Horizon213
Member
- Location
- Atlanta, GA
Sounds good to me David, I was just wondering, great discussion, I enjoyed it guys! Have a great day!
Service calculation load for 8 Air handlers . 480 volt 3ph. Name plate pic. attached
- Thread starter Horizon213
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Sounds good to me David, I was just wondering, great discussion, I enjoyed it guys! Have a great day!
- Location
- Connecticut
- Occupation
- Engineer
The label in the photo says "heat pump" so the compressor will run in heating mode as well.
- Location
- Placerville, CA, USA
- Occupation
- Retired PV System Designer
For any given installation of heat pump with auxiliary resistance heating, the decision on whether and when to run the compressor and heat strips at the same time is a design question.
You cannot just assume either that they will be used concurrently or that they will not.
StarCat
Industrial Engineering Tech
- Location
- Moab, UT USA
- Occupation
- Imdustrial Engineering Technician - HVACR Electrical and Mechanical Systems
Modular System
Modular System
View attachment 10041 [/QUOTE]
This is a very odd nameplate for " just " an AHU, as it shows compressor and charge DATA. Since it shows ampacity of OUTDOOR fan, it appears to be a remote air cooled unit. If you open it up I would expect to see a compressor inside. Its a type of package unit by the label.
I have seen and worked on similar ones made by Carrier and others.
It calls for 15 AMP protection with no heat pack.
30 AMP protection for 10KW of heat.
35 AMP protection for 15KW of heat.
These ampacities appear to cover everything INSIDE that cabinet.
AS thus, COMPRESSOR, BLOWER, HEAT PACK, etc.
By Model number standard convention its a 3 Ton compressor. [36000 BTU]
Its badly labeled.
I would call the OEM and ask to speak with Engineering.
Modular System
View attachment 10041 [/QUOTE]
This is a very odd nameplate for " just " an AHU, as it shows compressor and charge DATA. Since it shows ampacity of OUTDOOR fan, it appears to be a remote air cooled unit. If you open it up I would expect to see a compressor inside. Its a type of package unit by the label.
I have seen and worked on similar ones made by Carrier and others.
It calls for 15 AMP protection with no heat pack.
30 AMP protection for 10KW of heat.
35 AMP protection for 15KW of heat.
These ampacities appear to cover everything INSIDE that cabinet.
AS thus, COMPRESSOR, BLOWER, HEAT PACK, etc.
By Model number standard convention its a 3 Ton compressor. [36000 BTU]
Its badly labeled.
I would call the OEM and ask to speak with Engineering.
StarCat
Industrial Engineering Tech
- Location
- Moab, UT USA
- Occupation
- Imdustrial Engineering Technician - HVACR Electrical and Mechanical Systems
Modern Heat Pumps
Modern Heat Pumps
This is correct, and sorry I may not have read the entire thread responses.
MOST "Electric " heat pumps, as in NOT " Dual Fuel " WILL run backup heat strips and compressor during defrost periods for sure. This is typical convention.
The compressor LOAD during Heating operation is notably less than when in AC-Cooling mode because the unit is performing refrigeration duty at this point. Most Heat Pumps use outdoor air sensors in conjunction with their control logic and in some cases the 1st stage of electric heat can run with the compressor to a certain design limit.
All the best
Modern Heat Pumps
For any given installation of heat pump with auxiliary resistance heating, the decision on whether and when to run the compressor and heat strips at the same time is a design question.
You cannot just assume either that they will be used concurrently or that they will not.
This is correct, and sorry I may not have read the entire thread responses.
MOST "Electric " heat pumps, as in NOT " Dual Fuel " WILL run backup heat strips and compressor during defrost periods for sure. This is typical convention.
The compressor LOAD during Heating operation is notably less than when in AC-Cooling mode because the unit is performing refrigeration duty at this point. Most Heat Pumps use outdoor air sensors in conjunction with their control logic and in some cases the 1st stage of electric heat can run with the compressor to a certain design limit.
All the best
kwired
Electron manager
- Location
- NE Nebraska
Maybe, GD kind of covered what I was going to say on this.
For any given installation of heat pump with auxiliary resistance heating, the decision on whether and when to run the compressor and heat strips at the same time is a design question.
You cannot just assume either that they will be used concurrently or that they will not.
True the compressor is often less loaded when in the heating mode, but it is because the lower temperature typically encountered on the "evaporator side" means less heat is being moved, which puts less load on the compressor. When in defrost mode and aux heat is running - it is in "cooling" mode and there is more heat being transferred to defrost the outdoor coils, but at the same time this cycle is usually pretty short in duration, and may or may not involve 100% of the resistance heat being energized either, so it is still somewhat a case by case situation of what the peak load may actually be during a defrost cycle.
- Location
- Connecticut
- Occupation
- Engineer
For any given installation of heat pump with auxiliary resistance heating, the decision on whether and when to run the compressor and heat strips at the same time is a design question.
You cannot just assume either that they will be used concurrently or that they will not.
An HVAC heat pump runs the refrigeration cycle in reverse to heat rather than cool. You cannot assume that the compressor will not be running when the unit is heating, as Shoe suggested with his question.
kwired
Electron manager
- Location
- NE Nebraska
The compressor is running while defrosting or else you will not bring any heat to the coil to defrost it - true it is temporarily in the "cooling mode" as well that is how it brings heat to the outside coil to defrost it. The question is whether the aux heat is activated during this process, some say it must be, but the amount of heat lost during the defrost cycle is not that significant that it is absolutely necessary either, and part of the idea of heat pumps is that it takes less energy cost to operate then the resistance heat, so why spend the extra on the resistance heat even for the defrost cycle that will not last for long anyway, all you are doing is taking that heat and pumping it outside to defrost the coil, why not use the existing inside air that was heated by the heat pump to gain the needed heat for the defrost?
- Location
- Placerville, CA, USA
- Occupation
- Retired PV System Designer
Well, having cold air coming out of the ducts, even for a short time, could annoy the customer.
If instead the room temperature just drops a bit for no apparent reason, it might be acceptable.
Tapatalk!
If instead the room temperature just drops a bit for no apparent reason, it might be acceptable.
Tapatalk!
- Location
- Connecticut
- Occupation
- Engineer
I'm not talking about defrosting, I'm talking about heating. In other words, using the compressor to heat the conditioned space rather than cool the conditioned space.
kwired
Electron manager
- Location
- NE Nebraska
Those customers better stick to gas heat then, as the temp at the register is not all that high for straight resistance heating or for a heat pump in most cases, some don't like it.
Whether or not the aux heat can run with the heat pump depends on the controls, many do and the aux heat is a second stage on the thermostat. Again as mentioned earlier a heat pump in heat mode typically is not loaded as much as it can be in cooling mode, though NEC doesn't really recognize this fact. My 3 ton geothermal never even comes close to RLA when heating. RLA is likely somewhere near 20A but I have never measured it drawing more then maybe 8 A in heating mode. Since the heat source is a constant temp I doubt it ever will draw more either unless something changes.
- Location
- Connecticut
- Occupation
- Engineer
The data on the nameplate for this unit indicates that the electric heat and the compressor run concurrently.
The specification data from their website tells you how much heating MBH you will get from the compressor in heating mode. Whether the compressor will draw less than RLA in heating mode isn't really relevant.
kwired
Electron manager
- Location
- NE Nebraska
Via making some assumptions from the MCA. But irregardless you must supply it with a conductor sized according to MCA, making any argument somewhat pointless for the branch circuit calculation, but the OP is trying to calculate service or feeders.
- Location
- Connecticut
- Occupation
- Engineer
kwired
Electron manager
- Location
- NE Nebraska
Not exactly what you were referring me there for but I was thinking someone commented on the 208/230 volt indoor blower being an error but wasn't finding it - thanks. It is possible they maybe have a VFD or ECM motor in a standardized model used in other units and it is supplied through a transformer.
The reason you sent me to this post - no disagreements there.
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