Denis,
There is no basis that I would offer as professional advice to another appraiser. I can tell you that adequate sizing of electrical service equipment is determined by a calculation promulgated by the NEC. I don't recommend appraisers apply it without proper guidance.
I do not recommend that appraisers become electrical engineers for the purpose of valuation. If a particular assignment required the appraiser to eliminate any assumption of adequacy, I would recommend an inspection by a qualified professional.
(my bold)
And I think what I bolded is what FHA expects... and it expects it with the understanding that an appraiser is not an electrical engineer and will not make the calculation based on the NEC standards.
So, the true threshold is not "is the service adequate" but rather, "is it reasonable to require an inspection to determine
if the service is adequate"?
That is certainly a standard that an appraiser can meet using his/her experience, common sense, and discussing his/her rationale in the report so the intended use can make a judgment if it is reasonable or can decide it isn't reasonable, and not require any additional inspections.
I'm a simple Marine on the front line. I come up on something which looks like a mine to me. I'm not going to try to defuse it. I'm going to mark it and alert my command what I found, where it is, what I think it is, and recommend they get someone to look at it.
I don't have to make the determination that it is a mine or not.
I just have to use common sense in my determination of advising my command that there is a potential issue.
FHA expects a similar level of common sense in a lot less serious situation.