How do I add a thermostat to my furnace?

[Wagnerwerks]

Hi guys. I've had a wood furnace in my basement for years now, but have yet to wire in a thermostat to call for heat when my house temperature gets too low. Right now it just has the high low thermostat on the back of the stove to keep stove temperatures at a norm. Ideally I would like it to also stop working when my temperature of my wood stove gets too low to produce good heat. I'm not sure if that's a possibility as this is not my strong suit. I am a competent wiring person, not an electrician, but I did wire my own house and pass inspection. Does anyone know of a place with a good diagram or could someone walk me through the parts and pieces I will need to wire in? I really need my temperature of my house in the morning to be higher as my wife is accustomed to living with a wood stove... Aka 80° all the time. Thanks in advance.

 

[Marshy]

You need show us the controls you have now (pics would help). I believe you could add a thermostat in parallel to the existing controls you have that makes everything turn on to regulate the max temp of the unit. You should have an existing control board with relays in it (right?). Not unless you are controlling everything with an on/off switch. Need to know more about what you have.

If you want to set a control so that nothing turns on below a certain temp it's a little more difficult because you will have to add an aquastat to the control circuit. The aquastat for this would be called "close on rise" which means above a certain temp the switch will close and allow power to the controls.

 

[Marshy]

This site will be useful to help you choose a temperature controller.
https://customer.honeywell.com/en-US/Pages/department.aspx?cat=HonECC Catalog&category=Temperature+Controllers&catpath=1.1.3.3

The T7079 might be exactly what you need.

FYI, my knowledge is limited so Im sure you will get a better response from others. Im in the process of installing a boiler and learning the controls part but water boilers are different controls than furnaces which can be controlled with immersion wells for liquid temp vs air temp.

 

[Wagnerwerks]

First of all. Ty. You're awesome.

I have a limit switch right now... Like this

 

[Marshy]

L4064B2236 controls high limit and fan motors in forced air heating systems. Turns fan on and off according to plenum temperature via helical bimetal sensing element.

Application:
These combination warm air fan and limit controllers are suitable for various types of forced air heating systems. The controllers have 2 switches; one which opens the limit circuit if the plenum temperature exceeds the preset safety limit; it resets automatically. The other switch turns the fan on and off. The fan is turned on and off according to plenum temperature. The L4064R has a special high temperature range suitable for gravity heating systems. All models may be used as limit controllers by wiring only the limit side. Limit contacts are suitable for both line voltage and low voltage. For low voltage applications, the brass jumper must be removed."

Operation:

As the plenum temperature rises, the coiled bimetal sensing element of the control warps and mechanically makes the fan contacts (at the FAN ON temperature setting). During normal operation, the call for heat ends before the LIMIT setting is reached and the fan contacts break as the plenum temperature falls and the FAN OFF setting is reached. If the call for heat continues until the temperature in the plenum rises to the LIMIT setting, the bimetal element will mechanically break the limit contacts and de-energize the heating control circuit.

Here is the install document below that I got that info from. I have to run right now but will take a look later.
https://customer.honeywell.com/resources/Techlit/TechLitDocuments/69-0000s/69-0115.pdfI believe the problem you have to battle is if the plenum temp is too high and the thermostat for your living space is not calling for heat then it has to reject heat some how so it turns the fan on to cool the plenum. More to follow.

Edit, take a look at page 4 under "Checkout".

"When installation is complete, disconnect the fan motor circuit at the L4064. Turn on power and set thermostat to call for heat. Burner should come on and limit controller should shut burner off when plenum temperature reaches the limit set point. Turn off power, reconnect the fan switch, turn on power and again set thermostat to call for heat. The fan should start when plenum temperature has reached fan-on setting."

 

[Wagnerwerks]

Ok. So to clarify, my wife want more heat... Right now, I have the limit switch set to come on at 140is and shut off at 100ish. The problem is once the hood temp drops below 140, the blower doesn't come on for the rest of the night. My stove is a vogelzang 2500 with a fire brick lined steel plate on the top with air injection added. It's burning around 8hr burns and my chimney is clean.

 

[Marshy]

Ok. So to clarify, my wife want more heat... Right now, I have the limit switch set to come on at 140is and shut off at 100ish. The problem is once the hood temp drops below 140, the blower doesn't come on for the rest of the night. My stove is a vogelzang 2500 with a fire brick lined steel plate on the top with air injection added. It's burning around 8hr burns and my chimney is clean. View attachment 99012

You have two fans one for combustion and one for the plenum to supply how air to the house right? I know nmothing about that stove.

 

[Redfin]

Aka 80° all the time. Thanks in advance.

Wow Kris, you need to cuddle with the Wifey more if shes that cold.

 

[Dustin4185]

You may check out how Fire Chief has theirs setup. Dad has one and when it calls for heat, the induction blower and and hot air blower kick on. I believ US Stove has a similar setup for add on furnaces.

 

[Marshy]

@Wagnerwerks, do you have a relay control panel of any sorts? There has to be more than that to the controls.

 

[Wagnerwerks]

I have a fan blowing draft that I manually switch on. Literally the only electrical on the stove is the limit control and the blower.

 

[Wagnerwerks]

Wow Kris, you need to cuddle with the Wifey more if shes that cold.

That's my idea too. I have suggested it more than you know. Lol

 

[Wagnerwerks]

Maybe a combo of these? I have the r8239 fan control in my stash...

 

[Marshy]

Where did you get this second print from? That is helpful because it shows a switching relay actuated by the thermosta in series to turn the draft fan on (makes sense to me, bumps the plenum temp up). The first print shows the same wiring scheme. You will need that relay control board for the thermostat to interface with the rest of the controls because the thermostats are a 24 volts.

Sorry, Im still a little confused, do you have only one fan, draft fan for the fire or plenum for space heat?

The second print show the draft fan being controlled by the thermostat's relay in the control board. The thermostat will close the relay and power is sent to the fan. Its in series with the fan limit control (your honeywell) so it can be interrupted if temp gets too high. Make sense?

 

[Wagnerwerks]

I haven't had time to digest this yet. I very seriously appreciate all the help and we'll get back to this project shortly.

 

[paragonbuilder]

Subbed to help out later.