four contacts one ground

[frozenteeth]

Can I use a 5 wire run for my garage door control and contacts? I have two garage doors. I want to run a magnetic door switch to each door and then run wire to each opener. 
 
Can I use a common ground for all of these? or is it just two inputs per ground?
 
Also I'm piggie backing on the current wired garage door switches (at the opener not the switches). One switch is just a simple lighted doorbell type switch and the other is one with two buttons and a motion sensor (typical on garage doors for the light)
 
Should I wire each one separately or can I do as I proposed?

 

[az1324]

No you don't really want to mix grounds from 3 devices with their own power supplies.  So if you are restricted to 5 wires you should isolate the grounds by using relays or other isolation devices.

 

[frozenteeth]

Correction I didn't tell the whole story. On my elk I'm using inputs 7 and 8 with relays for the garage doors. The magnetic door contacts would not have a relay on inputs 9 and 10.
 
I can run more wire I just thought if I could get away with using the one it would be better/easier. I would rather do it right the first time.

 

[az1324]

You mean zones 9 & 10 for the magnets and outputs 7 & 8 for the relays?  If the relays are installed at the openers then you can use a common ground since you are not tying it to any other external grounds.  But if the relays are installed at the ELK then use separate wiring.

 

[frozenteeth]

Yes sorry correct outputs not inputs for 7&8. This is what I thought. Thanks

 

[Del91574]

You don't want to mix outputs and inputs on the same wire using a common....
 
Output common connection depends on whether or not you are using them as a dry contact or not....if you're providing a momentary short (OHD opener) then you don't want to mix the two systems together (2 OHD openers) and best practice would be to separate out the dry contacts. If you're running a wet relay and then providing a trigger voltage, then you'd be able to share a common.
 
Burg or status points, sure, but be aware of troubleshooting when sharing a common.