Harman draft questions

[Pellet_Pete]

I got a real steal on ebay on a brand new Dwyer 2001 magnehelic gauge so I can do the draft test on my Harmans. But of course this has only made more questions arise.

1) First tried it on the XXV, and both the high & low readings were at -0.65, which is reportedly "higher" than normal. Another thread from years ago suggests this is common (the readings being the same). But then, in troubleshooting air-tightness all around, I found that my door gasket isn't sealing well and should be replaced. But shouldn't a leaky door gasket decrease the vacuum in the stove? Not sure what to expect when I replace the gasket...even higher draft? This stove vents through the roof, about 8-10 ft. vertical.

3) My P61A is in the basement and vents into an existing chimney with about 23-25 ft. vertical. If I do a cold test for draft, it won't account for the natural pull of the chimney's draft while hot. But a pressure check during operation doesn't seem like a great idea. I'm leaning toward doing a cold draft adjustment and then choke off the intake (not OAKed) to make the flame "look right". Any thoughts?

 

[DAKSY]

You WANT to check the draft with the unit operating, but not necessarily burning...

http://www.manualslib.com/manual/256723/Harman-Pellet-P61a.html?page=20

 

[Harman Lover 007]

You WANT to check the draft with the unit operating, but not necessarily burning...

http://www.manualslib.com/manual/256723/Harman-Pellet-P61a.html?page=20

Do it in "test" mode as described in your manual....

 

[Pellet_Pete]

Don't worry folks, I knew enough to test the draft while in TEST mode. Would've been real hard to get a draft reading without any fans running - lol! For the P61A, I was concerned that the TEST mode draft adjustment wouldn't reflect actual draft conditions while the stove is fired up & the chimney's adding 25 ft. of natural draft onto the combustion fan.

 

[Mr. Spock]

Hey Pellet_Pete,
My XXV setup is identical to yours. I put a blast gate on the intake and restricted the air flow just enough to where the burning pellets would dance a little but not jump out of the burn pot. The restriction also got rid of the 'Woofing'.

 

[Pellet_Pete]

Hey Pellet_Pete,
My XXV setup is identical to yours. I put a blast gate on the intake and restricted the air flow just enough to where the burning pellets would dance a little but not jump out of the burn pot. The restriction also got rid of the 'Woofing'.

Aha, a blast gate - that would be easy to put in-line with my OAK. Thanks for the tip.

 

[TonyVideo]

This woofing you get, can you describe it? I have a P68 and a P43. The 43 makes this resonance sound periodically. Is that the woofing sound? It is in the part of the house we just past through so it is tolerable. It would be unacceptable in our main room. If this is correct I will check out the oak and do a draft test. The oak is straight out the back with the exhaust. No vertical pipe.

 

[Mr. Spock]

This woofing you get, can you describe it? I have a P68 and a P43. The 43 makes this resonance sound periodically. Is that the woofing sound? It is in the part of the house we just past through so it is tolerable. It would be unacceptable in our main room. If this is correct I will check out the oak and do a draft test. The oak is straight out the back with the exhaust. No vertical pipe.

Hi Tony,
Perhaps. First I have heard of it outside of an XXV. When the stove is going full it will sometimes make a low rumbling sound and the flame will flutter. At some point we started calling it woofing on the forum.

 

[TonyVideo]

That's it. Exactly what it does. Woofing. I guess I will check out the draft. I have a meter just need to do it.

 

[corkman]

what exactly is a blast gate and might someone have a pic of one.i just installed an Advance in my basement and the first couple of fires didnt look so good.its a simple up and out install with selkirk direct temp.flame is realy low and struggles to get above the top of the flame guide.flame is very brisk and pellets are dancing like crazy.i ran in stove temp with dial to 7 and feed at 4 and after 2 hrs had practically no ash in burnpot.bumped it up to 5 then 6 and still no ash buildup on front of pot.ups guy is walking down my driveway as i type this with my new draft meter so i will chk the draft and see where is at.im curious about this blast gate though.peace,Corkman

 

[Mr. Spock]

They come in varying designs but that basically what it looks like.

 

[corkman]

i tested the draft and i get a reading of .9 on high.i waited for combustion fan to go to low and distribution fan to high as per manual and i get .66 and thats with the draft adjustment turned all the ways counterclockwise.manual says low draft should be .35 to .45 but i cant get it any lower.suggestions???

 

[corkman]

I put a blast gate on the intake and restricted the air flow just enough to where the burning pellets would dance a little but not jump out of the burn pot. The restriction also got rid of the 'Woofing'.

what size Blast gate did you use.the 3" i presume and did you mount it right to the intake.i used the alluminum tape on the intake and stove is burning much better but i would rather install one of these.Peace,Corkman

 

[Mr. Spock]

I used a section of 3" pipe with gate from a retired machine shop.

 

[corkman]

thanks for the pic.looks like i got some work to do

 

[corkman]

is that one you used considered a half blast gate

 

[Mr. Spock]

Not sure as it was already constructed. Prolly made back more than 40 years ago. If I didn't have access to that I would have purchase some 3" flexible metal hose and attached a modern blast gate to that. Use a metal one.

 

[Delta-T]

I got a real steal on ebay on a brand new Dwyer 2001 magnehelic gauge so I can do the draft test on my Harmans. But of course this has only made more questions arise.

1) First tried it on the XXV, and both the high & low readings were at -0.65, which is reportedly "higher" than normal. Another thread from years ago suggests this is common (the readings being the same). But then, in troubleshooting air-tightness all around, I found that my door gasket isn't sealing well and should be replaced. But shouldn't a leaky door gasket decrease the vacuum in the stove? Not sure what to expect when I replace the gasket...even higher draft? This stove vents through the roof, about 8-10 ft. vertical.

3) My P61A is in the basement and vents into an existing chimney with about 23-25 ft. vertical. If I do a cold test for draft, it won't account for the natural pull of the chimney's draft while hot. But a pressure check during operation doesn't seem like a great idea. I'm leaning toward doing a cold draft adjustment and then choke off the intake (not OAKed) to make the flame "look right". Any thoughts?

nothing to worry about. Make sure the area under the burnpot is clean, along with the burnpot holes. DO you run the unit with OAK? this could add some resistance. If you tested the door with a doollar bill and it doesn't grip it, Do change the gasket, dont expect a huge change. The "natural draft" is not really a factor. The exhaust is pressurized. By the time it travels more than a few feet away from the unit its not that warm anyways. Dont block off the intake, do make sure the flapper works ok. You'll be running the combustion system rich = inefficient.

 

[Pellet_Pete]

Dont block off the intake...You'll be running the combustion system rich = inefficient.

But if I'm running it lean isnt that inefficient as well, sending an excess of hot air up the vent? I'm inclined to think it would be better to err on the side of richness. It would be hard to run it so rich that I'd be wasting fuel because I'd see unburned pellets/dirty-as-sin stove/smoke, whereas I coud run it leaner & leaner and only notice complete combustion. Correct me if I'm wrong, I don't quite trust my intuition on these things as yet. I know it sounds like splitting hairs but when I've burned 7 tons each of the past 2 years, optimization begins to become meaningful.

 

[Bioburner]

I just read the current manual for testing the P series and they want the draft test to be performed after the stove has run for 15 minutes on high. That's different than the older manuals.

 

[Mr. Spock]

I have read stove manuals where the air intake is adjustable. They say to adjust the draft to where embers will dance in the burn pot instead of jumping out. Seems logical to me.

 

[JDenyer236]

Burning rich will kill efficiency much more than running lean. While it is true that running lean will send more heat up the stack running rich will coat everything in a nice layer of insulating soot. A thick layer of soot will rob efficiency faster than anything else.