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General Outdoor Furnace Discussion / Proper fan speed, forced draft question.
« on: December 04, 2013, 08:04:12 AM »
I've been running the outdoor boiler I built for 6 weeks or so. Knock on wood, everything seems to be going good so far.
I've been fine tuning the boiler operation since I started it up. Slow fan with open flue damper, fast fan with partially closed damper, covered slots in grate, open slots etc...
My question:
Is there any "rule of thumb" for those who run forced draft boilers? Should the fan be on high speed, forcing tons of air into firebox to create a super hot, fast burning fire to heat the water very fast?
Should the fan be slowed down to create a more "stable" fire similar to the rate at which a regular woodstove burns? I'm thinking it would end up using more wood due to the cooler fire.
I currently have the fan turned up quite high and have very little visible smoke coming out of the chimney when the boiler is cycling.
I'm just curious what the rest of you have found to be the most efficient combination of fan speed, damper settings and whatever else you all do.
Thanks everyone!!
I've been fine tuning the boiler operation since I started it up. Slow fan with open flue damper, fast fan with partially closed damper, covered slots in grate, open slots etc...
My question:
Is there any "rule of thumb" for those who run forced draft boilers? Should the fan be on high speed, forcing tons of air into firebox to create a super hot, fast burning fire to heat the water very fast?
Should the fan be slowed down to create a more "stable" fire similar to the rate at which a regular woodstove burns? I'm thinking it would end up using more wood due to the cooler fire.
I currently have the fan turned up quite high and have very little visible smoke coming out of the chimney when the boiler is cycling.
I'm just curious what the rest of you have found to be the most efficient combination of fan speed, damper settings and whatever else you all do.
Thanks everyone!!
2
Home Made / New Build Pics and a Few Questions.
« on: September 08, 2013, 05:37:52 AM »
I wish I had found this great forum before starting my build but I didn't.
I've attached pics of the firebox and water jacket. Due to the vast amount of knowledge and experience many of you have, I'm sure I've done a few things wrong. This is my first build and I'm doing it from my own ideas and without a set of plans. Please go easy on me. I'm very interested in any and all feedback and criticism regarding what I've built so far. Obviously, with the work, steel and money already committed to the boiler build, radical "cut it apart and start over" suggestions aren't realistic.
I've never owned, used or seen an OWB before so I'm basically winging it. Like I said, I truly wish I had found this site before I started. But anyway...
The firebox is 1/4" hot rolled plate. It's 28" long, 24" wide and 32" tall. I've installed a 3 1/2" schedule 40 pipe under the rack for the blower to inject air under the grate. The grate is 1" round bar. My plan is to run 6" schedule 40 pipe out of the top of the firebox as the exhaust. From what I've seen on this site, I'm thinking the pipe should extend 12" or so down into the box.
The water jacket is 3/16 hot rolled plate. It is 36" wide, 48" tall and 38" long or deep looking at it from the front. I've calculated the water capacity to be 196 gallons once the firebox is installed.
I have installed a 1/2" steel bung in the bottom plate for a drain hosebib.
My questions are:
1: is it worth the extra steel and time to weld 1/4"x2" flat bar, on edge, on the outside of the fire box? The thinking being it will act as a heat sink allowing the water to come in contact with more surface area. Similar to the "fins" on an air cooled engine. I also think it may "swirl" or mix the water around the box better. I may be way off on this thinking but figured I throw it out there.
2: based on the sizes of the fire box and water jacket, how far off the bottom should the box be? I plan on installing 1" bungs for take off and return lines. I will be pulling from the bottom (of the back water jacket plate) and returning into the top. I've planned to extend 1" copper pipe into the jacket a foot or so for take off and 2 foot or so for return. I'm just not sure what you would recommend for clearance under the fire box.
3: this unit is intended to run the radiant heat in the basement and first floor, baseboards in two bedrooms up stairs and the domestic hot water for showers, faucets, etc... I'm figuring an 80-100 plate water to water heat exchanger would be sufficient.
Is the heat exchanger placed out at the boiler, in the enclosure (shed) or is it better to have it in the basement right near the existing plumbing, oil boiler, etc...? I'm planning to run 1" pex. The boiler will be almost level with the house 45 feet from the outside of the house foundation. It's approximately another 15 feet in the basement to the plumbing connections.
4: I purchased a "Honeywell 6006" aquastat with the immersion probe/well. The aquastat has a probe hard wired off the back which inserts into the immersion probe/well. Where is the best location for the probe/bung? Directly over the takeoff bung?
5: the boiler will be air fed by a blower under the grate. I was thinking of using a throttle body off a Suburu Forester to act as a baffle. The butterfly will be opened and closed with an actuator/solenoid and the blower will be attached to the throttle body "throat/rim".
When the blower shuts off and the butterfly shuts, it effectively seals off any air supply. Does the boiler require a small amount of air or draft while the boiler is "idling"?
I know the whole idea of a blower and butterfly is to kick the fire up when the water temp drops below a certain point and then to lower the fire once temprature is reached. I'm curious if an "auxiliary" vent or similar point of air intake is required to basically prevent the fire from suffocating between cycles. Is it desirable to have all air shut out between cycles?
These are the main questions I have right at the moment. As I said, I have never attempted this type of build before so I hope this will work the way I want it to.
I have many years of fabricating experience but basically no experience burning wood.
Please give me whatever you got.
Thank you very, very much!!!
[attachment deleted by admin for space issues]
I've attached pics of the firebox and water jacket. Due to the vast amount of knowledge and experience many of you have, I'm sure I've done a few things wrong. This is my first build and I'm doing it from my own ideas and without a set of plans. Please go easy on me. I'm very interested in any and all feedback and criticism regarding what I've built so far. Obviously, with the work, steel and money already committed to the boiler build, radical "cut it apart and start over" suggestions aren't realistic.
I've never owned, used or seen an OWB before so I'm basically winging it. Like I said, I truly wish I had found this site before I started. But anyway...
The firebox is 1/4" hot rolled plate. It's 28" long, 24" wide and 32" tall. I've installed a 3 1/2" schedule 40 pipe under the rack for the blower to inject air under the grate. The grate is 1" round bar. My plan is to run 6" schedule 40 pipe out of the top of the firebox as the exhaust. From what I've seen on this site, I'm thinking the pipe should extend 12" or so down into the box.
The water jacket is 3/16 hot rolled plate. It is 36" wide, 48" tall and 38" long or deep looking at it from the front. I've calculated the water capacity to be 196 gallons once the firebox is installed.
I have installed a 1/2" steel bung in the bottom plate for a drain hosebib.
My questions are:
1: is it worth the extra steel and time to weld 1/4"x2" flat bar, on edge, on the outside of the fire box? The thinking being it will act as a heat sink allowing the water to come in contact with more surface area. Similar to the "fins" on an air cooled engine. I also think it may "swirl" or mix the water around the box better. I may be way off on this thinking but figured I throw it out there.
2: based on the sizes of the fire box and water jacket, how far off the bottom should the box be? I plan on installing 1" bungs for take off and return lines. I will be pulling from the bottom (of the back water jacket plate) and returning into the top. I've planned to extend 1" copper pipe into the jacket a foot or so for take off and 2 foot or so for return. I'm just not sure what you would recommend for clearance under the fire box.
3: this unit is intended to run the radiant heat in the basement and first floor, baseboards in two bedrooms up stairs and the domestic hot water for showers, faucets, etc... I'm figuring an 80-100 plate water to water heat exchanger would be sufficient.
Is the heat exchanger placed out at the boiler, in the enclosure (shed) or is it better to have it in the basement right near the existing plumbing, oil boiler, etc...? I'm planning to run 1" pex. The boiler will be almost level with the house 45 feet from the outside of the house foundation. It's approximately another 15 feet in the basement to the plumbing connections.
4: I purchased a "Honeywell 6006" aquastat with the immersion probe/well. The aquastat has a probe hard wired off the back which inserts into the immersion probe/well. Where is the best location for the probe/bung? Directly over the takeoff bung?
5: the boiler will be air fed by a blower under the grate. I was thinking of using a throttle body off a Suburu Forester to act as a baffle. The butterfly will be opened and closed with an actuator/solenoid and the blower will be attached to the throttle body "throat/rim".
When the blower shuts off and the butterfly shuts, it effectively seals off any air supply. Does the boiler require a small amount of air or draft while the boiler is "idling"?
I know the whole idea of a blower and butterfly is to kick the fire up when the water temp drops below a certain point and then to lower the fire once temprature is reached. I'm curious if an "auxiliary" vent or similar point of air intake is required to basically prevent the fire from suffocating between cycles. Is it desirable to have all air shut out between cycles?
These are the main questions I have right at the moment. As I said, I have never attempted this type of build before so I hope this will work the way I want it to.
I have many years of fabricating experience but basically no experience burning wood.
Please give me whatever you got.
Thank you very, very much!!!
[attachment deleted by admin for space issues]
3
Home Made / POR-15 the inside of water jacket.
« on: September 05, 2013, 05:01:46 AM »
I've used POR-15 paint on other projects like the underside of vehicles and various outdoor steel projects.
Based on the incredible toughness and durability of POR-15, I'm curious if anyone has thought about or actually has coated the inside of their OWB water jacket with POR-15 or something similar?
I don't think heat would be an issue since the water shouldn't get any hotter than 212f due to a non pressurized system simply boils over should it reach this temp.
I'm thinking a good coating over the steel which is in contact with water would greatly reduce rust and eventual rot.
Does anyone have any expierience or general input on this idea?
Positive or negative I would love your input.
Thanks!!
Based on the incredible toughness and durability of POR-15, I'm curious if anyone has thought about or actually has coated the inside of their OWB water jacket with POR-15 or something similar?
I don't think heat would be an issue since the water shouldn't get any hotter than 212f due to a non pressurized system simply boils over should it reach this temp.
I'm thinking a good coating over the steel which is in contact with water would greatly reduce rust and eventual rot.
Does anyone have any expierience or general input on this idea?
Positive or negative I would love your input.
Thanks!!
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