Generator transfer switch

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Re: Generator transfer switch

does a single phase transfer switch even have enough switches to do that?
 
Re: Generator transfer switch

It depends on whether the neutral is bonded to the ground within the generator. If it is, then you must switch the neutral. If it is not, then it is not a separately derived system and the neutral in the transfer switch shouldn't be switched.
 
Re: Generator transfer switch

It can be done either way. But more importantly, it can be done wrong either way. There is a right way, and several wrong ways, to have the system switch the neutral. There is a right way, and several wrong ways, to have the system not switch the neutral.

You need to be talking to the electrician who will install this for you.

Please note that if you plan on doing this job yourself, the rules of this Forum prohibit us from giving you and advice or assistance.
 
Re: Generator transfer switch

Typically a transfer switch for a dwelling only switches the phase conductors (single phase). The grounded conductor (neutral) is solidly connected. A transfer switch that switches the neutral will be quite expensive relative to a single phase transfer switch.

If you install a single phase TS, remember that the neutral to ground bond needs to be isolated just as a subpanel would be.
 
Re: Generator transfer switch

I asked 12 electricians 4 with masters 8 journeyman that I work with they all say to switch the neutral but not for reasons posted. They all believe that the generator can back feed on the neutral) conductor a hurt a line man doing repairs. How would this be possible?
If there was a problem with my ground or the neutral) conductor then nothing should work. Am I correct? Now there is a difference between standby generator Nonseparately Derived System and a portable generator Separately Derived System furthemore Switching a neutral incorrectly can cause equipment malfunction so why would anyone want to switch a neutral?
 
Re: Generator transfer switch

If for some reason you had ground fault protection, switching the neutral would reduce false tripping. If you had a generator that couldn't have the neutral to ground bond removed, then you must switch the neutral.

If the generator neutral to ground bond is removed, and you don't switch the neutral, there is no risk of hurting a lineman by back feeding on the neutral.
 
Re: Generator transfer switch

mastergasfitter,
Switching a neutral incorrectly can cause equipment malfunction so why would anyone want to switch a neutral?
Click to expand...
How? All circuit conductors are switched at the same time.
 
Re: Generator transfer switch

Don,
There is actually a down side to switching the neutral.
A potential for abnormal surges due to momentary open-transition switching of all contacts;

A potential for abnormal surges due to momentary open-transition switching of all contacts, as well as neutral contact erosion; and

Dangerous voltage transients may occur.

This article has both methods of switching the neutral, additional pole to switch neutral, and overlapping neutral contact methods.
http://ecmweb.com/mag/electric_switching_neutral_whats/index.html

The downsides of either method of switching the neutral shouldn't cause someone to purposefully violate the code. If the gen n-g is bonded, then you must switch the neutral.
 
Re: Generator transfer switch

Ron,
I don't see anything in that article that indicates that switching a neutral would cause any problems in a dwelling unit and most likely not anywhere else either.
In fact, the transient voltages normally found in distribution circuits in industrial or commercial installations are far more severe than the ones the switched neutral might produce.
Click to expand...
Don
 
Re: Generator transfer switch

There are problems with switching the neutral.
When the neutral fails to switch or partially switches.

Furthermore isn't the neutral and the ground the one in the same at point of metering or at each panel or sub panel?

Using a 3 phase transfer switch for single phase, and using the 3rd leg for the neutral is against the manufactures suggested usage.
3 phase transfer switches are not designed to switch the neutral
Now I am just a gas fitter that is going to be connecting the gas to allot of these units and I find it amazing on how few electricians know anything about how to connect a (fixed,stationary, or in your own terms a Non separately Derived System) generator.
A portable generator or separately Derived System that can be moved should never be connected to house wiring,, That is why they have receptacles and breakers on them. unless the manufacture indicates such usage and provides an easy method for doing so
 
Re: Generator transfer switch

One more thought about switching neutral on a
separately Derived System. Could this be a reference to DC a bank of back up batteries
solar panels. wind power and in that case wouldn't you want to switch the entire system neutral and the ground
 
Re: Generator transfer switch

mastergasfitter,
There are problems with switching the neutral. When the neutral fails to switch or partially switches.
Click to expand...
The same can be said if any of the contacts fail to switch.
Furthermore isn't the neutral and the ground the one in the same at point of metering or at each panel or sub panel?
Click to expand...
If you are switching the neutral you have a SDS (separately derived system) and both the utility and the SDS have main or system bonding jumpers.
Using a 3 phase transfer switch for single phase, and using the 3rd leg for the neutral is against the manufactures suggested usage.
3 phase transfer switches are not designed to switch the neutral
Click to expand...
Who said anything about using a three phase transfer switch to switch the neutral for a single phase system? Transfer switches intended to switch the neutral are available for both single and three phase systems.
Now there is a difference between standby generator Nonseparately Derived System and a portable generator Separately Derived System ...
Click to expand...
fixed,stationary, or in your own terms a Non separately Derived System
Click to expand...
The fact that a power source is fixed or stationary has nothing to do with whether it is a SDS or not. As fas as genereators go, if you switch the neutral, you have a SDS, otherwise you don't have a SDS. The most common SDS, by far, is a transformer, and almost all of those are fixed or stationary.
A portable generator or separately Derived System that can be moved should never be connected to house wiring,, ...
Click to expand...
Can you cite a code section or source for that statement? Article 702 specifically permits the use of portable generators to supply power to buildings.
Don

[ December 03, 2005, 05:34 PM: Message edited by: don_resqcapt19 ]
 
Re: Generator transfer switch

I am sorry that I gave a personal opinion as far as portable generators. versus standby.
About using a three phase transfer switch. As I stated in the beginning of this post I asked several electrician and several of them suggested it. I never would have thought of a transformer being SDS since it doesn't create it own source it changes it. and yes it does have its own neutral but uses a bounded ground or am I way off base.
and BTW I am using this information and other information to advise those electricians of the difference between DSD and NSDS
 
Re: Generator transfer switch

Originally posted by mastergasfitter:
About using a three phase transfer switch. As I stated in the beginning of this post I asked several electrician and several of them suggested it.
Click to expand...
I think they are mistaken at least for auto transfer switches.

A 3 phase transfer switches 'brain' would expect to 'see' 3 phase incoming power. It would treat a neutral in place of one of the hots as a power failure.

Originally posted by mastergasfitter:
I never would have thought of a transformer being SDS since it doesn't create it own source it changes it.
Click to expand...
It is definitely an SDS to the NEC, it has no direct electrical connections from one side to the other (almost ;) )
 
Re: Generator transfer switch

I believe this thread has outlived its usefulness. The question has been answered. I am closing it now.
 
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