I am trying to automate a commercial door with iTach relay. It requires a brief connection between terminal R1 & R2 which I will achieve with Close/Open commands to the iTach. The problem is that as soon as I put the wires into the iTach terminal blocks, the door opener is activated - even though the relay is Open. I am at a loss to explain the behavior. The opener is a Liftmaster MH5011L, if I read the schematics right, R1 & R2 are using 24VAC
I think you are mis-wiring your garage door opener. If you look at MH5011L-2.png, you can see a terminal strip towards the bottom. It looks like the Open and Close buttons are wired to this strip, but the bottom of the drawing is cut off.
You should wire 1 of the normally-open relay contacts (outputs) in the iTach into terminals 1 & 3 of the opener. This relay should open the door.
Wire another set of normally-open contacts in the iTach to the terminals that are connected to the Close button of the garage door opener. I can't see the terminal numbers on the schematic.
You can leave the original buttons connected, or you can remove them. Essentially, what we are doing is simulating the push buttons with the relays. If you leave the buttons connected, they are in parallel with the relays, which will work fine.
There are two types of relay contacts, normally-open and normally-closed. A normally-open relay contact is open (no connection) when the relay is off. When the relay is energized, the contacts close and complete the circuit.
A normally-closed relay contact is just the opposite. When the relay is off, the contacts are closed and the circuit is completed. When the relay is energized, the contacts open and the circuit is interrupted. You probably originally wired the door opener to a set of normally-closed contacts, which is why it started running immediately!
The door opener has both 24 volts and 120 volts in it. I HIGHLY recommend unplugging it before working on it! A stray screwdriver tip or wire can short things together that won't like it!
Good luck!!
Mike P.
