PI: 220.83

[wwhitney]

Two more 220 PIs today. I'm a little baffled on this one as to why or how the current wording could be there. So if I'm missing the point somehow and this PI isn't reasonable, please explain.

Cheers, Wayne

[I'm omitting a bunch of the text that doesn't change.]

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 or feeder, calculating the total load in accordance with 220.83(A) or (B) shall be permitted.
(A) Where Additional Air-Conditioning Equipment or Electric Space-Heating Equipment Is Not to Be Installed Present.
[ . . . ]
(B) Where Additional Air-Conditioning Equipment or Electric Space-Heating Equipment Is to Be Installed Present.
[ . . . ]

Statement of Problem and Substantiation for Public Input

The sole difference in the computations in 220.83(A) and 220.83(B) is that 220.83(B) specifies a 100% factor for any Air-Conditioning Equipment or Electric Space-Heating Equipment. Under 220.83(A), any such equipment would end up with a 40% factor. The current dividing line between 220.83(A) and 220.83(B) is based only on what new equipment is being installed.

So consider a two stage series of improvements to a dwelling unit, two separate projects under two separate permits, perhaps a year apart. The final stage may have a load calculation that differs depending on what order the improvements are done, even as the final installed result is the same. If all of the Air-Conditioning Equipment or Electric Space-Heating Equipment is added as part of the first stage, and the second stage contains no such equipment, the final load calculation will be subject to 220.83(A) and include only a 40% factor for the Air-Conditioning Equipment or Electric Space-Heating Equipment. Conversely, if the second stage improvement does include additional Air-Conditioning Equipment or Electric Space-Heating Equipment, then the final load calculation will be subject to 220.83(B) and include a 100% factor for the Air-Conditioning Equipment or Electric Space-Heating Equipment.

This difference in load calculation results for identical final configurations of equipment makes zero sense. Therefore I propose that the dividing line between 220.83(A) and 220.83(B) should be based on what equipment is present, not what equipment is being installed.

Please note that if this proposal is accepted, 220.83 may be further simplified by eliminating the A/B divide and just specifying the computation in 220.83(B) for all cases. I kept my proposal minimal for clarity.

 

[jaggedben]

This would make it marginally more difficult to justify downsizing a main breaker to meet 705 for solar installations where there was existing HVAC and no change to loads. So I'm not in favor.

 

[wwhitney]

This would make it marginally more difficult to justify downsizing a main breaker to meet 705 for solar installations where there was existing HVAC and no change to loads. So I'm not in favor.

The way the first sentence is written, you can't apply 220.83 unless you're adding loads. But you could add a trivial load for that to work.

But can you actually think of any technical justification for the making the A/B distinction based on what loads are present? I mean, even if the status quo makes your job slightly easier, isn't it completely nonsensical?

Cheers, Wayne

 

[wwhitney]

But can you actually think of any technical justification for the making the A/B distinction based on what loads are present?

Sorry I meant to say "based on what loads are being installed, rather than on what loads are present?"

Cheers, Wayne

 

[tortuga]

The way the first sentence is written, you can't apply 220.83 unless you're adding loads. But you could add a trivial load for that to work.

But can you actually think of any technical justification for the making the A/B distinction based on what loads are present? I mean, even if the status quo makes your job slightly easier, isn't it completely nonsensical?

Cheers, Wayne

I think I offered this in your earlier post on 220.83;
220.83 was first added in the 1975 NEC (as 220-31 then) and only intended for those old a 60 Amp residential services.
Back then there were lots of 60A services with 4 edison fuses, a range pull out and a main and people were adding small heating and AC loads to them.
Then in '84 there were proposals to remove the 60Amp restriction resulting the the weird A/B issue.
I'd say any changes would best supported by a some load data or a study.

 

[wwhitney]

I think I offered this in your earlier post on 220.83;

Thanks. Based on that info, seems like 220.83 was conceived of for services that had no "Air-Conditioning Equipment or Electric Space-Heating Equipment". Then the dichotomy based on what you are adding makes some sense, as it is equivalent to a dichotomy on what you will end up with.

I'd say any changes would best supported by a some load data or a study.

Sure, but that sounds like work. : - ) My proposals are generally about something that seems illogical or unclear. In this case, the idea that the value of the load calculation could depend on the order in which equipment is installed, rather than just the list of equipment installed.

Cheers, Wayne

 

[jaggedben]

The way the first sentence is written, you can't apply 220.83 unless you're adding loads. But you could add a trivial load for that to work.

I never thought about it much and focused on the title 'Existing Dwelling Unit', which is what I usually was dealing with. It has worked for me and been accepted by a number of AHJs so I'm going to keep using it if I can.

But can you actually think of any technical justification for the making the A/B distinction based on what loads are present? I mean, even if the status quo makes your job slightly easier, isn't it completely nonsensical?

Cheers, Wayne

It seemed intuitive to me that because AC and heating may be counter-coincident and such that it could call for a different calculation. But I admit on closer examination it seems like there's no reason to have the A/B distinction at all.

Also you're 'present' vs. 'not present' language creates new problems given the 'existing' and 'new load' content of the section. It's ambiguous.

Finally be careful what you wish for. Open up this can of worms and the CMP may decide to finally add EVs to 220 in a way that makes it a lot more difficult for people to electrify.

 

[jaggedben]

... My proposals are generally about something that seems illogical or unclear. ...

Simply making the code more internally consistent or clear is a dubious motivation for a PI by itself. It doesn't guide you to resolve inconsistencies in a helpful manner. You might resolve ambiguity in a way that decreases safety, or that increases costs without increasing safety.

 

[wwhitney]

Simply making the code more internally consistent or clear is a dubious motivation for a PI by itself. It doesn't guide you to resolve inconsistencies in a helpful manner. You might resolve ambiguity in a way that decreases safety, or that increases costs without increasing safety.

While it's possible to resolve ambiguity in that way, obviously the goal would be to resolve ambiguity in a way that does not decrease safety or increase cost. And ambiguity itself increases cost, in terms of time spent understanding what is intended, as well as possible disagreements with AHJs, etc.

Also you're 'present' vs. 'not present' language creates new problems given the 'existing' and 'new load' content of the section. It's ambiguous.

OK, if "present" and "not present" is ambiguous, what would be better? Supplied and not supplied?

Cheers, Wayne

 

[Cu>Al]

Although I don't completely disagree with you, it seems the State of California has a different position.
I would very much like your opinions on this.

CA LV2 EV charger service load calculator

 

[jaggedben]

Although I don't completely disagree with you, it seems the State of California has a different position.
I would very much like your opinions on this.

CA LV2 EV charger service load calculator

That document seems to be a fairly straightforward attempt to simplify 220.83(A) into a worksheet for an end user. I don't see the relevance to the issues Wayne is raising in this PI, or what constitutes a 'different position'.

 

[Cu>Al]

That document seems to be a fairly straightforward attempt to simplify 220.83(A) into a worksheet for an end user. I don't see the relevance to the issues Wayne is raising in this PI, or what constitutes a 'different position'.

Yes, this is a simplified version of 220.83A. It seems evident that the State of California doesn't want to calculate any existing loads at 100%.
Add up everything...and if it's less than 48kw (200A), then you can have a 100A main.
So, you won't be adding HVAC's @100% or EVs at 100%. If you check around, some jurisdictions are calculating EVs at 125%.
Most building departments provide 220.82 as their "LOAD CALC" hand-out, which is fairly conservative. However, many EV installers are finding the states worksheet and 220.83A much more generous.

 

[tortuga]

Yes, this is a simplified version of 220.83A. It seems evident that the State of California doesn't want to calculate any existing loads at 100%.
Add up everything...and if it's less than 48kw (200A), then you can have a 100A main.
So, you won't be adding HVAC's @100% or EVs at 100%.

That worksheet just simplifies the 220.83(A) Calc to the nearest standard size main breaker.
For example going backwards from the 48kw = 100A main value:
48000 - 8000 = 40000
40000 * .4 = 16000
Add back the first 8kW @ 100%:
And you get your 24kW
24kW / 240V = 100A

I think the 220.83(A) calc presumes in an old house the first 8kW is the larger of the heating or cooling load.
And (B) is saying if your making any changes to the AC or heating system you have to count the entire system at 100%
So in a way it creates an incentive for more efficient HVAC replacement. And a disincentive to leave behind less cost efficient heating like resistance heat. No way to know for sure without doing a study, but I imagine you could drop (B) altogether and use A in any situation.

 

[wwhitney]

I would very much like your opinions on this.

Well, the note at the end says "This is a voluntary compliance alternative." I'm curious if any jurisdiction has actually adopted this as an allowable alternative.

Cheers, Wayne

 

[Cu>Al]

That worksheet just simplifies the 220.83(A) Calc to the nearest standard size main breaker.
For example going backwards from the 48kw = 100A main value:
48000 - 8000 = 40000
40000 * .4 = 16000
Add back the first 8kW @ 100%:
And you get your 24kW
24kW / 240V = 100A

I think the 220.83(A) calc presumes in an old house the first 8kW is the larger of the heating or cooling load.
And (B) is saying if your making any changes to the AC or heating system you have to count the entire system at 100%
So in a way it creates an incentive for more efficient HVAC replacement. And a disincentive to leave behind less cost efficient heating like resistance heat. No way to know for sure without doing a study, but I imagine you could drop (B) altogether and use A in any situation.

Brilliant! Thank you, and it is workable until the gas cooktop goes out, and you can't buy them anymore.

 

[Cu>Al]

Well, the note at the end says "This is a voluntary compliance alternative." I'm curious if any jurisdiction has actually adopted this as an allowable alternative.

Cheers, Wayne

The city of San Diego and Solano County would be two. I'm sure there are more.

 

[jaggedben]

Yes, this is a simplified version of 220.83A. It seems evident that the State of California doesn't want to calculate any existing loads at 100%.
Add up everything...and if it's less than 48kw (200A), then you can have a 100A main.
So, you won't be adding HVAC's @100% or EVs at 100%. If you check around, some jurisdictions are calculating EVs at 125%.
Most building departments provide 220.82 as their "LOAD CALC" hand-out, which is fairly conservative. However, many EV installers are finding the states worksheet and 220.83A much more generous.

The presumption in the form is that only an EV charger is being added. Thus since any HVAC is existing the form follows 220.83(A). I doubt that whoever developed the form gave any thought to the logic behind the method. They just followed the code.

To be clear, Wayne is thinking about the logic behind the code language and proposing a change to the code that would essentially eliminate 220.83(A) and require HVAC to be counted at full nameplate every time. I'm not in favor mainly because it would make it more likely for EV chargers to trigger unnecessary and expensive service upgrades. I've done a lot of residential load calcs and also looked at a lot of residential consumption data and I've rarely found actual use to be anywhere near the load calc. I've looked at a huge house with a 400A service whose consumption did not exceed 100A average over a fifteen minute period during the course of a whole year. Granted, I'm in an area without as much HVAC load as the south and the valley. But all that is to say, I think that 220.83(A) is probably a suitable way to do a load calc (including EV charger) for many homes with existing HVAC, and I don't look forward to having it made more stringent.

 

[jaggedben]

Some AHJs, btw, are just outright ignoring the code and demanding EV chargers be counted at 100%, essentially on top of 220.83 or .82. On the one hand, I can see the point of that, since unlike other loads EV charging usually draws near full nameplate for hours without cycling. On the other hand, it's incentivized to be used at off peak times, not coincident with the rest of the customers peak load.

 

[tortuga]

To be clear, Wayne is thinking about the logic behind the code language and proposing a change to the code that would essentially eliminate 220.83(A) and require HVAC to be counted at full nameplate every time.

Instead of that I would do a base load study on that 8kw number, that was the sweet spot for adding to 60A services in the 70's and is probably out of date. I would keep the first 8kw for services less than 100A like it was originally worded in the 1975 NEC and change it to 14.4 kw for dwelling unit services 100A and over up to 250A.
Its really all just guesswork until someone does a large load study. But I could see a good case for CA funding one since they need to add electric loads to most all older homes for as little cost possible in the next ten years. With 14.4 Kw your counting the first 60A at 100%.

 

[tortuga]

Total Load rounded to nearest 1000VA​	Less 14.4kw​	40% of over 14.4kW​	Add back 14.4kW​	Main breaker rating​
38000​	23600​	9440​	23840​	100​
44000​	29600​	11840​	26240​	110​
53000​	38600​	15440​	29840​	125​
68000​	53600​	21440​	35840​	150​
83000​	68600​	27440​	41840​	175​
98000​	83600​	33440​	47840​	200​
113000​	98600​	39440​	53840​	225​
128000​	113600​	45440​	59840​	250​