Outdoor Wood Furnace Info
All-Purpose OWF Discussions => General Outdoor Furnace Discussion => Topic started by: baldwin racing on November 16, 2013, 06:13:16 PM
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I am going to make a side arm heat exchanger for my electric hot water heater out of stainless steel....I can get scraps from my buddy that works for a company that makes maple products, evap. and so on....I was going to take a 2 inch pipe or 3 inch pipe about 24 inch or 36 inch long,drill 2 holes in the side of it....one at the top on the side for boiler hot in and one on the bottom on the side for boiler water to go out with one inch pipe, threaded on ends to except 1inch female pex fitting with barbed end..........then run 1 inch threw center for hot water heater water to run threw with 1 inch threded ends as well.....like the copper ones you can buy just out stainless steel..... I can do all the work in my own fab shop.....I can tig weld it all together and cut threads in 1 inch pipe and so on....what do you think? It will last a long time this way and wont have anything it except time..... :)
kelly
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I hope you go ahead with it and post some pictures. I plan to make one myself but out of copper and brass. I acquired some 2" coper pipe, and will attempt to spin a copper 2" x 3/4" reducer on a wood lathe. So your idea is alot more sane than mine.
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I hope you go ahead with it and post some pictures. I plan to make one myself but out of copper and brass. I acquired some 2" coper pipe, and will attempt to spin a copper 2" x 3/4" reducer on a wood lathe. So your idea is alot more sane than mine.
hey worth a try.......you want to use mine....lol
I must have hit the button twice sorry same pic.....lol
kelly
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hey boys you guys sound pretty handy why not make your own tube and shell or coil in a shell and have absolute unlimited hot water (like a palte exchanger) and have little to almost no added head pressure
iused a 50 foot coil f soft 1/2 inch copper (domestic water supply) and coiled it inside a 12 inch pipe that the OWB water goes through...very little restriction (head pressure) and all the "on demand" hot water you could ever want
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I am going to make a side arm heat exchanger for my electric hot water heater out of stainless steel....I can get scraps from my buddy that works for a company that makes maple products, evap. and so on....I was going to take a 2 inch pipe or 3 inch pipe about 24 inch or 36 inch long,drill 2 holes in the side of it....one at the top on the side for boiler hot in and one on the bottom on the side for boiler water to go out with one inch pipe, threaded on ends to except 1inch female pex fitting with barbed end..........then run 1 inch threw center for hot water heater water to run threw with 1 inch threded ends as well.....like the copper ones you can buy just out stainless steel..... I can do all the work in my own fab shop.....I can tig weld it all together and cut threads in 1 inch pipe and so on....what do you think? It will last a long time this way and wont have anything it except time..... :)
kelly
It should work but stainless will have less heat transfer than copper and the copper sidearms with just a single 3/4" pipe through the center don't have very good heat transfer. If you make it, go with as much heat transfer surface as possible.
You can buy pre-made stainless steel sidearms for around $175 so I would try to keep cost well below that.
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I hope you go ahead with it and post some pictures. I plan to make one myself but out of copper and brass. I acquired some 2" coper pipe, and will attempt to spin a copper 2" x 3/4" reducer on a wood lathe. So your idea is alot more sane than mine.
Wouldn't it be easier to just buy a 2" to 3/4" copper reducer fitting?
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RSI, no doubt easier to buy a couple or just buy the sidearm but have been experimenting with metal spinning anyway.
kelly, thats a sweet little metal lathe.
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I have no idea how hard it is to do that. I sounded like a lot of work to save a couple $7 fittings.
Are you able to close the end on 1/4" ID copper? I have been looking for a source for making cheap thermowells and haven't been able to find anything.
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Not sure how a thermowell is made, probably couldn't do it.
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What is the reason you decided to use a side arm instead of a flat plate? I've always wondered why people still use them.
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Since my hot water needs are low and quick recovery isn't an issue, I'm using a sidearm. My thinking is it will add the least amount of head to my system and the use of the lowest possible wattage circulator. Along with the FPHE itself, there is usually all the extra fittings, valves, y-strainer, etc. But if I still had kids at home and a high demand for hot water, for sure a flat plate.
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What is the reason you decided to use a side arm instead of a flat plate? I've always wondered why people still use them.
I guess the reason that I'm still not a big fan of plate exchangers is the huge amount of heat they can pull out of boiler water. My buddy has a 30 plate that will pull 30 plus degrees out of his water when his shower and washing machine are both in use(he does not have a tempering valve installed, so even with the washer set on warm,it will scald!).
His water to air exchanger will sometimes pull up to an additional 25 degrees out when the house calls for heat.
He runs his boiler temps quite high-190 on and 195 off, but he has still seen return temperatures at his boiler 135 degree range.
We use a sidearm mounted to our old(installed in the '60's) Bradford White 52 gallon water heater. Throughout the winter we may run out of hot water a half dozen times or so, and if we need a quick recovery, I just flip the breaker and 20 minutes later we have hot water.
I plumbed a mixing valve(anti-scald) in, so my water heater thinks it is much bigger than it actually is, so running out is seldom a concern.
I probably over think things sometimes, but having higher return temperatures by using a sidearm should increase the longevity of my boiler. There have been times when I've not put enough wood in and came out to a boiler with a temperature of less than 180*. Both my exchangers will not lower my water temperature more than 30*, so I rarely hit the 140* temps that we are warned against dropping down to.
Just a few thoughts from an old farmboy. ;)
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Marty, why is he running a 30? With such huge deltas it seems he has some really low flow
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I have to agree with Scott, proper sizing would help. And how often is the flat plate being used? Not often, maybe at the most 5% of the total time. Don't base your return temps on that.
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Scott,
He is running the 3 speed Grundfos (15-58?) on the high setting.
Isn't a 25 - 30 drop fairly normal for a Chinese made 30?
Oh, and he's running a 30 because he bought used off the net, shipped to his house for under 80 bucks...I think?
And...he's cheap!
He has about the same change temperature through his furnace exchanger (25* plus or minus a few as I do), so I'm thinking his flow is OK...???
I threw the 135 degree temperature out there just to remind folks that their boiler temps shouldn't be allowed to get that low. To my knowledge, his boiler never has, only the return line temperature. The occasional low return line water temperature, even that low, shouldn't ever have any bearing on condensation forming in the fire box as long as the actual boiler temperature is much higher.
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$80 for a 30 plate? So it is a 3" x 8" with 3/4" ports?
How much pipe is in that system? It sounds like the boiler flow is way too low.
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i dont think the size of the plate exchanger matters..it is the flow of the domestic water and the flow of the OWB that makes things work
most homes have an output of about 2 gpm at the tap
so if that water was 60 degrees on the way in to the exchanger and 180 on the way out you would have an increase of 120 degrees how ever most folks are not using 180 degree water at the tap and some of that 2 gpm will be cold water mixing in to cool the water.
lets say we need 2 gpm at 120 degrees and the incoming water is 60 so we need to raise it 60 2gpm is about 16 pounds times 60 960 btu per minute or 57600 btu per hour
everything i read says 180 degree water can deliver 10,000 btu per hour with a delta t of 20 degrees so if this is all figured out right (it may not be) 6 gpm from the owb should be able to heat 2 gpm of domestic water going through the plate exchanger to 120 degrees and still have a retrun temp of 160
yes? no? maybe so?
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The size of the plate matters if it has excessive head pressure loss.
If it is the bottleneck and drops the boiler flow rate from 6 gpm to 3 gpm it will cause problems on the whole system.
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i agree witht he low flow and the plate exchanger causing flow problems RSI
i was jsut thinking the other way...your plate exchngerer could not be too big unless your domestic flow was large also?
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RSI, no doubt easier to buy a couple or just buy the sidearm but have been experimenting with metal spinning anyway.
kelly, thats a sweet little metal lathe.
thanks....
I figured I could make a side arm easy.....figured the stainless would last and it's free even better....lol
kelly
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But you can run to large of a flat plate depending on flow on both sides. I've taken a 3/4 30 plate and produced 142 degree water out of the tap with the furnace on 180 with a 10 degree differential. Thats with the furnace 100ft from the house and having a 007 pumping the furnace. The reason I checked was because the customer was complaining the water wasn't hot enough for him. Of course I told him I wasn't going to make it hotter. lol
My point is that water flow on the domestic side determines a lot and if you have a bigger flat plate it will only jack it up more.
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RSI, no doubt easier to buy a couple or just buy the sidearm but have been experimenting with metal spinning anyway.
kelly, thats a sweet little metal lathe.
thanks....
I figured I could make a side arm easy.....figured the stainless would last and it's free even better....lol
kelly
It is certainly worth a try. Just add as much heat transfer surface area as possible if you can.
It will work even if you just do a simple pipe in pipe but probably won't keep up unless you add a large storage tank.