# Service size for 3+ appliances

Originally Posted By: dmacy
This post was automatically imported from our archived forum.

If a home has 4 major electrical appliances(Dryer,Stove,Tank and HVAC) is it code to have a 200 amp service or is 150 acceptable.

In a all electric home would you recommend installing a power monitor?

Thank you

Dave

Originally Posted By: Thomas Ogryski
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David,

The number of appliances is not the determining factor, the load is. Also, the actual square footage of the house enters into the calculation, so there is no easy way to determine the actual required minimum service size without doing the calculation.

Taking a S.W.A.G., if the house in question is fairly small, 150 would probably do the trick. I have always hated this size of service since , for a few dollars more, you could have has a 200 amp service.

Tom

Originally Posted By: jlybolt
This post was automatically imported from our archived forum.

Need to run load calcs. This is fairly simple and most do it yourself electrical books give examples on how to calculate load.

Hope this helps.

Originally Posted By: Thomas Ogryski
This post was automatically imported from our archived forum.

A quick look in the back of the NEC will show some very good examples of load calculations, along with code references.

Tom

Originally Posted By: dvalley
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Here ya go…

General Lighting

Take the square footage of the house times 3va (volt-amperes)= __________ then add that number to 4500, which would be 2 small appliances and 1 laundry load.

******************************************************

Take this subtotal and determine the *total general lighting load & small appliance as follows:

Take the first 3000 at 100% 3000

Take the remainder at 35% _____
and small appliance minus 3000)

Then add those two together to
obtain the *total general
lighting load & small appliance _____

******************************************************

Now determine the following and add them to the *general lighting load & small appliance:

Dishwasher 1200 va

Disposal 1200 va

Dryer 5500 va

Oven 8000-12000
(On the oven check the breaker size. If it is a 40 amp breaker it is 8000. If it is a 50 amp breaker it is 12000.)

Air Conditioner 5500-12000
(On the air conditioner, 700 sq ft requires 1 ton of air conditioning. A house of 2800 sq ft would require 12000 va whereas a house of 700 sq ft would only require 5500 va.)

Swimming pool 1500

Hot Tub 9000
(On the hot tub if the breaker is a 50 amp it would require 9000. If it is a 30 amp, it would require 6000.)

Electric Heaters, well pumps, and compressors would be figured out by taking the breaker size times the voltage required to use the breaker, and then times 35%. ( A single pole 20 amp breaker would result in 840 va [120 x 20 x .35=840]. A 20 amp two pole would be 1680 va [240 x 20 x .35=1680].)

******************************************************

Take the total of the above and divide it by 240 volts. The result will be the total amount of amperes needed by the house.

A house at 80 amperes or less is good for a 100 amp panel and service.

A house at 81 amperes to 90 amperes is marginal for 100 amp panel and service.

Anything over 90 amperes should be upgraded to at least a 150 amp panel and service.

A house at 160 amperes or less is good for a 200 amp panel and service.

A house at 161 amperes to 180 amperes is marginal for a 200 amp panel and service.

Anything over 180 amperes should be upgraded to a higher than 200 amp service and panel.

Here is an example of a load calculation:

The house is 2000 sq ft, therefore 2000 x 3va =6000

6000 + 4500= 10500

The 1st 3000 is at 100% 3000
The remainder of 7500 is at 35% 2625

The sum of these two is: 5625

This number is the general lighting load and small appliance.

The house has a disposal 1200
A dishwasher 1200
A electric dryer 5500
A electric oven at 50 amps 12000
A air conditioner 10000

The sum of all these appliances plus the general lighting load and small appliance is: 35525

Take 35525 and divide it by 240 volts = 148 amps

This house would require a panel and service upgrade to at least 200 amps.

--
David Valley
MAB Member

Massachusetts Certified Home Inspections
http://www.masscertified.com

"Some cause happiness wherever they go; others, whenever they go."