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Question about generator transfer switches

Jim Caudill

Stainless
Joined
Nov 3, 2002
Location
Dayton, Oh
For those of you that may not know, much of our region here in Ohio was without power following the windstorm created as Ike moved thru a short while back. Many of my relatives were without power for up to a week. I have 3 generators (one of which I just repaired with help from this board), 2 of which are portable and 1 is in an RV. It seems like power outages here, have become more and more common. I would like to develop a plan to keep my house warm and lit during a winter ice storm.

I am interested in powering my natural gas furnace circuit which contains electrical demand for igniter, thermostat, and blower motor. Powering a couple of light circuits with half-dozen 15w compact flourescent would be good also.

I have a 200amp main breaker that is fed directly from my outside meter. Would switching this breaker off provide the same degree of circuit interruption of a manual transfer switch? It seems like I would only be "breaking" the hot wires. If I then back-fed the electrical panel, I am concerned about current existing in the neutrals and being carried some way back to the main lines. Do transfer switches isolate the desired circuit's neutral and ground as well as the hot wires? What is the most economical way to safely accomplish the powering of a few circuits that are "wired-in" to the house?
 
Somebody correct me if I'm wrong, but most factory-made transfer switches
do not switch the netural leads. The generator in use is still bonded to the
made electrode at the service entrance, and the incoming neutral is tied to that
as well.

Jim
 
You really need to have a transfer switch installed (switching the live and the neutral, assuming you have a single phase supply) otherwise it would be possible to back feed the supply if you were to turn the main breaker back on with the generator running, the possible consequences for anyone working on the line don't bear thinking about.

The other risk is to your generator, if you were to have the generator connected and re connect the main supply you would have a plentiful supply of smoke and no generator.

DM
 
Jim,

I don't think there's any risk of back feed as long as there's no voltage potential between the neutral and hot leads. Hurricane Ike tore our neighborhood up pretty good as far as lines and poles go, fortunately our homes pulled through pretty well. I have a Powermate 5500 watt that we ran for nearly two weeks back feeding into the welder outlet in the garage, I have an older breaker box that requires multiple breakers open to de-power everything. The welder outlet is on the house lighting main breaker thus thats the only one I had to open to safely backfeed into everything I wanted to power. Be forewarned I'm sure it's not code and your local utility company cold be very angry. That said I've never seen the linemen around here work on lines without all the high voltage line lines bonded to ground (probably to protect themselves from idiots like me) I do intend to invest in a manual transfer switch before the next hurricane season, it will meet code and make the whole process way simpler and safer. Northern Tool has a ton of generator accessories, you may want to browse their inventory. Here's a link to Reliance that makes a switch I'm looking at.
http://www.reliancecontrols.com/

Take Care,
Robin
 
I have searched this website fairly thoroughly and read well over 150 posts regarding generators and transfer switches and all the dire warnings regarding linemen. About 20 years ago I upgraded my electrical system from 100amp service to 200amp service and had both the power company and city building inspectors approve of my work. A building permit was required and a slight deviation from the current regs was required due to the age and location of my garage (unable to maintain vertical distance between roof and line).

I have no desire to do anything that will involve having an inspector back on my property. Suffice it to say that I didn't have my shop when I did the upgrade.

Thanks Robin, I was typing while you were responding. Which model switch were you looking at? Lowes or Home Depot has a Reliance switch for around $300, which seems like a lot when you consider what a Square-D load center goes for. It may be that the $300 is an automatic with generator "exercising" or something. I just want to be able to isolate 2 or 3 120vac circuits, that I can then power up from a generator. I know, sounds exactly like a job for a manual, generator transfer switch. Back to what Jim Rozen is suggesting, and I questioned, do these things isolate the neutral and grounds? Some of the instructions for the transfer switches seem to only talk about controlling the "hot" wires.
 
Jim Caudill,
I own and work hands on in an electrical contracting company. my point is that with a transfer switch installed it is not possible to back feed the line. In the situation you are proposing this is possible when using your main breaker as an isolator.

Also if your property is protected by a residual current device this will not operate if the generator is not connected correctly.

DM
 
DM, thanks for responding. Perhaps things are a little different in the UK. In your first post you mention having a proper transfer switch to isolate the neutral and hot lines for a given circuit. This is exactly where my question lies.

Online instructions I have read, indicate that only the hot wire is switched by using readily-availble transfer switches that are approved for such use.

Here is a link to Reliance Controls installation manual. They only switch the "hot" wire going to the breaker. Neutrals and grounds are not isolated. This type of installation complies with our code, but would seem to be at odds with your familarity.
http://www.reliancecontrols.com/Documents/ProTran Instructions.pdf
 
There are very good reasons to install a proper transfer
switch to do this job.

Any suggestion, however, that power may be backfed to the
lines via the neutral, is incorrect as neither the
real transfer switch, or an opened main breaker, interrupt
the neutral line.

I might add that pulling the meter could get one into
some hot water with the utility later on down the road,
but if you did it to ensure isolation from a generator
they might look the other way....

Just a thought.

Jim
 
Opening the main breaker provides all the protection that a transfer switch procvides except for one. A transfer switch provides a positive interlock with the main lines. Your way you have to remember to do it manually. That's the difference. As long as you do right every time, no problems. Forget once and you back feed the entire grid, and likely smoke the genertor when the power comes back on. The reason you don't break the ground and neutral is the safety ground provided by the driven ground stake.
 
Jim,
I'm taking a look at the Reliance R30310B, Mine has to be rain tight. The price annoys me too, I suppose it's a relatively smaller production specialty item than household load centers thus the price. The cheapest I saw on the internet was Steadypower.com @ $375 I didn't check on shipping though.
 
I've run my 5.6KW gen hooked to a welder plug in my shop about a dozen times including once for 12 days. It gives me almost normal power. I have to shut off my hot water heater and if I'm running two window AC's and my water well pump comes on the breaker trips on the gen.
I just make DAMNED sure of the sequence for shutting off the main breaker and powering up the gen is done correctly. If you are absent minded or have others that might mess with things put some tape over the main breaker as a reminder when it's off.
 
Jim, We were out of power for 10 days since only 16 people were on our line we weren't worth fixing right away. Frustrating when there is power all around you. I bought a generator online, it got here the day after the power came back on. I am buying the transfer switch online as well from these guys:
http://www.electricgeneratorsdirect.com/ $248 delivered for the same switch mentioned above. -Mike
 
The transfer switch switches BETWEEN generator lugs and line lugs...... The common part of the switch is the input to the premise service box.

Obviously there is no chance of a backfeed.

If you shut off the main, and feed in somewhere, you can power your house. The three problems are that

1) the utility or inspectors will have a bouncing hissy-fit.
2) obviously you CAN switch it to power your drop, and the outside area, although it will almost certainly overload the genset due to still-connected outside loads, or blow the genset if your power is back on and you hit the mains with the genset still connected.
3) you will have, one way or another, a live plug with male prongs, somewhere in the system. Either on the genset, or out the box...... Those make for painful mistakes......

In an emergency, I'd do whatever is needed, and the rules can go hang. But a transfer switch is the code-correct way to do the job.
 
Neutral is bonded to ground at the service entrance. Chances of feeding back anything into the line on the neutral are about zero. Don't worry about switching the neutral. None of the transfer switches do that.

Get one of the simple manual switches. They do not require turning off the main breaker for use. They individually switch usually 6 circuits. One 220 and 4 110 circuits. They can be installed yourself if you have the skills. You don't have to use all the circuits if you don't need them. Just remove the hot wire from a breaker in your panel. Connect one circuit of the transfer switch with a wire to the breaker and a wire to the hot wire with a wire nut. A whole-house switch requires an electrician since you have to break the seal on the meter. Not necessary unless you have a generator big enough to power the whole house. 20 KW or larger.
 
Correct me if wrong but isn't an auto-transfer switch just a relay?

IOW, the coil is fed by the incoming power...if there is any, the relay connects the grid to the breaker panel thru the NO contact. If no coil voltage, the NC terminal (generator) then is connected to the breaker panel. Since NO and NC contacts never touch each other and the relay can't occupy both states at the same time....there can be no danger of connecting generator.

I suppose the reality is more highly developed than that, especially with the heavy-duty contacts of a motor starter or lighting contactor, and there's probably a strategy to deal with when to switch "back" to grid power.
 
Although...

For a two pole, double throw relay (the kind in use for such an auto X-switch)
it might be possible to have one one set of contacts on one pole stick, and the
other ones transfer. That would be exciting.

:)

Jim
 
There are in fact two types of transfer switch. One that switches the neutral as well as the hots and one that only switches the hots. To be intirely to code ( at least in Nova Scotia ) your generator type must match your transfer switch type. Some generators have a bonded neutral and others have a floating neutral. Back feeding the panel without a transfer switch is easily done but not legal because it leaves the possablity that someone could switch the mains breaker back on while the generator was running and back feeding the line which would be dangerous to the lines man.
 
years ago when I added a generator to the house/shop, I put in a commercial ATS that was used, bought at a surplus place. Ugly but functional.


It seems to have a fail-safe feature, when the utility is energized, there is a large magnetic
contactor that "breaks" the generator circuit from the rest of the switchgear.

When the utility power shuts off, there is a loud "CLUNK" as the contactor magnet de-energizes and
falls down (gravity & a spring) to make the circuit to the generator, disconnecting the utility input.

winco_ats.jpg


ats_schematic.jpg
 
The issue of neutral is interesting, since there may be different systems.

The most common system in the US is that the 240V line at the pole has its neutral point grounded at every pole. That very same neutral is brought in to your service, and becomes both your neutral, AND your equipment grounding conductor. It is also the neutral of the distribution voltage.

Your service has a ground (earthing) stake, at least, and often a more effective ground than stakes, such as water pipes. (the stake may have a resistance as high as 25 ohms, making it "legal" but almost totally ineffective).

Most codes do not allow any sort of switching or fusing in the neutral (grounded conductor), at least within a structure.

it is possible to envision a case where the pole neutral becomes energized with the distribution voltage, but that case will blow at least one fuse or open a breaker in the mains elsewhere.

To become entirely independent of the grid, you WOULD disconnect neutral. It may not be allowed, or apparently, in some cases it may be required... Just follow the local code and you will be OK.

The other system is where distribution voltage has no neutral, using earth instead. I believe the 240V side is the same, however, with local pole ground, premises ground stake, etc. The pole ground for the low voltage in some practice is separate from the earth return stake, , but the new Zealand code, for instance, appears to allow other grounds to connect to the supply stake, although supply line is limited to 8 amperes.

Same considerations for the service should apply.

There might be more reason to disconnect neutral however, since the relatively poor single pole ground (earthing) might allow neutral to have a voltage significantly off-ground, or to conduct fault current into your premises neutral if the high voltage becomes grounded to your earthing stake for the low voltage, or the grounds become interconnected..

Both conditions might be hazardous. And you are using the generator because there is a problem, possibly poles down, wires crossed, etc, so you do not know for sure that the neutral is good.
 








 
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