Demand calculations in a residence

[Luis De Castro]

What do you mean they only accept a letter from the poco?

If it was a new build it would have to be calculated by the procedure, how is this any different? How could you ever size a new house service because there is no poco to write a letter?

This is an existing house which the original plans dont match what is in the field. Right now they have the whole house on the gen. The permit drawing, they had taken one of the panels out of the gen. so the calculations were okay, now we have a case wher we need to kow the highedt KW demand, here in South Florida usually is the cooling the highest during the peak summer

 

[Luis De Castro]

Thanks for your post but where I lived they only accept lleter from the Power Co. Of course you can also use a meter for one month having yhe fifteem minuted reasdings as per NEC 220-87

Are you talking about the optional calc?

 

[Birken Vogt]

I still don't understand why you can't just use the standard or optional method of residential load calculation and submit that.

 

[hornetd]

This is an existing house which the original plans don't match what is in the field. Right now they have the whole house on the gen. The permit drawing, they had taken one of the panels out of the gen. so the calculations were okay, now we have a case where we need to know the highest KW demand, here in South Florida usually is the cooling the highest during the peak summer

What I don't understand is how the plans approval office can require a letter from the electrical utility for an OPTIONAL standby generator. If the transfer is automatic they can only require that the ampacity of the generator is capable of carrying the loads that will remain connected to it after the load is transferred. Birken Vogt and others have pointed out the calculated load should be the only thing at issue. There is no requirement in the US National Electric Code (NEC) for an optional standby generator to meet a particular load level as long as it is appropriately protected against overload. Given the diversity of dwelling loads, on which the service sizing of 83% of load is based, if the calculation is properly done it is super unlikely that the generator will fail to carry the calculated load. 65,000 watts at 240 volts will provide 270 amperes.

Tom Horne