Transfer Switch

MattM

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I bought a 40KW Muti-Quip diesel generator for emergency use. Now I need to get a 400 amp manual transfer switch.

I've been doing some research on the web but thought to ask for advice here.
 
If I may ask, why do you need a 400 amp transfer switch? Will you be using it to switch over to the generator from a 400 amp utility service? That's an awful lot of current for hobby machines, but to each his own. :)

Tom
 
Good question. That 400 amps supplies our entire house. I know it is way overkill but I got a good deal on an almost new genset. With the 40kw it can be wired directly into the main service box, no need to select individual circuits. The electrician said it would be a lot less expensive to wire.
 
so if your current house is 200amp, then you only need a 200 amp transfer switch.
All you need is a lockout type switch.
 
I have installed a few generators, and also considered one for my current house. I agree with Matt, it is much easier to have a generator big enough for the whole house load, rather than have separate breakout circuits in a sub panel that are handled by the generator. The transfer switch needs to be sized for the whole hose load. Older panels/houses were often 200A, newer house (larger) house tend to have higher amperage panels, my house service entrance is designed with a 200A main panel and an additional 100A breaker can be added if needed so I would need a 300A transfer switch. So the problem is that 200A automatic transfer switches are fairly common and they run $600-700. These are usually automatic type so they have a genset exerciser, sense line drop outs and also wait a specified time before before transfer back to house power and then have a cool down period for the generator. The common brands are Kohler, Honeywell, ASCO, Eaton, Winco, Generac, etc.. A manual transfer switch runs about $400. So at the 200A level it probably pays to go with an automatic. But above 200A the price of the automatic transfer switches in the 300-400A are 2-3X more expensive than the 200A. A manual 300-400A switch runs about $800, more if for a service entrance. If you cannot breakout the power after your main house breaker then you need a service entrance rated transfer switch and UL approved, which is very pricey. My last house I was able to put the transfer switch after the main house breaker, but many service entrance panels the main breaker is incorporated into the mains panel and you then need to use a service entrance transfer switch which is much more expensive. Not to be pessimistic, but if the panel is not rated correctly or is wired wrong and something happens, your insurance can deny coverage.

I would go with a transfer switch sized to your current main panel, a 400A is way overkill unless you have a large shop or heavy equipment, in witch case you would be better to just take care of the house power. A 200A transfer switch would be adequate for a 40kW genset. As far as what I recommend, the first 4 brands above, Generac is somewhat iffy in my experience. I would get the correct sized transfer switch and you need to determine if it can be installed, and if you need a service entrance type. At 200A, I would go with an automatic switch if the genset can be wired for auto start. The automatic systems also have sensors for things like low oil, overspeed/under speed, etc.
 
I have installed a few generators, and also considered one for my current house. I agree with Matt, it is much easier to have a generator big enough for the whole house load, rather than have separate breakout circuits in a sub panel that are handled by the generator. The transfer switch needs to be sized for the whole hose load. Older panels/houses were often 200A, newer house (larger) house tend to have higher amperage panels, my house service entrance is designed with a 200A main panel and an additional 100A breaker can be added if needed so I would need a 300A transfer switch. So the problem is that 200A automatic transfer switches are fairly common and they run $600-700. These are usually automatic type so they have a genset exerciser, sense line drop outs and also wait a specified time before before transfer back to house power and then have a cool down period for the generator. The common brands are Kohler, Honeywell, ASCO, Eaton, Winco, Generac, etc.. A manual transfer switch runs about $400. So at the 200A level it probably pays to go with an automatic. But above 200A the price of the automatic transfer switches in the 300-400A are 2-3X more expensive than the 200A. A manual 300-400A switch runs about $800, more if for a service entrance. If you cannot breakout the power after your main house breaker then you need a service entrance rated transfer switch and UL approved, which is very pricey. My last house I was able to put the transfer switch after the main house breaker, but many service entrance panels the main breaker is incorporated into the mains panel and you then need to use a service entrance transfer switch which is much more expensive. Not to be pessimistic, but if the panel is not rated correctly or is wired wrong and something happens, your insurance can deny coverage.

I would go with a transfer switch sized to your current main panel, a 400A is way overkill unless you have a large shop or heavy equipment, in witch case you would be better to just take care of the house power. A 200A transfer switch would be adequate for a 40kW genset. As far as what I recommend, the first 4 brands above, Generac is somewhat iffy in my experience. I would get the correct sized transfer switch and you need to determine if it can be installed, and if you need a service entrance type. At 200A, I would go with an automatic switch if the genset can be wired for auto start. The automatic systems also have sensors for things like low oil, overspeed/under speed, etc.
 
Very helpful.

The house has 400amps incoming which is split into two 200 amp sub panels. The sub panels (which are 90% full) are some distance from the genset. The genset is close to the main service entrance. We certainly don't need all 400 amps anytime much less in an outage.

I'm thinking in the case of an outage (or once a month) to light up everything and put a healthy load on the genset. Having had boats with diesels and having owned a marine diesel rebuild company I know diesels like to run hot and under load.

Like I said this is way overkill.
 
Matt i would suggest visit couple of scrap yards that buy industrial machines, and i would suggest find switch with two positions, 0,1,2 so you can switch between city power and generator power, i also own an 30 kw diesel generator i only have 100 a three phase 380 v selector switch.
 
Matt i would suggest visit couple of scrap yards that buy industrial machines, and i would suggest find switch with two positions, 0,1,2 so you can switch between city power and generator power, i also own an 30 kw diesel generator i only have 100 a three phase 380 v selector switch.

Can't do that. Must be a "legal" "approved" unit before a licensed electrician will install it and I'm not at all comfortable working around 400amps.

I did however install such a switch on an off-grid system but I was only dealing with 6.5kw and 30amps. Out there we, "Didn't need no stinkin permits" (or licensed electricians).
 
Can't do that. Must be a "legal" "approved"
Matt if you are thinking of investing you'll do it right anyway, no one wants to burn their house down with bad wiring, i know this is a very common with the solar systems installations now, here in europe the power company only cares that the power must pass thru the meter what you do with it, they really don't care, i have a main breaker and an selector switch, in the beginning i use to disconnect the main breaker and simply plug in my generator in the three phase socket in my garage, this is not wise because the automatic fuse are not made to work backwards but the generator has its own fuses.
 
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