mattvds
New User
- Location
- California, USA
- Occupation
- Home Owner
I'm installing solar batteries, which requires replacing my main panel and do load calculations based on NEC 220.83. I have a 240V 200A service, and no new loads are actually being added. But when the engineer for the solar company did the calculations, it showed my existing equipment was already well over 200A. So I'm trying to find out all the errors they made to unblock the permit.
I think I identified a few issues, and I wanted to run it by the knowledgable community here to make sure my understanding is correct, and ask for advice on how to handle some perhaps unique situations that I have.
1) I have 2 heat pump units with the following configuration: Both units have: 1 50A/2p breaker for condensor/evaporator and 1 30A/2p breaker for blower. The engineer calculated the total VA for A/C loads as sum of breakers * .75. This is much higher than the calculations obtained by looking at the LRA of the units and motor loads of the fans. Am I correct that I should use the actual loads versus basing it on the breaker size?
2) I have a 60A sub panel that contains mostly lighting loads, but also has an electric dryer load. They again used breaker size * .75 as the VA, instead of the nameplate VAs for the individual fixed appliances. I assume I can list the nameplate of the fixed appliance instead of the subpanel in the load calc? If so, how would I then show the "breaker size" for these?
3) Is there any modifers for multiple fixed appliances loads? 220.17 mentions applying a "demand factor". I have more than 4 non-cooking/non-hvac fixed appliances, so am I allowed to use the 75% multipler on the nameplate value on thoses? Likewise, we have 1 cooktop and 2 electric ovens, can I apply a demand factor to the nameplates of those, similiar to what is allowed with a range?
I think I identified a few issues, and I wanted to run it by the knowledgable community here to make sure my understanding is correct, and ask for advice on how to handle some perhaps unique situations that I have.
1) I have 2 heat pump units with the following configuration: Both units have: 1 50A/2p breaker for condensor/evaporator and 1 30A/2p breaker for blower. The engineer calculated the total VA for A/C loads as sum of breakers * .75. This is much higher than the calculations obtained by looking at the LRA of the units and motor loads of the fans. Am I correct that I should use the actual loads versus basing it on the breaker size?
2) I have a 60A sub panel that contains mostly lighting loads, but also has an electric dryer load. They again used breaker size * .75 as the VA, instead of the nameplate VAs for the individual fixed appliances. I assume I can list the nameplate of the fixed appliance instead of the subpanel in the load calc? If so, how would I then show the "breaker size" for these?
3) Is there any modifers for multiple fixed appliances loads? 220.17 mentions applying a "demand factor". I have more than 4 non-cooking/non-hvac fixed appliances, so am I allowed to use the 75% multipler on the nameplate value on thoses? Likewise, we have 1 cooktop and 2 electric ovens, can I apply a demand factor to the nameplates of those, similiar to what is allowed with a range?
