HVAC / electrical guys inside please

[Rich]

In our house, we have a oil-burning, forced-air heating system. On the main floor, there's also a free-standing coal stove, which we like to use. Problem is, when we run the coal stove, the main heating system never kicks on, so the basement and a few rooms (like the bathroom off the kitchen) are very cold.

I want to be able to turn the fan switch on the thermostat from auto to ON and have it circulate air around, which will take care of the issue.

Last year, I replaced the old-school dial thermostat (2-wire) with a programmable one that works for any system.. heating, , heat pump, furnace, etc.

The wire going to the t-stat from the furnace is 5-wire, I hooked up a third wire to provide voltage to the new t-stat, so that's good, but I'm not 100% what I need to connect on the PCB of the furnace and then to the t-stat to enable manual fan control. (Currently, when the 2 wires on the t-stat get continuity, it starts a series of events... the oil unit kicks on, heats the furnace, then once the temp is up high enough, the blower fan engages and starts blowing warm air)

I'll take some close-up photos of the PCB and the schematic label on the furnace.. anyone think they can help? (I'm sure I can handle the t-stat hookup, the instructions were quite simple for that)

 

[rattlecanpaint]

Does the new t stat not have manual fan switch?

 

[rockcity]

Does the new t stat not have manual fan switch?

it should.

I've hooked up quite a few in the past. I'm no HVAC tech but have done enough to get me by and make it work. But, without being there it'll be tough. Pics would help so we know what wire is where

 

[Rich]

Does the new t stat not have manual fan switch?

It does.. it has the typical heat/off/cool switch, then a Fan auto/on switch.

But having a replaced a 2-wire bi-metal spring/mercury bulb t-stat that had no options, it can't control the fan manually, since only the wires to initiate the normal heating sequence are connected.

If I wasn't clear in the first post.. I'm trying to enable functionality that is likely available on the furnace, but not currently enabled by the minimalistic wiring that's currently setup. it's NOT an issue with the t-stat, it's the wiring at the furnace that needs to be modified.

 

[rattlecanpaint]

Ah! I see now! I thought that manual fan mode didn't work since you put the new t stat in. Do you have a wiring diagram on the furnace itself? Should be on one of the panels you take off to service the unit.

 

[Ron]

With no idea how old the unit is, or make model etc. I am shooting in the dark here, but I will do my best.
There *should* be a relay in the furnace for the fan separate from the other functions. If so you can hit that relay (most likely a n/o-c-n/c style) on the appropriate 2 legs and make the fan run.

Get me any additional info you can and pics/diagrams and Ill do what i can.

Since I aint going to PA alternatively you can ship the entire furnace down south I will reverse-engineer label and ship back, freight collect of course.

 

[Rich]

Getting the schematic photographed and converted into something readable was proving to be a challenge...

Fortunately, the manual for the t-stat gave me a hint.. thank goodness this stuff is (mostly) standardized! The elusive "G" wire actuates the relay when 24VAC form the C terminal is applied to it..

I appreciate the offer to reverse engineer the furnace... fucker.

Now houseguests won't have to freeze while the rest of the house is a toasty 75! (or vice-versa in the summer!)