Unknown electrical issue

[Shore2Shore]

Ok I hope this is in the right place!

Our 1987 Bounder has 2x rooftop a/c units (coleman delta T) have replaced the fan motor & cleaned the evap coils to make it all as good as it can be.
Has been working perfectly before the freshen up & after.

Now all of a sudden as we are already hitting 100+ F days here in TX the compressor power is shutting off. The units have a low voltage protection built in (with light) that senses low voltage & cuts power to comp & keeps fan running.

Yet last year with constant 100+ days it never skipped a beat

The bounder is 30amp, with original longish cord with new plug.Upon reading another thread on here, mention of possible 30amp socket wear etc, so got a 50 - 30amp adapter and the 50amp socket is all nice & tight.

A week or so ago a similar thing happened on consecutive days & the 5th day the whole town power went out!!! So we thought just the town and not an issue with the bounder

But its happening again (to us) with apparently no one else having issues.Was fine yesterday & all night(only a degree or so difference) so kind of running out of ideas!!!
Dont think its the town again.. Would a shorter/new cord be recommended,
is it just the older design being too sensitive?!

I know with temperature increase, more strain on the town/park supply due to a/c's being cranked up/turned on ,fans etc. But the whole time the one unit we use has been perfect. Even after cleaning etc, even when its only the odd degree different.

No other appliance thats running in the bounder is having issues ie running slow or not at all.


Maybe it is just the old units power protection being too picky (I dont know if new units have protection systems that work differently and keep the compressor running but just lowers the output?) This 24 year old unit works fine every other time, just seems like power fluctuations kick the protection in. Yet people with 5ers etc still have a/c working.

Sorry for the ramble but pretty much out of ideas apart from a new roof unit. Or a portable unit inside connected to the power pole 20amp connection.

[RJay]

Hi Paul,
I think what your experiencing is compressor stall caused by a low voltage condition where you are. Take a voltage reading at the power pedestal and let us know what you find.

[Shore2Shore]

Thanks RJay for the suggestion, we have been lead to believe its voltage related.

Total brain fart moment, how do you take a voltage reading on the ac power pole?
I take it with a digital multimeter? Which way do you connect the leads?

sorry for the simple question but have only tested dc stuff before !

[Paul R. Haller]

unplug the trailer umbilical anread between the two uppr poles. On a 30 amp the they are the 2 diagnal slots. I think the right L1 120 and the other is neutral. Then between the L1 and ground which is the round pole on the bottom. L1 to neutral and to ground should read the same. 115-120 volts AC. Less then about 107 is low voltage.

I have seen places I stay in on very hot days get down to under 90 volts. That is low!! and trying to run ac that low will eventually fry the compessor and maybe blow the breakers too.
-Paul R. Haller-

[RJay]

Paul, good post. I'll just add that if you want to measure the voltage under load, instead of unplugging the power cord you can back out the plug of the power cord from the pedestal just enough to get your test leads to the prongs on the power cord plug. Taking the voltage reading this way give a better idea of the voltage actually going into the RV.

Since we are getting into air conditioning season, be aware that motors operating for any length of time below 108 volts suffer loss of life and the lower the voltage the more severe the loss of life. When the voltage gets down to between 108 and 110 volts I start my generator to run the airs until the voltage improves.

[codgerbill]

I do believe A.C. motor windings are wound for 115V, 230V, and 460V. They are supposed to have a voltage tolerance level of +or- 10% According to NEMA (National Electrical Manufactures Association) standards. The problem when operating at the lower end of the voltage tolerance is that the current will rise to maintain the rated torque (HP if you will) so at the lower voltages you get a much higher current and also a lot more heat. If the motor is not properly properly protected it will continue on a path to destruction.

[Shore2Shore]

Thankyou for all the advice & hints/tips . Found the digital mulitmeter and the battery just died! So will be going to the store in a few to get a new meter or battery,whichever I find first!!!

Had a feeling that running motors on low voltage cant be good for their lifespin will keep that in mind. Will have to try and get the generator going.

Wonder if the addition of a portable a/c on the seperate 20amp from the hookup would keep going ok?

Thanks again from pretty darn Hot & humid TX.

[RJay]

Paul,
Please keep us posted on what you find so we know what fixed the problem. Thanks.

[JimM68]

Paul, if the voltage is low, then it's low, and will be on the 20 amp line as well most likely.

Get the battery and check the voltage. Rather than messing with a half unmplugged 30 amp RV plug under load, just test ANY AC outlet in the coach. Stick the meter leads into the 2 straight slots, make sure the meter is in A/C and get a reading.

Does the A/C run ok on the generator?
That would be a pretty solid clue.

[wa8yxm]

The two flat blades on a 30 amp outlet are the ones you measure between, Ideal is 120,

On a 50 amp outlet there are 3 flat blades, Center to either side, 120, side to side 240

NOTE: red/black are interchangable when doing AC volts readings.

NOTE 2: This is a no.load test and is basically useless. but it is a furst step.

Once you have a reading at the pole plug in, minimize your electrical use and measure the voltage at an outlet,, Now fire up the A/C and see what happens there.

Suggestion: To measure SAFELY the voltage at a 30 amp outlet, Use a 30-15 amp adapter (This is an adapter that lets you plug a standard 15 amp cord into the 30 amp outlet) and a Kill-a-watt meter set to volts.

Use the Kill-a-watt to measure the outlet inside.

Some folks say they are not all that accurate but the first time compare it to your high quality digital and if they are close, (1 volt is more than close enough) that's good enough.

[Half Dimes]

A plug-in type continuous voltage read-out in very helpful in an RV. There are analog or digital styles as well as led indicators for status at a glance. Even better is an electrical management system with a remote display that will cut power if it drops below or exceeds preset parameters. Ours has saved us a couple of times.

[RJay]

Here's an AC receptacle meter that you can tell what the voltage is at any given time. Very handy.

[Shore2Shore]

Thankyou for all the help and advice Will check out one of those receptacles/line voltage thingies.

Would you believe the past couple of days and the a/c has been fine ,has been about just as hot as when the unit was switching on & off. Some light white cloud cover in spots at times.

Even at peak temps when the thing would normally kick in the safety off it ran faultlessly day & night. Today at 2pm central time it kicked off again.

ran to get the meter & it had already come back on with a voltage reading from various outlets inside the coach of 115-117V AC so judging by this when its running this reading is fine?

Now just waiting for the thing to shut off again so I can quickly see what the voltage is reading!! Although I'd rather it not shut off!!!

Again thanks for all the suggestions etc, will report back with any further installments. Still weird shoving things in plug sockets!

[Shore2Shore]

Update time *sigh*

low voltage light came on & compressor shut off, shoved the meter leads into various outlets ....all reading 118-120V AC?

Looking at the circuit diagrams the front a/c should be on its on circuit/breaker, which is a single pole with 30amp & 20amp in the same breaker. When ever we stretch the main supply it trips the 30amp switch & front a/c and all other electrical items go off too (suggesting the 30amp is the main breaker) so I would guess the breaker for the a/c on its own would be the 20amp side?

Will have to go check out the wiring diagrams again that I got from Fleetwood.