Special dental air compressor: contactor clicking

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Old 09-09-19, 08:48 PM
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Special dental air compressor: contactor clicking

Hi,

Not sure if this is the right forum, but google search led me here. I own a dental office and have a compressor unit. It started making weird noise. It still works, It's an airtechinque airstar 30 unit with 2 motor heads.

It's been making knocking or clicking sounds, and I ruled out motor units. It happens that the contactor has been making loud noises. I realize a lot of AC units have contactors and compressors and maybe you guys can help me. Contactor clicks and the unit turns on. But in few cycles, it starts clicking and continues on, and clicking gets worse and shuts off. It runs again after it drops below 60psi and tries to raise up to 100psi but sometimes clicks and clicks and never reaches 100psi. I am not sure what to do. I disassembled contactor and cleaned it up with no success. It works sometimes and sometimes show this symptom. I am guessing it may be because of capacitor? I have 2 capacitor units attached to the contactor.

It's also got humidistat and regeneration valve which I am not sure are related to this symptom. Any ideas?

Thanks.
 

Last edited by loglog84; 09-09-19 at 09:04 PM.
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Old 09-09-19, 11:17 PM
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Welcome to the forums.

Thread moved. Title changed

It took me a little while to figure out what you have. You have a dual air compressor with dryer for dental work. It may use a contactor but it is nothing like an A/C system.

You have a dual motor unit.
Are there two contactors or do both compressors come on at the same time ?
That contactor gets its signal from a pressure switch that monitors the pressure. That would be the part I would suspect as having a problem.

I see several units at the company website. Do you have the model number ?
Do you have the wiring diagram for the unit ?
 
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Old 09-10-19, 04:39 AM
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Hi, you really canít clean the points on a contactor, best to replace it if it has been chattering a lot.
Geo
 
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Old 09-10-19, 07:00 AM
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Thanks for reply. That's the right word. Chattering!

It's air techniques Airstar 30 unit.

There is only one contactor.
I got 2 27.5uF 370v run capacitors, i measured capacitance, one is measured at 24.5uF and another at 23.7uF. Can this be a problem? Maybe capacitors don't hold charge?

Can that be related to low voltage to contactor?

- checked voltage while machine is running and chattering happening, rated at 250v, its pulling 243v, but at the same time it's the same when the chattering is not happening. maybe just bad contactor?

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Last edited by PJmax; 09-10-19 at 12:16 PM. Reason: resized/labeled diagram
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Old 09-10-19, 12:15 PM
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I circled the pressure switch. That is your problem. That is the ONLY device that closes the circuit for the contactor. You can locate it and temporarily bypass it. The contactor should close and run normally.

Depending on where that pressure switch is.... it may be blocked with water or it could just be bad.
 
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Old 09-12-19, 01:58 PM
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thx! that was the problem!
 
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