HVAC Actual Power Draw
- Thread starter Zyb
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petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- engineer
The current draw shown is just current. You would need to know the power factor to actually calculate the load in Watts.
You can calculate the worst case VA, which would be (16.7+1.7)*208*sqr(3).
MCA tells you what minimum size to make the wires bring the power in.
You can calculate the worst case VA, which would be (16.7+1.7)*208*sqr(3).
MCA tells you what minimum size to make the wires bring the power in.
petersonra
Senior Member
- Location
- Northern illinois
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- engineer
OOPS. I missed that it said the incoming power was "2" phase. So leave out the sqrt(3). Incidentally it is not really two phase.
I am curious though about the model that is indicated as having "4" phase power.
winnie
Senior Member
- Location
- Springfield, MA, USA
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- Electric motor research
For what purpose do you need the 'actual maximum power draw'?
If you are trying to size something like backup system energy storage, then you need both the power consumption during worst case thermal conditions but averaged over a period of time. But if you are trying to size something like the inverter or alternator for that backup system, you need to look at the starting transient. For things like sizing feeder conductors, you need VA not power.
-Jon
If you are trying to size something like backup system energy storage, then you need both the power consumption during worst case thermal conditions but averaged over a period of time. But if you are trying to size something like the inverter or alternator for that backup system, you need to look at the starting transient. For things like sizing feeder conductors, you need VA not power.
-Jon
Thank you. This helps
- Location
- New Jersey
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- Journeyman Electrician
electrofelon
Senior Member
- Location
- Cherry Valley NY, Seattle, WA
I have found that HVAC equipment quite reliability draws about 66% of the MCA.
jaggedben
Senior Member
- Location
- Northern California
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- Solar and Energy Storage Installer
For conventional single speed compressors, I presume?
electrofelon
Senior Member
- Location
- Cherry Valley NY, Seattle, WA
IVe found it is close to that for both mini splits and things like three phase package units.
Joethemechanic
Senior Member
- Location
- Hazleton Pa
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- Electro-Mechanical Technician. Industrial machinery
I really don't get what's up with the 2 phase and 4 phase on the table. I haven't seen any manufacturer making 2 phase equipment in decades, and 4 phase?????????
Was this made up in China with the use of a poor translator?
Was this made up in China with the use of a poor translator?
winnie
Senior Member
- Location
- Springfield, MA, USA
- Occupation
- Electric motor research
I think it has something to do with the Lunar calendar and the parts of the month when the system will function....
Curious about the 2 phase. If your correct then shouldn’t the voltage range for the 1 phase have 120v ? . To me your maybe selecting a unique voltage/phase even though I see the thought process, sometimes you have to assume what the person that prepared the spec sheet is trying to present.
Joethemechanic
Senior Member
- Location
- Hazleton Pa
- Occupation
- Electro-Mechanical Technician. Industrial machinery
This is two different flavors of 2 phase. Believe me, nobody is installing it on purpose anymore. Where it still exists, when you need replacement stuff, it's all custom made
I
Look for the HVAC cooling capacity in BTU per hour and the Energy Efficiency Ratio EER (BTU/watt-hour).
Divide the cooling capacity by the EER and you get the electrical input required in watts.
You need to divide the resulting wattage by the supply voltage and the PF to get the correct amp value.
(BTW, that only tells you of the amp draw of your compressor. You have to add the amp draw of the other auxiliary loads of the HVAC (fans plus control power required.))
It would be best to look for the mechanical data and compute from there.
Look for the HVAC cooling capacity in BTU per hour and the Energy Efficiency Ratio EER (BTU/watt-hour).
Divide the cooling capacity by the EER and you get the electrical input required in watts.
You need to divide the resulting wattage by the supply voltage and the PF to get the correct amp value.
(BTW, that only tells you of the amp draw of your compressor. You have to add the amp draw of the other auxiliary loads of the HVAC (fans plus control power required.))
electrofelon
Senior Member
- Location
- Cherry Valley NY, Seattle, WA
Or use 66% of the MCA
- Location
- San Francisco Bay Area, CA, USA
- Occupation
- Electrical Engineer
Had to be…
Probably a misinterpretation of 240/120 3 phase 4 wire, because they would have no frame of reference for anything so out of their experience.
- Location
- San Francisco Bay Area, CA, USA
- Occupation
- Electrical Engineer
Outside of North America, 2-out-of-three phases is called “2 phase”, whereas here we refer to it as “single phase” because for us, true “two phase” power still exists in some pockets (like old Philadelphia).
jaggedben
Senior Member
- Location
- Northern California
- Occupation
- Solar and Energy Storage Installer
Sorry, but what exactly does '2-out-of-three phases' mean here? Do they have equipment that actually draws power from two L-L voltages and not a third, like ours? Or are we just talking about using two out of three available line conductors? I don't see how you get 4-phase from the former convention.
I've always maintained that conductors should be labeled L1, L2, etc and that 'phase" should be used only to refer to a combination of two line conductors. I recognize not everyone is on board with that. But as this example shows the alternatives just really don't make any sense.
mtnelect
HVAC & Electrical Contractor
- Location
- Southern California
- Occupation
- Contractor, C10 & C20 - Semi Retired
This might help to explain.
JoeStillman
Senior Member
- Location
- West Chester, PA
That chart in the original post is suspect. It isn't using conventional terms in the voltage column. Two hot legs from a three-phase source are NOT two-phase. (See Joe the mechanic above.) And we never did call two-phase "four-phase", even though we could have if we followed the (incorrect) convention that each wire is a "phase".
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