100 amp service

Len Couey · 05-12-2011, 02:40 PM

On a inspection today, in a 3 BR 3 bath 1991 home, with gas heat and gas water heater also gas range. Opened the main dissconnect and observed 100 amp service with proper size wiring for 100 amp service.
Just thought it was unusual not to have 200 amp service.
Any ideas, should this be called out.

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Guy W Opie · 05-12-2011, 03:24 PM

A 100 amp service is common in my area for that year house. In most areas it is the minimum size allowed.
I do not see any need to write it up.

**Dom D'Agostino** · 05-12-2011, 03:27 PM

There are plenty of newer homes than that around here, all electric even, no gas at all. with only 150 amp service.

**John Kogel** · 05-12-2011, 05:26 PM

Originally Posted by Dom D'Agostino

There are plenty of newer homes than that around here, all electric even, no gas at all. with only 150 amp service.

There can be a big difference between 100 amp service and 150 amp.

If you run all the standard appliances plus baseboard heat in an average-sized, say 2,000 sq ft house, 100 amp is not quite enough, but 150 amp is more than enough.

If the house has some gas appliances, 100 amps is usually adequate. These are just general observations of mine, not based on any load calcs or specifics.

Russel Ray · 05-13-2011, 02:15 AM

The only time I find more than 100 amps is in the McMansions of about 5,000 SF or more.

After Enron manipulated the energy markets here in 2000-2001, almost everyone who had electric appliances switched them over to gas, including me.

**Rick Bunzel** · 05-15-2011, 07:37 PM

When I was a newer inspector I once questioned the Amperage of a panel in a newer home and was quietly schooled by a licensed electrician who was also a part-time building inspector. The net-net is that if the local building authority allows it and their are no visible over current issues in the panel, why would you call it out? Would a home inspector have more knowledge than a licensed electrician who pulled the permit or the building inspector who approved the installation? You have to go with your gut, if it smells and looks like a rotten fish, it probably is.....

As I gained more experience I did identify sketchy electrical panel installations but most were retrofits to older homes.

//Rick

**Joe R. Maxwell** · 05-16-2011, 04:25 AM

Originally Posted by Rick Bunzel

When I was a newer inspector I once questioned the Amperage of a panel in a newer home and was quietly schooled by a licensed electrician who was also a part-time building inspector. The net-net is that if the local building authority allows it and their are no visible over current issues in the panel, why would you call it out? Would a home inspector have more knowledge than a licensed electrician who pulled the permit or the building inspector who approved the installation? You have to go with your gut, if it smells and looks like a rotten fish, it probably is.....

As I gained more experience I did identify sketchy electrical panel installations but most were retrofits to older homes.

//Rick

Probably nothing wrong with the 100-amp service.

Does a home inspect have more knowledge than a licensed electrician? Maybe. Why are there so many electrical issues in new homes if the electricians are so knowledgeable?

Also, knowledgable building inspectors. Where do they get their training if they have been trained? Some are good, some are bad, some are the Mayor's brother, father-in-law.

If its wrong, its wrong and does not matter who did it or who approved it.

**Don Horn** · 05-16-2011, 06:18 AM

With all the gas appliances, 100 amp or 125 amp service would be common in this area. The minimum is 100 amp, at present.

Rick Passero · 05-16-2011, 07:59 AM

Most homes in my area , southern ontario, have 100 amp services, including new builds as of today, unless the home is heated by electric or is over 3000 sq. ft. I see no need to write it up unless it is abnormal for your area.

Rick

**TR Platt** · 05-16-2011, 04:59 PM

For those of us under the International Codes, the service should be sized in accordance with E3602.2.

There is nothing requiring anything greater than 100A, unless the load calcs indicate more amperage is required or you have a local ordinance setting a minimum standard.

In my experience 200A is just routinely installed.

So, unless you are going to calc the house and demonstrate otherwise, I don't think it is noteworthy given the gas appliances and (I assume) absence of other large-amperage devices.

**Ken Amelin** · 05-16-2011, 06:02 PM

Even if someone does a calc, it involves diversity factors that are mostly empirical.

Not that I'm against calculations for determining a service size requirement, but in my experience, I've never inspected a property with a 100 amp service where the 100 amp main breaker is smoking hot and ready to trip due to overload.

Has anyone had any experience with nuisance tripping of 100 amp main breakers?

**TR Platt** · 05-17-2011, 03:46 AM

While I do agree, the calculation is the minimum standard. If the service does not meet the minimum standard, then it would be worth noting.

My old house was 100A for 2000+sf with electric dryer, electric oven/range and a swimming pool pump. Window A/C units were used in the summer. We never had the main breaker trip.