Originally Posted By: osmith This post was automatically imported from our archived forum.
Hey guys, I need someone to share their infinite wisdom with me. The last two houses I have inspected both had two panels in different locations in the house. One panel was normal with two wires and a nuetral coming into the box as well as a main breaker . The other panel did not appear to have two main wires coming in nor did they have a main breaker. My question is two fold:
1. How should I rate the amps in this case if for instance the regular panel has 100 amp service and the other has no visible main?
2. What is the purpose in doing it this way to begin with?
Originally Posted By: William Dorsey This post was automatically imported from our archived forum.
I agree with the first respondent the second panel is most likely a sub panel even if it is older than the first panel. Sub panels are installed for a variety of reasons, but typically either to expand the number of possible circuits when the main panel has few available breaker slots or to make it simpler to wire the structure. A sub panel does not need to have a main breaker, but it does need to be fed with 4 wire service from the main panel, and the neutral wires must be connected to a separate buss isolated from ground unlike the main panel where neutrals and grounds are connected to the same buss.
Anytime I install a sub panel, I feed it from a breaker in the main panel sized appropriate to the nominal load to be fed by the sub panel. As far as the sub panel being older, that isn't unusual. I have worked on many older homes where an older main panel was turned into a sub panel in a garage when a new main panel was installed. One recent place had a relatively new 125 amp Square D main panel in the basement which in turn fed an older 100 amp panel in the garage and the original 60 amp fuse box which was now in the barn. Some folks don't like to throw anything out if it can still be used. While frugal, I don't recommend reusing old electrical equipment. Some things don't get better with age, and electrical equipment is one of them.
Originally Posted By: osmith This post was automatically imported from our archived forum.
Thanks Jeff and William!
Of course I have one more questions now:
William, in the example you gave with the two panels that were fed from the main panel; would you say that the home has 100 Amps of service, 125 Amps of service or 160 Amps?
Originally Posted By: William Dorsey This post was automatically imported from our archived forum.
Oscar,
It has 125 Amp service. The service is limited by the main breaker in the main panel if all of the other panels are fed from this panel without doing something illegal like double stabbing in the sub panel feeds to the main feed into the main panel.
Now you could theoretically interconnect loaded panels to the point that there would be the potential demand for more power than 125 amp, but the main breaker would trip once 125 amp was exceeded so 125 amp is all you will be able to deliver.
Now think about the implications of bypassing the main disconnect by double stabbing in the feed to one or more sub panels. If you were to do this with say two 125 amp panels over wire rated for 125 amp through a meter base rated at 125 amp, you won't have to think long before you can begin to imagine the potential for burned wiring.