Varitrac Priority Shutdown

[joey791]

I have an older Varitrac on a job that I looked at yesterday. I have to do on/off through a time clock also this is a building in a plant and the customer wants an emergency shutdown. In looking through the manual I see that there is 3 ways to do this but the easiest looks to be shorting the supply air temp sensor(unit is a split not a Voyager package). Anyone done this before? Any preference? Any help would be appreciated.

[kwillmech]

Depends how important the shutdown is. If really important to stop airflow then I would interrupt power at the a/c unit.

[joey791]

Hey mech I notice that the manual says you can do a priority shutdown by opening the sensor. I have thought about what you said, because I also thought of killing the control power to the panel to shut the unit down, just not certain the best way to go about this yet

thanks for the help mech

[Balibe]

Only advantages to shorting the sensor is it will also send the shutdown to all the devices [UCM's, Bypass, etc]. If you just have dampers with no fans or heat, might be better to just break the control circuit. If you want to extra safe, use a DPDT relay to open the sensor and control circuit.

[kwillmech]

Opening sensor will work.

[joey791]

thanks for the ideas, I'm gonna go with killing R in the control circuit and opening the sensor on 2 different set of contacts.