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A couple friends are looking for double throw safety switches to use with standby generators this winter. Are these things $300???? Anyone have a good source for them or have ideas on how to do this without sopending $300. I thought these were about $100. Any advice apreciated.
$300 is a fair price. Spend the money, this is designed to do a specific task safely. There are cheaper ways of doing this but when you look at the big picture $300 is cheap compared to a new house. I have heard stories of people backfeeding and not tripping the main on the load center. When the power came back on there was an explosion. But we are in the business and $300 is a good price for a 200 amp transfer switch.
Are they looking to supply the full 200 amps with a standby generator? Most of these installations are for temporary power to a few circuits. My standby generator is a 12KVA unit that only feeds a few critical circuits. I paid about $100 for a 240v/60amp transfer switch from Northern Tool. Now that $100 is just the transfer switch. It doesn't include the separate subpanel/load center housing those "critical circuits". If you/they are looking for a complete load center including the transfer switch, the $300 figure is in the right ballpark.
They are wanting to use it to switch between the normal service and the generator so that there is no way the two can be on at teh same time. That would require the capacity for the standard 200amp service as the minimum correct?
I am not a licensed electrician and only have minimal knowledge of electrical code requirements, so take the following with a large grain of salt. If you keep that in mind, I'll say that from a practical standpoint, it shouldn't require a transfer switch that large to accomplish the purpose.Quote:
Originally Posted by Mike Heidrick
The way mine is wired in, there is a small subpanel that contains the circuits that need to be powered by the standby generator. Under normal circumstances that subpanel is fed by the main panel through a breaker sized to the subpanel requirements - 240v/60a in my case. That breaker feeds one side of the transfer switch. The standby generator feeds the other side of the transfer switch. Output from the transfer switch feeds the subpanel bus and is connected either to the utility power or the generator depending on the position of the transfer switch. That way, backfeed from the generator to the main power lines is prevented and the transfer switch doesn't have to be any greater capacity than the breaker in the main panel.
I believe you will find the units in the link I posted - the ones that are more than just a bare transfer switch - to be configured as a subpanel like I described above.
If you want to use just a single bare transfer switch, then yes, you will need one capable of feeding the entire panel. The main 200amp feed from the utility company will have to be moved from the main panel to one side of the transfer switch. Output from the transfer switch will then go the 200amp main panel. The other side of the transfer switch will be fed by the generator.
I strongly discourage wiring it such that the generator powers the entire main panel, even if that should meet codes. There is a large potential for trouble and/or damage to electrical devices in the house if the standby generator is too small to supply the potential load from the entire house.
Mike,
What Tom is saying is correct. A couple other points to consider.. if you get a stand alone stand-by (one that is on a pad outside your house) they will most likely come with a emergency circuit sub panel. If you are trying to use a portable type you can purchase a subpanel designed for that purpose. The main on that panel has two positions depending on where the power is coming from. Most are 60 amp but I have seen 100 amp also. They will run $100-$200 for the 60 amp depending on what and where you buy. If you use this type of set up you will also need to have a port on where to plug your portable in. You will need a flanged inlet rated for the 60 amps. This is basically a male plug recessed into a hole. You can also get them rated at 100 amps but those are monsters to work with as well as being very costly. As with Tom I am NOT an electrician. I do work in the trade selling this stuff. My best advise is think through what you want to do and then call an eletrical inspector in your area. If they are like ours, they will be happy to help and keep you out of trouble.