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Inverter / House Relay Issue
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Posted 2020-05-19 10:35 PM (#7315)
Subject: Inverter / House Relay Issue


So here is my situation.

The old inverter was fried when I got the coach. In removing it last week I found that something went really bad in that general area. The ground pin of the power cord was melted into the inverter, and the cord itself basically had melted down. Again, this is how I got the coach so no clue what happened.

So I was able to pick up a very nice 3000 watt Pure Sine inverter and spent the past week installing it in my free time. So tonight, I strike it up and this happens... The relay has a light that comes on, but the Allan Bradley Latch Relay is freaking out, slamming on and off.

Things that I know.... kinda... The inverter works, and seems unfazed by the event. I ran new 10guage wires from the inverter to the Latch Relay, placing them were the other wires had been. If I bypass the Latch Relay the system works fine (plugging the inverter into the Street Power plug).

I guess this old server won't take a video file so here is a link to the freakout

Edited by woodlandfarms 2020-05-19 10:44 PM
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Posted 2020-05-20 7:30 AM (#7316 - in reply to #7315)
Subject: RE: Inverter / House Relay Issue

Extreme Veteran

Location: Victoria, BC. Canada
Out of my league, Carl.

But I'm going to follow this because I've also got a 3000 watt inverter install on my event-horizon.

Someone will chime in here...

Good luck!

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B. Sitton
Posted 2020-05-20 9:24 AM (#7317 - in reply to #7315)
Subject: Re: Inverter / House Relay Issue

Extreme Veteran

Location: Ignacio Colorado
Carl you lost me on this one. The transfer relay is to switch between generator and shore power cord. You have introduced a third source of 120v power. The source for the inverter is 12v. Where did you connect the inverter 120v output? Do you still have a generator?
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Posted 2020-05-20 12:34 PM (#7318 - in reply to #7315)
Subject: Re: Inverter / House Relay Issue


Here is some pix of the guts of the system. What is interesting is that there is no Relay, only a Blade, for the Generator from what I can see.

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Posted 2020-05-20 1:33 PM (#7319 - in reply to #7315)
Subject: Re: Inverter / House Relay Issue


OK. I think I may be onto something. Take a look at this picture.. On the Nuetral (white) wire heading into the Allen Bradley switch, there is a jumper that goes to the next switch which handles the generator. But this jumper is connected to the HOT wire coming from the Generator. Shouldn't it match, going to the Nuetral of the Generator? And secondly WHY? WHY are these even tied together. I get them being tied on the opposite side of the switch, but not on the input side.
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Posted 2020-05-20 1:46 PM (#7320 - in reply to #7317)
Subject: Re: Inverter / House Relay Issue

Extreme Veteran

Location: Scottsdale, Aridzona
Duh ? Was the PO (previous Owner) named Nikola Tesla, or Thomas Edison ?
Some, many, most, all, FMCs have been modified by POs a little, a lot, completely, and no particular wiring or "other system" diagrams were made, or transferred with each unique FMC up to the present . . . and probably the future.
Many FMCers think THEIR FMC is just the way it came from the San Jose Factory. Most likely NOT ! Yours ? DEFINITELY NOT !

Converter - (120/240V) AC to (12V) DC. C= AC>DC
Inverter - (6/12/24/36V) DC to (120/other?) AC. I= DC>AC
Above for RVs.
There are many other rectifiers, converters, inverters, diverters, multipliers, dividers, subtractors, contactors, contractors . . . see your Financial Advisor before making a choice.

Stock FMC does not have an Inverter except for 110V on Refrigerator. Original FMCs did not have 3 way Reefers. They may not have been "invented" for RVs yet.
Propane was the "new and improved" version of RV reefers, which was the 3rd way, ie: 12V, 110V, LPG.
All 3 way Reefers in FMCs are "add-on updates", which is why all the different size/location vent doors.
Our Norway Friend Kjetil's #477 is the only FMC that I know of that has a 3-way Reefer without the outside Vent/Door. He explains why and how in his excellent Album Series in this website.

Please review The Coach Electrical System, 12V and 110V, in Section 5 of the Owners Manual. That describes WHAT YOUR FMC WAS. You get to finger out WHAT YOUR FMC IS.
You may become very familiar with and the DIFFERENCES between Figures 5-28, 5-29, 5-31, 5-33, and 5-34 . . . and YOUR FMC.
Stock . . . the FMC only had 110V when plugged into "Shore Power" or the APU (Auxilary Power Unit, big green thing in left side of Engine Bay, also called Generator) was running.
Stock . . . everything else was 12V ONLY from the batteries . . . or the converter (still 12V out) when Shore Power was plugged in, or the APU was running.
Stock . . . when APU running or Shore Power plugged in . . . the Coach ALSO had 110V to the various outlets, AND 110V to the CONVERTER.
The 110VAC to 12VDC CONVERTER "is/was" located under the Passenger seat.
Does #86 have a CONVERTER under the Passenger seat ? If not . . . where is it ?
Other more detailed "explanation" is available in the FMC Parts Manual and the FMC Service Manual.

You may want to make copies of the various wiring diagrams . . . and mark them up with colored pencils, crayons, "magic" markers, etc of just exactly what YOUR FMC ELECTRICAL SYSTEM IS.
If you ever sell YOUR FMC it would be appreciated if you transferred those marked up Electrical System Diagrams to the new owner.

Like life itself . . . things FMC are never what they seem !
Spark (ZAP!) ON !
Lou #120

Edited by hemi354az 2020-05-20 2:07 PM
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Posted 2020-05-20 8:28 PM (#7321 - in reply to #7315)
Subject: Re: Inverter / House Relay Issue


So as my new inverter has a built in relay, I am going to bypass entirely the functioning relay in my motorhome. It then came to me that the previous relay was deliberately set up to accommodate providing to both legs of the 110 circuits. Guess I either buy something updated or I get this relay working. My friend who works on giga yachts uses these types of systems and gave me his checklist. Will give it a try tomorrow.
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