I have a three year old PF100. I have it set in automatic with a feed rate at about 4 and am burning the same Marth brand of pellets as last year. Lately the fire in the burn pot will not go out, no matter what I have the thermostat set at. It continues to run a small fire and feed pellets (at a reduced rate) all of the time, just like when it is set to run in manual. When I shut the stove down and restart it the initial burn and ignition work exactly like it did before I started having issues. But for the life of me I can not get it to shut the fire down when we are not calling for heat. I recently cleaned the whole thing including the probe and nothing changed. Any ideas?
PF 100 in automatic acts like it is in manual
- Thread starter bradydad95
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Ejectr
Minister of Fire
Just saw your post. Mine does the same thing. Runs all the time like it's in manual but maintains the temp setting of 70 I have on the thermostat. Never see it hit 71 and shut off. I've asked a million questions about this furnace. Even to Harman. I don't think even they understand how it runs in automatic mode. Seems to be several definitions out there how the feedrat adjust works and when the board takes over.
You'd figure it would work like an oil furnace. The thermostat calls for heat, the burner comes on and heats the plenum. The fan controller kicks in heating the house. The thermostat gets satisfied and the burner shuts down. The planum cools down and the fan shuts off. Don't know why this thing keeps feeding a small fire all the time and the freeking temp never goes above 70. I guess Harman decided to make something easy complicated.
You'd figure it would work like an oil furnace. The thermostat calls for heat, the burner comes on and heats the plenum. The fan controller kicks in heating the house. The thermostat gets satisfied and the burner shuts down. The planum cools down and the fan shuts off. Don't know why this thing keeps feeding a small fire all the time and the freeking temp never goes above 70. I guess Harman decided to make something easy complicated.
Hello Ejectr. I have a PF100 and am in my third season with it. Generally, it has been great. When first installed it had a bad blower motor and it took a long time to figure out the problem. But I bought a replacement from Grainger for about $150 (it's the three speed motor) and it works great. I had to replace the igniter last season, which really surprised me. Now, I noticed that it is not always feeding pellets even when the red "Feed Motor" light is on. I traced the wiring for the auger feed motor and tapped on the low pressure switch/differential pressure switch and that seems to have improved the feed, though not entirely. I may replace that switch as it's only about $30.
During the installation process (I installed it myself) I had some correspondence with one of the engineers at Harman regarding the thermostat. He finally told me that I could wire a regular digital setback thermostat in series with the Harman thermostat. It has been working well with that setup. In the process of working this out with Harman I learned a lot about how the system works.
A typical furnace, oil or gas fired, is either on or off, and the typical thermostat is basically an on/off switch with adjustable "on" and "off" points. When the temperature falls below the setpoint on the thermostat the furnace is turned on. The furnace immedately fires up at full force. Once the supply plenum gets up to the preset temp, roughly 150 deg F, the blower will start and distribute warm air through the duct system. When the selected temp is reached at the thermostat, the furnace is trurned off, meaning that the flame is immediately extinguished. The blower continues to run until the preset temp for the supply plenum is reached, and then the blower turns off.
However, a pellet or any other wood fueled furnace works differently. The wall thermostat is not an on and off switch. Rather, it is a thermistor, which is a precision temperature sensitive resistor. As the temperature varies, the value of the resistor directly proportional to the temperature. This is part of the electronic circuit board controller mounted on the side of the PF100. Essentially, as the temperature at the wall thermostat ("wall control") approaches the set temperature, the resistance varies, and the controller slowly reduces the feed rate of the pellets, thereby reducing the fire, but NOT extinguishing it. This maintains a much more even temperature in the house, though it does keep the blower running most of the time. In my particular situation, this is big plus as it a large, drafty, very old house. With the oil furnace running we always have cold spots, but the PF100 keeps it much more comfortable. And the blower, though audible, is much quieter than the blower on our oil furnace.
Our PF100 is installed alongside our oil furnace. Either furnace can be operated. The wiring is set up so that only one can be operated at any time. There are four 'shutters' installed in the ductwork. Two of them must be open and two closed depending on which furnace is operating. This greatly improves the efficiency, by only allowing airflow to one furnace. If anyone is interested in more details on this set up, let me know and I can correspond off line.
Doug
During the installation process (I installed it myself) I had some correspondence with one of the engineers at Harman regarding the thermostat. He finally told me that I could wire a regular digital setback thermostat in series with the Harman thermostat. It has been working well with that setup. In the process of working this out with Harman I learned a lot about how the system works.
A typical furnace, oil or gas fired, is either on or off, and the typical thermostat is basically an on/off switch with adjustable "on" and "off" points. When the temperature falls below the setpoint on the thermostat the furnace is turned on. The furnace immedately fires up at full force. Once the supply plenum gets up to the preset temp, roughly 150 deg F, the blower will start and distribute warm air through the duct system. When the selected temp is reached at the thermostat, the furnace is trurned off, meaning that the flame is immediately extinguished. The blower continues to run until the preset temp for the supply plenum is reached, and then the blower turns off.
However, a pellet or any other wood fueled furnace works differently. The wall thermostat is not an on and off switch. Rather, it is a thermistor, which is a precision temperature sensitive resistor. As the temperature varies, the value of the resistor directly proportional to the temperature. This is part of the electronic circuit board controller mounted on the side of the PF100. Essentially, as the temperature at the wall thermostat ("wall control") approaches the set temperature, the resistance varies, and the controller slowly reduces the feed rate of the pellets, thereby reducing the fire, but NOT extinguishing it. This maintains a much more even temperature in the house, though it does keep the blower running most of the time. In my particular situation, this is big plus as it a large, drafty, very old house. With the oil furnace running we always have cold spots, but the PF100 keeps it much more comfortable. And the blower, though audible, is much quieter than the blower on our oil furnace.
Our PF100 is installed alongside our oil furnace. Either furnace can be operated. The wiring is set up so that only one can be operated at any time. There are four 'shutters' installed in the ductwork. Two of them must be open and two closed depending on which furnace is operating. This greatly improves the efficiency, by only allowing airflow to one furnace. If anyone is interested in more details on this set up, let me know and I can correspond off line.
Doug
Ejectr
Minister of Fire
Well Doug.....that is the best explanation I've gotten yet of how the PF100 works and I believe explains why there is always a fire in the burn pot that never seems to go out. I have a few more questions and will send you an email. Thanks for taking the time to repond to my post.
I have the PF100 and I run it mostly in manual except for the start and end of season and during times that it's warm enough out that the manual will be too warm.
When in Auto, I do see that my fire will go out if there is a good period of time that I hit my temp and it has not called for more heat.
When in Auto, I do see that my fire will go out if there is a good period of time that I hit my temp and it has not called for more heat.
Ejectr
Minister of Fire
I called Harman this morning and discussed my issue. It was time well spent. It appears that the fire always being in the burn pot is what it should be doing. I guess my heat loss is about equal to what I'm putting out for heat at 70 degrees so the furnace is just keeping pace. He asked me a bunch of questions and we eliminated the possibility of a faulty wall controller (their thermostat) or a bad board. It appears the feed rate adjust setting is only effective when there is a large call for heat. It goes off of that setting. If the feed rate is set too low, it will limit the output of the furnace and its ability to heat your house and reach the set point at all. It acts more as a limiter than anything else. Once the set point is hit, the board takes over and feeds at a rate it determines will satisfy the ESP. If your house is tight and the minimum burn that the board controls further heats the house and you reach 1 degree above the set point for a period of time, the furnace will shut down and will not reignite until the ambient has dropped 3 degrees from the wall controller setting.
He also told me that the advice to loosen the set screw and adjust the wall controller knob to match what one might read on a digital thermometer or thermostat is erroneous advice. He said that the "normal" position on the temp knob when the furnace is in automatic is a starting point. It is not the gospel setting. He said that the whole range of the temp knob is effective in automatic and will increase or decrease the temperature of the furnace. If the wall controller is set to 70 and your digital thermometer says 68, them you increase the temp knob off of "normal" until the room temp matches the wall controller setting.
I now understand this furnace a lot better than I did before I called them and the gentleman at Harman was extremely helpful and couldn't have been nicer.
He also told me that the advice to loosen the set screw and adjust the wall controller knob to match what one might read on a digital thermometer or thermostat is erroneous advice. He said that the "normal" position on the temp knob when the furnace is in automatic is a starting point. It is not the gospel setting. He said that the whole range of the temp knob is effective in automatic and will increase or decrease the temperature of the furnace. If the wall controller is set to 70 and your digital thermometer says 68, them you increase the temp knob off of "normal" until the room temp matches the wall controller setting.
I now understand this furnace a lot better than I did before I called them and the gentleman at Harman was extremely helpful and couldn't have been nicer.
76brian
Feeling the Heat
Ejectr
Minister of Fire
Somebody correct me if I'm wrong...but I think it's 45min with no call for heat before it will shut down completely. Sounds like you might be getting a call for heat but a fire just barely above your minimum burn rate is able to keep up with it.
Ejectr
Minister of Fire
That may be.. I'm all done obsessing over it. It is what it is I guess, Just as long as there is nothing wrong, I'll just sit back, let it do its thing and enjoy the heat.FOTONATE said:
Thanks everyone.
propanevictim
Member
Diggypif,
Funny you should mention that issue with the feed motor. I think I'm in my 5th season with the PF100, and only in the last three weeks have I had the same issue with the feed motor. I noticed first that the flame would cycle up and then far down. Then noticed that the feed motor light came on, but no feed motor--or not consistently enough to maintain desired temperature. Dealer came and diagnosed a bad pressure switch--$30. He put it in two days ago, started the unit up. Not 2 hours after he left, the unit shut itself down with 6 blink status. I cleaned and scraped, started it up, again it shut itself down with a 6 blink status. And wouldn't you know it, the feed motor is still not working. No response from my dealer yet. Any ideas? Maybe it's the Northern New Jersey air?
Funny you should mention that issue with the feed motor. I think I'm in my 5th season with the PF100, and only in the last three weeks have I had the same issue with the feed motor. I noticed first that the flame would cycle up and then far down. Then noticed that the feed motor light came on, but no feed motor--or not consistently enough to maintain desired temperature. Dealer came and diagnosed a bad pressure switch--$30. He put it in two days ago, started the unit up. Not 2 hours after he left, the unit shut itself down with 6 blink status. I cleaned and scraped, started it up, again it shut itself down with a 6 blink status. And wouldn't you know it, the feed motor is still not working. No response from my dealer yet. Any ideas? Maybe it's the Northern New Jersey air?
I finally got around to giving mine a good cleaning this weekend and that took care of most of my problems. The furnace still kept a fire going for a couple of hours after i had turned the temp way down. I realized that i had forgotten to clean my temp probe. once i cleaned that off it is working like it used to. People are right when they say on here that a good cleaning will cure most of your problems. they were right for me anyway.
Great info on the operation of the Harman furnace. Idling of the fire during brief periods of no heat demand is similar to what users of coal central heating systems experience. Normally in the coal fired heaters the fire never goes out due to the difficulty of restart. Those who use coal to heat domestic hot water increase the idle time during the summer in an effort to try to find the sweet spot that achieves a balance between coal usage and maintaining a flame. I just picked up a PB 105 Saturday and hope to complete a remote install this weekend. The info in this thread clears up a number of questions I had on how the Harmon controls work.
wil lanfear
Feeling the Heat
The PB 105, with the switch position in auto, it will shut down when the high limit setting is satisfied, it will refire with the low limit setting. If you desire that you want a continuous fire, position the switch in manual but........ you will need a "dump loop" in case of a overheat situation. I would suggest that you have a "dump loop" whether you run in manual or not. I have my aux. output (overheat zone) 120 volt wires connected to a 24 volt transformer. If I have a overheat situation, the transformer sends 24 volts to a relay which closes powering the circulator and fan on the unit heater in my workshop.katman said:
Ejectr
Minister of Fire
When you say "high limit "and "low limit", you are talking about the setting on the aquastat....correct? A little different than the high and low setting on the fan control on a hot air system. I used to have an HS Tharm wood/coal/oil furnace and I understood that thing like the back of my hand. I had a dump zone set up when I got to 200 degrees on the boiler temp measured off a seperate sensor than the aquastat. I loved hot water heat. Made sense. This hot air stuff....not so much.wil said:
wil lanfear
Feeling the Heat
wil lanfear
Feeling the Heat
The brand name is Young, it was given to me quite a few years ago from a place I used to work. The coil measures 14" w X 16" high. Any hot water unit heater would work, they are a tad bit spendy though. A couple 8 ft. pieces of radiation would work as a dump loop along with a circulator,transformer and a relay, less expensive than a unit heater.katman said:
http://www.pexsupply.com/Base-Line-2000-Baseboard-Heaters-796000
Ejectr
Minister of Fire
wil said:
One place I lived that had an HS Tharm boiler used a big ol' cast iron radiator like the ones used in a steam heat system to feed the dump zone to. Also had a thermostat in the cellar and the cast iron radiator hooked to a zone so if the house was closed up for the winter, the cellar could be heated to keep the pipes from freezing along with an anti freeze in the boiler water. That big cast iron radiator heated that cellar with no problem.
wil lanfear
Feeling the Heat
A cast iron radiator would work perfect as a dump loop, I wish I had saved some that I removed over the years.Ejectr said:
I like the cast radiator option but around here they have become very desirable so the baseboard might be the short-term option. I like the suspension heaters but they would bust the project budget. I'm a little skeptical of the mode where boiler operation is controlled in part by the outdoor air sensor. If my reading of the manual is correct it is calibrated to 0 degrees with a max dropping one degree for every degree above zero. That would give me a fairly narrow hi/lo range for most of the heating season here in annapolis, md. so I will probably try to operate without the sensor.
wil lanfear
Feeling the Heat
I used the outside sensor the first heating season I installed the boiler, haven't used it since, the reason being that I use the boiler for my DHW needs.
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