Article 220.83(A) - Air-Conditioning Loads

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Tainted

Tainted

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NEC 220.83 says the following:

220.83 Existing Dwelling Unit. This section shall be permitted
to be used to determine if the existing service or feeder is of
sufficient capacity to serve additional loads. Where the dwelling
unit is served by a 120/240-volt or 208Y/120-volt, 3-wire service,
it shall be permissible to calculate the total load in accordance
with 220.83(A) or (B).

(A) Where Additional Air-Conditioning Equipment or Electric
Space-Heating Equipment Is Not to Be Installed. The following
percentages shall be used for existing and additional new
loads.

My question is: No additional air-conditioning equipment is to be installed. So where do I include existing air conditioning loads in the calculation? It does not tell you anywhere to calculate it at 100%...
 
tortuga said:
I would wager its 220.83(A)(3)(a)
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Hard to say... I feel like it would conflict with the standard method and 220.82...

suppose initially the service was calculated using 220.82 with 100% factor for all AC loads. The load comes out to be 124.999999 amps so you would need 125A breaker.

After the job is done and everything is installed including the service and breaker, you would then want to add more load to the 125A breaker so you refer to 220.83 and apply the 40% rule to the AC loads meaning you could add more loads despite of what 220.82 tells you. It just doesn't make sense... tell me why wagering that is the right choice..
 
Interesting I had not considered all that, just well 220.83 opens with a "shall be permitted" and there is nothing else under (A).
 
tortuga said:
Interesting I had not considered all that, just well 220.83 opens with a "shall be permitted" and there is nothing else under (A).
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I've researched this a lot and there is no definite answer unfortunately... I admit that this answer doesn't really put my mind at ease with this article..
 
The way I read it is that you may use the new demand factor for the sq. ft, laundry and small appliance branch circuit. This is the same as the standard calculation except the demand is different. The rest of the calculation would be done as the optional calculation.
 
Dennis Alwon said:
The way I read it is that you may use the new demand factor for the sq. ft, laundry and small appliance branch circuit. This is the same as the standard calculation except the demand is different. The rest of the calculation would be done as the optional calculation.
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I'm not really sure what you mean. I don't think 220.83(A) is the same as the standard method but with different demand. Calculating using 220.83(A) is straight forward but there's 1 thing that bothers me, I don't even know where to include existing air conditioning loads, it doesn't tell you to even consider them as 100%.
 
If 220.87 determines max demand for existing buildings, then 220.83 only needs to be used for the additions & new equipment beyond that max demand.
 
But it doesn't really answer my question. Do I calculate the HVAC loads at 100% using 220.83(A) or do I include it in the 40% demand factor?
 
NEC reference chains lead to 100% Nameplate for air conditioning loads.

220.16 calls 220.14(C), which calls 440.6 for 100% HVAC Nameplate.

220.82(C) Optional method is 100% nameplate of the larger HV/AC load, except for multi-unit electric space heating demand factors.

220.83(A) can't be used for HVAC loads at all, much less at 40%

220.83(B) is for adding the larger of HV/AC load @ 100% to single existing unit.
 
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Tainted said:
NEC 220.83 says the following:

220.83 Existing Dwelling Unit. This section shall be permitted
to be used to determine if the existing service or feeder is of
sufficient capacity to serve additional loads. Where the dwelling
unit is served by a 120/240-volt or 208Y/120-volt, 3-wire service,
it shall be permissible to calculate the total load in accordance
with 220.83(A) or (B).

(A) Where Additional Air-Conditioning Equipment or Electric
Space-Heating Equipment Is Not to Be Installed. The following
percentages shall be used for existing and additional new
loads.

My question is: No additional air-conditioning equipment is to be installed. So where do I include existing air conditioning loads in the calculation? It does not tell you anywhere to calculate it at 100%...
Click to expand...
Option A, all loads combined first then apply appropriate percentage based on kVA to total loads, I also think like @tortuga said, existing HVAC loads calculations fit under 220.83(A)(3)(a) and based on nameplate rating.
 
Seems like there’s a mix of ‘yes and no’ answers here… In my opinion this deserves a public input as it is not clear who is right. I’ve searched everywhere and keep getting mixed answers
 
keep in mind 220.83 can only be used to calculate the existing loads on a single dwelling unit.
So say a house with a proposed new addition.
As a professional engineer / electrician your the person signing off on calcs your always allowed to be more conservative and use one of the other methods.
I say an appliance on a 'specific circuit' covers most HVAC. EDIT See art 100 def of appliance.
 
Not sure what your hung up on. Just carefully read what it says.

Existing air conditioning is not treated special under 220.83(A). Tortugas post #2 is correct.

There is no conflict with 220.82 because both are optional methods. You are not required to use either one but you can if you want to when the installation particulars permit that method.
 
Tainted said:
And new loads...?
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220.83 (A) and (B) both say "existing and additional new loads"

This reminds me of a remodel years ago at a restaurant, large commercial kitchen, 200A 240/120 hi leg service.
customers were wanting to add all kinds of stuff, I did a calc rounded up to 400A service.
Low bidder used existing 200A panel, I probably could have re-run the numbers lower, but went with my gut instinct.
We did not get that job, and I did not get fired.
But my name is not on that 200A service.
 
ramsy said:
Thats alright with me, my reading of the cross references it's not based on any particular experience.
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jaggedben said:
Not sure what your hung up on. Just carefully read what it says.

Existing air conditioning is not treated special under 220.83(A). Tortugas post #2 is correct.

There is no conflict with 220.82 because both are optional methods. You are not required to use either one but you can if you want to when the installation particulars permit that method.
Click to expand...
Let me put it this way:

So really what is the purpose of 220.82 if 220.83(A) will always give you a more liberal result? One could use 220.82 and then later on use 220.83(A) to add additional loads that 220.82 couldn't let you do because of the 100% AC loads. It just makes no sense then that 220.82 and 220.83(A) exist together, there should only be article 220.82 or 220.83(A), not both.
 
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