Transfer Switch

[bchauvette]

I going to be hooking up my MEP-003A as stand-by and to run the three phase stuff that cane with the M944A1. Transfer switches cost over $300.00 and the enclosres are huge. Why is that? I can buy a Chinese double pole single throw knife switch for under a hundred dollars. What kind of enclosure do I need to be compliant?

 

[R Racing]

Not sure where you are putting the switch. But if it were out in the weather. Most enclosure are nema 14 for being water proof . If inside I'd use a frankinstin switch.

 

[PeterD]

I've got a transfer switch that is three phase... Drop me a PM and I can shoot pictures of it. The enclosure is big but that's because the switch's computer board is big (it supports a lot of functionality such as automatic startup/shutdown, automatic test mode (with an optional timer). But the actual transfer switch part is not that large, and would give you an idea of what sizes are, and what box requirements should you mount something like this without the controller board (the controller board is not needed, either if you don't need automatic transfer.)

 

[steelandcanvas]

You may want to look into this design. I installed this a few months back, and am very happy with the functionality, design and price.

http://natramelec.com/

 

[TurboJoe]

Are you looking for an automated transfer switch, or a manual one?

A lot of the automated ones are close transfer (as opposed to closed) where they sync up and transfer load back to the grid when power is up for x amount of time. They do this with in one or two cycles so there is minimal interruption to power on the way back up. If you are looking for just a manual transfer switch then there are many options out there for well under 300 dollars. Keep in mind you will need to match the current rating of the main panel if you are transferring the whole house.

Manual transfer switches are not knife switches either. The ones I have seen are spring switches that take a full movement of the handle to load up a spring mechanism then it releases and the switch snaps to the other location. This avoids dragging an arc out if you are transferring into load. If you used a knife switch you would have to have the breakers before or after it off to avoid draggin and arc and making a boom.

Edit: There appear to be some double breakers, mechanical lock out type transfer panels out there economically. These would work also.

 

[Isaac-1]

The size of most transfer switches is caused by the NEC rules on things like bending radius of the largest size wire they are rated for, etc. Remember unlike breaker boxes these tend to have large wire not just feeding in once, but feeding in twice, and out once (assuming large generator that is sized similar to service feed coming in). Also those small Chinese knife switches are likely not themselves NEC rated, and probably don't have snap actions.

 

[bchauvette]

The size of most transfer switches is caused by the NEC rules on things like bending radius of the largest size wire they are rated for, etc. Remember unlike breaker boxes these tend to have large wire not just feeding in once, but feeding in twice, and out once (assuming large generator that is sized similar to service feed coming in). Also those small Chinese knife switches are likely not themselves NEC rated, and probably don't have snap actions.

Excellent!!

P.S. Exact likeness of myself

 

[rustystud]

Are you looking for an automated transfer switch, or a manual one?

A lot of the automated ones are close transfer (as opposed to closed) where they sync up and transfer load back to the grid when power is up for x amount of time. They do this with in one or two cycles so there is minimal interruption to power on the way back up. If you are looking for just a manual transfer switch then there are many options out there for well under 300 dollars. Keep in mind you will need to match the current rating of the main panel if you are transferring the whole house.
Manual transfer switches are not knife switches either. The ones I have seen are spring switches that take a full movement of the handle to load up a spring mechanism then it releases and the switch snaps to the other location. This avoids dragging an arc out if you are transferring into load. If you used a knife switch you would have to have the breakers before or after it off to avoid draggin and arc and making a boom.

Edit: There appear to be some double breakers, mechanical lock out type transfer panels out there economically. These would work also.

My switch is a knife style and they work just fine. One set switches from the two generators ( MEP-002A to MEP-003A ) and the other switches from Public Power to the generators. No boom and I've been using this set-up for 2 years now with on average 7 times a year of power failures, usually lasting over 12 hours.

 

[TurboJoe]

View attachment 503354View attachment 503355View attachment 503356

My switch is a knife style and they work just fine. One set switches from the two generators ( MEP-002A to MEP-003A ) and the other switches from Public Power to the generators. No boom and I've been using this set-up for 2 years now with on average 7 times a year of power failures, usually lasting over 12 hours.

I don't doubt you that it would work, I even said it would. I will say I bet you have not tried to switch that switch into or out of a load. Thats all I'm saying. Everyone should know the limitations or benefits of certain switches. Never operate a knife switch under load.

 

[rustystud]

I don't doubt you that it would work, I even said it would. I will say I bet you have not tried to switch that switch into or out of a load. Thats all I'm saying. Everyone should know the limitations or benefits of certain switches. Never operate a knife switch under load.

When the power comes on I switch from the generator to the Puget power supply, so yes I switch under load. No problem.

 

[TurboJoe]

How do you do that? Do you just leave everything up and running, then move the lever in the knife switch to the other position?

 

[bchauvette]

Chinese knife switch on Flee-Bay. 200 amp, 4 pole. $65.00. Obviously not snap lock. Absolutely must be enclosed. I'm thinking that the enclosure on an inside application is to contain any arching. If I configure so there is no wire bends inside the enclosure would a much smaller enclosure be OK. Fabricating an outside the enclosure lever would be no problem. Bet I could fabricate a snap lock device to.

We seem to be in a snap non-snap loaded transfer discussion. I would try and transfer no load but I have been known to forget.

B.T.W. Don't even know if my MEP-003A runs yet!!! That Honey-Do list is killing me.

 

[rustystud]

How do you do that? Do you just leave everything up and running, then move the lever in the knife switch to the other position?

Yes, that is exactly what I do. I'm sure if I was in a high amp situation I might experience some arcing, but I'm at most switching only 50 amps.

 

[ctfjr]

View attachment 503354View attachment 503355View attachment 503356

My switch is a knife style and they work just fine. One set switches from the two generators ( MEP-002A to MEP-003A ) and the other switches from Public Power to the generators. No boom and I've been using this set-up for 2 years now with on average 7 times a year of power failures, usually lasting over 12 hours.

Good post! I have a 400 amp single phase service coming into my house. I found a 400 amp 3 phase 'knife switch' like the one you posted the pix of rustystud. I picked it up new on ebay for $300. The wiring back to the 400 house box was a bear - I ended up having an electrician do that. I wired #2 wire back to the generator.
In the first pix I mounted it to the wall & used an old speaker to support it while I drilled 3/8 bolts into the concrete - its a big mother, that level is 2' long.

 

[PeterD]

http://imgur.com/a/P9gzV#4 and I wonder how SS will handle an imgur album! I may have to redo this, I'm not sure. Oh, well no preview. Anyway these are five pictures of a 3-phase automatic transfer switch. Before anyone says: yes, there is a key zip tied to the switch inside!

 

[steelandcanvas]

Not sure where you are putting the switch. But if it were out in the weather. Most enclosure are nema 14 for being water proof . If inside I'd use a frankinstin switch.

NEMA 14 is not an enclosure rating, you may have meant NEMA 4 or 4X. NEMA 3R would be sufficient enough for an outside location, provided it won't be pressure washed down for sanitary reasons.

 

[rustystud]

http://imgur.com/a/P9gzV#4 and I wonder how SS will handle an imgur album! I may have to redo this, I'm not sure. Oh, well no preview. Anyway these are five pictures of a 3-phase automatic transfer switch. Before anyone says: yes, there is a key zip tied to the switch inside!

Nice unit ! Looks like there only asking $200.00 . That's a steal for an automatic transfer switch !

 

[rustystud]

Good post! I have a 400 amp single phase service coming into my house. I found a 400 amp 3 phase 'knife switch' like the one you posted the pix of rustystud. I picked it up new on ebay for $300. The wiring back to the 400 house box was a bear - I ended up having an electrician do that. I wired #2 wire back to the generator.
In the first pix I mounted it to the wall & used an old speaker to support it while I drilled 3/8 bolts into the concrete - its a big mother, that level is 2' long.
View attachment 503719

View attachment 503720

Looks like you got yourself a good unit too ! It's fun drilling into the concrete and keeping the holes aligned with the cabinet isn't it !

 

[PeterD]

Nice unit ! Looks like there only asking $200.00 . That's a steal for an automatic transfer switch !

I'll sell it for that $200 too... Buyer can either pickup or arrange shipping, but I would be willing to bolt it to a pallet. The actual transfer switch is not that large (see the third picture) if someone wants that I'll be glad to take it out and ship it.

I got it to use with my MEP-004, but after all my health problems I've decided to re-prioritize and will use my existing transfer switches. They work, and in fact I just freed up a couple of breakers in them for additional circuits in the house.

 

[TurboJoe]

If I was looking for a transfer switch I'd buy that for 200 dollars in a heart beat. Nothing beats the correct way to do the job. I have the full GE zenith control panel at my shop, as well as at my mom's house. But they are approx $1800 or so at my cost.

You may be ok at low amps and a knife switch, but I cringe thinking about that. I've seen enough arc flash damage and explosions in my line of work. It is relatively low voltage, and low load.. but I would never ever transfer a knife switch into load myself. I suppose going into the load would not be as bad as breaking the load, but still not a fan.