Backfeeding your electrical system

cobb

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I know this is dangerous and should not be done, but was just wondering if it could be done and how would it be done.

As I discovered in another thread, it could take 1500 watts or 2500 to start up my fridge from an inverter in case of a power failure to keep my food cold and or safe from spoiling.

For years I have often wondered after seeing grid tied inverters how hard it would be to back feed my hvac unit from another outlet in my apartment to just run the blower and gas electronics for emergency heat. It runs on 110 and seems to take next to nothing to run when comparing to my air conditioner function during the summer. I know during the y2k thing folks have said you can use a male to male 220 plug and plug one end into your generator and the other to your electric dryer or stove outlet after throwing the main breaker to not feed the lines down your street. Since I have a 110 system and a gas stove and hvac that wont be possible.

Seemed like it would be nice if I could throw the main breaker, leave the breakers on for the hvac and fridge and plug a large inverter into an outlet on that circuit and make those appliances run off of a battery or two from one of my wheelchairs or a bank.
 

Lynx_Arc

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probably the best thing to do is have an electrician rewire your breaker box and put all the items you want to run off alternative power on a seperate set of circuits that you can disconnect from the main feed and connect to the alternative feed, inverter, generator etc.
 

gadget_lover

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They make something called a "transfer switch" that can be wired in line with your main box or in line with the few branches you want powered by the inverter. It's built in such a way that the wiring is only hooked to the inverter or the mains, but not both at any particular time.

Some transfer switches are automatic, in that they transfer to the backup when power from the utility is disrupted.

If you ever use the 220 dryer trick and do it wrong, you could kill a power company worker or cause a fire. Neither are worth it when a $100 transfer switch is almost as easy AND it is less likely to electrocute you too.

Daniel
 

wmirag

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Nov 22, 2004
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Safety is the first concern so do it right.

Transfer switches are good but expensive and RIGID. By that, I mean only what is wired into the transfer switch can be powered. There is a more flexible, cheaper, AND still safe alternative that allows you to power ANY circuit in your home by using your breaker box.

This thing is installed by your utility under your meter. It has a male 240V plug for your generator or other source of 240VAC. It disconnects you from the grid and powers your entire breaker box from the alternate source. Obviously you need to ration the circuits that are on at the same time. But with a decent power source, you can alternately power almost anything in your house.

http://www.globalpowerproducts.com/generlink.html

My utility doesn't install it, but many utilities do. They charge you next to nothing to install it but they charge a small lease fee every month.

W.
 

James S

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you cannot do it that way at all. The electric company is VERY hard on people that rig this stuff up, If they catch you doing that they will just disconnect you. Even if you remember to turn off the main breakers and everything, it's against the rules and if you forget and you kill a lineman thats murder.

As unlikely as that is to happen, still don't do it.

However, there is a very easy alternative solution. Have the furnace put on a plug! I've done that with all my air handlers so that I could run them through a line filter as they make so much electrical noise that they mess up other equipment that I've got.

What you want to do is replace the junction box where they are wired with a high quality 15 am outlet (there may be one there already as that is the new code) and then just disconnect the directly connected romex that probably leads to the furnace with a good quality 15 am plug. Then when the power goes out you can run an extension cord to the attic or closet, and just plug the furnace air handler into that. Obviously this wont work to power electric heat strips, but if you have a gas furnace and enough power to start the blower, it will work perfectly and be safe and not expensive and even can live up to code in most places where having a plug on an appliance is not against the rules.
 

Chris_Medico

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Sep 23, 2004
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Central, North Carolina
[ QUOTE ]
wmirag said:
Safety is the first concern so do it right.

Transfer switches are good but expensive and RIGID. By that, I mean only what is wired into the transfer switch can be powered. There is a more flexible, cheaper, AND still safe alternative that allows you to power ANY circuit in your home by using your breaker box.

This thing is installed by your utility under your meter. It has a male 240V plug for your generator or other source of 240VAC. It disconnects you from the grid and powers your entire breaker box from the alternate source. Obviously you need to ration the circuits that are on at the same time. But with a decent power source, you can alternately power almost anything in your house.

http://www.globalpowerproducts.com/generlink.html

My utility doesn't install it, but many utilities do. They charge you next to nothing to install it but they charge a small lease fee every month.

W.

[/ QUOTE ]

This is a very interesting product. I wonder how many utility companies would approve it being installed....

Hm....

Chris
 

CNC Dan

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boston area
[ QUOTE ]
wmirag said:

Transfer switches are good but expensive and RIGID. By that, I mean only what is wired into the transfer switch can be powered. There is a more flexible, cheaper, AND still safe alternative that allows you to power ANY circuit in your home by using your breaker box.

This thing is installed by your utility under your meter. It has a male 240V plug for your generator or other source of 240VAC. It disconnects you from the grid and powers your entire breaker box from the alternate source.W.

[/ QUOTE ]

It's still a transfer switch. It just does the entire electrical service. I would imagine it might be cheaper than the ones with the individual switches.
 

wmirag

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[ QUOTE ]
CNC Dan said:

It's still a transfer switch. It just does the entire electrical service. I would imagine it might be cheaper than the ones with the individual switches.

[/ QUOTE ]

Yes, it's a transfer switch, but quite out of the ordinary.

It is much cheaper and less intrusive i.e. no extra box, wire fishing, etc. And besides the flexibility, there is the issue of subpanels. All the residential tansfer switches I've seen are limited to 30A branch circuits. I have a 100A subpanel to my basement. Even though none of the circuits down there are larger than 30A. So I simply cannot do with a traditional transfer switch arrangement because I'd have to rewire the basement with individual circuits, VERY impractical and expensive from where my main panel is.

But this Generlink thing WOULD work if I turned off most of the circuits in my subpanel in favor of JUST the well, or JUST the air handler, assuming a good 5KW generator.

But, as I said, Con Edison doesn't install these so I store 100 gallons of water and a cord of firewood for when we lose power. And I use a little Honda 2000i generator to keep my office, the kids' TV, and a few lights going.
 

Pydpiper

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I have backfed /ubbthreads/images/graemlins/jpshakehead.gif
I have done it in a way that is safe though, as safe as it gets. I use a padlock system that allows me to only engage power while the main breaker is off.
There is also a "home made" version on the internet that utilizes an array of SPST switches, a bit complicated for someone with minimal electrical experience though.

As for the furnace, make sure you turn the switch so the fan remains on, a fan uses very little power, but the "start up" power requirements are huge. Once it is running it will be fine. Fridges too, be careful with those, if you do not have enough power to run them at full current you will most likly damage them, the motors will remain in a state of being partially powered and heat will build.
Home Depot carries a full line of equiptment to ensure you stay safe and keep the people around you safe as well.
 

cobb

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THanks. I like the plug idea. The hvac has a switch and box in the closet where it is located and that switch also switches it off and on like the breaker does. I know as I had the filter door come off and it was sucking the exhaust into my apartment. I was unable to throw the breaker and turning the thermostat did nothing as its delayed. I doubt it would be too hard to get a licenses electrician to wire up the plug.
 

yuandrew

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Apr 12, 2003
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Chino Hills, CA
The plug idea is good but it depends on your codes. In some areas, you can have your furnace connected by cord but other areas require things such as furnaces, garbage disposals, and garage doors to be hardwired

My furnace was installed using the plug method when the house was built but most new construction in my area have it hardwired with a light switch nearby to disconnect for service.

furnaceplug.jpg


Of course, you can always get a Gen-Tran www.gen-tran.com and eliminate the extension cords connecting your appliances to your generator but even some linemen for my power company say "don't hook up your generator at all to your house; transfer switch or not" and even someone told me transfer switches are still dangerous as most don't break the netural going out.

How can you get backfeed through a netural wire?

(I know if you connected the hot and netural wires backwards it can do that but it should be safe if installed properly)
 

rwolff

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Dec 22, 2004
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Location
Ontario, CA
[ QUOTE ]

How can you get backfeed through a netural wire?


[/ QUOTE ]

Assume the generator has its neutral terminal grounded. If it's a 120V generator (only serves one side of the panel), or a 240V where the load is unbalanced, and you have a bad connection somewhere between the panel neutral and the generator neutral, you will build up a voltage on the panel neutral. This is due to the current drawn through the resistance of the bad connection. Enough of that on a transfer switch that doesn't break the neutral will pose a danger to linemen.
 
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