CO sensors and overhead doors

[wirebender]

I have a CO sensor system that is designed to open all 15 overhead doors in a truck shop.
It does this with a dry contact just like the start/stop at each door.
Is there some way I can loop them all together and keep them all from opening at the same time when you push 'open' at a start/stop station?
This is the diagram at the door controller.
I don't know how to make it any larger but if you click on it you will go to Photobucket and you can enlarge it there.



They are not using the 'edge' controls.
Can the controller be programmed to allow my CO system to open the doors using the 'edge' inputs?

If that won't work, how can I keep them isolated? Separate cable from each controller to the CO sensor cabinet with some type of relay in each cable?

 

[kwired]

Separate cable from each controller to the CO sensor cabinet with some type of relay in each cable?

Seems like that is what you need - especially if the only time you want to open all 15 at the same time is via the CO sensor equipment. You either need a 15 pole relay or multiple and more easily found three or four pole relays.

Since each door controller has a separate control power supply you may not want to intermix those supplies anyway. In theory they can run parallel to one another, but in a fault condition on one unit it may effect all of them.

 

[GoldDigger]

Seems like that is what you need - especially if the only time you want to open all 15 at the same time is via the CO sensor equipment. You either need a 15 pole relay or multiple and more easily found three or four pole relays.

Since each door controller has a separate control power supply you may not want to intermix those supplies anyway. In theory they can run parallel to one another, but in a fault condition on one unit it may effect all of them.

This deals quite nicely with how to avoid overloading the single dry contact, but it does not address the point not mentioned by the OP about staggering the opening of the doors to avoid VD from all of the motor inrush currents happening at the same time.
Adding time delay relays with different time settings to your design will take care of this too.
Depending on the control circuitry (DC or AC relay actuation) you might be able to use diodes for isolation instead.

 

[DrSparks]

Why couldn't one relay open all 15 doors? Don't the control contacts use only a few mA? Simple math get the specs on the door open contacts and then size a relay accordingly.

 

[steve66]

Why couldn't one relay open all 15 doors? Don't the control contacts use only a few mA? Simple math get the specs on the door open contacts and then size a relay accordingly.

I think the problem is that one relay does open all 15 doors - both when the CO sensor goes off, and when someone just wants to open a single door with a pushbutton.

 

[GoldDigger]

I think the problem is that one relay does open all 15 doors - both when the CO sensor goes off, and when someone just wants to open a single door with a pushbutton.

:thumbsup:
If you bring in the signalling contact by bonding all of the start wires together, without isolation, then you have the problem that you have put all of the actual start switches in parallel too.

If one relay opens all 15 doors via 15 separate contacts, then the individual OPEN buttons remain isolated. A relay which throws a shorting bar across all 15 inputs and the common return rather than having 15 individual contact pairs would work too if you could find one. (Common in electric organs and other hand-built applications.)

 

[kwired]

:thumbsup:
If you bring in the signalling contact by bonding all of the start wires together, without isolation, then you have the problem that you have put all of the actual start switches in parallel too.

If one relay opens all 15 doors via 15 separate contacts, then the individual OPEN buttons remain isolated. A relay which throws a shorting bar across all 15 inputs and the common return rather than having 15 individual contact pairs would work too if you could find one. (Common in electric organs and other hand-built applications.)

How much trouble is potentially introduced because each of the 15 are supplied by separately derived systems? If they have DC control circuit maybe not a problem, but if AC what are chances all 15 are on same phase of the source? I can see some potential for higher then expected current if they are not all in phase with each other. Maybe not as bad as if all the separate sources were connected directly parallel to each other though, but maybe is still going to be increased current. Whether or not one lead (and which one) of the control circuits is grounded or not possibly matters as well.

 

[DrSparks]

How much trouble is potentially introduced because each of the 15 are supplied by separately derived systems? If they have DC control circuit maybe not a problem, but if AC what are chances all 15 are on same phase of the source? I can see some potential for higher then expected current if they are not all in phase with each other. Maybe not as bad as if all the separate sources were connected directly parallel to each other though, but maybe is still going to be increased current. Whether or not one lead (and which one) of the control circuits is grounded or not possibly matters as well.

Good point. The transformers may not necessarily be on the same phase. Most LiftMasters I've seen operate on 24 VDC from my experience, however. Also, if you put the relay down stream from the push buttons, the individual buttons will not activate all the garage doors. Draw it up on paper. There's a way to do it simply! ;-)

 

[wirebender]

My solution wound up being installing a relay with 24 volt coil inside each controller.
Use the normally open as a dry contact to the common and open terminals on the controller and daisy chain the coil terminals back to my CO panel where one of the relays in the panel will energize all the relays.

Voltage drop won't be an issue for the controllers, they are all 460 volts 3 phase, don't pull much and they are on 5 separate breakers, maybe 7 amps max on a breaker. Farthest one is 300 feet.