Roof AC high current

[amphi_sc]

One of my original 2006 Penguin heat pumps is starting to draw high current >20 amps after running for a while.  It starts up and heats or cools fine, but the current creeps up after a while.  Other than replacing it due to age (which I may do anyway), what to check?  Today, for example, all three units were working hard cooling on this hot day and after running almost continuously for an hour or two, it was drawing 22 amps and tripped the breaker.  The other two were drawing about 15 Amps each.

Thanks,

Al

[Stinger]

1 hour ago, amphi_sc said:

One of my original 2006 Penguin heat pumps is starting to draw high current >20 amps after running for a while.  It starts up and heats or cools fine, but the current creeps up after a while.  Other than replacing it due to age (which I may do anyway), what to check?  Today, for example, all three units were working hard cooling on this hot day and after running almost continuously for an hour or two, it was drawing 22 amps and tripped the breaker.  The other two were drawing about 15 Amps each.

Thanks,

Al

Some things come to mind - your other two units amperage draw are just about spot on for a 13,500 or 15,000 BTU unit.  The higher draw of the third unit could be caused by a couple things to check out.  

First:  locate the circuit breaker for that unit and make certain the wire connections are solid on the breaker itself.  OF COURSE CUT THE POWER TO THE PANEL FIRST!  A loose wire connection will create high resistance and therefore higher heat!  Over time it will burn out or melt - ask me how I Know!!

Second:  I would suspect the fan blower motor itself.  Some have start AND run capacitors on them.  Check / and or replace them first - least costly.  Then check all connections to that fan blower motor for being secure and not loose.  Carefully pinch the wire spade connectors on those capacitors after discharging them and killing power to the unit first.  Same thing can happen to them - especially if they are original installations!  

Lastly:  I might suspect the compressor draw.  IF you have an ammeter (clamp-on type) you can check the current (amp) draw of that compressor and compare with the other two compressors.  Should be close to the same.  If there is a large delta there, suspect the compressor.  Let us know what finally fixed the issue!

One more thing, you weren't running ALL THREE A/C units simultaneously were you?  That would just about cause an overload with nothing else turned on!  Over a few hours the average draw could exceed the 80% limit of some breakers.  

[amphi_sc]

Stinger, I already replaced the start and run caps as that was my first thought.  No separate caps that I see for the fan motor.  The run cap is a dual.  Also replaced the 20 amp (Square D) breaker in the sub panel just in case. 

Good thought about the clamp on meter.  I'll climb up in a day or two.  Probably compressor is getting old and heats up causing higher resistance and thus current draw as the day wears on...  Fan motor seems to spin freely.

By the way, three ACs are pretty standard on the big rigs and everything is sized and balanced across both legs appropriately.  At 45 feet like being space in a 100 degree day, two ACs couldn't begin to keep up so 3 units are standard.  Aqua hot and one AC on one leg, the two other ACs on the other leg.  In theory with all running would have 15 Amps to spare on each leg. (They all have individual 20 amp breakers in the sub panel....).  Also, voltage when all 3 are running is staying around 120-123 volts on either leg so no low voltage problem...on park power or the 10kw generator...no change.

 

Thanks

Al

[Harvey Babb]

While you are checking things, take a look at the temperature at the outlet of the condenser coil. If it isn't getting rid of as much heat as it should the temperature and pressure will rise, overloading the compressor.  If it is much higher than the other units then look for obstructed condenser air flow or possibly deterioration of the coil and fins.

For verification, run water over the condenser and see if the amps come back where they should be.

 

 

[Hypoxia]

If the fan runs even slightly  slow due to bearings etc. the pressures in the compressor will slowly  rise and so will the amps.  I spin them by hand to see if they coast or stop.

Harvy is right about running water on the condenser.

 

Edited July 16, 2020 by Hypoxia

[jacwjames]

Back in ~2015 I had the same symptoms with the front AC unit occasionally kicking the breaker.  I also replaced the start capacitor with no difference.    I then checked the blower motor itself, I could hardly turn it by hand, the bearings were on the verge of failure.  I also noticed that the squirrel cage fan blade was slightly hitting the sheet metal.   I bought a replacement blower motor for ~$120.  The motor came with new rubber mounting bushings.   When I removed the old motor I found the rubber bushings were pretty much gone.  The new motor with the new rubber bushings solved the problem.  The AC was much quieter and pulled less amps.  

[Chuck B 2004 Windsor]

At least twice a year you need to go up on the roof, remove the shroud, and clean the inside of the unit with water.  Dust and dirt can do wonders to shorten the life of the unit.  Check the fan to see if it turns smoothly or binds.  Keeping the unit clean and the fan running smoothly will extend the life of the unit. 

[Hotrod - R.I.P.]

Make sure the coils are clean and the weather stripping under the cover has not come loose. Low voltage and a hot day will get you up to 20a on a 15k unit.

[amphi_sc]

As a closing follow up ...

Recall that the problem unit was the front A/C heat pump ( 15k unit ).  As everyone knows, a lot of heat comes in the windshield even with shades and coverings.  After swapping pieces with the identical center unit (leaving bedroom unit untouched) essentially I now have a front unit that does not trip the breaker after running continuously for hours and hours, and the center unit also functions, but evidently as the heat load is less on that unit, it will cycle off and on giving it a rest which I guess gives it the chance to "cool off" the compressor ... which it never had the opportunity as the front unit.  So today again 100+ outside, full sun, and a West-NW facing parking location with hot windshield sun, all three units did not trip any internal breakers, but current draw was getting up there running close to 18-19 amps identically on the 3 units when they are in the worst heat of the day. They all start off about 14 amps as it starts to get warm from the cool night. My Hughes Auto former was in the circuit this time but in pass through mode, so was only getting the minimal 2% boost as unboosted voltage is rock solid at 120V. A few weeks ago I was here essentially under the same conditions with rock solid unboosted 120V, and the "original" front unit configuration would trip after running continuously for 2-3 hours. I don't think the booster is really a factor...I've just been too lazy to unplug it (internally mounted) as in a week I'll be at a campground well known for low voltage, but at least more shade and only in the low 90's.

Anyway, just fyi

[Bob Nodine]

7 hours ago, amphi_sc said:

As a closing follow up ...

Recall that the problem unit was the front A/C heat pump ( 15k unit ).  As everyone knows, a lot of heat comes in the windshield even with shades and coverings.  After swapping pieces with the identical center unit (leaving bedroom unit untouched) essentially I now have a front unit that does not trip the breaker after running continuously for hours and hours, and the center unit also functions, but evidently as the heat load is less on that unit, it will cycle off and on giving it a rest which I guess gives it the chance to "cool off" the compressor ... which it never had the opportunity as the front unit.  So today again 100+ outside, full sun, and a West-NW facing parking location with hot windshield sun, all three units did not trip any internal breakers, but current draw was getting up there running close to 18-19 amps identically on the 3 units when they are in the worst heat of the day. They all start off about 14 amps as it starts to get warm from the cool night. My Hughes Auto former was in the circuit this time but in pass through mode, so was only getting the minimal 2% boost as unboosted voltage is rock solid at 120V. A few weeks ago I was here essentially under the same conditions with rock solid unboosted 120V, and the "original" front unit configuration would trip after running continuously for 2-3 hours. I don't think the booster is really a factor...I've just been too lazy to unplug it (internally mounted) as in a week I'll be at a campground well known for low voltage, but at least more shade and only in the low 90's.

Anyway, just fyi

Sounds like the middle unit has more head pressure than the other two units. Could be a dirty or partially blocked condenser. Did you remove the cover and spray down the condenser with a cleaning solution and hose it off while you had the unit out?

 

[96 EVO]

Ok, I know I'm way, way late to this thread, but believe it or not, I've been waiting for about 2yrs for the only local distributor of foaming evaporator / condenser cleaner, to get some in store! Amazon Canada..... forget it, they charge about $30 a tin. I have 3 heat pumps.

My amps were creeping up on all 3 of my units, usually settling in about 18 amps per unit after an hour or so of run time.

Gave all three a good cleaning today. Did each evaporator coil twice, with a rinse in between. Condenser coil got one cleaning.

All three (2007 Duo-therms), will now run for hours drawing a steady 12-13amps. Getting 25 to 27deg difference between inlet and outlet temperature 👍!

These members that have suggested cleaning your coils first, are bang on!!