Meter/Panel Combo question

[mccayry]

Im looking at a house that has a 150A service. The HO has a Siemens 200A meter/panel combo he wants to install. The combo panel is equipped with feed through lugs so my thoughts were to install the meter/panel and feed throught to the existing 150A panel located inside. My question is do I consider the existing panel a subpanel and if so should the nuetral and ground be isolated? In the existing panel the grounds and grounded conductors are all terminated together so I would need to separate them.

 

[stew]

inside panel is beyond point of service disconnect so then becomes a subpanel and needs isolation of ground and neutral. you are on the correct path.

 

[augie47]

Note also that in most situations the AHJ will want any grounding electrode conductors move to the service (outside) panel.

 

[infinity]

Im looking at a house that has a 150A service. The HO has a Siemens 200A meter/panel combo he wants to install. The combo panel is equipped with feed through lugs so my thoughts were to install the meter/panel and feed throught to the existing 150A panel located inside. My question is do I consider the existing panel a subpanel and if so should the nuetral and ground be isolated? In the existing panel the grounds and grounded conductors are all terminated together so I would need to separate them.

Are these feed through lugs protected by an OCPD?

 

[Cow]

Along with what Rob said, are you going to run 200A conductors to the line side of that 150A panel?

 

[mccayry]

The combo Panel has a 200A main breaker. I was planning on running 2/0 copper from the lugs on the meter combo to the line side of the 150A existing panel.

 

[infinity]

The combo Panel has a 200A main breaker. I was planning on running 2/0 copper from the lugs on the meter combo to the line side of the 150A existing panel.

Are these lugs protected by an OCPD?

 

[mccayry]

The 2/0 connecting from the lugs on the combo panel to the 150A existing panel is protected by the 200A main breaker on the combo panel. I hope that makes since.

 

[infinity]

The 2/0 connecting from the lugs on the combo panel to the 150A existing panel is protected by the 200A main breaker on the combo panel. I hope that makes since.

Got it, so you're sizing your #2/0 (200 amps) from Table 310.15(B)(6) {2008 NEC}.

 

[mccayry]

Yes

 

[kwired]

The combo Panel has a 200A main breaker. I was planning on running 2/0 copper from the lugs on the meter combo to the line side of the 150A existing panel.

The 2/0 connecting from the lugs on the combo panel to the 150A existing panel is protected by the 200A main breaker on the combo panel. I hope that makes since.

Got it, so you're sizing your #2/0 (200 amps) from Table 310.15(B)(6) {2008 NEC}.

310.15(B)(6) can not be used to determine size of these conductors if they are not carrying entire load of a dwelling.

IF the conductors are short enough you are allowed to use tap rules in 240.21. They will have to be in a raceway if using tap rules.

 

[mccayry]

310.15(B)(6) can not be used to determine size of these conductors if they are not carrying entire load of a dwelling.

IF the conductors are short enough you are allowed to use tap rules in 240.21. They will have to be in a raceway if using tap rules.

Do you not think 2/0 Copper is sufficient for feeding the 150A panel?

 

[infinity]

Do you not think 2/0 Copper is sufficient for feeding the 150A panel?

Yes, if that feeder is carrying the entire load of the dwelling because of 310.15(B)(6). {2008}

 

[drive1968]

As long as he's using 2/0 to feed the main, then he's not required to use bigger conductors than that to feed the subpanel, even if the subpanel isn't serving the entire load of the house, correct?

 

[infinity]

As long as he's using 2/0 to feed the main, then he's not required to use bigger conductors than that to feed the subpanel, even if the subpanel isn't serving the entire load of the house, correct?

Nope, the meter main has a 200 amp OCPD protecting the feeder to the panel. If that feeder isn't carrying the entire load then the feeder conductors would need to be rate at a full 200 amps per 310.16. You can't use 310.15(B)(6) if the entire load is not fed from that feeder.

 

[mccayry]

Thanks alot for all the help!

 

[kwired]

Do you not think 2/0 Copper is sufficient for feeding the 150A panel?

1/0 copper is sufficient to feed the 150 amp panel but it can not have 200 amp overcurrent device on the supply side unless it also satisfies the feeder tap rules.

 

[Little Bill]

As long as he's using 2/0 to feed the main, then he's not required to use bigger conductors than that to feed the subpanel, even if the subpanel isn't serving the entire load of the house, correct?

Nope, the meter main has a 200 amp OCPD protecting the feeder to the panel. If that feeder isn't carrying the entire load then the feeder conductors would need to be rate at a full 200 amps per 310.16. You can't use 310.15(B)(6) if the entire load is not fed from that feeder.

Rob, if the service entrance conductors to the combo panel are indeed 2/0 sized from 310.15(B)(6) and he feeds to the 150A panel inside, wouldn't 215.2(A)(3) allow the feeder to be the same size as the service conductors?

 

[infinity]

Rob, if the service entrance conductors to the combo panel are indeed 2/0 sized from 310.15(B)(6) and he feeds to the 150A panel inside, wouldn't 215.2(A)(3) allow the feeder to be the same size as the service conductors?

IMO yes. Good point.

 

[1793]

I know it is early and I may need more coffee but, if there is an OCPD- 200A and then feed to a 150A MB panel, why would you not be able to use 1/0 CU feed from the 200A to the 150A. Wouldn't the 150A MB protect the Feeder conductors?