Harman PF100 Settings

[Ejectr]

I have my furnace on "auto light". I've been told that a small fire continues to burn for 45 minutes. If no call for heat is seen in that time, it goes out. In that 45 minutes, the small fire heats the fan controller and when it gets hot enough, it starts the blower, dissipating the heat and stops when the controller gets cool enough. This goes on and off for 45 minutes unless the thermostat calls for heat.

My blower fan seems to run an awful lot while the thermostat is satisfied according to a digital thermometer I have in the same room. How can the thermostat get to the point where it needs heat if this small fire burns for 45 minutes, and the fan turns on and off within that time dissipating the heat. Seems to me it's going to burn this small fire for 45 minutes and constantly satisfy the thermostat in that time period.

I have my feedrate set to 4 and the settings on the fan controller are according to the book. The Harman book leaves a lot to be desired as far as operational information goes.

Is this normal or do I need to tweak an adjustment?

Thanks.

 

[Labrat]

It's normal. The small fire is there to satisfy the ESP probe and allow the furnace to cool down slowly and not cause damage to the unit. The distribution fan turning off and on is also part of that process.

 

[DexterDay]

Can you set the temp where the fan can kick on and off? My Fahrenheit has an ajustment where I can set the on temp 160* (up to 200*) and the off temp 90* (as low as 75* or 80*, I think, not looking at it).

Its a round stat that allows the user to control the temp of air in which the blower turns on and off. By raising the lower temp, this would cause the furnace to have to run longer without kicking on (especially under a low fire condition). Dont know if Harmans have that capability? But if my cheaper unit has it? Yours may... I dont know??

 

[Ejectr]

Yes, it does have a fan control unit. I knew I could change the on off temps. Just don't know if I should.

 

[exoilburner]

Check the adjustment on your FAN/HI LIMIT CONTROL mounted on the hot air sheet metal duct. It is located 11 inches above your furnace. This switch controls the distribution fan as the hot air duct temperature heats and cools. It should be located 11 inches above your furnace on the hot air duct. If it is not 11 inches that may affect it's adjustment too.
It also has a second adjustment that sets the point your PF100 shuts down when the duct temperature overheats, so it is a very important safety adjustment. You may want to have a trained certified furnace tech. check these 2 adjustments. As you know this is a furnace not a stove. This component is a standard oil furnace component.

You can verify this information by looking at the PF100 electrical schematic.

Here is the adjustments in the Harman manual pg 19.
9. HIGH LIMIT setup is simple, just rotate the high limit
pointer clockwise until it is against the tamper-proof
screw. (Never adjust this screw)
10. FAN CONTROL setup: Move both fan control pointers
together until they touch, then rotate both pointers
together until the gap between them is directly over the
middle 0 of 100. See Fig 36.
Note: This is the best fan control position we have
found during factory testing. These fan control settings
can be adjusted if desired.

 

[Ejectr]

Check the adjustment on your FAN/HI LIMIT CONTROL mounted on the hot air sheet metal duct. It is located 11 inches above your furnace. This switch controls the distribution fan as the hot air duct temperature heats and cools. It should be located 11 inches above your furnace on the hot air duct. If it is not 11 inches that may affect it's adjustment too.
It also has a second adjustment that sets the point your PF100 shuts down when the duct temperature overheats, so it is a very important safety adjustment. You may want to have a trained certified furnace tech. check these 2 adjustments. As you know this is a furnace not a stove. This component is a standard oil furnace component.

You can verify this information by looking at the PF100 electrical schematic.

Here is the adjustments in the Harman manual pg 19.
9. HIGH LIMIT setup is simple, just rotate the high limit
pointer clockwise until it is against the tamper-proof
screw. (Never adjust this screw)
10. FAN CONTROL setup: Move both fan control pointers
together until they touch, then rotate both pointers
together until the gap between them is directly over the
middle 0 of 100. See Fig 36.
Note: This is the best fan control position we have
found during factory testing. These fan control settings
can be adjusted if desired.

I could not mount my fan control 11" from the top of the furnace. With the need to put in a back draft damper and a low ceiling, I didn't have the room. It was mounted as high as possible, but nowhere near 11".

I did set it up according to these instructions in the install manual. Just don't know if they're right for me seeing my fan control is mounted lower than 11".

 

[exoilburner]

I don't know how much closer you installed it on the duct or what the effect would be. I think it would be worth paying a certified furnace tech to tell you how to set it correctly with the Harman requirements. The furnace esp (probe) sits directly above the heat exchangers; I don't know how much affect the distribution fan has on the ESP when it pulls heat off the heat exchangers.
But the bigger issue is how safe is your high limit setting for your duct overheating. I would want to be sure that was set correctly. Probably a certified HVAC tech could check it out and give you the correct adjustments so you could adjust it later yourself.

 

[Ejectr]

I did not install it myself. It was installed by a certified HVAC guy and the settings were set according to the directions in the Harman installation manual. So it's already been checked by a certified tech.