I wired a 120v NO relay tied off my wood furnace blower to my gas furnace thermostat board R and G wires. When 120v is applied to my wood furnace blower the NO relay closes and my gas furnace blower starts running when I shut the gas furnace blower door. What's causing a NO relay to energized when power is applied? I'm wanting to run my gas furnace blower when the wood furnace blower kicks in.
120v NO SPST relay
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If I'm understanding this correctly your gas blower is running when it shouldn't? If that's the case it sounds like your relay might be NC or its a DPST and your on the wrong side.
Edit: I'm having a hard time understanding this. On 2nd read it almost sounds like it's working as you want it to.
Edit: I'm having a hard time understanding this. On 2nd read it almost sounds like it's working as you want it to.
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brenndatomu
Minister of Fire
brenndatomu
Minister of Fire
I am inferring that the wood furnace blower is an ECM that is always powered and OP only wants the relay to close when the motor is running.
maple1
Minister of Fire
I'm looking at these two statements
OP, enlighten us please.
Which seem to imply that "120v applied" is not the same as "kicking in". Somehow the first blower is getting 120v without running, and that causes the second blower to run.
OP, enlighten us please.
brenndatomu
Minister of Fire
No just a standard blower motor.
This is all continued from another thread (not sure why it got separated) where OP wants the gas furnace blower to kick on when the "add-on" wood furnace blower starts...I advised him to wire in a 120V relay that is activated by the wood furnace blower being powered up, which in turn kicks the gas furnace blower on by closing the R/G circuit of the gas furnace tstat...which should start the blower on the speed it runs for heat...and it sounds like its working to me...?
I wired a 120v relay from the load and line side of the fan and limit switch of the wood furnace blower. I ran the other two sides to R and G. When I plug in my wood furnace blower to get power the relay closes which makes the gas furnace blower run non stop. Something I have done is making it get power constantly instead of when the wood furnace blower kicks on and should make the relay trip and then turn on the gas furnace.
That's your problem. You jumped the relay across the limit switch which is basically putting it in series with the motor.
Just connect one lead of the relay to the "fan" side of the limit switch. Then the other lead goes to neutral.
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![[Hearth.com] 120v NO SPST relay](https://www.hearth.com/talk/data/attachments/285/285763-8c795e4d6dc0fda9de7f1f6a1a976e50.jpg?hash=KhgBnxiRWd "[Hearth.com] 120v NO SPST relay")
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You should not hook anything to the "line" part of the switch. Just hook one half of the relay coil to the fan "load" terminal and the other relay coil terminal to a neutral wire in the furnace. Right now you have current going from the "line" (always hot) through the relay coil, and then going through the fan motor windings and *then* to neutral, not good, and the relay will always be energized.
You should not hook anything to the "line" part of the switch. Just hook one half of the relay coil to the fan "load" terminal and the other relay coil terminal to a neutral wire in the furnace. Right now you have current going from the "line" (always hot) through the relay coil, and then going through the fan motor windings and *then* to neutral, not good, and the relay will always be energized.
It's like you connected a light bulb to the two terminals on a light switch and can't figure out why the switch doesn't work.
The relay needs to be in series with the switch, not across it.
There are no neutral wires in that limit switch box so you need to go elsewhere. Go where the fan is, find the wires going directly to the fan and hook your relay in parallel with those.
The relay needs to be in series with the switch, not across it.
There are no neutral wires in that limit switch box so you need to go elsewhere. Go where the fan is, find the wires going directly to the fan and hook your relay in parallel with those.
brenndatomu
Minister of Fire
brenndatomu
Minister of Fire
No offense meant to the OP, but this is why I am increasingly hesistant to help people wire up custom controls like this...
brenndatomu
Minister of Fire
If you are tied to the neutral, and the other wire is powered up only when the wood furnace blower runs, then it should work...the relay will only close when it has power and ground (neutral) connections made to the relay coil.
No offense taken. I'm not very electrical knowledgeable. Can't seen to find neutral on blower motor but hooked other lead in white neutral coming from plug and relay still closes.
![[Hearth.com] 120v NO SPST relay](https://www.hearth.com/talk/data/attachments/285/285769-993dadd70739192d84d06ffb34a7ae77.jpg?hash=XcPy7iHTvE "[Hearth.com] 120v NO SPST relay")
![[Hearth.com] 120v NO SPST relay](https://www.hearth.com/talk/data/attachments/285/285770-9a682a7562ad320a674a498656ba7b3a.jpg?hash=aSnBCca98T "[Hearth.com] 120v NO SPST relay")
Never tie anything to green/ground, that conductor (although it doesn't look like it's hooked up at all to your furnace which is.......ugh) should never be used to carry any current, even from a small relay coil. If your last picture is the cord coming from the wall/outlet in the bottom of that box, black from the wall cord "should" be hot and white "should" be neutral. In your last pic, purple is tied to hot/line from the wall and the other black(furnace/blower wire?) is tied to *white* from the wall, which is, or should be, neutral. Looking at your first pictures, it looks like you tied the purple wire onto the "load" side of the fan control - if this is the same purple wire in each location, it most likely was originally on the "line" side of the fan control/limit switch and has been reversed by mistake. Without a schematic or understanding where every wire on that furnace goes, due to the odd color schemes, tying black with white/neutral/etc you are treading on confusing and possibly dangerous ground until you have understood/mapped out the complete set of circuits you are dealing with and know what all the wire colors should be going to, which ones are hot and neutral, etc. You should really have a multi-meter to verify your hot/neutral from the wall, a schematic (factory or diy drawing from tracing out all the wiring), and a complete understanding of the wiring before you go further.
Original owner I got furnace off of had the load and line wires backwards. Reversed them and wired one to load and one to neutral and everything works now. Thank you all for your advice!
brenndatomu
Minister of Fire
Early in my career all my training was on 12VDC vehicle electrical systems...I work on mostly AC stuff now, but I still have a bad habit of using the term "ground" when referring to "neutral", especially when working with something simple like a relay coil. or incandescent light bulb...sorry for any additional confusion I may have added in here with that.
Is it helping to distribute the heat better?
Is it helping to distribute the heat better?
No worries sorry for the wild goose chase there. Took me forever to figure out that wires inside the box down by the blower were not going to right terminals to the fan switch. Yes definitely. I changed the speed from black/high to yellow not sure of the speed but it's lower and still not low enough to keep the air hot. I think red is the lowest so I'm going to try that next.
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