P68 erratic temp in room mode

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MarkDon

Member
Feb 22, 2015
24
NE pennsylvania
Hello folks, I’ve been a member for a while but mostly just lurking. I’ve had my P68 for about 13 years and I like to think I’ve become pretty familiar with them. I’ve replaced both blower motors and auger over the years.
This year I’ve been fighting an issue where I cannot get my house to a consistent temperature that I want. It seems to want to run and keep the house at 75/76 degrees or around 66 degrees. I want 70/72 and this hasn’t been a problem in the past. I’ve tried moving the temp sensing probe into different positions with no joy.
The temperature adjusting knob also seems to have grown finicky where at the slightest touch it would ramp up the distribution blower or turn the blower off so I’m thinking ok the temperature control POT finally crapped out and got a dead spot. I ordered a new red supposedly long life POT and soldered it in. Before I installed it I checked it with an OHM meter and it seemed to work appropriately. It is a 100k POT. The old one would show open at different positions. So I thought I should be good to go.

I installed the board yesterday at about 72 degrees and it seemed to be working good but when I got home again this morning from work I was at 76 in the house.

I would really appreciate some help or hints. Thank you, Mark
 

SciGuy

Feeling the Heat
Aug 17, 2007
363
Constableville, NY
Hello folks, I’ve been a member for a while but mostly just lurking. I’ve had my P68 for about 13 years and I like to think I’ve become pretty familiar with them. I’ve replaced both blower motors and auger over the years.
This year I’ve been fighting an issue where I cannot get my house to a consistent temperature that I want. It seems to want to run and keep the house at 75/76 degrees or around 66 degrees. I want 70/72 and this hasn’t been a problem in the past. I’ve tried moving the temp sensing probe into different positions with no joy.
The temperature adjusting knob also seems to have grown finicky where at the slightest touch it would ramp up the distribution blower or turn the blower off so I’m thinking ok the temperature control POT finally crapped out and got a dead spot. I ordered a new red supposedly long life POT and soldered it in. Before I installed it I checked it with an OHM meter and it seemed to work appropriately. It is a 100k POT. The old one would show open at different positions. So I thought I should be good to go.

I installed the board yesterday at about 72 degrees and it seemed to be working good but when I got home again this morning from work I was at 76 in the house.

I would really appreciate some help or hints. Thank you, Mark

Hi Mark,

I suspect that you just misspoke but it's my understanding that the Room/Stove/off dial that adjusts the distribution blower speed rather than the temperature dial. Obviously the temperature dial will come to play with the distribution blower if heat is called for or the esp gets so warm the distribution blower is turned on to cool the stove down.

Just to clarify, did you change out the temperature pot or the Room/Stove/Off pot? Also, how about adding a picture of where your room temperature sensor is living? I love a good mystery:)

Thanks,

Hugh
 
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MarkDon

Member
Feb 22, 2015
24
NE pennsylvania
C13DE495-C48A-4610-8D7A-3739A16CB0AC.jpeg
Thanks. In haste, I wasn’t clear. I always run the stove in room temp mode with dial turned all the way to the right which should have the distribution blower fan on its highest speed. Yes, the temperature setting is the POT I replaced. Thanks for your reply, Mark
 

SciGuy

Feeling the Heat
Aug 17, 2007
363
Constableville, NY
View attachment 288104 Thanks. In haste, I wasn’t clear. I always run the stove in room temp mode with dial turned all the way to the right which should have the distribution blower fan on its highest speed. Yes, the temperature setting is the POT I replaced. Thanks for your reply, Mark

In the drafty cabin I live in, the stove would keep the place in the low eighties if the sensor was in that location with the temperature dial set on ~65. Perhaps your insulation is vastly better than mine but the sensing device in the cable is at the tip and it its cooler down by your baseboard than the main area of the room it will work to get the baseboard area to the set temperature. I know you mentioned moving its position but it certainly looks to be the likely culprit to me.

YMMV,

Hugh
 

MarkDon

Member
Feb 22, 2015
24
NE pennsylvania
Ok i will move the probe to a different spot and see what happens without adjusting the temp dial. I just woke up and it’s back to 67 here.
Please keep everyone’s thoughts coming. This one has me stumped.
 

SciGuy

Feeling the Heat
Aug 17, 2007
363
Constableville, NY
Ok i will move the probe to a different spot and see what happens without adjusting the temp dial. I just woke up and it’s back to 67 here.
Please keep everyone’s thoughts coming. This one has me stumped.

Is air circulation within the room different at different times of day? Perhaps there's a cool draft hitting the sensor with certain doors open or closed?
 

MarkDon

Member
Feb 22, 2015
24
NE pennsylvania
I have tried the probe against the outside wall to the right in my picture and that position is where the sun comes up in the morning and it does affect the stoves performance. I’ve had the probe coiled there for a couple of years without this issue. The only draft could be from the kitchen door about 15 feet away and with it being winter in NE Pennsylvania we don’t dally around with the door being opened longer than it needs to be. I had thought about checking the resistance in the temperature probe but as an easy check I held it close to the stove while it was running and it quickly slowed the stove down.
 

MarkDon

Member
Feb 22, 2015
24
NE pennsylvania
Well SciGuy, I moved the probe to the left hand side of the stove. It’s still close to an outside wall but the sun doesn’t hit that spot. It’s been holding at a nice 72 for about three hours now. I’m cautiously optimistic but this is similar to yesterday afternoon but then the temp rose overnight.
I’ll report back in the morning when I get home from work. Fingers crossed and I’m still open to any other suggestions incase this doesn’t pan out.
Thanks, Mark
Sorry about the dirty picture, ha. I would have wiped it down some if I knew the old girl was going to be on camera.
 
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SciGuy

Feeling the Heat
Aug 17, 2007
363
Constableville, NY
Well SciGuy, I moved the probe to the left hand side of the stove. It’s still close to an outside wall but the sun doesn’t hit that spot. It’s been holding at a nice 72 for about three hours now. I’m cautiously optimistic but this is similar to yesterday afternoon but then the temp rose overnight.
I’ll report back in the morning when I get home from work. Fingers crossed and I’m still open to any other suggestions incase this doesn’t pan out.
Thanks, Mark
Sorry about the dirty picture, ha. I would have wiped it down some if I knew the old girl was going to be on camera.

My fingers are crossed too;) When I checked the temperature next to my base board after my last post it was about 6*F cooler than where my temperature sensor is located projecting out from the mantle. I suspect the difference is even greater the colder it is outside.

My sensor is poking out a few inches from the mantle in the area circled in yellow and yes those are bare studs in the background;)

Sensor location.jpg
 

mtnbiker727

Feeling the Heat
Mar 11, 2019
262
PA
I'm in Northcentral PA. This year has been a little warmer during the day than most years, and nighttime temperatures are slightly above normal as well.

Today it was around 35 degrees as a high, but the sun shining in my office window was making me sweat. I rolled up my sleeves and cracked the window open. It's December 20th!

That said, I can see how the temperature probe touching the outside wall would be problematic. If the wall gets warm from the sun, the stove would idle down and cool the room down. When the wall gets cold over night, the stove would ramp up and make the room hot.

I keep my temp probe coiled up at the back of the stove, about a foot from the wall. I see you have a corner install, so that would be tough. Hopefully moving to the other wall that's not impacted by the sun will make the difference you need!
 

MarkDon

Member
Feb 22, 2015
24
NE pennsylvania
Well I came home this morning and my thermostat was sitting right at a nice 72! I’ve tried moving it around before without luck. Maybe I just always picked the wrong spot but I am very pleased right now. Thanks for all the help.
Mtbiker727, yeah this year has been warm for us as well. I’m used to the stove being finicky in the fall and spring, never before into December do I remember such a difference between daytime and nighttime temps. However I’ll take the warm days. Last week one day it was 60 here! I would like to get back to having the probe coiled like I had and like you said you use but right now I’ll have to wait for a few consecutive days off where I can monitor it and make adjustments. I’m from Wyoming county by the way. Almost 2 hours west of New Jersey.
Mark
 

MarkDon

Member
Feb 22, 2015
24
NE pennsylvania
I see there are some threads on here with that info. I think I might look into doing just that after some of these issues.
Thanks for the suggestion!
Mark
 

bogieb

Minister of Fire
Oct 31, 2014
3,092
South Central NH
I have 2 of these... fairly cheap.. and easy..
View attachment 288226
Dan

Putting both my pellet stoves on real thermostats were some of the best of the cheap-to-do ideas I've had.

The main floor stove is hooked to a thermostat in my office - which is about at the center point of my house. The basement stove got a dead spot in the pot dial so it was either keeping at 65* or 75* (or something like that) and I just wanted 70*. Installed a thermostat almost kitty-corner to the stove ( behind the stairway and closer to the the garage door) and works perfect.

I use Lux DMH110's - cheap and easy - note that I don't need programmable. I love the "Save" button - one press and it will lower (or raise) the set temp by 5*. Can be run by battery or wired.

LUX DMH110 Thermostat.JPG
 

Pete Zahria

Minister of Fire
Jan 6, 2014
1,234
New Hampster
mcmanusfuels.com
I see there are some threads on here with that info. I think I might look into doing just that after some of these issues.
Thanks for the suggestion!
Mark
It's pretty straight forward... You should give it a try..
The unit Bogie mentioned is a great one if you don't want to program
day/night or weekend settings.
You are just making a loop out of one side of the Harman probe, to go through
the new thermostat...
(you can use small wire nuts too... or solder.
I used these so I could go back if I ever wanted to)
Hope this helps..
Dan

harman_t_stat.JPG
 

mtnbiker727

Feeling the Heat
Mar 11, 2019
262
PA
Well I came home this morning and my thermostat was sitting right at a nice 72! I’ve tried moving it around before without luck. Maybe I just always picked the wrong spot but I am very pleased right now. Thanks for all the help.
Mtbiker727, yeah this year has been warm for us as well. I’m used to the stove being finicky in the fall and spring, never before into December do I remember such a difference between daytime and nighttime temps. However I’ll take the warm days. Last week one day it was 60 here! I would like to get back to having the probe coiled like I had and like you said you use but right now I’ll have to wait for a few consecutive days off where I can monitor it and make adjustments. I’m from Wyoming county by the way. Almost 2 hours west of New Jersey.
Mark
Lycoming County here. Not real far west of where you are, although there are no straight roads to get here from there!