P 68 problem. Too much draft??

[pipeliner542]

I have recently purchased a dealer refurbished 2008 Harman P68. It was running in my shop till I could get the hearth constructed in the house. In the shop it was a direct vent through the wall with 24" straight pipe. Moves it to the house hooked it up and the stove seems to have to much draft. It has no flame height and the flames are blue and 1/2" above and wrapped around the pellets. Appearing to be pulled into the holes in the burn pot. The venting installed is duravent all the joints have.been foiled taped proir to install. Starting at the stove a harman to pipe adapter then a 6" and 12" horizontal pipe next is a t with clean out cap on bottom. A 12" vertical then a 90 into the wall and a 12" section then the termination piece outside. Total EVL measuring joint to joint and adding for the T and 90 is 13.4791'

I hooked up a manometer for some draft measurements.

Cold stove,test mode unhooked flue
High was -.69-.73. Low .56-.59
Connected venting
High -.62-.65. Low -.52-.55
These numbers are the Low voltage draft screw in full counter clockwise position

Same test with Low voltage screws in full clockwise position
Unhooked flue
High .71-.73. Low .64-.67
Connected venting
High .63-.66. Low .56-.59
Input voltage to unit is 120.3 volts 60hz
Voltage at combustion blower 120.0 volts regardless of Low voltage switch position.
Stove has been thoroughly cleaned with vacuum and compressed air. All doors and accesses have been cleaned out.
Door gasket was adjusted using dollar bill and slight tension
No staus lights on.
Controls have been set at both room and stove temp.
Stove temp high ,feed at 4 stove will stay burning but side of firebox Temps never get above 260 degrees top of stove with distribution blower on high won't exceed 155 degrees
I'm burning somerset premium pellets which I was burning before with no problems.
Dealer which has been helpful is 4 hrs away. Is scratching his head. No local support so I'm trying here. Sorry for the long post just trying to get all the info out there that I had found
Has red wired probe and impedance of probe is 1100 ish ohm at 70 degrees temp(not sure if that's good or bad
Room temp setting had no effect on anything.

 

[Golfeur]

I do not know if in test mode it is possible that the combustion fan does not take into account the adjustment of the draft screw.
I adjusted mine with the stove on in normal operation I adjusted the maximum draft as recommended and the minimum a little higher than recommended because at the recommended minimum it did not burn well and got clogged and it showed by the color of the flame.
I don't remember the adjustment values I have for the draw.

You may need to try adjusting it with the stove on.

 

[pipeliner542]

I have. Turning the draft screw with it running does not do anything. I need to turn the combustion fan down and it won't adjust lower. I can put a piece of foil over the intake port to block it off completely leaving it open about a 1/4" and the flame pattern burns as it should. Stove appears to be getting to much air.

 

[pipeliner542]

I would believe with very limited knowledge that the screw in test mode made small changes as reflected in the measurements taken. It increased and decreased accordingly. But that is just what I am.seeing at the moment. Those number provided were done multiple times and gave almost identical results

 

[Golfeur]

If you look at the air inlet and you open the valve completely you will see another duct which leads the air for cleaning the glass so if the valve does not open enough and all the air goes below the burn pot which can cause your problem because there is still a good amount of air that goes to cleaning the glass

 

[pipeliner542]

I will check that now. Thanks

Dealer said with all info I sent him and videos of multiple things his Harman tech said he would bet on the esp probe being bad. He is shipping one out. He also suggested to remove the auger assembly and make sure something didn't get in there and cause the auger to bind or feed slowly. He figured control board called for the amount of air and fuel but there isn't enough fuel for the air being supplied. Guess I'll pull it and see if it's clear.

 

[pipeliner542]

Port was clean for the glass wash. And auger tube was clear as well. Guess it's a waiting game for the new probe unless someone has any other ideas.

 

[Golfeur]

the new esp probe tomorrow or later

 

[bogieb]

Usually when the flame is crawling toward the holes in the burn pt, that means that not enough air is getting to where it needs to be. That can mean there is a blokage between the air intake and the pot, or that something is not put together correctly, which disturbs the air flow. Seriously, you moved the stove and it suddenly has issues - although it could be parts related and just weird timing, I'd look at the free stuff first.

Check the air path - did ashes get back at the throat and cause a dam (had that happen), or did some packing material get sucked in there - I've found a piece of saran-wrap type stuff that had to have been there for a while, but finally worked itself into a position to block too much air. Is the cover under the fire pot on correctly - take it off and reinstall becuase looks mean nothing. Are the holes in the burn pot clear? Is the fines box clean and the cover on correctly (again, remove the cover and reinstall.

And lastly, you didn't say if you had an OAK, but if your house is too "tight" and there you do't have an OAK, it may not be able to get the air it needs. The only way to check that is to crack open a window that is close by, and see if that has an effect.

 

[3650]

I tried setting the draft on my Accentra with similar results. I can’t get it adjusted anywhere near spec. Full counter clockwise on the screw and still high draft readings. Top of the stove is Luke warm and the stove pipe just seems way hotter then it should be. Let us know if the ESP solves your issue.

 

[Golfeur]

The esp probe is used for temperature control and also that if the temperature of the exhaust is too high it will make sure to reduce the fire in the stove to prevent a fire hazard.
If your pipe is hotter than it should be, your probe is seeing the temperature lower than actual.
either your probe is defective or dirty or obstructed and does not detect the heat evacuated

 

[pipeliner542]

Tried a temporary OAK. Makes no difference.
I took the stove outside and lit it with no venting same result.

I can completely cover the intake with foil poke a 1/4" hole in it and it burns a perfect flame. I keep asking everyone where these stoves could leak air. The response is it would light a status light if it did.

My family used to own a heating oil and coal business in Eastern pa. I've been around coal stoves and boilers. This is my first pellet stove I burned it three days in the shop which it never seemed to burn right compared to the ones he had burning in his showroom. Flames were burning hot. Mostly blue short flames. It looks like more of a hand stoked coal forge flame. This forum by far has more information than anywhere else on pellet stoves. I have found plenty of info that should have eliminated any non electrical problems.
I bought a harman soley based on the information and reviews found here. I was gonna go coal but would have had to rebuild a chimney and didn't want to do it in the winter.
If the esp probe doesn't fix it I'm tearing the whole stove down and reassemble it

 

[Golfeur]

normally when the draft is strong the flames are high and we even see sparks rising

 

[Golfeur]

If the draft is high and the fire in the pot is low, you are taking air from somewhere other than the holes in the burn pot.
The door seal and that of the ashtray door
the hopper cover gasket or the hopper gasket above the screw
the lid of the fine box not closed properly
the lid below the combustion pot is not closed properly or is not airtight

 

[Mt Bob]

Ignore your readings, they are within reason.
If you block/restrict the air intake, you increase the draft, but lower the volume. Just the opposite if you block off/restrict the exhaust.
Top of pellet stoves are not meant to get real hot.
It sounds like not enough pellets.
A good test, light stove, put in "stove temp", turn up to #6, then the switch to "manual". Flames should get up to the top of stove, and stay there a while. May not stay there, as it will be affected by the blower setting, and how much heat the stove itself loses to the room, as this affects the exhaust probe.

 

[3650]

Ignore your readings, they are within reason.
If you block/restrict the air intake, you increase the draft, but lower the volume. Just the opposite if you block off/restrict the exhaust.
Top of pellet stoves are not meant to get real hot.
It sounds like not enough pellets.
A good test, light stove, put in "stove temp", turn up to #6, then the switch to "manual". Flames should get up to the top of stove, and stay there a while. May not stay there, as it will be affected by the blower setting, and how much heat the stove itself loses to the room, as this affects the exhaust probe.

Don’t mean to hijack op’s thread but I think velocity may be my issue. My chimney is 3” and about 13 or 14 feet. Probably should have used 4 inch.

 

[rickwai]

When starting the stove next time check that the auger motor is running at the proper speed. It should be a 4 rpm motor which means it should make a revolution every 15 seconds. When starting in auto does the initial charge of pellets fill the pot approx 3/4 full or more and light quickly without having to do a second push of fuel?
Also may want to check the dip switch settings on the board to verify that it is set for the P68

 

[pipeliner542]

New esp arrived today installed it. Stove does the same thing. They are sending a circuit board now. And the idea of not enough pellets is what is being stated as the problem.

 

[pipeliner542]

Lit stove again. Put in stove mode turned up to 6 flopped to manual flames are down to almost nothing now.

 

[Mt Bob]

Didn't happen to blow stove out with air pressure before moving into house? If so, may have damaged vacuum switch. Is auger motor running when the auger light flashes? After start up, settings in a higher setting, auger should be running a lot. As a test, you can jumper vacuum switch and see if it burns different.

 

[mtnbiker727]

When I kick my stove on with pellet feed set to 4, it fills the burn pot with pellets within about 4 minutes, then it lights shortly after (sometimes before pellets stop feeding). About 15 minutes in, the flames are touching the heat exchanger.

Sounds like your stove never really did that...

Have you done the dollar bill test on the door? The door handle can be adjusted to make a tighter seal.

 

[pipeliner542]

Yes I adjusted the door gasket with a dollar bill.
I disconnected the pressure switch. I also had all the doors and hopper open when doing so. Stove had no pellets in it including the auger area. I also had the regulator set to 25lbs. It was only used to get fine dust out and then re vacuum

 

[pipeliner542]

Auger light lights when auger runs. It seems to run very infrequently. It definitely doesn't push enough pellets into the pot.

 

[bogieb]

Lit stove again. Put in stove mode turned up to 6 flopped to manual flames are down to almost nothing now.

This is a long shot, but check that your temp probe is fully seated at the back of the stove. I know this shouldn't affect anything when in stove temp mode - but I had this happen with my P61a and once and once I fully seated the temp probe, the flame height and feed rate acted as it should.

 

[Mt Bob]

"As a test, you can jumper vacuum switch and see if it burns different."
Also, depending on year, yours may have a hopper switch, that you can bypass and test.