type of thermostat for simple oil furnace (heat)

alano9999

Hi - have a older Honeywell Chronotherm thermostat model T8090A 1056.. Model has a mercury bulb and battery operated clock and clock pins to adjust the temperature for lower heat or higher heat. (Red vs Blue). I also have a simple oil fired furnace for winter heat. (House has no HVAC duct work.) I unfortunately broke one of the Red Pins on the unit and Honeywell cant replace this piece. So while the thermostat still works, I was thinking to replace it. Feeling overwhelmed about the choices out there. I'm pretty sure that I do not have a C wire which a lot of Internet controlled Thermostats need. Any recommendations for a replacement thermostat?

Jamie Hall

Almost any inexpensive battery powered thermostat will do. You can get them in simple versions, ones which have two different (weekend/weeday) programs, or seven different ones. Or without any programming at all. If you don't need the programming, keep the Chronotherm. It will never quit on you.

Any chance you could MacGyver a replacement pin for the broken one? Bet you could...

EdTheHeaterMan

Lots of old timers will tell you to never get rid of your Mercury switch Thermostat. They are basic, simple and have a great track record for dependability and accuracy if proper installed. That said, I agree with @Jamie Hall if you don't need the timer setback function... keep it.

If however you are looking for something that can be controlled remotely from an App on your smartphone, then you need to look at the reviews for the different WiFi thermostats. And there are some that have the ability to use an existing 2 conductor thermostat wire. Some of the popular smart thermostats are made by Resideo (formarly Honeywell), Nest, Amazon, and Ecobee. They have adaptors to use the existing 2 conductors to power the thermostat.

The simplest way is to get a new thermostat wire with at least 3 conductors. Sometimes the existing wire has three conductors where the unused conductor is wrapped around the wire and stuffed inside the wall. You should investigate that before you purchase the replacement thermostat. Then you will need to know what the thermostat is connected to. Some oil heat controls do not have an easy place to add the third wire (often called the C wire). Some oil burner controls do have a place to add the C wire. What control (part number or model number) is your current thermostat wire connected to?

HVACNUT

You can set it up for heat only. Uses only 2 wires (R and W) and takes 2 AA batteries. Very easy to install, and just as accurate as what you have as long as the CPH is set correctly. You can always come back here if you need help with it, or any other thermostat. 

JUGHNE

Some Chromotherms tstats had a separate 24 volt transformer/circuit for the motor.
You might have 2 extra wires connected to tstat. If so, transformer is near furnace and always hot.

alano9999

Hi Jaime.
In process of 'Macgyvering' one out of stiff wire for the Chrontherm- we'll see

Hi EdTheHeaterMan - It seems that I have only a 2 wire (Red and White) connecting to a Carlin 60200-02 box that has TT TT terminal indicators. White is connected to one Terminal and Red is connected to the other 'T' terminal. Looks like no third wire as expected....

Big Ed_4

I Like the T4

EdTheHeaterMan

alano9999 said:

Hi Jaime.
In process of 'Macgyvering' one out of stiff wire for the Chrontherm- we'll see

Hi EdTheHeaterMan - It seems that I have only a 2 wire (Red and White) connecting to a Carlin 60200-02 box that has TT TT terminal indicators. White is connected to one Terminal and Red is connected to the other 'T' terminal. Looks like no third wire as expected....

That primary control does not have a place to connect the C wire from a smart thermostat. If you really, really, really, really, really, want a WiFi thermostat there is a way to do it, but if WiFi is not mandatory, then the T4 that @HVACNUT suggests is your best option.

Just be sure to change the batteries every year. they might last 2 years but you don't want a No Heat service call one evening because the batteries died.

Funny Story, (but not for this customers son)
I got a No Heat Call from a customer and at the time My minimum service call was $39.00 (yea... a long time ago). I found that the batteries in the thermostat were dead, I had a Flat Rate for replacing batteries when I supplied them. It might have been 10.00 at the time. It included parts and labor. Like maybe $2.00 battery cost and 3 minutes labor, the automatic markup and overhead costs were included in the $10.00.

The homeowner was not home ( a single mom) and the middle school child gave me access. I called the owner at work to get an OK for a $50.00 repair, and got it. Within 15 Minutes I was on my way to the next call. Easy Peesy... Right?

That evening I got a call from that customer in a rage. She had just replaced the batteries a month earlier and was questioning my $10.00 charge for batteries. That was outrageous for something she already replaced last month, Do batteries go bad that fast?. I explained the flat rate includes the labor to make the repair. and that for such a short repair like 3 minutes the labor was only $8.00 plus the minimum service call fee of $39.00, so the total was $49.00. I apologized for not telling her over the phone at work all the details, but it appeared that you were very busy at the time and since you were a regular customer, I didn’t want to bother you with emailing the invoice so you can approve and sign it, then email it back. And it was only $49.00.

Two days later she called me to apologize. It seems that her son helped her with the thermostat battery replacement. And her son’s Gameboy® batteries died. Knowing where he could find some relatively new batteries, he swapped the dead batteries in the Gameboy with the thermostat batteries. Who needs heat anyway when you can’t play on your Gameboy?