Is There a Minimum Disconnect Requirement for a Sub-Panel

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pjsullivan

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Round Rock, TX
First, let me say that I'm a home inspector in Texas, and although I can spot most problems with residential wiring, once in awhile I run across something that is a head-scratcher (at least for me).

Here's the configuration:

1. Exterior panel feeds a sub-panel (separately derived) located in attached garage.
2. Disconnect for said sub-panel is only 40 amps (see pictures). I rarely see anything less than 60 amps for these. Is this a problem? If so, what code(s) is/are being violated?

Thanks ...

Peter Sullivan
National Property Inspections
Round Rock, TX
TREC #6399
 
If the breaker is sized to protect the conductors, and doesn't trip, the only argument left is load calcs. Have you done them? Do you know how or why they're done?

However, since we're hard-core here, and don't equate 'home' inspector with 'electrical' inspector, you tell us what NEC section you see as being violated. Have an NEC?

You are qualified to inspect electrical systems, aren't you?
 
Well, the home is <1 year old, and the homeowner has not had a problem with the lights going out. And, no, I haven't performed a load calc ... I just don't have the time. And yes, I have a 2005 NEC. I was leaning toward 229.34(D), but I'm just not that sure. What do you think?
 
pjsullivan said:
Well, the home is <1 year old, and the homeowner has not had a problem with the lights going out. And, no, I haven't performed a load calc ... I just don't have the time. And yes, I have a 2005 NEC. I was leaning toward 229.34(D), but I'm just not that sure. What do you think?
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Could you have printed a typo? I don't have a 229.34(D) in my '05. :confused:
 
I believe your intent was to cite 225.39(D). And I agree that the minimum size should have been 60 amps. But what is to be done about the situation is an entirely different matter. May I ask if this house is being sold, and if that is why you are involved in the project? My suggestion is that you include it in your list of observations as a "potential issue," and include as well a recommendation that an electrician be brought into the picture to deal with any corrective actions that may be appropriate. The fact that a new installation would fail inspection for this same issue does not necessarily mean that the existing condition will be required to be upgraded, even if it is only a year old. Much depends on the rules set up, in the local area, with regard to existing conditions.
 
charlie b:

Thanks for your reply.

I performed the inspection for the homeowner for his 1-year builder's warranty inspection. I inspect the home, prepare a report, and the homeowner gives the report to his builder, who then addresses the issues I find.

Anyway, I did exactly as you specified. I simply questioned the 40 amp breaker as a potential issue, and recommended a qualified electrician evaluate and determine a course of corrective action if required.

Thanks again for the help.

Peter.
 
From that panel shedule a 2 pole 40 is bit low.Did you open the panels up and varify size of wires and that the 40 is actually supplying this panel ?Seems strange to put in large main and then just use 40.
 
225.39(D) applies to the rating of the DISCONNECT, it says nothing about the ampacity of the feeder. The feeder need only be sized for the load to be served. There are many garages, sheds, etc. fed with 30-amp feeders. The disconnect must be rated for at least 60-amps, this does not mean that you need to install a 60-amp feeder to serve a 30-amp calculated load. I am sorry that as a home inspector you do not "have time" to do a load calculation on the garage, but unless you do you have no idea whether the feeder is adequate or not. The feeder will be protected at the proper ampacity by the breaker in the distribution panel, the disconnect is just a switch to disconnect the power at the building.
 
haskindm said:
225.39(D) applies to the rating of the DISCONNECT, it says nothing about the ampacity of the feeder. The feeder need only be sized for the load to be served. There are many garages, sheds, etc. fed with 30-amp feeders. The disconnect must be rated for at least 60-amps, this does not mean that you need to install a 60-amp feeder to serve a 30-amp calculated load.
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I agree, but as it is it has a 40 amp disconnecting means.
 
iwire said:
I agree, but as it is it has a 40 amp disconnecting means.
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I agree that it is right to agree ,...the easy solution,.. back feed a 60 amp breaker at the sub panel.
 
1. Exterior panel feeds a sub-panel (separately derived) located in attached garage.
2. Disconnect for said sub-panel is only 40 amps (see pictures). I rarely see anything less than 60 amps for these. Is this a problem? If so, what code(s) is/are being violated?
Click to expand...

Am I missing something? The OP stated this is an attached garage, so Article 225 would not apply.

Chris
 
pjsullivan said:
First, let me say that I'm a home inspector in Texas, and although I can spot most problems with residential wiring, once in awhile I run across something that is a head-scratcher (at least for me).

Here's the configuration:

1. Exterior panel feeds a sub-panel (separately derived) located in attached garage.
2. Disconnect for said sub-panel is only 40 amps (see pictures). I rarely see anything less than 60 amps for these. Is this a problem? If so, what code(s) is/are being violated?

Thanks ...

Peter Sullivan
National Property Inspections
Round Rock, TX
TREC #6399
Click to expand...
How do you figure it is 'seperately derived"? That would be very unusual for this kind of situation.
 
raider1 said:
Am I missing something? The OP stated this is an attached garage, so Article 225 would not apply.

Chris
Click to expand...
1. Exterior panel feeds a sub-panel (separately derived) located in attached garage.
Click to expand...

That would imply the circuit is outside, making it subject to article 225.

Although the way 225.1 is written, you could argue either way.
 
petersonra said:
How do you figure it is 'seperately derived"? That would be very unusual for this kind of situation.
Click to expand...
It is an imprecise use of terms. I'm sure the OP did not intend to confuse this with an SDS.
 
Bob,
Yes the exterior panel would make the feeder subject to the rules in 225, but since the feeder does not feed a second building, there would be no requirement for a disconnect at the panel. Part II of Article would not apply.
 
iwire said:
Now Chris wants to confuse us with facts. :grin:
Click to expand...

As a wise man once said (Homer Simpson) "Facts are meaningless, you could use facts to prove anything that's remotely true!":D

Chris
 
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