Mini split electrical specs

[h2ofun]

Am starting to play with what is the actual numbers for my house relating to how much I have, vs could it meet code spec for a 200A feed.
Just not clear what to use. What I see when using a few heads seems a lot less that things I see. Below is one of my compressors. I just seem things like max fuse, and then min circuit ampacity. I then find other info in a spec sheet. So what VA or watts do I use in my load calculations?

 

[Vines]

I believe that the compressor plus the fan is rated to pull no more than 22.43A continuously, or 5383 W at 240VAC.

EDIT, See Waynes response below, which is more accurate and code compliant.

 

[h2ofun]

I believe that the compressor plus the fan is rated to pull no more than 22.43A continuously, or 5383 W at 240VAC.

So, if I want to use this as Watts (W) to volt-amps (VA), what would I use?

 

[wwhitney]

Load calcs are always in VA. For a toaster (electric resistance heater) that's the same as watts. For anything else, hopefully it is labeled in VA, or labeled in V and in A, and you just multiply.

If you have just one motor or HVAC load on a feeder (or service), you just use the MCA (minimum circuit ampacity) for the A.

If you have multiple motors or HVAC loads on a feeder (or service), you could use the MCA for all of them, and it will be a conservative overestimate. To avoid the overestimate, for each MCA you need to look at the label and figure out the constituent loads. E.g. it might say compressor 12A, fan 1A, heater 5A. That should go along with an MCA of 21A, as the MCA is the sum of all the loads, plus 25% of the biggest motor load (the compressor in this example). Then once you've broken down all the MCAs, you get to add up all the loads, and just add 25% of the biggest motor of any kind on the feeder. [For the general case. For a dwelling unit load calc, HVAC loads are handled separately from non HVAC loads.]

BTW, say you have a purpose built piece of machinery that just uses a motor. In that case, you don't use the motor nameplate amps, you use the motor nameplate HP and look up the FLA (full load amps) in NEC Table 430.248 (for single phase, or nearby tables for other case). Then if that's the only motor on the feeder, you add 25% of it; otherwise, you throw it in the mix and add 25% of the largest motor on the feeder.

Cheers, Wayne

 

[wwhitney]

P.S. So take the name plate you posted. The important information is MCA 32.5A, and compressor RLA (a special term for compressors, treat it like a motor FLA) 20.0A. Since the RLA is over half of the MCA, the compressor is the largest motor, which is all we need to know.

So if a feeder is supplying just one of those and nothing else, the load on the feeder is 32.5A * 240V = 7,800VA. But if a feeder is supplying two of those and nothing else, the load is not double. Instead, you get to figure out that MCA - 25% of the largest motor = 32.5A - 5A = 27.5A. Then the feeder load is 32.5A (MCA) plus 27.5.A (MCA less 25% factor) = 60A, and at 240V that's 14,400 VA.

Cheers, Wayne

 

[h2ofun]

Load calcs are always in VA. For a toaster (electric resistance heater) that's the same as watts. For anything else, hopefully it is labeled in VA, or labeled in V and in A, and you just multiply.

If you have just one motor or HVAC load on a feeder (or service), you just use the MCA (minimum circuit ampacity) for the A.

If you have multiple motors or HVAC loads on a feeder (or service), you could use the MCA for all of them, and it will be a conservative overestimate. To avoid the overestimate, for each MCA you need to look at the label and figure out the constituent loads. E.g. it might say compressor 12A, fan 1A, heater 5A. That should go along with an MCA of 21A, as the MCA is the sum of all the loads, plus 25% of the biggest motor load (the compressor in this example). Then once you've broken down all the MCAs, you get to add up all the loads, and just add 25% of the biggest motor of any kind on the feeder. [For the general case. For a dwelling unit load calc, HVAC loads are handled separately from non HVAC loads.]

BTW, say you have a purpose built piece of machinery that just uses a motor. In that case, you don't use the motor nameplate amps, you use the motor nameplate HP and look up the FLA (full load amps) in NEC Table 430.248 (for single phase, or nearby tables for other case). Then if that's the only motor on the feeder, you add 25% of it; otherwise, you throw it in the mix and add 25% of the largest motor on the feeder.

Cheers, Wayne

Wow, so much to learn.
So, as just one breaker, (is this a feed?), I have a 100 amp breaker that drives 3 mini split compressors.
mxz-3c24na2 FLA 2.43 RLA 12 So that 3463 watts, but the MCA says 22.1 or 5304 watts (More than your 25%)
mxz-5c42na2 FLA 2.43 RLA 20 So thats 5383 watts. but the MCA is 32.5 or 7800 watts (More than your 25%)

Which one to use?
Looking at the specs of my kitchen stuff now

 

[Vines]

Load calcs are always in VA. For a toaster (electric resistance heater) that's the same as watts. For anything else, hopefully it is labeled in VA, or labeled in V and in A, and you just multiply.

If you have just one motor or HVAC load on a feeder (or service), you just use the MCA (minimum circuit ampacity) for the A.

If you have multiple motors or HVAC loads on a feeder (or service), you could use the MCA for all of them, and it will be a conservative overestimate. To avoid the overestimate, for each MCA you need to look at the label and figure out the constituent loads. E.g. it might say compressor 12A, fan 1A, heater 5A. That should go along with an MCA of 21A, as the MCA is the sum of all the loads, plus 25% of the biggest motor load (the compressor in this example). Then once you've broken down all the MCAs, you get to add up all the loads, and just add 25% of the biggest motor of any kind on the feeder. [For the general case. For a dwelling unit load calc, HVAC loads are handled separately from non HVAC loads.]

BTW, say you have a purpose built piece of machinery that just uses a motor. In that case, you don't use the motor nameplate amps, you use the motor nameplate HP and look up the FLA (full load amps) in NEC Table 430.248 (for single phase, or nearby tables for other case). Then if that's the only motor on the feeder, you add 25% of it; otherwise, you throw it in the mix and add 25% of the largest motor on the feeder.

Cheers, Wayne

Good points Wayne, thanks for the correction on the load calcs. My calculation completely ignores the minisplit "heads" which can be of various BTU ratings.

 

[getakey]

I decided to install a mini-split on the lowest level of my house where my office and "wine room" is. It's a long narrow room, probably 50ft by 12 ft. The 50 ft wall faces east outside exposure. My house goes down from street level. The room has one vent from the heat pump that primarily serves the second level of the house, but it just does not get much air flow. Summer isn't that much of a problem because of the east exposure and it is down 2 levels. I've been using a wood stove that was existing, but wood has gotten so expensive. I'll leave the stove for occasional use and add the mini-split for everyday use.

The installer is recommending a 1.5 ton.

 

[wwhitney]

A branch circuit is the wiring from a breaker (or fuse) to the utilization equipment (load). A service is the wiring from the utility before any breakers on your property. Everything else is a feeder. So assuming each compressor unit is further protected by a smaller breaker or fuse, the 100A breaker would be protecting a feeder.

On the compressors data you posted, forget the fan FLA. All you need is MCA 22.1 / 32.5 and RLA 12 / 20 (since the RLA for the compressor is the largest motor load in each unit).

So let's say "total unfactored load" = MCA - 25% RLA = 19.1 / 27.5 respectively. For a feeder supplying only those 3 compressor units, the "total unfactored load" is the sum (which is either 65.7 or 74.1, depending on which model you have two). Then for the total feeder load, you need to add back 25% of the largest motor, which in this case will be 5A additional (25% of the 20A RLA on the larger unit). Then multiply by 240V to get VA.

Cheers, Wayne

 

[wwhitney]

Good points Wayne, thanks for the correction on the load calcs. My calculation completely ignores the minisplit "heads" which can be of various BTU ratings.

The heads are typically powered by a circuit from the outdoor unit, right? That's the way my single "head" (air handler) unit works, not sure if it's different when heads to outdoor units are not 1:1.

So then the load of those heads should be reflected in the MCA on the outdoor unit, I would think. Which is probably one reason for the info the OP posted, MCA is bigger than 125% * RLA + FLA.

Cheers, Wayne

 

[Vines]

The heads are typically powered by a circuit from the outdoor unit, right? That's the way my single "head" (air handler) unit works, not sure if it's different when heads to outdoor units are not 1:1.

So then the load of those heads should be reflected in the MCA on the outdoor unit, I would think. Which is probably one reason for the info the OP posted, MCA is bigger than 125% * RLA + FLA.

Cheers, Wayne

Correct from my very limited experience, they are fed from the compressor unit. Also, the indoor heads come in different sizes that are somewhat interchangeable. The MCA likely reflects the worst-case combination.

 

[h2ofun]

The heads are typically powered by a circuit from the outdoor unit, right? That's the way my single "head" (air handler) unit works, not sure if it's different when heads to outdoor units are not 1:1.

So then the load of those heads should be reflected in the MCA on the outdoor unit, I would think. Which is probably one reason for the info the OP posted, MCA is bigger than 125% * RLA + FLA.

Cheers, Wayne

I have multiple heads on each compressor, and they are different sizes

 

[dafish]

I believe your plate tells you exactly what you need for a breaker, right?

MCA 32.5 amps. As a HVAC product this is subject to the 125 continuous use specification. Which is why the recommended breaker is 40 amp.

Load? Running or startup? Startup, as in what you'd need from a generator, can be significant. That's LRA (locker rotor amps) plus fan. RLA is roughly running amps, and you'd total the compressor and fan.

BTW, I run a very large home, complete w/6 ton Geothermal, on 200 amp and have never had an issue (20 years now).

What's this "meet code spec for 200A" thing? When I build my house nobody gave a hooka. I picked out what service I thought I could live with (been right so far), and nobody cared. BTW, we once tested my total current demand in my house. With every possible thing running, and I mean right down to sump pump on, disposal, toaters, and two vacuams, (you get the idea) I was pulling something like 330 amps over a 200 amp service. And it didn't blow.

Back then a ton of that was lighting (lots of light in house). Now, with LED in everything, I doubt I could break 200 if I tried.

I can say this: Long-term I'm pretty sure we'll all be charging our cars at work. Short-term most folks aren't pulling enough power at night to matter. Someplace in the middle there will be some dual EV's homes trying to take something like 130 amps during the night. I know my power loads pretty well. I would be reluctant to allocate less than 60 amps (12kva) to running my home at night (5,200 sq'). During the day I would need at least 100 amps. But I don't use electric dryers either, so..

So in my home, my size, my build, 200 amp could, maybe, get tight someday but even then would still be viable.

 

[h2ofun]

I believe your plate tells you exactly what you need for a breaker, right?

MCA 32.5 amps. As a HVAC product this is subject to the 125 continuous use specification. Which is why the recommended breaker is 40 amp.

Load? Running or startup? Startup, as in what you'd need from a generator, can be significant. That's LRA (locker rotor amps) plus fan. RLA is roughly running amps, and you'd total the compressor and fan.

BTW, I run a very large home, complete w/6 ton Geothermal, on 200 amp and have never had an issue (20 years now).

What's this "meet code spec for 200A" thing? When I build my house nobody gave a hooka. I picked out what service I thought I could live with (been right so far), and nobody cared. BTW, we once tested my total current demand in my house. With every possible thing running, and I mean right down to sump pump on, disposal, toaters, and two vacuams, (you get the idea) I was pulling something like 330 amps over a 200 amp service. And it didn't blow.

Back then a ton of that was lighting (lots of light in house). Now, with LED in everything, I doubt I could break 200 if I tried.

I can say this: Long-term I'm pretty sure we'll all be charging our cars at work. Short-term most folks aren't pulling enough power at night to matter. Someplace in the middle there will be some dual EV's homes trying to take something like 130 amps during the night. I know my power loads pretty well. I would be reluctant to allocate less than 60 amps (12kva) to running my home at night (5,200 sq'). During the day I would need at least 100 amps. But I don't use electric dryers either, so..

So in my home, my size, my build, 200 amp could, maybe, get tight someday but even then would still be viable.

I twice turned on everything, and I got like 35kwh, which I think is like 145 amps?

If I were to make changes, I assume the building department would want numbers

 

[dafish]

Depends on where you got the 35KWH, and for how long. If that was an instant read on your meter then it's 35,000/240. So yep, just over 145amps.

You are never ever going to see that happen. Now, did that include charging your car, and was it at fill bore?

Ah, building permits. You need a permit to add a minisplit? We added one to my sons man-cave garage and didn't do spit. I guess the HVAC guys might have, but I don't think so..

ATB,

-d

 

[h2ofun]

Depends on where you got the 35KWH, and for how long. If that was an instant read on your meter then it's 35,000/240. So yep, just over 145amps.

You are never ever going to see that happen. Now, did that include charging your car, and was it at fill bore?

Ah, building permits. You need a permit to add a minisplit? We added one to my sons man-cave garage and didn't do spit. I guess the HVAC guys might have, but I don't think so..

ATB,

-d

I did it for I believe an hour, so was in my green button data. (I did at least twice) I had zero EV car charging going. But I did have everything including the kitchen sink.
permit for a mini split, you bet! Technically anything I believe with electrical or gas should have a permit. If one ever had a fire
and was traced to something without a permit, good luck getting insurance coverage it would seem.

 

[wwhitney]

I have multiple heads on each compressor, and they are different sizes

Right, but the MCA should already include the heads, per my discussion with Vines. So you don't have to look at the heads.

Cheers, Wayne

 

[dafish]

Ah yes. California. My bad. I suppose so.

Anyway, hard to think you'll need more than 200.

Lock to you!

-d

 

[wwhitney]

MCA 32.5 amps. As a HVAC product this is subject to the 125 continuous use specification. Which is why the recommended breaker is 40 amp.

No, the MCA already includes the extra 25% for the largest motor, you don't need to apply a 125% continuous use factor on top of it. The breaker size is larger to allow for motor startup current, not due to a continuous load issue.

For example, a bare motor with a Full Load Amps (from the NEC Table I referenced) of 20A would need conductors of 25A ampacity, but could use a breaker up to 50A. The motor itself would then also have separate overload protection; the breaker is only providing short circuit and ground fault protection.

Cheers, Wayne

 

[Xenoilphobe]

I just installed 5 mini splits (3 LG 12K units and 2 ThermoCore 9K units) at my second home, replacing a 20 year old oil burner. All my systems required 240/15Amp breakers and I installed surge protectors as well on each unit. Specs for the units include the indoor cassette mounted on the interior wall.

I did one to one main room installs to keep the SEER 25.5 EER 13.8 and HSPF 12.5 rating as efficient as possible and to provide redundancy. This required a sub panel, put was not really that hard to do. I also added a heat pump water heater.

I wall mounted the condensers, and probably won't do that next time, as I was getting resonant sounds at certain speeds, I was able to fix that by adding Silicon Vibration Mounts - VIBRATION MOUNTS - V10Z61MTHTW | Advanced Antivibration Components eliminating the low frequency vibration.