Building an outdoor boiler

[CHRanch2015]

Hello again everyone, I posted awhile back about my plans to build my own outdoor boiler to heat my house starting next season.
I have narrowed down a design and have gotten my firebox already.

I am wanting to get brushed up on some of the details I'll be needing for my build. I have a good handle on the main idea but what I lack is information pertaining to the details such as pumps, aquastat, draft blower etc.
Recommended brands, pump and blower sizing?
What should I use for the water outlets on the boiler? Galvanized, black pipe, brass?
If I could get started gathering some of this information it would help me greatly, thank you and I look forward to your replies.

 

[warno]

Could you tell me about your design? Is it "tank in tank" or are you copying a manufactured boiler design?

How are you heating your building? (In floor, HX in duct work, baseboard, ect.)

How far is your building(s) from boiler?

How many gallons in the water jacket are you running?

How big is your fire box?


This was my first year but As for parts go here's what I have and worked great this year.

Aquastat - Johnson controls A419
Pump - bell and gossett or grundfos
Plumbing - I ran all pex fittings and tubing
Boiler connections - black pipe coming from water jacket
Blower fan - ebay
Boiler return protection - caleffi thermomix valve


Give me a call or text tonight if you have time. I could give you a quick run down of my system.

 

[CHRanch2015]

Well when I first started out I was looking to do a tank in tank design but I figured by the time I'd find a tank big enough to accommodate my firebox I already have I wouldn't be very far ahead.
So I came across manufacturer that I really liked. Earth Outdoor Furnaces. They utilize a 1/2" thick firebox surrounded by an 1/8" water jacket "box"
3/16" chimney that extends about 1/2 way down into the firebox which forces the combustion gases back into the fire for a second burn before leaving the firebox.

I am using about a 4' section that was cut out of a 500 gal propane tank. Will make a good size firebox and has a good heavy wall.
I will be building this at work like you did as I don't have a welder or anything here at home.

 

[CHRanch2015]

Could you tell me about your design? Is it "tank in tank" or are you copying a manufactured boiler design?

How are you heating your building? (In floor, HX in duct work, baseboard, ect.)

How far is your building(s) from boiler?

How many gallons in the water jacket are you running?

How big is your fire box?


This was my first year but As for parts go here's what I have and worked great this year.

Aquastat - Johnson controls A419
Pump - bell and gossett or grundfos
Plumbing - I ran all pex fittings and tubing
Boiler connections - black pipe coming from water jacket
Blower fan - ebay
Boiler return protection - caleffi thermomix valve


Give me a call or text tonight if you have time. I could give you a quick run down of my system.

I will be heating with a HX in existing ductwork for lp furnace.

The boiler will sit pretty close to the house, maybe 20'

I haven't figured out the dimensions of my water jacket to be able to calculate how many gallons, I was thinking somewhere in the 4' x 4' range but don't know to do the math to account for the volume taken up by the firebox. Ideally I'd like to have a water jacket that holds at least 200-250 gallons, I have a big 2 story non well insulated old farm house so I would rather build a large one than too small.
The firebox is about 4 ft long with an outside diameter is just over 3ft.
Going to build an ash pan into the bottom of it and all that

 

[warno]

Well the math is easy to figure your gallons. If you figure the volume of your firebox then subtract that away from your water jacket what is have left is your jacket total.

Like this:

Pi X r^2 X L = cubic inches of volume

then ÷ that by 1728 to get cubic feet

Then X that by 7.4 to get gallons

In one cubic foot there's ~ 7.4 gallons, hints the final equation.

So your fire box is:

3.14 X 18^2 X 48 = 48,858
48,858 ÷ 1728 = 28.27
28.27 X 7.4 = 209 gallons in your firebox

Now to get water jacket volume I need to know if you are using another tank or building a box around your firebox tank.

 

[CHRanch2015]

How do I know what size circulation pump I need for my application?
I've been searching around bit don't really know what size I should be looking at? I see alot of them rated in GPM but don't know hoe any GPM I need for my application

 

[warno]

You need to find your HX for your furnace duct first. It will have information about flow and head loss numbers. Then you need to figure up your plumbing head total and that will tell you which pump to get.

I can't remember all the numbers but each fitting and piece of pipe you add to the system changes your flow and head numbers. you need to figure up all your fittings and lengths of whatever size pipes you are running then get the the total head and figure the required flow for your HX.

 

[CHRanch2015]

Oh ok, sounds good.
What size pex should I run? I was thinking 1" bit should I got bigger to 1 1/4"?

 

[maple1]

They utilize a 1/2" thick firebox surrounded by an 1/8" water jacket "box"
3/16" chimney that extends about 1/2 way down into the firebox which forces the combustion gases back into the fire for a second burn before leaving the firebox.

I'm not sure that will accomplish much more than increasing the smoke spillage out the door whenever you open it.

 

[warno]

Putting your chimney down half way into the box will give you alot of smoke out the door. I'll be honest the thought is there to help burn the smoke off but without added oxygen the smoke simply will not burn any. You will need to find a way to get oxygen right in the area below the chimney pipe to help any possible burning of the smoke.

I would think with your short run to the house and HX that 1" lines will be fine.

 

[CHRanch2015]

Ya I've actually been working on a different chimney design for it that incorporates a chimney bypass like on some other factory models, push the rod in and the smoke exits through a tube at the front of the firebox moves back through the tube to the rear and then exits the verticle stack, this allows for more heat absorption from the exhaust as well before exiting the boiler. But when you pull the rod it will close off the front of the tube and open the rear directly below the stack allowing the exhaust to exit straight out so you don't get as much of a face full of smoke when you open the door, just simply pull the handle to divert the flu gas before opening the door

 

[Pat32rf]

I have an older P&M that looks a LOT like Warno's. No bypass, i just open the door to the first notch for a half a minute or so. The draft created sucks the fresh air IN the door and the smoke goes up the chimney.

 

[warno]

How's this build coming along? Any progress pictures yet?