Hidden Generator Relay & Gen Problem

Makes me want to chew nails when someone buries electrical equipment like this, and to make matters worse doesn’t include any signage or manual notice of it being there.

I’ve been troubleshooting shore power works fine but generator runs but doesn’t power anything all day. Wasn’t able to verify gen breaker was functional or not till I found the relay location behind the drivers seat inside that carpeted molding.

Grrrrrr

A tour bus took off my drivers side mirror and shattered the two side windows on my 2011 2551. The shock wave popped the drivers side outlet cover off and the gen problem started at the same time so figured the problem was in that same area. I checked the voltage from the generator as 120v and observed the relay close with shore power disconnected.

Can anyone suggest something else over there that might be causing this problem?

I’ve also checked the breakers and fuses several times, even the three hidden 30a fuses under the bottom Zantrex panel. All good.

So far I’m stumped as to what the problem is. Help!!!  😁

There is a transfer switch fed by both generator and shore power.  On my 2015 2551,it is located behind the driver's seat, behind the carpeted piece on the panel that connects the cab to the wider RV sides.  There are 3 or 4 screws near the top of the carpeted area. They are hidden in the carpet tufting.  Remove the screws, pull the panel and you will find the transfer switch.  Ideally, whether plugged into shore power or not, 20 seconds after the generator starts, it will switch output to come from the generator.   If that transfer switch is defective the generator power won't get switched into use. 

A quick call to PC should have provided this information.

ThruTraffic,

From my reading of your troubleshooting efforts, sounds like you have reviewed and potentially eliminated the most obvious issues.  Just in case I am misreading what you are saying, I'll mention a couple anyway.

The breaker on the generator unit itself would have been my first check--if it's tripped, the unit runs with no output.  Sounds like you're saying that you verified it is functional however.

The transfer switch is the second obvious concern.  However, also sounds like (after some effort) you located the transfer switch, and at that location "checked voltage from the generator at 120v", and also "observed the relay close with shore power disconnected".  If that is generator-produced 120 volts (should have to be with no shore power connection), and if that is the relay closing that applies generator power to the RV circuits, sounds like the transfer switch is doing what it should.

If the above is correct, you covered the most obvious failure points.  I suppose a wiring connection issue is a possibility after a jolt like you took, but since you say you're getting proper shore power, the output wiring from the transfer switch to the power panel must be OK.  If you have power with 120v shore power applied to that wire, you would have power with 120v generator power applied to that wire.  About the only possibilities are that the generator voltage is not getting applied to that output wire (even though you see a relay close), or that the120 volts generator voltage you are reading is just potential with no load applied, and is dropping to zero (or unusable voltage) when actually applied to the load by the relay.  My troubleshooting at this point would probably involved more detailed voltage checks at the transfer switch to confirm exactly which that is.

Wish I could be more help,         Mike 

Yep donc13; Stated in my post I found that switch behind the driver seat and observed it function after starting the generator. I found that relays location by searching this forum.

I presume you checked the output from the transfer switch.  There should be 2 input lines, one from shore power and one from generator.   The output of that switch is goes to the breaker box.  Since you get power from the generator TO the switch. And since the output FROM the switch is common to both.   The only thing that I believe can be the issue is the switch itself.   If the internal relay contacts are damaged, even though the switch clicks, the output isn't being switched.

I could certainly be wrong, but I had a similar issue in an earlier RV and had to replace the switch itself.

Don

I presume you checked the output from the transfer switch.  There should be 2 input lines, one from shore power and one from generator.   The output of that switch is goes to the breaker box.  Since you get power from the generator TO the switch. And since the output FROM the switch is common to both.   The only thing that I believe can be the issue is the switch itself.   If the internal relay contacts are damaged, even though the switch clicks, the output isn't being switched.

I could certainly be wrong, but I had a similar issue in an earlier RV and had to replace the switch itself.

Don

Homing to tackle all aspects of the switch next. Last thing I did was shut off shore power, start the generator and saw that after a few seconds the relay did close and hold. My expectation is that power is getting to the other side of the switch; I’ll know more tomorrow. Since I verified 120v from the generator and the switch works I’d expect to have power to the fuse box from the generator. Looks like I’ll have to pull the pass bed to get to the terminals; no power is getting to the breakers. Are there any more hidden devices or connections between the transfer switch and the panel? 

ThruTraffic,

If your coach is equipped with an onboard Electrical Management System (EMS), those units can be connected either in the shore power feed to the transfer switch (monitoring/protecting only shore power), or in the output feed from the transfer switch to the power panel (in which case they monitor/protect both shore and generator power).  If you happen to have one and it is installed in the circuit after the transfer switch, it is possible that it is allowing shore power to your power panel because it is within limits, but is interrupting generator power because some aspect is out of limits.

That would be the only thing I could think of as a possibility between the transfer switch and power panel--to my knowledge there should be no other device/connection between the transfer switch output and the power panel input--just a single electrical cable transferring the output of either shore power or generator from the transfer switch to the panel.  That's why if you have correct A/C voltage with shore power (absent an EMS), that indicates that part of the connection is good, and the problem almost has to be at the transfer switch or the generator.

The best place to check power is at the actual output connection on the transfer switch where the cable to the power panel connects.  That point should be hot when shore power is plugged in, and again when the generator relay closes.  Given your symptoms, I would expect to see voltage at that point with shore power but not generator, and then would track the circuit back through the transfer switch to see where you're losing it.

Mike

Mike: you make an interesting point regarding the wiring of the EMS.
Seems it would provide most protection on the load side of the transfer switch unless there is some compatibility issue.
Do you know how they wired yours?
I'll ask them about this next week also.

Jim,

I'm not sure how mine is installed, I'm going to check.  Since delivery in February I've only fired off the generator for a short time, and didn't notice the readout on the EMS panel with it running.  However I assume Phoenix wires it to monitor/protect both shore and generator power unless there is some characteristic of generator power that creates frequent issues with the EMS tolerances for power resulting in shut-offs.  All I know right now is that the installation manual for the Progressive EMS I have says they can be wired either way.

I'm not sure what Phoenix was doing about EMS in 2011 when they built the coach ThruTraffic has, so I don't know if the above even applies to his problem.  But, given his symptoms, it's the only thing I know of that could be an issue on the downstream side of the transfer switch.

Mike

Well, kiss my grits. Looks like mike gets the cigar!! 

I disconnected shore power, fired up the generator, waited until I heard the transfer relay close for the generator feed, same thing nothing ran on generator power as expected.

I went to the EMS display and sure enough there was a 136 volt disconnect error. I switched EMS to bypass, heard the microwave beep and the A/C came on.

So this problem has never presented itself before, curious as to why not. This anecdotal experience is saying that the generator now has a higher output voltage for a few seconds, high and of duration enough to trip out EMS.

So I’m back in business, knowing how to solve it when/if it happens again.

Never thought of an EMS since you show a 2011 model and an EMS isn't standard.

Does it take about 20 seconds from when the generator starts for the transfer switch to click on?   If it does, your generator should not put out that much voltage after it stabilizes.   Have the generator serviced.    If the transfer switch clicks pretty much as soon as you start the generator, then the transfer switch is no longer set for the delay (there is an internal setting to delay or not) or the switch no longer "honors" the setting or it's one of the switches that doesn't have such a setting and (your option obviously) should be replaced with a switch with a delay.

Don

https://www.rvwithtito.com/download/Onan4000MaintenanceManual.pdf

Adjusting the generator engine rpm changes the output frequency and voltage. See page 80,  section 8-13, spec D and later.

Try connecting your voltmeter to an outside 120v socket  and measuring the voltage while tweaking the altitude adjustment knob (mixture screw) before messing with the throttle stop screw (governor).

https://www.rvwithtito.com/download/Onan4000MaintenanceManual.pdf

Adjusting the generator engine rpm changes the output frequency and voltage. See page 80,  section 8-13, spec D and later.

Try connecting your voltmeter to an outside 120v socket  and measuring the voltage while tweaking the altitude adjustment knob (mixture screw) before messing with the throttle stop screw (governor).

Good advice from CalCruiser above, I'd add to start by getting informed about the whole process from page 76, sec. 8-9.

You must have a 4000W test load available and, if frequency is correct and voltage is not correct, the voltage regulator is defective.   See page 6-31, table 6-14.

Thanks for the assist guys. Yep, gen test/service is warranted. This just started out of the blue and the EMS kicking out on generator hasn’t ever been a problem before.

Yes there is a delay which I also would have assumed allowed the generator to settle down. The one time I measured the voltage, node somewhere at the beginning of this thread the result was 120v.

True, EMS wasn’t standard in 2011. I installed it last year. Not sure I like it. I ‘thought’ EMS managed voltage but it appears it just denies any voltage greater than 135v. About half the RV parks I’ve stayed at are above that and many over 130. So about half the time the EMS is disabled, by me, so I can have shore power. 🤬