Pellet Stove Baffle Modification

I recently installed a new pellet stove of the Drolet (SBI-Quebec) Eco-45 variety. Using an exterior vertical flue and a fresh air intake kit, the stove is an excellent performer. Over the years I have spent some time successfully improving (tinkering with) wood stoves and wood furnaces to extract every available BTU from them. The balancing act was always to maximize heat transfer while keeping the flue gases hot enough to avoid the well-known problems, and to not overheat internal structures unless you really enjoy welding or replacing warped parts. So, it is wisdom born of experience that has so far kept the torch and hacksaw away from the new pellet stove. But naturally, I have to wonder about that baffle above the burn pot. The opening across the front of it is effectively a slot, maybe 12" x 1/2". That should keep the fire area hotter, and create turbulence as hot gases are forced up, back, and through the stainless steel heat exchanger above the baffle. But if the baffle were either removed, had some holes drilled in it, or the slot were enlarged to say 12" x 1", wouldn't the heat exchanger tubes reach a higher temperature (being careful not to overdo this) and thus be able to convey more heat to the air blowing through them? I can't wait to experiment with this. So my questions are: Has anyone learned any lessons from this kind of "tuning" of their pellet stove? Are there any gains (or losses I just don't foresee) to be had by altering baffle dimensions? Or, should I instruct my wife to hide all of the tools while I am not looking?

Thank you for sharing your thoughts.

I beat you to it on that advice. I'm already after those leaves. But I hear those tools calling me....

We have now been using the ECO-45 for ten weeks. We are heating 2200 square feet on two floors. We leave the stove on the lowest settings (1 or 2 of 6) during the day and overnight. If it is really windy and wet, so the chill goes right through the old bones, we run it on 3 or 4 to bring up the temp. We like about 65 degrees in the house. When it is 0 to 10 degrees outside, we run the stove on 4 overnight. It is installed in a south-facing sunroom with 250 sq.ft. of low-E glass. A fan circulates the heat into adjoining rooms.

I have explored most of the internals of the stove. Generally, it is thoughtfully designed and well made. Some of the welding appears to be done by hand, and some appears to be done by robot (no heartbeat), and all of it is well done. Good quality parts are used throughout the stove. There are numerous electrical safety interlocks covering every type of mechanical failure that could occur. It starts itself quickly, runs quietly, and does a very effective job of heating our home. While it deserves good marks for functionality, its performance and reliability are improved if you are a handyman.

Downside:
1. The air intake connected to outside air dumps cold air directly into the house.
2. Difficult access to the heat exchanger cleaner - have to remove cheap front grill that is awkwardly attached to the stove. Drolet could have run the cleaning rod through the grill and attached a knob like other stoves.
3. The shape of the fins in the cheap grill actually limits heated air flow into the room.
4. The blower is just adequate. A restrictive internal air path limits the air volume that can be passed through the unit for heat transfer.
5. The warm air exiting the front of the heat exchanger is highly stratified. There are two areas of high flow, and some areas of little or no flow.
6. Pellet volume goes from 1x up to 6x on the highest burn setting. Blower speed increases maybe 30% on the highest setting. The stove heats up beautifully on higher settings, but the increase in the volume of heated air entering the room is negligible.
7. Ten or more pounds of pellets stick in the hopper. We tried numerous tricks to make it empty by gravity, short of a physical modification, but the bottom sides just have too little slope.
8. On arrival, the steel was slightly warped at the top of door. This causes the gasket to leak air and the glass to dirty quickly. I checked it with a straight edge, and straightened it with a 6" wood block and a prying on it with a breaker bar.
9. The left-hand steel lip where the door hinges are mounted needs perhaps a 1" angle iron stiffener. The steel warps with heat, causing the top door hinge (carrying a heavy door) to slowly bend slightly outward and to the right. This spoils the door gasket seal on the left side and the top.
10. The electric igniter is marginal with the outside air intake installed. Minimize the air intake at startup - cold outside air slows or completely prevents ignition.
11. The door latch is a clever roller-based design, but it can easily be pushed too far past its stop and bent. This requires prying/hammering the hinge pins out and opening the door backwards to free the latch. If you want a tighter fit, remove the latch roller (drive out the pin with a small punch), turn the handle one full turn counter-clockwise, and reattach the roller. A simple wedge latch would have been far simpler and more reliable.
12. The pellet feed motor has a small puddle of oil under the gearbox. As long as it stays small, I will just check it periodically.


Upside:
1. No insurmountable problems if you clean the stove regularly, and perform simple maintenance.
2. No increase in electric bill versus oil furnace. The stove will run about 30 minutes on a Belkin 1250 VA UPS during a power failure.
3. The control electronics were smart enough to detect a reverse-wired outlet, which was easy to correct.
4. The oil furnace has remained OFF, and at current oil prices, can comfortably stay that way.
5. Heating cost cut by 65%. Greater savings in future years if oil stays high.
6. Once the house is warm, it stays warm.

Recommendations:
Sorry, my post is too big to fit.
Please see my next post for recommendations...

Continuation of previous post...

Recommendations:
1. Straighten out the fins on the air grill to minimize restriction and maximize hot air flow. Be gentle or the remaining thin steel might break at the ends of the fins. Touch up with high-heat black paint. If you are not into aesthetics, remove it, laugh at the way it is mounted, and then toss it in the garage until you want to show off your pellet stove.
2. Always drop the firebox baffle, then reach up inside and brush off the heat exchanger tubes when cleaning.
3. Straighten the steel where the upper door hinge is attached, with a hammer and wood block, once a week. Place the block to BOTH the left and the right of the hinge when hammering to straighten the steel where it is attached. Else the door hinge sag to the right will have the door hitting the bottom of the latch when closing the door. The hinge is cast - do not hammer it! Remove the door before hammering on the firebox. Do this when the stove is cooled down for cleaning.
4. Install the fresh air intake kit - it is not a perfect fit, so wrap it in insulation and seal off all of the remaining cold air leaks with adhesive weather stripping. You can order this Kit # AC02019 from Inventex at 1-800-363-0566.
5. Leave the side panels open slightly for more heat transfer off the sides of the hot firebox - always use a screen to keep children away.
6. Remove the screen from the blower motor to very slightly increase air volume - AND - to make it possible to dust out the fan with a brush and vacuum. If you remove the screen, be sure to replace the ring and tighten the screws!
7. Clean the stove 2 -3 times per week. Check your exterior flue pipe cleanout for collected ash periodically. We have emptied the bottom ash drawer 3 times in using just under two tons of pellets.
8. Finally, enjoy sitting in front of the stove and watching the snow fly!

I assume that none of the pellet stoves are perfect. They all have design strengths and weaknesses, and this one appeared to have a fair balance of them. So we got pretty much what we expected.

After splitting wood for years, for a first pellet stove, we are thoroughly enjoying our ECO-45! The bride is not too keen on the hammering thing, but hey, whatever it takes. Somehow I think she managed to miss out on all of the hammering and welding the wood stoves required!

Happy New Year!

Pete,

The Fresh Air Intake kit I mentioned is a clever little steel box that Drolet apparently designed as an afterthought. It attaches inside the stove, between the port (which, as you say, goes nowhere) and the side of the blower intake. The idea is to put that cold air into the firebox - not into the house. But like I mentioned, it is less than a perfect fit, so I plugged the holes with adhesive-backed weather-proofing foam, a little "Great Stuff", and then wrapped it in fiberglass insulation. It keeps a LOT of cold air out of the house. This is really only needed if you have the air intake ducted to the outside so the burner gets enough air in a tight house.

I like your duct work idea. I'm a believer. Put the heat where it's needed. And as much of it as possible!

Best regards,

Jim

If I recall correctly, the reference to the "door overlay" had to do with replacing the liner that the glass sits in. The book recommended having this done by the manufacturer.

Your reference to the "paper test" reminds me of how I determined why the glass was getting so dirty. I used a dollar bill and found that only the right side was snug. That is when I learned that the top edge of the door frame was bent in a full 1/16", and the left side of the door frame was bent out a full 1/16". With enough prying and hammering, I managed to get them perfectly straight, the seal became perfect, and the glass stayed clean. The top edge has stayed pretty straight, as it has about a 1/2" lip bent into it. The left edge warps outward and needs straightening once a week at cleaning time.

The firebox baffle is that piece of plate that you can push up with your hand, and lower off the ledges it sits on. The heat exchanger tubes above it get very crusty between cleanings.

Our glass stays quite clean too. Much cleaner than a number of pellet stoves I have seen. Each time I shut it off for cleaning, I vacuum off the inside glass, then use a single-edge razor blade (paint scraper) to scrape off the harder deposits (all of which come off instantly when warm), then I use Windex to instantly make that door glass shine. It is a pleasure to have so little of the problem that creosote causes with glass doors in a wood stove.

Because we draw in outside air through the burn pot, we are not pulling warm air out of the house. You have to buy the kit I mentioned to accomplish this. I usually set the intake draft to minimum at startup, and even though I don't touch it after that, the next time I restart after a cleaning, I find that it has opened itself about 1/3 to 1/2 way open. That seems to work perfectly, and we never see a blowtorch effect, or hurry the heat up the chimney.

Those "masonry-like panels" are inserts that look like bricks. They fasten in with those two screws you found. They are an extra-cost option that does not come with the stove. I do not have them either, because I know from seeing other stoves that after one day of use, they look more like a "charred mess" than "bricks".

One more thing I forgot to mention previously. With the right side of the stove open while running, you can feel a draft coming out of the under side of the plenum to which the blower is bolted. Actually, both sides of the plenum have a 1/4" crack under them, and a lot of air that should be going through the stove leaks out from under it. Use some high-temp RTV to seal up those cracks and send the air through the heat exchanger.

No doubt about the stove. It is capable of providing excellent service. It was 5 degrees here this morning, and it ran all night on setting 3, keeping the house comfortable. As for the service guy, I expect you are likely to see the same service guy I would use. In the mirror.

Best regards.

Silicone spray doesn't help. Nor does burnishing the bottom slopes to make them as slick as possible. There just isn't enough slope in the bottom sections of the hopper to let the pellets gravity feed into the auger. They get in their own way and block each other until the stove goes out. You have the solution we use. Heap the pellets up in the middle from time to time. I do have an idea that will solve this, but no time available to cobble it togeher at the moment.