Thread: 100 AMP Adequacy

Just want to revisit whether 100 amps is enough for a typical 1700 square foot home with all electronic applicances (except gas supplied heat) i.e., one A/C, one range, one electric water heater, one dryer hook-up, and misc. ? Typically, this is ok?

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While a 100 amp service may be adequate for some in a 1700 sq. ft. structure, it leaves no room for additional equipment or expansion in the future. I'm not sure about areas other than the NE Arkansas region, but around here the Utility company requires 200 amp meter bases and panels before they will connect a new service and on most remodels or rehabs if the service has to be moved.
Check with the local building or code inspectors for their requirements, if they allow and the utility allows.........

David,

I would be careful using terms such as "Adequacy".

If someone wants to know if a 100 amp, or even a 900 amp service on a small two bedroom house is "adequate" - recommend they contact a licensed and qualified electrical contractor to do a load calculation for the structure.

David,

Like Jerry said, determining adequacy is beyond the scope of the home inspector.

However, I have had a 100 amp main breaker "trip" while testing the range, A/C and water heater simultaneously. This is worth reporting.

One thing to keep in mind: my area (Chicago) even a properly installed 100A panel may not be acceptable to some homeowners' insurance companies if it's fused.

Originally Posted by Michael Thomas

fused panel may not be acceptable to some homeowners' insurance companies.

In South Florida, and probably all of Florida, insurance companies would not insure a "fused panel" ... the insurance companies wanted the 'FUSED panel' replaced with one with breakers - no fuses allowed.

Same here. Any fuse "boxes" or panels, no matter their condition, are likely to be an in$urance problem.

Just did a 3400 sq ft 2-story home, with pool, dishwasher, w/d, etc. with only 150-amp service. I asked if they ever had breakers trip, and the selling agent just looked at me - he never did answer...
Of course, after the poly piping, I guess they're lucky...

Last week, inspecting a by level with a 200 amp service. The interior temperature of the home was about 50 degrees, exterior temperature close to 30 degrees. The heat source for this home is electric baseboard heat.

When I arrived I turned “all” of the baseboard heaters up and went outside for approximately twenty minutes. Came back into the home, no lights are on, did the power go off? No the main breaker tripped, none of the branch circuit breakers tripped. I committed the “sin” I reset the main breaker, the main held for approximately 15 minutes and tripped out again.

Further evaluation of the panel, the main was forced to fit in the panel, parts of the breaker had been broken away to secure it to the bus bars.

Description of the obvious and Recommend a licensed electrician to further evaluate and repair as needed.

This was a first for me.

Michael P.

Originally Posted by Michael Patton

Further evaluation of the panel,

"Further evaluation" - that was not needed. Any electrician looking at the panel would, of course, first have to assess (evaluate) the panel to know what to do. By saying 'further evaluation needed' you are saying 'I did not inspect it, have it inspected by a qualified person, I am not qualified', yet you did, to some extent, "inspect it".

This was needed:

the main was forced to fit in the panel, parts of the breaker had been broken away to secure it to the bus bars.

Simply state what you found, and that all that needs to be corrected, plus anything else they find or cause when doing those repairs.

Description of the obvious and Recommend a licensed electrician to further evaluate

Again, "further evaluate" is not needed, describe the problem and report that a licensed and qualified electrical contractor needs to do a load calculation on the house and make corrections as needed. By opening up the "further evaluate" Pandora's Box you are allowing the electrician (typically hired by the seller to make repairs) to say 'tain't nuttin' wrong, jus' don't turn all the dang baseboard heaters on at da same time ... any fool coulda tolled ya dat' - and there you have, and are stuck with, your "further evaluate" by a licensed electrician.

I am in Western Pennsylvania. The majority of existing homes in this area have 100 amp service. It never seems to be called into question. Insurance companies only require 100 amp service here as well. The reason is that natural gas is the predominate method of heating.

While I never had a main breaker trip while on an inspection, if this did happen, I would wonder if there was specific problem with the electrical system outside of its amperage capacity? I know that my job is to report what I see, so don't correct me on it. I would be careful however, making any statements that the service is not adequate. In the case of the baseboard heat, if the load is not balanced on the bus, then one phase could be drawing too much current, while the other has much less load. This condition will cause the main breaker to trip.

Originally Posted by Ray Fonos

In the case of the baseboard heat, if the load is not balanced on the bus, then one phase could be drawing too much current, while the other has much less load. This condition will cause the main breaker to trip.

Aren't most baseboard heaters 240 volts? If so, these would not be "unbalanced".

All the more reason to ...

Originally Posted by Jerry Peck

... describe the problem and report that a licensed and qualified electrical contractor needs to do a load calculation on the house and make corrections as needed.

Jerry,

The description within the report and need for repair was much more descriptive of multiple conditions identified as I indicated. "Description of the obvious and Recommend a licensed electrician to further evaluate and repair as needed."


Thanks for the critique but for the purpose of the post, I was only identifying a condition that I had not previously experienced as it related to the original post of service adequacy.

Michael P.

Originally Posted by Michael Patton

... to further evaluate ...

Yes. I saw that.

Thanks for the critique ...

You are welcome.

... but for the purpose of the post, I was only identifying a condition that I had not previously experienced ...

I got that part in your post.

Check with AHJ. My jurisdiction requires 200 Amp for over 1200 SF not matter what type of heat. Also you need to plan for expansion of this house, some one may want to add something later. I think that 100 amp service for 1700 sf is a little small.

Feel free to do a "sizing electric services" calculation for your own info and knowledge. This is in NEC and Code Check, various editions, including page 13 of CC Electrical 4th Edition.

Forget about future needs, for this purpose. NEC wants you to cover the existing situation. If your calculations come up with 99 amps then a 100 is fine and you have a defensible position. If it comes to 101 amps then you should think 125 or larger panel.

Let us know what you come up with.

JB

Originally Posted by David Edens

Just want to revisit whether 100 amps is enough for a typical 1700 square foot home with all electronic applicances (except gas supplied heat) i.e., one A/C, one range, one electric water heater, one dryer hook-up, and misc. ? Typically, this is ok?