Is There a Minimum Disconnect Requirement for a Sub-Panel

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Hi ... I'm the original poster. I've been in the field all day, and just got back, and there seems to be some confusion about the configuration. I'll try to clear it up.

The home is 2-story, Sq.Ft.=3,100, Year Built=2007.

There is a main service panel mounted on an exterior wall of the home. This panel has the following breakers (see pictures):

Ckt# Description
1/3. 2-Pole 125 Amp Main.
2/4. 2-Pole 40 Amp A/C Condenser.
5/7. 2-Pole 40 Amp Sub-Panel.
6/8. 2-Pole 30 Amp Dryer.
10. 1-Pole 20 Amp Washer.
12. 1-Pole 20 Amp Gas Dryer.
13. 1-Pole 20 Amp AFCI Smoke Alarm.
14. 1-Pole 20 Amp Lawn Sprinkler.

The Sub-Panel is mounted on an interior wall of a built-in (attached) garage, and provides all of the circuits for the following:

Ckt# Description
1. 1-Pole 20 Amp Disposal.
2. 1-Pole 15 Amp Hall Lighting.
3. 1-Pole 20 Amp Dishwasher.
4. 1-Pole 15 Amp Bedroom #4 AFCI.
5. 1-Pole 20 Amp Gas Furnace.
6. 1-Pole 15 Amp Master Bedroom AFCI.
7. 1-Pole 20 Amp Microwave.
8. 1-Pole 15 Amp Bedrooms #2 & #3 AFCI.
9. 1-Pole 20 Amp Kitchen GFCI #1.
11. 1-Pole 20 Amp Bathroom GFCI.
13. 1-Pole 20 Amp Dining Room Lighting.
15. 1-Pole 20 Amp Water Softener.
17. 1-Pole 20 Amp Refrigerator.
19. 1-Pole 20 Amp Kitchen GFCI #2.
21. 1-Pole 20 Amp Game Room Lighting.
23. 1-Pole 20 Amp Garage GFCI.
25. 1-Pole 15 Amp Lighting & Plugs.
27. 1-Pole 15 Amp Lighting, Utility, Garage.
29. 1-Pole 15 Amp Living Room.
31. 1-Pole 15 Amp Family Room.

As stated earlier, the garage sub-panel is fed by a 40 Amp breaker on the exterior service panel. The neutrals & grounds are isolated from each other in this panel ... that's why I referred to it as "separately derived". If I've misused this term, I apologize. I've also attached photos of the panels with the covers off. The sub-panel feeder conductor is multi-strand AL. I was unable to determine the size (I'm not quite experienced enough to ID these by sight). I've attached a close-up of the conductor. Perhaps you can tell.

To Re-state:
- I was wondering if the 40-Amp Sub-Panel disconnect is large enough as I usually see Sub-Panel disconnects rated at 60 Amps.
- Is there any code being violated here? I had thought that 225.39(D) would address the issue, but I'm not sure.

Anyway, I hope all of this helps you to help me.

Thanks again.

Peter Sullivan
National Property Inspections
Round Rock, TX
 
pjsullivan said:
- I was wondering if the 40-Amp Sub-Panel disconnect is large enough as I usually see Sub-Panel disconnects rated at 60 Amps.
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Pete, first, my apologies for my first response. You obviously are more concerned with doing a good job than most H.I's I've butted heads with. :smile:

Second, what size and material are the conductors on that breaker? They appear to be #6 or 8 aluminum.
 
Larry: No need to apologize. I'm just glad you're taking the time to help.

The feeder conductors are aluminum. There were no accessible markings that would indicate their size though, but I'm pretty sure they are at least #6, and possibly #4.

Thanks.
 
I believe it would be impossible to do a load calculation without more info, however, if the panel has been there for a year I would not think the feeder size is an isue. You can put an amp meter on it but again that may not give an accurate picture.

Do the feeders look heated(mis-colored) at all. From looking at the loads you stated I would be surprised if the feeder didn't hold. I would have put a 60 amp circuit but 40 may very well be adequate.
 
That feeder circuit looks really small to me considering the circuits it powers.
How many people live in this home?

steve
 
He should have used a larger breaker and that wire looks to be atleast #6 if so i do not know why he used a 40 perhaps it was the truck answer.As to if its enough depends on who lives there.If you were doing this inspection for a buyer i would be concerned.Would put on report what you found and suggest the EC deals with this as it is easy fix if #6.Also as you know this is sloppy work in the panels,and likely that was done by there best man so no telling what rest of job looked like.Your concern on this find is justified.
 
pjsullivan said:
Larry: No need to apologize. I'm just glad you're taking the time to help.

The feeder conductors are aluminum. There were no accessible markings that would indicate their size though, but I'm pretty sure they are at least #6, and possibly #4.

Thanks.
Click to expand...
Is there ANY possibility that the 125A "main" is feeding the "sub-panel"? That would make good sense. If you turn the 40A off, what really dies?

By ANY chance does this home have a generator (or plans for one?) with it's panel fed by the 40A?
 
GeorgeB said:
Is there ANY possibility that the 125A "main" is feeding the "sub-panel"? That would make good sense. If you turn the 40A off, what really dies?

By ANY chance does this home have a generator (or plans for one?) with it's panel fed by the 40A?
Click to expand...

Yes, the 125A "main" is feeding the "sub-panel". If the 40A is turned off, only the "sub-panel" dies.

No plans for a generator.

3 People & 2 cats live in the home (answer to earlier question).

Thanks ...

Peter Sullivan
National Property Inspections
Round Rock, TX
 
My thinking says that with a normal family with 2 teens that we would be tripping that breaker.Kitchen alone could easily use half.Get the mr coffee going ,toaster,microwave,dish washer and then flip on the pig.Add that to the computors,tv,washer hmmmm.They just been lucky
 
The tracer is there (left side). It is edge on, so it's not very obvious. I can barely see it my original full-size photo, so it's not surprising that it's not visible in the reduced size photo.
 
Load Calculation

Load Calculation

Well ... since all of you have invested so much time in this, I decided to bite the bullet and attempt to perform a load calc for the sub-panel. Since I take photos of all the data plates of the home's equipment & appliances, I had the data I needed. Here's what I came up with:

3,156 sq.ft. x 3 9,468 VA
2 Small Appliance Circuits 3,000 VA
Total Gen.Lgt & Sm.App. Load 12,468 VA
Gen.Lgh Demand (3,000 + 35%) 6,314 VA

Refrigerator 1,344 VA
Dishwasher 1,188 VA
Disposal 804 VA
Microwave 1,580 VA
Garage Door Operator 720 VA
Gas Furnace Blower 800 VA
Total Appliance Load 6,346 VA
Appliance Demand Load (75%) 4,827 VA

Service Demand 11,141 VA

Demand Load 46 A
Neutral Demand 46 A
Min. Feeder size 2
Min. Neutral size 4
Equipment Grounding Conductor 6
Composition Aluminium

Did I do this correctly?
 
Dennis:
Can you please be more specific about what does not look right about the calc?

I agree with the feeder size comment ... the spreadsheet indicated the conductor sizes based on a minimum 100A service disconnect. I neglected to make the adjustment for the 46A sub-feed. It should be #4 Aluminum.

Peter.
 
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