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BMC (Bluebird Motor Coach Unique Issues) If you have a unique issue with your BMC coach and it can't be answered in one of the other forums here, then this is where you can list it.....List your BMC Parts here too.

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  #11  
Old 04-11-2013
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To try and make clearer what I am talking about I have made a diagram (somewhat crude) that shows how coaches are most likely wired when they have the relays for transferring inverter power to select circuits. (at least this is the case with mine)
The AC out wiring from the inverter should only carry the output from the inverter when it is turned on, not any "pass through" loads. If AC power is allowed to pass through on this wiring it will result in AC power coming from 2 sources into the relays at the same time. I don't know if that in itself is a problem but I would imagine that the relays prioritize the power coming from the main panel, but when the breakers in the main panel are turned off the circuit will remain hot because of the pass through. That would be the test for this situation. While plugged into shoreline, turn off the breaker to one of the circuits that you know are powered on inverter, then check to see that the circuit is actually dead. I welcome any other information anyone could shed on this as well.
I also included a pic of one of the boxes with three of the relays from an earlier post from Robert Britton.
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Last edited by Buckeye Bird; 04-11-2013 at 08:38 PM.
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  #12  
Old 04-12-2013
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So based on my observations and your drawing those six relays are energized on shore power and generator power then they are de-energized on inverter power. So if you do not have power to a single specific circuit on shore or genny power but do on inverter power these could be the problem. Right?
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  #13  
Old 04-12-2013
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Quote:
Originally Posted by Buckeye Bird View Post
To try and make clearer what I am talking about I have made a diagram (somewhat crude) that shows how coaches are most likely wired when they have the relays for transferring inverter power to select circuits. (at least this is the case with mine)

I also included a pic of one of the boxes with three of the relays from an earlier post from Robert Britton.
I've located a few schematics that I hoped would shed some light on how the engineers meant for the inverter and shore power to be wired in the 1980s and 1990s. They don't accomplish much to move your question forward, but I think they illustrate the existing hardware that is involved in your trouble condition on the Insta Hot wiring. In schematic #1, (early 1980s), the inverter was a Redi-line auxillary generator that was manually switched on when 12V-->120V was wanted. In schematic #2 (early 90s), the idea was still to turn the inverter on when 12V-->120V was wanted. The 8-terminal relays in both schematics suggest that not much changed in all that time. Both appear to have a relay that transfers the load between two power sources. Maybe someone who actually knows how to read them will come along to educate me.

What happens when both sources of 120V are hot? I don't know, but my '91 still runs the old PACS 1500 inverter while I decide how to install a new inverter/charger without remodeling more than is needed. (Your Line 2 Input "not transferred" option doesn't show up in any models I've shopped in the last year, by the way. Are inverters still available with that capability? ) So I'm switching the PACS on and off as needed. Somewhere in a manual I read a warning about serious consequences if I ever turn the inverter on while shore or generator power is present. I think the warning was about equipment damage, not about the hazardous live circuits that by-pass the breakers. I did create that condition once in my coach, and the main 50A automatic transfer switch "got confused" and quit switching. But it was fixable.

Obviously, as we know now, these inverter relays weren't designed for pass-thru 120V from the inverter and also 120V from the main panel, at the same time. But if you continue switching the inverter on/off as needed, it would be like having a very advanced inverter/charger back twenty years ago when the coaches were built.

Anyway, the attachments *might* illustrate the relays in Robert's photo and in your '94. Anyway, that's what I have in mind when posting them to this discussion. Hope they help.

--Ned
Attached Files
File Type: pdf Ice Maker Relay 82.PDF (17.7 KB, 213 views)
File Type: pdf 94_Inverter relays.pdf (636.4 KB, 217 views)
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  #14  
Old 04-12-2013
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Quote:
Originally Posted by bwinter1946 View Post
So based on my observations and your drawing those six relays are energized on shore power and generator power then they are de-energized on inverter power. So if you do not have power to a single specific circuit on shore or genny power but do on inverter power these could be the problem. Right?
I believe that to be the case, as far as when the coils are energized. So yes, if you have a situation as you described it could definitely be a bad relay.

Ned, thanks for posting the schematics. They help explain the relays as well. Like you, I don't know that having both sources hot causes any issue by itself, but it would leave the circuit hot even if the breaker tripped in the main panel as well as if it was turned off manually.
As far as inverters that can have the pass through feature turned off, the RV 2012 as well as the RV 3012 GS series modified sinewave inverters can.

If you are in the market you might try:
Mike LaVine
16026 E. Tillman Road
Ft. Wayne, IN 46816
(260) 433-3730 (cell)
mjlavine@aol.com

He often has Xantrex factory refurb units at a great price.
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  #15  
Old 04-12-2013
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I don't see any issue with two power sources on the relays, Only one at a time can be passed through.
I can't tell for sure from the diagram but I assume there are breakers on the output side of the relays to protect the individual circuits.
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Last edited by gcyeaw; 04-12-2013 at 02:17 PM. Reason: confusing
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  #16  
Old 04-12-2013
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No breakers on the output side of the relays, straight out to the individual circuits. When on shoreline everything goes through the main panel breakers before the relays. On inverter power it just uses the single breaker in the charger/inverter (25 amps on my RV3012) before the relays.
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  #17  
Old 04-12-2013
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Quote:
Originally Posted by Buckeye Bird View Post
No breakers on the output side of the relays, straight out to the individual circuits. When on shoreline everything goes through the main panel breakers before the relays. On inverter power it just uses the single breaker in the charger/inverter (25 amps on my RV3012) before the relays.
This is disturbing. If a device fails and trips a breaker, the relay will drop and connect the inverter to the bad device re-energizing the circuit. Assume the device is on a 15 amp breaker and the inverter is 25 amp This is not good as the circuit is designed for 15 amps and may heat up rather than trip the 25 amp breaker. I can't believe this passed any kind of RV electrical code.

So when a device shorts it is required to trip two breakers consecutively to open the circuit. And if an unsuspecting person trips the breaker and then tries to work on the circuit, he could get fried.

WOW!!!!!
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  #18  
Old 04-12-2013
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Quote:
Originally Posted by gcyeaw View Post
This is disturbing. If a device fails and trips a breaker, the relay will drop and connect the inverter to the bad device re-energizing the circuit. Assume the device is on a 15 amp breaker and the inverter is 25 amp This is not good as the circuit is designed for 15 amps and may heat up rather than trip the 25 amp breaker. I can't believe this passed any kind of RV electrical code.

So when a device shorts it is required to trip two breakers consecutively to open the circuit. And if an unsuspecting person trips the breaker and then tries to work on the circuit, he could get fried.

WOW!!!!!
Gardner, that situation would only exist if it is wired incorrectly, which was the original point of the thread. Many inverters have the AC pass through feature and would pass the AC power through what should only be the wire for inverted power. The AC pass through feature needs to be shut off. I wanted people to realize how easy it is to create that situation and not realize it.
I am pretty sure that I cannot have the inverter on when plugged in to a shoreline. I think it turns itself off when it senses incoming AC, however that does not keep it from powering up both sides of the relays with the AC pass through if that is activated.
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Last edited by Buckeye Bird; 04-12-2013 at 04:54 PM.
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  #19  
Old 04-12-2013
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Quote:
Originally Posted by gcyeaw View Post
This is disturbing. If a device fails and trips a breaker, the relay will drop and connect the inverter to the bad device re-energizing the circuit. Assume the device is on a 15 amp breaker and the inverter is 25 amp This is not good as the circuit is designed for 15 amps and may heat up rather than trip the 25 amp breaker. I can't believe this passed any kind of RV electrical code.

So when a device shorts it is required to trip two breakers consecutively to open the circuit. And if an unsuspecting person trips the breaker and then tries to work on the circuit, he could get fried.

WOW!!!!!
I do not believe that could happen in my coach. When I have generator or shore power the inverter is off and the battery charger mode is switched on in my inverter. I can only get the inverter to run when I have no A/C power in the coach. Safety interlock built into the inverter I suspect, so the Inverter/charger only does one function at a time. In addition, those six relays would remain energized until the A/C power is removed thereby, leaving the inverter out of the circuit.
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  #20  
Old 04-12-2013
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Quote:
Originally Posted by bwinter1946 View Post
I do not believe that could happen in my coach. When I have generator or shore power the inverter is off and the battery charger mode is switched on in my inverter. I can only get the inverter to run when I have no A/C power in the coach. Safety interlock built into the inverter I suspect, so the Inverter/charger only does one function at a time. In addition, those six relays would remain energized until the A/C power is removed thereby, leaving the inverter out of the circuit.

So you unknowingly trip a breaker, drop shore power while breaking camp and your inverter fires up..now you have that 15 amp circuit on the 25 amp inverter.....

Or maybe you trip a breaker intentionally because you discovered a broken outlet or other issue..same situation applies.
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