proper generator hookup 5

[jarvis]

I posted a topic last week about hooking up a small generator for emergency use. I asked about meters turning backwards and syncronizing to line. I recieved some nice responses telling me the meter cannot run backwards and that the generator usually synchronizes itself to the line. I also received a post which was very angry. I responded nicely last night and I've been thinking about it since. I needed to give more of a response. Upon logging in and looking for the topic, it has now apparently been erased for whatever reason.

I do not wish my fellow man harm and am not to my knowledge considered "ignorant" until the angry man informed me that I was. If I have done something that is unsafe or illegal, I welcome peoples constructive criticism as long as they inform me as to how I can correct the situation. The angly man offered no alternative method, only anger. He was ranting and raving about how I was doing something illegal and unsafe and should be charged a million dollars for it. If he reads this I ask him if he as ever drove over the speed limit, crossed a white line, passed on the shoulder, drove with a light out, let his tires wear too much, or forgot to use his signal. ALL these things are against the law and could easily result in the death of many unsuspecting people. If he can honestly tell me he has never done anything illegal or unsafe, than I will admit to being "ignorant".

With that out of the way, I would like to ask what is the proper way to hookup a small emergency generator(4400 watt manual start)so that it only runs the critical systems and not every circuit.

Ben Englund

 

[enginebob]

The proper way is to install the special transfer switch.
Most places that sell the generators will have them.
It amounts to a series of single pole double throw switches, that have the circuit at the center pole, and the line on one end and the generator on the other end. These special transfer switches also have one or so double pole double throw switches so the generator can also power up an electric water heater or stove burner. And what you do is simply switch on or off the circuits you wish to use.
If you inadvertantly switch to the line position (with a power outage) the circuit is hooked to the dead line. No generator power is transfered to the line. Do a search for transfer switches, that should help.

 

[alehman]

One way is to use an approved transfer switch. It doesn't have to be automatic. You would need to arrange a sub-feed breaker in your incomming utility power panel to one input of the transfer switch and connect the generator to the other input. Then feed your branch circuits (via another panel) from the output.

http://www.kohlerpowersystems.com/residential_transfer.html

http://www.eatonelectrical.com/unsecure/cms1/TB00800001E.PDF

page 8-26

 

[chuckhydro]

"Home Power" magazine may have some good articles that apply to what you want to do. It has a search engine on the web page. Try the following link:

http://www.homepower.com/

 

[aegcmac]

You do have to isolate your critical circuits if the generator can't power the whole house. If you don't isolate them into a sub-panel, even with a transfer switch, whether auto or manual you'll potentially have loads on in the rest of the house that you can't run simultaneously with a 4400 watt generator. Or, you have to insure you turn off all the loads it can't handle before you start it. So if the generator can't handle everything at the same time, then you should isolate the critical loads into a sub-panel. Then you can install a manual or auto-transfer switch for either the generator or the utility to power this dedicated sub-panel. If manual, and you don't quickly bypass the generator once the grid is restored, then at least you won't be back feeding into the grid. The generator will run the sub-panel until you manually change it back to the grid. If auto-transfer, then your generator will run until you turn it off, but it won't be powering anything, just running.

 

[aegcmac]

Follow up:
If you're in the U.S., this company sells inexpensive, reliable relay-based auto transfer switches for smaller 120/240 Vac applications like yours. They even have a 30 to 60 second delay so your generator warms up before the transfer occurs.

http://www.solar4power.com/solar-power-transfer-switches.html

Generator company or after market add-on auto-transfer units tend to be much more expensive.

 

[jbartos]

Suggestion: The manual operation will always have a human error possibility involved. Therefore to avoid it, there are automatic transfer switches developed and applied.
To operate everything manually, the following should be a part of the rigid procedure, if applicable (see comment below):
1. The service switch or circuit breaker has to be turned off when the utility power is lost.
2. The load shedding should be performed by turning off circuit breakers or removing fuses.
3. The generator started.
4. The manual transfer switch transferred to the generator supply.
5. Selected loads turned on by circuit breaker or by fuses.
6. Etc.
The reverse procedure to restore the normal service supply should include:
1. Turning off the generator by the transfer switch.
2. Turn on the Service switch.
3. Turn on circuit breakers and or insert fuses that were not on during the generator power supply.
4. Etc.
Nowadays, an average electrical contractor can install the emergency power supply system. It is a very straightforward construction.

A big difference is where this generator will be applied. Specifically, whether it is for a private family house or for a commercially classified building subject to various bylaws.

 

[jarvis]

THANKS GUYS it sounds like I'll have to look into transfer switches and purchase the nesassery equipment. You guys have been very helpful. According to the solar4power website that aegcmac posted, we might be able to do it for 100 bucks or so. It seems common practice around here to hook up generators directly through breakers around here, but now I know the right way is not all that expensive.

Ben Englund

 

[CJFlatters]

Jarvis

Sorry to hear about Mr Angry - at least it sounds like you have found some good constructive advice above, I think I would follow the auto-transfer option above.

The time delay feature is worth having to give the set chance to run up to speed before being loaded.

_______________________________________
Regards -

Colin J Flatters
Consulting Engineer & Project Manager