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Shaver Furnace / How I improved my shaver boiler model 290
« on: September 27, 2013, 09:37:17 AM »
I bought my outdoor wood boiler in 2008 and have had a series of issues I wanted to address to make the boiler more user-friendly and efficient. Below you will find a series of images and descriptions documenting this process.
The boiler originally shipped with a rather rudimentary temperature control system consisting of a surface mount thermostat that cycled an electric blower on and off, and a manually adjusted draft door on the blower. I had a very difficult time regulating the temperature. I had frequent boil-overs and wide swings in water temp. I addressed the problem by adding a dry well, a solenoid, and a two stage digital aquastat that is set as follows:
180* - blower off and damper closed
<180* but >=175* - blower off and damper open
<175* - blower on and damper open
The idea is to only use the blower when needed, as it forces hot air out the chimney and wastes heat.
The second issue I faced, was what I personally define as “poor insulation”. The boiler used some type of fiberglass batting on the to and sides, and nothing on the bottom of the water jacket. I decided to strip the tin, and ultimately the framing from the boiler and prep for spray foam. I was a bit disappointed to find the outer shell of the water jacket also had no paint and was beginning to rust:
I also discovered the water jacket was not welded solid around the top of the boiler, which essentially left me with a 50 gal air space above the water level:
I sandblasted the boiler, welded the gaps, and sealed the welds with polyurethane roofing sealer for good measure, then painted the boiler and tacked on studs to attach tin:
I also cut and threaded the overflow pipe on the side to direct it up through the roof and reclaim that unused 50 gallons of airspace for water storage.
Before I welded that ridiculous inspection cover in place, I added a couple 90* and a few pieces of pipe to the inside of the return pipe to direct the water to the front of the boiler and promote better circulation. Unfortunately I forgot to take pictures of this step.
Once this long and laborious process was complete, I was ready to have the boiler insulated with closed cell spray foam. I kept the foam away from the door and chimney area, I used rock wool high-temp insulation for those areas, along with in-between the inner and outer firebox door panel:
The single wall chimney was also a source of problems for me. At least twice during the winter it would clog up and I would have to climb onto the shed roof and attempt to clean it out. I decided to cut the existing chimney off about 12” above the tank, and bought some nice triple wall insulated pipe and a cap. I reused most of the existing tin, but had to buy a few corner pieces and covered the furnace
I added a switch to cut the power to the damper and blower while loading the stove:
Since I spray foamed the bottom of the boiler and the hot coals sit in the ash pan and could potentially melt the foam, I thought it best to line the ash pan with half-height firebricks. These bricks also raise the floor of the firebox even with the bottom of the cleanout door, which is a nice benefit.
I think I may also experiment with lining the floor and possibly the firebox walls with firebrick in an attempt to raise combustion temps and further improve efficiency. I’m going to experiment with a secondary burn air tube plumbed from the ash pan area, up along chimney, and along the ceiling of the firebox. I’ve drilled a series of holes in the pipe that runs along the firebox ceiling in hope that the air will help ignite the wood gasses and initiate a secondary burn. I’m not fully sold this will work, but it was an easy modification while I was working on the boiler:
From the factory, the door gaskets consist of a large bead of hi-temp silicone, which on my boiler, melted away every year. I decided to clean off the sealing area and glue a 1”x1/4” strip of nomex to both doors. If I can’t seal the firebox, all the sophisticated controls in the world won’t properly regulate the temperature.
I know I’ve missed a few items, and need more and better pictures of others, but this should be a good start. I’ll keep track of wood usage this winter to document any improvements. In the past winters, I’ve used about 12-14 full cord of hardwood to heat a three level (including finished basement) 3000ft house to 72*, an 800ft garage to 55*, and an 800ft apartment above the garage to 72*. Everything but the apartment has radiant floor heat, and both are well insulated. On the coldest spells, 3 days or more of constant below 20 weather, I had to load the boiler up to four times per day, and it would still never reach a 175* set point, the blower ran constantly.
In case you didn't notice in the pictures, there are actually two different 290's we did the same modifications on, so there is a mix of pictures.
The boiler originally shipped with a rather rudimentary temperature control system consisting of a surface mount thermostat that cycled an electric blower on and off, and a manually adjusted draft door on the blower. I had a very difficult time regulating the temperature. I had frequent boil-overs and wide swings in water temp. I addressed the problem by adding a dry well, a solenoid, and a two stage digital aquastat that is set as follows:
180* - blower off and damper closed
<180* but >=175* - blower off and damper open
<175* - blower on and damper open
The idea is to only use the blower when needed, as it forces hot air out the chimney and wastes heat.
The second issue I faced, was what I personally define as “poor insulation”. The boiler used some type of fiberglass batting on the to and sides, and nothing on the bottom of the water jacket. I decided to strip the tin, and ultimately the framing from the boiler and prep for spray foam. I was a bit disappointed to find the outer shell of the water jacket also had no paint and was beginning to rust:
I also discovered the water jacket was not welded solid around the top of the boiler, which essentially left me with a 50 gal air space above the water level:
I sandblasted the boiler, welded the gaps, and sealed the welds with polyurethane roofing sealer for good measure, then painted the boiler and tacked on studs to attach tin:
I also cut and threaded the overflow pipe on the side to direct it up through the roof and reclaim that unused 50 gallons of airspace for water storage.
Before I welded that ridiculous inspection cover in place, I added a couple 90* and a few pieces of pipe to the inside of the return pipe to direct the water to the front of the boiler and promote better circulation. Unfortunately I forgot to take pictures of this step.
Once this long and laborious process was complete, I was ready to have the boiler insulated with closed cell spray foam. I kept the foam away from the door and chimney area, I used rock wool high-temp insulation for those areas, along with in-between the inner and outer firebox door panel:
The single wall chimney was also a source of problems for me. At least twice during the winter it would clog up and I would have to climb onto the shed roof and attempt to clean it out. I decided to cut the existing chimney off about 12” above the tank, and bought some nice triple wall insulated pipe and a cap. I reused most of the existing tin, but had to buy a few corner pieces and covered the furnace
I added a switch to cut the power to the damper and blower while loading the stove:
Since I spray foamed the bottom of the boiler and the hot coals sit in the ash pan and could potentially melt the foam, I thought it best to line the ash pan with half-height firebricks. These bricks also raise the floor of the firebox even with the bottom of the cleanout door, which is a nice benefit.
I think I may also experiment with lining the floor and possibly the firebox walls with firebrick in an attempt to raise combustion temps and further improve efficiency. I’m going to experiment with a secondary burn air tube plumbed from the ash pan area, up along chimney, and along the ceiling of the firebox. I’ve drilled a series of holes in the pipe that runs along the firebox ceiling in hope that the air will help ignite the wood gasses and initiate a secondary burn. I’m not fully sold this will work, but it was an easy modification while I was working on the boiler:
From the factory, the door gaskets consist of a large bead of hi-temp silicone, which on my boiler, melted away every year. I decided to clean off the sealing area and glue a 1”x1/4” strip of nomex to both doors. If I can’t seal the firebox, all the sophisticated controls in the world won’t properly regulate the temperature.
I know I’ve missed a few items, and need more and better pictures of others, but this should be a good start. I’ll keep track of wood usage this winter to document any improvements. In the past winters, I’ve used about 12-14 full cord of hardwood to heat a three level (including finished basement) 3000ft house to 72*, an 800ft garage to 55*, and an 800ft apartment above the garage to 72*. Everything but the apartment has radiant floor heat, and both are well insulated. On the coldest spells, 3 days or more of constant below 20 weather, I had to load the boiler up to four times per day, and it would still never reach a 175* set point, the blower ran constantly.
In case you didn't notice in the pictures, there are actually two different 290's we did the same modifications on, so there is a mix of pictures.
2
Shaver Furnace / My Shaver experience and modifications I've made
« on: November 19, 2008, 09:44:31 AM »
I have a shaver 290 and for the most part it is great, but like some of you I have had a couple issues. My biggest concern is the water steaming off, I am down several gallons a day and steam constantly at all temps. My friend, who has the same furnace uses no water in a 2-3 week time frame and has basically the same installation with the same parts. I think I have discovered the difference in our boilers and why some Shavers steam more than others. I've attached an image depicting our installations. My boiler (Boiler B) has a slight lean to the rear, where my friends (Boiler A) has a slight lean to the front, and possibly an upward angle of the vent tube exiting the boiler.
I believe the lean frontward lean and upward angle of the vent pipe on my friends boiler dramatically cuts down on the surface area of water exposed to the atmosphere. Boiler A's vent pipe is full of water, where Boiler B's is simply a passage way for the atmosphere to make contact with the entire surface of the water in the tank allowing much more steam to be created and exit even when the water is below boiling.
I slid a 1" piece of pex over my overflow and and secured it with a hose clamp. Then added a short 90* and another 1-2" of pex vertically. The boiler water level is now raised slightly, but would still be vented and the surface area of the water exposed to the atmosphere would only be the area inside the vent pipe instead of the entire top of the tank. Another side benefit is I can see my water level in the pex, as I have a pink rust inhibitor additive that shows through the pex. If you run straight water clear flexible pipe attached to the vent, bent upwards and held in place with clamps on the side of the boiler should be an easy fix, just don't extend the pipe up too far or you may risk overflowing out the water coil cover.
Here is a quick sketch of the two scenarios (boiler A and boiler B) as well as a diagram of my proposed fix (bottom right). I've been running this for a day now and have seen zero steam and have lost zero water. I don't think the water in the pex will ever freeze as mine is quite hot (160*+). Does anyone see any problems with this? I sent an email to shaver for their input and am awaiting a response.
Here is my steam fix, I keep the water at about halfway up the pipe so I can track any level changes. My vent use to steam nonstop, but no more.
I replaced the original thermostat because I had bad luck with it and boiled the water a couple times. I also wanted a thermometer to tell me the water temp inside the boiler (I have one on the line coming off the OWB but it is only accurate when the pump running). It's funny you mention inside application, because the controller I have sends a signal 0-10v for a remote monitor, still deciding if I want a display inside to tell me the temp of the boiler. My Ranco is working fine, I'm going to move the well to a better spot . Another guy gave me a great idea for a thermostat well. He used a 12" piece of 1/4" copper, capped one end then flared the other. He then drilled a hole on the top of his water jacket near the cover in the back. He dropped the copper pipe down the hole and the flared end kept it from falling in all the way. dropped in his sensor and siliconed the top. Said it's dead nuts accurate. I plan on doing this to mine this weekend. Here is a pic of it, it is mounted inside the rear door:
I still need to do some cleaning up and insulating on the rear of the boiler, but I have a few more adjustments to make first.
My next project is to modify my blower damper to operate like the natures comfort and Hardy OWB. They use a solenoid to cover and uncover the blower inlet when the fan is on/off. Here is a pic I borrowed from fellow member (derwood91, thanks for the pic):
I modified my spare blower yesterday. I re drilled the flange so it can be mounted with the door facing up. Then I drilled out the door rivet and cut out the grill off the air inlet. I the door to a hinge so it will swing up and put an eyelet in the center of the door. I'm going to mount it on the boiler this weekend and attach the door to a solenoid that will activate and lift the door when the blower turns on. When the blower turns off, the door will close and limit draft. I think this will help the boiler recover quicker when the blower is on, more air entering because the door will be wide open. When the blower is off, the fire will smolder better and not overheat the water. I'll take pics this weekend and let you know how it works.
I believe the lean frontward lean and upward angle of the vent pipe on my friends boiler dramatically cuts down on the surface area of water exposed to the atmosphere. Boiler A's vent pipe is full of water, where Boiler B's is simply a passage way for the atmosphere to make contact with the entire surface of the water in the tank allowing much more steam to be created and exit even when the water is below boiling.
I slid a 1" piece of pex over my overflow and and secured it with a hose clamp. Then added a short 90* and another 1-2" of pex vertically. The boiler water level is now raised slightly, but would still be vented and the surface area of the water exposed to the atmosphere would only be the area inside the vent pipe instead of the entire top of the tank. Another side benefit is I can see my water level in the pex, as I have a pink rust inhibitor additive that shows through the pex. If you run straight water clear flexible pipe attached to the vent, bent upwards and held in place with clamps on the side of the boiler should be an easy fix, just don't extend the pipe up too far or you may risk overflowing out the water coil cover.
Here is a quick sketch of the two scenarios (boiler A and boiler B) as well as a diagram of my proposed fix (bottom right). I've been running this for a day now and have seen zero steam and have lost zero water. I don't think the water in the pex will ever freeze as mine is quite hot (160*+). Does anyone see any problems with this? I sent an email to shaver for their input and am awaiting a response.
Here is my steam fix, I keep the water at about halfway up the pipe so I can track any level changes. My vent use to steam nonstop, but no more.
I replaced the original thermostat because I had bad luck with it and boiled the water a couple times. I also wanted a thermometer to tell me the water temp inside the boiler (I have one on the line coming off the OWB but it is only accurate when the pump running). It's funny you mention inside application, because the controller I have sends a signal 0-10v for a remote monitor, still deciding if I want a display inside to tell me the temp of the boiler. My Ranco is working fine, I'm going to move the well to a better spot . Another guy gave me a great idea for a thermostat well. He used a 12" piece of 1/4" copper, capped one end then flared the other. He then drilled a hole on the top of his water jacket near the cover in the back. He dropped the copper pipe down the hole and the flared end kept it from falling in all the way. dropped in his sensor and siliconed the top. Said it's dead nuts accurate. I plan on doing this to mine this weekend. Here is a pic of it, it is mounted inside the rear door:
I still need to do some cleaning up and insulating on the rear of the boiler, but I have a few more adjustments to make first.
My next project is to modify my blower damper to operate like the natures comfort and Hardy OWB. They use a solenoid to cover and uncover the blower inlet when the fan is on/off. Here is a pic I borrowed from fellow member (derwood91, thanks for the pic):
I modified my spare blower yesterday. I re drilled the flange so it can be mounted with the door facing up. Then I drilled out the door rivet and cut out the grill off the air inlet. I the door to a hinge so it will swing up and put an eyelet in the center of the door. I'm going to mount it on the boiler this weekend and attach the door to a solenoid that will activate and lift the door when the blower turns on. When the blower turns off, the door will close and limit draft. I think this will help the boiler recover quicker when the blower is on, more air entering because the door will be wide open. When the blower is off, the fire will smolder better and not overheat the water. I'll take pics this weekend and let you know how it works.
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