Hi everyone. My Concord two zone oil fired forced hot air furnace decided to stop coming on the other day. It has a Honeywell EMM-3 zone controller, a relay and a transformer. I had my oil dealer come and look at it, it was working for him. After he left, it stopped again. I took matters into my own hands as I am technically inclined especially with wiring. I replaced the zone controller. The furnace ran one cycle to satisfy the thermostats and shut off normally. Once the thermostats called for heat a second time, nothing. The zone controller shows the furnace is on, but it really isn't. So I replaced the transformer myself. Turned it on, Same thing. Once cycle charlie I call it now. That leaves the relay. Do you agree? Anyway, the transformer came with a relay, I just took it off and put it aside. Now I want to try and use it, but the posts do not match up to what I have in there now. Are there different relays that I can get that will match up better? It's like the relay that is in there now has posts that are missing on the new one and vice versa. I am not worried about heat, if I need heat, I just go and tap the relay with a screwdriver and it kicks the furnace on :-/

What do you guys think? Are there different relays that I can get that I can just pull a wire from one and put it on the other so I don't screw it up?
Steve

My furnace guy was telling me that I probably should have had two transformers and relays hooked up. It might be that the singel relay is getting weak and wearing out in other words. Sort of makes sense. I told him "your company is the one that installed this thing, can I blame you?? Of course not he said haha. We'll see...

I would give making the relay you have work if it matches the requirements. Most relays have 4 terminals, line, load, and 2 coil terminals. If the coil and switched voltage are the same, sometimes line is combined with one coil terminal. So identify the coil terminals. One connects to the white wire from the zone controller and the other to the common of the transformer. Line connects to the incoming power, and load to your blower or damper. As long as you sort out the coil terminals from line and load, it should work.

One complication is a double throw relay. Line connects to com. It will be connected to the NCC terminal until the coil is energized. It them switches the common from NCC to NOC. If the old relay only had line and load, chances are the new one will work if you connect them to com and NOC. Some zone systems must have double throw relays.