Shelter wood furnace upgrade/Improvement

[Medic21]

Have you gotten better burn times yet? I recently bought the shelter sf3100 and havent been overly impressed...im getting 4 hour burn times which is what i was getring with my antique hotblast from tractor supply 10 years ago. Got this one thinking it would be better but hasnt yet made me feel like it was a great decision. When the draft blower kicks on i burn through wood way to fast and if its off its way to cold. I cant find a happy medium at all. Adjusted the draft blower preset damper piece a few times but same results. Also if i pit more than 2 pieces of wood in the shelter the firebox gets cherry red and ill even get some glow at the upper front of the door. The old hotblast i could cram that baby full and not have an issue

Here is what I have found out with the SF1000 so far.

Do not load it with a good bed of coals when the stat is calling for heat with the inducer running nonstop. You will get the top of the door glowing like your talking about and burn through your wood in no time. Get the load charred with the door cracked and I watch the flue temps around 500 internal. Shut the blower off and let it heat up the house. Turn the blower back on when the temp Is raised to the stat setting. With ash, elm, and oak it holds a flue temp around 300 after that and the inducer does not come on for a couple hours. I can get 4-5 hours when it's below 10 degrees out and I have gotten 12 hours at 35 degrees out over night.

At the suggestion of another member I lowered the circulation fan on temp to 140 and it produces heat a good hour longer now. I have a bunch of larger splits, 8"-10" that fit three across with two layers in the fire box once it's going.

I am going to check the flue this weekend, calling for 50+ on Saturday. If I see a large creosote issue I'll let you know. Hope this helps. I'm very satisfied with the furnace even though it has some quirks I don't like.

 

[Lawson111]

This is the one I like, very accurate at least compared to the magnetic stick on crap:

https://www.teltru.com/p-272-big-gr...ter-lt225r-5-inch-stem-2001000-degrees-f.aspx

Just don't peg it at 1000F, I did that once and then it didn't read right after that.

What’s wrong with the magnetic ones? Are they low or high on temp? And with the one you suggested do you just drill a small hole in the pipe and place this in there?

 

[3fordasho]

What’s wrong with the magnetic ones? Are they low or high on temp? And with the one you suggested do you just drill a small hole in the pipe and place this in there?

I've had several of the magnetic ones on the same heated surface right next to each other and they can be 100-150F off from each other. On the surface of your connector pipe they might be ok on a single wall pipe, but useless on the double wall stuff (only thing I use). They are slow to respond to temperature changes, I've had flue temps on a Woodstock fireview go from 300f to 1000f in a matter of minutes on a reload or cold start when the bypass was open.

For the tel-tru probe thermometer I've simply drilled through both walls of the double wall connector pipe, just slightly larger than the diameter of the probe, then used a small dab of high temp silicon to seal it up and it's enough to hold it in place. The silicon is the bronze colored automotive type good for 700F+.

The tel-tru's have tracked well with the thermocouple / digital controller I've installed for more sophisticated control of flue temps.

I mentioned that I pegged one at 1000F and it was off after that, I forgot to say it was fixable, there is a calibration nut on the back, loosen it, put the probe in boiling water, set dial to 212F, fixed.

 

[maple1]

What’s wrong with the magnetic ones? Are they low or high on temp? And with the one you suggested do you just drill a small hole in the pipe and place this in there?

Magnetic pipe temp guages are pretty well garbage IMO. They can be inaccurate from one to the next as last post says, and they greatly underestimate internal pipe temps. I have one, right beside a probe guage. The magnetic reads 100c less than the probe when burning. That might lead to someone trying to push up their pipe temp going by one of those, when it's already hot enough inside. So IMO they can also be dangerous, especially if combined with someone new at wood burning or with not-ideal practices or especially unseasoned wood.

 

[Lawson111]

I've had several of the magnetic ones on the same heated surface right next to each other and they can be 100-150F off from each other. On the surface of your connector pipe they might be ok on a single wall pipe, but useless on the double wall stuff (only thing I use). They are slow to respond to temperature changes, I've had flue temps on a Woodstock fireview go from 300f to 1000f in a matter of minutes on a reload or cold start when the bypass was open.

For the tel-tru probe thermometer I've simply drilled through both walls of the double wall connector pipe, just slightly larger than the diameter of the probe, then used a small dab of high temp silicon to seal it up and it's enough to hold it in place. The silicon is the bronze colored automotive type good for 700F+.

The tel-tru's have tracked well with the thermocouple / digital controller I've installed for more sophisticated control of flue temps.

I mentioned that I pegged one at 1000F and it was off after that, I forgot to say it was fixable, there is a calibration nut on the back, loosen it, put the probe in boiling water, set dial to 212F, fixed.

My magnetic one is on single wall pipe. I use single wall pipe until it connects to my thimble. I did this because the heat that comes off the pipe is enough to keep the basement warm which keeps my floors warm.

I just put it in boiler water and it reads 25-50f hotter than boiling water. I can live with that...

 

[Lawson111]

Magnetic pipe temp guages are pretty well garbage IMO. They can be inaccurate from one to the next as last post says, and they greatly underestimate internal pipe temps. I have one, right beside a probe guage. The magnetic reads 100c less than the probe when burning. That might lead to someone trying to push up their pipe temp going by one of those, when it's already hot enough inside. So IMO they can also be dangerous, especially if combined with someone new at wood burning or with not-ideal practices or especially unseasoned wood.

Hmmm maybe I’ll buy the one @3fordasho suggested and give it a shot. It will be ok to install on single wall pipe right?

 

[maple1]

Should be Ok yes.

If you do get it, post up some comparison numbers. We can add that to the 'hmm that's interesting' pile.

 

[3fordasho]

Hmmm maybe I’ll buy the one @3fordasho suggested and give it a shot. It will be ok to install on single wall pipe right?

Yes it will work fine. I'd be less likely to use the high temp silicon to secure it on single wall, you might exceed the high temp rating. In my case the silicon is on the outer layer of the double wall that does not get near as hot.

Couple options to try, drill hole same size as probe diameter and hopefully a slight interference fit will be enough to secure, I've also taken a short length of brass threaded rod, maybe 3/4" long, drilled a hole thru for the probe, then tapped a hole in the pipe to match the treaded rod thread size.

 

[Lawson111]

Yes it will work fine. I'd be less likely to use the high temp silicon to secure it on single wall, you might exceed the high temp rating. In my case the silicon is on the outer layer of the double wall that does not get near as hot.

Couple options to try, drill hole same size as probe diameter and hopefully a slight interference fit will be enough to secure, I've also taken a short length of brass threaded rod, maybe 3/4" long, drilled a hole thru for the probe, then tapped a hole in the pipe to match the treaded rod thread size.

I’m a little confused on the threaded rod idea... could you explain more?

 

[3fordasho]

I’m a little confused on the threaded rod idea... could you explain more?

Ok, I've got to remember not everyone has access to a metal lathe

There are brass hose fittings that will work, I've something like this : https://www.mcmaster.com/#5346k11/=1b73hxf

and simply drilled out the center hole to match the diameter of the probe on the tel-tru. you'll need to tap your pipe for 1/8 pipe thread which is pretty common.


There is also a clip that comes with the tel-tru that is used to secure it to the big green egg grill.
This could also be used but that clip would reside inside the pipe, so access is an issue and it could also collect fly ash or other build up.

 

[tomtom85]

So is the sf1000 worth the money? thinking of putting one in this summer

 

[Medic21]

So is the sf1000 worth the money? thinking of putting one in this summer

So far, yes. Really hard to give an answer on that. We have had a colder than normal winter so with it being sized for the house on a normal winter it doesn't keep up like I'd like it to on the single digit nights and days. That said in the 20s daytime andnim getting 9-10 hour burns while I'm at work. I can go 6-8 hours at night in the teens. Our normal for this time of the year is 34 high and low 20s low.

That said it is clean and efficient. I have still used 30%-40% less wood this year. I also have used only about 50gal of propane since Jan. My only comparison though would be electric since I put the propane and central air in this last summer. My electric bills dropped from $600+ to $150. I'll post a complete pros and cons review this spring when I'm done burning.

Edited to change 100gal to 50gal. I had a 1000 tank forever now 500.

 

[Debold]

I have had my shelter furnace for 3 years now. Never really had any serious issues with it besides trying to keep the door handle adjusted properly but that’s not a huge issue.

What I would like to try though is instead of the air induction fan running off a thermostat in the house is there a way to hook that up to the blower thermostat? Or something similar maybe using a separate thermostat that monitors plenum heat. Really trying to get longer burns with this stove so I was trying the think of a way to set it up similar to a wood boiler where the induction fan will kick on when it calls for heat. But In this case when the fire box gets to a certain temp have it kick on to heat the fire up and turn the blower on.

I know this is supposed to work off a house thermostat the same way but I have had no luck with it. I have to choke the fire down so much in order to get this to work resulting in bad creosote and even puff backs.

Right now I don’t even use that induction fan I just monitor flue temps with a magnet thermometer on the stove pipe and adjust air intake with the bottom ash pan knob and plate on the side of the induction fan. Running it this way I burn a lot of wood and my house is 80 because the blower fan is constantly running because I try and keep the fire hot enough to not make a ton of creosote. It sucks having to clean the chimney every two weeks!

Any input or ideas would be great
Maybe someone with a shelter furnace can help me get this thing setup to burn and run the way it was designed!

Thank you!! Sorry for the long read.

This is to everyone wishing for longer burns. I have owned the larger shelter outdoor unit for 5 years. Stop using the induction fan. Leave the thermostat switch off. Close the cover on the fan. I typically only use the screw style air intake until temps get to single digits or below. Then i open the slide on the inducer fan 1/8th inch at a time. I get 8 to 12 hours burn time if loaded correctly. My log cuts are around 18 inches. I stack neatly in the back. Then cross stack the front with any shorter pieces. Hope this helps someone.

 

[Medic21]

This is to everyone wishing for longer burns. I have owned the larger shelter outdoor unit for 5 years. Stop using the induction fan. Leave the thermostat switch off. Close the cover on the fan. I typically only use the screw style air intake until temps get to single digits or below. Then i open the slide on the inducer fan 1/8th inch at a time. I get 8 to 12 hours burn time if loaded correctly. My log cuts are around 18 inches. I stack neatly in the back. Then cross stack the front with any shorter pieces. Hope this helps someone.

In the SF1000 and the FC1000 this will not work at all. It needs much more airflow than this will allow. That is the whole problem with it.

 

[Debold]

In the SF1000 and the FC1000 this will not work at all. It needs much more airflow than this will allow. That is the whole problem with it.

So medic, ive looked at the design on these smaller indoor units. My subtle suggestion is to install a damper and run it 3/4 closed. I recently did this on mine and im thoroughly impressed. After 10 to 12 hours, i wake up to 3 unburnt logs and plenty of heat. This shouldnt have an affect on the inducer motor system as it can force the smoke through the damper. The result should be a satisfies thermostat and much longer blower runs with hotter air temps. A damper is 8 dollars and easy install. Well worth the experiment.

 

[Mrpelletburner]

My subtle suggestion is to install a damper and run it 3/4 closed.

Does this help keep the heat in the firebox? Hotter firebox = longer secondary burn?

 

[Debold]

Does this help keep the heat in the firebox? Hotter firebox = longer secondary burn?

I am playing with a damper for the first time on my outdoor unit. Thus far, i must wait for the fire to flare up nicely before closing the damper. I only close ot halfway. Im getting hotter air for an average of 12 hours. Typically in the morning i still have 2 logs that are barely burnt. If i close the damper much further, it kills the fire. Im very happy i tried this. Heres the trick. I have tripple wall stainless pipe on the stove. To install a damper you have to buy a 6" and install it on the rod from a 8". It takes a little engineering but it can be done.

 

[Medic21]

So medic, ive looked at the design on these smaller indoor units. My subtle suggestion is to install a damper and run it 3/4 closed. I recently did this on mine and im thoroughly impressed. After 10 to 12 hours, i wake up to 3 unburnt logs and plenty of heat. This shouldnt have an affect on the inducer motor system as it can force the smoke through the damper. The result should be a satisfies thermostat and much longer blower runs with hotter air temps. A damper is 8 dollars and easy install. Well worth the experiment.

It has good burn times in normal weather. The problem is it is choked down to an opening of 3/8”X2” along with two 1/2” to draw intake air. Roughly a 2square inch opening is all it has to draw air from at an idle. With the inducer running it supplies considerably more air. The 6inch outlet does not effect draft so a damper is a mute point, especially with the baffle.

 

[Mrpelletburner]

It has good burn times in normal weather. The problem is it is choked down to an opening of 3/8”X2” along with two 1/2” to draw intake air. Roughly a 2square inch opening is all it has to draw air from at an idle. With the inducer running it supplies considerably more air. The 6inch outlet does not effect draft so a damper is a mute point, especially with the baffle.

Basically because of the “fixed intake air” the draft doesn’t matter?

 

[Medic21]

Basically because of the “fixed intake air” the draft doesn’t matter?

Draft matters absolutely. 28 square inches outlet will only flow what comes in. If draft is good closing off the flue has no different effect than closing down the intake.

 

[Mrpelletburner]

Draft matters absolutely. 28 square inches outlet will only flow what comes in. If draft is good closing off the flue has no different effect than closing down the intake.

What would you consider a good draft? What would be to much of a draft?

For example without a bd installed, I am seeking the draft hit -0.2” wc.

 

[Medic21]

What would you consider a good draft? What would be to much of a draft?

For example without a bd installed, I am seeking the draft hit -0.2” wc.

If it burns it has good draft. If it doesn’t burn it doesn’t have good draft. I don’t live by instruments at all.

I can open the door on my furnace and fire will immediately rage away. That means I have adequate draft. Just like a structure fire and closing your bed room door, limit or interrupt that flowpath of a fire , the draft, and fire doesn’t burn.

 

[maple1]

If it burns it has good draft. If it doesn’t burn it doesn’t have good draft. I don’t live by instruments at all.

I can open the door on my furnace and fire will immediately rage away. That means I have adequate draft. Just like a structure fire and closing your bed room door, limit or interrupt that flowpath of a fire , the draft, and fire doesn’t burn.

Too much draft isn't a good thing though.

 

[Mrpelletburner]

If it burns it has good draft. If it doesn’t burn it doesn’t have good draft. I don’t live by instruments at all.

I can open the door on my furnace and fire will immediately rage away. That means I have adequate draft. Just like a structure fire and closing your bed room door, limit or interrupt that flowpath of a fire , the draft, and fire doesn’t burn.

Everything I have read states...

To much draft and you risk damaging the unit.

To much draft and you will go through fuel faster.

I am guessing what you are suggesting is because the primary air is “fixed” the draft doesn’t matter as you can only pull X amount of air through the opening? This where these newer models differ from an adjustable primary air adjustable damper?

 

[brenndatomu]

If it burns it has good draft. If it doesn’t burn it doesn’t have good draft. I don’t live by instruments at all.

I can open the door on my furnace and fire will immediately rage away. That means I have adequate draft. Just like a structure fire and closing your bed room door, limit or interrupt that flowpath of a fire , the draft, and fire doesn’t burn.

Yeah, that isn't right at all. You never cut off incoming air 100%...or your fire would go out. So if you are running high draft, its pulling more air into the fire than what is supposed to be (at any given setting) and if the furnace has a fixed opening like the new FC do, you are gonna overfire in a heartbeat with -0.2" draft!
Even Kuuma, with their precision computerized air control, still stresses the need to control chimney draft to -0.04 to -0.06" WC...they even come with a Fields baro.