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  1. #1
    Rolling Along
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    Generator transfer switch concern...

    I just put in a Progressive transfer switch for my self installed generator. Operation seems pretty straight forward (one or the other but not both) but I have a concern. Since these are separate contactors, there is no mechanical lockout. If one contactor gets stuck (welded contacts) or a control board failure for that matter, both inputs can be energized.

    I'm curious how this is even legal.
    Roger, Stacy and the Sophie the fur kid

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  2. #2
    Seasoned Camper
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    There is no issue here, pretty standard electrical transfer switch. I actually have two of them on my RV that automatically switch between shore power/generator/inverter power. The contactor is either on one source or the other, if it gets stuck, it simply will not be able to energize from the other source. It cannot energize both sources at once, it is either one or the other. In any event, if you have the appropriate protection on the source power, any fault with a stuck contact will be cleared at the source.

    A simple description on how it all works..... The switch is spring loaded in a default position, which would be shore power in most instances. So if you plug in the RV to shore power, you get immediate power. If you are disconnected from shore power and start your generator, the transfer switch will sense it. After a time delay the transfer switch will energize a coil and the switch will transfer over to the generator, energizing the trailer. The switch cannot be in both positions at the same time, totally impossible.

    I have inadvertently left my inverter on, then unknowingly plugged into shore power. The trailer stayed on the inverter as the coil had the transfer switch locked in that position. It was only after the inverter started beeping on low power that I knew I screwed up. I turned off the inverter and the coil dropped out, switching back to shore power. Point is, even though it is an electrical transfer switch, there is a mechanical connection inside that can only be in one position. Perfectly safe.

    DAN
    Last edited by TwoElkhounds; 01-24-2020 at 10:46 PM.
    2016 Reflection 323BHS
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  3. #3
    Rolling Along
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    Thanks for the input, Dan. But I have to disagree.

    The Progressive Dynamics PD52 uses two contactors (heavy duty relays). When one is energized, shore power is connected. When the other is energized, generator power is connected. The "transfer switch" relies on a control circuit to ensure that they are not energized or closed at the same time. This is not a true switch that can mechanically be in only one position at a time.

    The system works well, as long all parts are working, but if something fails in the wrong mode it could be trouble.

  4. #4
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    Quote Originally Posted by TwoElkhounds View Post

    I have inadvertently left my inverter on, then unknowingly plugged into shore power. The trailer stayed on the inverter as the coil had the transfer switch locked in that position. It was only after the inverter started beeping on low power that I knew I screwed up. I turned off the inverter and the coil dropped out, switching back to shore power. Point is, even though it is an electrical transfer switch, there is a mechanical connection inside that can only be in one position. Perfectly safe.

    DAN
    Dan,
    Isn't the inverter AFTER the transfer switch? Thus power is supplied to it whether it is on shore power or generator? Most arrangements I've seen had a power protection device, then xfer switch, then breaker panel, then loads in that order when supplied from shore power; on generator it was the same except no power protection device, so: xfer switch, breaker panel, then loads (including inverter power/input).


    Quote Originally Posted by Roll With The Changes View Post
    Thanks for the input, Dan. But I have to disagree.
    Roll With The Changes, this might be a good question for Progressive; maybe drop them an email question. In the meantime, you got me wondering so I did a quick search and found this...; one of the posts included this: "...If you have a welded contact in one of the relays, it can cross-connect between the generator and shore power plug. When you run the generator you'll have voltage on the exposed pins of the shore power plug. And when you plug into shore power voltage is applied to the generator windings, shorting out the shore power and tripping the breaker....". So maybe you're onto something.
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  5. #5
    Rolling Along
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    @traveldawg... I'm waiting for Monday to call Progressive, but at this point I will leave it as is and here is why.

    My generator is not set up to be an onboard generator so I mounted it on the back for several other reasons. The original install was to just plug the generator into the shore power inlet when I wanted to use it... Simple. No mods required.

    Well, I got tired of going outside in the rain to start the generator for the first cup of coffee, so full install it is. Since I do most things differently than most, why not this too?

    I installed a second shore power inlet on the back of the coach to plug in the generator. That also gets me 20 feet closer to the pedestal that might be just out of reach

    So with my setup, I can just not plug in both at the same time. Other than sticking your finger in the shore power inlet, a failure of the transfer switch would not be catastrophic.

    Incidentally, when looking for a switch and learning how they work, I found that the Furrion F50 (model # ?) advertises a mechanical interlock for this very reason. I couldn't find any pictures and I didn't want to pay another $50 for an unknown.

  6. #6
    Rolling Along
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    And... I use an inverter generator and I do NOT want to find out what happens to it if shore power is applied to the output of the inverter

  7. #7
    Seasoned Camper
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    Quote Originally Posted by Roll With The Changes View Post
    Thanks for the input, Dan. But I have to disagree.

    The Progressive Dynamics PD52 uses two contactors (heavy duty relays). When one is energized, shore power is connected. When the other is energized, generator power is connected. The "transfer switch" relies on a control circuit to ensure that they are not energized or closed at the same time. This is not a true switch that can mechanically be in only one position at a time.

    The system works well, as long all parts are working, but if something fails in the wrong mode it could be trouble.
    Well, my switches are about 5 years old, so maybe they are different. Can't really go look at it as it is installed behind the wall in the basement and the fiver is buried in snow and covered. All I can say is that over the years, I have had any combination of inverter, shore power, and the generators inadvertently running at the same time on the fiver and have had no issues. The switches I have are pretty simple and cannot physically be in multiple positions simultaneously. If your concerned, maybe you might want to consider getting something more simple like what I have.

    DAN
    2016 Reflection 323BHS
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  8. #8
    Seasoned Camper
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    Quote Originally Posted by Roll With The Changes View Post
    @traveldawg.
    My generator is not set up to be an onboard generator so I mounted it on the back for several other reasons. The original install was to just plug the generator into the shore power inlet when I wanted to use it... Simple. No mods required.

    Well, I got tired of going outside in the rain to start the generator for the first cup of coffee, so full install it is. Since I do most things differently than most, why not this too?

    I installed a second shore power inlet on the back of the coach to plug in the generator. That also gets me 20 feet closer to the pedestal that might be just out of reach

    So with my setup, I can just not plug in both at the same time. Other than sticking your finger in the shore power inlet, a failure of the transfer switch would not be catastrophic.

    Incidentally, when looking for a switch and learning how they work, I found that the Furrion F50 (model # ?) advertises a mechanical interlock for this very reason. I couldn't find any pictures and I didn't want to pay another $50 for an unknown.
    I pretty much did the same thing, but I still have to go out and start the generators as they are Honda EU2000 with the pull cord. I hard wired them into a transfer switch so the always stay plugged in, no running a cord to the trailer outlet. I also converted them to propane so I do not have to lug around gas. Only difference is that my outlet I plug into at the rear of the trailer is isolated from the shore power outlet on the side of the fiver via a transfer switch, they are not connected.

    If you are saying that the outlet you installed on the back for the generators is connected and energized along with the shore power outlet with no isolation, then I agree, that is a big problem.

    I will see if I can sketch what I did with my setup as it appears you are trying to do the same thing. So maybe I did not understand your original question.

    DAN
    2016 Reflection 323BHS
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  9. #9
    Seasoned Camper
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    So here is a simple diagram of how I set up my system. I used two PD transfer switches to allow me to connect and isolate three independent sources, shore power, on board generator, and inverter. Shore power is default, but if the generators or the inverter are running, the system will stay engaged on those sources, even if I plug in shore power. I know this because I have made the mistake several times over the years. If we go dry camping and I inadvertently leave the inverter running, when I get home and plug into shore power, it stays on the inverter until the battery goes dead (don't ask me how I know this). Alternatively, if I am on the inverter and I go out and start the generators, it stays on the inverter. Again I know this because I have made the mistake numerous times. The important thing is that nothing has ever been cross connected.

    Hope this helps and gives you all some ideas.

    DAN

    Click image for larger version. 

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    2016 Reflection 323BHS
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  10. #10
    Seasoned Camper
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    Quote Originally Posted by traveldawg View Post
    Dan,
    Isn't the inverter AFTER the transfer switch? Thus power is supplied to it whether it is on shore power or generator? Most arrangements I've seen had a power protection device, then xfer switch, then breaker panel, then loads in that order when supplied from shore power; on generator it was the same except no power protection device, so: xfer switch, breaker panel, then loads (including inverter power/input).
    See above for what I did with my system. One critical item not shown is that I have removed the converter circuit and isolated it from the inverter. So the converter is only connected when I am on shore power or when the generators are running. I had to install a separate breaker panel to accomplish this and feed the converter independently from the trailer breaker panel. You obviously don't want to be charging the batteries when you are running on the inverter.

    DAN
    2016 Reflection 323BHS
    2006 5.9L Ram Megacab

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