Older Harman PF100 ignition causes "woosh" and smoke in ductwork

[DougInMaine]

I searched this forum and couldn't find a problem quite like mine.

Some background: My Harman PF100 was installed in approximately 2003. After some initial quirks, mostly due to dealer/installer ignorance (they were new to this product), the furnace has been reliable and efficient. In a dozen or so years, I've only had to replace the igniter and I added a Skytech remote thermostat - thanks to information on this site. Initially, at the beginning of each heating season, I laid in a supply of 3 to 4 tons of bagged pellets from various suppliers. Now that bulk-delivery is available in my area of central Maine, I use only premium pellets (usually 3 tons per delivery), stored in a monster bag in my basement. I clean the system thoroughly once a year and "spot clean" during the season.

Anyway, lately I've had a strong wood smoke smell - nothing visible - as the pellets ignite. The odor, though strong, only lasts briefly, so I suspect one big puff. Now I think an important clue is that as the pellet pile flashes over, there is a short blast of air that really rattles that little damper in the firebox door. You hear a mighty "woosh, clang, clang, clang" upstairs in the living room. Then the smell. Then normal operation. There is nothing unusual nor any smoke smell after that, even when the circulator is running.

Thoughts anyone? Thank you!

 

[Delta-T]

Good chance the delayed ignition causes a rapid pressure change and has messed with the silicone seal on the exhaust pipe allowing smoke to get blasted into the plenum. Reseat the pipe adapter onto the exhaust flange and redo the silicone. Make sure the adapter is not pressed all the way down onto the skin of the unit. The flange and the skin are not sealed. Leave about 1/8" between the adapter and the unit so you can see the seal. Should fix it right up..

 

[Delta-T]

Could also be the door gasket. They tend to wear on the hinge side..

 

[DougInMaine]

Could also be the door gasket. They tend to wear on the hinge side..

Those areas sound like a good place to start and make sense for an older machine that's been run hard. I'll give your suggestions a try. Thank you!

 

[wil lanfear]

Not only the things that have been mentioned already but maybe excessive amount of pellets in the burnpot, will create tons of smoke with explosive starts. IMHO, the least amount of pellets in the burnpot and still have ignition the less smoke that can result in explosive starts.


https://www.hearth.com/talk/threads/harman-pf100-igniter-dip-switch-settings.124790/#post-1675439

 

[SmokeyTheBear]

Gee can I play?

I'll add a nice clean air path in the igniter area (covers and such back on correctly) and to outside the termination cap also helps the ignition process to be way less smokey and faster lighting.

Usually with no loud noises follow by smoke in the stove room.

 

[DougInMaine]

Again, thanks all. I can see how normal "wear and tear" would cause new issues, but I haven't made changes to the pellet feed. Can that alter over time? This is a recent problem which started last season and continues now, following a fanatical cleaning.

BTW, is there a shop manual that covers the less obvious inner guts and adjustments?

 

[SmokeyTheBear]

How many times has the igniter cycled on that unit?

It just might be at the end of its useful life.

 

[Don2222]

Hello
I have worked on those units.
Take out the exhaust blower and clean it and the exhaust chamber if not done recently.

 

[Bioburner]

Be interesting to see what your draft vacuum is. Loose door seals allowing air in and not through the pot increases time before ignition. I replaced the door seals on the PC45 last fall and was a marked decrease in time before ignition. Those pesky vacuum leaks add up fast.

 

[DougInMaine]

How many times has the igniter cycled on that unit?

It just might be at the end of its useful life.

That's one part I did need to replace. I keep records and could check the exact date, but it has had long, hard use over many years. I wouldn't be at all surprised if it died soon.

However it lights reliably in under 10 minutes. How could the igniter cause my somewhat dramatic starts?

 

[SmokeyTheBear]

Time to heat the air increases. Couple that to a slight this and that and whoosh.

 

[DougInMaine]

Be interesting to see what your draft vacuum is. Loose door seals allowing air in and not through the pot increases time before ignition. I replaced the door seals on the PC45 last fall and was a marked decrease in time before ignition. Those pesky vacuum leaks add up fast.

Yes, I think I'll replace the seals in any event, even if just as preventive maintenance.

 

[DougInMaine]

Hello
I have worked on those units.
Take out the exhaust blower and clean it and the exhaust chamber if not done recently.

Done, thanks. I think I spend as much time on this as I do cleaning the firebox!

 

[wil lanfear]

Again, thanks all. I can see how normal "wear and tear" would cause new issues, but I haven't made changes to the pellet feed. Can that alter over time? This is a recent problem which started last season and continues now, following a fanatical cleaning.

BTW, is there a shop manual that covers the less obvious inner guts and adjustments?

BTW, is there a shop manual that covers the less obvious inner guts and adjustments?Not that I'm aware of.

After the auger stops feeding pellets at startup,how long does it take to ignite the pellets? First, dip switches 1,2,3 control the quanity of pellets fed into the burnpot for ignition.IMHO, this is why Harman has provided dip switches to control the amount of pellets fed into the burnpot prior to ignition, pellet manufacturers have different lengths of pellets. Now, if you're now using pellets that are short in length, it's possible that the quanity of pellets in the burnpot is to great for a smooth ignition, shorter pellets will feed more per revolution of the auger which will cause tons of smoke and explosive ignitions with excessive amounts of pellets in the burnpot.Take a look at the quanity of pellets in the burnpot at startup after the auger stops feeding, after you have ignition, if the burnpot is 3/4 full of pellets, this is way to many pellets being fed in for startup, I have my pb105 dip switches set so I can't see any pellets in the burnpot prior to ignition, but........ I have the pressure ignition which doesn't require as many pellets in the burnpot for ignition, a finned igniter requires a tad more pellets. If the quanity of pellets in the burnpot isn't excessive, it's already been mentioned, maybe it's time for a new igniter.

 

[SmokeyTheBear]

Done, thanks. I think I spend as much time on this as I do cleaning the firebox!

I'd spend more time on the stuff in the possible air flow restriction side of things than that huge firebox.