Capacity

[Calvin D. Cowles]

I feel I should know if this is a concern but........

Scenario: 200 Amp Service
Main Panel with following:
5 240 breakers totaling 270 Amps
1 of above breakers a 80 amp for sub panel
30 120 breakers totaling 600 amps

Sub panel (off 80 amp in main)
1 240 totaling 30 amps
4 120 totaling 80 amps

A problem??

[Gerry Beaumont]

Hi Calvin, there is little or no correlation between the service amperage and the total amperage of the breakers, 200 amps should be fine as the assumption is that not all the circuits would be drawing the max all at the same time.

Regards

Gerry

[James E. Braun, CMI]

What type of building is this?

[Calvin D. Cowles]

Single Family 3 story (finished basement).
Has heat pump for the basement (gas furnace w/ central air for main and upper), electric cooktop and oven, electric clothes dryer, gas tankless water heater.

[David P. Valley]

Calvin,

Never add up the amperage of the breakers as a total. That has nothing to do with the safety of this panel.

If each breaker is protecting one wire, then there is no issue with the supply portion of this 200 Amp panel.

Post pictures of your panel of concern, and your answers will be more precise.

[James E. Braun, CMI]

I am just wondering what the 5 breakers totaling 270 amps is for. The math just does not add up for a typicl residence.

[Calvin D. Cowles]

Yea, I understand that just totaling amperages doesn't mean much...this just seemed
like a really large poetential draw from the supply...that why I asked!!

James, the 5 240 breakers are
80 amps for 3 AC condensers (individual breakers at the ext. disconnects)
2 40's for the cooktop and oven
1 30 for the clothes dryer
1 80 for the sub panel

[George P. Wells]

Originally Posted by ccowles

I feel I should know if this is a concern but........

Scenario: 200 Amp Service
Main Panel with following:
5 240 breakers totaling 270 Amps
1 of above breakers a 80 amp for sub panel
30 120 breakers totaling 600 amps

Sub panel (off 80 amp in main)
1 240 totaling 30 amps
4 120 totaling 80 amps

A problem??

Electrical service size is based on calculated demand (demand factor). I created a simple Residential Electrical Service Size calculator that is free to download from my website (BestInspectors.Net).

I originally created the calculator to use in my electrical classes for electricians but it went into more detail than we need as home inspectors so I simplified it for my home inspector classes. If you have a question of whether an electrical service is large enough, all you have to do is answer basic questions about the house. The calculator will tell you the service size required (standard breaker size), the size of the service conductors, and conduit size. You can find the calculator in the "Free Stuff for Members area" http://www.bestinspectors.net/members.htm

For an idea of why we do not go by the connected load, think of heating and cooling equipment. We call those "non-coincident loads" because you would typically run one or the other but not both at the same time. Therefore, it is not necessary to size an electrical service to handle running both at the same time. That's the basic idea behind a calculated demand (aka demand factor).

Keep in mind that this is a teaching calculator and it is based on the NEC. The results are close to 100% accurate but in the event your results are borderline, I recommend having someone who is experienced at sizing electrical services do the calculations. It should be noted that it is common for local rules to deviate from the NEC. For example, some jurisdictions, use either Watts or VA exclusively (not both). The NEC has historically used both. The differences between Watts and VA are usually minimal in houses (I have a separate calculator for that). They might also have wattage schedules instead of using the NEC's square footage method.

[David P. Valley]

Originally Posted by ccowles

Yea, I understand that just totaling amperages doesn't mean much...this just seemed
like a really large poetential draw from the supply...that why I asked!!

James, the 5 240 breakers are
80 amps for 3 AC condensers (individual breakers at the ext. disconnects)
2 40's for the cooktop and oven
1 30 for the clothes dryer
1 80 for the sub panel

Only one(1) 40 AMP needed for an electric stove w/ oven.

Why 2?

[Calvin D. Cowles]

Seperate units

[David P. Valley]

Originally Posted by ccowles

Seperate units

Well that makes sense.

Calvin,

Would you happen to have pics of these panels in question?