underamped subpanel??

Hey everyone,

I came across a subpanel with a 90 amp service from the main panel outside. Included in the subpanel is the 40 amp breaker for the range along with everything else other than the HVAC system breakers. An electrician friend of mine told me they prefer to put the range breaker in the main panel outside and then to install a 100 amp service to the subpanel.

Any input on how to address this aparent inadequacy in a report?

P.S. I know to include a statement recommending a licensed electrician further evaluate, but I also don’t want to raise red flags where none are due.


To determine if the service is properly sized a demand load calculation would be performed.

The smallest service allowed to a dwelling today is 100 amps.

Hi Will,

Jim is correct about the only way to know is by doing a load calc, however you stated that there is a “main” panel feeding the interior “sub” and this panel also feeds the AC, question is what size is the “main” service?? in all likelyhood this is just fine, in fact it sounds an awful lot like this is a manufactured home (mobile home) as that is the way they are commonly wired.



Thank you gentlemen. That’s some good info. The main panel has a supply of 200 amps. Although this situation may exist in manuf. homes, it seemed to me that my client will experience problems with such a system. My report comment is as follows. I’d appreciate your input.

Service to the sub panel is 90 amps. This appears to
be an underrated supply for items such as the range, the dryer, the water heater, and the
other circuits to be in the same panel. This may cause an excessive amount of breaker
overload while multiple circuits are being used. It is recommended that a licensed electrician
evaluate and repair/replace as needed.

How do you know this?
What condition did you find at the time of inspection to support this?
Voltage drop, hot breaker, blinking lights?
You are going to cost someone a service call and likely get in an argument with several people. On what grounds?

On the surface it does not sound improper or undersized in any manner, and is a very common installation in both manufactured homes and “stick built” homes in many areas.

Remember, you can look just as bad making a call that something is incorrect that isn’t, as you can calling something correct that isn’t.

Ditto. Without more information, you might be better off leaving this one alone.

He said that everything was in the sub panel except the hvac…

I would bet that it would be found incorrect by 20-40 amps if a load calc was done on an average size home and even worse if its more than 2500sf.

I guess I’d rather address an issue that may be a concern to my client in the future. This is why I hoped to gain some useful information from the veterans out there…not some stupid attitude from someone who has to tear others down to feel better about himself.

Thank you to all those who contributed constructively. You are greatly appreciated!

I don’t ever want to feel gunshy of asking an inteligent question. I’d like to use this resource as often as possible to ever increase my understanding in this field.

Will, I’m looking real hard in this thread to find something that made you say that and I just don’t see it ???

Was it David Anderson’s post? That post should not offend you, its good factual information. David is the source of some very good info on here, I recommend you read all of his posts about HVAC too.

Don’t read anything extra into posts on here, some are just trolling for an argument but don’t make something out of a simple strong opinion.

hope this helps!

by the way, your sample writeup is just fine for that issue you discovered.

Thanks Bruce. You’re absolutely right. I look forward to spending the time getting the valuable info out there. I actually had someone leave a very nasty comment on my personal webpage about my electrical inspection ability and was just irked. I’ll keep it professional. Thanks again for your encouragement.

I was very short on time yesterday, but I thought your question warranted a reply before you finished your report, or whatever. Sorry if my shortness was constrewed as being a smart *****.

I agree. I always ask questions when needed. If we don’t have the answers, consider them next time. If you really screwed up, go back. No one will fault you for being wrong and trying to correct it.

I try to ask things that we as HI’s can determine without getting off tract, doing things outside the SOP. “Analysis” of any component is not our job (if you elect not to do so). When I call in another “expert” I have a list of things for them to do, and why they should be done. This can’t always be done, but you should have the needed information to support your call (something that is actually happening). Something that is wrong.

The main point is that calling in another contractor without something substantial to base the call on will get you in arguments, and make you look bad (substantiated or not) to many people in the process. Electrical Contractor, Seller, Listing Agent, Selling Agent, Client, Clients friends (potential referrals) etc.

I got a call one time from a client who hired two Electrical Contractors to fix a burnt HVAC breaker. She was pissed because both of them said I was FOS and there was nothing wrong. She wanted to know who was going to pay those service calls. I was a mile down the road so I swung by and pulled the breaker (which looked like a lump of charcoal in the back and handed it to her. She asked; Why didn’t they find that? “I’m sorry mam, but there are just some questions we can’t answer”!

I’d rather you find yourself on this side of the argument.
I try not to tell people “what to do”, but rather ask questions. There are too many things that must be assumed if you don’t have the facts. Not until I have the needed facts will I recommend you do something.

As for those PM’s, just hit the delete button!

p.s. Everyone that posted above, probably knows more about electrical than I do.
More “Experts” responded to you than that one backhanded PM!
Something you just have to get used to here.

Very well said and on the money, David.