[whited44]

Here is the report

I have 2 Scs ac units. 1 large one that uses 2 breakers, and one small one that uses 1 breaker.

The small one works fine and is pulling 15 amps at the breaker in the box.  Since this one works fine I’m going to quit talking about it.

My problem was the large one blowing breaker 1 in the breaker box after running for about 20 minutes.  This unit pulls 15 amps on breaker one and 4 amps on the second breaker in the “high fan” cool mode.  If the fan is on low it pulls no amps on breaker 2 and 15 amps on breaker 1.

Last night during the testing it worked fine.  I could not amp clamp at the ac unit itself because the wires were too short so I did all my testing at the breaker box.  I did disconnect and reconnect the compressor plugs and made sure they weren’t burnt.  It ran all night and seems to be ok so far today. 

End report

[Richard]

Super, thanks for taking the time to straighten out my understanding.

Two things can be discerned from your data. One, the second compressor in your large unit is NOT coming on. Two, the circuit board has some weird logic. In low cool, compressor 1, the inside and the outside fan ALL RUN off the same leg. But in high cool, compressor 1 runs and the internal fan run off leg 1, while compressor 2 and the outside fan run off leg 2. SCS did that I suppose to balance the loads as much as possible. I may have the fans reversed, but I am sure one of the fans moves to the second leg on high.

The question is to determine why comp 2 is not running.

Which breaker is tripping? 1 or 2, or both? Edit, reread your summary, breaker 1.
What size are the breakers? If 15, then we know why they are tripping Edit, I just saw the pics, they are 20 amp.


The 15 amps while running is about right given the heat we are experiencing. But you might want to continue to monitor the amp draw on that breaker as the day heats up. Higher outside temps mean higher head pressures on the compressor leading to higher amp draw

One last thing, can you remove the filters under the steps and look at the inside of the units. I know a fellow who was tripping breakers only to discover dust bunnies and a couple of coffee filters plastered on the inside evap fins.

[Richard]

This pic demos what Jeff is talking about. You can see the alternating pattern where the legs would power the circuit breakers. 

https://www.google.com/search?q=picture+...AIYASACKAE

[whited44]

Super, thanks for taking the time to straighten out my understanding.

Two things can be discerned from your data. One, the second compressor in your large unit is NOT coming on. Two, the circuit board has some weird logic. In low cool, compressor 1, the inside and the outside fan ALL RUN off the same leg. But in high cool, compressor 1 runs and the internal fan run off leg 1, while compressor 2 and the outside fan run off leg 2. SCS did that I suppose to balance the loads as much as possible. I may have the fans reversed, but I am sure one of the fans moves to the second leg on high.

The question is to determine why comp 2 is not running.

Which breaker is tripping? 1 or 2, or both? Edit, reread your summary, breaker 1.
What size are the breakers? If 15, then we know why they are tripping Edit, I just saw the pics, they are 20 amp.


The 15 amps while running is about right given the heat we are experiencing. But you might want to continue to monitor the amp draw on that breaker as the day heats up. Higher outside temps mean higher head pressures on the compressor leading to higher amp draw

One last thing, can you remove the filters under the steps and look at the inside of the units. I know a fellow who was tripping breakers only to discover dust bunnies and a couple of coffee filters plastered on the inside evap fins.

So what would cause compressor 2 not to run??  Bad capacitor??  Bad compressor??  

Is the only way to access them take the entire unit out??  

I did look under the steps and there are nothing sucked against the fins

[Richard]

What would cause comp 2 not to run:
Signal from tstat not present on board
Power from board to comp is compromised
Compressor is burned up
Run cap is kaput

A lot of this can be tested at the circuit board without removing the whole unit.

[whited44]

So this was just at Newell for my roof repair..

Anyway they “diagnosed” the ac unit as needing a new control board (they warrantied it which was nice). Cleaned the coals and fixed a shorted fan motor wire. Said it was good to go.

When I picked it up it was doing the same thing as before I dropped it off. I had to leave to get back for work. So I couldn’t stay.

This morning I had some time with the meter. My diagnosis is.. on low cool, unit starts like normal, compressor kicks on. Amp draw around 10 at the breaker in the box. Unit runs for about 20 minutes and one of the fans you can hear outside starts to slow down and quits.. I run inside, it’s still blowing thru the vents so the other fan must still be running. But amp draw continues to increase until breaker 1 trips.

I think the fan motor is the culprit, loose wire, tired fan. Is there anything I should check before taking the unit out and replacing both fan motors??

[[email protected]]

So this was just at Newell for my roof repair..

Anyway they “diagnosed” the ac unit as needing a new control board (they warrantied it which was nice).  Cleaned the coals and fixed a shorted fan motor wire.  Said it was good to go.

When I picked it up it was doing the same thing as before I dropped it off.  I had to leave to get back for work.  So I couldn’t stay.

This morning I had some time with the meter. My diagnosis is..  on low cool, unit starts like normal, compressor kicks on. Amp draw around 10 at the breaker in the box.  Unit runs for about 20 minutes and one of the fans you can hear outside starts to slow down and quits..  I run inside, it’s still blowing thru the vents so the other fan must still be running. But amp draw continues to increase until breaker 1 trips.

I think the fan motor is the culprit, loose wire, tired fan.  Is there anything I should check before taking the unit out and replacing both fan motors??

I would expect there is a capacitor for that fan motor. I would check that if it has one. But it sounds like a dying motor. Could be just bearings going out in it but not usually worth fixing that yourself on a 20 year old motor.

BTW please give us an update on the roof repair!

[whited44]

So this was just at Newell for my roof repair..

Anyway they “diagnosed” the ac unit as needing a new control board (they warrantied it which was nice).  Cleaned the coals and fixed a shorted fan motor wire.  Said it was good to go.

When I picked it up it was doing the same thing as before I dropped it off.  I had to leave to get back for work.  So I couldn’t stay.

This morning I had some time with the meter. My diagnosis is..  on low cool, unit starts like normal, compressor kicks on. Amp draw around 10 at the breaker in the box.  Unit runs for about 20 minutes and one of the fans you can hear outside starts to slow down and quits..  I run inside, it’s still blowing thru the vents so the other fan must still be running. But amp draw continues to increase until breaker 1 trips.

I think the fan motor is the culprit, loose wire, tired fan.  Is there anything I should check before taking the unit out and replacing both fan motors??

I would expect there is a capacitor for that fan motor. I would check that if it has one. But it sounds like a dying motor. Could be just bearings going out in it but not usually worth fixing that yourself on a 20 year old motor.

BTW please give us an update on the roof repair!

Ahh yes capacitor!!  I think I have one from my other unit.  Seems like the only way to get to that is remove the unit tho right??

[johnkosir]

My experience as a retired hvac contractor is that run capacitors (fan motors do not have start caps) will stop the motor from starting,(they throw the start windings out of phase witch makes the motor start, if you spin the motor by hand and it starts you have a bad cap) if the bushing are worn the motor will start slowly, draw more current and the thermal overload in the motor will open ,stopping the motor, the head pressure will go up and cause the compressor to work harder, draw more current and trip breaker,

[[email protected]]

So this was just at Newell for my roof repair..

Anyway they “diagnosed” the ac unit as needing a new control board (they warrantied it which was nice).  Cleaned the coals and fixed a shorted fan motor wire.  Said it was good to go.

When I picked it up it was doing the same thing as before I dropped it off.  I had to leave to get back for work.  So I couldn’t stay.

This morning I had some time with the meter. My diagnosis is..  on low cool, unit starts like normal, compressor kicks on. Amp draw around 10 at the breaker in the box.  Unit runs for about 20 minutes and one of the fans you can hear outside starts to slow down and quits..  I run inside, it’s still blowing thru the vents so the other fan must still be running. But amp draw continues to increase until breaker 1 trips.

I think the fan motor is the culprit, loose wire, tired fan.  Is there anything I should check before taking the unit out and replacing both fan motors??

I would expect there is a capacitor for that fan motor. I would check that if it has one. But it sounds like a dying motor. Could be just bearings going out in it but not usually worth fixing that yourself on a 20 year old motor.

BTW please give us an update on the roof repair!

Ahh yes capacitor!!  I think I have one from my other unit.  Seems like the only way to get to that is remove the unit tho right??

I think there are some capacitors in the electrical compartment behind the control board. Cannot remember if there are more inside, does seem like I remember seeing some on the motors? Its been a while.