Help with older Champion Duplex compressor only 1 running

[Krician]

Hello, my shop moved and we are lucky to have a compressor included in the new shop. I cannot find the model number of the unit but doing some research it looks like a older Champion Duplex model. My issue is only 1 pump runs. The tank is drained every night and every morning I start both pumps up again. After the morning run, throughout the day only 1 runs. We replaced the pressure switch on both pumps and now it's doing the same thing- only its the opposite pump now. Defective pressure switch? We even lowered the non running pumps kick on pressure and still it won't go. My guess is the other pump kicks on too soon before the non running one so the pressure cannot reach the kick on pressure.. here are pics

 

[930dreamer]

This set up uses an alternator to switch between compressors on/off.

 

[Krician]

This set up uses an alternator to switch between compressors on/off.

Really? Can you please guide me on where it is located? I monitored the compressor and only the right side runs...

 

[redmondjp]

Somewhere inside the control box is an alternator relay that is bi-stable - it latches in one of two positions. Every time power is applied to it, it switches to the other position. The switch contacts in this relay should be wired in series with the contactors for each pump motor.

You should be able to get a wiring diagram from Champion.

 

[txvwnut]

Only one pump will under normal conditions, only when there is a high demand for air will both pumps run at the same time. It sounds like the flip-flop switch is doing it’s job since you say both comps run when the tank is empty then it switches to one or the other after it has filled.

 

[930dreamer]

Did you get it figured out?

 

[Krician]

So its normal for only the right pump to be used throughout the day, and the left pump only when the tank is empty?

 

[redmondjp]

So its normal for only the right pump to be used throughout the day, and the left pump only when the tank is empty?

Does only the left pump come on when the tank is empty, or both pumps simultaneously?

 

[bsaint]

Its suppose to alternate. It seems like its the alternating relay thats the culprit. The low demand switch seems to be working.

 

[redmondjp]

If it were my machine, I'd do away with the alternator relay altogether and just use a separate pressure switch for each pump, with 10 psi or so differential between the 'on' settings. This way, both pumps would run simultaneously (assuming sufficient electrical capacity to the machine is there) to fill up the tank from zero faster, and then only one pump would cycle for a low-demand load. But if the demand exceeded what one pump could produce, the pressure would drop and the second pump would come on.

If you put hourmeters on each unit, you can manually switch their controls to even out the hours on each pump as one sees fit.

 

[Alexander]

If you put hourmeters on each unit, you can manually switch their controls to even out the hours on each pump as one sees fit.

My understanding is that this machine, when functioning properly, does exactly what you're describing - automatically.

It should alternate pumps each time it cycles under normal small loads, and switch on both during periods of high demand.

Then again, maybe I'm not understanding correctly.

The problem here seems to be that it's not correctly switching between units each time it cycles.

 

[bsaint]

Yea it should do it automatically. But it has two starters. You need to confirm its trying to pull in the second starter or not. There should be a schematic somewhere.

 

[engineer2]

I agree it's likely an alternating relay issue. Since both can run at start-up, it'll be a cross-wired type of alternating realy, if that's how they do it.
Quick search online line shows little about what type of alternating relay Champion uses.
Since the lead pump usually starts first, it's hours will tend to be higher.

 

[Krician]

Sorry for the late reply guys, I've been busy. So I opened up the alternating relay box and watched the contacts while the pressure was released to kick on- it only went to the right compressor all the time, never the left. I like the idea of having both kick on at the same time instead of alternating- can I eliminate the relay?

 

[6PTsocket]

Sorry for the late reply guys, I've been busy. So I opened up the alternating relay box and watched the contacts while the pressure was released to kick on- it only went to the right compressor all the time, never the left. I like the idea of having both kick on at the same time instead of alternating- can I eliminate the relay?

It appears that it is wired to over ride the alternating relay when demand is high and run both pumps Why would you want to modify this design instead of just repairing it? What it is supposed to do seems to be the optimum setup. Is there a second relay to start both pumps together when pressure has dropped low enough?

Sent from my SM-G900V using Tapatalk

 

[engineer2]

Can you post a pic of their realy setup?