Water to Air heat exchanger?

mtfallsmikey

Mounted a separate transformer and Honeywell R8229C relay to control both the fan and secondary circ., heating only t-stat with an off switch. This avoids any opportunity for voltage bucking,etc.

James_19

Water to air heat exchanger?

I have an outdoor wood boiler that is plumbed into my house forced air furnace through a water to air heat exchanger. My forced air unit is propane and also has an AC coil in it. I need to know how to wire my thermostat or furnace so that when my thermostat calls for heat the fan just turns on and does not try to call for gas???? Any help would be great.

klaus

Options

Are you going to keep your boiler warm all winter? If so you could just add a second thermostat and use the R and W contacts there. Wire them to the R and G contacts on your furnace. This way a call for heat will bring on your fan. Set this one at least 3 or 4 degrees higher than your LP furnace stat.

If you don't want two thermostats you could could change your existing one out for a two stage thermostat and wire W1 for fan only , G on furnace, and W2 stat to W on the furnace.

Either way will use the boiler as first stage of heat and the LP furnace as a second stage or back up.

If I were doing it I would add a simple temperature sensing switch attached to the water pipe into the control circuit of first stage to prevent blowing cold air around if the fire goes out.

Good Luck, Rich L

Big Ed_4

You want to control the fan when using the wood stove.

You would need a " make on temperture rise aquastat" . You can buy a strap on which will be mounted on the return pipe of wood burning heating coil. Wire from low voltage power source on furnace " R" though new reverse aquastat back to terminal " G" (fan relay)on furnace. Asumming you have a terminal board.

This is one way to split systems. The fan will run if the aquastat sensors the coil being hot. You will have one thermostat controling wood stove and one for AC/propane. Wood thermostat set higher then propane. Run out of wood , then propane is used as back up.

zeke

I would use a single thermostat, with the boiler and fan controlled normally.
Assuming the outdoor unit has enough heating power to handle the heating load alone, then the furnace, is a backup. Therefore you need something to detect a failure of the boiler and turn on the furnace unit. I would use a time delay relay (TDR) that is powered by the Tstat and wired in series with a thermal switch located in the the ducting, set to close at say less than 90 F.
For example, assume that the tstat calls, then the fan and the outddor boiler are activated and the TDR is powered . After say 30 seconds, if the temperature in the supply duct is less than 90 F, the TDR contact closes and being in series with the Tstat provides the signal to actvate the gas unit.

World Plumber

The Honeywell Vision 8000 or IAQ stats have the dual fuel kit built into them. That's what I have been using. Gives you a lot of options. The 8000 you need to run all the wires back to the stat. The new IAQ you mount a modual by the equepment and only need 3 wires back to the stat.

James_19

I have it working the way I wanted it to now. Thanks for everyones help.

Big Ed_4

How did you set it up? Just courous.......

James_19

Big Ed, to be honest with you the biggest problem I had was a blow 3amp fuse on my board after finally finding one to use I did as suggested, first I unwired my exsisting thermostat and just wired the R and G wires and it worked just fine. 2nd I tried wiring a second thermostat which also worked which are short term solutions. I actually need to decide what I want the system to do for me and then wire it correctly.

Anthony_23

two heating sources, two thermostats, 1 duct fan

Sorry James, did you say you wired both thermostats to the same terminals on the gas furnace board? This discussion sounds like my situation, but need a little clarification.

I too have an outdoor wood furnace, with a water to air heat exchanger in the house ductwork. My original furnace is a forced air oil fired furnace. (I currently have no A/C but plan to install in the future. I had planned to rob the A/C connection from my thermostat and wire it to control the fan for my application. )

I want to run the wood furnace as primary heat, and control the exisitng furnace fan to cycle on when wood furnace thermostat calls for heat. I do not want the oil boiler to fire unless the house temp drops below the temperature set on the existing (oil furnace) thermostat. I plan to set wood furnace thermostat high , and oil furnace thermostat low.

I have decided to install a 2nd thermostat for the sole purpose of cycling the exisiting furnace fan. I do not want the oil boiler to fire when under control of the new wood funrace thermostat. However, if the house temp drops too low , into the range of the oil furnace thermostat, the oil furnace works as usual. So, I do not want to disconnect the oil furnace, having to reconnect when required. I want it in automatic reserve.

any help/clarification would be appreciated.

thanks
anthony