A question about draft readings on a Harman PF100 furnace

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ex-oil slave

New Member
Oct 2, 2008
45
NW Ontario, Canada
When I installed this furnace (new) the manual suggested using a manometer to check the draft readings at the firebox at both high and low speed combustion fan settings. I got .72 inches at high speed and between .39 and .45 inches at low speed. The low speed reading was a little higher than it should have been (.25) but was within usable specs. The furnace operated just fine for two heating seasons with this low speed draft. Now I'm having trouble getting the furnace to auto start (there is another whole thread on this problem in this forum). I measured the high and low speed draft readings and they are now .72 on high and .62 on low. Anyone have any ideas what may have caused them to change? Any ideas on what the change represents? combustion blower rotating too fast on low speed? not enough air entering the firebox? too much air entering the firebox? The stove was given a thorough cleaning from air intake right thru to the final elbow in the exhaust vent. It's as close to new (as far as cleanliness goes) as possible. I'd appreciate any ideas. I've run out of my own.
 
Oh good lord, here we go............yet another toy I will have to look at.............teehee.......

-Soupy1957
 
There is a low draft pot adjustment screw to the right of the igniter LED which you could tinker with.

However, I don't think this is your ignition problem. You are still within a range which should light.

It might be a faulty igniter, but one thing to try is remove the access plate held by two wingnuts
on the front of the burnpot and clean that air chamber with a vacuum hose or your finger.
This will remove the built-up gritty ash that has fallen thru the burnpot holes and has solved poor ignition
problems several times on my PF100.
 
Ok, been thinking about this a bit more...

If we discount a possible igniter problem...

You mentioned a higher draft reading in the burn chamber - this indicates
a greater vacuum than usual. I suggest checking the air intake flapper
door to see if it's stuck/frozen in the closed position. This might explain the higher
vacuum reading and also reduce air flow through the burn pot holes and resulting
poor ignition problem.

Hailfire
 
hailfire said:
Ok, been thinking about this a bit more...

If we discount a possible igniter problem...

You mentioned a higher draft reading in the burn chamber - this indicates
a greater vacuum than usual. I suggest checking the air intake flapper
door to see if it's stuck/frozen in the closed position. This might explain the higher
vacuum reading and also reduce air flow through the burn pot holes and resulting
poor ignition problem.

Hailfire

You are absolutely right, Hailfire. An obstruction in the air intake does increase vacuum in the combustion chamber. I placed my hand over the air intake while monitoring the pressure and it went up to 1.00 inches. Unfortunately, the flapper is working just fine. I have an OAK and have run the stove with and without my outside air connected with no change in pressures. I've checked the air passage from the intake right thru to the burnpot. All clear, no debris. This problem defies all the logic I can bring to bear on it. When the furnace is manually lit, it runs fine. Air flow is good, flame is good, heat output is good, etc. The D&^% thing just wont auto light. This is not rocket science.... air blows over a hot igniter that super heats the air which then enters the bottom of a stack of pellets causing them to heat up to the point of ignition.... DUH! Igniter gets hot... check, air flow is good... check, pellets ignite... NO CHECK What the heck am I missing????? I feel like I'm in the forest and cant see the trees.... This is sooooooo aggravating.
 
https://www.hearth.com/econtent/index.php/forums/viewthread/59175/

After reading this I'm wondering how long a period of time after you fire it in auto ignition do you wait before before deciding that it isn't going to fire. Also in this time frame, do you see any smoke comming from the burnpot? I know when I was using the cartridge ignition system in my boiler, from a cold start it would take forever to fire, a ton of smoke.
 
wil said:
https://www.hearth.com/econtent/index.php/forums/viewthread/59175/

After reading this I'm wondering how long a period of time after you fire it in auto ignition do you wait before before deciding that it isn't going to fire. Also in this time frame, do you see any smoke comming from the burnpot? I know when I was using the cartridge ignition system in my boiler, from a cold start it would take forever to fire, a ton of smoke.

I waited a good 5 minutes and no there was no smoke. The furnace waits 2 or 3 minutes to detect heat then goes into a feed cycle where it feeds more pellets into the burn pot. It does this several times with a pause of a minute or so between tries before giving up just before the burnpot overflows with pellets. It used to light after about 2 minutes and there was plenty of smoke and flying sparks a good 30 seconds to a minute before bursting into flame. I'm getting none of that now. I'm at the point where I'm going to put a new (another new) igniter in it. The igniter I have gets red hot but maybe it's not getting hot enough.
 
SmokeyTheBear said:
Is it possible that the pellets are too far away from the igniter?

The igniter is mounted in contact with the underside of the burn pot floor and the pellets are sitting on the burn pot floor right above it. They can't physically get any closer than they already are. Or if you meant, have they fed far enough up the slope to cover the holes over where the igniter is, the answer is yes.
 
ex-oil slave said:
SmokeyTheBear said:
Is it possible that the pellets are too far away from the igniter?

The igniter is mounted in contact with the underside of the burn pot floor and the pellets are sitting on the burn pot floor right above it. They can't physically get any closer than they already are. Or if you meant, have they fed far enough up the slope to cover the holes over where the igniter is, the answer is yes.

That would cover the ground, now if the igniter connections are not oxidized and are tight the only other thing would be a bum igniter.
 
ex-oil slave said:
wil said:
https://www.hearth.com/econtent/index.php/forums/viewthread/59175/

After reading this I'm wondering how long a period of time after you fire it in auto ignition do you wait before before deciding that it isn't going to fire. Also in this time frame, do you see any smoke comming from the burnpot? I know when I was using the cartridge ignition system in my boiler, from a cold start it would take forever to fire, a ton of smoke.

I waited a good 5 minutes and no there was no smoke. The furnace waits 2 or 3 minutes to detect heat then goes into a feed cycle where it feeds more pellets into the burn pot. It does this several times with a pause of a minute or so between tries before giving up just before the burnpot overflows with pellets. It used to light after about 2 minutes and there was plenty of smoke and flying sparks a good 30 seconds to a minute before bursting into flame. I'm getting none of that now. I'm at the point where I'm going to put a new (another new) igniter in it. The igniter I have gets red hot but maybe it's not getting hot enough.
Are you saying that even though the pellets that have fed into the burnpot on startup have not ignited, the auger will continue to feed pellets to the point that they overflow the burnpot? If so, IMHO, I don't believe this should be doing this. On my boiler, the auger feeds pellets on startup, no more pellets are fed until the ESP senses the temp high enough to indicate that ignition has happened. This maybe your problem with ignition when pellets are being augered into the burnpot at the same time. Don't know, just a thought.
 
Hey Wil,

No, the stove doesn't continually feed pellets until the burn pot overflows. It will feed for a minute then stop for about 3 minutes (I've never timed it, but it's a long time when you are waiting). If the ESP doesn't detect heat after 3 minutes it goes into another 30 second feed cycle (I'm assuming the software at this point is thinking that not enough pellets were fed into the burn pot). After this second feed cycle it waits a minute or so for the ESP to detect heat. Is the ESP still does not feel heat, the feed motor augers more pellets into the burn pot for another 30 seconds. Then it waits again. It does this 3 or 4 times then finally gives up if the ESP doesn't detect heat.
 
Oh, okay, I understand now. When I had the igniter fail on my boiler, no more pellets fed into the burnpot other than the ones on startup, something to ask your dealer to confirm that it should be doing that. I believe you should at least get a little smoke but.... if that new igniter is not getting hot enough, probably not. The new igniter that was installed, was it under the warranty or did you have to pay for it?
 
Seems to be narrowing down to just a couple of possibilities.

I reckon that since it's the start of a new season you might be using
older pellets left over from last season. It could be that you can get them
to light with Gel or a propane torch, but due to staleness or moisture
the superheated air from the igniter is insufficient for combustion.

I don't know if you've already tried new pellets but you seemed to have
ruled out everything else but the igniter.

Hailfire
 
Wil,

The igniter was warranty. However, I'm beginning to wonder if it's the right one. My daughter picked it up from the dealer on her way thru (dealer is 90 miles away) and the guy that gave it to her wasn't sure if it was the right one. It looks the same and like I said it glows red when power is applied, but maybe it's rated at a lower wattage. Wouldn't that be a corker if all this time I'm fighting a 200 watt igniter where I should have a 300 watt one..... Hmmmmmm
 
Hailfire,

I started the season with 3 new bags of pellets the local pellet dealer gave me to try out. They didn't work either so I tried my left over pellets that were stored in the garage all summer. No joy with them. It's got to be the darn igniter!!
 
ex-oil slave said:
Wil,

The igniter was warranty. However, I'm beginning to wonder if it's the right one. My daughter picked it up from the dealer on her way thru (dealer is 90 miles away) and the guy that gave it to her wasn't sure if it was the right one. It looks the same and like I said it glows red when power is applied, but maybe it's rated at a lower wattage. Wouldn't that be a corker if all this time I'm fighting a 200 watt igniter where I should have a 300 watt one..... Hmmmmmm
With your voltmeter, measure the actual voltage to the igniter, measure the resistance of the igniter, plug the voltage results and the resistance results into the power calculator to determine what the wattage is of your igniter.

http://www.the12volt.com/ohm/page2.asp
 
Wil,

The Voltage measured at the connector on the control board (the wires that feed the igniter) was 118 volts AC and the igniter resistance was 47 or 48 ohms. It should be 296 (at 47 ohms) watts according to my calculations (power = volts squared divided by resistance). So it seems right mathematically. However, I still get no flames.
 
Here is what I'm thinking, for what its worth. I know that the quanity of pellets in the burnpot directly effects how quickly the pellets ignite. If in fact, after the auger feeds in pellets at startup, it cycles the auger again and again prior to the pellets burning it just seems to me that this would prolong the ignition because as pellets are fed into the burnpot, the pellets already in the burnpot being heated by the igniter are going to move. I don't know on the pf100 if its easy to unplug one wire going to the auger. If its easy, on start up, after the auger feeds and stops for ignition, before it can auger in more pellets, unplug one of the wires which will prevent any more pellets being fed into the burnpot, see if the pellets will ignite after a few minutes.
 
You can halt the auger motor by opening the hopper lid to trip the vacuum switch, during startup the igniter stays on in this state.

You can control the amount of pellets fed into the burn pot this way.

Hailfire
 
If this is a newly installed igniter:
I have read forum posts that mentioned the igniter bracket being installed 180 out on its mounting holes causing no ignition. It is an offset bracket which would change the location of the igniter in the burn pot.
Old igniter part number: 1-10-06620
New 15 fin igniter part number: 3-20-677200

http://i357.photobucket.com/albums/oo18/eewing_01/Igniterslabels.jpg


Also remember a post that said igniter wires laying against the burn pot and firebox caused the insulation to break down and the igniter wires started to arc to the metal. My dealer just installed a new igniter in my PF100; the new igniter is not even making smoke and now I can hear arcing in the fire box. So I'm manually starting it and the dealer tech will be back soon to fix it.
 
I have my stove three years now and last year i had the same issue. i replaced a couple ignitors only to find out that the burnpot had swelled uo and the holes cracked forming grooves in the burnpot i replaced it under warranty. One thing might throw the draft off is if it is windy out wouldnt the draft increase in the low setting?
 
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