Shore power is hot, 50 amp, but bus not getting power

Topic: Shore power is hot, 50 amp, but bus not getting power (Read 1236 times) previous topic - next topic

Shore power is hot, 50 amp, but bus not getting power

May 09, 2018, 04:48:31 pm

I was running the air conditioner plugged in at a state park, 50 amp, when all of a sudden the air conditioner went off and the POWERWATCH, A.C. Polarity meter needle was bouncing from left to right with a scratchy noise. So, I went out to check the breaker outside on the post and it had not tripped. But I turned it off to further investigate. And turned off the air conditioner.

I tested the 50 amp. at the post. Fine. Then I checked my 50 amp cord. Fine. So I was getting shore power but not inside my coach.

My generator works, so the Air conditioning then worked fine and the A.C. Polarity Powerwatch meter worked properly. Just not getting shore power.

I did a little research here on the forum and "transfer switches" came up recently. I do think mine is pretty old. I'll attach a photo. Might even be original. However, mine is not by bed. It is attached to roof of battery bay. So another question could be that if I bought the Progressive Dynamics PD52V 5200 Series Automatic Transfer Switch - 240 VAC, 50 Amp from Amazon - would it work? Not on a floor, but same place as current one?

Susan Hammer
1990 Grandvilla 36 ft

Re: Shore power is hot, 50 amp, but bus not getting power

Reply #1 – May 09, 2018, 05:01:58 pm

Are you sure it is the transfer switch? How did you test shore power. With some testers it will show you have correct voltage but when you put a load on it the voltage will be about zero.

Did you check cord where it connect to coach and make sure it is twisted tight?

Re: Shore power is hot, 50 amp, but bus not getting power

Reply #2 – May 09, 2018, 05:02:38 pm

Susan,

Sounds like you are mechanical-- checking the ATS is not difficult. When you said you tested the CG outlet, assume with a voltmeter and all readings were correct. If you like, would be happy to post "what readings should I get between what sockets".

With shore power disconnected, generator off, inverter off:

Remove lid.

Check carefully for any burned wires-- if so, cut them back to good copper and reattach or run new wire.

Verify none of the lugs securing the wires are loose.

Let us know what you find, or post picture.

And, then after doing the above (assuming it all checks out) we can post how to troubleshoot it with your voltmeter.

Re: Shore power is hot, 50 amp, but bus not getting power

Reply #3 – May 09, 2018, 05:16:06 pm

Turbojack,

I will check the cord, thanks....

Re: Shore power is hot, 50 amp, but bus not getting power

Reply #4 – May 09, 2018, 05:30:26 pm

Brett,

I will open ATS and look. And yes, please post: "what readings should I get between what sockets".

Susan

Re: Shore power is hot, 50 amp, but bus not getting power

Reply #5 – May 09, 2018, 05:34:32 pm

The 50 amp outlet:

The two outer straights are the HOTS
The center straight is the NEUTRAL
The center round is the GROUND

So:

Between either outer straight and either center round or center straight should read 120 VAC.
Center round to center straight should read ZERO.
Outer straight to outer straight should read 240 VAC.

BTW, spent a lot of time sailing (and a few VERY fast hours in a race boat) on Elephant Butte when we lived in Albuquerque several decades ago.

Re: Shore power is hot, 50 amp, but bus not getting power

Reply #6 – May 09, 2018, 05:40:58 pm

Brett, I opened box and took a photo, attached. I can't seem to attach an image with this reply box. I will try some other way. Maybe I will message you.

Susan

Re: Shore power is hot, 50 amp, but bus not getting power

Reply #7 – May 09, 2018, 05:46:03 pm

Brett,
Well I don't know how to attach a photo unless I make a new topic. It looks very clean. no frayed ends anywhere.

Is there some way to test the ATS?

Re: Shore power is hot, 50 amp, but bus not getting power

Reply #8 – May 09, 2018, 06:22:33 pm

The problem may or may not be at the ATS, did you move the coach to another pedestal? Regardless, you should have one of these:

Re: Shore power is hot, 50 amp, but bus not getting power

Reply #9 – May 09, 2018, 08:38:51 pm

"I don't know how to attach a photo unless I make a new topic."

Write your text, click preview. Preview gives you options to add photo.

Re: Shore power is hot, 50 amp, but bus not getting power

Reply #10 – May 09, 2018, 10:05:27 pm

OK, spent some telephone time with Susan.

She is fine and both A/C's running on generator. We talked through troubleshooting she will do in the morning.

She has a good handle on it and knows how to use her voltmeter.

Re: Shore power is hot, 50 amp, but bus not getting power

Reply #11 – May 10, 2018, 04:24:19 pm

Ok, Brett, I started to take apart the outlet on the bus that the cord goes into. I took out 4 bolts, one each corner of the squarish shape. I tried to pull the outlet down then, but it only drops an inch and a quarter or so. Not enough to see anything. Is there something else I am supposed to release?

Re: Shore power is hot, 50 amp, but bus not getting power

Reply #12 – May 10, 2018, 06:26:59 pm

Long conversation with Susan.

She is on the hunt. Going to pull the outlet where the shore power cord goes into the coach and check it-- both by verifying that wires are clean, not burned and lugs tight and then with her VOM (set to OHMS) check that each of the 4 wires goes where it should.

If that proves out, ONLY the shore power cord is questionable-- and it has been run over by the coach while back.

She/I will keep the Forum posted.

BTW, it always does my heart good to see an owner learn how to trouble shoot a problem. In this case we only have 4 wires, all color coded that she is verifying are correctly wired.

Re: Shore power is hot, 50 amp, but bus not getting power

Reply #13 – May 10, 2018, 09:03:03 pm

Need to take your vom and see if you have the right voltage at the end of the power cord. If everything checks out on the power cord. See if he can plug the power cord in and check voltage on the end of receptacle where the coach power cable connects to it. Be careful and don't get shocked or short anything out

Re: Shore power is hot, 50 amp, but bus not getting power

Reply #14 – May 10, 2018, 09:21:44 pm

I finally got the outlet to drop down. (After unscrewing the control board for the drains, which was in the way of getting screws out of the mini wall separating the battery bay and the outlet area, and taking the old cable and telephone parts out, I could finally see how to get the outlet to drop. (So many screws I am praying I can put it all back together.

I think the neutral looks corroded or burned.

Perhaps I need to get a new outlet. I'll attach photos.

I'll check the ohms tomorrow. It's been a 100 degree day here at the Butte.

Re: Shore power is hot, 50 amp, but bus not getting power

Reply #15 – May 11, 2018, 08:53:05 am

The neutral wire does looks corroded. When there is a loose connection you will see the insulation start to melt / discolor and I do not see that in the pictures. Are the screws tight that hold the wires. From what I can see in the picture it looks like the outlet is not damaged but do not know what it looks like where the neutral wire is contacting the receptacle.

If the screw to the neutral/ white wire was loose then that could have been your problem.

You need to be very careful with neutral problems when dealing with this 50 amp 240v power. The neutral is used to carry the imbalance back to the power pole between the two phase conductors. If the neutral goes bad, then the phase that has a high load will get low voltage and the phase that has a light load the voltage will go high. If course when that happens items do not like high or low voltage and will let the smoke out.

Re: Shore power is hot, 50 amp, but bus not getting power

Reply #16 – May 11, 2018, 09:54:09 am

Quote from: turbojack – May 11, 2018, 08:53:05 am

when that happens items do not like high or low voltage and will let the smoke out.

X2.......No one at our 'Park' admitted to fault (naturally) when we fried our cables + the ATS, even though they put new breakers in after the fact! That's when I bought a EMS and trusted NO pedestals after that. That SMELL is one of the worst tip-offs any of us can have, you don't know, at first, where it's coming from and, most importantly, is the coach going to catch fire? We lucked out, only (ha!) cost us a CB+change to renew everything. Scary stuff!

Re: Shore power is hot, 50 amp, but bus not getting power

Reply #17 – May 11, 2018, 02:59:17 pm

Quote from: Susan – May 10, 2018, 09:21:44 pm

I finally got the outlet to drop down. (After unscrewing the control board for the drains, which was in the way of getting screws out of the mini wall separating the battery bay and the outlet area, and taking the old cable and telephone parts out, I could finally see how to get the outlet to drop. (So many screws I am praying I can put it all back together.

I think the neutral looks corroded or burned.

Perhaps I need to get a new outlet. I'll attach photos.

I'll check the ohms tomorrow. It's been a 100 degree day here at the Butte.

Susan, I applaud you. You are doing great. Don't give up.
John

Re: Shore power is hot, 50 amp, but bus not getting power

Reply #18 – May 12, 2018, 01:28:47 pm

John, thank you very much! Need the encouragement!

Re: Shore power is hot, 50 amp, but bus not getting power

Reply #19 – May 12, 2018, 04:02:58 pm

Susan,

You will get it worked out. Why? Because you were smart enough to ask for help and then learnt what you did not know! If everyone did that things would go so much smoother.

Keith

Re: Shore power is hot, 50 amp, but bus not getting power

Reply #20 – May 13, 2018, 05:44:54 pm

John Morales and Keith & Joyce,

Thanks for the thumbs up! I love this forum. It's been a life line for me several times.

When I further took the assembly apart the red wire that looked so good was actually very compromised as well. Out of the 6 copper wires inside the red hot only 2 were long enough to get connected. The "person" had cut 4 copper wires too short when he stripped the outside red sleeve.

Then further observation had me google the name on the side of the outlet to see what it was called specifically and where to order. It turns out the person put in a 30 amp shore power outlet instead of a 50 amp!

At the parks I have stayed in I only plugged in 30 because that's all they had. So I never noticed it. Also, I am usually boondocking. It was bound to happen eventually.

I ordered the part, will be here Wed., so I'm resting in order to get ready for my next technical challenge! Installing a shore power outlet! 50 amp.

Happy Mother's Day all you mom's!

Susan

Re: Shore power is hot, 50 amp, but bus not getting power

Reply #21 – May 13, 2018, 06:41:25 pm

Wow. Good job. BAD job by the original installer. Good luck with the replacement.

Re: Shore power is hot, 50 amp, but bus not getting power

Reply #22 – May 14, 2018, 10:08:37 am

Let's go back to diagnosis...our coach has stopped recognizing 120 vac coming at all from the post or the genset. Happened while we were away for a few days. Fridge went to LP so that's ok. Solar keeps the batteries up though it is raining now and will for several days. Got a call into Father and Son but they are really loaded down for a couple of weeks. All looks good inside the two boxes at the foot of the bed. What would cause FT to mount the one box almost right up against the back of the circuit breaker panel??? Had to hold a driver bit in vise grips to get the screws loose. Holding a mirror down with a flash light on I can see no problems in that box. The one with the two relays has one contact bar that is dark but the contacts look good so maybe it over heated before I bought the coach and was cleaned then. Got any ideas?

Re: Shore power is hot, 50 amp, but bus not getting power

Reply #23 – May 14, 2018, 10:49:28 am

How are you plugged into power? 50 amp, 30 amp or 20 amp?

You have no 110v in coach, no microwave, ac, or anything?

If from generator or shore power is not working in coach then it is looking like problem is the transfer switch.

Re: Shore power is hot, 50 amp, but bus not getting power

Reply #24 – May 14, 2018, 11:25:18 am

If you have a volt meter? Check power at the transfer switch while plugged in to the power pedistal. Should be voltage present on the top side of one of the contactors and passing thru to the common (load) side on the bottom.
If power is on the common (load) side then check the line side of the Main panel for 120v there.
This should give you a good starting point anyway.

Affiliate Notice