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[brian79z]

I've been looking through the posts, but a lot are confusing with how the hookups are with aquastats & such.
My issue is much simpler than that.

New Natural gas furnace in the basement.
Outdoor wood boiler that pumps 24/7 when I turn it on in November until April.
OWB piped into a heat exchanger in the Nat gas furnace plenum box.

Last year, I had 2 thermostats side by side.  The Nat Gas thermostat was set to a much lower temperature to avoid kicking on the burners. (65deg F)
The adjacent OWB "heat only" thermostat was set to kick on the "fan only" when the temp dropped below 72

Right now, the outside temp is fluctuating... not enough to start the OWB yet.
So-- I want to have periodic Nat Gas heat. -- But my setup which I though tested & worked last year -- does not work now.  In fact, I can't get the Nat Gas to fire at all.

HELP----
I need to find a single thermostat that can handle my exact needs. (fan only for 72deg....  fan & gas heat for 65 deg)
--or--
If that is not possible, I need to figure out the wiring correctly between the 2 thermostats. -- drawings are nice.

Thanks

[slimjim]

I have tried to explain this several times on here and it seems that most usally do the double thermostats but here we go again. You will need 1 Argo relay, 1 Honeywell strap on aquastat. Take the existing TT wires to the TT terminals on the Argo relay and then continue them down to the TT terminals on the burner itself, that is your low voltage side done. Now bring 110 to the power in terminals on the Argo relay, then come off the normally open terminal on the Argo relay with a power(110) wire to the low, medium, or high speed wire on the blower motor itself, your choice which one, cut that wire and attatch the three together, this simply adds another power source to your blower motor. Now for the part most folks don't understand, strap the Honeywell aquastat to the incoming wood boiler line on copper or black iron, (not pex as it will not register the heat as well ) run two wires from the R+B terminals on the aquastat down to the power wire on the burner itself (AKA B-1), cut that wire and attatch the ends to the two wires you brought over from the aquastat, set the aquastat at about 160 degrees, you have just interupted the burner circuit and it cannot fire above the aquastat setpoint, when the aquastat registers below setpoint the burner returns to normal. above the setpoint power is diverted through the Argo relay and powers up the blower only.

[yoderheating]

 Is there a reason a standard two heat thermostat doesn't meet your needs?

[slimjim]

Yoder what I am suggesting works for those people who only have 2 wire TT wires and don't want to tear the walls up to run another TT wire and will maintain a more consistant heat with oil/gas or wood as the source, can you see the benefits.

[Scott7m]

Yoder what I am suggesting works for those people who only have 2 wire TT wires and don't want to tear the walls up to run another TT wire and will maintain a more consistant heat with oil/gas or wood as the source, can you see the benefits.

You don't have to tear walls out, u can run jumper wires from the existing stat...  But I see very little of the situations you all have in the ne

[WoodMOJoe]

I know nothing of how these thermostat setups interact (but will have to learn real soon when I go to hook up my system) but thought I would throw in something I just experienced this morning...

Tried to fire up my Carrier propane upflow furnace and I am pretty sure my gas valve is not opening, haven't determined if it getting voltage yet.  Anyways, if your setup was working last year and now it's not, it is possible that you have an issue with your furnace.

with that little bit of info I now send it back to the guys that have forgotten more about this stuff than I will ever know...   

[yoderheating]

Slim, I use aquastats fairly often although I just use 24v ones. In the case of Brian if he had a g terminal in his furnace you wouldn't even need a relay with an aquastat. And if he had at least a 3 wire thermostat wire pulled all he would need is a 2 heat thermostat.
 In my area we are normally dealing with heat pumps which means there are already 2 heat sources so it makes it more complected.  I either use a 24v aquastat to block the heat sources when the outdoor furnace is providing heat or a second thermostat with a relay to prevent back feeding. The key is to make everything automatic.
 The method you describe would work well I believe, its just not the type of situation I run into very often.

[slimjim]

Yes Yoder you are right, up here very few homes have heat pumps, and down your way there seems to be very little for hydronic heating, most homes up here that I go into have oil boilers that hacked in by the oil companies with almost no regard for expansion of the system ( two wire thermostat wire and then they staple it up so pulling new wire can be a beach.