I have a little prb here. It's a 3 family bldg. There are 4 meters (including the PLP meter) outside of the bldg. There are no place to put the service disconnect on the inside other than the 1FL tenant car garage, the common hallway, or the basement boiler room directly below it.

(1)Will it be a prb to put it in the boiler room? It's approximately 12ft away from the meters.

In the NEC, 230.72 (C) - it states: Access to occupants. In a multiple-occupancy building, each occupant shall have access to his or her disconnecting means.

(2)Does it refers to SERVICE DISCONNECT?
(3)If 230.72 (C) refers to service disconnect, does that mean we cannot put in the the 1FL car garage?

Another prb, I was told in this case, with 4 meters, and a 2" pipe ran from the meter to the trough, then from the trough to the main disconnect for all 3 apts and common area with 4 sets of #6 THNN is a violation? Is that right? Each apt is using a 50 Amps Main breaker.

PLEASE HELP!

Every tenant needs to have access to his 50 amp breaker.

Your main disonnect would usually be immediately after the meter, and before the trough- assuming that the apartments are not individually metered.

A more common install would have the service conductors exit the riser directly into the trough. In the trough, the service would be split to a meter for each address- with a disconnect just after each of those meters.
You are allowed to use this arrangement- one without a "main" disconnect- where there are no more than six meters.

I really think you need to talk to both your town hall, and your power company. It sounds as if this was a rather half-baked conversion, and there may be other issues you will need to address as well.

Why not put the disconnects right below the meters? They are accessible right? You can get a single enclosure for all four meters and mains, a lot easier... all of the NEMA3 ones I have seen in the last few years have provision for locks on the covers to the breakers too.


Anyway, IMO 50a is a little light for an Apt. Definately too light for condo units. What if any ever need a 220/240 for anything?

Also running all of the services in one 2" may not be legal for your POCO after the meter section, not to mention derating conductors to 50%, per Table 310.15(B)(2)(a).

Take a look at 230.79(D) and see if I read this right. We need 60a rated breakers if these breakers you are talking about are Service Disconnects.

You're right George, no less than 60A.

Even on small apt's I do 80A.

You guys are right. It should be minimum of 60 Amps. Thank you. As for Code - 310.15(B)(2)(a), for a 4 meters which carries 4 sets of 3 wires, with total of 8 current conductors in a 2" pipe (over 24"), if #4 THNN is used, does that mean it will meet the requirement??

These are single phase 120/240v meters. Does the neutral consider as current carrying conductor?

[This message has been edited by rknikko (edited 01-25-2006).]

310.15(B)(4)(a) A neutral conductor that carries only the unbalanced current from other conductors of the same circuit shall not be required to be counted when applying the provisions of 310.15(B)(2)(a).

"if #4 THNN is used, does that mean it will meet the requirement??"

Yes

"if #4 THNN is used, does that mean it will meet the requirement??"

Maybe not....

12 conductors (current carrying) of (I am assuming) ThhN to panels with load diversity. (i.e. un-equal loads on each phase.) 95A @ 50%=47.5A

If you call the neutrals non-current carrying 95A @ 70% = 66.5A (see 220.22) We don't know what the loads are do we? (See Annex D for examples)

This is not including calculations for ambient temp. (A boiler room was mentioned.) Or 110.14(C)(1) provided an Inspector carries a calculator. Or if the AHJ allows feeders or branches of seperate metering in the same conduit or enclosure.

As I dont think is 310.15(B)(6) is applicable with all in one 2" conduit.
I know commentary is not code, but I don't see 310.15(B)(6) as an exception.

Why not 4 cables or conduits? Then #4 is fine... You could do 100A!

I think it is clear you only count the phases, the neutrals will only carry the unbalanced current. That puts you in the 70% derating column. That will give you the 60+ amps required for 60a breakers and not kick the 310.15(B)(6) tar baby.
I would certainly be troubled if someone wanted to say this was good for 100a but the expected diversity would allow me to sleep well at 60a per.

So guys, which one is it? Neutral counts as a current carrying conductor OR not? Which derating to use? 70% or 50%???

We dealing with a single phase 120/240V now.

In single phase, the neutral only carries the unbalanced current. If you are seeing current on the neutral, the current on one of the phases is reduced that much.

...and your answer to the question is....

Don't count the neutral in the derating.