Basement air 2nd compressor

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IslandGuy

IslandGuy

Well-known member
Joined
Oct 4, 2009
Posts
468
Location
Saddlebrooke, AZ
Been checking my basement AC and am not sure if the 2nd compressor is running...when I turn on the AC the 1st compressor starts up and peaks at about 26 amps and settles down to around 12 or 13 amps...after a minute or so the outdoor fan shuts off and then the second compressor should fire up...again the amps peak at about 26 or so and then settles down to 18 or 19...the outdoor fan continues to run...if I turn off the breaker to the second compressor the amps drop back to 12 or 13....I believe with both compressors running I should see about 23 amps or so...at least that is the spec from Coleman Mach.
I am getting about 20 degrees difference between the input and output at the AC registers....maybe just chasing my tail
I am checking the amps reading while running the generator...
I made a video of the ckt board....green led flashes 4x's and the red led is solid...according to the attached wiring document I believe this is normal...
any thoughts?

Thanks!
 

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I think you're in the ballpark of proper operation, temperature differential should be >=20 degrees. The operational sequence of the compressors and fan seems normal to me. As far as the current draw with both compressors running, you are just a bit on the low side but your current readout might not be accurate. Get a clamp-on ammeter (they are inexpensive if you don't have one) and check each leg. You can clamp-on at the breaker panel if you have room (BE CAREFUL!) or at the basement unit itself.

A very common cause of poor cooling is the ductwork in the rear cap is leaking air. If you have a non-contact thermometer, scan the rear cap for cool spots, or feel with your hands. Clean your evaporator and condenser coils, the condenser coil is the one on the outside. You can buy special purpose spray cleaner or use Simple Green (the one that's aluminum safe.)

You should consider replacing the compressor start and run capacitors, even if yours are okay it would be useful preventive maintenance.
 
Sounds about right to me, about the same amp readings and sequence I get
 
John Canfield said:
I think you're in the ballpark of proper operation, temperature differential should be >=20 degrees. The operational sequence of the compressors and fan seems normal to me. As far as the current draw with both compressors running, you are just a bit on the low side but your current readout might not be accurate. Get a clamp-on ammeter (they are inexpensive if you don't have one) and check each leg. You can clamp-on at the breaker panel if you have room (BE CAREFUL!) or at the basement unit itself.

A very common cause of poor cooling is the ductwork in the rear cap is leaking air. If you have a non-contact thermometer, scan the rear cap for cool spots, or feel with your hands. Clean your evaporator and condenser coils, the condenser coil is the one on the outside. You can buy special purpose spray cleaner or use Simple Green (the one that's aluminum safe.)

You should consider replacing the compressor start and run capacitors, even if yours are okay it would be useful preventive maintenance.
Click to expand...

Thanks John...I did check the amps with and they are reading out about the same as the panel....I definitely have to do some housekeeping on where the duct elbow connects...can feel cool air blowing there and someone had taped it before...just did a poor job.
 
Have spoken to two different techs about the low amperage on the 2nd compressor...one was Leon Herschberger from National RV refrigeration and the other was Mike from Gene's RV AC repair up in Phoenix. They both believe the reason for the low amps is due to low freon...so there may be a small/slow leak in the 2nd compressor...going up to Phoenix in a few weeks to get it checked out...of course they need to pull out the unit...this won't be cheap...

 
low amperage draw can also be a result of a low load. As load increases and condenser temps rise so does head pressure, resulting in higher amperage. The same thing happens in reverse as conditioned air space is brought to temperature or condenser temp drops.

Like islandguy said it can also be a result of low charge or a compressor getting worn out. Not sure about the wiring on your unit but I can change mine out so that 1 is 2 and 2 is 1, that would help you to see if they are pulling the same. I do that occasionally so both compressors wear the same (more or less)
 
IslandGuy said:
... They both believe the reason for the low amps is due to low freon...so there may be a small/slow leak in the 2nd compressor..
Click to expand...
They'll have to install service fittings, I suppose they have a way to capture the Freon when they open up the system.

catblaster said:
low amperage draw can also be a result of a low load. As load increases and condenser temps rise so does head pressure, resulting in higher amperage. ...
Click to expand...
That certainly makes sense. I have a smart well pump controller that monitors the pump run current, when the current decreases the pump shuts off because it isn't under load (low GPM well.)
 
John Canfield said:
They'll have to install service fittings, I suppose they have a way to capture the Freon when they open up the system.
Click to expand...

They can use a line piercing valve, just clamp it around the line and it pierces the pipe. If it is truly low on refrigerant then it has to be going somewhere. Some will put the gages on and see a low suction pressure and think there is a leak but instead it is a stopped up evaporator or clogged fan limiting the airflow. Then they throw more refrigerant in which does nothing but flood the system and on several I have seen the liquid comes back on the suction side to the compressor and takes it out. boom!

It's hard to find good help sometimes...
 
catblaster said:
They can use a line piercing valve, just clamp it around the line and it pierces the pipe. If it is truly low on refrigerant then it has to be going somewhere. Some will put the gages on and see a low suction pressure and think there is a leak but instead it is a stopped up evaporator or clogged fan limiting the airflow. Then they throw more refrigerant in which does nothing but flood the system and on several I have seen the liquid comes back on the suction side to the compressor and takes it out. boom!

It's hard to find good help sometimes...
Click to expand...

I spoke to a few techs and they say that piercing the line is a sure way for a future leak...they both braze in new fittings...with that in mind when I get mine looked at I am going to make sure they don't use a piercing valve.
 
IslandGuy said:
I spoke to a few techs and they say that piercing the line is a sure way for a future leak...they both braze in new fittings...with that in mind when I get mine looked at I am going to make sure they don't use a piercing valve.
Click to expand...

That's true about the possibility of an eventual leak but thats a way of evacuating the system so you dont dump the "freon" into the atmosphere. then braze on the charging ports
 
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