# Mini Split Load Calc



## Dennis Alwon (May 9, 2009)

You have not shown us a load calculation but without doing one I would guess it may be overloaded


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## wildleg (Apr 12, 2009)

I did a calc and I come up with 67 amps, not sure if I made a mistake or not. you really should nail down the mini split - you can find out the exact info online, you don't have to guess. you didn't mention laundry, I assume there is central laundry. check out 220.83


General lighting	2940	
small appliance	3000	
laundry	0	?

Heat or AC baseboard	3500	
Heat or AC plus minisplit	9600	

Range	8000	
Dishwasher	1200	?
Water Heater ?

total watt	28240	

220.83 1st 8000	8000	
220.83 remainder	8096	

total watts	16096	
total amps	67.0666666667


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## mgraw (Jan 14, 2011)

A 2.5 ton heat pump is probably going to draw under 15 amps unless it has auxiliary heat strips. I would get the exact nameplate information before deciding what to do.


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## Mountain Electrician (Jan 22, 2007)

wildleg said:


> I did a calc and I come up with 67 amps, not sure if I made a mistake or not. you really should nail down the mini split - you can find out the exact info online, you don't have to guess. you didn't mention laundry, I assume there is central laundry. check out 220.83


220.83. Thanks! 

No laundry, no hot water, no fixed appliances. These are glorified hotel rooms. This is the only one I've seen in the building with a full size range. 

980 x 3 watts = 2940
range = 11200
small appliance = 3000


Total = 17140


First 8000 watts, plus remainder (9140) at 40% = 11656 watts

New AC load, greater than heat load 5275 watts

16,931/240 volts = 70.54

Sold!


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## wendon (Sep 27, 2010)

I think you used the calcs for resistance heat. You should be able to get the specs on it. Make sure it doesn't have strip heaters.


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## nrp3 (Jan 24, 2009)

The only issue I see with that is does this unit provide heat and what happens if they use the baseboards and the heat pump?


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## Mountain Electrician (Jan 22, 2007)

I told the salesman that the only way this would work was if it was an AC only mini split. 

He started with a single compressor/double head unit, which are (according to him) heat pump only, but two single units will be AC only. The AC load exceeds the heating load.


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## nrp3 (Jan 24, 2009)

Seems like more are coming with heat as well. Not that it's a bad thing, just doesn't help you.


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## Mountain Electrician (Jan 22, 2007)

nrp3 said:


> Seems like more are coming with heat as well. Not that it's a bad thing, just doesn't help you.


Heat is about 250 extra on a 2.5 ton unit, and you're right...more are coming with heat these days. My local electrical supplier stocks LG units, and with an 8 (?) hour refrigeration class I'm good to install them. Just haven't had the time or the need to do that yet. 

The two 9k units will be AC only, but I think even if they were heat pumps, at 18000 BTU/hr I'd still be good. Just haven't found too many specifics on the units showing total amperage. The ones I've seen online were at 10.5 amps for the 9k, so the 3.412 BTU per watt formula seems close.

9000/3.412 = 2638
2638/240 = 11 amps


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## mgraw (Jan 14, 2011)

Mountain Electrician said:


> Heat is about 250 extra on a 2.5 ton unit, and you're right...more are coming with heat these days. My local electrical supplier stocks LG units, and with an 8 (?) hour refrigeration class I'm good to install them. Just haven't had the time or the need to do that yet.
> 
> The two 9k units will be AC only, but I think even if they were heat pumps, at 18000 BTU/hr I'd still be good. Just haven't found too many specifics on the units showing total amperage. The ones I've seen online were at 10.5 amps for the 9k, so the 3.412 BTU per watt formula seems close.
> 
> ...


Mountain Electrician you are nowhere near the knowledge you need to install this. You are telling your customer they can not install what they want when you really have no clue about what you are talking about. Are you looking for mini splits or split systems?


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## LGLS (Nov 10, 2007)

Mountain Electrician said:


> I got a call last week from a salesman for a statewide oil and propane company looking for a quote on a mini split install in a small condo. I go to look at the job, he wants to install a 30000 btu heat pump in a @980 sq ft unit. The unit has an electric range, about 3500 watts of electric baseboard and is fed with a 240 volt 70 amp feeder. The only thing he can tell me about the heat pump is it requires a 40 amp breaker.
> 
> Google tells me there are @ 3412 BTU/hr in 1 kw, so using maths, I determine that the thing will pull almost 37 amps. Not going to work, and I tell him so. Of course he starts trying to pressure me to do it anyway, so the negotiations begin. He is currently proposing two 9000 BTU/hr units, which should a combined load of about 22 amps if I'm figuring this correctly. This would still put me a bit over the feeder rating, (if I was calculating a new feeder for the unit) but not horribly.
> *
> ...


Sounds like whoever their "regular" electrician is, won't do it, which is why they're calling you.


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## Mountain Electrician (Jan 22, 2007)

mgraw said:


> Mountain Electrician you are nowhere near the knowledge you need to install this. You are telling your customer they can not install what they want when you really have no clue about what you are talking about. Are you looking for mini splits or split systems?


I'm certainly not looking for a mini split, split system or banana split for that matter. I'm doing electrical only, installation is no problem. Run some wire, hook up some wire, go home. I was trying to make sure there is sufficient power available in the existing system to accommodate the added load. If my terminology was incorrect, I apologize. 

My original question was concerning calculating power requirements for mini split (ductless) AC or heat pump units. I told my potential customer they can't add a 30000 BTU per/hr heat pump to a 980 square foot condo with an electric range already installed and a 70 amp 240 volt service. Do you disagree? If so, please explain why.

After re-familiarizing myself with 220.83, I think that the two 9k BTU/hr AC only units will work in this instance. Do you agree?


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## Mountain Electrician (Jan 22, 2007)

mgraw said:


> A 2.5 ton heat pump is probably going to draw under 15 amps unless it has auxiliary heat strips. I would get the exact nameplate information before deciding what to do.


The salesman for the company supplying the unit told me the 2.5 ton requires a 40 amp breaker. Mitsubishi, I believe. It was a single compressor with two heads.


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## Mountain Electrician (Jan 22, 2007)

IslandGuy said:


> Sounds like whoever their "regular" electrician is, won't do it, which is why they're calling you.


You are 100% correct, their "regular" electrician is a friend of mine who is 1.5 hours away and doesn't like to crawl in attics anymore. He gave them a price reflecting this.


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## Vintage Sounds (Oct 23, 2009)

They aren't going to be using that baseboard heat while the ACs are going, are they? A pair of modern 9k units should only require a 240v 15 amp circuit each, protected by a 20A breaker. For that matter in that size class some companies like Fujitsu even make 120v models.


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## mgraw (Jan 14, 2011)

Mountain Electrician said:


> The salesman for the company supplying the unit told me the 2.5 ton requires a 40 amp breaker. Mitsubishi, I believe. It was a single compressor with two heads.


Mitsubishi has a 2.5 ton condenser with two heads with a 15 amp mca, 20 amp mocp at 230v. 

As for AC only or a heat pump what difference does it make watt wise.


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## mgraw (Jan 14, 2011)

Mountain Electrician said:


> I'm certainly not looking for a mini split, split system or banana split for that matter. I'm doing electrical only, installation is no problem. Run some wire, hook up some wire, go home. I was trying to make sure there is sufficient power available in the existing system to accommodate the added load. If my terminology was incorrect, I apologize.
> 
> My original question was concerning calculating power requirements for mini split (ductless) AC or heat pump units. I told my potential customer they can't add a 30000 BTU per/hr heat pump to a 980 square foot condo with an electric range already installed and a 70 amp 240 volt service. Do you disagree? If so, please explain why.
> 
> After re-familiarizing myself with 220.83, I think that the two 9k BTU/hr AC only units will work in this instance. Do you agree?


I don't know what the correct answers are. Look I am not trying to give you a hard time but what they need to do is get a HVAC contractor in to do a heating and cooling calculation. Then the HVAC guy can tell them what they need and you can tell them what it will take to get them there. Just picking out units based on amp draw is not going to work. If I were you I would not suggest units because if you are wrong you are going to own it forever.


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## Mountain Electrician (Jan 22, 2007)

mgraw said:


> I don't know what the correct answers are. Look I am not trying to give you a hard time but what they need to do is get a HVAC contractor in to do a heating and cooling calculation. Then the HVAC guy can tell them what they need and you can tell them what it will take to get them there. Just picking out units based on amp draw is not going to work. If I were you I would not suggest units because if you are wrong you are going to own it forever.


I'm sorry, I thought I explained that in my original post, that's exactly what's going on. I'm not trying to spec out the the tonnage of the unit my self, the salesman for the HVAC company did the heat loss calculation long before he called me. Based on the tonnage of the unit, (all I have to go by, he couldn't give me the running amps, just the OCD size) I'm trying to figure out what the largest AC that can be installed, power consumption wise. He started by engineering a 2.5 ton unit, but quickly dropped the size to 18000 BTU when I said I thought the 30000 BTU unit won't work. That tells me he was trying to sell the customer something they probably didn't need, is quite possibly a scum bag, and certainly won't have my back if things go south. He may not be the most trustworthy source of technical data, he just wants to sell ACs.

That's why I came here with my question, which was basically how to calculate power requirements for these ductless systems. I had been trying to do a straight BTU/hr to KW calculation, but that seems like it may be high. I've looked at different cut sheets online, but there seems to be a disparity between manufactures concerning power consumption, so the only thing I can do is get the nameplate data from whichever unit the salesman finally chooses.

As far as you trying to give me a hard time, it kinda seemed like you were. I'm an electrical professional looking for advice from other electrical professionals. I thought that's what this site was for. I don't know much about these units, and am hoping to learn more, and one way to do that is to ask questions. I am actually looking for someone with the correct answers to those questions, or at least a nudge in the right direction. Telling me "you really have no clue about what you are talking about" isn't just bad grammar, it could be taken as slightly insulting. Luckily, I'm not that sensitive. :thumbsup:


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## mgraw (Jan 14, 2011)

Mountain Electrician said:


> I'm sorry, I thought I explained that in my original post, that's exactly what's going on. I'm not trying to spec out the the tonnage of the unit my self, the salesman for the HVAC company did the heat loss calculation long before he called me. Based on the tonnage of the unit, (all I have to go by, he couldn't give me the running amps, just the OCD size) I'm trying to figure out what the largest AC that can be installed, power consumption wise. He started by engineering a 2.5 ton unit, but quickly dropped the size to 18000 BTU when I said I thought the 30000 BTU unit won't work. That tells me he was trying to sell the customer something they probably didn't need, is quite possibly a scum bag, and certainly won't have my back if things go south. He may not be the most trustworthy source of technical data, he just wants to sell ACs.
> 
> That's why I came here with my question, which was basically how to calculate power requirements for these ductless systems. I had been trying to do a straight BTU/hr to KW calculation, but that seems like it may be high. I've looked at different cut sheets online, but there seems to be a disparity between manufactures concerning power consumption, so the only thing I can do is get the nameplate data from whichever unit the salesman finally chooses.
> 
> As far as you trying to give me a hard time, it kinda seemed like you were. I'm an electrical professional looking for advice from other electrical professionals. I thought that's what this site was for. I don't know much about these units, and am hoping to learn more, and one way to do that is to ask questions. I am actually looking for someone with the correct answers to those questions, or at least a nudge in the right direction. Telling me "you really have no clue about what you are talking about" isn't just bad grammar, it could be taken as slightly insulting. Luckily, I'm not that sensitive. :thumbsup:


My apologies. My point was about HVAC not electrical. 3412 BTU/hr in 1 kw is for electric heat not a heat pump. You can not do a proper load calculation without getting the units data. I would really be concerned about doing work for somebody that is only interested in the "sale" and not doing the job properly.


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## chicken steve (Mar 22, 2011)

Methinks the only thing i could fault you on is listening to some  oilocracy salesman dangling the carrot here Mountain dude.

I _loath _salesmen btw, being they rarely back up what they sell , and have many many stories to back that up, but i digress

Your figures are of your profession, _not_ his. 

You will ultimately be responsible for the install, _not_ him. 

It's your license, permit and reputation , _not_ his

Stand your ground , and do not allow yourself to be coerced 

Good Luck

~CS~


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## Mountain Electrician (Jan 22, 2007)

chicken steve said:


> Methinks the only thing i could fault you on is listening to some  oilocracy salesman dangling the carrot here Mountain dude.
> 
> I _loath _salesmen btw, being they rarely back up what they sell , and have many many stories to back that up, but i digress
> 
> ...



Thanks, that's good advice and I intend to follow it. I just need the nameplate data before I can move forward with a quote. 

I want his company's business, but not enough to bend the rules.


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## chicken steve (Mar 22, 2011)

*No, i'm not that nice.....*



Mountain Electrician said:


> Thanks, that's good advice and I intend to follow it. I just need the nameplate data before I can move forward with a quote.
> 
> I want his company's business, but not enough to bend the rules.


Well we're often asked to _'hook up'_ equipment provided by others Mountain dude. 

Myself i stick to _my _end of the job just as _you're_ doing here, doing the 'lectrical math & code related details.

I'm not a hvac, heat,ac, guy , nor do i forward the _impression_ that i am, and rightly so as i get fairly po'd when they try impose themselves on _ my_ turf

Our company policy is, we will install YOUR equipment to code, and we _don't want to hear anything_ about how it's working out, if it's inadequate , expensive to run, not the right color, tech support from India, warranty , insurance or liability concerns.

I come on strong right up front with this, vocally as well as contractually, have lost my share of biz due to it, and you would not believe the number of _'lighting ladies'_, _'architects_' , AND_ salesmen_ that suddenly become spineless non committal wishy washy characters due to it

That goes double for all the green machine_ loonies_ out there btw.

~CS~


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## Dennis Alwon (May 9, 2009)

I would check out what size wire is run to the apts and see if the overcurrent protective device can be legally upsized


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## Mountain Electrician (Jan 22, 2007)

Dennis Alwon said:


> I would check out what size wire is run to the apts and see if the overcurrent protective device can be legally upsized


I did that already, #4 SER al, not in direct contact with insulation, had a 60 amp breaker, I will up size to a 70 amp. I think I got the last squeal out of that pig.


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