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[4CSTRAILS]

Ok,I have read all the posts and tried all the combinations trying to hook up a 2nd thermostat but I can't seem to get it to work. I have one heat exchanger in my what seems to be simple oil furnace with forced air. Lets say now I just want to bypass the oil backup and use the blower alone. I can run a seperate power from basement to thermostat area or whatever is needed. How do I hookup this blower. I noticed posts mention line voltage thermostats. Is that what I need? Any help?

[slimjim]

I guess I just don't understand, why do you need a second thermostat.

[4CSTRAILS]

I was reading what others were doing and to have the ability for oil as a backup. Maybe I should rewind and start from the begining.
I just installed a used OWB and have the heat exchanger mounted above the oil furnace after the blower. How do I use the heat from the heat exchanger instead of the oil furnace. I started and ended this first time experience all by myself from hauling 12 cords of wood and the boiler with a pickup and a 16 foot trailer(10 fourteen mile round trips,loading the boiler with some pipe and a winch and setting on a 6'x6' slab that I salvaged from my old barn area 70 feet away) I hand dug the trench and burried thermopex and finished the inside install pex and pump started a fire last Sunday and now I am stumped by this final step. I don't mean to be so dramatic but there is hot water running through my heat exchanger and I would like to use it!

[RSI]

How old is the oil furnace? Do you have a fan only position on your thermostat? If it is an older furnace, it may not have low voltage wiring in it that you can tap into with a regular thermostat if it is older. If that is the case you will need to add a relay.

If you can either get more details or post some pics it would help.

[slimjim]

Now here is a man with drive, I like that 4ctrails, we need more people like you in these United States, RSI is one of those guys that can do magic on dual thermostats and heat pumps/ AC, I can help you with the single TT and old oil and gas fired hot air units, as he said the 2 wire thermostat can be wired to a switching relay to control the fan and an aquastat would be used to kill the oil burner when you are delivering hot water to the heat exchanger, can you give us a bit more info on the wires from the thermostat, how many wires?

[4CSTRAILS]

Oil furnace was made in 1996. The OWB has an aquastat on the back that runs a door damper. That is all seperate and I don't want it involved in the thermostat circuit. It looks like the two wires from the thermostat white to w and red to RH run down to the TT on the Honeywell on top of burner. I just noticed when taking the picture that the red and white wire coming off the front of that voltage box run to a side mount humidifier and then upstairs to the humidifier control. I do not use that humidifier. Could that be a problem? Current thermostat is a White Rodgers programable. Left to right  W  RH  B RC and under that is G  O  Y . I really don't need a programable thermostat,I have another white rodgers like in the picture that is not programable if that need be. My 2nd thermostat is the simple slide control type(pictured).

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[RSI]

It looks like the blower is probably controlled from a temperature switch. Is there a silver box up higher on the furnace?

[4CSTRAILS]

Yes, a probe goes into the area right under where I mounted the heat exchanger.

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[RSI]

There is no low voltage wiring so you will need a relay. It looks like you can use that transformer that is already there in the other pic.
Is there just two wires in the cable going to part in the last pic?

[4CSTRAILS]

I see 3. Its hard to read but it looks like red to "load fan" orange to "load limit" and black below in the center.( I can't tell you how much help this is, I can do electronics in a car but this stuff is not my norm.)

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[RSI]

Ok, you should verify the connections but it looks like the red wire in the fan and the black wire is the incoming power.

If that is right, you will just need to connect the common connection on a relay to the black and the NO connection to the red. If there are wire nuts in the junction box, just add a wire to each to go to the relay.

Then on the 24v side, you can use the existing transformer. You will need to run two wires to your thermostat. Connect one to the W and the other to the RH.
At the furnace end, connect a wire from one side of the coil on the relay to one side on the transformer. Then one of the two wires from the thermostat will go to the transformer and the other to the relay coil.

[4CSTRAILS]

Thanks for your help. I will work on this in the morning.My days start at 4 am.

[4CSTRAILS]

Sorry one more question.What am I looking for as far as getting the relay. I assume something to be purchased? Thanks

[RSI]

You will want a relay with a 24v ac coil. I would get one with 2 poles in case you need to add a zone valve later.
Somewhere like grainger or electric supply should stock them.

[hondaracer2oo4]

I have a similar set up to yours. I tried a line voltage thermostat but it couldn't switch the amperage load required when the fan started up. So what I did was get a second programmable thermostat(the other runs the oil burner if the temp in the house drops to a certain point. I then ran the thermostat to this http://www.lowes.com/pd_314869-74493-RA89A1074_0__?productId=3355572&Ntt=honeywell&Ns=p_product_price|0&pl=1&currentURL=%3FNs%3Dp_product_price|0%26Ntt%3Dhoneywell%26page%3D3&facetInfo=  And then ran the switched hot wire from the switching relay to the fan for the plenum.