Easy solution don't blue into a gfi outlet. Lots of neutral to ground connections in the GMC as they should be.
Neutral and ground are bonded in the breaker box.

You could get rid of the transfer switch entirely??

Most gmc's do not have a transfer switch, the onan wires up to a female outlet, and you either plug coach into that outlet for generator use,

Or it plugs directly into shore power. Where the onan is now completly separate from coach wiring.

Transfer switch could be nice, but I personally dont think it is all that nessiary.

Aaron,

I'm with Rick; your solution needn't be too complicated; the Coachmen
should have had separated Neutral and Ground busses.

As for the switching, I'm not sure ordinary 50A Automatic Transfer Switches
will recognize the 30A plugs you intend to use. Further, there complexity
and cost are not justified. Here's DIY version of a 30A transfer I've
used, without attention, for the past 19 years:

http://www.gmcmhphotos.com/photos/g3484-automatic-120-vac-power-source-selection.html

It's simply wired; in fact, mine's in excess space inside my replaced
circuit breaker panel (that's probably not Kosher, 'tho').

Aaron,

Welcome to the group, family, cult, asylum....

We may well have met at Shawnee, but you are here now and that is what matters.
You have a first class team helping you with your electric issues. There is not simple way you could do better than where you are right now.
Please do not feel like you are imposing on the people here. This what most of these people enjoy - Helping other owners.
The geography does make it hard some times, but we try to over come that.

If you have not already, you will soon find that your coach is much more than a new and different toy. Being an owner makes you a part of a community that is like few others. I say that and I only know of one. These people will pull off some amazing things to help another owner. It is all because they want other and particularly new owner to get as much enjoyment from what a GMC can do for you as we have all gotten to appreciate. That other community is that of the watermen of my world. That be the case, I like to welcome new owners here much as any new owner or vessel is welcomed there. So,

May the Good Lord bless this coach and all those that set forth within her.

Welcome Aaron

Matt

I have a GMC upfit coach so can't go out and look at Coachmen wiring--- but from what I remember the breakers for flip/flop between shore/Onan are 2 pole each, as Coachmen uses TT-30 hookup (single hot, neutral, ground) and one pole is on the hot and one on the neutral on each breaker. Disconnected from power and using an Ohm meter you should by concentrating on this area you should be able to find where and why the N and G are tied. Perhaps a bad breaker in the flip/flop (easy to test) or the handy work of a PO who "fixed" it.

Aaron,

You overestimate the cost and complexity of a DIY auto transfer switch.
Here's a first-look relay for $18.49:
http://www.mouser.com/ProductDetail/TE-Connectivity-PB/T92S7D22-110/?qs=sGAEpiMZZMtSzCF3XBhmW6vMa%2fMpJxoP71VMV4XEUfE%3d

Only one relay is needed if you only want to transfer between shore and
generator -- just delete all the connections and components in the Inverter
section.

But if you're not comfortable with that level of electrical fabrication,
stick with the factory-built solution. But remember that with your
isolated ground system, you shouldn't need a 50A switch. I believe you'll
find that all commercial transfer switches operate just about like my
diagram, meaning that the shore power will never see the Onan's combined
Neutral and Ground connection.

HTH,

Ken H


On Fri, Sep 1, 2017 at 9:29 PM, Aaron Bush wrote:

> Ken Henderson wrote on Fri, 01 September 2017 15:36
>> Aaron,
>>
>> I'm with Rick; your solution needn't be too complicated; the Coachmen
>> should have had separated Neutral and Ground busses.
>
>
> That's correct - my busses are separate at all boxes on my coach - the
> ground and neutral are only connected at the generator and that neutral is
> not
> switched anywhere, nor is the ground from the generator. The comment about
> the neutral and ground busses being connected was not mine, and it's not
> actually the problem that I have. I guess the *simplest* thing for me to
> do would be to put in a double pole breaker at the main generator box - but
> that still leaves a convoluted set-up with more boxes, more wire, and
> certainly more junction boxes and wire nuts, than I actually need. Also, if
> I
> get rid of the excess boxes and wire I will gain some usable storage
> space. Also doesn't resolve power for my 2nd AC on shore power. So toss that
> idea.
>
>
> Quote:
>> As for the switching, I'm not sure ordinary 50A Automatic Transfer
> Switches
>> will recognize the 30A plugs you intend to use. Further, there
> complexity
>> and cost are not justified. Here's DIY version of a 30A transfer I've
>> used, without attention, for the past 19 years:
>>
>> http://www.gmcmhphotos.com/photos/g3484-automatic-120-
> vac-power-source-selection.html
>>
>> It's simply wired; in fact, mine's in excess space inside my replaced
>> circuit breaker panel (that's probably not Kosher, 'tho').
>
>
> Mmmmm, this seems a bit complicated to me. It's certainly a little more
> than I'm easily comfortable with in terms of electrical diagrams - but it
> looks like I would need two of the power relays ($50 each), two diodes(14
> cents each), and two capacitors (don't know the price.) That puts me at
> around before the capacitors $100, about $50 less than the switch I am
> looking at. Basically you built your own automatic transfer switch correct?
> It
> might be worth $50 of my money right now to pay some one else to build it
> for me. I would probably enjoy doing that if I had a little more time for
> it.
>
> I'll double check on whether the PD52 transfer switch will work with 30
> amps - I believe it will, but the connection instructions for that switch
> are
> not entirely clear.
>
>

Aaron,

If the link led to a DPST relay, I apologize for not searching more
carefully; you must use a DPDT relay, which will, indeed, be a little more
expensive. They're frequently available on eBay for pretty good prices; I
can't give you a number off-hand, but it will probably be from
Potter-Brumfield. Be sure the coil is 120 VDC NOT vac or you can't use
the capacitor to slow operation, which is definitely desirable. It would
be simple to use a lower voltage DC coil, but would complicate the circuit
by requiring a step-down transformer.

Since your house circuits are only set up for 30A load, the Onan will only
supply that current to them through the NO contacts of the relay. Whatever
method you use to supply the 2nd A/C from shore power you'll need to
utilize for the Onan also. It would, of course, be quite simple to add
another relay (requiring only 15A contacts) in parallel with the transfer
relay to handle the Onan, but it will be simpler and easier to just provide
a socket from the Onan, BEFORE the auto transfer relay, to plug the 2nd A/C
into. Another option to paralleling the primary relay would be to include
a second relay after the primary one.

Sorry if I offer too many or too complex options -- my extensive parts
inventory and 60+ years of electronics education and tinkering dominate my
thinking.

Ken H.


On Sat, Sep 2, 2017 at 10:09 AM, Aaron Bush wrote:

> Well, this is very interesting - I understand about not including the
> inverter. I thought I would need a 50 amp switch because the onan power
> would be
> running through it - but you are saying that is not the case, that I only
> need a 30 amp switch which would be activated by my 30 AMP shore power, not
> the onan? (Onan would be the default power so only the contacts would be
> experience more than 30 amps.)
>
> Also, hashing this over with a friend who is more familiar with
> electronics than I am, then reviewing some switch terminology - I'm pretty
> sure I need
> a DPDT relay, but the one you linked to below is DPST.
>
> Are you thinking of a way to do this with a ST switch? Either way, if I
> can do it with one really, one diode and one capacitor, then I think I can
> handle that.
>
> Please realize this post makes me sound a little more electronics savy
> than I really am.
>
> Aaron
>
>
>
>
>
>
>
> Ken Henderson wrote on Fri, 01 September 2017 21:38
>> Aaron,
>>
>> You overestimate the cost and complexity of a DIY auto transfer switch.
>> Here's a first-look relay for $18.49:
>> http://www.mouser.com/ProductDetail/TE-Connectivity-PB/T92S7D22-110/?qs=
> sGAEpiMZZMtSzCF3XBhmW6vMa%2fMpJxoP71VMV4XEUfE%3d
>>
>> Only one relay is needed if you only want to transfer between shore and
>> generator -- just delete all the connections and components in the
> Inverter
>> section.
>>
>> But if you're not comfortable with that level of electrical fabrication,
>> stick with the factory-built solution. But remember that with your
>> isolated ground system, you shouldn't need a 50A switch. I believe
> you'll
>> find that all commercial transfer switches operate just about like my
>> diagram, meaning that the shore power will never see the Onan's combined
>> Neutral and Ground connection.
>>
>> HTH,
>>
>> Ken H
>>
>>
>> On Fri, Sep 1, 2017 at 9:29 PM, Aaron Bush wrote:
>>
>>> Ken Henderson wrote on Fri, 01 September 2017 15:36
>>>> Aaron,
>>>>
>>>> I'm with Rick; your solution needn't be too complicated; the Coachmen
>>>> should have had separated Neutral and Ground busses.
>>>
>>>
>>> That's correct - my busses are separate at all boxes on my coach - the
>>> ground and neutral are only connected at the generator and that
> neutral is
>>> not
>>> switched anywhere, nor is the ground from the generator. The comment
> about
>>> the neutral and ground busses being connected was not mine, and it's
> not
>>> actually the problem that I have. I guess the *simplest* thing for me
> to
>>> do would be to put in a double pole breaker at the main generator box
> - but
>>> that still leaves a convoluted set-up with more boxes, more wire, and
>>> certainly more junction boxes and wire nuts, than I actually need.
> Also, if
>>> I
>>> get rid of the excess boxes and wire I will gain some usable storage
>>> space. Also doesn't resolve power for my 2nd AC on shore power. So
> toss that
>>> idea.
>>>
>>>
>>> Quote:
>>>> As for the switching, I'm not sure ordinary 50A Automatic Transfer
>>> Switches
>>>> will recognize the 30A plugs you intend to use. Further, there
>>> complexity
>>>> and cost are not justified. Here's DIY version of a 30A transfer
> I've
>>>> used, without attention, for the past 19 years:
>>>>
>>>> http://www.gmcmhphotos.com/photos/g3484-automatic-120-
>>> vac-power-source-selection.html
>>>>
>>>> It's simply wired; in fact, mine's in excess space inside my replaced
>>>> circuit breaker panel (that's probably not Kosher, 'tho').
>>>
>>>
>>> Mmmmm, this seems a bit complicated to me. It's certainly a little
> more
>>> than I'm easily comfortable with in terms of electrical diagrams -
> but it
>>> looks like I would need two of the power relays ($50 each), two
> diodes(14
>>> cents each), and two capacitors (don't know the price.) That puts me
> at
>>> around before the capacitors $100, about $50 less than the switch I am
>>> looking at. Basically you built your own automatic transfer switch
> correct?
>>> It
>>> might be worth $50 of my money right now to pay some one else to
> build it
>>> for me. I would probably enjoy doing that if I had a little more
> time for
>>> it.
>>>
>>> I'll double check on whether the PD52 transfer switch will work with
> 30
>>> amps - I believe it will, but the connection instructions for that
> switch
>>> are
>>> not entirely clear.
>>>
>>>
> Your proposed 2nd A/C solution is certainly workable, but in the
>> past when
>> working on 30A service coaches, I've just added a separate 15A CB box
> and
>> line cord for the 2nd A/C.