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Randall, RVIA Certification
Category: RV
Satisfied Customers: 11642
Experience:  RVDA/RVIA Master Certified Technician with many years experience.
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Everything works great as as I am plugged into 30 amp. The

Customer Question

Everything works great as long as I am plugged into 30 amp. The minute I plug into 50 amp I have compressor 2 pop the breaker and even burned up the 110 volt wire going to compressor 2 relay. Repaired wire and plugged into 30 using the adapter both compressor work great. Even checked amp draw at both compressors and each one is pulling about 8 to 9 amps when running. Also blows my high speed fan fuse. Have any idea what else to check or could it be the EMS controller?
Submitted: 2 years ago.
Category: RV
Expert:  Randall replied 2 years ago.

If you are correct about the plugs...........a 30 amp plug has 3 prongs and a 50 amp plug has 4 prongs, then one of two things is most likely happening. Either your cord or panel has a problem on the 2nd leg OR the pedestal has an issue and isn't delivering the proper voltage AT the service location. Sounds like you have a good meter so you should be able to check that pretty easily. And just so you know, you really shouldn't try running two A/Cs on 30 amps. That is only 3600 watts total power available. EACH A/C can draw over 20 amps on a hot day. They are rated at 95 degrees, but the ambient temps on the roof can reach 130 or more which increases the amp draw by another 7 amps or so on each one. The amps. So check the voltage on each leg of your service, both at the source and at your load center. And check the amp draw if you can. Somewhere that second leg is pulling more power than it can safely deliver. Another possibility, is that you have the water heater on or some other large draw on that leg. Turn all other AC loads off and check it. The fridge can be about 500 watts on AC mode and the water heater another 1400 watts. That would cause that leg (if both on the same one) to be overloaded. Hope that proves helpful here. Please get back to me if you need more as all follow ups are included in our fee. R.J.

Customer: replied 2 years ago.
I have a EMS on this coach and it will run both a/c s at the same time on 30 amp it automatically shuts down my hot water heater and if the amp draw is to much because of something else running then it shuts down compressor 2 and #2 fan and then electric on refrigerator and the refrigerator switchs over to gas. As I said everything works great on 30 amp and not on 50 amp.
Expert:  Randall replied 2 years ago.

I saw that.........but, if it isn't working and it might not be.........then damage can result. Check the source and then the voltage at your service panel and we can go from there. Testing is the only way to track this down.

Expert:  Randall replied 2 years ago.

Please keep in mind that taking voltage readings alone won't always show the true condition of a circuit. Breakers and relays can open up either partially, or totally under load. Let me know what you find here.

Customer: replied 2 years ago.
I check the voltage at my panel when it is hooked up on 50 amp service I have 125 coming in one leg 124 coming in on the other both legs to equal the 249 volts. I've even disconnected all the wires from the box that went to the plug and ohm them out it shows me same resistance on all the wires from the plug to the box. Turned on compressor 2 breaker and it popped turned it back on and it didnt pop but the fan relay in the basement air keep clicking and fan did not start. Didn't want to burn up any thing so I plugged it back into the 30 amp and turned on the breaker and the relay clicked a couple times then the fan started and the unit is running fine. I checked the voltage while relay was clicking and voltage was 123 volts the same as it is with it on the 30 amp. On 50 amp one side read 125 and the other 124 when the clicking was going on the one side read 125 and the other 123. After unit was running on 30 amp for awhile the relay started clicking again it is the high condenser fan relay that is clicking.It did it before on 50 amp service and on 30 amp one time before and then worked fine. Has been working fine on till i tried to put it back on 50 amp.
Expert:  Randall replied 2 years ago.
Some load shed devices ONLY work when you are on a 30 amp hookup. USUALLY no need for them when on a 50 amp service. I mentioned earlier, you really need to be able to put a load on each leg in order to see if it really is capable of delivering the proper amps as rated. IF you have a breaker going bad it may not function properly under load. I don't know what else to offer here and so I will opt out of this and let another tech give some input if they can. Kind of a head-scratcher at this point! I will keep an eye out on this post and go and take a look in some of my manuals and see if I find anything I might not have thought of here. And please give me the make and model of your load shed unit. Thanks! R.J.
Customer: replied 2 years ago.
Here are pics of what I have
Expert:  Randall replied 2 years ago.

I put this back on the board for other techs to look at.........and I will check my manuals to see what I might have. R.J.

Expert:  Randall replied 2 years ago.

I have been giving this some thought.............and I am wondering if you have a cord reel in use? Sometimes, they will work fine except wen under a larger load (like a 2nd A/C) and even though they read proper AC voltage with a meter, they "open up" on one leg under load. I have seen this once before on a Monaco with a reel. Either that, or someone mislabeled the sides on the system and what says "30 amps" is really 50 and vice versa. I don't know any other explanation. R.J.

Customer: replied 2 years ago.
No reel have an appointment for someone to look at it on monday.
Expert:  Randall replied 2 years ago.

Please let me know what it turns out to be as several of here on site are wondering about it. Thanks!