Control wiring question

[Bones32]

Have old furnace had bad gas valve with the mercury switch in it. Installed new gas valve with a new s8610u spark ignition module. Furnace has fan center relay on it I wired everything on it I get 24v from the limit side to my new module. But I don't know where I connect my 24v ground wire from new ignition module

[Freon]

Please read page 5 of the instructions for the S86 module very carefully. I don't know what module you are replacing but USUALLY (and again, read and check for the module you are replacing) the 24 volt GND terminal on the new control unit to the common. In my case, replacing a S86E, the other transformer wire went to the TH-W lead as noted in the Procedure Notes, far left column.

[Bones32]

Hey thanks! I had to replace an old mercury gas valve that had a white Rodgers relite control. I replaced with a honeywell gas valve and a honeywell s8610u ignition module. The main wiring from valve to control was simple I get my 24 v from the limit switch to new control. But this old furnace has a fan center relay which has w,r,g,b,y terminals on it. Which these can be very tricky. My issue is I'm not sure which terminal to hook upthe 24vground wire from the ignition module to on that fan center relay transformer.

[heatseeker]

Ground wires should go to ground. If you go to ground and it doesn't work than something else is wrong.

[Freon]

You need the schematic to know if b or g is possibly the ground connection, also known as the 'common' designated usually by the letter C. If you can't find the schematic and have an available screw on the metal furnace frame, you can use that as ground. You may see a green wire attached to the furnace frame... again, that's the ground.

On the S86 control you have the 24 V and 24 V (GND) connections. The 24 GND (ground) will attach to the furnace frame... the ground. But the other 24 volt terminal on the S86 may be empty, as it was in my situation. Check page 5 carefully.

[Bones32]

Thanks freon! So the 24vground doesn't technically need to come back to the common side of the transformer. I can ground it to the * Also the b/c terminAl on the transformer has a wire that runs front it through the fan relay back to G on transformer so I don't think I can use though terminals at * Not a 100%sure don't want to fry anything

[Freon]

Again, I'm shooting in the dark since I can't see what you have. Usually all ground connections eventually find their way to the furnace frame which is grounded to the main breaker box. It is very very seldom you have a "floating" ground. So when you connect anything to the furnace frame, you're making a ground connection and using the metal of the furnace frame as the conductor.