90 or 180 Amps?

[jweinberg]

Originally Posted by eschwartz

OK,
I think it is clear that there are two, separate 240v 90 amp breakers, right?

So that means that there is a 180amp capacity.

But if you had an appliance that was rated at....100amps (big big stove), you would be in trouble.

I vote for two separate 90amp services...

Great thread.

Ed

So how do we feel about this description?

Size of Electrical Service:
•120/240 Volt Main Service - Service Size: 180 Amp

Main Disconnect:
•Main Service Rating: Service limited by two 90 Amp service breakers installed in parallel.

[Russel Ray]

Originally Posted by jweinberg

So how do we feel about this description?

Size of Electrical Service:
•120/240 Volt Main Service - Service Size: 180 Amp

Main Disconnect:
•Main Service Rating: Service limited by two 90 Amp service breakers installed in parallel.

I don't know. I'm having trouble with a few words: so, do, we, by, in.

[eschwartz]

Russell,
You say that it is a 90amp service because any single load on it that is greater than 90amps would overload the main panel. Right? That makes sense too.
How about this: "180amp service with a limit of 90 amps for any single breaker"

[Russel Ray]

I'm still not happy with the 180 amps, though. Adding two 90-amp breakers together to get 180 amps doesn't sit right with me.

Let's take a modern 42-breaker panel. Let's wire it with 3/0 for a maximum of 225 amps, just like this one, and give it a meter with a maximum of 200 amps, just like this one. Now, though, instead of two "main" breakers, let's give it 42 "main" breakers, all rated at 20 amps. Would you add up those 42 "main" breakers" to get 840 amp service? I wouldn't. On the other hand, I don't necessarily like calling it 20 amp service, although I think that's what it is. I don't think there is a checkbox solution, so I'm sticking with my 90 amps. However, I would modify my standard language to state something like "Meter service capacity is 200 amps while wiring service capacity is 225 amps. However, service capacity appeared to be limited to 90 amps due to the non-standard wiring of two 90-amp circuit breakers." Then I would add my standard less-than-100-amps caution regarding insurance.

[Paul W. Abernathy]

We know you are loaded with the BUCKS Ray Ray.......so I am sure you would upgrade fella...

[ddelaney]

Actually, the rating of any service is only the individual rating of the breaker (the actual #), not the wire size. The wire, when installed correctly, should be sized properly so that the overall load does not exceed 80%.

However, as home inspectors, we just need to know that the breaker rating is the service size. The thermal/mechanical overload limit in a 2 pole breaker is sized to trip when the total load exceeds the individual rating marked on the breaker. So, in theory, a 90 amp 2 pole breaker shouldn't be able to exceed a total of 90 amps.

Hope this helps.

[Joey D'Adamo]

Originally Posted by rray

I'm still not happy with the 180 amps, though. Adding two 90-amp breakers together to get 180 amps doesn't sit right with me.

Let's take a modern 42-breaker panel. Let's wire it with 3/0 for a maximum of 225 amps, just like this one, and give it a meter with a maximum of 200 amps, just like this one. Now, though, instead of two "main" breakers, let's give it 42 "main" breakers, all rated at 20 amps. Would you add up those 42 "main" breakers" to get 840 amp service? I wouldn't. On the other hand, I don't necessarily like calling it 20 amp service, although I think that's what it is. I don't think there is a checkbox solution, so I'm sticking with my 90 amps. However, I would modify my standard language to state something like "Meter service capacity is 200 amps while wiring service capacity is 225 amps. However, service capacity appeared to be limited to 90 amps due to the non-standard wiring of two 90-amp circuit breakers." Then I would add my standard less-than-100-amps caution regarding insurance.

I see what you're saying and it probably holds in this case. However, those two 90s do not have an OCPD upstream of them, which would allow them both to draw 90 amps @ 240v each. In your example 200A panel filled with breakers summing well over 800A, that 800A could never be drawn. So there is a difference. The 180A @ 240V is possible, whereas the 800A example provided could never actually happen without tripping the main.

[Robert J. OConnor]

Originally Posted by eschwartz

I vote for two separate 90amp services...

Originally Posted by pabernathy

Correct...Ed

I don't agree. There is only one service to the house ... with a 200A rated meter, 225A rated SE feeders, and a single service panel with 2-90A twined main breakers.

Originally Posted by rray

Let's take a modern 42-breaker panel ... Now, though, instead of two "main" breakers, let's give it 42 "main" breakers, all rated at 20 amps. Would you add up those 42 "main" breakers" to get 840 amp service?

Although that would be a defect with more than 6 main switches (actually 2 main switches, since it would then be a "lighting and appliance" panel per NEC 408.16), in that case you wouldn't add up the breakers since it wouldn't be limiting the service capacity. It's also not likely that all would draw close to the max ... so a load calc would be necessary to fill in the last piece of the service capacity question.

But in this case adding up the service panels breakers doesn't exceed the meter/feeders ... it actually limits the capacity, which is why my call is 180A capacity.

Now if there was a single 180A main breaker in the panel with the 2-90A twin breakers to sub-panels (not service panels), what would be the service capacity ... obviously 180A as that limits the capacity ...

[Paul W. Abernathy]

Incorrect...my agreeable point is (2) 90 Amp sub-panels based on the rating of the OCPD...I do not get into telling the client what the system COULD be if they wish to upgrade it or change it....My job is to tell them what they have RIGHT NOW.....and I see (2) 90 Amp panels with a combined service rating of 180 Amps.....

This is also not a normal set up....My report would have 180A Service with (2) 90A sub panels.....sure I could say you have 180A service....BUT based on this set up I am not going to list it as such....You are FREE to do what you wish.....from experience I am not going to list it that way....maybe it is just me.

As far as I am concerned the client has the ability to have 90A from either location...yes, it is 180A capacity BUT I am more concerned with them overloading a 90 A panel....that is what I am saying.

[Russel Ray]

Originally Posted by pabernathy

As far as I am concerned the client has the ability to have 90A from either location...yes, it is 180A capacity BUT I am more concerned with them overloading a 90 A panel....that is what I am saying.

I think that's what I've been saying, too.

[Paul W. Abernathy]

I hear ya Ray Ray...but dont take my word for it..I don't know JACK.....

[Robert J. OConnor]

Originally Posted by pabernathy

...yes, it is 180A capacity ...

We agree there ...

Originally Posted by pabernathy

...BUT I am more concerned with them overloading a 90 A panel....

I would agree if one of the sub-panels had a very significant load compared to the capacity of that sub-panel, but the loads are not known and that concern wasn't expressed ... so I'm just not seeing that.

Even then it would likely just be an issue with shifting some of the load/circuits from the older sub-panel (which does appear to be a little packed) over to the newer sub-panel. But that wouldn't affect the 180A service capacity.

[jweinberg]

Originally Posted by pabernathy

As far as I am concerned the client has the ability to have 90A from either location...yes, it is 180A capacity BUT I am more concerned with them overloading a 90 A panel....that is what I am saying.

See below

Originally Posted by rray

I think that's what I've been saying, too.

See below

Originally Posted by roconnor

Even then it would likely just be an issue with shifting some of the load/circuits from the older sub-panel (which does appear to be a little packed) over to the newer sub-panel. But that wouldn't affect the 180A service capacity.

It does appear to be a little packed. But keep in mind the following:

The bottom 4 breaker on the older subpanel are in the off position and two of those four don't even have condutors attached to them.

Also, BOTH subpanels had deadfront labels that indicated 'spare' on at least a couple of breakers. And I KNOW we all believe that all deadfront markings are properly labeled...

I don't feel there is a load to sub panel capacity issue on either subpanel NOW! I bet there was one before the second/newer subpanel was added though.

[Robert J. OConnor]

Originally Posted by jweinberg

I don't feel there is a load to sub panel capacity issue on either subpanel NOW! I bet there was one before the second/newer subpanel was added though.

That would be my guess too given the info you provided and the presence of a newer sub-panel ...