A/C tripping breaker

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gaoneal02

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I have a 1988 Winnebago 37' Elandan with dual Coleman model 6779B installed. Both units are acting the same, both will trip in the heat of the day (100-105 degrees). They run great in between 8pm-11am, but after that, they will run for 10-15 minutes, trip the breaker, leave them of for 1-15 minutes, then reset the breaker and on goes the cycle. Anyone know about this?
 

kdbgoat

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Have you pulled the top covers and cleaned the coils? Dirty coils will cause high head pressure, and essentially overload the compressor motor, causing high amp draw. Also, if the breakers have been tripped a lot, they could be getting weak.
 

John From Detroit

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As the world warms. The compressors have to work harder as the pressure in the systrem gets higher and higher. the harder the compressors work the more current they draw till TRIP

As the other Poster suggested a good coil cleaning may fix it as this allows air to flow more freely, and cools things off.
 

solarman

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gaoneal02 said:
I have a 1988 Winnebago 37' Elandan with dual Coleman model 6779B installed. Both units are acting the same, both will trip in the heat of the day (100-105 degrees). They run great in between 8pm-11am, but after that, they will run for 10-15 minutes, trip the breaker, leave them of for 1-15 minutes, then reset the breaker and on goes the cycle. Anyone know about this?

aside from the usual "clean the coils" suggestions, I will ask how old are these units and when was the last
time they had the run capacitors replaced ?

run capacitors dry out over a period of time, especially in hot conditions.
one sign of a failing capacitor is higher current draw and overheating of breakers.


 

Gary RV_Wizard

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Circuit breakers are basically just heat sensitive switches - high current makes them ht and they trip. So, it could be higher current or it could simply be that the panel is getting unusually warm at 100+ temperatures.  I've even seen a few breakers that held ok if the panel cover was open or removed, but tripped when all bundled up.

Chances are, though, that the a/c are simply old and tired, coupled with the accumulated dirt and old "run capacitor" that others have mentioned.
 

cerd

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I tried to search, but didn't get much. Assuming the Coleman 6779B is a rooftop unit, are you running it on high or low? I can run my AC all day on low drawing about 15A. I can actually power it from a normal outlet in my garage, only occasionally tripping a breaker.

However, on our last trip, we set the AC to High because it was hot out and we wanted the camper to cool off quickly. On a 30A breaker, it continuously was tripping. We switched it back to low, and didn't have a problem all weekend and it still kept the camper nice and cool even in 100F weather, also directly in the sun.
 

beaverfever

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have you checked the voltage? if you are in a rv park the voltage is probably dropping as it heats up and everybody returns and turns on their a/c units.
low voltage =high amps that will over heat the internal thermal overloads causing them to trip.
 

cerd

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Gary RV_Wizard said:
High or Low only affects fan speed.  Don't see how it can alter the amp draw very much. Perhaps +1A?

That's what I thought too, but apparently that's not the case. It affected how hard the compressor ran too. It was kicking in harder (maybe under higher pressure?) making the circuit breaker trip. I'd put a clamp meter on it, but I only have 15A circuits available for use at my house.
 

kdbgoat

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The fan speed affects the airflow across the coils, which may also affect the head pressure.
 

_Rusty_

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solarman said:
....run capacitors dry out over a period of time, ....

Dumb Question from a plant electrician... what's a "Run Capacitor"? ???

I deal with "start" capacitors all the time, (but not air conditioners).  When the motor is energized the cap shifts the phase to give more torque for starting, then when the motor is up to speed a centrifugal switch throws and bypasses the capacitor applying in-phase voltage to the windings. If the capacitor is bad the motor starts reaaalll slow.  If that switch fails to operate the motor draws more current and doesn't run at full speed. Also, can the motor be a dual speed motor? There may be separate windings for each speed but still needs the starting torque to get the compressor to run.

Is there something I need to learn about air conditioning circuits?
 

kdbgoat

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Here's a quick lesson.
https://beckettcorp.com/support/tech-bulletins/an-introduction-to-psc-motors/
 

John From Detroit

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There are two fans. Inside and out.

Now we think of the inside fan cause we hear it all the time but we tend to forget the OUTSIDE fan. That's the fan that does the cooling of the evaporator coils.

As the fan slows. the heat builds, the pressure builds, and the amps drawn build.

So yes it makes a difference.
 

_Rusty_

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kdbgoat said:
Here's a quick lesson.
https://beckettcorp.com/support/tech-bulletins/an-introduction-to-psc-motors/

Thanks!  I don't believe we have had anything this small here to have ever come across one.  Overall a PSC motor looks like the thing to use in an AC unit.
 

John From Detroit

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Either one will work in an A/C.. I've used split phase for fans. And water pumps.

But now I understand the PSC motor as well (The diagrams spoke volumes to me) and this helps me to unmderstand. IF they are using PSC motors. It helps me umnderstand why I am having issues.

SO thanks.  Big time Thanks.
 

gaoneal02

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Sorry, I was expecting some sort of an alert that someone had responded to my question. So, I did pull the covers off both rooftop units to inspect them. Very clean and no rust or rot of any kind. But, I did figure out how to fix them, I am going to sell the motor-home and buy a larger more updated 5th wheel. I did try an additional cover for one unit so the sun was indirect, but had absolutely no effect. I even had a mobile rv repair company come and they didn't even want to work on them. These units are from 1988 and have no history on them beyond Nov 2017
 

John From Detroit

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I like your cure :)

Some years ago I met a couple of women (Mother/Daughter team) who had no hot water. Well based on information here I was able to help 'em get back, into hot water by doing a TEMPORARY fix (Gutting the check valve on the hot outlet on the heater)  They did a better fix a year later though.

Same one you are doing :)
 

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