How to comply with 220.87 when replacing existing loads?

[fuse_junkie]

Hello. I'm working on a town hall hvac renovation and I'm trying to verify that the panels/service can handle the new equipment. 220.87 says to make sure (existing loads x 1.25) + new loads < feeder/service rating. Am I still able to use this method when I'm replacing potentially half or more of that existing load with new equipment? I was floating the idea of taking (existing load x 1.25) - (connected load value of existing equipment to be removed) + (new continuous loads x 1.25) + (new non-continuous loads) and making sure that value doesn't exceed the feeder/service.

My confusion is that if I measure the existing load and just add the new load, I'm double counting a lot of equipment. On the flip side, I don't see where the NEC specifically allows me to do what I'm proposing above (at least in 220.87).

I'd appreciate it if anyone can offer some advice.

 

[LarryFine]

Welcome to the forum.

I think the best bet would be to calculate the entire thing as a new installation.

Continuous at 125% and the rest at 100%, regardless of new vs existing.

 

[JoeStillman]

(1.25 x existing load) - demolition + new equipment = new load

 

[wwhitney]

(1.25 x existing load) - demolition + new equipment = new load

That is obviously non-conservative. In that the primary reason to use 220.87 is that 1.25 * existing load is less than the calculated load. So subtracting the calculated load for the demolished equipment is overcounting. As an extreme example, if 1.25 * existing load were only half of the calculated load for the existing equipment, and you demolished half the existing load, your formula would give "new equipment = new load", ignoring the other half of the existing load.

Larry's suggestion is obviously conservative, but then you don't get any benefit from 220.87. But it may be the only option allowed without further data. [If you could meter the equipment to be demolished separately, then you could apply 220.87 using just the observed load for the equipment to remain.]

If you want to take any credit for the removed load, then you could try the approach, although there's no language in the NEC to support it:

1.25 * (observed load) * (calculated load to remain) / (calculated existing load) + (calculated load of new equipment).

As long as the load you're removing and the load that remains have similar characteristics as far as (observed load / calculated load), that's conservative. But if for some reason the load to be removed draws less current in practice relative to its calculated load than what remains, this is still non-conservative.

Cheers, Wayne

 

[JoeStillman]

That is obviously non-conservative. In that the primary reason to use 220.87 is that 1.25 * existing load is less than the calculated load. So subtracting the calculated load for the demolished equipment is overcounting. As an extreme example, if 1.25 * existing load were only half of the calculated load for the existing equipment, and you demolished half the existing load, your formula would give "new equipment = new load", ignoring the other half of the existing load.

Larry's suggestion is obviously conservative, but then you don't get any benefit from 220.87. But it may be the only option allowed without further data. [If you could meter the equipment to be demolished separately, then you could apply 220.87 using just the observed load for the equipment to remain.]

If you want to take any credit for the removed load, then you could try the approach, although there's no language in the NEC to support it:

1.25 * (observed load) * (calculated load to remain) / (calculated existing load) + (calculated load of new equipment).

As long as the load you're removing and the load that remains have similar characteristics as far as (observed load / calculated load), that's conservative. But if for some reason the load to be removed draws less current in practice relative to its calculated load than what remains, this is still non-conservative.

Cheers, Wayne

The whole point is to not have to run around an existing building and try to calculate the existing connected load.

 

[wwhitney]

The whole point is to not have to run around an existing building and try to calculate the existing connected load.

In which case there's no conservative way to take credit for the removed load, unless you separately record demand data on them.

Cheers, Wayne

 

[JoeStillman]

In which case there's no conservative way to take credit for the removed load, unless you separately record demand data on them.

Cheers, Wayne

In cases like the OP, you actually have that recording if you have a one-year set of electric bills. I have often used the delta between highest summer demand and highest winter demand and called it the cooling load. This only works if you DON'T have electric heat though.

 

[MyCleveland]

Hello. I'm working on a town hall hvac renovation and I'm trying to verify that the panels/service can handle the new equipment. 220.87 says to make sure (existing loads x 1.25) + new loads < feeder/service rating. Am I still able to use this method when I'm replacing potentially half or more of that existing load with new equipment? I was floating the idea of taking (existing load x 1.25) - (connected load value of existing equipment to be removed) + (new continuous loads x 1.25) + (new non-continuous loads) and making sure that value doesn't exceed the feeder/service.

My confusion is that if I measure the existing load and just add the new load, I'm double counting a lot of equipment. On the flip side, I don't see where the NEC specifically allows me to do what I'm proposing above (at least in 220.87).

I'd appreciate it if anyone can offer some advice.

If you are truly replacing (1-for-1) of most or all of the HVAC equipment, plus some yet to be determined ADDED LOAD, I would break this into two projects for load discussion purposes.

For the (1-for-1) replacements, I would identify each item replaced and its load, pic of nameplate. Then show on plans old/new load for each combination. As long as new load is <= old load, NO further discussion of these items are needed.

New load: validate through load history of existing load x 1.25 as you have noted and then compare to service size, you can determine your remaining capacity you have available for all other truly NEW loads. Spell this out in detail on your plans. Don't forget all this HVAC will be needing AFC labels, so start making calls to the utility NOW, or cling on to what is becoming the old TRADITIONAL method of passing it to the EC.

 

[Fred B]

220.87 only applies if you can get actual data from poco or can monitor to get a 15 minute reading over a 30 day period.

Look to 220.16(B). That also refers you back to 220.12 and 220.14

 

[Knightryder12]

Typically what I do on projects like this is add up the load removed and the load added (new equip). If the new equip is less, than I just do a simple load removed load added calculation on the plan.
As others have said, if the new load is more, than you have to get the load information from the POCO or put a recording meter on the service for 30 days.