Dual Fuel Chubby Stove

Re: Dual Fuel Chubby Stove

PostBy: JRLearned On: Fri Sep 13, 2013 1:59 pm

blrman07 wrote:I got confused with the preoccupation with the Cat. and it's temperatures.

The main question I have is have you changed the stove from a single fuel to a different single fuel? Or can you use the stove on wood and then go to coal and if so with what modifications? Since you have modified it to burn wood which requires over the fire air just like Bit coal, can you bypass the Cat and burn Bit coal in it?

You may have hit on something here if it really is dual or triple fuel with minimal work for changeover.



When the really cold weather hits, I'm going to unbolt the top casting and remove the combustor from the stove before burning anthracite. From what I've read coal gasses will erode the catalyst coating on the combustor, rendering it useless. The chamber will remain in place except the bypass is no longer useful and there's no catalyst. The chamber will still act as a baffle and heat exchanger to, in theory, increase surface area and capture more heat from the coal gas before it goes up the chimney. And, in theory, a slightly lower temp would be witnessed in the flue.

As for bit. coal, I have absolutely no experience with bit, so I don't know.
JRLearned
 
Stove/Furnace Make: Chubby Stove
Stove/Furnace Model: FrankenChubby

Re: Dual Fuel Chubby Stove

PostBy: JRLearned On: Fri Sep 13, 2013 2:11 pm

dcrane wrote:needs to reach 1000 degree's, yes that bypass damper should close tight upon reaching 1000, preheated secondary air into the chamber would be nice.

When you call these companies next time explain you are developing a dual fuel stove and need one of their cats shipped out to you (you would like maintain less than 3" thickness)... then... after that start getting into your subjects of how to design for their cat! ....your going to be buying them by the pallet! :clap:


Do you think the preheated air should be provided above the catalyst or below it? I put it just above the baffle, before the cat, assuming the smoke would mix with fresh air and then enter the catalyst feeding it for the burn. But, what I've seen is the secondary air (even though its up high above the baffle) was just feeding the primary combustion with air. I had a hard time keeping the primary combustion under control so I plug the secondary. What would the air still feed the catalyst if it were injected above the cat?

Tonight my plan is to cover the bypass damper completely (with a steel plate sitting on top of it). Since I'm burning bio bricks I don't think I have to worry about cresote clogging the catalyst by engaging it too early like that. This will be a good test since the rest of the chamber is sealed with gasket and the bypass is currently just a 5 1/2" leaky manual pipe damper sitting in a 6" collar. I'm thinking maybe you gotta really force the smoke up through the catalyst to get the 1000-1500 degree temps they claim to operate at.

If the test is successful then I'll redesign the bypass damper and come up with somethign better than a standard pipe damper. Maybe a heavy steel plate on a pin hinge, or something with a chain and crank.
JRLearned
 
Stove/Furnace Make: Chubby Stove
Stove/Furnace Model: FrankenChubby

Re: Dual Fuel Chubby Stove

PostBy: JRLearned On: Fri Sep 13, 2013 8:39 pm

Ok, capped the bypass damper completely, and closed off the secondary air tube. I also put a piece of sheet metal in the automatic draft box to cover up the intake completely and then put some big 'ol gasket in front of it to hold it in place a bit. Ash door vent closed 100% and even have a small piece of gasket around the shaker handle so it seats completely around the opening when pushed in. 2 1/2 hours so far on 6 bio bricks and the stove surface temp is at 500 degrees. The catalyst is putting out a constant 1000 degrees exactly.

I'm surprised I'm not getting the big temps the product literature claims, but very happy that I'm achieving a constant 1000 degrees for hours on end with no variance. It appears the catalyst burning is creating a super draft effect on the fire box. It seems like it's sucking oxygen from every little nook and cranny in the stove body: a big difference from coal where it'll go right out if you shut the intakes down completely.

So... better performance, definitely.

A note on cost of operation: Coal is by far more affordable on a hourly rate. If you burn a bag a day @ $6/bag, that's $0.25/hr. If I get 5 hours on 6 bricks @ $0.28/brick, that's $0.33/hr. But, it's not terrible for a cool night in the fall where you run it just to get a little heat in the house and let it go out overnight. Load it up again with 6 bricks at bed and you've spent $3.36.
JRLearned
 
Stove/Furnace Make: Chubby Stove
Stove/Furnace Model: FrankenChubby

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Re: Dual Fuel Chubby Stove

PostBy: dcrane On: Fri Sep 13, 2013 8:55 pm

nortcan wrote:
dcrane wrote:thank god you got rid of that VC that couldn't take 750 degrees inside the burn chamber without busting at the seams


To be honest with you or VC, the 750*F is on the top of the stove, on the center of the griddle, not in the secondary burn chamber where the temp. would be much more than 750*F.
Doug, just remember one thing about V.C. : they have the best ash pan system in the world :lol: . And a few other good points...and a FEW bad ones :cry:
Not the best stoves, specially the new ones having the Ever Burn systems (I got one of them...) or the even newer ones having 2 systems in the same stove: the Ever Burn system and the Cat.system in the same stove....


ohhh no... not the roll top desk again :down: Vermont Castings is ALL about bells, whistles and next year you might see some glittery tassels and a built in rotisserie to roast your Turkey toothy

@JRlearned... the preheated secondary air should go above the Cat


P.S. for those who dont know...Nortcan is one of my fav. bro's on the forum and we have fun sometimes :box:
dcrane
 
Hand Fed Coal Stove: Crane 404

Re: Dual Fuel Chubby Stove

PostBy: nortcan On: Fri Sep 13, 2013 10:20 pm

:lol: A good one Doug, did you say sometimes??????????? :blah: but :cheers: from Québec
nortcan
 
Stove/Furnace Make: Stuart,Peterson/ Grander
Stove/Furnace Model: Sunnyside/ Golden Bride

Re: Dual Fuel Chubby Stove

PostBy: JRLearned On: Sat Sep 14, 2013 8:54 pm

Today I cut and ground a more full fitting damper plate for the same rotary style damper. I also drilled a hole in the base plate near the catalyst and extending the secondary air pipe up through it into the upper chamber. I am able to better control the ferocity of the primary combustion now after covering the automatic draft damper intake better. I fired the stove up to 450 surface temp / 450 chamber temp above the cat and closed the bypass. I appeared to get "lift off" as the catalyst output shot up to 700 degrees. I closed the intake down and the surface temp has dropped down to 300 degrees. The cat is still chugging along at about 750 degrees. The secondary air is open, so whatever air flow a 1/2" black pipe provides is available in the upper chamber. Flue MPD is closed too, so the smoldering bio bricks are producing a lot of smoke. If I opened the door I'd get a big waft into the room.

I'm not getting the 1000 degrees I got before, but I have to assume the cat is doing its job. I don't think I'd be getting 750 degree temps in the upper chamber without it with the fire just crawling, but I'm not sure. Any thoughts that? I should probably pull the cat out and run it one night without it to measure the chamber temps and compare.

If I've learned anything so far it's that catalytic combustors are temperamental (what a pun). They're not so straight forward as you'd think. But that aside, my house is toasty and I'm getting some nice long burns on these bio bricks. It doesn't compare well to anthracite, but... aaaaahhhhh toasty :bighug:
JRLearned
 
Stove/Furnace Make: Chubby Stove
Stove/Furnace Model: FrankenChubby

Re: Dual Fuel Chubby Stove

PostBy: Freddy On: Sun Sep 15, 2013 6:51 am

Nice job! It's always fun to improve, invent, design.

I guess the only fear I might have is.... when burning coal, you have made a large "can" above the fire. If you somehow manage to have a "puff back", it might be a BIG one. Make sure ALL your pipes and connections ( the stove addition itself) are screwed together. If not a puff back can blow them apart, or blow them out of the chimney. Keep up the good work!
Freddy
 
Stoker Coal Boiler: Axeman Anderson 130 (pea)
Hot Air Coal Stoker Stove: Reading piece o' junk in the barn (rice)
Coal Size/Type: Pea size, Superior, deep mined

Re: Dual Fuel Chubby Stove

PostBy: JRLearned On: Mon Sep 23, 2013 8:41 pm

Ok, so I took the catalytic combustor out of the stove today and fired it up with bio brick to get a comparison of temperatures with and without. With the bypass closed the catalytic thermometer reads a steady 600 degrees with the stove surface temp at 400 around down on the side of the fire box. It appears that with the combustor at the same rate of combustion I am getting an extra 200-250 degrees of output on the catalytic thermometer.

Anyone have a rough calculation of how that added output converts to additional BTU of the stove? Franco B? You've always got the beat on combustion principles?
JRLearned
 
Stove/Furnace Make: Chubby Stove
Stove/Furnace Model: FrankenChubby

Re: Dual Fuel Chubby Stove

PostBy: JRLearned On: Mon Sep 23, 2013 9:01 pm

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JRLearned
 
Stove/Furnace Make: Chubby Stove
Stove/Furnace Model: FrankenChubby

Re: Dual Fuel Chubby Stove

PostBy: franco b On: Mon Sep 23, 2013 9:08 pm

I think you can only get the additional percentage of heat at that location. If the rise in heat is 200 degrees at that spot then it is probably putting out double the Btu but only in that spot and not total for the stove. You would need the area of the stove that displayed the higher temperature. Then use this chart to calculate.


80* ------------------------------------------------------ 15 Btu's / Sq.Ft.
100* ------------------------------------------------------ 51 Btu's / Sq.Ft.
150* ------------------------------------------------------ 168 Btu's / Sq.Ft.
200* ------------------------------------------------------ 315 Btu's / Sq.Ft.
400* ------------------------------------------------------ 1230 Btu's / Sq.Ft.
600* ------------------------------------------------------ 2850 Btu's / Sq.Ft.
800* ------------------------------------------------------ 5430 Btu's / Sq.Ft.
1200* ----------------------------------------------------- 9370 Btu's / Sq.Ft.
franco b
 
Hand Fed Coal Stove: V ermont Castings 2310, Franco Belge 262
Baseburners & Antiques: Glenwood Modern Oak 114
Coal Size/Type: nut and pea

Re: Dual Fuel Chubby Stove

PostBy: JRLearned On: Tue Sep 24, 2013 3:13 pm

franco b wrote:I think you can only get the additional percentage of heat at that location. If the rise in heat is 200 degrees at that spot then it is probably putting out double the Btu but only in that spot and not total for the stove. You would need the area of the stove that displayed the higher temperature. Then use this chart to calculate.


I think my statement about the same rate of combustion is technically innacurate as well. If the combustor is putting out additional heat in the form of an extra 250 degrees, some of that heat is transfering to the stove. And, if the stove is a little hotter, the automatic draft damper is closing a little bit more to compensate. Thus, with the combustor engaged, the stove has to be operating a slightly lower rate of combustion to achieve the same surface temperature as measured by the spring coil in the draft damper.

This all makes it very difficult to measure! :doh:

I think if I measured the surface temperature of the upper chamber, both with and without the combustor, I'd see some delta. Then, since I know the surface area of the upper cylinder, I'd be able to better calculate BTUs based on your chart here.
JRLearned
 
Stove/Furnace Make: Chubby Stove
Stove/Furnace Model: FrankenChubby

Re: Dual Fuel Chubby Stove

PostBy: franco b On: Tue Sep 24, 2013 4:00 pm

If the stove thermostat holds the stove temperature at a steady level with or without the combuster then the use of the combuster should result in a longer burn. Knowing the Btu value of the bricks and dividing the hours burned into that value would give the increase in Btu. Sort of. More like the percentage of efficiency gain.

Starting with a cold stove you could time how long it takes for a particular spot on the stove to fall to maybe 150 degrees and do this both with and without the combuster.
franco b
 
Hand Fed Coal Stove: V ermont Castings 2310, Franco Belge 262
Baseburners & Antiques: Glenwood Modern Oak 114
Coal Size/Type: nut and pea

Re: Dual Fuel Chubby Stove

PostBy: JRLearned On: Thu Sep 26, 2013 9:02 am

Franco B,
If the additional surface area provided by the addition of the upper chamber is 4.71 SQ Ft based on the dimensions, and the surface temp of the upper chamber is roughly 300 degrees on average, then does it stand that just adding the upper chamber provides an additional 3500+ btus to the stove's output. Based on the chart provided 300 degrees is about 750 BTU/SQFT, give or take. So forgetting the combustor and the automatic damper and rate of combustion, just adding this surface area to a Chubby stove increases the output significantly, right?
JRLearned
 
Stove/Furnace Make: Chubby Stove
Stove/Furnace Model: FrankenChubby

Re: Dual Fuel Chubby Stove

PostBy: franco b On: Thu Sep 26, 2013 6:49 pm

JRLearned wrote:Franco B,
If the additional surface area provided by the addition of the upper chamber is 4.71 SQ Ft based on the dimensions, and the surface temp of the upper chamber is roughly 300 degrees on average, then does it stand that just adding the upper chamber provides an additional 3500+ btus to the stove's output. Based on the chart provided 300 degrees is about 750 BTU/SQFT, give or take. So forgetting the combustor and the automatic damper and rate of combustion, just adding this surface area to a Chubby stove increases the output significantly, right?

If at the same burn rate as without the additional heat exchange area you are now adding almost 5 square feet of heat exchange then absolutely yes. Stack temp. should be much lower than before.
franco b
 
Hand Fed Coal Stove: V ermont Castings 2310, Franco Belge 262
Baseburners & Antiques: Glenwood Modern Oak 114
Coal Size/Type: nut and pea

Re: Dual Fuel Chubby Stove

PostBy: JRLearned On: Fri Sep 27, 2013 8:53 am

Here's an update on the effectiveness of my FrankenChubby. We've been in the 60's during the day and dropping to 45 overnight consistently. I've been loading the stove up before bed with about 8 bio bricks ($2.24). I could fit about 8 more if I wanted, but it's not that cold out. I get it going with the ash door damper wide open for about 20 minutes. Then I shut the ash door damper and set the automatic draft damper. The stove purrs along at about 350 degrees surface temp. Every day I've woken up to warm house in the morning. And while the fuel is mostly gone, a few small pieces remain and the stove is still at about 275 degrees surface temp. Bio bricks don't reduce to hot coals like cord-wood does. They keep smoldering with the texture of cardboard and reduce to a fine powder. All-in-all I'm very pleased with my decision to go dual fuel with the stove and I love not having to layer up clothes in the morning and sit in cold living room to drink my coffee. And I'll be damned if I give my fuel $'s to the Saudi by turning on the oil heat!
JRLearned
 
Stove/Furnace Make: Chubby Stove
Stove/Furnace Model: FrankenChubby

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