Portable Generator Cord Length

[mkgrady]

This customer wants to have a 5500 watt portable generator power his house. I would install an interlock between his MCB and a generator CB (30 amp) and wire that to an inlet on the outside of the house about 25 feet from the panel. The issue is that he wants to operate the generator 80 feet away from the inlet. I'm wondering if that distance (105') would create a big enough voltage drop to be a problem or if it raises any other concerns.

 

[roger]

When I use my generator in power outages (6500 watt) it is about 100' from my panel, I use #8 SO for my cord.

I use general lighting circuits, refrigerator, and freezer normally however, I do have to selectively use my well pump and water heater and have never had a problem.

My heat is propane and wood and I don't need A/C most of the year, the nice thing about being in the mountains.

Roger

 

[jumper]

As a personal rule, I generally do not worry about VD at 100' or close. However, for a genny I would upsize to #8 in this application also here as Roger did. Not NEC mandated.

 

[tkb]

Here is what MA has to say,

Insert a new 702.11(C) as follows:

(C) Classification of Supply. A generator with a grounded circuit conductor connection as part of its output shall be wired as a separately derived source unless its grounded circuit conductor is not bonded to the frame, or where used to supply a premises wiring system it shall be permitted to be wired as a nonseparately derived source if all of the following conditions are met:
(1) The generator rating does not exceed 15 kw.
(2) The generator is connected through a flexible cord and a cord connector to a flanged inlet.
(3) The flexible cord does not exceed 4.5 m (15 feet) in length.
(4) The flanged inlet connection point is not more than 3.0 m (10 feet) from the main bonding jumper or system bonding jumper for the supplied premises.
(5) The point of connection is marked ?Disconnect cord when generator is not in service.?
(6) Ground-fault protection of equipment has not been installed on any portion of the premises wiring system supplied by the generator.

Informational Note: Current product standards require all portable generators rated 15 kw and below and supplying grounded output circuits to have the grounded circuit conductor connections bonded to the generator frame.

 

[mkgrady]

Here is what MA has to say,

So to do this job in MA I have to seperate the neutral from the frame of the generator? And comply with the rest but I don't understand #6.

6) Ground-fault protection of equipment has not been installed on any portion of the premises wiring system supplied by the generator. Is it saying the house can't have any installed GFI breakers or receptacles? It must mean something else but I don't know what.

Any guess as to the reasoning of this MA ammendment?

 

[suemarkp]

You don't have to separate it from the frame, but if you choose to do so you'll need to meet all those rules. If you can't or don't want to meet the rules, then wire as a SDS and switch the neutral.

GFPE is not the same as GFCI. GFPE is what you typically need to install on the larger services (over 800A I think?).

 

[mkgrady]

You don't have to separate it from the frame, but if you choose to do so you'll need to meet all those rules. If you can't or don't want to meet the rules, then wire as a SDS and switch the neutral.

GFPE is not the same as GFCI. GFPE is what you typically need to install on the larger services (over 800A I think?).

It would seem dangerous to not have the gen frame bonded to neutral so it makes sense that would not be the case.

Isn't the neutral considered switched by the twist lock cord connections at both the gen and the inlet?

 

[tkb]

You don't have to separate it from the frame, but if you choose to do so you'll need to meet all those rules. If you can't or don't want to meet the rules, then wire as a SDS and switch the neutral.

GFPE is not the same as GFCI. GFPE is what you typically need to install on the larger services (over 800A I think?).

What about roof snow melting cable?
426.28 requires GFPE to protect the cable.

The way I read the Mass amendment is that you cannot power the same panel that has the snow melt cable with a portable generator.

 

[mkgrady]

What about roof snow melting cable?
426.28 requires GFPE to protect the cable.

The way I read the Mass amendment is that you cannot power the same panel that has the snow melt cable with a portable generator.

I will now invent an interlock that will prevent snow melt systems from operating while using a portable generator to power a home!

 

[kwired]

It would seem dangerous to not have the gen frame bonded to neutral so it makes sense that would not be the case.

Isn't the neutral considered switched by the twist lock cord connections at both the gen and the inlet?

A generator that doesn't have the neutral bonded to the frame, will have a 4 wire supply to the premises wiring, the neutral will be bonded to the equipment ground at the service equipment, and will return via the EGC in the 4 wire supply to bond the frame of the generator.

The neutral needs to be switched by the transfer switch for separately derived systems not a cord connector. If somehow the cord connector is the transfer switch then I suppose the neutral could be considered switched but that will not happen.

Separately derived generators are completely isolated other than equipment grounding conductors from the other source and the transfer switch needs to transfer all current carrying conductors.

A non separately derived generator has the grounded conductor tied to the grounded conductor of the other source at all times but only looks at the transfer method for this determination and not cord and plug connections.