We lost our shore power

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tvfrfireguy

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Yesterday we pulled into our site (air temp 95 degrees) and I plugged in our 50 amp cord.  My wife said she could hear a buzzing under the floor in our alpenlite 5th wheel.  I unplugged the cord and the buzzing quit.  I plugged the cord in again and we had no power.  I then started our onan generator and we had power.  I then checked our site hookup and there was 120 volts on each leg of the female outlet.  With the generator off, I plugged the 50 amp cord back in and we had power for about forty seconds and by wife heard a loud click.  The power was out so I climbed in the belly of the trailer and had a look see.  I took the cover plate off the generator transfer switch box and it smells burnt.  To replace this box looks like something I can do but before doing this I am wondering what would cause this to happen.  It looks like an expensive part and I would hate to replace it and then fry the new one.  Has anyone experienced this problem?  Thanks,  Dave
 
Hard to guess what went wrong. Maybe 220V between hot and ground on the power pole? Or maybe just a defective transfer switch?

If you are still at that same site, check voltage from each of the hot pins to both neutral and ground - both should show 120V (give or take a few volts). And there should be 240V between the two hots. IF that checks out OK, odds are you had a transfer switch failure, but hard to say why.
 
IT may also be the Transfer switch ... Just fried.

My transfer switch "Defaults" to shore power if fried in all but one pan  Once the generator starts and it sees gen-set power then the electronics start counting down and when they reach the end of their count CLICK the switch transfers.

However that's mine.... Others may have active electronics on the shore side too.

Oh, the one failure mode that will leave me stuck with no shore power... Welded relays,  Sometimes the contacts "Weld" in one position or the other and won't transfer the load.
 
Most recent model auto-transfer switches work as John describes - the genset powers the relay and it switches after a slight delay to let the generator speed stabilize. Yours still does that, so that part of the function is OK. Sounds like there is a failure on the shore power side, tho. Maybe corroded (and now burned) connection where the shore cable attaches to the switch?  That's where I would look first for the problem. The switch itself may still be OK.
 
Thanks for your replies.  I will have to remove to see where the damage is.  The connections seem fine.  This is a 2004 Alpenlite and hasn't had that much use.  It looks to me whether you buy a cheap RV or a upscale one, they all use the same appliances and parts.  I just replaced the Dometic Heat Pump.  It was used a few times and self destructed.  I wrote the factory and they told me " to bad, so sad".  I built homes for years and had I used the same quality the RV Industry uses, I would have been run out of town.  Dave
 
The transfer device (ATS) will select the shore power side with no power to the coils and then shift to genset if it is powered up. You don't say how lod the RV is but the contacts will burn in time and the coils do also occasionally fail. It would sound like yours has badly burned contacts and what your wife . heard was arcing because they were not closed completely. After a brief period they failed. When you shifted to the genset you would have caused the shore power side to open and then to snap closed when power was interrupted from the set. But since the contacts were burned, they soon failed again.

If you shift the power from shore power to the genset when under load, it will very quickly burn the contacts and it can cause other serious problems. If you are not the first owner of the RV it could be that this has been done by a previous owner. It is especially bad to start the genset when you have heavy loads like an electric heater or the air conditioner on as it will soon shift to the genset and in so doing there will be a huge surge because the two power sources will not be in phase. That kind of thing can and does destroy ATS units.
 
A good starting point is the ATS (Automatic Transfer Switch) Now: If you are uncomfortable working with voltage and current limits that can easily kill you get professional help. As it happens I'm trained in this kind of thing so I'm comfortable doing it.

Locate the ATS, remove the cover and CAREFULLY check, using a proper meter or test light, for power on the shore power input, and the output terminals.    On my rig ti's fairly easy to access the ATS (only two screws need be removed)

From there it gets harder.. I had a screw loose on the power inlet.
 
Thanks for your help.  I ordered the new switch box today from an outfit on the internet (RV Powerhouse.com) for $130 bucks.  I'm glad I checked around because Campingworld wanted $275.00.  It looks like an easy changeout.  I have talked with others of late and they tell me others  who have had this problem have had a 50 amp plug installed on there Gererator and then wire their shore power directly to the breaker box.  If this new switch goes south on me I will be carring some large wire nuts and hook up direct using the burnt switch box as a junction box.  Thanks again for your input.  This forum is great!  I don't feel like I'm at the mercy of the dealer anymore.
 
slumbert55 said:
it all comes down to what i learned in electronics  "DON'T LET THE SMOKE OUT, YOU HAVE TO KEEP THE SMOKE IN THERE IF YOU DON'T IT WON'T WORK}
Click to expand...

LOL, yes, Electronics all run on magic smoke.  And you are quite right, if you let the magic smoke out, It stops working.

Not only that but Magic Smoke smells real bad
 
Dave,
If you "fry" the new transfer switch - you really need to find out why. Just hooking up your 50 AMPcord to the burned out switch sounds like you might put generator power into the shore power circuit if you were to start your generator while you are still plugged into the shore power receptacle. :eek:

Green lights and soft breezes,
 
Thanks Roland:  I wasn't very clear on my intentions.  If I have another problem with the new transfer switch, I will disconnect the generator and wire nut the shore power directly to the breaker box bypassing the switch.  When I return home, I would have a female 50 amp plug installed on the generator and eliminate the transfer switch altogether.  Dave
 
Dave,
If you loose another ATS and decide to hard wire your service; you may still want to find out what is causing the problem. I expect if you loose it, it will not me at the same site your were in before. Also I have not ever heard of frying two ATS's in a row. They are relatively heavy duty, not complex and usually last for years. Make sure that you shut off your A/C's and other heavy loads before you shut down the generator. Or switch from gen to shore power. You may have arcing at the contacts and this could cause damage. Just a thought.

Green lights and soft breezes,

 
If your intent is to replace the ATS for now, I think I'd not put the 50 amp outlet on the generator just yet... Rather keep it, and in fact get a 2nd 50 amp outlet and a 50 amp plug.. .Next time the ATS goes out replace the ATS as follows

Line from ATS to distribution panel.. The plug

Line from Generator, An outlet, painted red or orange and labeled "GENERAOR"

Line from shore inlet left black and labeled "Shore Power"

Then you can pulg in as needed without doing a lot of extra work

By the way. I finally figured out what the buzzing was... It was power arching over the contact on the relay in the ATS that had failed.  You may have had a bug in your system (Real bug, the kind with many legs)

Used to happen all the time at my parent's farm. Bug would crawl into the pressure switch on the water pump, I'd turn off power, climb down into the pit, remove the cover, clean the contacts, replace cover, climb out of the pit, and restore power.  Good till the next system bug happened.
 
Thanks John:  I wish I had not ordered that new transfer switch.  Your solution is well thoughtout.  From this I have learned not to get in such a hurry.  Your solution would be trouble free, inexpensive, and simple.  Thanks for your help,  Dave
 
Well... My solution has another advantage too.. If you choose to put in a Auto-Former.. You just plug it in to the shore power "outlet" where the ATS used to be.  and it's installed.  (you don't need one with the generator)

I would keep the ATS even if you decide to use the system I describe.  Increases the re-sale value of your rig.
 
An autoformer increases the voltage to the load when the source voltage is low, increasing the current draw accordingly, and exacerbating the problem.  I don't recommend them at any time.  If the park voltage is low enough to use one, then either move to a different site, different park or run the generator.
 
Dave,

Not John. A Hughes Autoformer is a rectangular can about 14"high x 8" wide and 12" deep and weighs about 45 lbs. Has either a 30 or 50 AMP receptacle on one end and the appropriate short power cord (3ft.) coming out the opposite end. Inside is a step up or buck transformer and some related electronics. When the autoformer senses a voltage drop, of the incoming power, below 116 VAC it goes into boost mode and increases the voltage by 10%. This costs about 1 to 1 1/2 AMP to accomplish. 115 VAC would become 126 VAC; 100 VAC would become 110 VAC and so forth. When the incoming voltage increases above 118 VAC the autoformer comes out of boost mode. If the incoming voltage drops below 94 VAC the autoformer stops boosting and does nothing. The increased voltage level allows inductive motors like your A/C motor to run at a reduced amp draw and at a cooler temperature. Low voltage is a prime contributor to A/C motor failures. Autoformers do not alter power up stream in the park. A 50 AMP autoformer is about $525.00. Expensive, but sometimes useful to have.

Green lights and soft breezes,
 
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