Help installing the wood furnace

Sawyerfortyish · December 09, 2005, 11:52:10 PM

Took a look at the plenum on my forced hot air furnace where I have to install my heat exchanger. There is a switch for my blower with a thermostat that sticks in the plenum right where i have to put the heat exchanger. The switch is a auto/man switch for the blower it also has a thermostat. My question for you furnace guys is can I move this switch? does the thermostat in the plenum have to be kept any certain distance from a heat exchanger? How does the blower hook up to come on and off to push heat through the house? I hear everyone say how good these wood furnaces are but they come with Dang little instructions to install em.

Jason_WI · December 10, 2005, 12:13:57 AM

Having just installed a heat exchanger in my grandmas mobil home that has a 30 year old oil furnace, I know your frustation. That thermostat in the plenum is used to keep the fan on until the plenum cools off to the set temperature. I added a bypass switch on that thermostat when using wood heat. With the heat exchanger always being hot the thermostat in the plenum would never cool off so the fan would always run. As far as moving the thermostat in the plenum I don't know how that would affect operation when your not using wood for heat. I suppose instead of using that thermostat you could use a time delay relay and set is to turn off a minute or two after the thermostat reached its setpoint. That way you don't have to worry about the switch and the plenum will be cooled off if not using wood for the heat source.

I needed to add thermostat controlled fan switch to my grandmas furnace as it didnt have a seperate fan control from the burner. I wired the 120V hot for the fan to the contactor of the fan control switch. I have a seperate thermostat on the wall for using the wood heat. When this thermostat calls for heat, just the fan will run and will turn off the second the thermostat has reached its setpoint.

Hope this helps.

Jason

woodmills1 · December 10, 2005, 07:59:17 AM

sawyer I thought I was going to have the same problem. Look at the probe from the the switch on the furnace and see how far it actually sticks up into the furnace. Also look at the bottem of your new heat exchanger to see if the distance between the fins themselves and the outside mounting area will allow enough clearance for the excanger to clear the end of the probe.

I found on mine that the fins were recessed far enough that by mounting the exchanger up about 1.5 inch over the bottem of the plenum I got the exchanger about 2 inches above the end of the probe.

so far the furnace fan only comes on when the house demands heat. that is I havent had the problem of the heat in the exchanger triggering the fan by itself. 2 things, the temp of the exchanger I thing is below the temp of the air that would come from burning fuel, and heat rises.

OK on to the thermostat

there are 3 possibilities in order of dificulty and your set up

1. check your existing thermostat for a fan only operation and if it has it use that. If not try this. put your existing thermostat in heat mode if it has choice. make sure it is set so furnace not running. remove cover and jump the G terminal to the R. If the fan comes on without turning on the burner, just hook your new thermostat up to those two terminals.

2. If that doesnt work go to your furnace and locate the control for the fan relay. it should have a bunch of terminals on one side and a relay coil on the other. I found on mine that by jumping the R terminal to the G terminal the fan came on with out triggering the burner. So I hooked the new thermostat R to the furnace R and the new thermostat W to the furnace G using new wire and it works perfectly. These terminals are not on the burner moter but on a separate relay that was up on the right side of my furnace cabinet.

3. If that doesnt work you need a new second fan relay and will have to use it to power the fan from the new thermostat.

I had pretty good instructions but did get confused on the fan control. I almost called an electritian, but figured out that my old thermostat was only 2 wire and went diectly to the burner. so I jumped all the possible connections on the relay till I found out which 2 worked.

Sawyerfortyish · December 10, 2005, 06:09:30 PM

James my probe for my thermostat comes into the plenum from the side about 4" above the furnace boxand sticks in about a foot. There just might be enough room above it to mount the heat exchanger. I would have to mount it high in plenum just under the point where the ducts are. My thermostat has a manual fan setting but the fan will run all the time on that setting. The boiler is comming in the end of this next week. I already have the heat exchangers but with no instructions. I hope some kind of instructions come with the boiler.

arj · December 10, 2005, 10:29:22 PM

Thats the fan limit switch you can relocate it , but you need to have it or the fan won`t run right
arj

woodmills1 · December 11, 2005, 07:23:30 AM

If the heat exchanger fits above the limit switch and below or before any ducts come off of the plenum I think that will work fine. My heat exchanger is very close to the probe but doesn't cause it to activate

Your current thermostat has fan control, that is the easiest option. That means you already have two wires to control the fan, running from your current thermostat down to the furnace. You will need a new 2 wire thermostat and it will connect to the two terminals in the existing thermostat that control the fan. The new thermostat will then turn the fan on when the house is colder than its setting and then back off when the temp is met. Your old thermostat can be turned way down and will only turn on the furnace when the wood is not delivering heat. By the way this hook up won't interfere with your existing system at all. In other words If you let the fire go out the old thermostat will work just the same at whatever you set it at. I think the lettered connections will be R on new to R on old and W on new to G on old. You can check this out by jumping the R to the G on the old one to see if the fan only comes on.

I set my old thermostat at 50 and so far havent let the fire go down enough for it to come on. Can you say no, zero, zip fuel cost so far.

Sawyerfortyish · December 11, 2005, 07:47:19 AM

I just went and looked I'll probably have to cut a new hole in the plenum and lower that fan controll. I think I can drop it a good 3" then I'll lots of room for the heat exchanger 8). After I get that in I have to have an electrican come anyway to fix the underground electric line I ripped up >:(when putting in the water line to the boiler. Se he can play with the thermostat.

woodmills1 · December 19, 2005, 08:38:18 PM

here are two shots of the crimper I got in my installation package. I was really impressed with the ease of installation of the PEX plumbing.

etat · December 20, 2005, 12:51:36 AM

I plumbed my whole house with pex. Compared to sweating copper it is very very easy to work with. Plumbers around here are just now 'starting' to switch over to it and getting more and more away from sweating copper. Back in the summer I roofed a million dollar plus house (where in the WORLD do people get that kind of money) and all of the plumbing in it was pex.

I did buy a big set of half inch and three/quarter inch crimpers to use. They were pretty expensive but I figure I paid for em with the ease of installation and not worrying about not sweating a copper joint right.

Corley5 · December 20, 2005, 08:50:20 AM

We used the Pex compression fittings. They use two small O rings and a ferul to seal. No compression tool needed. 8) 8) I'd much rather use Pex than copper too

woodmills1 · December 20, 2005, 08:55:08 AM

I talked with sawyer on the phone last night, he just got his stove delivered. One of the questions he had was about the pex, and what kind of crimper to get. Mine came with my installation package and was fine for the 20 or so connections. If I was doing more I would consider a fancier one. I only had compression fittings on the tempering valve on the water heater.

Corley5 · December 20, 2005, 09:00:10 AM

A pex search on E-bay will usually show some crimpers. For ease of use the fittings that we used couldn't be beat but I'm not sure of the cost difference. We've got them on the three outdoor boiler installs on the farm. Both the Heatmor and Crown Royal dealer supplied them with the stoves.

Sawyerfortyish · January 28, 2006, 07:23:34 PM

Well she's up and cookin. It's 38 outside and 83 inside 8). Whew gotta open some windows now. Went to the mill picked up some cutoffs. If I can pick it up and throw it in the loader bucket it'll go in the boiler. Fired it up about noon and got a bed of coals then tonight I filled er up with as big a pieces as I can lift. Ill see how long it burns on that load.

maple flats · January 28, 2006, 08:42:59 PM

I sold outdoor biolers for 12 years. The fan control must be below the heat exchange coil. As far as pex, the crimpers are the way to go. They cost a lot but last forever and the fittings that use these are much more reliable than the compression type and cost far less. If you ever need to remove on you can cut the crimp ring and try to remove the pex but usually you end up cutting a slit to remove it and then to re hook you just start a little shorter. You can buy about 8-12 crimp fittings for the cost of just one compression one and the compression type is very finicky, not tight enough it leaks, too tight the nut cracks. This cracking often happens at a later date, in the middle of the night after it has had many hot cold hot cold cycles. They also often need re tightening after these cycles too or they leak.

Sawyerfortyish · January 29, 2006, 08:57:07 AM

None of the plumbing supply places carry much if any pex fittings or the crimp pliers around here. It hasn't gotten that popular yet. The one supply place that had pex didn't sell the same manufacture brand that I had and it seems you can't go back and fourth with this stuff. So since I only had about 4 crimps and I needed more and the crimp pliers were priced at 200.00+ to me I sweated it all in copper. I had a large toolbox full of 3/4 fittings so all I needed was some lengths of tubbing. The underground lines were done in pex and after about a month I ran into someone that had the crimp pliers I needed and I used them to crimp the 4 fittings on the ends of the pex that I ran underground. If all the companies that made the crimps and fittings would come togeather and make universal crimps and fittings this stuff would be the end of all copper pipe. But each company is doing there own thing and the plumbing supply places won't stock it around here because of the differances between manufactures. Thats what one place told me!