Whole House Generators

[ljelectric]

It has been stated by local inspectors that when you install a whole house generator with a main breaker transfer switch. If the house was wired with a 6/2 romex range connection, you now have to replace the wire, receptacle and cord with a 6/3 romex, so that the neutral and the ground are fully separate since you had changed the main panel into a sub panel and have separated the neutrals and grounds. Is this correct?

 

[david luchini]

It has been stated by local inspectors that when you install a whole house generator with a main breaker transfer switch. If the house was wired with a 6/2 romex range connection, you now have to replace the wire, receptacle and cord with a 6/3 romex, so that the neutral and the ground are fully separate since you had changed the main panel into a sub panel and have separated the neutrals and grounds. Is this correct?

I think that is correct. It sounds like the circuit would no longer meet part (3) of the exception in 250.140.

 

[qcroanoke]

It has been stated by local inspectors that when you install a whole house generator with a main breaker transfer switch. If the house was wired with a 6/2 romex range connection, you now have to replace the wire, receptacle and cord with a 6/3 romex, so that the neutral and the ground are fully separate since you had changed the main panel into a sub panel and have separated the neutrals and grounds. Is this correct?

If the dryer is 10/2 with ground does he make you change that too?
I don't see how he can make you change it if you don't mess with it.

 

[rlundsrud]

So are you using a 3 pole transfer switch? I don't see why you would have to change the stove if you used a 2 pole transfer and floated the neutral at the generator.

 

[ljelectric]

it is a 2 pole transfer switch. keep in mind that we are changing the main panel into a sub panel by separating the grounds and neutrals. we have now altered the original work. with that being said to me it sounds like that we had lost our exception as indicated above. it would apply to both range and dryers since in the past were wired with a 10/2 or 6/2 and the frame of these appliances were bonded. which also has to be changed.

 

[rlundsrud]

I suppose I don't understand, if it's a floating neutral in the generator and a 2 pole switch, why are you separating the neutral ground in the panel?

 

[kwired]

So are you using a 3 pole transfer switch? I don't see why you would have to change the stove if you used a 2 pole transfer and floated the neutral at the generator.

I agree, then I realized this would only apply if the transfer breaker were in the service panel. See below.

I suppose I don't understand, if it's a floating neutral in the generator and a 2 pole switch, why are you separating the neutral ground in the panel?

I think he was trying to say the original service panel is having the transfer switch or panel with interlocked breakers intalled ahead of it and now the transfer switch/panel is now the service panel. The three wire range circuit is now possibly a violation because it is not run to the service panel anymore. This would be a problem for any situation that changes the original service panel to a sub panel.

 

[rlundsrud]

Ah, that makes sense. So the neutral will be bonded at the generator and isolated at the existing main panel, now I get it.

Can you contact the transfer switch manufacturer and see if you can bypass the breakers and just use it as a switch? I would hope there is a way to avoid using the transfer switch as the main service point. Of course, there would need to be a way to isolate the neutral at the generator. I'm sure this must have come up on other installations, so they probably have addressed this before.

My apologies for being so slow to understand.

 

[kwired]

Ah, that makes sense. So the neutral will be bonded at the generator and isolated at the existing main panel, now I get it.

Can you contact the transfer switch manufacturer and see if you can bypass the breakers and just use it as a switch? I would hope there is a way to avoid using the transfer switch as the main service point. Of course, there would need to be a way to isolate the neutral at the generator. I'm sure this must have come up on other installations, so they probably have addressed this before.

My apologies for being so slow to understand.

If the neutral is bonded at the generator then you have to connect it as a separately derived system and the transfer switch has to switch the neutral.

Most smaller generators and especially portables that are used for backup to a premises system do not have the neutral bonded to the generator frame. By running separate neutral and equipment grounding conductor to the premises wiring (it does not have to go directly to service equipment as the two should remain separated downstream of the service equipment) you rely on the main/system bonding jumper of the premises wiring to bond the neutral an EGC together, which eventually leads back to the generator frame. If operating a portable generator that is not connected to a premises wiring system, you are operating it as an ungrounded system, if any conductor of that system faults to ground - nothing noticeable happens. The EGC terminal on receptacles of the generator are just bonded to the frame but are not really a part of the power system.

 

[rlundsrud]

The OP said he was separating the neutrals and grounds at the old main panels. So where is the neutral going to be bonded?

 

[GoldDigger]

The OP said he was separating the neutrals and grounds at the old main panels. So where is the neutral going to be bonded?

At the transfer switch which will be the service disconnect? Or at new OCPD right before or after the transfer switch?

 

[rlundsrud]

My question was really in response to kwired's statement. If the generator neutral is bonded at the frame and you used a three pole disconnect that switched the neutral you would effectively separate the neutral from the ground for the sub panels.

 

[iwire]

The NEC prohibits a transfer switch on the supply side of the service disconnect .

That being the case the whole house transfer switch will be service rated and will become the new service disconnecting means.

This means the old main panel becomes a subpanel and you can't have 3 wire feeds to dryers and ranges.

 

[Little Bill]

The NEC prohibits a transfer switch on the supply side of the service disconnect .

That being the case the whole house transfer switch will be service rated and will become the new service disconnecting means.

This means the old main panel becomes a subpanel and you can't have 3 wire feeds to dryers and ranges.

You can still have 3-wire feeds from subpanels. As long as SE cable with bare neutral isn't used. If it is, THEN, it can't be used from a subpanel.

I thought we settled this a while back.

3) The grounded conductor is insulated,} or the grounded
conductor is uninsulated and part of a Type SE service entrance
cable and the branch circuit originates at the
service equipment.

The part in blue is the first part of the sentence. Notice the comma!
The part in red is the second part of the sentence. The "and" between "cable" & "the" means it's also part of the second part of the sentence.

So, for existing installations with 3-wire you can still feed dryers and ranges from a subpanel as long as it's not SE cable with a bare grounded conductor.

 

[iwire]

You can still have 3-wire feeds from subpanels. As long as SE cable with bare neutral isn't used. If it is, THEN, it can't be used from a subpanel.

I thought we settled this a while back.

3) The grounded conductor is insulated,} or the grounded
conductor is uninsulated and part of a Type SE service entrance
cable and the branch circuit originates at the
service equipment.

The part in blue is the first part of the sentence. Notice the comma!
The part in red is the second part of the sentence. The "and" between "cable" & "the" means it's also part of the second part of the sentence.

So, for existing installations with 3-wire you can still feed dryers and ranges from a subpanel as long as it's not SE cable with a bare grounded conductor.

The OP has a 6/2 NM that is two insulated and a bare conductor.

That cannot be run from a subpanel to the range.

 

[iwire]

My question was really in response to kwired's statement. If the generator neutral is bonded at the frame and you used a three pole disconnect that switched the neutral you would effectively separate the neutral from the ground for the sub panels.

Switching the neutral does not change the rules.

 

[ljelectric]

It is bonded at the service rated transfer switch

 

[Little Bill]

This means the old main panel becomes a subpanel and you can't have 3 wire feeds to dryers and ranges.

The OP has a 6/2 NM that is two insulated and a bare conductor.

That cannot be run from a subpanel to the range.

I was replying to your statement (in red) saying you couldn't run 3-wire from a subpanel.
Sounded like a "blanket" statement for any 3-wire from a subpanel.
I will agree with no bare neutral from a sub.

Side note: I've never seen an inspector make anyone change an existing 3-wire when adding a transfer switch and making the existing main a sub. I suppose they could, just never seen it.

 

[kwired]

The OP said he was separating the neutrals and grounds at the old main panels. So where is the neutral going to be bonded?

My question was really in response to kwired's statement. If the generator neutral is bonded at the frame and you used a three pole disconnect that switched the neutral you would effectively separate the neutral from the ground for the sub panels.

Equipment grounding conductors are not opened in either case with generators - separate/non separately derived systems.

With the separately derived system your standby neutral is bonded at the generator your utility neutral is bonded at service equipment, the neutral is transferred with the ungrounded conductors to whichever source is being used, the equipment grounding conductor is still connected to the neutral from both sources as neither bonding jumper gets interrupted in any way.

The opening of the neutral in the transfer switch of a separately derived source prevents neutral current from taking parallel paths through equipment grounding conductors, this is not a problem with non separately derived as the neutral is not bonded at the generator, it is bonded at the service equipment.

 

[rlundsrud]

Thank you all for the follow up info. I know I wasn't the OP, but this was an interesting post and it answered several questions regarding this type of installation.