Harman - room temp, blower stopping briefly

[movemaine]

With the cold temps, I've been cranking my stove (Harman Accentra) much more than usual...having it on full blast. Generally, I achieve it's max output by putting it in room temp at 75 degrees with the blower on high.

In the last few days, the distribution blower has been shutting down, and then coming back on. I haven't observed if the combustion blower is experiencing the same effect. However, if I put it in stove temp, then it doesn't seem to happen. I think the stove is shutting itself down more, based on pellet consumption. If I keep the stove in room temp and blast it all night long, it will burn through 2/3 of the hopper. The other night I came down in the morning, and only 1/3 of the pellets had been consumed.

Anyone have any insight or theories?

 

[Harman Lover 007]

Any chance your igniter switch is in the manual position?

 

[movemaine]

Any chance your igniter switch is in the manual position?

Just double checked; it's in the auto position.

 

[Harman Lover 007]

Just double checked; it's in the auto position.

Hmmmm.......if it doesn't do it in ST mode, that's perplexing. Sounds thermal in some way.....
The next time it does it, grab the knob and see if you can start the fan back up by wiggling it. Maybe the very beginning of a dirty or failing "pot"?

 

[movemaine]

Hmmmm.......if it doesn't do it in ST mode, that's perplexing. Sounds thermal in some way.....
The next time it does it, grab the knob and see if you can start the fan back up by wiggling it. Maybe the very beginning of a dirty or failing "pot"?

Which knob? the room temp knob?

 

[Harman Lover 007]

Which knob? the room temp knob?

Yes, sorry. The knob that controls the fan speed. It's the same knob for RT or ST, its just a matter of where you turn it. (but you know that)

 

[jackman]

It sounds like the fan speed potentiometer has the dead spot problem. I call it a ratty pot. Its a common problem with the Harman board. You can do a search in the forums for potentiometer and read all about it. If you're handy with a soldering iron you can replace the pot yourself for about $10. A replacement board will be lots more.

 

[swalz]

Mine was doing the same thing, if you moved the nob a little it would start back up or go off. I replaced the potentiometers last month and it resolved the issue.

 

[railfanron]

I think what you're seeing is normal. My stove in room temp mode will do the same thing if I set it at 70 when it's real cold out. I think what you're seeing is the stove coming up to temp and ramping down. Once it gets to the low fire or close to shutoff the convection fan will go off, but by then the temp sensor is calling for heat and the stove starts ramping back up and the fan starts again. If I set mine to 65 or a little lower it shuts off for awhile and then starts back up. If I set it to 77 or so the blower will stay on as the stove has less time in idle mode. When it's very cold out the convection currents in the house are much more aggressive as heat and cold air love to come together so the room sensor will sense the cold air possibly before you do. My stove has been on 70 for the last month and I can almost tell you what the temperature is outside by the length of time between stops and stats of the blower. Tonight is 20 degrees warmer the last night and the blower off length of time is a lot longer than last night. Last night was never more than a minute (-10 with 20 mph wind).
Ron

 

[Harman Lover 007]

I think what you're seeing is normal. My stove in room temp mode will do the same thing if I set it at 70 when it's real cold out. I think what you're seeing is the stove coming up to temp and ramping down. Once it gets to the low fire or close to shutoff the convection fan will go off, but by then the temp sensor is calling for heat and the stove starts ramping back up and the fan starts again. If I set mine to 65 or a little lower it shuts off for awhile and then starts back up. If I set it to 77 or so the blower will stay on as the stove has less time in idle mode. When it's very cold out the convection currents in the house are much more aggressive as heat and cold air love to come together so the room sensor will sense the cold air possibly before you do. My stove has been on 70 for the last month and I can almost tell you what the temperature is outside by the length of time between stops and stats of the blower. Tonight is 20 degrees warmer the last night and the blower off length of time is a lot longer than last night. Last night was never more than a minute (-10 with 20 mph wind).
Ron

Ron,
What you describe above is exactly how the stove should operate when in RT mode with the igniter switch in the MANUAL position. This is how I run my stove in the coldest part of the season. The OP, Movemaine, has this occurring with his switch in AUTO and the distribution fan should not be ramping up and down with the switch in this position. It is not normal.

 

[railfanron]

Harman Lover I'm far from an expert on this stuff but consider this. I run my stove in room temp manual as well when it's cold outside because I had exactly what Movemaine described happen to me when it got really cold outside. Think about this, in room temp automatic the thermostat has reached the required temperature and the stove goes into shut down. Shut down progresses until the fire is out and the combustion fan is still running BUT the convection fan has shut off because the outside air has cooled the stove quickly. Then because of bitter temperatures and a possible cold draft circulating close to the temperature pickup the stove now calls for heat thus going into startup mode. There are enough coals to ignite the burn quickly and the a minute later the fire is up and burning enough to trigger the combustion fan. In the right conditions this can all happen in a couple of minutes. So the series goes like this, shut down then startup blower off for a couple of minutes a few minutes later heat is satisfied and the same thing happens all over again. I know this happens because it has happened to me when it got down in the -20 degree territory with the room temp at 70 in auto mode. When it is warm out things work pretty well in auto (stove off for 15 minutes to a half hour then another cycle. This is heating 2250 sq ft, 825 to 71 and the rest to 65. The idea of the igniter firing maybe 6 time an hour got me to move to room temp manual in all but the warmest days.
Ron

 

[Harman Lover 007]

Harman Lover I'm far from an expert on this stuff but consider this. I run my stove in room temp manual as well when it's cold outside because I had exactly what Movemaine described happen to me when it got really cold outside. Think about this, in room temp automatic the thermostat has reached the required temperature and the stove goes into shut down. Shut down progresses until the fire is out and the combustion fan is still running BUT the convection fan has shut off because the outside air has cooled the stove quickly. Then because of bitter temperatures and a possible cold draft circulating close to the temperature pickup the stove now calls for heat thus going into startup mode. There are enough coals to ignite the burn quickly and the a minute later the fire is up and burning enough to trigger the combustion fan. In the right conditions this can all happen in a couple of minutes. So the series goes like this, shut down then startup blower off for a couple of minutes a few minutes later heat is satisfied and the same thing happens all over again. I know this happens because it has happened to me when it got down in the -20 degree territory with the room temp at 70 in auto mode. When it is warm out things work pretty well in auto (stove off for 15 minutes to a half hour then another cycle. This is heating 2250 sq ft, 825 to 71 and the rest to 65. The idea of the igniter firing maybe 6 time an hour got me to move to room temp manual in all but the warmest days.
Ron

What you describe is normal. I don't believe movemaine was describing the same thing.

 

[movemaine]

Harman Lover I'm far from an expert on this stuff but consider this. I run my stove in room temp manual as well when it's cold outside because I had exactly what Movemaine described happen to me when it got really cold outside. Think about this, in room temp automatic the thermostat has reached the required temperature and the stove goes into shut down. Shut down progresses until the fire is out and the combustion fan is still running BUT the convection fan has shut off because the outside air has cooled the stove quickly. Then because of bitter temperatures and a possible cold draft circulating close to the temperature pickup the stove now calls for heat thus going into startup mode. There are enough coals to ignite the burn quickly and the a minute later the fire is up and burning enough to trigger the combustion fan. In the right conditions this can all happen in a couple of minutes. So the series goes like this, shut down then startup blower off for a couple of minutes a few minutes later heat is satisfied and the same thing happens all over again. I know this happens because it has happened to me when it got down in the -20 degree territory with the room temp at 70 in auto mode. When it is warm out things work pretty well in auto (stove off for 15 minutes to a half hour then another cycle. This is heating 2250 sq ft, 825 to 71 and the rest to 65. The idea of the igniter firing maybe 6 time an hour got me to move to room temp manual in all but the warmest days.
Ron

No, this isn't what's happening. In Maine it's consistently been running colder than average temps, and the stove has kept up without issue. This is a new behavior where there's a sudden die down and a quick ramp back up. The blower is not shutting down due to reaching temp (as it never reaches the setting I have it at).

 

[movemaine]

Ok, as I was sitting here it just happened on Stove Temp mode. Blower stopped for 2 seconds, and then immediately came back on.