Harman XXV themostat sensativity

[aqualab]

Hi,

Just fired up the stove last night and noticed that the room's temp was not really corresponding to what I have the potentiometer set at (@70 degrees), the house thermostat was reading 75 and the stove was still running full tilt. Top of the stove was hot to the touch even with the blower running - don't remember that happening before. I think I have had the stove going on five years. I always operate the stove in room temp, not stove temp. The temp probe was not moved from its position last year- coiled up, off the back of stove - not touching the stove or wall. I replaced the temp probe last year - Labrador Retiever puppy. Does the temp controller/potentiometer in the control box need cleaning maybe, contacts dirty? Just seems that the thermostat "being off" is getting worse every year.

Thanks,
Bill

 

[SidecarFlip]

It depends entirely on the physical type of temperature controller, how accurate the control is and to a large part, the location of the sensing element and to a lesser extent, the path of convection currents in the heated room, versus cooler areas.

Most commercially availabe thermostats are accurate to 2-3 degrees of setpoint, but that again, will depend entirely on the physical location of the probe (or thermostat itself.

I control my unit with a digital wall thermostat located in an adjacent room. The convection currents that affect the temperature settings will allow the room where the appliance is located to climb 7-10 degrees warmer than the room where the control is located at. You also have to keep in mind that, unlike central heat, the appliance isn't ;on and off'. It's heat up and cool down so the temperature swings will be much greater that a central heat plant.

 

[aqualab]

The house thermostat (propane furnace/central air) is in the same room that the stove is located in - 20' x 26' open floor plan with no doors to the off rooms (kitchen, foyer, dining room areas). SidecarFlip, I'm referring to the stoves thermostat on the control panel losing its accuracy - I believe it is just a potentiometer. It is probably a cheapy one at that, but it was much more accurate when I first got the stove. Has drifted further off into running hotter the past couple of years. I have never looked in the control panel to see its guts, planning on doing that next weekend to check the temp control type and clean it if I can. I thought I remember awhile back somebody on this forum describing how they switched out the temp control for a better brand one? Now if I have it set at 70 it continues to burn when the room is 75+ (according to the house thermostat). You can obviously feel that the area is too warm also - uncomfortable so I know the house thermostat is somewhat correct. I then have to turn the temp control knob on the stove down to 60 or so to get it to shut down and then later on the area is too cool and I have to turn the control knob up - major PITA cycle. Concerned when we are at work and am relying on the stove to keep the house comfortable throughout the day. Anyone else had to clean the contacts or replace the temp control on the stove's control panel?

Thanks Again,
Bill

 

[gbreda]

Dont know how much this matters in Room Temp mode, but have you cleaned the exhaust probe?

 

[jtakeman]

The probe is measuring temps were its located. Do you have a portable thermometer? Put it were tha probe is and see what its is seeing for temps.

 

[gbreda]

The probe is measuring temps were its located. Do you have a portable thermometer? Put it were tha probe is and see what its is seeing for temps.

Thought the same thing at first, but the OP says it is coiled behind the stove and this is where it has been for years.

Bill says that the top of the stove is getting hot. Generally the XXV does not get all that hot, especially at this time of year as it shouldnt need to run all that much. You can out your hand on top and not get burned at all. This is what leads me to the exhaust probe possibly bing dirty or bad.

Try the stove in stove temp/manual for a while and see if it holds steady, If it does, that might eliminate the probe.

Also, I may be wrong, but I thought I had read about some cutting off the leads to the room temp wire and putting better better contacts on it.

 

[jtakeman]

The probe is measuring temps were its located. Do you have a portable thermometer? Put it were tha probe is and see what its is seeing for temps.

Thought the same thing at first, but the OP says it is coiled behind the stove and this is where it has been for years.

Bill says that the top of the stove is getting hot. Generally the XXV does not get all that hot, especially at this time of year as it shouldnt need to run all that much. You can out your hand on top and not get burned at all. This is what leads me to the exhaust probe possibly bing dirty or bad.

Try the stove in stove temp/manual for a while and see if it holds steady, If it does, that might eliminate the probe.

Also, I may be wrong, but I thought I had read about some cutting off the leads to the room temp wire and putting better better contacts on it.

Geno, I was just wondering if there is a big temp difference were the probe is at. Maybe a draft is keeping it cool. My sis has a P43 and we extended the probe closer to where the furnace stat was at. Now the stove dial is at 70 just like the furnace stat. We found the the stove drawing cool air might have made the probe seem to be off. We put a stat right were the probe was placed by the installer and the temp there was 67ºF. So the stove would over fire the room to around 73ºF.

Now that I know you can use a stat with the probe. She may just do that.

https://www.hearth.com/econtent/index.php/forums/viewthread/59977/

One of my sis biggest complaints was even if you only slightly bumped the dial it would let the house get to warm. With a stat you can set it in 1 degree increments and add the swing function that the Harman doesn't have. Just might do the trick!

 

[SidecarFlip]

Is it possible to run a remote t'stat? My unit has a jumper pair on the main board that allows a remote t'stat which I installed right away. Removing the t'stat from the immediate area allows the unit to maintain a more even heat because the thermostat is sensing ambient temperature in a more differential location. Mine is a goos 20 feet from the appliance.

I actually installed the thermostat in the kitchen where the central furnace t'stat is installed.

 

[aqualab]

Thanks for all the suggestions - I will play with it more this weekend (presently out of town on business). I don't believe there is a breeze behind the stove where the sensing bulb is coiled. How do I check/get to the exhaust bulb - through rear access panel? Can you just remove same and clean? Do they get creosote/soot build-up on them?

 

[gbreda]

Thanks for all the suggestions - I will play with it more this weekend (presently out of town on business). I don't believe there is a breeze behind the stove where the sensing bulb is coiled. How do I check/get to the exhaust bulb - through rear access panel? Can you just remove same and clean? Do they get creosote/soot build-up on them?

The exhaust probe is located inside the exhaust flange. Remove the back cover (right side if looking from the front) and you will see 2 wires going to the top of exhaust flange. There is 1 set screw holding the probe in place. Remove the screw and the probe. Clean the probe with alcohol. This should be done after every ton burned as well as even ash buildup can mess up the stove temp readings to the controller.

Also, as Jay mentioned, try moving the wire to somewhere within the room. It is not suggested to coil the temp wire behind the stove as it defeates the purpose of it's function. It may have worked in the past, but if the exhaust probe does not solve the issue, give this a try.

Let us know how it works out.

 

[aqualab]

Thanks for all the suggestions and information. I removed the exhaust probe and cleaned it with alcohol this past weekend. It had a little creosote-like staining, hardly any build-up. I also moved the temp sensor to a location that receives more air movement/circulation. Stove is now working like a charm and the temperature adjustment is more precise. Appreciate everyone's help.