Sizing generator transfer switch/panel?

[ManCave]

I'm going to be installing a transfer switch/panel for powering my home with a generator when the power goes out. Right now I only have about a 5500 watt generator. Eventually I may get a whole house generator. I'm trying to decide how large a transfer switch I should get. We have a huge house. Right now an 8-circuit switch would be plenty big. But what I don't want to do is install one that is too small and have to replace it later.

Just wondering how big you guys went with or what you might recommend as far as size?

 

[Provincial]

Whole house requires a switch that can handle the whole amperage of the commercial feed.

If you use a switching sub-panel then you can size the transfer for the amperage of the generator and limit the loads by choosing which circuits to run off the generator and putting those breakers in the sub-panel. Then feed the sub-panel with a breaker off the main panel that matches the capacity of the generator.

You can pick a switching sub-panel that can handle a greater amperage than the current generator, since the generator will be protected by it's on-board breaker. The wiring should be sized to match the maximum capacity of the sub-panel so you can upgrade to a larger generator later. The feed breaker from the main panel can be sized to match the maximum capacity of the sub-panel, since it only protects the wiring between the two.

 

[JordanPeter]

Can we use 8-circuit switch with 5500 watt generator? If yes then how can we do connect it?

 

[CJKaz]

I just installed this panel, ten breakers, 7.5kw, meters on each bus. Same size generator as yours. Includes exterior receptacle in a steel box. Prewired flex conduit goes
To your panel with clearly marked leads.

Very well made in the USA! Best price was at Home Depot online. Check Reliance's site for sizing, installation walk throughs.

http://www.reliancecontrols.com/ProductDetail.aspx?31410C

 

[nehog]

I just installed this panel, ten breakers, 7.5kw, meters on each bus. Same size generator as yours. Includes exterior receptacle in a steel box. Prewired flex conduit goes
To your panel with clearly marked leads.

Very well made in the USA! Best price was at Home Depot online. Check Reliance's site for sizing, installation walk throughs.

http://www.reliancecontrols.com/ProductDetail.aspx?31410C

I have two of these panels for my house (gives me 20 circuits).

What I'd recommend is determine the amperage of the main panel, and buy a transfer switch that size (or larger.) Harbor Freight has a C/H box that is rated at 200 amps, I suspect that would be large enough. Some day, when I upgrade my breaker box, I'll change over to that type of transfer switch.

 

[theoldwizard1]

If you have a pair of spare slots on your main panel you can feed your generator directly into 2 appropriately sized non-main breakers IF you have an interlock installed to prevent back feeding the power company's feed.

Some panel manufactures sell interlock kits. If you can't find a electrical supply house that will order it for you, check out this web site.

This type of system is easier and much cheaper to install than the typical transfer panel.


It does take a few "brain cells" to properly operate, but the benefit is, you get to "scale" it to the size of your generator at no additional cost !!!!

 

[CJKaz]

Very interesting solution. Basically what I did during a short outage before I had the transfer switch installed. Back fed through a wall receptacle, threw main to prevent back feed. Only ran the refrigerator for fear of overloading the wiring to the receptacle (15 amp) circuit.

 

[VHF]

Oh oh.

 

[SixStringMadness]

Very interesting solution. Basically what I did during a short outage before I had the transfer switch installed. Back fed through a wall receptacle, threw main to prevent back feed. Only ran the refrigerator for fear of overloading the wiring to the receptacle (15 amp) circuit.

 

[mooman]

 

[Jeff95TA]

If you have a pair of spare slots on your main panel you can feed your generator directly into 2 appropriately sized non-main breakers IF you have an interlock installed to prevent back feeding the power company's feed.

Some panel manufactures sell interlock kits. If you can't find a electrical supply house that will order it for you, check out this web site.

This type of system is easier and much cheaper to install than the typical transfer panel.


It does take a few "brain cells" to properly operate, but the benefit is, you get to "scale" it to the size of your generator at no additional cost !!!!

My power company said this was not an acceptable method. I ended up with the same 10-circuit transfer switch as the couple guys above.

If the OP is considering spending the money on a whole house generator, an automatic transfer switch might be the way to go for convenience.

 

[Alchymist]

Very interesting solution. Basically what I did during a short outage before I had the transfer switch installed. Back fed through a wall receptacle, threw main to prevent back feed. Only ran the refrigerator for fear of overloading the wiring to the receptacle (15 amp) circuit.

If you have a pair of spare slots on your main panel you can feed your generator directly into 2 appropriately sized non-main breakers IF you have an interlock installed to prevent back feeding the power company's feed.

Some panel manufactures sell interlock kits. If you can't find a electrical supply house that will order it for you, check out this web site.

This type of system is easier and much cheaper to install than the typical transfer panel.


It does take a few "brain cells" to properly operate, but the benefit is, you get to "scale" it to the size of your generator at no additional cost !!!!

Oh oh.

And AWAY WE GO! Wait, I forgot my popcorn.....

My power company said this was not an acceptable method. I ended up with the same 10-circuit transfer switch as the couple guys above.

If the OP is considering spending the money on a whole house generator, an automatic transfer switch might be the way to go for convenience.

Anyone wanting to use the interlock kit - check with your AHJ beforehand - many don't allow them.

 

[SixStringMadness]

my $0.02

If all I had was a 5500 watt generator. I'm assuming a pull start jobber, I would not be deeking around with any transfer switches. Too much effort. Roll out a few extension cords, and let it eat.

I would not get a transfer switch until I had a real, self starting genset that started and switched all on it's own.

If so, size the transfer switch to the genset you plan to buy, and even that may get replaced as the Home Depot gensets use a specific transfer switch I believe.

I've only installed the commercial 50-75kVA Caterpillar units, so forgive me if I sound cynical....

 

[theoldwizard1]

If all I had was a 5500 watt generator. I'm assuming a pull start jobber, I would not be deeking around with any transfer switches. Too much effort. Roll out a few extension cords, and let it eat.

Obviously you did not look at my link on breaker panel interlocks.

They are relatively inexpensive and easy to install. Best of all, they can be easily upgraded later by simply changing the breaker (assuming the proper size wiring is already in place).

 

[nehog]

...
If the OP is considering spending the money on a whole house generator, an automatic transfer switch might be the way to go for convenience.

...
I would not get a transfer switch until I had a real, self starting genset that started and switched all on it's own.

If so, size the transfer switch to the genset you plan to buy, and even that may get replaced as the Home Depot gensets use a specific transfer switch I believe. ...

Any automatic transfer switch, coupled with a self starting (automatic starting) backup power source falls under some serious NEC rules regarding size and capacity. For virtually all applications a simple, manual transfer switch is adequate.

(this has been discussed in depth in the past, some good threads on the topic...)

 

[pentavolvo]

interlock kit and proper sized breaker IMO is the easiest way to go

 

[willysrule]

interlock kit and proper sized breaker IMO is the easiest way to go

this way is NOT a "legal" way to hook up a generator according to my electric provider...they require an actual transfer switch.

 

[Stuart in MN]

this way is NOT a "legal" way to hook up a generator according to my electric provider...they require an actual transfer switch.

As mentioned above, some electric utilities allow them, but others don't. A person has to check first before buying one.

This is an article from Popular Mechanics that shows the step by step installation of a conventional manual transfer switch and generator panel, it's a pretty good reference for the work involved. Specific installations will vary depending on a person's individual needs and local regulations. http://ne.mara.net/generator/pm_gen_install.pdf

Here's another interesting product that installs between the meter and meter socket. http://www.generlink.com/about_generlink.cfm This is another device that's allowed in some areas but not in others, so check first before buying.

 

[Gregishome]

I remember back in the icestorm of 2003 here when the power was off at my house and thousands of others, for as long as 7 days. One could go out and here gas gen's running in peoples back yards everywhere. ..

The power crews came from 4 surrounding states to help us get re-energized from the ice pulling trees down across the power lines. The local stores would invite the linemen in and give them free hot coffee and snacks if, their store had power..

Then one day it happened, one of the linemen was attempting to hook up a secondary drop and it was energized and it nearly killed him. Someone out in the neighborhood somewhere, had back fed a generator in to their dryer/ranger outlet and forgot to turn off the main breaker.

Needless to say, I saw a lot of power company trucks stopping by and checking houses whenever they heard a gen running, before they would touch the power lines. DONT EVER BACK FEED GENS TO OUTLETS. Use automated/manual transfer equipment or just use extension cords !!!!!!!!!!

P.S. I looked at the interlock and dont like it. How does one know how many breakers they can turn on before their gen is overloaded ? What happens when the house is sold and the new owner takes it off cause he doesnt like it in the way ? Too many variables can happen to risk a lineman's life ..........

 

[theoldwizard1]

this way is NOT a "legal" way to hook up a generator according to my electric provider...they require an actual transfer switch.

Are you saying your power company ? They can not control what you do on your side of the meter, IF it has been passed by your local inspector and it meets standards.

Generator Interlock Technologies states, "Our kits are designed to be installed by qualified electrical personnel and meet the strict requirements of the National Electrical code and the National Fire Protection Code."

 

[Alchymist]

Are you saying your power company ? They can not control what you do on your side of the meter, IF it has been passed by your local inspector and it meets standards.

Generator Interlock Technologies states, "Our kits are designed to be installed by qualified electrical personnel and meet the strict requirements of the National Electrical code and the National Fire Protection Code."

3 comments here:
1) Perhaps they cannot "control" what you do on your side of the meter, but they can and will choose not to provide service if they deem your "installation" unsafe.

2) In this area, during an outage, if they see lights on, they investigate - if no proper transfer switch and generator is in any way connected to the service, (ie; not run on extension cord to individual appliance), they will cut the main drop and will not reconnect until the problem is corrected, and even then they are in no hurry to do so.

3) The Pope himself could have blessed a kit, but if the local AHJ says no, you don't get to use it. Just because it "meets the strict requirements of the National Electrical code and the National Fire Protection Code" doesn't mean local codes cannot prohibit it.

 

[SixStringMadness]

Obviously you did not look at my link on breaker panel interlocks.

They are relatively inexpensive and easy to install. Best of all, they can be easily upgraded later by simply changing the breaker (assuming the proper size wiring is already in place).

I didn't really need to. I offered my opinion based on field experience. I stand by my opinion.

The "interlock" has a few variables I would not allow in my home. Variables that require an effort not worth taking with a 5500 watt, pull start generator.

That's not to say you or the OP are more than welcome to use that equipment. It is simply my opinion to not do so. After several years installing generators and generator/UPS combos on a commercial level, I have good reason to stand behind my opinion.

Cheers to anyone who has the initiative to install transfer switches on their home pull start generators, they have more than me. , because I'd just roll out three 12AWG the extension cords, and plug stuff in.

 

[SixStringMadness]

Any automatic transfer switch, coupled with a self starting (automatic starting) backup power source falls under some serious NEC rules regarding size and capacity. For virtually all applications a simple, manual transfer switch is adequate.

(this has been discussed in depth in the past, some good threads on the topic...)

I certainly agree. Although, having seen both in action many times, and since I have an entire bookshelf of the applicable code books, the auto starts are worth the trouble and effort. Simply my opinion though.

 

[theoldwizard1]

3) The Pope himself could have blessed a kit, but if the local AHJ says no, you don't get to use it.

I concur 100% ! It has to be pass by your local building/electrical inspector.

1) Perhaps they cannot "control" what you do on your side of the meter, but they can and will choose not to provide service if they deem your "installation" unsafe

Legally, if your installation is passed by the local building/electrical inspector, the power company does not have a "leg to stand on".

 

[SixStringMadness]

Generator Interlock Technologies states, "Our kits are designed to be installed by qualified electrical personnel and meet the strict requirements of the National Electrical code and the National Fire Protection Code."

Statements like this are rather misleading. That could mean that it just doesn't violate any of the codes. It doesn't mean its approved for use. It would carry some weight with a UL listing instead.

Products are not listed with the NFPA, however with UL, they are listed with a specific application. For your interlock, maybe you'll find a UL 1004-4 or UL 1008 listing on it?. That means they have passed a series of strict tests based on multiple scenarios, and are approved for such specific uses. (and not approved for some another use, because carrying a UL label is not a free ticket to use for any and all applications, i.e.: Commercial vs Residential)

FYI, there is not a standard for "interlocks", so I doubt the one you are using is listed at all.

 

[SixStringMadness]

Legally, if your installation is passed by the local building/electrical inspector, the power company does not have a "leg to stand on".

Oh they most certainly do. They may not have the authority to show up, barge in and look around for rigged up worked, but if they are made aware of it somehow, you will be warned, given a time frame to comply, and if you don't comply, you'll come home to you're meter removed from the meter base. AND they most certainly have the authority to do so.

 

[bd8134]

I considered carefully what my options were after some extended power cuts. I can live without cooling, range, dryer, compressor or lift during those times, so a 120v generator will serve my needs. My house, in my eyes, is wired the most ridiculous way with lights and outlets on different floors shared throughout. I would need almost every fuse in my 30ish-way fuse panel switched on. That would require a large transfer switch and I am not re-wiring my house. I am not on a gas main. My propane tank is 100 gal but it might already be half empty.
I decided on a new larger consumer panel, I needed one anyway for some extra bathroom circuits. This unit is 40-way which had its own specially designed interlock switch from the same company. This is approved in MA. It was all installed by a licensed contractor and inspected by the town. I use 2 Honda gas powered, light (we are getting older), quiet and portable generators that are designed to be run in parallel which are hooked up to an approved generator box. It is not automatic but I can live with that.
We had one power cut since the instal and everything worked better than I had hoped. Lights for every room, heat, hot water, coffee maker, washing machine,etc. I could also still work in the garage, door openers etc. We had to be careful what we switched on simultaneously, I have not been able to find an amp or power meter that suites my needs.
If you set realistic or reduced expectations for what you need powered on during a power cut, you can minimize the size of generator needed and hence the noise output, amount of fuel for a bigger generator, work required to install, etc.
Your mileage may well be very different for your situation.
Check with your town as to what is approved.

 

[Jeff95TA]

Cheers to anyone who has the initiative to install transfer switches on their home pull start generators, they have more than me. , because I'd just roll out three 12AWG the extension cords, and plug stuff in.

I went the extension cord route once and it was kind of a mess. And my furnace is hard wired, which requires some unwiring. I think maybe I was just looking for an excuse to install the switch!

 

[nehog]

...
Cheers to anyone who has the initiative to install transfer switches on their home pull start generators, they have more than me. , because I'd just roll out three 12AWG the extension cords, and plug stuff in.

I tried this once... We got by (three days of getting by) but it was so sub-optimal that I quickly installed proper transfer switches. Now, when the power goes out, I plug in the generator, start it up, throw the transfer switches, and it is like we never lost power. Sure beats having a bunch of extension cords running around the house!

 

[SixStringMadness]

I tried this once... We got by (three days of getting by) but it was so sub-optimal that I quickly installed proper transfer switches. Now, when the power goes out, I plug in the generator, start it up, throw the transfer switches, and it is like we never lost power. Sure beats having a bunch of extension cords running around the house!

I guess I'd have to experience a long power outage, more than once for the pain of lugging power cords to be irritating enough to want to install the switch. Sounds like you experience multiple power outages.

Our power is pretty reliable and power outages are usually short around here. And long outages are usually rare for the folks that do experience them.

 

[pattenp]

this way is NOT a "legal" way to hook up a generator according to my electric provider...they require an actual transfer switch.

I'm in Chesterfield County which is south of Richmond VA and Chesterfield is rather tight on code requirements and they allow interlocks on the main panel for portable generators. So it goes to say "different strokes for different folks". Note: that is for portable generators.

 

[Alchymist]

I tried this once... We got by (three days of getting by) but it was so sub-optimal that I quickly installed proper transfer switches. Now, when the power goes out, I plug in the generator, start it up, throw the transfer switches, and it is like we never lost power. Sure beats having a bunch of extension cords running around the house!

So much easier to do it right:

 

[ManCave]

Thanks guys. Lots of good info. I decided to go with this transfer switch.

 

[Dusty Floor]

I have three reasons to have a transfer panel with my portable (pull or electric start) 6kW generator - furnace, well, and built-in refrigerator.

All three could be rigged to an extension cord with some hassle (the fridge has a regular plug, but requires removal of part of the cabinet to access it; the well is 240V and hardwired; furnaces are hardwired), but we've had two outages totaling 12 days in the past six months (after a total of about 72 hours of outages in the prior ten years), and the convenience of having the transfer panel more than paid for the cost of the installation.

I looked at the expense as an insurance policy against the damage a frozen house would sustain, and it turned out we would have had to move out during the second outage last year without heat (the temps were just above freezing, so damage wasn't an issue, but habitability certainly was).

 

[ahmedats]

I think you can find more about connecting a transfer switch to home generator at this site:
www.transferswitch4all.blogspot.com
Enjoy!

 

[theoldwizard1]

I think you can find more about connecting a transfer switch to home generator at this site:
www.transferswitch4all.blogspot.com
Enjoy!

That is but ONE type of "transfer switch". There are others, and this confuses most people and some electrician also !

 

[creativecars]

So much easier to do it right:

I take it the box on the right is for running the circuits durring a power loss?
What do you have for a breaker powering the other box? Assuming the wire at the bottom of the boxes is that transfer wire.

 

[Alchymist]

I take it the box on the right is for running the circuits durring a power loss?
What do you have for a breaker powering the other box? Assuming the wire at the bottom of the boxes is that transfer wire.

Main panel is 200 amp.; a 60 amp breaker feeds the transfer panel. (This breaker can be up to 100 amps). The wire at the bottom is indeed the feed - #6-3. The generator feed has yet to be installed in that picture.

Here's a link to the panel:
http://www.reliancecontrols.com/ProductDetail.aspx?TRC1006D

 

[creativecars]

Main panel is 200 amp.; a 60 amp breaker feeds the transfer panel. (This breaker can be up to 100 amps). The wire at the bottom is indeed the feed - #6-3. The generator feed has yet to be installed in that picture.

Here's a link to the panel:
http://www.reliancecontrols.com/ProductDetail.aspx?TRC1006D

Do you have any pics with the generator feed installed?

 

[Alchymist]

Do you have any pics with the generator feed installed?

Generator feed is simply another #6-3 from an outdoor plug in a waterproof box.