2 Compressors feed from an ATS?

[amge]

Is there a way to put an ATS for 2- 100hp air compressors or is there a control panel that I just cant seem to find. The customer wants a redundant compressor and does not have the power available for a new circuit.

 

[augie47]

There are controllers designed to operate compressors in an alternate sequence.
I will see if I can locate one. You might also look at "pump controllers" as it is commonplace there also.

link added:
http://www.time-mark.com/Documents/Brochures/Alternating Relays Brochure.pdf

 

[Jraef]

There are controllers designed to operate compressors in an alternate sequence.
I will see if I can locate one. You might also look at "pump controllers" as it is commonplace there also.

link added:
http://www.time-mark.com/Documents/Brochures/Alternating Relays Brochure.pdf

It's called a "Duplex" starter panel, all of the major suppliers have them available. It is two motor starters in one box, with an "alternator" relay similar to what Augie47 showed which is wired so that each time a compressor is called for, it picks the other one that was not used the previous time. Those also typically have a feature that turns on the other one if the first one trips, and then an option to turn on the second one if the first once can't handle the demand. In your case, because his service is insufficient, you would want to opt OUT of that last feature.

 

[amge]

Thanks, the compressors are 2 separate units with there own controllers

 

[amge]

I wonder if I could put an interlocking relay off of the existing controllers to lock out one pump at a time and switch with a pump failure.

 

[kwired]

I wonder if I could put an interlocking relay off of the existing controllers to lock out one pump at a time and switch with a pump failure.

I would design my own alternating control for this for that reason. A single panel with both controllers in it means you possibly need to work on one while the other one in same enclosure is live, and you already have separate controls in the first place, just convert each to a hand/off/auto setup with auto running through the alternating control.

 

[Jraef]

Thanks, the compressors are 2 separate units with there own controllers

I wonder if I could put an interlocking relay off of the existing controllers to lock out one pump at a time and switch with a pump failure.

I would design my own alternating control for this for that reason. A single panel with both controllers in it means you possibly need to work on one while the other one in same enclosure is live, and you already have separate controls in the first place, just convert each to a hand/off/auto setup with auto running through the alternating control.

Yes, per kwired's suggestion you certainly can do this, if you have the control circuit design skills to get it right. It's not hard for those of us who do this sort of thing often, I only say it that way because I know that getting a license does not mean you have expertise, or even exposure, to control circuit design work.

So one thing you will want to do is to have the pressure switches no longer control each starter directly, have just one pressure switch, and have it energize the alternator relay. Then have the control power go through the alternator relay to control the individual starters. To avoid down time, have a N.O. trip contact of each of the starter OL relays wired in parallel with the alternator contacts, so if either one trips off line, the alternator status is overridden and it just runs one compressor. If it were me, I would run those trip contacts to little relays, then use the relay contacts in the parallel circuit, but have another relay contact on each one turn on a "Failure" light so that you know one of the compressors is down and they have no backup.

Simpler "Manuel" control option: get a 200A double throw safety switch ahead of the two compressors and if one goes down, send Manuel over to pull the switch handle and change over to the other one. No evening out of wear and tear, no automatic operation if one fails, but simple to implement.

 

[kwired]

Yes, per kwired's suggestion you certainly can do this, if you have the control circuit design skills to get it right. It's not hard for those of us who do this sort of thing often, I only say it that way because I know that getting a license does not mean you have expertise, or even exposure, to control circuit design work.

So one thing you will want to do is to have the pressure switches no longer control each starter directly, have just one pressure switch, and have it energize the alternator relay. Then have the control power go through the alternator relay to control the individual starters. To avoid down time, have a N.O. trip contact of each of the starter OL relays wired in parallel with the alternator contacts, so if either one trips off line, the alternator status is overridden and it just runs one compressor. If it were me, I would run those trip contacts to little relays, then use the relay contacts in the parallel circuit, but have another relay contact on each one turn on a "Failure" light so that you know one of the compressors is down and they have no backup.

Simpler "Manuel" control option: get a 200A double throw safety switch ahead of the two compressors and if one goes down, send Manuel over to pull the switch handle and change over to the other one. No evening out of wear and tear, no automatic operation if one fails, but simple to implement.

Or even have a second pressure switch set at a different level to kick on second compressor regardless of the status of the first compressor. That is common with lift stations - first level switch kicks on an alternating pump each cycle. If level reaches a second switch for any reason, it is set up to start both pumps. If one is not running for some reason it is often only noticed if you pay attention to the run time hour meters. If they advance at about same rate they are likely alternating. If one runs a lot more then the other - something is wrong, maybe elecrical, maybe mechanical.

 

[Cow]

Or even have a second pressure switch set at a different level to kick on second compressor regardless of the status of the first compressor. That is common with lift stations - first level switch kicks on an alternating pump each cycle. If level reaches a second switch for any reason, it is set up to start both pumps. If one is not running for some reason it is often only noticed if you pay attention to the run time hour meters. If they advance at about same rate they are likely alternating. If one runs a lot more then the other - something is wrong, maybe elecrical, maybe mechanical.

He only has one circuit available for a single compressor setup, otherwise this would be the way to go.

 

[kwired]

He only has one circuit available for a single compressor setup, otherwise this would be the way to go.

You are correct, I did read that earlier but forgot about it already. Still could alternate and possibly set up to attempt to start the second unit if the first fails for some reason.

 

[iceworm]

All good advice.

Only thing I would add is to not alternate. If you do, you end up with two worn out compressors - both needing rebuild at the same time.

Instead, run one in lead, second in backup. When the first wears out, run the second in lead while rebuilding the first.

ice