Low draft adjustment screw

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pelletkid

New Member
Oct 10, 2011
33
I just got my new p35i installed and working!! I have tried it on room temp at 75degree and feed rate at 3. It heats great! I have a noise like a whistle when the flame is real small which is most of the time its not that cold outside today only in the 50s. Also i turned down the low draft screw all the way and that makes the flame look better not so wild also it dont shoot near as many sparks up. Were should this adjustment screw be set? Also why do i have the whistle some times. I used 3 in dura vent 14 feet long to cap straight up the old chimney.
 
You dont want to turn it down so much, that yoi have a "lazy flame". The flame should be active and throwing some sparks. You dont want pellets getting ejected. But sparks are not a bad thing.

The whistle is feom air coming through the burn pot holes. My Quad does this on Low.

I will let a Harman owner assist you in the screw. But I.dont think it should be all the way down. If the flame is lazy, your pellets wong have complete combustion and your firebox will get black and sooty.
 
With it turned all the way down the flame still throws some sparks and is not what i would call lazy. The elevation here is very low is like only 150 feet not sure if that makes a difference.
 
May make a difference. I was just warning of a lazy flame. Harman folks should be along shortly. Sunday night football and Dinner.

There are videos on Youtube, if you want to watch some of them in the meantime. To get an idea.
 
I rather strongly suggest you dont mess with the potentiometer unless you have a magnehelic......lazy flame isnt good....that being said, i think the adjustment only makes a few volts difference
 
IMHO...turn the screw half way up, then adjust it an 1/8th of a turn counter clockwise until the flame is barely licking the heat exchangers...lazy flame=bad...decent lick is good!
 
Lousyweather said:
I rather strongly suggest you dont mess with the potentiometer unless you have a magnehelic......lazy flame isnt good....that being said, i think the adjustment only makes a few volts difference

I agree. You should not be adjusting that screw unless you have the test equipment to test it. you may have more problems with the stove.
 
Washed-Up said:
IMHO...turn the screw half way up, then adjust it an 1/8th of a turn counter clockwise until the flame is barely licking the heat exchangers...lazy flame=bad...decent lick is good!

That is were the factory had it set so i will turn it back there for know and try that. The flame still has a good fast look to it with it turned all the way down and with it turned up to a 1/8 it almost blows the flame out when it is running on low! Should it be almost blowing it out on low or not? I have had experience with pellets stoves in the past and know what the flames on them look like but this is my first experience with a harman and not sure. This harman burns a lot slower then any of the other ones i have used and it just seems to almost blow out the flame. Should it really about blow the flame out on low?
 
other than some minute flame changes, the setting on the board most likely wont change your draft enough to do all that much. My aforementioned comment comes mostly from the service side......nothing worse than working on a unit trying to find out whats wrong when someone has "tinkered" with it.....then we get to figure out what they changed and THEN the issue with the stove!
 
I would take a look at you hopper lid gasket. If it is not sealed tightly or if there is a pellet or two caught in the gasket it will whistle a bit.
 
CJ-SR4ever said:
I would take a look at you hopper lid gasket. If it is not sealed tightly or if there is a pellet or two caught in the gasket it will whistle a bit.

Did that and no there is not any caught in the gasket.
 
Lousyweather said:
other than some minute flame changes, the setting on the board most likely wont change your draft enough to do all that much. My aforementioned comment comes mostly from the service side......nothing worse than working on a unit trying to find out whats wrong when someone has "tinkered" with it.....then we get to figure out what they changed and THEN the issue with the stove!

I'll give you that, but adjusting the low draft blower speed is pretty inconsequential in my experience. My draft is "off the charts" high and adjusting the pot from zero to -10 volts doesn't really move the magnehelic needle an appreciable amount. Maybe the adjustment is more relevant if the draft numbers are closer to factory spec?

My only option appears to be flow restriction in the exhaust. Not ideal, but it's worth a try...with caution.
 
lbcynya said:
Lousyweather said:
other than some minute flame changes, the setting on the board most likely wont change your draft enough to do all that much. My aforementioned comment comes mostly from the service side......nothing worse than working on a unit trying to find out whats wrong when someone has "tinkered" with it.....then we get to figure out what they changed and THEN the issue with the stove!

I'll give you that, but adjusting the low draft blower speed is pretty inconsequential in my experience. My draft is "off the charts" high and adjusting the pot from zero to -10 volts doesn't really move the magnehelic needle an appreciable amount. Maybe the adjustment is more relevant if the draft numbers are closer to factory spec?

My only option appears to be flow restriction in the exhaust. Not ideal, but it's worth a try...with caution.

You could try that flow restriction on the input side.

Safer than blocking the output side of a blower and a lot easier on the blower motor.
 
lbcynya said:
Lousyweather said:
other than some minute flame changes, the setting on the board most likely wont change your draft enough to do all that much. My aforementioned comment comes mostly from the service side......nothing worse than working on a unit trying to find out whats wrong when someone has "tinkered" with it.....then we get to figure out what they changed and THEN the issue with the stove!

I'll give you that, but adjusting the low draft blower speed is pretty inconsequential in my experience. My draft is "off the charts" high and adjusting the pot from zero to -10 volts doesn't really move the magnehelic needle an appreciable amount. Maybe the adjustment is more relevant if the draft numbers are closer to factory spec?

My only option appears to be flow restriction in the exhaust. Not ideal, but it's worth a try...with caution.

If your draft is off the charts high then do you at least do what you can and run it as low as you can adjust it?
 
pelletkid said:
If your draft is off the charts high then do you at least do what you can and run it as low as you can adjust it?

Not sure what you mean? Draft fan voltage is at -10 which is the minimum voltage, this is per my Harman diagnostic tool.
 
lbcynya said:
pelletkid said:
If your draft is off the charts high then do you at least do what you can and run it as low as you can adjust it?

Not sure what you mean? Draft fan voltage is at -10 which is the minimum voltage, this is per my Harman diagnostic tool.

The draft adjustment screw. Do you have it set all the way counterclockwise to try and of set the high draft?
 
Maybe i am stupid for asking all this. If so let me know :-S
 
SmokeyTheBear said:
You could try that flow restriction on the input side.

Safer than blocking the output side of a blower and a lot easier on the blower motor.

Hmmmm. Already have 1/2 the intake covered to try and help the "woofing" I get at 50% flame, or so. That's a separate issue, really. I kind of gave up on proper draft in favor of eliminating the "woof". Covering the intake seems to minimize woofing, but wouldn't restricting the incoming air also creates lower pressure inside the stove resulting in a higher magnehelic reading? Trying to lower the vacuum pressure in the stove, so restricting the exhaust would lower vacuum pressure in the stove, no?
 
pelletkid said:
The draft adjustment screw. Do you have it set all the way counterclockwise to try and of set the high draft?

Yep, full CCW on the low draft adjustment pot. This is a -10 volt adjustment.

PS - Pelletkid - No such thing as dump questions, just dumb answers. :)
 
lbcynya said:
SmokeyTheBear said:
You could try that flow restriction on the input side.

Safer than blocking the output side of a blower and a lot easier on the blower motor.

Hmmmm. Already have 1/2 the intake covered to try and help the "woofing" I get at 50% flame, or so. That's a separate issue, really. I kind of gave up on proper draft in favor of eliminating the "woof". Covering the intake seems to minimize woofing, but
but wouldn't restricting the incoming air also creates lower pressure inside the stove resulting in a higher magnehelic reading? Trying to lower the vacuum pressure in the stove, so restricting the exhaust would lower vacuum pressure in the stove, no?

Give it a try and see what the gage says. It is just that blocking the output of a blower is not easy on the blower motor and the slowed down/trapped exhaust can cause over heating issues in the vent from that point backwards. There are warnings about dampers in the exhaust of pellet stoves because of that.
 
I will turn it full ccw that seems to make a little difference on my stove. As far as restricting the incoming air my stove is a insert so i would have to pull it out to get to it.
 
SmokeyTheBear said:
lbcynya said:
SmokeyTheBear said:
You could try that flow restriction on the input side.

Safer than blocking the output side of a blower and a lot easier on the blower motor.

Hmmmm. Already have 1/2 the intake covered to try and help the "woofing" I get at 50% flame, or so. That's a separate issue, really. I kind of gave up on proper draft in favor of eliminating the "woof". Covering the intake seems to minimize woofing, but
but wouldn't restricting the incoming air also creates lower pressure inside the stove resulting in a higher magnehelic reading? Trying to lower the vacuum pressure in the stove, so restricting the exhaust would lower vacuum pressure in the stove, no?

Give it a try and see what the gage says. It is just that blocking the output of a blower is not easy on the blower motor and the slowed down/trapped exhaust can cause over heating issues in the vent from that point backwards. There are warnings about dampers in the exhaust of pellet stoves because of that.

Point taken. Being a basement install, low EVL and a 4" exhaust, this seems to "supercharge" my draft. Probably prudent to accept it as is and walk away. Unfortunately, I can't leave well enough alone...
 
lbcynya said:
SmokeyTheBear said:
lbcynya said:
SmokeyTheBear said:
You could try that flow restriction on the input side.

Safer than blocking the output side of a blower and a lot easier on the blower motor.

Hmmmm. Already have 1/2 the intake covered to try and help the "woofing" I get at 50% flame, or so. That's a separate issue, really. I kind of gave up on proper draft in favor of eliminating the "woof". Covering the intake seems to minimize woofing, but
but wouldn't restricting the incoming air also creates lower pressure inside the stove resulting in a higher magnehelic reading? Trying to lower the vacuum pressure in the stove, so restricting the exhaust would lower vacuum pressure in the stove, no?

Give it a try and see what the gage says. It is just that blocking the output of a blower is not easy on the blower motor and the slowed down/trapped exhaust can cause over heating issues in the vent from that point backwards. There are warnings about dampers in the exhaust of pellet stoves because of that.

Point taken. Being a basement install, low EVL and a 4" exhaust, this seems to "supercharge" my draft. Probably prudent to accept it as is and walk away. Unfortunately, I can't leave well enough alone...

I understand the urge to tinker, I do my share of it, but I always try be certain that what I'm doing isn't apt to bite me on the rump. I want to live to be a really grumpy old man ;-) .
 
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