Generator power but no Shore power

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wvirnwkr

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Joined
Mar 22, 2013
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7
When Generator is running I have power to all equipment. Stop Generator and plug in shore power cord and I have nothing. Shore cord power into coach comes in to small junction box at top of breaker box and says transfer switch and has power coming in from shore cord. There are also hot-black and ground-white wires coming in labeled generator and wire nut to coach wire, standard 12/3. Since I have power when running generator but no power when cord is plugged in is the transfer switch bad? All breakers have continuity but no power to them when cord is plugged in. I have searched and cannot find any additional breaker that need to be energized although it seems that something is keeping power away from breakers from shore power cord. This is a 30 amp system on a 89 Class A Granville. Can I disconnect the generator service wires (not run generator) that go to coach wiring and wire nut to shore cord to get power to breaker box. Any help appreciated.
 
Sounds like your Transfer Switch is not working.  Most likely culprit(s) are (1) the actuating solenoid (open), (2) the connection to the solenoid, (3) dirty/pitted contactor points, or (4) contactor points are not moving when actuating power is applied (not switching between Shore and Genny).
 
Thanks Walt. No mechanics are visible. All I can see are the wire nut connections. Mechanics must be under the box. I will have to dig deeper into breaker box. 
 
[ Shore cord power into coach comes in to small junction box at top of breaker box and says transfer switch and has power coming in from shore cord. There are also hot-black and groundwater wires coming in labeled generator and wire nut to coach wire, standard 12/3.]

Two questions: 

1. The SP Cord that has power from the Pedestal connects to what??????? 

2.  When you say the Gen is wire-nutted to the "Coach Wire" do you mean the wire that is supplying main power to the on-board CB Panel???

In a typical installation the SP and Gen Power cords will come into a box ahead of the CB Panel and connect to the fixed points of a contactor(s) and the CB Panel will connect to the switchable points of the contactor(s).  In your installation it sounds like some one has removed the Transfer Contactor and hard wired the Gen to the CB Panel (There are also hot-black and groundwater wires coming in labeled generator and wire nut to coach wire, standard 12/3).

You said SP Cord power is coming into the Junction Box, to what does the SP Cord connect in the Junction Box and where does the SP Cord connection, if any, go upon leaving the Junction Box????  Where does the Coach Wire that the Gen connects to go.??

Lot of questions but your answers will localize the problem.
 
Walt: Thanks again. I found the "guts" to the transfer switch. Everything looks new and I checked all connections for tight. The point assly stays in the upper position (generator) . When pushed down to other set of points (shore) I get power to breakers and 110v inside all outlets work . I suspect the coil that pulls the points to lower position is not functioning. Guess New switch is answer or just engage points to lower position for shore power using wood or plastic to hold in that position and remove to use generator. Thanks  Mike
 
Or, as you suggested, get rid of the transfer switch entirely by connecting the shore power cord directly to the breaker box.  Then connect the generator to a matching outlet in the compartment where you store the shore power cord.

When you disconnect from shore power and stow the cord, plug it into the generator outlet and you'll have generator power.  When you want shore power, unplug the cord from the generator socket and plug it into the shore power.
 
Mike, my wiring diagrams are over at the MH I can check tomorrow, in the mean time I am going to go from memory.

Does the Transfer switch look like it has been replaced.  The reason that I ask is that the Gen should take precedence if you have both SP connected and  the Gen running. 

That being the case, the Gen is normally connected to the N/O (normally open) points the SP to the N/C (normally closed) points and the actuating coil connected to the Gen.  With Gen off the contactor is not picked (actuated) and the power flows from SP thru the N/C points to the switched points to the CB panel.  When you start the Gen it picks the contactor and disconnects the SP and power flows from the Gen to the N/O points to the Switched points to the CB Panel.

1. To what was the actuator coil of the Xfer Switch  connected.

2.  Did the Xfer Switch pick (actuate) with Gen power present.

3. Have you measured continuity of the actuating coil.

There is a possibility that there is a second relay in the Xfer Switch that disconnects the power to the actuator when picked with Gen Power.

It is logical to me that you would be running on SP more often than Gen therefore the SP should pass thru the Xfer Switch by the N/C points.

I hope this makes sense to you.  I will get my Wiring Diagrams tomorrow.
 
Walt: The transfer switch looks original. I did not have the switch opened up when the gen was running . I now have it open and will experiment further. When I opened the switch and looked at the points they were in the upper mode(away from coil)  and I assumed thats where they were when gen was running. I shut gen off and gently wedged points to lower position(toward coil) and got 110 thru coach off shore cord. Sooo the coil would not pull points down with power (shore) on. I had to as I say gently wedge points to lower position toward coil.  Thanks  Mike
 
Good description, the problem has to be either: (1) the contactor coil is open, or (2) not receiving power to pick the contactor.

1.  Continuity can be checked with an Ohmmeter.  Remove SP and turn Gen off, isolate the pick coil by removing the pick wire(s), measure the resistance of the coil.  The resistance of the coil will depend on whether the pick voltage is 120vac or 12vdc.  If coil is open you will have to replace the Contactor.  If continuity is good then:

2. Reconnect wires to Contactor pick coil, reapply SP and then measure voltage at Pick coil start with 120vac and work back to 12vdc.

Does your Xfer Switch have a Control Board in the unit.  If so the Switching power (Contactor Pick Voltage) may be 12vdc.  The Control Board, if there is one, will sense the input SP and apply the pick voltage.  Can't go much further without knowing whether you have a Control Board.

The most likely suspect is the XFer Assembly, they are readily available on line.  Let me know what you find.   
 
Knowing the make and model of the auto transfer switch might help. We can likely find some pertinent info via the internet on your model.
 

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