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Old 10-10-2013, 09:34 AM   #15
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Finally got the relay replaced and did a couple of other mods. I got the switch for the front AC done so that I can run it on shore power and it works perfectly except the unit isn't cooling. I also ran a separate circuit for the dometic fridge since it was blowing the GFI breaker after a few minutes. The element is getting hot(not sure how hot) but the fridge isn't cooling(ill make a new thread for those issues later). here's the relays (old vs new)


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Old 10-10-2013, 02:19 PM   #16
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Those flex braid things don't just burn up like that for no reason or out of regular wear and tear. That thing lived through a dead short, a lightning hit, or a 10x overload.

Bonding, grounding, and neutral switching with transfer switches is a difficult topic. Approaches have changed over the years and manufacturers recommendations aren't consistent; also, the approach in RVs is generally not the same as the approach in buildings. Caveat lector.

If you are using an SPDT switch to choose power sources that means you aren't switching the neutral. Three problems with that, one, the neutral blade on your separate 20a plug for the air conditioner may carry a few volts to ground, enough for a bad shock, as a result of voltage drop in the neutral on the 30a shore power cord and associated wiring. Second problem if you connect it to a miswired outlet with reverse polarity it will blow up in your hand. Third problem is that you're running the 30a and 20a neutrals in parallel essentially and so if there is an open or a high resistance on the 30a shore power cord you'll have up to 50a going through the neutral on the 20a cord. No breaker or fuse because its the neutral so your first indication that something is wrong may be the sirens from the local FD.

This sort of thing is why the NEC doesn't allow multiple service entrances (except in rare cases in exceptionally large facilities).

My rig is wired for 50a which is the right way to do this.
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Old 10-10-2013, 04:03 PM   #17
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not sure what blew the braid but it was the neutral side of the ckt not the hot the braid looked kinda wimpy especially compared to the new relay but the old relay was marked to be 30a and the new ones 40a but that's a big difference for 10 more amps...either way all is working normal now.
on the ac mod, the input power is not going th be tied into the 30a service cord but it will have a separate drop cord hooking into the 20a park/home outlet. I've read on several forums that this is a more cost effective way to run the front ac without the gen running or having to run a new service entrance cord and panel box. The neutral will be tied into the neutral the gen feeds the circuit and the ground will be tied to the chassis like it should be, yes im only switching the hot side but in my limited knowledge of electrical it seems to make sense. I did make a diagram to demonstrate this mod if you can understand my cryptic drawing style...lol
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Old 10-10-2013, 09:27 PM   #18
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but hopefully I get points for making it look good...lol

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Old 10-11-2013, 05:41 AM   #19
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Why not just install a 50 amp transfer switch. It will do all of this for you plus have extra capacity.
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Old 10-11-2013, 06:39 AM   #20
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if I understand it correctly, in order to take advantage of 50a service you need a 4 wire shore cable (2 120 hots 1 neutral and 1 ground) the 30a cord only has 3 wires (1 hot 1 neutral and 1 ground) the front ac circuit is independent anyway since it is originally wired only to the gen (gen has 2 120 outputs 1 30a to the coach and 1 20a to the front ac) I just took advantage of the separation and added a second input to the front ac circuit. I know ill have to make sure that both plugs are wired correctly but its a good habit to check regardless from what ive read.
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Old 10-11-2013, 10:51 AM   #21
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Another way that mod is sometimes done is, instead of a switch, just put in a receptacle for the 20a side of the generator. Then plug into that for generator or connect an extension cord if using shore power. Breaks both hot and neutral and the switch is never in the wrong position.
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Old 10-11-2013, 08:32 PM   #22
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I agree with Jammer in post 16. Instead of using the SPDT switch, I would have went with a DPDT (double pole double throw). This way you would be separating the neutral as well. It's easy to change. Just add another white wire & do what you did with the hot black wire.
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Old 10-11-2013, 10:45 PM   #23
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I see what you are saying and its a good idea but Lowes didn't have any dpdt switches that I could find...might try one from the internet I guess.
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Old 10-16-2013, 07:44 PM   #24
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Quote:
Originally Posted by romakdaddy View Post
I see what you are saying and its a good idea but Lowes didn't have any dpdt switches that I could find...might try one from the internet I guess.
A proper DPDT switch with the right rating costs about $60. I did the same mod as 3 Dog Nite and it works like a charm. Highly recommended.

Here is the DPDT switch switch I used.

Brad
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Old 10-22-2013, 02:46 PM   #25
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got the right switch and I must say...it wasn't cheap.got one local for 70 bux and installed it the next day...I shouldn't have to worry now cept getting the front unit to cool...lol
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Old 10-22-2013, 07:32 PM   #26
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Maybe I am missing something or have a different set up (350). I have a SPDT switch that lets me choose whether to run the front or rear A/C when on shore power (both are fed on Generator). Is this the same on the 370?

Because, even if you used a DPDT switch on the Generator feed to the front A/C it is still not isolated since it shares a neutral on the SPDT switch to choose which A/C to run.... So wouldn't you also need to replace the A/C selector switch with a DPDT switch as well?

I could be wrong, and often am, but I was hoping to do the same mod and was looking at the wiring diagram in my manual.
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Old 10-22-2013, 07:48 PM   #27
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Dave,

Refer back to posts #17 and #18. The purpose for installing the switch is to allow running both air conditioners while connected to shore power. Typically these motorhomes are set up to allow only one of the two to run at a time on a 30 amp circuit.

What the switch does is allow you to bring in a separate 20 amp shore power cord , connect it to one side of the switch, the generator feed to the other side and the output goes to the rear a/c unit transfer switch.

With the switch in one position the a/c unit is powered from the generator (or factory shore power). In the other position it's powered from the new 20 amp shore power cord. This allows you run the front a/c unit via the rotary switch that selects which a/c unit, front or rear.

I have a sketch of how I did the wiring change on the 310. If I can dig it up I'll send you a copy.

All in all it's a nice wiring change to make.

Brad
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Old 10-22-2013, 08:30 PM   #28
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Brad,

I still don't see it. I understand the purpose, but fail to see how the Rear A/C gets a neutral if not tied together somewhere. Since the switch is a SPDT switch the hot is being shifted. But where are the A/C's getting neutral if not tied in. There are 2 Generator neutral ties ins on the main breaker panel and a magnetic transfer switch to switch the hots. I need to look at the switch over relays for the main and rear A/C again.... I am also going to go into the electrician at work ans say "splain this to me".
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