Need unusual time delay control

Steve Garson_2

Matt:

You are a life-saver! Another kudo to the wonders of heating-help.com.

Thanks,

Steve

Steve Garson_2

Unusual time delay control needed

I am installing an AC system in a public accessed poolhouse. Sometimes, people will prop the door open.

My interest: to attached a magnetic low voltage reed switch on the door. When the door is open for more than five or more minutes, the control would shut off the circuit to the thermostat and shut off the AC. When the door is opened and closed normally, it would have any effect on the circuit.

I have found controls that will shut off the ciruit on the opening of a circuit and prevent restart for a set period, but nothing that will shut off the circuit the way I would like.

Any thoughts?

Steve Garson

Matt_67

I'm not sure about your sequence of operations - but for a control you might be able to use an off delay timer like a Grainger 6A859. Run the door switch through the start circuit contacts on the relay - when the door is closed the set of dry contacts in the relay will transfer and stay that way until the door has been opened for more than five minutes. When the door closes again the dry contacts will again transfer. (I think that relay may require 120v - I know they have similar relays for 24V.)

Steve Garson_2

Matt:

I think this relay will provide shut-off after five minutes, but I need the added ability to have the relay do nothing (ie not shut off the device) when there is normal opening and closing of the door contacts. So the timer circuit would stop when the contacts close if they close in less than five minutes. The specs on the one you suggest aren't detailed enought to say is this is how it works. But it's a starting point to Google from.

Steve

Matt_67

It works like this - when you make a circuit between two terminals of the relay - the dry set of contacts close at that moment. When you open the circuit - the contacts remain closed until the end of the timing period - at which point they open. If the door opens and is shut before the timing period ends, the contacts will remain closed - EDIT - in other words - it only acts as a timer when the door switch is open - if it is closed so will the dry contacts on the relay.