I think I may have too much draft WITH a damper

[Sean in the woods]

Hi again.
I my quest of a long efficient burn I found that I may have too much draft. The stove dealer came by today and installed a key damper. After this he measured our draft with the damper closed, the stove cold, the stove door closed and the fire not lit. It was a gusty day about 35 degrees. The heater was reading .04 wc to pegged passed .1 wc as the winds gusted.

Is there a chimney cap that prevents wind from creating a vacuum?

 

[rockettmantoo]

Hi again.
I my quest of a long efficient burn I found that I may have too much draft. The stove dealer came by today and installed a key damper. After this he measured our draft with the damper closed, the stove cold, the stove door closed and the fire not lit. It was a gusty day about 35 degrees. The heater was reading .04 wc to pegged passed .1 wc as the winds gusted.

Is there a chimney cap that prevents wind from creating a vacuum?

Maybe a barometric damper?

 

[Sean in the woods]

Maybe a barometric damper?

Already have a damper installed and it was fully closed during the test.

 

[Highbeam]

It is not unheard of to have two key dampers. Also, draft measurements on a cold stove are meaningless. Finally, you want the steady reading and not the gust of wind reading to be what you compare against the requirements.

Some chimney caps are marketed as being wind resistant but I believe that they are intended to prevent the wind from blowing down the chimney and smoking out your house.

 

[kennyp2339]

I really like this, this is a repost that a member put on here a few weeks back:
Florida Bungalow Syndrome (gulland.ca)

 

[Das Jugghead]

I modified both the intake and the flue in an effort to slow down my draft.

Pleasant Hearth WS 2417 Outside Air Intake Build

At the end of 2018 I purchased a Pleasant Hearth WS-2417 woodstove. That installation and subsequent learning process is described here: https://www.hearth.com/talk/threads/pleasant-hearth-ws-2417-install-challenges-questions-observations.173074/ Several issues have been on the list to...

www.hearth.com

I am still trying to fine tune it.

 

[bholler]

I had to run 2 key dampers at my old house to get the draft within spec when it was cold out

 

[kennyp2339]

I have 2 dampers on my bk princess, generally speaking when temps get below 20 I'll use the one damper at 100%, when a storm blows in the other one gets used in conjunction with the 1st key damper, works ok for me.

 

[Sean in the woods]

If I find I need a second key damper, does it matter how far from the first it is installed? Stacked? Or with a space between?

 

[kennyp2339]

If I find I need a second key damper, does it matter how far from the first it is installed? Stacked? Or with a space between?

I have space between mine, the first damper which hardly gets used is in the actual adapter collar for my dvl, the second collar is about 40" above due to the telescoping dvl (didnt want interference when sliding the pipe up and down) The idea behind the key damper is not so much as restriction, but a turbulence that it creates, it fools the stove into thinking is a lower draft.
FYI on the install for those that are wondering, I did mine DIY, I had to buy (2) key dampers (they were cheap at less then $10) I used the 6" plate and the longer rod (with a little bit of re-work bending) to get the proper length since it had to go through large od pipe.
Without the damper in effect I was bouncing between .1 & .15 when the maximum is .05 I was able to settle things down between .04 & .08 with the one damper which was a huge night and day difference in stove performance and control.

 

[bholler]

If I find I need a second key damper, does it matter how far from the first it is installed? Stacked? Or with a space between?

Mine were about 12 to 18 apart

 

[Sean in the woods]

The damper was installed today while the dealer was here testing the draft. Just finished a small load of 4 splits on a hot coal bed. This quick out-gassing would normally cause a runaway. This time it did not. Nice and even. It will be interesting see what a full load of oak does starting on a hot bed...

 

[Sean in the woods]

This morning a came downstairs to a healthy bunch of live coals in the stove . Moved into a N/S mound in the center, pu ton some kindling and (Ahh! smoke rolling out of the stove! oh yeah, new damper.) opened the key damper, loaded the stove full with 10 splits of oak and closed her up. After a 1/2 hour of monitoring and tweaking the air intake and the key damper were both closed and the stove was cruising in the 700's. 6 hours in and there are still lazy flames and have been no overruns.
Yay.

I think that the key damper may have solved the issue.

The next thing I want to do is try (within reason) to make it overrun. When this load burns down further, I'm going to not mound the coals down the center but spread them across the entire stove and put a full load on that. This is close to what I did the first time I lost control of it. I think that with all coals spread under the entire first layer of wood it was feeding more gasses in to the burn that the stove could handle because of the too strong a draft. At least that's my theory. I am hoping the key damper will give me that control I need. If nothing else, this experiment will tell me what not to do.

 

[begreen]

Getting back to the issue at hand, @Sean in the woods what kind of cap is on the chimney now and what brand stove pipe? How tall is the flue system on this stove? On a calm day, does the stove run well?

 

[begreen]

This morning a came downstairs to a healthy bunch of live coals in the stove . Moved into a N/S mound in the center, pu ton some kindling and (Ahh! smoke rolling out of the stove! oh yeah, new damper.) opened the key damper, loaded the stove full with 10 splits of oak and closed her up. After a 1/2 hour of monitoring and tweaking the air intake and the key damper were both closed and the stove was cruising in the 700's. 6 hours in and there are still lazy flames and have been no overruns.
Yay.

I think that the key damper may have solved the issue.

The next thing I want to do is try (within reason) to make it overrun. When this load burns down further, I'm going to not mound the coals down the center but spread them across the entire stove and put a full load on that. This is close to what I did the first time I lost control of it. I think that with all coals spread under the entire first layer of wood it was feeding more gasses in to the burn that the stove could handle because of the too strong a draft. At least that's my theory. I am hoping the key damper will give me that control I need. If nothing else, this experiment will tell me what not to do.

Yes, If a full-load of wood is superheated all at once, it is going to release a very large gas bloom. A lot of that will get wasted up the chimney. The key damper will give you more control, but only within reason. The operator is also a key part of safe stove operation.

 

[begreen]

Barometric damper discussion moved to its own thread.

 

[Sean in the woods]

Getting back to the issue at hand, @Sean in the woods what kind of cap is on the chimney now and what brand stove pipe? How tall is the flue system on this stove? On a calm day, does the stove run well?

The cap is nothing fancy. It is a flat disk on legs held about 5 inches above the pipe opening. Basically keeps the rain and snow out if it falls strait down.

Don’t know the brand of the chimney, it came with the house. The stove dealer said that it is double wall stainless steel. The stove pipe is also double wall and is 5 feet from the stove to the two 45 degree bends that form a dogleg that connects to the ceiling. No, I had the same symptoms on a calm day. Until the key damper was installed.

 

[Sean in the woods]

Yes, If a full-load of wood is superheated all at once, it is going to release a very large gas bloom. A lot of that will get wasted up the chimney. The key damper will give you more control, but only within reason. The operator is also a key part of safe stove operation.

In the interest of not polluting the local airspace, I think I’ll not do that experiment.

So, if it were really cold out and you had a full load that had burnt to coals and you wanted to start another full load to bank for the night, what would your method be? Push all the coals into a mound so only a couple of splits were in contact with them?

 

[begreen]

In the interest of not polluting the local airspace, I think I’ll not do that experiment.

So, if it were really cold out and you had a full load that had burnt to coals and you wanted to start another full load to bank for the night, what would your method be? Push all the coals into a mound so only a couple of splits were in contact with them?

This is a common scenario. It takes planning. I would place a couple 2-3" splits on top of the coals about 2-3 hrs before bedtime and move the air control to about 50% open. That will help burn down the coal bed while still providing heat. After an hour or so, the coals get raked forward to burn first. There are two options at this point. Load N/S for a full load or load the stove E/W for a not quaite as full load, but a bit slower burning. Once the wood has started to burn well (this could be in just 5 minutes) and the flue temp is around 600F, start turning the air down. How quickly will depend on the wood.

 

[Sean in the woods]

This is a common scenario. It takes planning. I would place a couple 2-3" splits on top of the coals about 2-3 hrs before bedtime and move the air control to about 50% open. That will help burn down the coal bed while still providing heat. After an hour or so, the coals get raked forward to burn first. There are two options at this point. Load N/S for a full load or load the stove E/W for a not quaite as full load, but a bit slower burning. Once the wood has started to burn well (this could be in just 5 minutes) and the flue temp is around 600F, start turning the air down. How quickly will depend on the wood.

Thank You!

 

[MR. GLO]

Hi again.
I my quest of a long efficient burn I found that I may have too much draft. The stove dealer came by today and installed a key damper. After this he measured our draft with the damper closed, the stove cold, the stove door closed and the fire not lit. It was a gusty day about 35 degrees. The heater was reading .04 wc to pegged passed .1 wc as the winds gusted.

Is there a chimney cap that prevents wind from creating a vacuum?

What did it read at 450 to 500 burn? and where did he stick his probe? and where did he install the damper (at the starter pipe area or further up?).
Did he measure draft before or after damper? Im not sure but think you want to measure before.

I am getting ready to test a Vacu-Stack and will keep you posted. I think the vacu-stack will help with the jumping of the draft readings but guessing it wont impact draft of chimney. I plan on installing a butterfly damper. I am having problems with not being able to turn the air control more than halfway. Otherwise I get white smoke outside and think the draft is pulling it up before it can burn on secondary.

 

[bholler]

What did it read at 450 to 500 burn? and where did he stick his probe? and where did he install the damper (at the starter pipe area or further up?).
Did he measure draft before or after damper? Im not sure but think you want to measure before.

I am getting ready to test a Vacu-Stack and will keep you posted. I think the vacu-stack will help with the jumping of the draft readings but guessing it wont impact draft of chimney. I plan on installing a butterfly damper. I am having problems with not being able to turn the air control more than halfway. Otherwise I get white smoke outside and think the draft is pulling it up before it can burn on secondary.

A vacustack will increase draft when it is windy. When you say white smoke are you sure it is smoke not steam?

 

[MR. GLO]

A vacustack will increase draft when it is windy. When you say white smoke are you sure it is smoke not steam?

thanks for the info. Have you tested this with a magnehelic draft gauge before burn and during a burn cycle with winds ? I thought the vacu-stack stopped the down draft and when wind increases it maintains the draft but I am not sure. going to test it and damper. I live in windy area and have a over .14 when burning.

 

[bholler]

thanks for the info. Have you tested this with a magnehelic draft gauge before burn and during a burn cycle with winds ? I thought the vacu-stack stopped the down draft and when wind increases it maintains the draft but I am not sure. going to test it and damper. I live in windy area and have a over .14 when burning.

The vacustack is for very specific problems caused by wind and yes it is designed to increase draft with wind which is why the name is vacustack. You just want a cap with a good wind band