400 or 200 Amp Service

[skinnydip]

Have 2 - 200 amp main panels located in garage that are being fed by 4/0 Al conductors. Each panel is wired to the meter but am unable to look in the meter to see how it is done(double tapped or double lugged). Well under 200 amps needed for a 1400 sf house that has been upgraded from baseboard heat to heat pump.

One electrician has told me that it was a 400 amp service based on that information alone while another one told me it could be no higher than 200 amp service. 2nd electricians reason was that the downstream wiring had to be protected between the meter and the main panels. The second electrician made more sense to me so was going to have him do the work. Which sounds correct or is there more information needed to make the call?

The next problem I have, I want to install a disconnect (combination panel) at the meter, so that I can power down the breaker panels inside and run circuits from the outside meter panel. The electrician said they don't make a combination panel that is double lugged and said a special panel would have to be ordered which was ridiculously expensive. Do you know of a 200 amp combination panel that is double lugged? and preferably reasonably priced?

Thanks.

 

[Dennis Alwon]

It sounds like you have a 400 amp service. The larger meter base has double lugs on the load side of the meter. They also make a panel that has a 200 amp main and feed thru lugs.

 

[Smart $]

Doesn't matter whether it was double tapped or double lugged in meter base... either way, the conductors from meter to panels are considered service entrance conductor taps.

Under Code, your service is rated 400A because it is "branched" to two 200A main breakers.

 

[mirawho]

I think you are looking at this wrong. If you need circuits near the meter, why not just get a 400A panel. You can then install a couple of 200A breakers for your disconnects for the other load centers and take out the circuits you want at that panel. Why are you trying to do this through lugs? Try to make your wiring installations as simple as possible. The unfortunate things is that most of the large load centers are 3-phase. They do of course make single phase 400A panels but they are a few bucks. I would look on Ebay first as they always have guys selling used panels all they time in sorts of configurations.

 

[Smart $]

Being its an existing installation, I wouldn't even bother with adding anything between meter and panels. I'd just run any new circuits out of one of the panels. If he installs a meter load center combo ahead of the existing panels, the main bonding jumper and the grounding electrode system will have to change over to it and removed from the two existing panels.... just for a few breaker spaces that he likely already has in the existing panels. In the end just wasting money for relatively little convenience, and I'd bet at substantially more overall cost.

 

[GerryB]

Being its an existing installation, I wouldn't even bother with adding anything between meter and panels. I'd just run any new circuits out of one of the panels. If he installs a meter load center combo ahead of the existing panels, the main bonding jumper and the grounding electrode system will have to change over to it and removed from the two existing panels.... just for a few breaker spaces that he likely already has in the existing panels. In the end just wasting money for relatively little convenience, and I'd bet at substantially more overall cost.

Absolutely. Doesn't make sense to do it any other way. If I understand the poster he has a meter with no disconnect, therefore his panels must be pretty much back to back with the meter provision. If he had electric heat and got rid of it he also has plenty of circuits available.

 

[kwired]

Absolutely. Doesn't make sense to do it any other way. If I understand the poster he has a meter with no disconnect, therefore his panels must be pretty much back to back with the meter provision. If he had electric heat and got rid of it he also has plenty of circuits available.

Plenty of free circuit spaces - maybe. Plenty of VA capacity - most likely.

 

[skinnydip]

I also should add that the main breaker panels are Federal Pacific and I didn't really want to open that can of opinions but my opinion is that I would like to be able to replace the panels in the near future without having to get the utiity company or the inspector involved to do so. I wanted to phase the work and Phase 1 would be replacing the meter base with a means of disconnect to the interior panels for ease of future replacement, and be able to run circuits from outside panel. All of this is on a very tight budget. Even if I have a 400 amp service, does the code require 400amp meter pan or can I reduce the capacity since the house only needs 200amp service?

Also, I thought that since the 4/0 al service entrance was rated for 200 amp, that something would have to trip if the draw was ever over 200amp. If I had a 400 amp meter feeding it and one se shorted, what would provide protection to prevent fire?

Thanks for all your help so far

 

[ceb58]

I also should add that the main breaker panels are Federal Pacific and I didn't really want to open that can of opinions but my opinion is that I would like to be able to replace the panels in the near future without having to get the utiity company or the inspector involved to do so. I wanted to phase the work and Phase 1 would be replacing the meter base with a means of disconnect to the interior panels for ease of future replacement, and be able to run circuits from outside panel. All of this is on a very tight budget. Even if I have a 400 amp service, does the code require 400amp meter pan or can I reduce the capacity since the house only needs 200amp service?

Also, I thought that since the 4/0 al service entrance was rated for 200 amp, that something would have to trip if the draw was ever over 200amp. If I had a 400 amp meter feeding it and one se shorted, what would provide protection to prevent fire?

Thanks for all your help so far

If that is what you have in mind then replace the meter with a 400 amp meter combo with a 8/16 built in panel. It will come with 1- 200amp breaker and you must buy and install the 2nd 200 amp breaker along with the lugs for utility connection. This will give you outside circuits and give you the ability to change out the panels at a later date with out pulling the meter.

 

[kwired]

I also should add that the main breaker panels are Federal Pacific and I didn't really want to open that can of opinions but my opinion is that I would like to be able to replace the panels in the near future without having to get the utiity company or the inspector involved to do so. I wanted to phase the work and Phase 1 would be replacing the meter base with a means of disconnect to the interior panels for ease of future replacement, and be able to run circuits from outside panel. All of this is on a very tight budget. Even if I have a 400 amp service, does the code require 400amp meter pan or can I reduce the capacity since the house only needs 200amp service?

Also, I thought that since the 4/0 al service entrance was rated for 200 amp, that something would have to trip if the draw was ever over 200amp. If I had a 400 amp meter feeding it and one se shorted, what would provide protection to prevent fire?

Thanks for all your help so far

One thing about permitted overcurrent protection for services that doesn't quite make sense in some instances is that if you only have one service disconnecting means - overcurrent protection must match or be less then the service entrance conductor ampacity, but if you have multiple service disconnecting means (where permitted and in particular the two to six rule) then you only need to size any common supply conductor to those service disconnecting means to the calculated load. So with that you could have six 200 amp main breakers all supplied by a single 200 amp conductor if the load calculation is 200 or less, but supply the exact same load with a single 400 amp main breaker and now the supply conductors must have an ampacity of 400 amps

 

[Smart $]

One thing about permitted overcurrent protection for services that doesn't quite make sense in some instances is that if you only have one service disconnecting means - overcurrent protection must match or be less then the service entrance conductor ampacity, but if you have multiple service disconnecting means (where permitted and in particular the two to six rule) then you only need to size any common supply conductor to those service disconnecting means to the calculated load. So with that you could have six 200 amp main breakers all supplied by a single 200 amp conductor if the load calculation is 200 or less, but supply the exact same load with a single 400 amp main breaker and now the supply conductors must have an ampacity of 400 amps

Yeah, its not logical. I submitted a PI which would require the ampacity of a service entrance conductor to be not less than the largest rated OCPD supplied. I considered other measures but did not propose any that I thought would be considered too radical a change... :angel:

 

[shortcircuit2]

In the case of a single service disconnecting means the SE conductors must be sized to the breaker or fuse rating unless the load is less and then we can use the next size up rule for under 800amps.

In the case of multiple switches up to 6...the service ampacity is the size of the service entrance conductors that feed the up to 6 switches, not the added amperage rating of the switches.

So, 2-200amp switches doesn't equal 400amp capacity and 6-200amp switches doesn't equal 1200amp capacity.

IE: 2-200amp switches fed with 300amp rated SE conductors equals a 300amp service capacity and 6-200amp switches fed with 300amp rated SE conductors equals 300amp service capacity. Its up to the electrician to not overload the SE conductor ampacity in either situation.

 

[Smart $]

In the case of a single service disconnecting means the SE conductors must be sized to the breaker or fuse rating unless the load is less and then we can use the next size up rule for under 800amps.

In the case of multiple switches up to 6...the service ampacity is the size of the service entrance conductors that feed the up to 6 switches, not the added amperage rating of the switches.

So, 2-200amp switches doesn't equal 400amp capacity and 6-200amp switches doesn't equal 1200amp capacity.

IE: 2-200amp switches fed with 300amp rated SE conductors equals a 300amp service capacity and 6-200amp switches fed with 300amp rated SE conductors equals 300amp service capacity. Its up to the electrician to not overload the SE conductor ampacity in either situation.

The requirement is sound as long as it is used within the intent, but literal interpretation allows SE conductors to be unprotected. What if you only had a 100A calculated load and 2-200A service disconnecting means (SDM). You could technically run a 100A "main" SE conductor and a 50A tap to each SDM, assuming balanced loading of SDM's. What protects these SE conductors?

Existing Exception No. 3

Exception No. 3: Two to six circuit breakers or sets of fuses shall be permitted as the overcurrent device to provide the overload protection. The sum of the ratings of the circuit breakers or fuses shall be permitted to exceed the ampacity of the service conductors, provided the calculated load does not exceed the ampacity of the service conductors.​

Proposed Exception No. 3:

Exception No. 3: Two to six circuit breakers or sets of fuses shall be permitted as the overcurrent device to provide the overload protection. The sum of the ratings of the circuit breakers or fuses shall be permitted to exceed the ampacity of the service conductors, provided the ampacity of the service conductors is not less than the calculated load or any supplied overcurrent device rating, whichever is greater.​

The example given above under my proposed revision would require all SE conductors to have an ampacity not less than 200A.

 

[shortcircuit2]

The requirement is sound as long as it is used within the intent, but literal interpretation allows SE conductors to be unprotected. What if you only had a 100A calculated load and 2-200A service disconnecting means (SDM). You could technically run a 100A "main" SE conductor and a 50A tap to each SDM, assuming balanced loading of SDM's. What protects these SE conductors?

You couldn't drop a 50amp tap to a 200amp main? Each SE conductor tap to the each SDM would need to be sized on the 200amp rating.

 

[shortcircuit2]

Proposed Exception No. 3:

Exception No. 3: Two to six circuit breakers or sets of fuses shall be permitted as the overcurrent device to provide the overload protection. The sum of the ratings of the circuit breakers or fuses shall be permitted to exceed the ampacity of the service conductors, provided the ampacity of the service conductors is not less than the calculated load or any supplied overcurrent device rating, whichever is greater.​

The example given above under my proposed revision would require all SE conductors to have an ampacity not less than 200A.

I believe 230.90(A) already provides that restriction.

 

[Smart $]

You couldn't drop a 50amp tap to a 200amp main? Each SE conductor tap to the each SDM would need to be sized on the 200amp rating.

Okay. Got a little ahead of myself... but the SE conductor before tap off could be rated 100A under the current wording.

 

[shortcircuit2]

Okay. Got a little ahead of myself... but the SE conductor before tap off could be rated 100A under the current wording.

I believe 230.90(A) already provides that restriction.

 

[Smart $]

I believe 230.90(A) already provides that restriction.

I agree it is intended to... but Exception No. 3 is not worded explicit enough to say absolutely. After all it is an exception. If you look at service entrance conductor requirements for ampacity, it is based solely on calculated load, with no consideration for OCPD rating.

 

[growler]

If I understand the poster he has a meter with no disconnect, therefore his panels must be pretty much back to back with the meter provision.

Not really, it could be an older install. The code requireing a disconnect has not been there that long.

I know of an older house (out in the country) that has a 400 Amp service installed back in the 60s . They actually used CTs to meter the power with no disconnects.

 

[GerryB]

I also should add that the main breaker panels are Federal Pacific and I didn't really want to open that can of opinions but my opinion is that I would like to be able to replace the panels in the near future without having to get the utiity company or the inspector involved to do so. I wanted to phase the work and Phase 1 would be replacing the meter base with a means of disconnect to the interior panels for ease of future replacement, and be able to run circuits from outside panel. All of this is on a very tight budget. Even if I have a 400 amp service, does the code require 400amp meter pan or can I reduce the capacity since the house only needs 200amp service?

Also, I thought that since the 4/0 al service entrance was rated for 200 amp, that something would have to trip if the draw was ever over 200amp. If I had a 400 amp meter feeding it and one se shorted, what would provide protection to prevent fire?

Thanks for all your help so far

I don't know how the POCO works where you are but here in Ct. you (ie: the electrician) are allowed to change or work on your panel (say the main goes bad) without a permit. We would simply pull the meter. If the meter is locked like it is sometimes the POCO will unlock it for us, no permit required. I have a temporary gfi outlet with alligator clips to tap the meter if we need power or light. As far as whether or not you have a 400 amp service I would say if the meter socket is rated 400amps, (or320amps) and you have two sets of 4/0, one to each panel, you have a 400 amp service. Makes no difference what size wire the utility is providing, at least around here. They have their own guidelines. If you are on a tight budget get a price but a 400amp meter socket with 2 200amp breakers is going to be very expensive and now I would say you do need a permit because of the scope of the work.