2 unit Apartment and large house service questions

[dm9289]

I recently did some work at a couple of houses and I had a couple questions about their services.

House#1 2units - SE cable was Aluminum 4/0 (200 amp), after the dual meter socket it had 2/0 Aluminum (150amp) wire feeding 2 separate breaker boxes with main breakers of 150 Amps. I tried to read up on Service entrance rules and I could not find a way to make this OK.



House#2 - SE cable was Aluminum 4/0 (200 amp), after single meter socket it fed a splice box which mated incoming 200amp cable to a 100 amp SE cable and a 200amp SE cable, which fed a 200amp main breaker box and a 100 amp main breaker box. Is this condition OK?

Basically my main concern with both of these is that the breaker boxes combined can draw more current than the SE cable is cable of handling please straighten me out on this.

Thanks as always
Dave

 

[Davis9]

What is the calculated load on the units?

Take a look up on the pole at the #4AL wire feeding it.LOL

Tom

 

[dm9289]

I did not do a load calculation I was at the house reinstalling some bad landscape lighting. I figured the potentials would be the biggest concern.

 

[suemarkp]

Both of those installations could be code compliant. What matters is the overall calculated load. Both have the potential for overloading, so each electrician needs to do a load calculation if they add something which has a calculated value.

 

[iwire]

Basically my main concern with both of these is that the breaker boxes combined can draw more current than the SE cable is cable of handling please straighten me out on this.

You are right, the breakers could allow more current to pass then the SE cable is rated for.

This is directly allowed by 230.90(A) Exception 3.

That is why this ...

Both have the potential for overloading, so each electrician needs to do a load calculation if they add something which has a calculated value.

... is very important. If your adding loads to service like this you have to do load calcs or at least know what the current load is.

This happens in industrial and commercial as well, I work at one facility where they have a 1200 amp switchboard supplied by 1200 amps worth of conductors but the combined rating of the six breakers that serve as the disconnecting means total more than 3000 amps.

Truthfully the rule does make sense, here is an example I use a lot.

There are six 100 amp breakers 'protecting' the riser on this service. If I recall the service conductors are in the 200 - 250 amp range. And that was still a good deal larger than the calculated load needed. (A friend of mine did this service)

It would have served no purpose to require 600 amp service conductors for this service.

 

[dm9289]

So basically long as you can show the inspector the calculated load is below the rating of the SE cable you are OK. In the cases I seen it just concerned me if someone would throw in say a high draw device like a 80amp heat pump ( becoming very popular in my region) system what could happen.

Thank you all for your info
Dave

 

[iwire]

In the cases I seen it just concerned me if someone would throw in say a high draw device like a 80amp heat pump ( becoming very popular in my region) system what could happen.

Yes you got it, the installer has to pay attention.

In the service I posted a picture of the entire building uses gas for cooking and the dryer. If the landlord suddenly switched to all electric that riser would be in trouble.

 

[zappy]

To me if i had a 200 amp panel, I would want to be able to use at most 80% of it's capacity. Maybe one day I would like a shed in the back. I think future use should be considered, not just what the calc. load is at the moment. Just my 2 cents:smile:

 

[LarryFine]

To me if i had a 200 amp panel, I would want to be able to use at most 80% of it's capacity. Maybe one day I would like a shed in the back. I think future use should be considered, not just what the calc. load is at the moment. Just my 2 cents:smile:

That's certainly permitted to be considered, and should be discussed with the customer.