HVAC Contactor w/ Shunt

[Timd32]

I have a Carrier unit about 7yr old the contactor is shorted.

The board actually has a pretty cool diagnostic code flashing deal, sure enough its right on the money.

So anyone know why the contactor controls one contact and then is a shunt on the other side, so it's basically just jumpered thru internally. My guess is for distribution only cheaper to use this then mount another TB @ 40A.

But is there any technical reason for this or in a bind can I make a single work for the weekend.

I would just leave the one in place with the shunt and possibly add a temp contactor till I can get the correct part.

Its never a price deal, seems most places are closed tomorrow and I have to start work at 5AM tomorrow till who knows when doubt I will make it to a place to get one.

I ordered something close today for Monday, not the exact deal. Will pick a place online to grab the correct part.

It's fused shut I tried to pop it loose, welded pretty good. We had a utility failure 2 days ago my guess is during my Generator run or the sag event something was undervoltage for a bit or chattered. Doubt its coincidence usually the unit is off for generator runs I forgot and left it on and it tried to run and my wife said the lights started flickering pretty bad.

Guess I should clean this out more often, out of sight out of mind.

 

[dieselshadow]

Single pole contactor is cheaper than a two pole. Simple economics my friend. I wouldn’t hesitate to install either a single or double pole contactor.

 

[brucejohnson]

Here is a small statement I found that makes safety/protection sense, just like the situation you experienced:

Why do we have a shunt trip breaker or Isolation contactor in the enclosed Altistart Softstarts (ATS23, ATS46, ATS48, ATS22)?
Published date: 14 May 2020

Issue:
We install either a Shunt trip breaker or Isolation Contactor when building an enclosed or MCC installed softstart.

Product Line:
Altistart 22 (ATS22)
Altistart 48 (ATS48)
Altistart 46 (ATS46) - obsolete
Altistart 23 (ATS23) - obsolete

Environment:
All models, all versions.

Resolution:
This is for line isolation.
All softstarts use SCR's to switch the voltage during operation.
Since the solid-state switches (SCR's) may be incapable of completely blocking incoming power should a failure occur (they will almost always fail shorted), auxiliary isolation on the line-side of the controller is required.
The isolation device must be capable of operation via command from the Fault relay of the controller.
An isolation device consisting of either a circuit breaker incorporating a shunt trip coil or an electromagnetic contactor can be used to open the controller power circuit in the event of a controller fault.

This prevents voltage and current from passing through a damaged SCR and single phasing the motor.

https://www.se.com/us/en/faqs/FA90170/​

 

[Tuesdak]

I have the Carrier off brand, ICP, but same age as yours. Already blown one compressor motor cap and the nasty looking evaporator coil I am just waiting for it to finish corroding through.

After the second "brownout" and/or quick flicker of the lights caused my HVAC compressor motor to stall and trip the overheat... The overheat takes hours to reset and that's literally not cool in 110+ heat. The brownouts or quick power blip are not enough to trip the thermostat restart delay etc. An auto transfer switch wouldn't even start the genset from the (guessing utility switching) power blips that have stalled this compressor. So I installed the only "brownout" protection offered for HVAC:

https://www.intermatic.com/en/hvacr/power-protection/cd1-024r

Intermatic. The Compressor Defender is the only all-in-one undervoltage and surge power protection device on the HVAC Market, providing protection for central A/C and heat pump condensing units and their associated motors, controls and components

 

[Timd32]

Single pole contactor is cheaper than a two pole. Simple economics my friend. I wouldn’t hesitate to install either a single or double pole contactor.

Yeah going to figure out a work around for now. I find more weird stuff on household things at times its mostly cost related.

Here is a small statement I found that makes safety/protection sense, just like the situation you experienced:

Why do we have a shunt trip breaker or Isolation contactor in the enclosed Altistart Softstarts (ATS23, ATS46, ATS48, ATS22)?
Published date: 14 May 2020

Issue:
We install either a Shunt trip breaker or Isolation Contactor when building an enclosed or MCC installed softstart.

Product Line:
Altistart 22 (ATS22)
Altistart 48 (ATS48)
Altistart 46 (ATS46) - obsolete
Altistart 23 (ATS23) - obsolete

Environment:
All models, all versions.

Resolution:
This is for line isolation.
All softstarts use SCR's to switch the voltage during operation.
Since the solid-state switches (SCR's) may be incapable of completely blocking incoming power should a failure occur (they will almost always fail shorted), auxiliary isolation on the line-side of the controller is required.
The isolation device must be capable of operation via command from the Fault relay of the controller.
An isolation device consisting of either a circuit breaker incorporating a shunt trip coil or an electromagnetic contactor can be used to open the controller power circuit in the event of a controller fault.

This prevents voltage and current from passing through a damaged SCR and single phasing the motor.

https://www.se.com/us/en/faqs/FA90170/​

This is different then the Shunt Trip for a breaker, but thanks for looking that up, this is like a 2pole contactor but one pole has a bar across the contact.

So the left contact is number 11 is L1. 12 is L1 out, then the second pole is number 23 is L2, and the top side is also 23 L2 but does not switch.

My contactor is essentially shorted closed on 11 and 12, it shifted into Emergency Mode and shuts something down,

The Shunt Trip is used to open the incoming breaker, to protect a unit from a shorted SCR. Kinda plays with the below.

I have the Carrier off brand, ICP, but same age as yours. Already blown one compressor motor cap and the nasty looking evaporator coil I am just waiting for it to finish corroding through.

After the second "brownout" and/or quick flicker of the lights caused my HVAC compressor motor to stall and trip the overheat... The overheat takes hours to reset and that's literally not cool in 110+ heat. The brownouts or quick power blip are not enough to trip the thermostat restart delay etc. An auto transfer switch wouldn't even start the genset from the (guessing utility switching) power blips that have stalled this compressor. So I installed the only "brownout" protection offered for HVAC:

https://www.intermatic.com/en/hvacr/power-protection/cd1-024r

Intermatic. The Compressor Defender is the only all-in-one undervoltage and surge power protection device on the HVAC Market, providing protection for central A/C and heat pump condensing units and their associated motors, controls and components

Thanks for the info I will look into that, yeah 100% similar deal, but just an odd part trying to find it at like Home Depot no luck, but I have contactors I can get this going safely if needed.

Cool little device.

 

[dieselshadow]

Here is a small statement I found that makes safety/protection sense, just like the situation you experienced:
Issue:

We install either a Shunt trip breaker or Isolation Contactor when building an enclosed or MCC installed softstart.



line-side of the controller is required.
The isolation device must be capable of operation via command from the Fault relay of the controller.
An isolation device consisting of either a circuit breaker incorporating a shunt trip coil or an electromagnetic contactor can be used to open the controller power circuit in the event of a controller fault.

This prevents voltage and current from passing through a damaged SCR and single phasing the motor.

https://www.se.com/us/en/faqs/FA90170/​

This. Anytime you have a solid state starter, VFD, Soft Start, VVVF drive, etc., you should have a contactor in between the line source and the motor in case your solid state device shorts closed. Every elevator and escalator I've installed or worked on absolutely require this contactor. Without it obvious bad things could occur if the SCRs shorted.

 

[Timd32]

Thanks for the info.

Will look into the reduced voltage thing.

So guys at work had one, yeah they tell me it's just a cost savings to have one pole be a contact other is feed thru.

They had a 2 pole, said no issue throwing this in.

So later at home will swap it out.

I also ordered a 2 pole so will have a spare.

 

[dieselshadow]

Easy repair.