Outdoor Wood Furnace Info
All-Purpose OWF Discussions => Electronics => Topic started by: MaverickM23 on October 12, 2015, 06:00:40 AM
-
Finished up my dads stove install but now need to tackle the thermostat wiring so the blower runs on a call for heat and the oil furnace only runs when it drops to a lower point. I have read numerous posts on this and saw these instructions that utilizes one thermostat and will do exactly what I need it to
Red to Rh or Rc with jumper between the two.
Green to G and W/E with jumper between the two
White to the W2 for gas furnace
Yellow to Y for cooling.
My only problem is that his furnace is older, and it only has a two wire thermostat, just an old round honeywell that runs to two terminals marked T and T, and the fan is controlled by a limit switch, there is no relay or transformer. My question is how can I accomplish a one thermostat setup with his current setup or does it need to be done with two thermostats. It doesnt matter either way if one will work great or if he needs two thats fine, but all the reading Im doing they all have more than two wires so do I need to convert his oil furnace to a 24v setup or will the old wiring work, also his furnace does not have any AC. I appreciate any help
-
When I had my old oil furnace the way that I figured out to do it was use a Honeywell RA89A1074 to turn the blower on in my furnace with one thermostat on the wall. Then I used a second thermostat on the wall to run the oil furnace and set it a few degrees lower then the thermostat for the blower. This worked ok, but was not a great set up. If the oil furnace has to kick in, the blower fan is going to run and run and run because the thermostat for it is calling for heat. I never used oil unless it was a real emergency or something so it wasnt a big deal to me.
-
Have mine set up pretty much like Hondaracer, I stuck with two for the greater differential, most of the ones I seen that could use a single thermostat the differential is only a degree or two before the secondary heat source is activated.
I also had mine set up so the gas furnace would kick on once a day to keep it “dried” out upon my father’s insistence, was much easier to go along than argue about it, I’ve done away with that as if the fan on the furnace is running it’s moving air thru it and should keep it dry regardless.
-
So if I use two different thermostats what would the wiring look like? Could I still use the existing fan limit switch or do I need to upgrade since I only have two wires?
-
You will need someway to turn ONLY the fan in the furnace on. The fan limit switch makes and breaks the connection when the temp in the furnace hits a certain level. I wired my Honeywell RA89A in parallel with the fan limit switch. The problem with this set up is the fan will continue to run all the time if the owb thermostat is telling the RA89A to call for heat.
-
I did read yesterday where Slim said about putting an aquastat on the incoming line that breaks on temperature rise and then connect that aquastat to the furnace oil burner motor so it would turn off the motor and the fan and thermostat would act normally. Anyone done this before, I'm trying to find the part number for an aquastat to use but haven't found one yet
-
The aquastat is a 6006c 1018 by honeywell
-
Well funny you mention that. I guess this would work perfectly in your situation. I say funny because that is just what I did for my new set up. When the boiler temp drops to 140 the aquastat makes the connection. Don't bother with the mechanical aquastats from honeywell. Use a Ranco 111000 or Johnson A19. You can get the Ranco for $50 and it is much more programmable than the mechanical aquastats are.
-
Which one did you go with? I was looking them up and couldn't tell if they would work with clamping it onto my incoming pex or do you just tape the sensor to the pex. Also don't I want one that opens at a certain temp like a high limit it would open? I keep seeing SPDT but not sure if those would work.
-
You want the Ranco 111000-000. http://www.etcsupply.com/ranco-etc111000000-digital-temperature-controller-p-86.html The single pole double throw means that it has a Normaly open(NO) and a Normal closed(NC) post. You would want to use the Normally open post. Then when the temperature hit a certain low point of whatever you set the Ranco to it would make the connection and allow the boiler to run normally until the incoming water reached the high point on the Ranco and killed power to the oil burner again.
-
NICE DESCRIPTION!!
-
Alright that makes much more sense. Thanks for all the help a Ranco is on the way. Now I just have to study the wiring diagram to see which wire I am going to break going to the burner. It is a Williamson R164 Lo Boy.
-
http://www.williamson-thermoflo.com/en/assets/pdf/en_w_thb_manual.pdf
That is the owners manual I believe for yours. Page 14 has the wiring Diagram. I think you should interrupt the black wire(Hot) Located at the bottom on the page going into the Burner Disconnect. That should kill burner power only for you.
-
Here is the closest diagram I can find online http://www.nortekhvac.com/literature/a864a.pdf (http://www.nortekhvac.com/literature/a864a.pdf) its on page 12. I will get a picture of mine tonight to show you its on the back of the front shield but I forgot to take a picture of it.
-
Ok, I think your looking to break that Hot(BL) wire going to your burner mounted Jct. Box.
-
Assuming I read the schematic right, is there any reason you couldn't cut the orange wire from the burner junction box and connect the control side to the common in the ranco, the other end of it to the NO connection and run a wire from the NC to splice in with the red blower motor wire? This would be assuming you are using the ranco on cooling mode. If using heating mode you would need to swap wires on NO and NC.
-
I have attached two photos of my furnace wiring diagram. Its similar to the one on the link I posted. Just trying to see which wire I need to break. Also I was looking at the wiring diagram for the Ranco and I understand breaking the hot line to the burner but what wire would I use for the COM on the upper terminal in the Ranco? If Im just breaking the one wire do I need a COM for it to function properly? One again thanks for all the help.
-
Yes you need a neutral wire to the ranco. Unlike a mechanical thermostat it needs power to run the thermostat.
-
So I assume I can get the neutral from anywhere like the white wire that runs to the fan. Looking at the picture I took do you still think I should break the B wire in the burner mounted junction box?
-
Yes you can grab the nuetral wire from anywhere as long as it's on the same circuit that you are breaking the hot wire from. RSI knows better than I do but I figured killing the whole burner down below would be easiest.
-
What I suggested should turn the blower on instead of the burner when the thermostat calls for heat. The Ranco would divert the power that runs the burner to the fan. When the OWB temp dropped then it would switch back to normal.
If doing it this way, you would want to make sure the blower motor didn't draw more current than the burner control is rated for or use a relay to handle the load.
-
Is there anyway I could get you to do a drawing for me I'm still a little confused on how this should be wired up. I tried drawing it myself but not sure where to break the orange and how to wire up the ranco. Thanks in advance
-
First of all, we should make sure we are all talking about the same thing before it gets confusing. I am not sure if I missed something but I didn't see how you were going to actually make the fan run if you have the Ranco break the B wire. If you have that already figured out, can you post that again. I mentioned using the orange wire because that is probably going to work best if you don't use any other relay.
-
I just realized that what I suggested may not work due to the flame sensor shutting it down the burner control.
I think you will need another relay to be able to get everything to work correctly.
-
What I'm trying to do is to get the Ranco to kill the power to the burner only but keep the power to the fan when the thermostat in the house calls for heat. I figured I would use the Ranco to to break it on a temperature rise so once the loop is say 140 it wold break power to the burner, and if it ever dropped below 140 the ranco would make the connection again and the oil burner would fire.
-
Your still going to need a relay to turn on the fan.
-
So what would the wiring for that look like? Couldn't I break and use the orange and the white going to the oil burner and wire them into the aquastat? Im guessing I would break them after the transformer but not sure if that would work. Any ideas?
-
When I posted the other night it was late and I forgot about the burner control needing to see fire to run.
If you use the orange wire like I suggested, it would run the fan for a few seconds and then shut off because there was no light picked up by the flame sensor.
You will be best off adding another relay. Since there is no usable 24v transformer on the furnace, you would be best off to use a fan center relay or switching relay.
-
So what would that look like with my wiring and would I still be using the aqua stat? It came today and I was gonna start working on it tonite or tomorrow
-
Yes, you would still need it if you want to use a single thermostat.
I think you will want to get a 2 pole fan center.
How it gets wired will depend on how you want it to work. It would be easiest to just wire it up so the fan always ran when the thermostat was calling for heat. This would over ride the existing fan control that only runs the fan when the plenum is hot. If you don't want to do that, you will need to setup the ranco to divert the power from the B wire to the fan wire when the OWB is hot.
We can tell you how to wire it once we know more how you want it to work.
-
That's exactly what I would like it to do, when the thermostat calls for heat I want the fan to come on. Then if the incoming line from the owb is lower than a certain temp say 140 the oil burner would also come on, so if the fire goes out or something we will have freeze protection
-
Ok, then I would use a 2 pole fan center or switching relay.
You would take the wires off the T T connections and connect them to G and RH on the fan center. (or could be T T depending on brand and model) Then you would connect one side of the relay (com and NO) to the T T connections in the furnace.
Then the other side of the relay connect to BLK wire going to the fan and limit to the com, and the R to the NO connection.
The Ranco can just be in series with one of the T wires or the B wire in the furnace. You would connect to com and NO in the ranco.
-
Alright I'm following you so far is there a brand or model fan center or switching relay you would recommend? The only question I have is with the aqua stay I understand wiring in one of the t wires but would that be the hot wire and what would I use as the com?
-
There are two terminal strips in the aquastat. One is just to power it. The other is the relay. The wiring I mentioned was just for the relay side. For the power, just run from the incoming hot and neutral wires shown on the left side of the schematic.
The T wires are the low voltage thermostat connection. What I suggested would turn on the fan and short the T T connections at the same time. When those connections are shorted together, the oil burner will fire. The aquastat would keep them from shorting when the OWB is hot.
With it wired this way, you won't have the delay from when the oil burner fires till when the blower starts. That is because the hot air in the plenum was what turned on the blower.
Also, you will probably have to turn the temp up on the fan control if the heat of the heat exchanger causes the blower to start up. You could probably bypass it with the wiring but it is kind of a safety and should probably be left operational if possible.
-
Pretty much any DPDT relay should work. The fan centers need to mount on a 4x4 electrical box. Switching relays usually have their own enclosure.
-
Sorry about the multiple replies. I should have said DPDT or DPST will work in the last reply.
Something like a Honeywell 845A should work fine.
-
Ok I think Im getting it. Im looking at a Honeywell R845A diagram and I see the T T terminals and also that it needs hooked to 120 power which I could get from where it enters the furnace. Then it has two areas that each have a to Power and Load . I take it those would be the same as NO and COM. My question is it mentions if using low voltage that I also need a separate transformer, so since Im using the one relay for the T T wires back to the furnace control I need that correct? Also the Ranco I got is for 120 only I think, therefore I cant break one of the T wires it has to be the black since that is a 120 line, is my thinking on this correct?
-
Thinking and looking more at different switching relays and would a Honeywell ra832a do what I need? Couldn't I use the incoming thermostat on t t and then use the x x terminals to t t on the furnace that way I wouldn't need a transformer. And then I could use load 1 to power the fan and put the aqua stat in series on the black line ? Does my thinking make sense here
-
The ranco can switch any voltage up to 240v. It would work just fine on the 24v T T connections.
The RA845A would be better than the 832a.
-
Alright thats what I will go with then, one last question I hope. On the relay that I attach to the fan you mentioned connecting it to the black going to the fan and limit and the red to the NO on the relay wouldn't I just want to break the red wire going to the fan motor so that when the thermostat calls for heat it will close that circuit and the fan will run?
-
You can ignore the NC and NO labels in the earlier post if you use the 845a since it is not double throw.
Here is is again modified for the labels in an 845A relay.
You would take the wires off the T T connections and connect them to T and T on the honeywell relay.
You would connect the line and neutral to both the Honeywell and the Ranco line connections. (ranco is labeled com and 120v)
Then you would run a wire from one of the T connections on the furnace to terminal 5 in the honeywell. Run a wire from terminal 6 to the C terminal in the ranco. Run a wire from the NO in the Ranco to the other T on the furnace.
Then run a wire from BLK wire going to the fan and limit to terminal 4 in the honeywell and a wire from R to terminal 3.
Just splice into the R and BLK wires.
-
I drew it out and I think I have it all down, by splicing into the black and red I will be turning the fan on whenever the thermostat calls for heat. This will still function alright if I don't have the OWB going but it will turn the fan on before the plenum is hot if Im only using oil but what happens when the plenum gets warm enough and that switch closes but I already have the fan running? Sorry about all the questions, I just want to do it right and I know you are the guys who can help me do that.
-
If the switch in the plenum closes it won't hurt anything since it would be in parallel but it would keep the fan running after the thermostat quit calling for heat. Hopefully you can turn the temperature on it up high enough so that won't happen. You could disconnect the R wire from the switch so that won't happen. I just like the idea of having it there so if the oil burner is running and the relay failed it would still turn the fan on. If you just disconnect the R wire and leave the other wires it should still have the high limit there to shut the oil burner down.
-
I follow you now thanks so much for all your help I really appreciate it. I have a Honeywell 845a on the way and if I run into problems I will post back, thanks for checking and keeping up with all my posts and questions
-
Just an update but I put in the relay and aquastat as RSI described and the everything works perfect, I did remove the red wire from the fan control so it does still have the limit control but the fan is controlled directly by the thermostat. Fired the stove up and got it all up to 180 and hit the thermostat and the fan kicked on and he is drawing about 20 to 25 degrees off of the heat exchanger in the plenum, I have gauges going in and out of it, the only problem is that the Ranco temperature probe isn't giving a great reading. It is taped to the brass tee that the gauge is on and when the temp on the gauge says 180 the Ranco says 125 guess I need to experiment where to put the probe to get a better reading. But thanks again for everyone's help
-
What type of gauges do you have? If they are in wells, pull out out and put the probe in there and see how it compares.
If that isn't an option, get some aluminum foil tape and tape it tightly to a pipe. Pex is ok if you don't have any copper. Run the tape all the way around the pipe and probe. Then insulate around the section of pipe and probe. Make sure there are no openings in the insulation that air can get in.