MEP-004a 15kw rewired 1 phase, connecting to home. Transfer Switch Question/Advice

[GiftedFaithful]

Ok, so the epic saga of Generator n00b is still under way. I am closing in on completed though, as we test out just as we should post modification:

L1-l0 120v
L3-l0 120v
L1-L3 240v
(L1-L3 being hot. L0 being neutral) For any who might not know!

So now then, the way I had been doing it was by killing my main supply breaker (from power company) and then flipping on my welding plug breaker, I had a double male ended plug i would put in the old generator and the other end in the welding plug. Power was had.

Now I want to do it a little more "correct"/safe etc as I may not be the one doing it and dont want anyone or anything to be harmed. So I am looking at auto (or manual) transfer switches? What would be a good size to handle this mep-004a? Any ideas?

 

[sewerzuk]

So now then, the way I had been doing it was by killing my main supply breaker (from power company) and then flipping on my welding plug breaker, I had a double male ended plug i would put in the old generator and the other end in the welding plug. Power was had.

Now I want to do it a little more "correct"/safe etc as I may not be the one doing it and dont want anyone or anything to be harmed. So I am looking at auto (or manual) transfer switches? What would be a good size to handle this mep-004a? Any ideas?

Glad you are planning on doing it the right way; while I realize that there are likely thousands of people powering their house this way, one little mistake can literally put thousands of volts on the high voltage lines outside your house. The fact that the power is out and you need the generator to power your house means that linemen and/or firefighters are dealing with down lines. That little mistake can easily electrocute somebody...and, as I firefighter, I don't want that to be me or one of my guys!!!

Here is what I have been installing lately; easiest/cheapest/best way, in my opinion. It is a kit to interlock your gen inlet breaker with the main breaker so that they cannot both be closed at the same time:
Generator InterLock Kit
This is easy enough for a skilled DIY'er to do...however, you are limited to the largest breaker that you can get for your panel. For your MEP-004a, a 60A breaker would be ideal...

Another option is a main power transfer panel; I installed these on both my house and shop services when I built them:
http://www.harborfreight.com/100-amp-generator-manual-transfer-switch-42162.html
(The ones I used were 200A versions of this panel). This is both more expensive and more involved...however, you can transfer over your entire service this way and are only limited by the size cable and power inlet box you use when you install it.

 

[ctfjr]

I think the transfer switch is the way to go. I have multiple circuit breaker boxes located on opposite sides of my house so I couldn't easily isolate just those circuits I wanted to power from the generator. Having a 400 amp service meant getting a 400 amp transfer switch. With a little patience I found a brand new Square D on ebay & snagged it for $300.

Here are a couple of pix of the switch while I was installing it. I found an old speaker that was the perfect height to set it on while I screwed it into the wall (the bugger weighed over 100 lbs). The other pix is of the conduits between my CT box and the switch. Sorry about the quality, it was the best my phone camera could do in low light.

 

[sewerzuk]

I have multiple circuit breaker boxes located on opposite sides of my house so I couldn't easily isolate just those circuits I wanted to power from the generator. Having a 400 amp service meant getting a 400 amp transfer switch. With a little patience I found a brand new Square D on ebay & snagged it for $300.

If your sub panels are fed from the main panel, the interlock kit still works nicely, as you can still power everything from that one panel. This is fairly common in residential systems.
In your case, however...power may split off from inside of the CT box, making the transfer switch the way to go (that would be the only way to power all of the panels without doing multiple interlocks and power inlets). Not TOO many people will have a 400A service that they need to feed though! You must have a lot of electrical loads in your house!

 

[ctfjr]

Not TOO many people will have a 400A service that they need to feed though! You must have a lot of electrical loads in your house!

actually no, there is a fairly 'normal' electrical load. When I built the house in '86 I did all the wiring (5 miles of romex in the house). We have over a 500' run from the street and I wanted the power company run larger wire. The only way they would do it was if I put in a 400 amp service. Dopey me said OK I would. I have 2 breaker boxes to the left of the CT cabinet and a 200 amp breaker that feeds 3 boxes on the other end of the house. My labor was cheap and copper wasn't $4.00/lb.

Plus the 400 amp transfer switch cost me less than buying a 200 at our old house.

 

[Timeline98]

Wiring

How do you plan on wiring that transfer switch? Are you just going break the Neutral? You will need to pay particular attention to the Neutral to Ground bond within the Generator. I will try to post something tomorrow on generator wiring.

- Keith

 

[PeterD]

One route to go that has not been discussed is:

Generator Manual Transfer Switch - 100 Amp

which is basically a CH transfer switch. Well built, but a bit large, it is clearly a professional solution to the 'problem' of doing it right.

 

[sewerzuk]

Another option is a main power transfer panel; I installed these on both my house and shop services when I built them:
Generator Manual Transfer Switch - 100 Amp
(The ones I used were 200A versions of this panel). This is both more expensive and more involved...however, you can transfer over your entire service this way and are only limited by the size cable and power inlet box you use when you install it.

One route to go that has not been discussed is:

Generator Manual Transfer Switch - 100 Amp

 

[Stalwart]

If you are doing a whole house transfer, the size of the generator has no bearing on the size of the transfer switch. The transfer switch rating is sized to the service to the house. It has to transfer ALL the power going to the house when the mains are connected. For instance I have a CL320 meter base which has a CONTINUOUS rating of 320A. Hence I chose a 400A manual transfer switch.

 

[ctfjr]

If you are doing a whole house transfer, the size of the generator has no bearing on the size of the transfer switch. The transfer switch rating is sized to the service to the house. It has to transfer ALL the power going to the house when the mains are connected. For instance I have a CL320 meter base which has a CONTINUOUS rating of 320A. Hence I chose a 400A manual transfer switch.

You are 100% correct Stalwart! In my case I had to locate a 400 amp switch. Most homes have 200 amp service so a 200 amp xfer switch would do the trick. btw I did a quick search on ebay and found several manual 200 amp switches between $300-$500.

If you are concerned about putting a generator that is not nearly capable of handling your whole house then I see 2 options. First you could switch the entire house and then selectively turn off non-essential circuit breakers. The alternative would be to use a generator sub-panel & move selected circuits off the main box into the sub. These sub-panels are commonly 100 amp and include a built in xfer switch.

 

[PeterD]

 

[PeterD]

You are 100% correct Stalwart! In my case I had to locate a 400 amp switch. Most homes have 200 amp service so a 200 amp xfer switch would do the trick. ...

One thing to be very careful of is that to meet code (NEC) when you have an automatic swtich, and an automatic starting generator, the generator must be also rated at that load too. But... I'm not sure what NEC says when the generator has automatic over current protection (such as found on most MEP generators) and whether that might meet the code.

One way to avoid installing a huge transfer swtich is to use two boxes, one for the main power in, with a smaller breaker to feed the transfer switch. Then a second box off the transfer switch that supplies only those circuits that you need backed up with the generator. For example, I don't care if the washer, drier or a few other things get backed up or not, as long as the main things (heat, lights, outlets, etc.) are. That will let you perhaps use a 100 amp transfer switch by keeping that second box rated at 100 amps too... You'd have to feed the transfer switch using a 100 amp breaker as well, no big deal there.

 

[mistaken1]

As I understand it if you are doing automatic transfer and automatic generator start then the generator has to be sized for the full load or if not sized for the the full load you must to have automatic load shedding.

If the transfer is manual then you can undersize your generator and do manual load shedding.

The most important safety point is to have an arrangement that will not let the generator backfeed the utility (which is what one will get when following the NEC).

I like the idea of having the whole house connected with manual load shedding. That way in an extended outage I can shut down the HVAC and do laundry or pump water then when finished bring the HVAC back online.

http://www.steelsoldiers.com/auxillary-equipment/38439-connecting-mep-house-2.html#post925603

http://www.steelsoldiers.com/auxillary-equipment/38439-connecting-mep-house-2.html#post929559

 

[islandguydon]

IMHO, SAFETY FIRST...!

A transfer switch is defenitly the way to go. An auto TS would be nice but manual works just as good and is safe for you and your home. Please ground the box. Ground, Ground, Ground.

 

[M1031CMT]

When we got the new house built, we paid the extra money and got the electrician to wire in the generator panel. Cost $1,200 (included the panel, wiring and labor) but in the end we were very happy with what we got. It is up to code (good for insurance reasons) and it well setup. It is a manual switch. But since we don't have a type of generator that starts up automatically (or is always connected), an automatic switch was not the way to do it. But he told us if we ever want to install an auto-start generator, the switch can be changed easily.

Only thing we would have liked would have been a connection on the outside of the house, but they said it was better for security reasons. We just have to run the cord under the garage door and out to the generator we have in the M1031. Only problem we have to fix is that the cable they gave us was not very long. It was made just long enough to connect to a generator sitting right outside the door. But since our generator is in the truck, we need a cable about 4 feet longer. Nothing major.

 

[hardhead]

Please make sure you have a visible "open" most transfer switches have one, I am not sure a breaker will give you that. BTW, I am just a power lineman with his $.02