Chasing Temps

[Ejectr]

First of all Merry Christmas to all, whatever your beliefs might be,

I re -read my original post and realized how stupid it could sound, so I'm just going to ask a PF100 owner to please explain to me when the feedrate adjust comes in to play. I know it increases or decreases the auger on time therefore affecting the supply of pellets to the burn pot, but when. Is it after the ESP and the board takes over?

 

[Ejectr]

My distribution fan seems to be running non stop. It does stop once in awhile very briefly. The thermostat seems to be satisfied for all I can tell comparing it to a digital thermometer and the furnace is in slow burn with feedrate adjust set to 4.

When the install was done, I was unable to get 11" clearance to the fan control because of a low ceiling, existing duct work and the need to put a back flow damper on the vertical duct riser coming out of the furnace.

Should I boost the temp of the fan control turn on or off or try turning the feedrate to 3? It's not really been that cold here. I think I should have seen the furnace shut itself down instead of the distributor fan running all the time. What good is it going to do to heat with pellets if the electric bill goes up because the fan runs non stop?

Any help or suggestions will be appreciated.

 

[archie79]

Theoretically speaking. Say your thermostat is set to 70. If your temp is holding a steady 70 degrees then everything is working fine. If the temp is warmer than your setting then there is probably something up with the fan control. If, however the temp is correct and the blower motor is running to frequent for your taste then upping the feed rate will make the temP of the air comming out of the furnance hotter thus making the blower fan not run as frequently.

 

[archie79]

P.s if you are thinking the blower is running to much to keep the fire box cool, then the temp in your house would be higher then the setting on thermostat. Also most of the blower motors are a small drain on the electric bill, but nothing like the cost of fuel oil, propane, natural gas, kerosene, or heating with a heat pump, or any other type of electric heat. Unless your house is insulated extremely well.

 

[Ejectr]

Theoretically speaking. Say your thermostat is set to 70. If your temp is holding a steady 70 degrees then everything is working fine. If the temp is warmer than your setting then there is probably something up with the fan control. If, however the temp is correct and the blower motor is running to frequent for your taste then upping the feed rate will make the temp of the air coming out of the furnace hotter thus making the blower fan not run as frequently.

I do have it set to 70 and it is holding that temp. If I increase the feed rate and make it hotter, wouldn't that make the fan control even hotter and want to run more to get it to the set off temperature on the fan controller? Or would that satisfy the thermostat sooner and shut down the furnace. I'm still trying to figure out the modus operendus of this PF100. Would have been nice if Harman included a description on theory of operation in their manual instead of " trust me....it works".

 

[archie79]

Ok you can set your limit switch from automatic to manual, when the switch gets to warm it switches automatically. If that is the case then you could always try lowering the feed rate to see if that will work. If your going that rout, may I suggest turnig the feed rate to 1, and seeing if that holds the correct temp in your house. I think starting at the bottom and working up is easier anyways. If its any help, I have a 1300 square foot house, and the temps have been in the mid to upper 30s at night and between the mid. 40s and low 50s during the day. My feed rate is set to number 1, and would be set lower if there was one lower. Hope that helps

 

[Ejectr]

I tried once before setting the feed adjust to 1 and the furnace went out. Went out set to 2 as well. I set it back to 4 and didn't try 3. My first floor that I am heating is probably around the 1300 sq ft size. Our temps have been variable at high 30's to 40 daytime, high teens to 20's at night. Today a warm one at 47 expected high and 39 low for the night.

 

[archie79]

So how high we're you able to mount your fan switch?

 

[Ejectr]

From te top of the furnace, onl about 6".

 

[archie79]

Hmm, I still have to wonder if your low draft is set correctly. Tell you what. See if you can take a thermometer and try to put it next to your fan limit switch and record the temp after the furnance has been running awhile. Try to set it up in a way that doesn't let Alot of air escape. I know that when I had my feed rate set to 4 it was really close to engaging the limit switch and it was nearly 150 degrees.

 

[Ejectr]

Hmm, I still have to wonder if your low draft is set correctly. Tell you what. See if you can take a thermometer and try to put it next to your fan limit switch and record the temp after the furnance has been running awhile. Try to set it up in a way that doesn't let Alot of air escape. I know that when I had my feed rate set to 4 it was really close to engaging the limit switch and it was nearly 150 degrees.

The installer set it to the best he could get. What limit switch was it in sanger of engaging? The upper limit?

 

[archie79]

Yeah the air comming out of the furnace was almost to hot. All I had to do was barley touch the switch and it jumped to the manual position, and when I tried setting it back to auto I had to do it very gingerly or it would just fall back to the manual positon

 

[Ejectr]

Wow....I'm starting to wonder if your furnace board is out of whack. With heating your house on 1 and in danger of tripping the limit on 4, that sounds kind of obverse. Are you running in manual or automatic off the thermostat? I'm off the thermostat.

 

[archie79]

Yeah I guess something would be out of wack had my burn pot not been full and just tipping ash out into the pan. This furnace is kinda complicated for the average user. It's probably why Harmon doesn't put out detailed info on the everday usage of the product. If they said that Alot of the settings is dependent upon each individual circumstance and takes Alot of tinkering to get it to work the best it can,then they probably wouldn't sale Alot of them. Actually I am currently designing a new circuit board for my furnace. I already see several things that could streamline the efficiently of the furnace. I'm thinking of adding themometer to the firebox and having those readings determine the feed rate. I just don't have enough data to get the details right. I think the process of going into a minimum burn until the tenpins 1 degree higher then the thermostat setting could be improved upon. When I get the time to take the notes needed and do my experiments I'll post my findings.

 

[Ejectr]

That will be interesting. I also have an electronics background. I had an HS Tharm wood/coal boiler once. I knew that thing like the back of my hand but it was all analog. No circuit boards, just temp sensors, relays, solenoid valves and circulators. I could run that thing in my sleep.

 

[wil lanfear]

Wow....I'm starting to wonder if your furnace board is out of whack. With heating your house on 1 and in danger of tripping the limit on 4

X2, my guess is that the control potentiometer for the pellet feed is faulty, feeding excessive amounts of pellets on the lower setting.

 

[archie79]

Wil, I actually considered that myself, but I noticed that with the feed rate on 1 my Burn pot is only half full, and when it's on 4 the burn pot is full. I also noted that i have the newest model. It makes me wonder if Harmon is playing around with the system? I mean we both have obvoiously both pith Alot of thought and research in the mater. It wouldn't be the first time a company pulled a switcharoo. Any thoughts on that?

 

[Ejectr]

Sent Harman Customer Service an email on all this and this is their reply:

It is true about the feed settings being based on a 60 second timer. It will only run on the feed setting on the control when there is a demand for heat. When there is no demand for heat it will slow the feed down to a 5-7 second per minute cycle. If the if the temperature demand stays satisfied in this cycle, it will shut the unit down.

 

[Ejectr]

Wil, I actually considered that myself, but I noticed that with the feed rate on 1 my Burn pot is only half full, and when it's on 4 the burn pot is full. I also noted that i have the newest model. It makes me wonder if Harmon is playing around with the system? I mean we both have obvoiously both pith Alot of thought and research in the mater. It wouldn't be the first time a company pulled a switcharoo. Any thoughts on that?

My burn pot is about half full running on 4...

 

[archie79]

hmm, that is something to test, when i get a chance ill pull the circuit board out of there and see if i can get the specks on the rheostat. Before i had nothing to compare it to so i figured that since the furnace charged more pellets with the feed rate set to a higher setting, and less pellets with it set to a lower setting it was working correctly. Thanks for the heads up. (I hate math, but sometimes it does pay to do it anyways... lol)

 

[wil lanfear]

Wil, I actually considered that myself, but I noticed that with the feed rate on 1 my Burn pot is only half full, and when it's on 4 the burn pot is full. I also noted that i have the newest model. It makes me wonder if Harmon is playing around with the system? I mean we both have obvoiously both pith Alot of thought and research in the mater. It wouldn't be the first time a company pulled a switcharoo. Any thoughts on that?

First, let me mention that the length of pellets being used has a direct impact on how many pellets are fed at a given feed setting. I can only speak to my boiler feed setting, which I run on setting 5.5. If I were to set it on setting 1 or 2, my guess it would fail to stay burning, I have set it on 4 back when I first installed the boiler but soon found that this setting created a low burning flame that burned more pellets. If your burnpot is half full on setting 1, this shouldn't be, doesn't give you much of a feed adjustment for using a different brand pellet. I still stand by my thought that the control board has an issue with the feed rate.

 

[wil lanfear]

hmm, that is something to test, when i get a chance ill pull the circuit board out of there and see if i can get the specks on the rheostat. Before i had nothing to compare it to so i figured that since the furnace charged more pellets with the feed rate set to a higher setting, and less pellets with it set to a lower setting it was working correctly. Thanks for the heads up. (I hate math, but sometimes it does pay to do it anyways... lol)

These are the ones for my control board.

http://www.ebay.com/itm/3-Harman-Pe...838?pt=LH_DefaultDomain_0&hash=item27c192574e

 

[Ejectr]

Was in the mid teens last night and I had my thermostat set to 70. The digital along side it said 68 in the room. I had a pretty substantial fire going in the burn pot. I don't think I'd consider it slow burn. I figured I'd raise the feedrate adjust to get more heat out of the furnace. I adjusted it from 4 to 6 and timed the auger feed light. I got 24 seconds on...36 seconds off. I set it back to 4 and timed it again. Same thing. I set it to 2 and got the same thing. No setting on the board changed the time of the auger on and I'm still not hitting the set point on my thermostat.

So...I'm confused.

 

[archie79]

Me too, one of us has a faulty board, or Harmon has changed something. My furnace will change the feed rate as soon as you change it. But yOurs sounds like everyones else who says its mostly controlled by the board anyways.?? Oh well, just find something that works well for you and go with it

 

[Ejectr]

I've been in communication via email with Harman. This is what they told me:

(ME) It was in the mid teens last night and I had my thermostat set to 70. The digital along side it said 68 in the room. I had a pretty substantial fire going in the burn pot on what was obviously a demand for heat from the thermostat. I don’t think I’d consider it slow burn. I figured I’d raise the feedrate adjust to get more heat out of the furnace. I adjusted it from 4 to 6 and timed the auger feed light. I got 24 seconds on…36 seconds off. I set it back to 4 and timed it again. Same thing. I set it to 2 and got the same thing. No setting on the board changed the time of the auger on and I’m still not hitting the set point on my thermostat. It is solid at 68 while my thermostat is set at 70.

(Harman) Raising the feed rate will not increase the heat output of the furnace. If the pf100 wall control is set at 70 and your digital t-stat is reading 68, it is not going to create a demand for heat. Try adjusting the temp control dial higher to increase the heat output of the furnace in order to have it match the reading on your digital t-stat. If you have the temp control on circuit board set to normal setting, increase it to the #5 position.

As far as the on and off time of your feed motor, it will not feed to the maximum of 40 seconds out of 60 unless it has to in order to meet the demand. That adjuster is actually a limiter also. When you set this, you are limiting the amount of time it can feed when it has to. In the #4 setting, or any other setting, it may only feed 24 out of 60 seconds if there isn’t a great demand for heat. It operates this way to avoid over shooting the set temperature.