Forced draft OWB to natural draft?

ButchC · February 05, 2018, 04:37:35 PM

I have been running a 4400 woodmaster for 10 years and have always burned dry split wood. Has always seemed to me that the forced draft was set up for burning wet wood in big chunks, way too much air. So, after thinking about it all these years today I put a switch on the draft fan , currently burning on the draft from the stack. Anyone else done this? I will report results if there is interest.

Gearbox · February 05, 2018, 05:26:37 PM

My fans have a rheostat and burning dry wood I keep it on low speed .

Don P · February 05, 2018, 05:53:05 PM

Without forced draft you can probably adjust natural draft with some stack height.

ButchC · February 05, 2018, 06:29:44 PM

I have 6 foot of stack on it. It's 19 here and washing machine is runnning, we heat the domestic too. Draft was open for 1 1/2 hours to reach cut off temp. Usually 15 minutes with the fan. Should be able to come to some sort of conclusion about wood usage fairly quickly since I know the thing pretty well.

thecfarm · February 05, 2018, 08:53:45 PM

I have a Heatmor,no natural draft with one of these. My fire would go out with the blowers. The fans don't come on,it can't get no air. This allows me to burn dead cedar and not have a boil over.

E Yoder · February 05, 2018, 08:59:06 PM

Slow burning may creosote up on you..what I've seen is if the stack height isn't high enough to create adequate draft, moisture will tend to condense on the door jambs, chimney, or any other cool spot.
Rust follows if it's mild steel.
Just something to keep an eye on.
Another option might be to use a piece of sheet metal to throttle the intake of the fan to allow an exact amount of air in.

dave_dj1 · February 06, 2018, 05:04:34 AM

I am from the natural draft camp. I think once you learn to regulate the temp of the water according to heat loads and outdoor temps you will find that you use considerably less wood. You may have to install some sort of manual control to introduce some draft. I have a friend that has an Aquatherm boiler in his garage shed that heats his house, it has a blower, I talked him into drilling a 1/4" hole in the door for a draft and he loves it, the blower will still come on occasionally but for the most part it gets enough draft between the hole in the door and what leaks in around/through the blower.

Gearbox · February 06, 2018, 10:23:06 AM

Be careful of a draft that doesn't shut completely off . I went out to fire mine one morning and a solenoid had stuck . The boiler was just starting to boil in the cross tubes . There was enough draft to spin the blower cage . Uncontrolled air in a boiler is a no no . You just can't watch it close enough . Mine shuts off tight and still will over run by 5 to 10 degrees in the spring and fall .

jwh f-100 · February 06, 2018, 12:14:05 PM

Quote from: ButchC on February 05, 2018, 04:37:35 PM
I have been running a 4400 woodmaster for 10 years and have always burned dry split wood. Has always seemed to me that the forced draft was set up for burning wet wood in big chunks, way too much air. So, after thinking about it all these years today I put a switch on the draft fan , currently burning on the draft from the stack. Anyone else done this? I will report results if there is interest.

OMG. funny this has came up. I also have a 4400. And have been thinking and talking about the same thing.

My next door neighbor, who is a intelligent heat and boiler guy, has a central boiler. I know for a fact ( controlled damper only) it burns wood better than my WM.. When he's been out of town I fill it for him. His ash is literally dust compared to mine which contains a good amount of waste.

My blower cover is removed from my WM. When it is real cold, and I know it wont overheat, I place a small sliver of wood under the flapper allowing a little air to enter (when the flap fully open the sliver falls on the ground) . When I later look inside I can clearly see how much better the coals burn down..

I am considering adding a second aqua stat to operate the fan only, leaving the flapper controlled by the WM components. The flapper would open first. The fan would only kick on if the temp got real low..

I thought about adding male and female cord plug in the wire to the fan but a switch is a good idea..

I also agree with the uncontrolled draft. Not a good idea. My WM flapper dry rotted and tore. It overheated and almost ruined my boiler..

LAZERDAN · February 06, 2018, 12:38:54 PM

Hello
I also have a 4400 WM , I did put a switch on the blower motor last year. I thought just like you and played around for a year. I dicked around and found I liked it with the draft fan to run, did not find that much savings (woodwise). The one thing that scares me . Every once and a while I boil the water inside. Has not hurt anything

jwh f-100 · February 06, 2018, 03:00:37 PM

Quote from: LAZERDAN on February 06, 2018, 12:38:54 PM
Hello
I also have a 4400 WM , I did put a switch on the blower motor last year. I thought just like you and played around for a year. I dicked around and found I liked it with the draft fan to run, did not find that much savings (woodwise). The one thing that scares me . Every once and a while I boil the water inside. Has not hurt anything

Maybe your door seal of the rubber flapper need attention. It shouldn't overheat.

ButchC · February 07, 2018, 10:41:43 AM

Hi all, I have a couple days in now and a little bit of information. Shut off the fan late in the day, everything seemed to be OK but woke up to the the furnace being on low limit, :( shucks. Was mid teens that evening, three people taking showers and wife ran two loads of wash. So I reset the control and turned the fan on and went to work. Yesterday evening I made up an adjustable block for the fan intake and installed it. Dont judge me too harshly on the fab work, I have learned to not spend to much time perfecting things when I am on a wild hair if you get my drift? Anyway temps were basically the same last night, same number of showers, same number of washing machine cycles as the night before. Woke up to 165 system temp and everything going fine. As far as I can tell there is more than a little bit of wood savings, but that is based upon one night and it will take a bit to know for sure. I am burning three year old split wood that has been under cover, dry as a bone. As it would appear right now it seems that an adjustable draft would be the hot set up? Warm days dry wood = less, colder days wet wood = more? I am also with the comment made about timing out the fan after a given period. I have seen the thing blowing flames out the stack many times when there was a high demand on it, not chimney fire flames but from the firebox and it has to be wasted BTUs??

thecfarm · February 07, 2018, 02:42:18 PM

Where's your chimney? Straight shot right from the fire box? Heatmor has to travel the length of the fire box,exits above the feed door,than travels to the back of the stove through a 3"X 6" rectangle tubing than out the chimney.

jwh f-100 · February 07, 2018, 03:13:21 PM

You may be on to something with that concept. I'll be watching for your results.

Be aware the flapper may not seal up properly and cause a overheating situation..
Maybe cut a piece same size as the flapper with a hole in it, that way it will seal properly..

E Yoder · February 07, 2018, 03:25:16 PM

Extra baffles in the exhaust is what you need if you have flame out the top. Too short of an exhaust path.

Dave Shepard · February 07, 2018, 03:56:35 PM

I force draft my Classic every now and then with my Milwaukee M18 blower, but only when I'm in a hurry to get things burning again if the fire goes out. You can get a two foot long blow torch flame coming out the front. I call it dragons breath.

ButchC · February 07, 2018, 04:34:50 PM

Quote from: thecfarm on February 07, 2018, 02:42:18 PM
Where's your chimney? Straight shot right from the fire box? Heatmor has to travel the length of the fire box,exits above the feed door,than travels to the back of the stove through a 3"X 6" rectangle tubing than out the chimney.

All old school woodmasters are a round firebox with the chimney out the top at theb
rear. Just below the top there are retangular tubes running sideways and the is a by pass gate so the exhaust must come.forward, then back around the tubes and out.

ButchC · February 07, 2018, 04:41:54 PM

Quote from: jwh f-100 on February 07, 2018, 03:13:21 PM
You may be on to something with that concept. I'll be watching for your results.

Be aware the flapper may not seal up properly and cause a overheating situation..
Maybe cut a piece same size as the flapper with a hole in it, that way it will seal properly..

Yessir, it is not a perfect seal right now but it's cold enough that the leak isnt causing issues. I am going to toy with the crude set up a while before I invest in permanent type fixes. Just came from peeking in the firebox and was surprized how much wood was left, last filling was 22 hours ago. Happy so far

jwh f-100 · February 07, 2018, 04:57:02 PM

Quote from: ButchC on February 07, 2018, 04:41:54 PM
Quote from: jwh f-100 on February 07, 2018, 03:13:21 PM
You may be on to something with that concept. I'll be watching for your results.

Be aware the flapper may not seal up properly and cause a overheating situation..
Maybe cut a piece same size as the flapper with a hole in it, that way it will seal properly..
Yessir, it is not a perfect seal right now but it's cold enough that the leak isnt causing issues. I am going to toy with the crude set up a while before I invest in permanent type fixes. Just came from peeking in the firebox and was surprized how much wood was left, last filling was 22 hours ago. Happy so far

Your switch sparked an idea for me. I'm gonna keep my eyes open for a strap on aqua stat. Attach it just past the circulator pump. Wire it to the fan and set it below the fan as I mentioned above..

ButchC · February 07, 2018, 08:01:04 PM

You might want to check the ETC unit. It may have the capibilities to run them seperate. I know there are extra terminals on it. I don't do well with electronic gizmos myself

ButchC · February 08, 2018, 08:23:29 AM

Another day on choked draft.
I am heating a large 2 story 1900ish farm house with some insulation and newer windows. Temps yesterday were lows in teens and highs were mid 20s with some wind but lots of sun. The furnace went 24 hours on one 80% loading with wood to spare, guessing another 12 hours. Definitely would not have done that on full draft. Wood savings is definite at this juncture but exactly how much is not easy to calculate, I do know that before I choked the draft it would NOT have made 24 hours on one filling in those conditions, let alone have wood left over for another 8-12 hours.

Wood Shed · February 11, 2018, 08:22:04 PM

Hard to compare OWB performance with so many constantly changing variables. There are some constants I strive for while operating my CB 6048 (12th season) with forced air draft. They are:

1. maintain contant temp range 170-180 degrees.
2. fire every 12 hours depending on anticipated heat load
3. produce a clean burn with a minimum of offensive smoke
4. enjoy the entire process from wood selection to ash removal

Much easier to do now that I am retired and priorities change.

Kwill · February 11, 2018, 08:31:55 PM

This is my draft on my homemade outdoor wood burner. It is controlled by the thermostat in the house. When the house calls for heat the draft door opens when the house gets up to temp it shuts. It has worked good. I often considered adding a pusher fan but I was worried about sparks coming out the stack.

ButchC · February 12, 2018, 09:08:52 AM

Quote from: Wood Shed on February 11, 2018, 08:22:04 PM
Hard to compare OWB performance with so many constantly changing variables.

Yessir, and that is why I have not made any definitive statements,,,yet. I too enjoy the entire process. We burned a bit of wet wood the 2nd year when we ran low and WOW does that ever increase the amount burned! This is our 10th year operating the 4400 but at two residences. It does create a bit more smoke since the draft was reduced and that would be a consideration if anyone lived near enough to us to be affected.

We are into week two with the draft opening reduced about 75%. At this juncture the only definitive thing I have to say is we are definitely saving wood and not in small amounts, at least one arm load a day but less than two arm loads. Temps have moderated here a bit highs above freezing. I am running 24 hours on about 50-60% loads presently where as with full draft I would have needed to be almost full loading to go 24 hours.