Generator panel

[fisherelectric]

I'm looking at a Reliance generator transfer panel that says:

"The X Series? exclusive, patent-pending switching mechanism will break the two hot legs of the circuit, in either direction, before the neutral is broken. It will then close the neutral before the two hot legs close. This prevents destructive 240V current from momentarily powering the 120V circuits and damaging inductive motors and sensitive electronics."

This is a panel that has 2 mains, one fed from utility, one fed from generator, and opening one closes the other. I have installed panels like this in the past and never switched the neutral. What up with this?

 

[augie47]

Some applications, ones with GFP main protection plus some others, require the neutral be switched.
What size service are we switching ?
Keep in mind, with a switched neutral, your generator will now be a SD and 250.30 will now apply. Grounding will be different.

 

[fisherelectric]

I'm just using a 30amp flanged inlet and a 4 wire cord from from a 6500 watt portable generator to feed this panel. Maybe this is the wrong panel for me? It's a 10/18 circuit panel rated at 30 amps or 60 amps.

 

[ceb58]

That panel is what is being used for portable generators where the N-G are bonded in the generator. The portable is a SDS.

 

[fisherelectric]

So do most portable generators have N&G bonded? These people haven't actually purchased this generator yet. How does this effect the wiring in the panel....neutral from service and neutral from generator are separated and circuit load neutrals get switched between?

 

[ceb58]

So do most portable generators have N&G bonded? These people haven't actually purchased this generator yet. How does this effect the wiring in the panel....neutral from service and neutral from generator are separated and circuit load neutrals get switched between?

Yes, your portable units will have the N-G bonded together. The utility and generator neutrals are separated and they are switched between utility and generator. The generator can also be a stationary unit also and be set up as a separately derived system but is not necessary in a normal residential setting. I would see what they intend to buy before I did anything.

 

[jes25]

Yes, your portable units will have the N-G bonded together.

Not true. A lot of generators have floating neutrals and are even marked as so on the front panel.

The utility and generator neutrals are separated and they are switched between utility and generator. The generator can also be a stationary unit also and be set up as a separately derived system but is not necessary in a normal residential setting.

Now I'm confused. If the neutral is switched the generator must be set up as a SDS.

Fisher, I would just buy a regular generator panel (unswitched N) and tell the customer to buy a gen with a floating N. The bottom line is that any generator can and will be plugged in so it almost doesn't matter. Plus if the N was or wasn't bonded in the gen it pretty much makes no difference with a portable.

 

[fisherelectric]

Thanks for the info. I take it that a generator having a 4 wire receptacle like an L14-30 doesn't necessarily mean that it won't have the N-G bonded together?

 

[ceb58]

Not true. A lot of generators have floating neutrals and are even marked as so on the front panel. Ok you are correct some not bonded




Now I'm confused. If the neutral is switched the generator must be set up as a SDS.

The bottom line is that any generator can and will be plugged in so it almost doesn't matter. Plus if the N was or wasn't bonded in the gen it pretty much makes no difference with a portable.

That is a very arrogant and misinformed statement. From the UL white book

ENGINE GENERATORS FOR PORTABLE USE (FTCN)

GENERAL
This category covers internal-combustion-engine-driven generators rated
15 kW or less, 250 V or less, which are provided only with receptacle outlets
for the ac output circuits. The generators may incorporate alternating or
direct-current generator sections for supplying energy to battery charging
circuits.

When a portable generator is used to supply a building wiring system:
1. The generator is considered a separately derived system in accordance
with ANSI/NFPA 70, ‘‘National Electrical Code’’ (NEC).

2. The generator is intended to be connected through permanently
installed Listed transfer equipment that switches all conductors other
than the equipment grounding conductor.

3. The frame of a Listed generator is connected to the equipment grounding
conductor and the grounded (neutral) conductor of the
generator. When properly connected to a premises or structure, the
portable generator will be connected to the premises or structure
grounding electrode for its ground reference.

4. Portable generators used other than to power building structures are
intended to be connected to ground in accordance with the NEC.

Take the time to read over this http://forums.mikeholt.com/showthread.php?t=150449

 

[jes25]

That is a very arrogant and misinformed statement.

My apologies if I came across arrogant.

I had a couple basic points please let me know which ones disagree with.

1) If the neutral is switched the generator becomes a SDS based on the NEC definition that "such systems have no direct electrical connection including a solidly connect grounded (neutral) connection.

2) It is a code violation to not switch the N and have it bonded in both the portable generator and at the service. ie; parallel paths

3) As a practical matter it is easiest to switch only the hot conductors, and that as an electrician you have no control over what type of generator is plugged into the outlet; and even if, a gen with a bonded outlet was plugged in in would not cause any real safety issue.

 

[ceb58]

My apologies if I came across arrogant.

I had a couple basic points please let me know which ones disagree with.

1) If the neutral is switched the generator becomes a SDS based on the NEC definition that "such systems have no direct electrical connection including a solidly connect grounded (neutral) connection.

2) It is a code violation to not switch the N and have it bonded in both the portable generator and at the service. ie; parallel paths

3) As a practical matter it is easiest to switch only the hot conductors, and that as an electrician you have no control over what type of generator is plugged into the outlet; and even if, a gen with a bonded outlet was plugged in in would not cause any real safety issue.

Ok, on 1 & 2 you are totally correct. I agree also on half of 3 it is easer and we have no control. It is the last part that you your self have said it is a code violation. Look at #1 & #2 If the N-G bond were left intact in the portable and it were installed with out switching the neutral then you have created a parallel path.

When a portable generator is used to supply a building wiring system:
1. The generator is considered a separately derived system in accordance
with ANSI/NFPA 70, ??National Electrical Code?? (NEC).

By UL's instructions not switching the neutral would also be a violation. As far as having no control on what type generator the customer buys I semi-disagree. I think it's our responsibility to tell the customer the generator must be there at the time of installation and advise them of what to buy or be ready to install ether type in a compliant manner. Now what the customer goes and buys in a years time, after the original one craps out, we have no control of.