ATS- Engine shutdown circuit

[mbrooke]

Why would an elevator transfer switch require an engine shutdown circuit? Basically any ATS in the building (life safety, critical, fire pump, ect) can start the backup generator (2 wire start), however the generator will not begin its cool down sequence until all elevator ATSs have transferred back to normal power. The 2 wire shutdown circuit is separate to that of the 2 wire engine start circuit. Anyone seen this before? Or know the reasoning?

 

[dmsv10]

I've engineered a transfer inhibit switch on an ATS before, in my case, specifically, the ATS that was feeding the critical UPS and Battery systems including the maintenance bypass cabinet.

I've never used a specific set of contacts to inhibit transfer on an elevator by itself, only on the building main ATS so onsite staff or operating engineers can decide and verify the following:

1. Are all life safety and UPS systems operating normally on generator power?
2. Is the client in the building going to experience another outage and/or has the issue been identified with local utility company?
3. Is it safe to retransfer to Utility?

My experience has lead towards utilizing the logic in the Main ATS and not having a rouge relay hidden in an elevator closet that most do not have access to.

Unless its specified by local code, it could be required to ensure that the elevators be the last or first to re transfer.

Many other variables to consider.

Sent from my LGMP260 using Tapatalk

 

[mbrooke]

I've engineered a transfer inhibit switch on an ATS before, in my case, specifically, the ATS that was feeding the critical UPS and Battery systems including the maintenance bypass cabinet.

I've never used a specific set of contacts to inhibit transfer on an elevator by itself, only on the building main ATS so onsite staff or operating engineers can decide and verify the following:

1. Are all life safety and UPS systems operating normally on generator power?
2. Is the client in the building going to experience another outage and/or has the issue been identified with local utility company?
3. Is it safe to retransfer to Utility?

My experience has lead towards utilizing the logic in the Main ATS and not having a rouge relay hidden in an elevator closet that most do not have access to.

Unless its specified by local code, it could be required to ensure that the elevators be the last or first to re transfer.

Many other variables to consider.

Sent from my LGMP260 using Tapatalk

Thanks

The engine shutdown only circuit goes to the elevator ATSs, specifically the shutdown circuit relies on a micro switche that only opens when the ATS is actuated to normal power. In other words its just looking for the physical transfer of emergency to normal.

The start circuit on the other hand relies solely on voltage and frequency- any preset deviation closes the circuit to initiate start.


Once the start circuit is broken, the engine just needs the shutdown circuit to open.

 

[ATSman]

SD and PO Loops

SD and PO Loops

I have not seen it done with elevator circuits but this is common practice in the Telco central offices out here. They use the 52/a contact in the normal breaker of the transfer pair or the aux contact in a stand alone ATS wired in series to complete a shutdown (SD loop) loop to initiate the shutdown of the generator. When all breakers/ATSs are back to normal position it starts the gen cooldown timer then the generator shuts down. The theory is that if one of the ATSs gets stuck in emergency they don't want the generator shutting down and dumping the load. Consider it a permissive circuit.
Here it looks like they want to prevent loss of power to any car (should a failure occur) after it runs on gen power and the utility returns.
Telco's also employ a Proper Operation (PO) loop that works the same way only in the transfer to gen. This sends an alarm to the NOC when ever a failure occurs of any unit in the lineup in the transfer to gen and dispatches an operator.

 

[mbrooke]

I have not seen it done with elevator circuits but this is common practice in the Telco central offices out here. They use the 52/a contact in the normal breaker of the transfer pair or the aux contact in a stand alone ATS wired in series to complete a shutdown (SD loop) loop to initiate the shutdown of the generator. When all breakers/ATSs are back to normal position it starts the gen cooldown timer then the generator shuts down. The theory is that if one of the ATSs gets stuck in emergency they don't want the generator shutting down and dumping the load. Consider it a permissive circuit.
Here it looks like they want to prevent loss of power to any car (should a failure occur) after it runs on gen power and the utility returns.
Telco's also employ a Proper Operation (PO) loop that works the same way only in the transfer to gen. This sends an alarm to the NOC when ever a failure occurs of any unit in the lineup in the transfer to gen and dispatches an operator.

That has to be it- makes a lot of sense now that I think about it. This is a hospital- I doubt they want to loose elevator service from a failed ATS.