50 Amp switch electrical advice needed - Montana Owners Club

bncinwv · 05-20-2011, 04:24 AM

Need some advice and information from the electrical gurus on the forum again. At some point (yeah right!!) I am going to finish the installation of the Autoformer in the rig. The way I installed it in the previous rig was to have it isolated by 50 amp plugs so that I could take it out of the loop to eliminate the 2V bump that at times caused the EMS to disengage power to the rig. With the current installation location planned for under the steps to the living room, I really don't want to have to plug and unplug the unit. Is there any kind of a bypass switching mechanism that is available?? What would be ideal is to have a bypass switch for the Autoformer mounted in the entry closet where it could easily be accessed. My plans are to leave the Autoformer isolated, then in low voltage situations where the EMS kicks in, be able to switch the Autoformer on. Any ideas, comments, criticisms???
Bingo

NCFischers · 05-20-2011, 05:12 AM

Bingo,
You would need a two pole 50 amp rated A/B type switch wired so you could bypass the autoformer if needed and run power directly to your EMS.

bncinwv · 05-20-2011, 05:34 AM

Thanks Jim,
I might have to call or PM you, but I am trying to post on the forum so hopefully others can learn while I do. I think you know the circuit as I have it, but as a service to the forum: I have two inputs to the rig, shore power and generator that are going to an automatic transfer switch. Output on the automatic transfer switch from both sources then goes through the EMS to the rig. Autoformer is only on the shore feed side as they are not recommended on generator circuits. This is the feed that I want to able to go in two branches. So if I mount a single breaker box in the closet with an A/B switch, one setting will allow the current to go through the Autoformer and the other will allow it to bypass it? Is this all something that is readily available at Lowes or Home Depot?? And is a switch available that will handle 6 gauge wire, I think that is what the feed lines are if I remember correctly?? Guess what I really need to find is some on-line diagrams or schematics of the switch so I can fully understand the hookups, can you guide me in that direction??
Bingo

farmboy · 05-20-2011, 06:29 AM

I think another transfere switch should do the job just fine. Control of transfere sw. would be with low voltage via a wall sw. JMO, but then I am an industrial electrician. With that much power I prefer relay/contactors.

bncinwv · 05-20-2011, 06:37 AM

What has me confused is how can I possibly wire this without using two switches?? If I have two possible input branches (to Autoformer or to EMS) and two possible output branches (from autoformer and straight through to EMS), how can I do this with one switch? As it is now (manual plugging), I have to unplug the autoformer (one switch??) and plug that plug into the EMS feed line (second switch??).
Bingo

Phil P · 05-20-2011, 02:04 PM

Hello Bingo

I work a lot with 200 Volt 3 Phase 400 cycle power. We do all of our switching the way Farmboy advises. In my opinion that the low voltage control makes for a cleaner application of the switch with less electrical arcing.

Maybe Farmboy can scan a simple drawing of the circuit for us and supply some part numbers.

Phil P

gregdan24 · 05-21-2011, 03:07 PM

Here's how I installed a second power inlet with a manual interlock transfer switch. A 5 or 6 circuit box and two breakers from Home Depot was like 30 bucks. They sell the interlock shown too, but I made up my own. You may be able to use something like this for your situation.

http://s1231.photobucket.com/albums/ee506/danneffgr/

farmboy · 06-06-2011, 01:46 PM

Well Bingo, I finally got home so I could get good internet service so here is my idea to help you out. You need the following items: 1 on-off-on sw.(toggle or wall). 3 ea.- 50amp 2pole contactors with 120volt coils. I suggest you mount the sw. where you wish. One contactor between shore power and transfer sw. The other two contactors are for the autoformer. One on the input side and the other on the output side. The idea is for one position(A) of sw to control the first contactor and the other position(B) to control the other two at the autoformer. Position A will isolate the autoformer when not needed and positon B will let the autoformer do its thing and isolate the transfere sw. I have no way of putting up a diagram so I hope you get the idea. I also have no experince with an EMS so I don't know if you should wire the output of the autoformer to it's input or bypass it. You may know best. I hope this helps you out. Pm me with question if you have any. JOHN

NCFischers · 06-06-2011, 03:43 PM

Bingo,
John has the right idea. you can control the electrical path easily with a lot less heavy wire.
Jim

bncinwv · 06-06-2011, 04:39 PM

I will have to get back to this. Been working on the dock most of the Spring. John, I am curious as to how much all of that will cost. I usually do things the cheap way (like plugging and unplugging the autformer). John, I will PM you and Jim, I still plan on giving you a call as well, when I get back to doing Montana things. As I said, this weather has me working on the dock evenings and weekends trying to get it ready for the fourth of July. One thing I have always done, is take advice from any who will offer it in order to make a more informed decision. Thanks to all for the responses. What would help is if I could get some web pages that show all the respective devises that are believed to be needed. That way I can actually understand the wiring required. Still confused on the output side of the circuit since both routes have to go to the same input of the automatic transfer switch. The other input of the automatic transfer switch is dedicated to the generator circuit. The current shore power input at the automatic transfer switch is the one where I need the new double inputs (one Autoformer and one shore power). Still seems like I would need two switches, one to route the input power to the Autoformer or shore power only and another one to switch the input to the transfer switch from the output of the Autoformer or the shore power input line?? Maybe I am over-complicating this, but I want to make sure what I buy will work up front.
Bingo

noneck · 06-07-2011, 03:00 PM

Well, I'd need a schematic to make this discussion more clear. It would be important to note that the switch should "default" to Autoformer state as expecting a electrical control device to activate on fuzzy power is not good circuit design.

bncinwv · 06-07-2011, 03:37 PM

Actually, I was hoping to have it the other way, that is the default would be sans Autoformer. With the EMS, if the EMS shuts power to the rig and the code yields a low voltage situation, then I am hoping to energize the Autoformer and hopefully be able to use the rig and prevent the EMS from engaging. If I didn't have the EMS, then I would agree with you Charles. Of course at the rate I am going, by the time I get the installation complete, it will be time to trade the rig again!! I think I started the installation in November, and still haven't completed the cutting under the steps I need for the internal Autoformer installation. Might have to put it all off until the rally in NC, then everyone can supervise me!!

Bingo

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