Is your building too dry inside, thereby providing life sustaining low humidity levels for the Coronavirus or other viruses to live?
Researchers at Yale identify low Relative Humidity as a potential culprit in sustaining the life of the coronavirus indoors. Your heater maybe contributing to the occupants risk of seasonal viruses.
(RH) Relative Humidity is the amount of water vapor present in the air expressed as a percentage of the amount needed for saturation at the same temperature. If both of the rooms are at the same temperature as shown in the image below, one is approaching a very low RH, and the other is in the sweet spot at 50% Relative Humidity according to Yale scientist.
Relative Humidity at the same Temperature
Where do Yale scientist say the sweet spot is for maintaining RH levels in indoor environments?
The Yale researchers determined that mice were capable of clearing an inhaled virus and responding with a robust immune system when they were kept at 50% relative humidity.
The mice love 50% Relative Humidity and basically reject the virus when kept in this environment. Below is a psychrometric chart showing the relative humidity curves and the sweet spot between 40 & 60% RH.
Yale Research RH Sweet Spot
Why do we care about how mice respond, when we’re humans. But wait, there’s more, according to the National Human Genome Research Institute, “Overall, mice and humans share virtually the same set of genes. Almost every gene found in one species so far has been found in a closely related form in the other. Of the approximately 4,000 genes that have been studied, less than 10 are found in one species but not in the other.” This is why researcher use mice for many of their experiments.
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It may not be practical to keep your facility at 50% RH to slow the spread of viruses due to the heavy energy penalty and cost due to the type of facility, but you may want to consider trending where your relative humidity levels are throughout the year, especially in the winter when it is known to be low and in dangerous RH territory. The addition of a humidifier to your HVAC system will help increase the RH levels.
As shown in the chart below the Influenza Virus and the Human Coronavirus is more active in the winter months and early spring, when your more likely to use your heater and reduce the Relative Humidity in the indoor environment.
According to the epidemiological studies in temperate regions, most of the respiratory viruses have seasonal oscillation of their outbreaks, a few are shown in the chart below.
Seasonality of Respiratory Virus Infection in Temperate Regions
Effects on Relative Humidity due to Heating
As shown in the image below when air is heated the Relative Humidity is reduced. This is because sensible heating (horizontal pink line) strikes across the relative humidity lines on the psychometric chart. The example shows air at 60% RH being heated to 70 F & 30% RH. (Relative Humidity goes from 60% RH to 30% RH due to Heating).
As air increases in temperature so does its capacity to hold moisture but heating only provides sensible heat (adds no moisture), so the corresponding relative humidity drops, creating much drier air in relationship to its temperature.
The Effect Heating has on Relative Humidity
The Yale researchers indicate that when cold outdoor air is heated the relative humidity drops to about 20% RH. “This comparatively moisture-free air provides a clear path for airborne viral particles of viruses such as COVID-19”
Anything below 20% relative humidity and people begin to complain of dryness of the eyes, nose, mouth, skin and irritation of mucous membranes. Also, the rate of respiratory illnesses increases, and as the Yale scientist found in their research, the path for viruses is cleared for easier infection.
The chart below from the Yale research shows that the stability of the Respiratory Virus is at its lowest when the Relative Humidity is between 40 to 60% RH. The question to ask your HVAC technician or those responsible for your HVAC system, “what is the Relative Humidity level during the winter months?”.
Virus Stability and Relative Humidity
ASHRAE 55-2017
ASHRAE standard 55 provides a range of temperatures that are ideal for comfort but notes that there are many factors that go into the results for anyone individual. The environmental and personal factors influencing comfort include type of clothing (clothing insulation), metabolic rate, air temperature, air velocity, radiant temperature and our favorite, Relative Humidity.
As an owner or operator of a facility, whether that be commercial or residential, you’ll most likely only have control over the environmental factors, which includes relative humidity. It’s not like you can just shutoff the Heating system to help with the RH levels.
Summary
Relative Humidity matters according to the Yale scientist, so it should probably matter to us, unless a contradictory research reveals otherwise. Whether at home or at work, your HVAC design should take into consideration relative humidity. By adding a humidifier to provide the minimum level of moisture in the air to maintain the recommended relative humidity, you provide an additional layer of protection from air borne viruses, including COVID-19 according to the Yale scientist. Remember though that the recommended range is 40 to 60% RH.
If you have small children at home you might consider buying a small room humidifier for their bedroom for the heating season, just in case this research has merit. Better safe than sorry.
Remember that this isn’t a substitute for social distancing, washing hands, wearing a mask and the latest recommendations from the CDC, as they evolve with their understanding of how best to prevent exposure.
I’ve seen experienced technician install ACR refrigerant tubing without the use of a nitrogen purge at the time of brazing a joint into a new VRF system. This should be of concern for the owner of the system and the installing contractor as the potential for future problems increases without a purge.
Why Purge your ACR Piping?
Why go through the hassle of dragging out bottles of nitrogen, and then hooking them up with hoses to the newly installed ACR tubing so as to force a small amount of nitrogen through the piping during the brazing process? Well according to the Copper Development Association, the need to provide a nitrogen purge is to avoid harmful oxidation to the interior of the tubing during brazing which can lead to possible failure or contamination of the system. Reduction of these oxides reduces the chances of system contamination.
Most copper tubing manufactures will refer to this association for the proper installation of their ACR tubing.
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VRF equipment manufactures will also state in their installation manuals that purging with nitrogen or other approved inert gases are required. See the insert from Daikin’s Installation Manual (23MB) for their Heat Recovery Outdoor Unit.
Quality Control
Make sure that you mandate that the installing contractor provide a nitrogen purge during the installation of any ACR refrigerant piping no matter the size of the installed VRF system or the size of the tubing.
There is a reason that ACR piping comes pre-charged with nitrogen, and that is to ensure that there isn’t any moisture in the piping that could contaminate the system. Make sure that your contractor is using clean and capped ACR tubing or line sets.
The manufactures of copper tubing will provide a process of cleaning, purging and pressurizing the tubing to assure a high level of tubing cleanliness to comply with ASTM B280. They will seal the ends of the tubing with plugs to maintain the cleanliness from the manufacturing plant to the project site.
Make sure that the ACR tubing being used for your projects has been protected with caps on the end of the tubing before installation and during the process of installation until the system is sealed tightly so as to prevent any moisture from entering the system. Any stored copper tubing should have the ends capped to prevent atmospheric contamination during storage.
Look to see if the tubing is marked as ACR/MED. This indicates that this is the correct ACR piping for your VRF system. Don’t accept standard copper type “L” piping that hasn’t been processed according to the cleanliness standards of ACR/MED tubing.
Oxidation – The Hidden Bully
Piping Oxidation – The Hidden Bully
It is in the best interest of everyone not to allow the Oxidation Bully to the party, because he’ll destroy the place, causing damage that will show up later. Keep the bully away by adding the purging process to all VRF ACR tubing installations.
References:
ASTM B75 Seamless Copper Tube
C12200 99.9% Pure Copper
ASTM B280 Seamless Copper Tube for Air Conditioning and Refrigeration
VRF Ventilation Sensible Heat Ratio and Latent Heat
Ventilation for VRF Systems
Ventilation (outside air) can create havoc on occupant comfort if your VRF system isn’t sized or capable of handling the latent (moisture) content of the outside air. We will cover what to look for in your VRF system and what type of spaces may create a problem for ventilation air. Step 1 is to determine the latent heat of the space by following the below procedure, but first we need to understand a few helpful ratios and standards.
Moisture riding with the outside air is brought into the building to meet ventilation requirements as referenced in ASHRAE Standard 62.1. This moisture can make it uncomfortable for the occupant if the VRF system is incapable of handling excessive amounts. VRF Manufactures indicate their indoor units sensible heat ratio (SHR) which indirectly notifies you of its latent heat capabilities.
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Sensible Heat Ratio
The Sensible Heat Ratio (SHR) compares the amount of sensible heat to total heat. For example if you had an Conditioner with 60,000 BTU’s of Total Heat and a SHR of 0.75, you would have 45,000 BTU of Sensible Heat Removal and 15,000 BTU’s of Latent Heat Removal (Moisture)
Sensible Heat = 45,000 BTU’s (75%) or 0.75 SHR
Latent Heat = 15,000 BTU’s (25%)
Total Heat = 60,000 BTU’s (100%)
Sensible heat is something that you can feel as it affects a change in temperature, while latent heat involves a change in state (Vapor to Liquid) in the air conditioning cycle.
VRF Ventilation Air and Latent Heat
Item #1 – Mixed Air Temperature. This is a combination of the Ventilation Air (Outside Air) and Return Air. AHRI Conditions for testing uses entering air conditions of 80° DB / 67° WB at the cooling coil. VRF manufactures will show various temperature ranges, such as 58° to 82° WB in their engineering manuals allowing you to see the performance at various conditions for each of their systems.
Item #2 – 43° F Saturation Temperature
Item #3 – Modulating Expansion Valve will vary the amount of refrigerant that reaches the cooling coil in order to meet the demand of the set point of the remote controller (item #6)
Item #4 – 115° F Condensing Temperature in heating
Item #5 – VRF Manufactures will have their SHR (Sensible Heat Ratio) in the range of 0.70 to 0.89, which equates to the VRF system be able to handle 70% to 89% sensible heat and the remainder of 30% to 11% of latent heat (Moisture)
Item #6 – Remote sensor
VRF Manufactures Sensible Heat Ratio
The VRF manufactures indicate the SHR (Sensible Heat Ratio), that portion of the cooling capacity that can handle the sensible load (Temperature Difference) compared to the total load. The difference between the total capacity and the sensible is the latent heat, which is the ability of the cooling coil to remove moisture.
With VRF Manufactures sensible heat ratio’s (SHR) ranging from 0.65 to 0.89 (65% to 89%), this means that the latent capacity is equivalent to a range from 0.11 to 0.35 (11% to 35%). This requires that you check the design conditions that affect the mixed air temperature at the entrance to the cooling coil on the indoor unit. The higher the SHR, the greater the discharge air temperature will be.
You can see in the chart below from one of the VRF Manufactures that the Sensible Heat Ratio (D) decreases as the indoor WB (Wet bulb Temperature) increases. Instead of showing the SHR, this VRF Manufacture choose to list SHC (Sensible Heat Capacity) in BTU’s. Item (C) below shows a SHC of 50.8 which is indicated in thousands, so this stands for 50,800 BTU, while item (B) TC (Total Capacity) equals 56,900 BTU. To figure the Sensible Heat Ratio from this chart, the process is the same just take the SHC/TC.
VRF Manufactures SHR (SHC/TC)
Depending on the Sensible Heat Ratio (SHR) of the VRF units you are using and the Mixed Air Temperature (return and outside air), you may need another method than the VRF indoor unit to remove the excess moisture brought in by the outside air for ventilation requirements. You need to make sure that the mixed air temperature is with the range specified by the VRF manufacture; otherwise the capacity will be diminished.
Below is another VRF manufactures 2-Ton Ducted High Static Indoor Unit. As the indoor air temperature increases the Sensible Heat Ratio decreases, while the Latent Heat capacity increases. Increasing latent capacity comes at a sacrifice to an increase in the indoor temperature. This VRF manufactures 2-Ton ducted indoor unit at AHRI Standard 1230 conditions is rated at 24,000 BTUH at an indoor Entering Air Temperature of 80° F DB / 67°F WB based on an outside air temperature of 95°F DB/ 75°F WB
18,480 BTUH Sensible / 24,000 BTUH Total = 77% Sensible (23% or 5,520 BTUH Latent)
VRF System Chart based on AHRI Conditions
High Occupant Spaces and VRF
The higher the occupant load of the space, the more ventilation air required to meet ASHRAE standard 62.1 or if you live in California, then you would need to meet Title 24 of the energy code.
High density occupant spaces can put a latent burden on your VRF system. Depending on the SHR of the VRF unit as shown above in the example VRF chart there are limits to how much moisture or latent heat a VRF system can handle. According to ASHRAE standard 62.1 there is a requirement to bring in the minimum amount of ventilation (outside air) for each occupant of a space. The more occupants, the more outside air and its constituents of sensible and latent heat.
ASHRAE 62.1
The above Table 6-1 is a replication of the ASHRAE Standard 62.1. To understand how engineers determine how many occupants are required per space type there are various sources that can be used based on the local code authority, but for this simple example we’ll use the above table.
Occupancy Category defines the space type that is under consideration for determining the ventilation requirements. In column #1 above we have listed just a few of the hundreds of occupancy categories listed in ASHRAE’s table 6-1
Occupancy Density (Column #4) defines how many people are to be considered to occupy the space for every 1,000 Ft2 or people per every 100 M2. If you have a 500 FT2 office space, then the following quantity of people would be required according to the calculation as such; 600 Ft2 / (5 people/ 1,000 Ft2) = 3 People
Occupancy Density (# of People / 1,000 FT2)
People Outdoor Air Rate (Column #2) defines how much CFM (Cubic Feet per Minute) that must be provided for every person determined by the occupant density requirements.
Area Outdoor Air Rate (Column #3) defines the additional CFM/Ft2 required for the off-gassing and other contaminants generated by the space and its furnishings.
Example Ventilation Requirement
500 Ft2 Breakroom
Step 1 – Figure total Occupant Density (500 Ft2 / (50 people / 1,000 Ft2) = 25 People
Step 2 – Multiple People by column #1 (CFM/Person) to get total CFM for Outdoor Air (25 People x 5 CFM/ Person) = 125 CFM
Step #3 – Figure the CFM required for column #3 (Area Outdoor Rate). 500 Ft2 x 0.12 CFM / Ft2 = 60 CFM
Step #4 – Add the two values together (125 CFM + 60 CFM = 185 CFM)
How do you get from CFM of ventilation air to latent heat in BTUH. The simple answer is by using the following calculation, which would require a psychometric chart or computer program.
2019 Building Energy Efficiency Standards Title-24
If you live in California, then you will go by section 120.1 of Title 24, which provides for the requirements on ventilation. Section 120.1(b) is for High-rise residential Buildings, but we will cover section 120.1(c)3 which covers Nonresidential and Hotel/Motel Buildings using a mechanical system, as opposed to natural ventilation.
The system needs to be designed to meet one of the two following methods whichever provides the larger outdoor flow rate (CFM).
Method 1
(Equation 120.1-F) Vz = Ra x Az
Where:
Ra = Outdoor airflow rate required per unit area as determined from Table 120.1-A
Az = Zone floor area is the net occupiable floor area of the ventilation zone in square feet.
Title 24 California Energy Code on Ventilation
Method 1 Example (Breakroom Space)
Ventilation CFM = Air Rate (from table 120.1-A) x Square Footage of Breakroom (1,000 Ft2)
Ventilation CFM = 0.50 x 1,000 = 500 CFM
Method 2
This method uses a calculation based on a fixed amount of occupants or fixed seating. This can be based on the engineers design occupant quantity or fixed seating quantity. California Building Code table 1004.1.2 “Maximum Floor Area Allowances per Occupant,” indicates occupancy parameters based on room types.
(Equation 120.1-F) Vz = Rp x Pz
Where:
Rp = 15 cubic feet per minute of outdoor airflow per person
Az = The expected number of occupants. The expected number of occupants shall be the expected number specified by the building designer. For spaces with fixed seating, the expected number of occupants shall be determined in accordance with the California Building Code.
Converting Latent Heat CFM to BTUH
Latent Heat BTUH = CFM x 0.68 x Delta-Grains (Outdoor Grains – Indoor Grains) See our YouTube video explaining this calculation using a psychometric chart.
Other Latent Heat Loads
In addition to the ventilation air (outside air) adding latent heat (moisture) to the space, there are other contributing factors. People give off sensible and latent heat. People give off about 140 BTUH when they are seated at rest. Equipment and infiltration can also add moisture to the space.
Ventilation – People – Equipment – Infiltration
So what do you do if your VRF system can’t manage all the latent heat coming into the system from ventilation air, people, equipment and infiltration? There are several options that we have already covered in other articles that you can find links to within this article.
The solution is to provide another means of removing the latent heat (Moisture) and not rely on the cooling coil of the VRF system.
DOAS – Dedicated Outside Air Systems
One of the options available for handling the excessive moisture that the VRF system is incapable of removing is to use a DOAS system. The DOAS system can handle the additional moisture that the VRF system isn’t size to remove, plus it provides additional static pressure and airflow. See this article on DOAS systems or VRF Ventilation Alternate Systems
Summary
ASHRAE Standard 62.1, “Ventilation for Acceptable Indoor Air Quality,” under the mechanical ventilation method needs to be carefully reviewed when designing a VRF system to ensure that there is sufficient capacity to handle the moisture brought into the space for ventilation (Outside Air). Ducted VRF systems have limited capacity to handle moisture. Check the SHR (Sensible Heat Ratio) of the indoor VRF unit and the fans static pressure rating to determine if they are sufficient to meet the requirements of the space.
Identify the space type where the VRF system is being proposed and calculate the latent heat from the ventilation, infiltration, occupants and any equipment giving off moisture. Select a VRF System that can handle the latent load if possible, if not, then select an alternate method of conditioning the ventilation air before it hits the VRF cooling coil.
This formula will show you how to calculate the total heat transfer from a cooling coil. The calculation for this is as follows;
BTUH(t) = CFM x 4.5 x [Et(h) – Lt(h)]
Cooling Coil Total Heat Transfer
To calculate the Total BTUH you will need to know how much CFM is traveling over the coil, and what the entering and leaving total enthalpy.
BTUH(t) = Total BTU per Hour
Et(h) = Entering Total Heat (BTU/LB of Dry Air)
Lt(h) = Leaving Total Heat (BTU/LB of Dry Air)
What we need to do to come up with the values for our calculation, is to take some field measurements to come up with the CFM and the temperature of the entering and leaving conditions.
Entering Conditions
For our example we will assume that the field measurements determined that there is 2,000 CFM of air passing over the cooling coil at 76 DB (Dry Bulb) and 64WB (Wet Bulb).
Leaving Conditions
The next step is to measure the leaving air conditions. We measure that the same 2,000 CFM entering the coil is also leaving the cooling coil, but at a reduced temperature of 56 DB and 53 WB.
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Psychrometric Chart
These conditions are easily plotted on a psychrometric chart. Horizontally along the bottom of the chart is where you will find the scale for dry bulb temperature. We have shown the entering condition with a vertical red line at the 76 degree dry bulb temperature line.
Then we draw a red line diagonally at the 64 degree wet bulb temperature line. The wet bulb temperature scale runs on a curve along the left side of the chart. As a side note, the point at where they intersect will indicate the relative humidity level and other info.
Psychrometric Chart of Entering Conditions
With the entering temperature plotted on the psychrometric chart as shown below, we can see that the wet bulb temperature line when extended further up and to the left, will hit the “Total Heat Enthalpy” scale. At that point you can read the value as 29.31 Btu/lb of dry air.
Entering Total Heat (29.31 BTU/LB)
By doing the same thing for the leaving conditions we can derive at the “Total Heat Enthalpy” for the leaving air. As indicated below by the blue lines, this value equals 22.02 Btu/Lb.
Leaving Total Heat (22.02 BTU/LB)
Now that you have plotted both the entering and leaving conditions on the psychrometric chart, you will be able to calculate the difference in Enthalpy between the two, which is required for our calculation.
Formula for Total Heat at Cooling Coil
Using our example, we can now plug into the total heat transfer equation the values we have determined from our measurements and from plotting those values on the psychrometric chart.
Total Heat Transfer Equation for Cooling Coils
We have calculated the total heat transfer as 65,610 BTUH
Wet Bulb to Enthalpy Chart
To make life easier, there are charts that will give you the Enthalpy values based on the wet bulb temperature. As shown below, we have highlight the entering and leaving wet bulb temperatures and their corresponding Enthalpy values, the same values that were derived from plotting the wet bulb temperatures on the psychrometric chart.
Having an HVAC VRF Estimating Spreadsheet that automates portions of your estimates saves you valuable time that you could use to make more sales. All aspects of the cost of furnishing and installing a VRF or HVAC system is contained in one spreadsheet made specifically for the HVAC industry.
Your VRF HVAC Estimating Spreadsheet needs to be able to handle rental equipment, general conditions, subcontractors, piping takeoffs, sheet metal, labor rate tables with crew mix capabilities, , and a bid summary. Each sheet in the estimating spreadsheet automatically calculates the values you enter, showing you a new total bid amount.
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VRF & HVAC Equipment
Enter the project equipment price and labor to rig into place. Compare supplier pricing easily side by side. The VRF HVAC Estimating Spreadsheet automatically selects the lowest bidder but lets you override that decision.
HVAC Equipment Equipment Cost and Labor Sheet
Labor Rate & Crew Mix Table
Choose your crew mix based on the level of experience and the different pay scales based on each project. Pick any combination and quantity of tradesman based on the requirements of the project. There is a separate crew labor rate for HVAC Piping Shop & Field and Sheet Metal Shop & Field.
Labor Rates and Crew Size
VRF Piping Material & Labor
The piping tab on theVRF estimating spreadsheet allows you to enter ACR piping material and labor unit values for pipe sizes 1/8” to 3-1/8” along with a discount multiplier. Also included are 50 and 100 foot rolls of copper, fittings and empty tables for any items you want to add.
ACR Piping Labor and Material Cost
General Conditions
Do you need a jobsite trailer or onsite management? Enter the quantity and level of the staff required to run the project, whether one person or dozens. Set the quantity and duration of each general condition.
General Conditions Tab in the VRF Wizard Estimating Spreadsheet
Subcontractors
HVAC contractors often subcontract out for Air & Water Balance, Sheet Metal & Piping Insulation, Water Treatment, Building Automation, Excavation and other specialty trades that they don’t self-perform. This spreadsheet was made especially for the HVAC contractor and the most often used subcontractors.
Piping & Sheet Metal Material & Labor Sheet
Having a estimating spreadsheet with your pipe & fitting prices already entered and saved for use on the next estimate saves time and money. Just enter the quantity required and the cost and labor is automatically generated based on your unit values.
VRF Piping Material and Labor Summary Sheet
Rentals
For those HVAC air conditioning projects that require a crane, fork lift, scissor lift or any other equipment that you don’t own but will be required on the project. Having a spreadsheet that maintains a list of the most common equipment you normally rent along with their rental rate will save you time and money while avoiding having to call for pricing on every job.
Rental Equipment Pricing Sheet
Engineering
If you do your own design then you should have a sheet of each of the personnel responsible for spending time on the engineering task. If you’re doing design/build work, but don’t do the engineering yourself, but hire a third party, then you should add some engineering review time. It’s your responsibility to manage your third-party engineer to make sure they design within your cost parameters.
Engineering Cost Sheet
Estimate Summary
All of your estimates are summarized on the last tab of the VRF HVAC Estimating spreadsheet for easy review. You can quickly scan each of the categories to see where all the project cost has shown up. There is the labor and material summary for HVAC Piping & Sheet Metal another section for subcontractors, general conditions, rentals, etc.
Parameters
How much does this project cost per square foot or per ton? How many CFM or BTU’s per square foot did the engineer figure? What is the cost per ton for this project? With the easy parameter calculator contained on the summary page, you can keep historical records of the project you bid.
Engineering and Cost Parameters
Estimating Spreadsheet
Having an HVAC Estimating Spreadsheet made exclusively for the HVAC industry without costing a fortune is a money saving opportunity. This helps prevent having to make a major purchase for an estimating software program that offers a spreadsheet as a package deal, and will save of thousands of dollars.
HVAC Piping & Sheet Metal Estimating Programs
HVAC Piping & Sheet Metal Estimating programs can cost anywhere from $5,000 to over $10,000 for the industry leader. These expensive programs will pay for themselves over time if you are bidding lots of large plan and specification projects requiring a lot of material takeoffs. These programs are great for crunching large amounts of data quickly and efficiently saving you time and money. They can hold over a hundred thousand prices for pipe, valves and fittings, along with calculating sheet metal cost.
VRF HVAC Estimating Spreadsheet Summary
The VRF Wizard spreadsheet is used to gather all the information for estimating a project, putting it into a format where you can make quick adjustments and decisions while the spreadsheet gives you an immediate update on the price.
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Find comparison on VRF System Central Controllers for all major manufactures. Daikin, Carrier, Toshiba, Panasonic, Mitsubishi, Trane, York, LG, Fujitsu, Lennox,
The following is a look at Touch Screen VRF Central Controllers that are available from the various VRF system manufactures. There are various other control schemes that can be employed to accomplish increased levels of monitoring and control at additional cost. These additional levels of control would include BACnet and similar protocols, in addition to the monitoring of the facilities non-VRF systems, such as lighting, boilers, security and other HVAC equipment. An additional BMS module would be required in most cases in order to connect the Touch Screen Controller to a BMS system.
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Maximum Indoor Units on Main Controller
The size of your facility and the quantity of indoor units that you need to monitor from your VRF controller is dictated by the maximum allowable set by each VRF manufacture. Some VRF manufactures have adapters that allow you to expand this maximum even further; other VRF manufactures would require you to purchase another main controller.
VRF Central Controller – Maximumm Indoor Units
Multiple Indoor units can be operated by one controller and identified as a group within the central controller. Groups allow for easily scheduling or making operational changes to indoor units that belong to the same tenant, zone or other parameter. VRF central controllers will limit the quantity of groups available.
VRF Controller Display Size
If you’re going to be viewing floor plans on the Display then you will probably want a larger screen size.
VRF Main Controller Display Size Comparison
Prohibit Remote Controllers
This feature allows the prohibiting of certain functions or adjustments at the tenant level using the remote controller. Certain control settings can be prohibited from being adjusted such as temperature settings, fan speed, on/off, scheduling and others.
You can setup restricted adjustments and then disable/enable the restricted group of settings by changing the accessibility at the central controller. Some Indoor units can be locked out while others are freely adjustable by the tenant. Restrict a portion of the remote controls functionality or all of it.
Daikin VRV System Controller
Daikin VRV System Controller
The Daikin VRV Touch Screen Central Controller (ITM Intelligent Touch Manager) comes with the following features:
Choice of 3 different screen savers.
Area and Group configuration
Area contains one (1) or more Area(s) or Group(s)
A Group may be an indoor unit, Di, Dio point that has a DIII-NET address
The Controller displays On/Off, Operation Mode, Setpoint, Space Temperature, Louver Position, Fan Speed for each Area or Group.
Displays date and day of the week along with the time of day
Adjust for daylight savings time (DST) automatically.
System status icons displays On/Off (color coded), Malfunction/Error (color coded), Forced Stop, Setback, Filter, Maintenance, and Screen Lock.
Display of temperature setpoint and room temperature information configurable for Fahrenheit or Celsius
Error status displayed in the event of system abnormality/error with one of three color coded icons placed over the indoor unit icon or lower task bar.
Error history stores up to 500,000 errors/abnormality events
Floor plan layout
Capable of displaying site floor plan as the background for visual navigation. Indoor unit, DIII-Net Di and Dio, and External Di, DO, and Ai icons with operational status can be placed on the floor layout
The ability to track the electricity usage by each tenant provides for a convenient means of billing. Each tenant in a building may have hours of usage that differs from their neighbor. With tenant metering you can fairly charge each tenant according to the amount of electricity or for the time their air conditioners are running.
Scheduling
VRF Central Controllers allow for the operational scheduling of the various zones programmed into the system. It’s imperative that you set up your zones according to usage, separating out rooms that run 24 hours a day or run on the weekend. This will allow certain zones to function after hours while the rest will shutoff to ensure energy efficient operation of the facility. A good way to waste money is to have your HVAC system running when the space is unoccupied.
Each VRF central controller will allow a limited amount of schedules that can be programmed into the system. Schedules can be given a name that corresponds to particular events or daily fluctuations in operating hours.
The quantity of events that are capable of being set for each schedule created is limited by the program. Setting events lets you control what happens at what time according to your programmed schedule. Each VRF manufactures central controller allows you to manipulate various set points and conditions based on your schedule, such as fan speed, setpoint shift, Temp setback points, pre-cool/pre-heat settings, Prohibit Changes, timer extensions, etc …
Features to look for:
Administrative Control
Graphical representation of schedule
Ability to exclude dates, such as holidays or weekends.
The LG Smart 5 VRF Central Controller comes with a wall mounting plate, manual and a SD Card. The SD card is used for data backup and recovery. The LG Smart 5 features a UX-compatible platform that works with a PC, smartphone or tablet. The LG Smart 5 contains the following:
10.2” LCD Touch Screen (C-Type Touch Panel)
Dual Core CPU
2 GB of Memory
16 GB of storage
Mono speakers
2-Port RS-485
SD Card (data backup & recovery)
Mini USB (for debugging software), Micro USB (for service)
VRF Central Controllers vary on their ability to control settings and functions. You can control one component or make global changes to all units using the VRF central controller. A password can be used to lock or allow certain changes to the settings based on what you would like the tenant to be able to change.
Features to look for:
Temperature settings
Temperature range restrictions (limit High & Low Settings)
Fan speed (typical high, medium & low)
Louver control (adjust direction of airflow)
Mode (Operational control of an attached component)(heating or cooling only)
Schedule
Controller use restrictions (Permit or Prohibit use of certain settings or functions)
On/Off of attached components
Language
Passwords (screen can be locked requiring a password)
Date and time (12 hour or 24 hour display)
Screen display brightness and backlight timeout functionality
Ability to move a device from one zone to another
Error codes and history of errors
Ability to import and display floor plans
Error detection notification via email
Interlock with non-VRF input devices (Motion sensor, CO2 sensor, Door entry key)
Emergency stop
Administrators and Users (maximum quantity of admins or users)
Control Wiring
VRF Central Controllers are wired to each component in the system in a daisy chain fashion. This is very efficient method of wiring that allows each component a pathway for the communication wiring to the central controller. If you need to expand the quantity above the allowable limits for the system than you would need to run separate wiring to each of the added adapters that help increase the capacity of the control system.
RS485 cabling is the most commonly used connective wiring as it allows for multiple devices to be connected together and allows for longer runs of cabling than the previous RS-232.
The capability to connect to a BACnet system or some other protocol should be available, sometimes as an add-on component.
Data Backup
There are various methods that the VRF manufactures use to allow data to be backed up and stored in case of power or system failure. Having a backup will save you hours of programming if such a failure occurs and you need to restore your settings. Backup can come in the way of storing the data on a hard drive, thumb drive, the cloud or on some form of Memory card. This may also be the method that the VRF manufacture using to update the system software.
Zone/Area Control
A zone is created by grouping various indoor units together under a common control setting scheme. Combining a group of indoor units that have similar thermal experiences and scheduling requirements will help save on individual programming. You can provide a name for each zone that you create, allowing for quicker recognition of various areas of your facility under control.
You can group indoor units according to the Outdoor Unit that feeds them in addition to the floor that the indoor unit resides on. See example below.
3rd Floor – ODU-1 – Indoor Unit (Room 345)
Floor Plan Display
A unique feature of the central controller is its ability to import and display floor plans. Having the ability to view the floor plan on the controllers LCD display with the indoor units displayed in the appropriate locations, allows for a quick graphical representation of the overall system layout. The indoor units are represented with icons that are interactive, allowing you to make adjustments to the settings for each unit with a quick touch of the screen. The auto detection feature of the VRF Central Controller will populate the system with individual icons for each indoor unit.
The VRF Central Controllers allow for email notification when an error occurs in the system. This allows for rapid response to get the error corrected and the system repaired if needed. The email notification allows for various alarms or errors to be directed to different email addresses. If there is an error with the Outdoor Unit, maybe you want two emails sent, one to the building engineer and another to the contractor that services the system. This would allow the contractor to be in route to fix the issue much faster. Error logs can show the history of alarms and what part of the system went into alarm.
Internet/Web Access
Some of the VRF Central Controllers can be viewed over the internet using the appropriate additional hardware in some cases, while others require only an IP address at the site for connection to the controller. Web access allows you to operate and make adjustments to the VRF central controller from a PC or MAC instead of having to be present at the touch screen.
Administrator and Users
The VRF Central Controller usually has two levels of access, one for administrators and another for general users. There is a maximum amount of general users that the system will allow, in addition there is a limit of how many of those users can access the system at the same time.
The administrator can access multiple building sites from an offsite location via the internet. For owners or property management companies that have multiple properties this makes oversight much easier.
Commissioning
With a VRF system, commissioning is critical to the proper operation of the system. Using a certified trained technician will improve your chances of having the system run as designed. Commissioning will ensure that the initial settings and calibrations are correct and everything is functioning as intended.
Most of the VRF central controls have a self-discovery feature that automatically recognizes any component that is connected properly to the system. This feature will automatically detect any indoor fan coil, outdoor unit or heat recovery box that is wired correctly to the central controller and powered electrically. You will need to run electrical power to energize the VRF central controller. Most VRF central controllers run on 120-240V, 50/60 Hz power
Summary
Having a VRF central controller makes sense if you have a lot of indoor units that you would like to control from a central location or remotely. Having the ability to see what is happening at each indoor unit and having the ability to adjust or lockout the adjustment of any of the settings provides better management of the energy consumption and usage of the air conditioning and heating system. Support this blog by using the following links for any Amazon purchases.
How do you increase individual control without adding additional indoor units? Daikin has a Zoning Kit that allows you to increase the amount of zones that are controlled by their own thermostat while using the same indoor fan coil unit. Using the Daikin Zoning Kit eliminates the need for multiple indoor units to create individual zones, which should save you money.
Depending on the size and type of your indoor fan coil, you can add up to six (6) zones. The largest single indoor fan coil that has the ability to add this zoning kit has a capacity of 54,000 Btuh, which can be split into 6 zones or as few as 2 with air flow rates (CFM) as shown in the chart below.
Daikin Zoning Kit CFM Range
Using the Daikin DZK Zoning Kit gives you the ability to have better control over individual spaces. You can have one of the 6 zones feed one space or multiple spaces depending on the cooling requirements of the space. You can combine two zone dampers together to create a bigger zone, or have one zone serve multiple supply air grilles.
Daikin Zoning Kit (DZK) 4-Zones
The Daikin DZK Zoning Kit currently works with their FXMQ_P, FXSQ_TA, FBQ_P and the FDMQ series indoor units.
The Daikin Zoning Kit is relatively light, weighing 23 lbs. at the largest size, while only requiring 10.44” in height. It will require either 110 or 230 volts of AC power.
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Daikin Controls and BACnet
The Daikin zoning kit integrates seamlessly with the indoor unit fan coil controls. You have the choice of a wired or wireless thermostat; this is in addition to the indoor fan coil unit’s navigation remote controller. The thermostats control the individual zone dampers allowing for better comfort control for each space.
BACnet
The Daikin zoning kit has the option of adding the DZK BACnet interface module to work with any BACnet IP compatible Building Management system, including the iTM BACnet Client option. This gives you 14 system-level points and 12 zone-level points for better monitoring and control of each individual zone. It allows control & monitoring of the following variables:
Indoor unit status
Fan status and fan speed
Auxiliary heat stages status
Global ventilation status
Operation mode
On/Off for each zone
Set point setting for cooling & heating in each zone
Room temperature in each zone
You can get the above using Daikin’s iTM controller in addition to the following:
Local fan activated/deactivated for each zone
Auto (scheduling) activated/deactivated
Unoccupied mode status
Vacation mode activated/deactivated
Opening damper status for each zone
Indoor unit and DZK errors
The wireless controllers can be up to 164 feet line of sight distance to the control box. You can connect up to 6 wired controllers to the control box. The wired controllers are sexier with its color display versus the flat single color wireless controllers.
Alarming is also available which allows the unit to be shut down and the dampers closed. You could use a refrigerant leak detector that could shut the unit down upon a refrigerant leak, or a smoke detector.
Various Zone Configurations
You can arrange the zones in various combinations from single zones to a group of five (5) zones out of six on Daikin’s 6-zone box. Below are the options for Daikin’s 4-Zone Box Kit.
Daikin Zoning Kit Optional Layouts using a 4-Zone Box
Daikin Zoning Kit Air Balancing
One minor flaw in the design of the zone box kit is that on several of the zone kits, specifically the two smallest kits, model DZK030E4 & 5, the indoor unit supply air discharge doesn’t line up perfectly with the zone box. This causes the dampers in the middle of the zone box to receive more air flow than zone dampers on the outsides of the box.
You need to take this into consideration when balancing the system, or if you’re not going to use all of the zone ports, than blank-off zone #1, the outer most zones with the least amount of air flow.
Daikin VRV Fan Coil Zoning Kit
Fresh Air – Ventilation
Most codes require some form of minimum ventilation for occupied spaces. The Daikin indoor unit sets a range for the inlet temperature of the mixed air (Outside Air & Return Air) entering the unit. This is to avoid burdening the indoor unit with additional cooling and heating loads above a certain range. If the entering air is going to exceed the allowable range, than the outside air needs to be pretreated.
The minimum supply air for the Daikin Zone Kit can’t be set below the code minimum outside air requirement. This can be accomplished by setting the Daikin Zone dampers to a minimum setting that corresponds to the code required minimum ventilation CFM.
According to ASHRAE 62.1 2013 any ventilation system wherein one or more air handlers supply a mixture of outdoor air and recirculated air to more than one ventilation zone, the outdoor air intake flow (Vot) shall be determined in accordance with sections 6.2.5.1 through 6.2.5.4
To understand how to calculate the required ventilation for a Multiple-Zone Recirculating System see ASHRAE 62.1 or Daikins Zoning Kit Application Guide.
Summary
The Daikin Zoning Kit (DZK) is a great option to increase individual zone control and comfort without having to add extra indoor unit fan coils.
Daikin now has available a Dual Fuel, 3-phase variable refrigerant flow system. Daikin made it adaptable to the North American market with its ability to integrate with the ubiquitous gas furnace. For heating Daikin gives you the choice of using electricity (heat pump) or a gas furnace. This allows a customer to switch between electric or gas heating depending on the cost of utilities.
The Daikin VRV IV X connects with their 80%, 96% and 97% AFUE gas furnaces (available from 60,000 Btu up to 120,000 Btu) using the CXTQ coils (Available In 2, 3, 4 & 5 Tons). The Daikin system allows you to connect multiple gas furnaces to a single outdoor unit. Switch from heat pump (electric) to gas heat with customizable changeover temperatures.
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Phased Installation
The Daikin IV X was designed with the phasing of projects in mind. The capability to add indoor and outdoor units as the project gets built-out provides flexibility for multi-tenant phased projects. Also, initial capital investments can be reduced until future tenant spaces are leased and additional capacity is required. Starting with one outdoor unit you can expand to a dual system than to a triple outdoor module configuration as indoor units are added to serve the required tenant buildout.
Variable Refrigerant Temperature
Using the Variable Refrigerant TEMPERATURE system design you benefit with increased annual energy efficiency and comfort. This is done by optimizing the compressor speed using automated adjustments to the temperature difference of the evaporator temperature (in cooling) and condensing temperature (in heating) with the condensing temperature and the evaporation temperature, respectively. The compressor works less, so you save more energy.
In ECO mode the Daikin IV X is optimized for energy efficiency and with each progressively faster mode of operation the temperature reaction time increases to keep the room set-point temperature.
The outdoor units come in sizes from 6 tons (1 module) up to 38 tons (3 modules) with the use of various indoor unit types. The indoor units come in capacities from 1/2 ton up to 8 tons.
ASHRAE looked at three types of flame-free mechanical joints that are used in refrigeration and air-conditioning systems, which included; Press/crimp fittings, compression fittings, and flare fittings. They also included a brazed joint as a bench mark against the time and leak rate of the various mechanical joints.
100 Mechanical Joints Tested
The experiment involved using experienced and inexperienced refrigeration technicians that would assemble 100 of each type of joint. They then recorded how many joints had failed and what the average time it took to assemble a joint for each joint type.
Testing of the Mechanical Joints
Next they tested the durability of the fitting assemblies to see if they would hold up through pressure-temperature cycling, freeze-thaw cycling, and vibration testing. They then measured the refrigerant leakage rate of each mechanical joint assembly.
Conditions of Test
100 Fittings of each Joint type was tested. (100 Press-fit, 100 Compression, 100 Flared)
Used both experienced & inexperienced technicians
Two different sizes for each fitting type (3/8” & 1-1/8” Press-fit), (3/8” & 3/4” Compression & Flared)
Assembled under Normal Conditions & Difficult Conditions (Elevated & Confined Spaces)
Recorded time to assemble.
Tested fitting assembly with Pressure-Temperature cycling, Freezing-Thawing or Vibration.
Recorded leakage of any fitting assembly
Leakage Rate Test Results
The biggest winner by far was the Press-fit fitting assembly. If there was any doubt about using a mechanical press-fit fitting such as Parkers Zoomlock versus a brazed fitting, this study should relieve your fears. With an amazing 99% success rate, and with only 1 leak by an inexperienced technician, the Press-Fit fitting assembly is by far the most reliable fitting in this study. The one press-fit leak was due to the lack of inserting the tubing fully into the fitting, and was not due to fitting failure.
The fitting assemblies were subjected to Pressure-Temperature Cycling, Freeze-Thaw Cycling & Vibration Testing. Again the Press-fit fitting assembly dominated the results with NO failures out of the 100 fittings test. The Press-fit fitting scored a success rate of 100 out of 100.
Harshness Failure Rates of Mechanical Pipe Joints
Summary
The test results of ASHRAE’s study on Mechanical Piping Joints showed that the press-fit fittings took less time and had fewer leaks and was more durable than all the fitting assemblies including, compression, flared fitting and brazed. The use of experienced technicians will save you from 20 to 105% over inexperienced technicians, so it’s important to have technicians that are well trained in order to save time and avoid costly leaks. The flared fittings took the longest time to assembly and had the greatest amount of leaks.
The press-fit fitting dominated the ASHRAE study!
Checkout Mechanical Pipe Joints in these various articles;
