Adding central air load to service

Status
Not open for further replies.

pridelion

Member
My customer has an existing 100 amp main service with no sub panel,powering their 1956 1500s/f cape. They have an electric dryer & range. How would I calculate whether I could add on a load for a Central a/c compressor and air handler?
THANK YOU! (the rookie)
 

wyatt

Senior Member
Re: Adding central air load to service

Do you have the specs on the new ac and air handler, also electric heat?, gas, or heat pump?
Realy looks like your looking at a service upgrade.

[ January 29, 2006, 07:36 PM: Message edited by: wyatt ]
 

charlie b

Moderator
Staff member
Location
Lockport, IL
Occupation
Retired Electrical Engineer
Re: Adding central air load to service

You either have to calculate the load on the entire house (using the link from Infinity is one way to do that) or you may connect a load monitor and measure the peak load over a 30 day period. You can also use one year's worth of utility bills to get the peak load over that period.

In Washington State, there is a formal process for using measured data as part of a load calculation. The basic method is to take the highest reading over the time period, add 25%, then add your proposed new load. You might need to make a "seasonal adjustment," if your example you took your 30 day readings during the fall and the house has all-electric heat. If the final result is within the rating of your equipment, then you will be given a permit to perform the work.
 

bphgravity

Senior Member
Location
Florida
Re: Adding central air load to service

The NEC permits and "existing calculation" as per section 220.83(B) in your case. This calculation can save you from having to install a larger service.
 
Status
Not open for further replies.
Top