Pellet stove, too much draft?

[Ed in Maine]

Below is what I have for instructions that came with my Harman XXV. I am drafting at > -.6 in both high and low combustion modes. My magnohelic stops at .6 unfortunately, but I am going to borrow one that goes up to -2 this weekend. I turned the pot mentioned below to full CCW to minimize blower voltage, but it is still off the scale. They said not to worry about it at the end of the write up below, but I am wondering if I am burning too much fuel due to the increased draft?

Question, I am planning to hook the fresh air inlet to a pipe and run it about 4ft into the next room through sheetrock for air circulation. Would this help me reduce my draft?

Or, am I sweating the small stuff?

Thanks!
Ed


1. Plug unit into a 120VAC, 60 HZ outlet.
2. Close the hopper lid, front view door, and the ash pan.
Neither pellets or a fire are required for this test.
3. With the mode selector in the "OFF" position, turn
the feed adjuster to "TEST".
4. Record the high draft_____in W.C. (Normal is -.50
to -.60) The control will be on the High Draft for a total
of 2 minutes.
5. After 2 minutes, the combustion motor will go down to
low draft and the distribution blower will go on high. Allow
approximately 15 seconds to pass for the combustion
motor to slow before checking the low draft.
6. If the low draft is between -.35 and -.45, record the
reading _____ in W.C. If the reading is higher, slowly
turn the set screw counter-clockwise until the draft
lowers. If the reading is lower, very slowly turn the set
screw clockwise until the draft increases.
NOTE: The test mode alternates from high to low
draft every 60 seconds. If more time is needed
for draft adjustment, wait until the next low draft
cycle.
NOTE: In some cases, the draft may not go as low
as -.35 to -.45 even with the set screw completely
counter-clockwise, ideally, you should just set it as
low as possible.

 

[HarryBack]

youre "sweating the small stuff". Many draft readings "peg out". You arent burning more fuel, since its a metered flow of fuel, controlled depending on which mode the stove is running in. What you have to worry about is LOW draft.

 

[Kansasairbuspilot]

Ok, so I have a silly question....

What would the symptoms be with LOW draft?

On my harman accentra insert, I dont think I am getting the heat that I should.....

In a 720sqft room with 8 ft ceilings, there are cold spots.... (mainly farthest from the stove) AND....

Should I be able to lay my hand on the stove (top) when it is running on full throttle?

I am concerned as the gentleman who installed my stove never did a draft check, and the way he hooked it up to the damper on my existing fireplace chimney has me wondering.....

Can anyone help with a little friendly guidance?

Thanks all.....

 

[GVA]

low draft would give you a lazy flame. An example would be if you have a strong flame and you crack the front door open the flame starts to move forward and to the sides. Sorry it's the best way I can describe it....
Low draft can be caused by poor venting, blocked exhaust of lack of fresh air.
Since it's an insert you may be starving a bit for fresh air resulting in the lazy flame.. if you have a tight house try cracking a window nearby see if it changes.

Also placement of the room temp probe is important try moving it around the stove area and see if the stove changes... that is you'll here the distribution blower kick in or out.EDIT>This is not draft related..... But can affect the stove supplying heat to the room and the activity of the fire...

Anyway the draft check should have been done at least at the initial install it can be adjusted somewhat by eye but the WC is better to know if something major has gone wrong down the road.

 

[KeithO]

My St Croix Greenfield in fact has a damper on the fresh air side that is used to regulate draft. I have a 4" chimney close to 30ft tall and mostly in heated space, so the draft in my application is very good (never measured).

I have definitely found it beneficial to close the damper to reduce draft in my application (I gage it by how long the flames from the combustion become). With the inlet damper full open, hardly any flames can be seen, just hot glowing coals. If I progressively close it, the flames get bigger and bigger and lazier and lazier. The "right" position for me was with the damper about 50% closed. I got a lot more heat, much more visible flame and a significant drop in fuel consumption. Its all heat exchanger related. The faster either of the gasses flow through the heat exchanger, the less time they have to exchange heat.

I also think that since the fueling on these stoves is somewhat primative, too much draft is the same as burning a fire in an open fireplace with too much air diluting the combustion gasses and cooling them down. Just remember that these stoves are not like your cars injection system that has an oxygen sensor to help it control air fuel ratio. Auger speed / duty cycle is directly linked to a combustion fan speed and thats it. Chimney draft throws in a huge variable. If you have a typical instalation (direct vent fashion) they you probably approach the factory settings. If you have a long vertical or other chimney install, you have to do something to get things back in the ballpark.

 

[GVA]

Keith the Harmans combustion blower will change speed or run in high and low draft based on what the stove is doing it take the human interface out of it (as long as it was setup correctly in the beginning), no need to adjust any dampers.
That is why usually at the initial install the draft is checked and any variations from the initial #s can be attributed to airflow problems through the stove or venting components Ie :the stove is dirty or the flue is plugged Comb blower dying etc...

 

[HarryBack]

Ok, so I have a silly question....

What would the symptoms be with LOW draft?

On my harman accentra insert, I dont think I am getting the heat that I should.....

In a 720sqft room with 8 ft ceilings, there are cold spots.... (mainly farthest from the stove) AND....

Should I be able to lay my hand on the stove (top) when it is running on full throttle?

I am concerned as the gentleman who installed my stove never did a draft check, and the way he hooked it up to the damper on my existing fireplace chimney has me wondering.....

Can anyone help with a little friendly guidance?

Thanks all.....

not silly at all.

yes, the further from the stove you are, the cooler it will be irregardless of the unit. Yes, you can lay your hand on the top of the stove at full throttle, because thats basically the door to your pellet hopper, which you wouldnt want to get really hot anyways.

The installer DEFINITELY should have run a draft check, other than the obvious reasons, its useful later for diagnostic checks. The insert is notorious for people not cleaning the left exhaust tube well enough, which really screws up combustion ( a draft reading would show this). As for installation...we cant really comment without knowing how the installer did the work. Did he follow the manual?

 

[KeithO]

GVA The stove only responds to 1 thing and that is the heat demand you set. Based on that setting, it will operate the auger at a certain speed or duty cycle and increase or decrease the combustion blower speed. It will also adjust the convection blower speed according to a set program (off or low when cold, then increasing when up to temp and finally running flat out when at 100% heat.

What is missing from this picture is feedback regarding how the stove is actually doing. There is a sensor to determine whether the fire has gone out to shut down the stove, and there is a vacuum switch so that the stove knows if the door is open, in which case it will shut down after a short delay.

Generally, these stoves were designed for vents that have close to zero draft. In these conditions they would work with the factory settings just fine, unless your elevation was very high (10k ft). The primary problem is actually with chimneys that have good draft, these result in a lot of excess air. The damper I mentioned, adjusting it is a one time affair. It has a big effect on maximum heat, by reducing the amount of exces air. To get the low setting stable, one is able to trim both the auger feed rate and combustion air blower when at minimum heat rate (idle). This has no effect on the top end at all.

It took me a few days of fiddling to get my stove dialed in and the setings are lost in the CPU when one turns the power off (for the low heat trim) but getting the top end right was very important. St Croix has a whole section in their manual on making these adjustments. If you don't have a damper / throttle on your air intake there are ways to work around this if you have too much draft.

 

[Kansasairbuspilot]

Ok, so I have a silly question....

What would the symptoms be with LOW draft?

On my harman accentra insert, I dont think I am getting the heat that I should.....

In a 720sqft room with 8 ft ceilings, there are cold spots.... (mainly farthest from the stove) AND....

Should I be able to lay my hand on the stove (top) when it is running on full throttle?

I am concerned as the gentleman who installed my stove never did a draft check, and the way he hooked it up to the damper on my existing fireplace chimney has me wondering.....

Can anyone help with a little friendly guidance?

Thanks all.....

not silly at all.

yes, the further from the stove you are, the cooler it will be irregardless of the unit. Yes, you can lay your hand on the top of the stove at full throttle, because thats basically the door to your pellet hopper, which you wouldnt want to get really hot anyways.

The installer DEFINITELY should have run a draft check, other than the obvious reasons, its useful later for diagnostic checks. The insert is notorious for people not cleaning the left exhaust tube well enough, which really screws up combustion ( a draft reading would show this). As for installation...we cant really comment without knowing how the installer did the work. Did he follow the manual?

First of all, thank you so much to all who responded! I love this forum, as there is such great member participation....

As for the installer, I know he did not run a draft check. As a matter of fact, he just hooked up the stack from the back of my insert, to a "plate" he made out of metal, to where my damper used to be located in my fireplace.....

I am starting to think that my accentra might run more efficiently, and use less fuel if I ran the correct stove pipe all the way to the top of my masonry chimney??..... The way it is set up now, the exhaust from the stove dumps into my 8inch or so square chimney.....

I appreciate any and all feedback.... Once again, you guys are awesome...

 

[BrotherBart]

Question for da pellet pros. How is a Magnehelic hooked up to a pellet stove to measure draft?

 

[GVA]

Question for da pellet pros. How is a Magnehelic hooked up to a pellet stove to measure draft?

There is a bolt hole on the stove that you remove and insert the tube into.

 

[GVA]

GVA The stove only responds to 1 thing and that is the heat demand you set. Based on that setting, it will operate the auger at a certain speed or duty cycle and increase or decrease the combustion blower speed. It will also adjust the convection blower speed according to a set program (off or low when cold, then increasing when up to temp and finally running flat out when at 100% heat.

What is missing from this picture is feedback regarding how the stove is actually doing. There is a sensor to determine whether the fire has gone out to shut down the stove, and there is a vacuum switch so that the stove knows if the door is open, in which case it will shut down after a short delay.

Generally, these stoves were designed for vents that have close to zero draft. In these conditions they would work with the factory settings just fine, unless your elevation was very high (10k ft). The primary problem is actually with chimneys that have good draft, these result in a lot of excess air. The damper I mentioned, adjusting it is a one time affair. It has a big effect on maximum heat, by reducing the amount of exces air. To get the low setting stable, one is able to trim both the auger feed rate and combustion air blower when at minimum heat rate (idle). This has no effect on the top end at all.

It took me a few days of fiddling to get my stove dialed in and the setings are lost in the CPU when one turns the power off (for the low heat trim) but getting the top end right was very important. St Croix has a whole section in their manual on making these adjustments. If you don't have a damper / throttle on your air intake there are ways to work around this if you have too much draft.

I'm confused are you directing a question to me?

 

[BrotherBart]

Question for da pellet pros. How is a Magnehelic hooked up to a pellet stove to measure draft?

There is a bolt hole on the stove that you remove and insert the tube into.

Ah! Thanks. I kept seeing references to testing draft with one and could not figure out where it connected.

 

[Tristan]

Does anyone know where I can rent a magnehelic (or however that is spelled)? I live in Central MA. Thank you.

 

[FireJumper]

I don't think you can actually rent one. I don't know if they're are dealers out there that do that or not. you may be better off purchasing one. You may be albe to find one at your local HVAC stores. OR you can look at the link below to get one.

(broken link removed)

 

[Tristan]

Grainger indeed has alot of great stuff, but i cannot spend $70 on a piece of instrument i know nothing about and to be used only once. Although i did the stove install myself, can I ask the dealer to come out and verify the draft as part of a warrantee issue? I.e. "Something is wrong with my stove, the flames are way too high, NOT WIDE, but really high"

 

[cantman]

I just installed my Harman XXV and did an initial draft test. My setup consists of a stove adapter + 4" Tee + 17' X 4" vertical flue pipe run. (Simpson Pellet Vent Pro)
I havn't installed the outside air kit yet. The draft readings are as follows:

- .77" wc for high draft
- .70" wc for low draft

After adjusting the low pot fully CCW, the low draft reads @ -.43" wc

I will report my readings when I install the outside air kit.

 

[Tristan]

My flames are really high. Almost straight up. I would think that the ideal falme pattern for the XXV would be wide and mid height so that the heat exchangers are properly heated by the tips of the flame all the way across the heat exchanger. I aint no-pyro expert, but isn't the tip of the flame the hottest part of the flame? I think that this high flame is the result of high draft. My XXV is connected to the standard harman OAK. As far as the directions for that thing, all it says was to connect the pipe anf thats it. If I am understanding the operation of this stove correctly, I realize that the XXV is designed to run as efficeint as possible with minimal mingling by curious humans - however, regardless of the feed rate and all that knob controls, isnt it true that whatever amount of pellet being fed into the burn chamber, the resultant flame spread pattern is what really matters? - isn't that the initial source of any heat? i.e. if the flame is too tall and narrow its not heating the accordian baffles effieciently? Can some please rent me thier alcholic meter .... i mean their Magnehelic.

Thank you so much

 

[FireJumper]

I don't think this will be covered under warranty. It says something in the back of the manual under the warranty explanation that adjustments needed to keep the stove in "good operating condition" is not covered. They will probably charge you a service call to check this since you installed the unit yourself. I personally wouldn't worry to much about it.

 

[MrWinkey]

If you look on e-bay you can find a Magnahelic for around 30 bucks with shipping. I just bought one a few weeks ago....

My draft was .75 and .70 WITH the pot turned all the way down......I have nearly the same setup....21 feet of 4" pipe into an existing masonry.

I'm going to try to put the OAK on mine this weekend.

http://cgi.ebay.com/Dwyer-Magnaheli...4970942QQihZ003QQcategoryZ55825QQcmdZViewItem

Oh my low draft test is to close the door to the stove....then latch the latch slightly.....my stove will run with just the door closed but not latched......the further I press on the latch the higher the flames go....(this was pre magnahelic and quite barbarian)

Good luck!

 

[GVA]

You know if my stove had the test port on the back I would have had mine permanently hooked up, and watched the reading to tell me when to clean it, like in the picture above.
I think you would use it more than once to compare the initial install and then when you have a problem you can compare the readings.
If I still lived in MASS I would lend you mine but it is packed in a box somewhere I would have to look for days,and days to find it...
You're dealer could check it for you.

 

[MrWinkey]

I thought about leaving mine hooked up but it says in the gauge manual to not leave it hooked up to air hotter than 120 deg......

Perhaps they have another gauge for that but this one would not do it......

That's a spiff idea tho.....kinda like an boost/vac gauge for your stove? That would also be neat if I could put an EGT in too!

I cant wait to tell the wife that plan.....Yes dear we need an EGT for the stove.....

 

[GVA]

I thought about leaving mine hooked up but it says in the gauge manual to not leave it hooked up to air hotter than 120 deg......

Perhaps they have another gauge for that but this one would not do it......

That's a spiff idea tho.....kinda like an boost/vac gauge for your stove? That would also be neat if I could put an EGT in too!

I cant wait to tell the wife that plan.....Yes dear we need an EGT for the stove.....

It would be vacuum at that point so it would not be blowing hot air in the Mag.
There would need to be a transition to copper tube at the stove connection though that gets pretty hot.
I had mentioned the woodburners doing this on thier flues and they might be able to dial in thier fires easier, but they hve more stuff in the pipe to deal with plus higher temps. But if someone could do it say on a woodburners firebox then I'm sure it would work, and make the newb woodburners learn how to control thier stove quicker.
I'll try to dig up an old thread from MSG on this.. I'll be back.

EDIT*****
here it is
https://www.hearth.com/talk/threads/6748/

 

[Southbridge06GT]

Question for da pellet pros. How is a Magnehelic hooked up to a pellet stove to measure draft?

There is a bolt hole on the stove that you remove and insert the tube into.

Any idea where this bolt is on an XXV?

 

[Southbridge06GT]

Question for da pellet pros. How is a Magnehelic hooked up to a pellet stove to measure draft?

There is a bolt hole on the stove that you remove and insert the tube into.

Any idea where this bolt is on an XXV?

Anyone?