Outdoor Wood Furnace Info
All-Purpose OWF Discussions => Plumbing => Topic started by: doo_hicky on November 11, 2013, 05:53:54 AM
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Ok, little history first.
I built a room onto my pole barn that I put a pressurized Royall 6150 wood/coal boiler into( it has a 35 gal capacity and is rated at 150k BTU). I ran 1" PexalPex with a gundfos 26-99 3 speed pump pushing the water 120' basically level to where it enters the basement. The electric HW heater is located first then the oil boiler second.
I have a 50 plate to hook into my existing oil boiler and a 20 plate for my domestic HW. The HX are 1" MPT.
Ive read and read and read. I like WillieG's idea of a header system for the 2 exchangers, but since I only have 2
"appliances" (and no need to have any more) would it be worth that?
If i go series why would I want the DHW to be first, other than that it is located before the oil boiler?
Thanks for the help.
Getting cold in west central Pa
Mike
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CAUTION!!!! Think about what you are doing! if you have a power failure there is no way to dump the heat as heat in water will not flow down on its own, it needs to be driven by a circulator, this requires power. Any time that you lose power the boiler will overheat and pop the relief valves from overpressurizing, if the relief valves fail to open you have a bomb in your pole barn! You could put in radiation above the boiler in the pole barn with auto-mag zone valves that can dissipate the heat but that creates another problem with potential freeze up, battery backup with an inverter can solve the issue or a standby automatic generator but they both will require maintenance and can fail. I'm not really good on coal but the golden rule for pressurized wood boilers is that you need to be able to dump a minimum of 30% of the rated heat load of the boiler with no power on conventional wood boilers, ceramic lined or coal I would assume would be far higher. Remember one thing, a failure is never going to happen when you are standing next to the generator, you will either in bed or at work!
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As of right now I only plan to run the furnace on wood(large supply of locust).
This furnace uses a draft blower to add air to be able to burn, no power no draft no burn....no problem? I do have a back up genset that is wired in.
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There is still a bed of coals and a fire in the boiler that will continue to create heat, in other words the fire does not go completely out as with an oil or gas fired unit/ you will still need to dump heat, is your genset automatic and well maintained, just trying to keep you from making a bad mistake.
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Well sorry to say too late, lol.
Hey, if for not anything else i'll be the example of what not to do, unfortunately this is what I have to work with and would appreciate any help with my original question in dealing with the heat exchangers.
Mike
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I chose to goto the water heater first so it was always the most consistent temperature. I have my 20 plate setup so it dumps hot water into the water heater thus making the hwh a storage tank. If it went to the other exchanger first and it callex for heat I could possible lose some hot water and have to readjust while showering and when the furnace cut off could get burnt from the temp. Rise. I don't have a tempering valve and this system has worked percectly for my family.
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doo-hickey, I'm not saying that I won't help, just use caution and set it up right, although I as well like to use a manifold I see no need for it in your case, the idea of going to your hot water first is to make it the priority, be sure to use an expansion tank that is rated for your system (gallons of water).
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Yes, expansion tank is in place and pop off works, we verivied that when we pressurized the furnace before i bought it.
In the future I plan on pouring a pad in half of my pole barn and adding heat to the floor, so that will be my dump zone. For right now I may look into some sort of option to put on that trunk line to get rid of excess heat if need be.
Mike
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Heat in the floor is not a non powered dump zone, it requires power to send the water down
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I know there is a CHANCE that something could go wrong, been around coal/wood boilers for my whole life of 42 years on the farm and I can remember when the power would go out we would have to close the furnace up tight so it wouldnt draw a draft and then the pop off would go off and make a mess of things.
So the whole idea of a pressurized system is not new to me.
I have tried to plan for most of the situations that might happen because me and Murphy are best friends lol
Mike
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just had a thought, i may be over thinking this but here goes: When plumbing my HX i need to have the flow of water enter 1 bottom port exit 1 top port before traveling onto the next HX, correct, I just cant T into the first HX for the feed and return correct?
Mike
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Exactly, if you pulled both supplies off one main loop then you would always be sending water to the heat exchanger with the least resistance.
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I must be a little thick. I did a little sketch but i'm not allowed to attach it. dang IT
Could you possible do a little sketch or picture?
Thanks
Mike
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i am no pump guy for sure so this rant is just that and maybe a pump guy cn explain it to me in a way i understand so here goes my wack way of thinking
your pump with the pipe in its system can (just saying) pump 10 gpm at 20 feet of head
your system comes from the owb to a header with one line from it to your plate exchanger at the hot water tank (this line is getting 10 gpm at 20 feet of head)
you add a second line from teh header to the furnace exchanger that you figure if was on its own would only be 15 feet of head (but its not on its own)
so now (i am also thinking your pump is big enough) your pump still can pump 10 gpm at 20 feet of head so it does just that it pumps up till it is pushing pressure to = 20 feet of head on both lines...the shorter line will get more water but the long line will still get some too? the pressure will still be equal to 20 feet of head but velocity will change the longer line will recieve less and the shorter line will recieve more but both devices will recieve water
unless the shorter line was of such a large diameter that the pump could not build pressure against the the longer line will always recieve "some" water
a valve on the shorter line could be used to adjust equal head pressure on both lines that would ensure equal velocity on both lines(?) this would ensure the same gpm to each device (if that was desired)
i hope some one can explain this properly and cipher out what i think i am typing ..LOL
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If I were doing it I would put them in series. If you go in parallel you will get a lot less GPM through each even though the total GPM will be a little higher. Put the DHW first since it is intermittent will work better with hotter water.
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ok, soooooo plumbing these HX's in series would go like this: Supply line into DHW HX port 1 out of port 2 then into oil boiler HX port 1 out port 2 then straight shot back to my wood boiler, is this correct?
Mike
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Yes and don't forget on the other side of the heat exchanger, the flow should be counter current, in other words the flow through each heat exchanger should go in the opposite direction on the pressurized side.
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Yes, I understand about the counter flow. learned about it from on here, and people having issues.
Hope I can plumb them both tonight after work and hopefully running by the weekend.
I'll keep everyone posted
thanks again
Mike
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I have been thinking about what Jim was saying about having an issue if/when the power goes out and having heat/pressure build up in my boiler.
Could a soultion be a zone valve that(which one normally open or normally closed???) would open when the power goes out. Is there such a beast?
I feel this has merit because my trunk line comes out of the top of the boiler before it goes into my PexalPex. I have a T there already for future expansions, and hotwater will circulate without power. Ill just put in a section of finned radiator in a loop before it returns to the bottom of the boiler.
Thoughts?? or am i off my rocker?
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You are exactly right, is the building being used heated already, can you tag onto an existing loop above the boiler?
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Well, I did it.
Fire in the furnace and no leaks!!!!! Hot domestic water. Now to tie into exixting boiler.
When the HX is "working" what would be the maximum temperature drop that one should see? Just getting an idea if I need to bump up the speed of my pump.
Thanks, this forum has been a GREAT help!
Mike
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I don't like to see more than 20 degrees under full load.
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OK, I thought that was what the average was.
Thank you for the confirmation.
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Well it's been a little over 2 weeks and everything is working better than expected. I can go 12 hours before I need to reload, this was verified when we had a couople days of single digits. My idea of using a lower hot water tank thermostat to complete the circuit for the oil boiler burner works like the expensive strap on aquastats. I just have it sitting on top of the HX for the bioler and if the fire would ever go out and the temp of the HX drops below 125 the circuit is completed and the oil burner will kick on. I completely shut off the electric hot water tank, it had a little blinking light that was annoying me(to warn of high temps). I was pushing 180 deg water to the house, but backed it off to 170-175.
My only complaint is the smoke, depending on how the wind blows...... I may add a nother section or 2 to see if that makes a difference. My long term goal seeing that this furnace is working so well, I have made up my mind to do a block chimney next year.
Mike
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Glad it all worked out well for you, have a very Merry Christmas!