OT Electrical Question

I'm looking at getting a stationary standby generator. Here's my set up now. Our main electric comes into the house with the breaker panel in the basement. Off of this panel I feed our shed with 200 amp service (2-100 amp breakers). My question is. Can I hook the generator up to my shed with a transfer switch in the shed or does the transfer switch need to be in the house? I would think I can put it in the shed.
Right now I have an older 42 amp 11hp generator I plug into the breaker box in the shed and it backfeeds into the house and runs everything except the AC. I just have to flip the main breaker in the basement box first though.

The transfer switch has to be between the incoming power and the 1st panel. So no, you can't put it in the shed.

The transfer switch would need to be between the line and your intended load. You shouldn't back feed for the purpose of safety and to save your generator. On a portable generator it is easy to kill the main and back feed through the breaker box and no problem will arise as long as one doesn't forget to throw the main off. With a standby and using a transfer switch the transfer switch and the line from the generator must be up stream of any intended loads. The transfer switch will isolate the gen from any upstream load or power.

Just an FYI for anyone reading this, if you forget isolate (kill the main breaker or use a transfer switch) your generator from the line (power company). One of two things could happen. If a lineman begins to work on the line that should be dead from the power company and you just now energized it with your generator guess what happens. The other thing is when the power is restored the phases won't match your generator and your generator will be fried.

If you only want to power this one building with this generator you could put a transfer in the incoming power feed for this building. That way you can disconnect the building from the incoming power and connect the building to the generator.

I know the generator will be fried if not phased
in. Now another question has risen. My transformer
is in our yard 80ft from our house. To my
understanding when my generator is running it can't
back feed in thru the transformer and create
current out on the main line along the road,
correct?

SHORT ANSWER NOOOOOOOOOOOOOOOO

Im sure there will be a ton of good responses (as for legal or electrical questions) so I may as well get my two cents worth in early and see how many agree or disagree?? No Warranty, Im not saying Im right or wrong mind you, wire it however you please......... YES Billy Bob, his method will still "work"

John, If you put the Transfer Switch in the shed, just what is it you intend to "transfer"???

It sounds like you want to backfeed the main panel via the circuit breaker that feeds the shed and you want to switch the feeder from either supplying the shed as normal to instead being powered via the Generator. THATS NOT THE NORMAL TRANSFER SWITCH FUNCTION and it defeats the switches safety feature because its to prevent backfeeding the utility if your loads are being fed by the Genny. If you connect the genny that way and the main breaker isn't opened you can backfeed the utility IM SURE YOU KNOW THAT AND INTEND TO FLIP THE MAIN BUT THATS JUST NOT HOW AND WHY A TRANSFER SWITCH IS INTENDED TO OPERATE.

How a transfer switch is intended is to transfer whats feeding your house from EITHER the Utility OR the Genny and in so doing the other source is isolated to prevent any possibility of a potentially hazardous backfeed.

There would be two INPUTS to the Transfer Switch, The UTILITY ORRRRRRRRRRRR THE GENNY and one Output, your main panel. What youre transferring is the source to your house from the genny orrrrrrrrrr the utility and the two can never meet...........

There are relatively inexpensive transfer methods, one of which is merely a panel mounted locking slide out in which case the backfeed breaker cant be on at the same time the main breaker is. If the main is on the backfeed breaker must be off and vice versa. Or you can buy a full fledged transfer switch.


NOTE if you want to use only a 2 pole transfer switch to switch 120/240 volt single phase three wire (probably what you would do):

a) If the genny has the Neutral bonded to the case/frame YOU NEED TO SEVER THAT BOND.

b) You must carry FOUR wires from (assuming its a 120/240) genny to transfer switch, 2 Ungrounded (Hot) Conductors,,,,,,,,,,,,1 Grounded (Neutral) Conductor,,,,,,,,,,1 Equipment Grounding Conductor.

c) The Genny Neutral and the Utility Neutral ARE BONDED TOGETHER (may do so at switch)

d) Carry the equipment Grounding conductor out from the main to the case/frame of the genny

e) The genny is NOT a separately derived source configured as above and does NOT require connection to a grounding electrode (ground rod for Billy Bob) however its case/frame needs bonded to the equipment grounding conductor.

I think this is correct but Ive been retired from active EE desing a long time so no warranty, see if some of the fine still practicing electrical gents like drsporster or Dusty or several others agreer or not.

HOWEVER ITS NOTTTTTTTTTTT WHAT ANY OF US SAY THAT MATTERS, CONSULT WITH LOCAL AUTHORITY AND YOUR UTILITY PROVIDER AND DO AS THEY SAY..

Nuff said,

John T

The electrician that put in the 19kw farm generator here did it that way. You throw the transfer there and then throw the breakers he installed at the house. It is about a four step process but the farm runs just like normal with the diesel generator running. There is a lot of power going to the machine shed normally so the overhead lines are plenty big. The neighbors hate me when they see the yard lights working during a blizzard.

Whatever you do - no Generac.

NOT CORRECT

The Utility Transformer is an AC In/Out Step Up/Step Down device. It has around 9600 VAC Primary IN which it steps down to 240 VAC Secondary OUT HOWEVER If it sees 240 VAC on its Secondary GUESS WHAT it will transform that to 9600 VAC up on the utility and if its connected that can fry a utility lineman.

FOR SURE IF YOUR GENNY IS RUNNING AND ITS NOT ISOLATED (main isnt switched off) and its backfeeding a breaker in your panel IT SENDS 9600 VOLTS BACK UP HOT ON THE LINE and that can ruin a linemans day electrocute him (but those guys know what they are doing and will turn off or ground out guys like you)

No warranty Im right but sure you wanna take that risk of killing someone?????

John T Retired Electrical Engineer
Untitled URL Link

Any licensed electrician can quote it for you.

If you are going to wire that yourself find out ahead of time what your building inspector will approve, so you don't have to wire it twice. If you improperly wire it yourself, your insurance company can use that to refuse to pay for damages or liability claims.

What you need to be lega and for that matter smart:

A transfer switch will unplug the main power lines from the utilities before it will then engage the power lines from your generator.

So one switch will allow either but -never both- sources of power to be fed into the wires.

If you want your generator to power just your shed, you can put the transfer switch there.

If you want it to power just the hose, you can put the transfer switch there.

If you want the generator to be able to power your whole place, you will need to put the transfer switch by the main meter/ transformer/ area.

I think the others might have real good advice, but we are missing the starting basics - the transfer switch is designed so any dummy at all can't possibly have both the generator and the utility transformer ever connected to each other. Ever.

That is what the transfer switch does.

Paul

Hey John, let me try and summarize what I am seeing here.
1. The word "Transfer Switch" is being mis-used in some parts of this conversation. What you are doing now with your 11hp generator is a simple back-feed kept safe only by the fact that you manually disconnect from the power grid at the house first. This works as long as you do these manual tasks in the correct order. There is no "Transfer Switch" in what you have now. You could run your new generator in the same way. But it is manual and someone could mis-sequence the switches and cause issues, perhaps damage. You may not always be present to do it "properly".
2. The more correct way is to put a "Transfer Switch" between the house and the power grid. The house is on the common node and the switch first opens one feed (e.g. the power grid) and then connects the second feed (e.g. the generator). This is a much safer arrangement. There are likely some details here I left out, talk to your electrician or local electrical inspector. I am not an electrician.
3. Or, as someone said you could just feed generator power to your shed with a "Transfer Switch" between the house and the shed. In this case the shed would be the common node and the house (power grid) and generator would be the switched power sources. Your house would not benefit from the generator backup. Just make sure your "2-100 amp breakers" arrangement does not back feed to the house and the power grid.
Again, talk to your electrician or local electrical inspector. He will be able to make sure you meet any State and Local codes and implement all known safe practices. Paul

"but we are missing the starting basics - the transfer switch is designed so any dummy at all can't possibly have both the generator and the utility transformer ever connected to each other. Ever."

EXACTLY but who is we anyway??

Fun chat for us sparkies at least

John T

As others have said repeatedly, the short answer is "no".

I think some confusion arises as to what constitutes a transfer switch. There are two flavors: The simplest ones just replace the main service disconnect and switch the entire service. But the ones that ship with most generators and are sold at the big box stores are tied into the circuit breaker panel and only switch selected circuits. I don't care for the latter; they're complicated to install and typically limit the number of circuits you can use. I suppose the generator makers like them because they make it impossible to overload the generator. I prefer to choose for myself what I want to run.

At any rate, neither style of transfer switch will do what you want, because the intention of the transfer switch is precisely to prevent you from backfeeding the service.

You do not explain why you want to feed the house from the shed. Are you running your generator in the enclosed shed? Hmm...

(quoted from post at 20:40:18 10/05/14) I'm looking at getting a stationary standby generator. Here's my set up now. Our main electric comes into the house with the breaker panel in the basement. Off of this panel I feed our shed with 200 amp service (2-100 amp breakers). My question is. Can I hook the generator up to my shed with a transfer switch in the shed or does the transfer switch need to be in the house? I would think I can put it in the shed.
Right now I have an older 42 amp 11hp generator I plug into the breaker box in the shed and it backfeeds into the house and runs everything except the AC. I just have to flip the main breaker in the basement box first though.

Click to expand...

We all appreciate trying to save some money and the satisfaction of doing your own work.
As previously stated. It still stands that a proper break before make transfer switch is required to isolate the utility and connect to your generator.
Back feeders , in particular those who back feed 120/240 into a three prong welder plug . They need a good swift kick in the backside.

2510Paul, You put it in words best. I was looking at getting the generator as far from the house to keep noise down was my reason. Thanks for your input.

Just a question--why no Generac? I'm in the process of buying a generator to power my home in the case of emergency and a Generac 6500 is one I would consider. Are they bad?

Generac had some serious design errors and problems with product build quality.
The newer horizontal shaft systems today are better.
A primary problem with a majority of generator applications is that somebody chose too small of a generator.
Sometimes the buyer misses the fine print on the intermittent and continuous power ratings.
A 6500W continuous unit should not have more than 5000W continuous. 6500W load on a 650W generator is on the hair edge of meltdown.

I have looked at standby generators to do every thing at house and out bulding and the price they gave me included the installation and will cover all switches to be used.