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Plate Exchanger for domestic hot water and OWB

Started by Nodak Andy, January 07, 2021, 12:35:41 AM

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Nodak Andy

Hi guys, my wife and I are going to be having a house brought in and set on a basement on 5 acres that we bought a couple years ago.  I have decided to use an OWB as our main source of heat for the home and hot water.  I'm fairly handy with tools and building stuff and fixing stuff, so I'm looking forward to doing the radiant floor heat system.

Just a quick breakdown of what we will have going on in our house.  We will have in floor heat in the concrete floor of the basement, and also on the underside of the subfloor for the main floor.  I plan to use the aluminum heat plates on the stuff for the main floor as well.  The house will have central air, so I plan to either install a water to air exchanger in the duct work for back up in case the radiant floor heat doesn't keep up, or possibly install a propane furnace instead of just an air handler.... that way If I'm gone for work or something and the wife doesn't feel like keeping up with the OWB she can just let the propane furnace and DWH kick in to keep everything warm...

If I choose to go the route of the water to air exchanger in the duct work, I'll want to find a way to incorporate a propane water heater into the floor heat system... at least then there would be SOME (most likely enough) heat should it cool down when I'm not around to fire up the boiler or keep it running.  I'm thinking something along the lines of a couple valves in the system to isolate the radiant floor heat from the OWB during the off season, essentially making the floor heat system a standalone system with a propane tank installed in the loop for the heat supply....

One quesiton that I do have for you guys is this:  For those of you that use a plate exchanger for heating your DHW, what kind of temp drop do you see between the OWB lines coming to and leaving the plate exchanger...   I'm not sure, but I think typically the temp of the water going into the radiant floor heat system needs to be down around 110 max..... would going through that plate exchanger, even if nobody is using hot water, provide enough of a temperature drop to keep from making the floor heat way too hot?

Thanks for your help!

E Yoder

You'll want to use a mixing valve to temper down the water going into the floor. Otherwise it fluctuates way too much.
They can be set precisely at the temp you need.
You'll want the loops in the slab to be on a separate pump and mixing valve from the loops in the wood floor. Typically concrete transfers heat from pipe to floor more easily, hence lower water temps. Concrete also heats and cools more slowly, the weight creates a flywheel effect.
Integrating another heat source is doable, with the correct heat exchanger, piping and controls.
HeatMaster dealer in VA.
G7000

Nodak Andy

Thanks for the tips E Yoder.  Naturally, I forgot to include a very important piece of information.... I'm going to be using a couple of automated Cross manifolds and will have multiple zone T-Stats hooked up to it...  I suppose I could set up a 12 zone unit for the basement radiant floor heat and the garage radiant floor heat as that will all be in concrete, and then set up the other unit for the main floor heat, and possibly a self contained hanging water to air exchanger for the garage, as I guess I'd be running that manifold at a higher temp.  A buddy of mine who does HVAC recommended I do some sort of air handler/exchanger in the garage and not just floor heat to quicken recovery time so I think I will.  The garage will be spray foam insulated, but we are in ND and it gets brutally cold for long stretches so it may not be a bad Idea to have an exchanger in the loop.

I've been looking into tempering valves, and had planned on installing one in the system for the DHW.    In my research on OWBs I found that central boiler has a pretty good basic layout on how to do almost exactly what I've been contemplating, but they didn't include a tempering valve in the mix for the RFH...  I guess it wouldn't hurt anything to install one in the RFH Loop; If i didn't end up needing it I could always just bypass it or remove it if needed.   I suppose the best thing to do would be to do a drawing of how I envision the layout of the system and upload it to see what people think would need to be changed.  

One other question that I have is on loop length.  It looks like with 1/2" pex roughly 300' is for the most part the recommended max length.  I have seen some sites say 350 is ok, and some say not to go over 250, but for the most part, most say 300'...  does that seem pretty accurate?  We are putting the mechanical room in pretty much the exact center of the house, so there should be very minimal home-run lengths.

Any other tips and pointers that you folks with experience in these systems have is GREATLY appreciated.  Thanks!

Corley5

Be aware that a flat plate heat exchanger will plug with lime scale.  Getting one that can be taken apart for cleaning makes life easier 😉
Burnt Gunpowder is the Smell Of Freedom

trapper

Where do you plan to get wood from 5 acres is not going to last long.
stihl ms241cm ms261cm  echo 310 400 suzuki  log arch made by stepson several logrite tools woodmizer LT30

hedgerow

Quote from: trapper on January 07, 2021, 09:46:53 AM
Where do you plan to get wood from 5 acres is not going to last long.
This is a good question. Welcome  Nodak and Andy to the forum. I am not sure were to start. I have been doing what you want to do for 11 years. You will need a fair amount of wood. I burn 10-15 full cords of hedge a year. I run my Garn year around to heat domestic to try to recoup some of the investment. Your going to want to set up a primary, secondary pumping system with heat exchanger's. You will need mixing valves on your floor heat. I have floor heat in my shop 30x60x16 and have a air handler with a coil in it to help when the doors open and close. I have three coils in three furnaces in my house and pex under the wood floors on the first floor. If I were you I wouldn't buy a OWB open system boiler you will always be fighting treating the water to keep from plugging your heat exchangers. I got a $15,000 Garn that been a pain in the you know. I have about $30,000 total in my system when I put it in 11 years ago and I did all the work other than the spray foam. Two years ago I spent three grand on repairing a leak and now I have another leak in a another location. Got high temp silicone on the leak for now hope to make it threw the winter. Before you spend the first dime run the numbers and make sure this wood heat is going to work. Heating with wood is a life style and takes a lot of time, energy and money. Its not free heat. Spend your money on sealing that house up and just heat with propane. I would put the tubes in the concrete when poured even if you never use them.   

Thomasjw4

I installed all my own pex in the crawlspace for my CB and both dealers in my area said not to go over 300 feet on the loops.  i have had no problems whatsoever.  Make sure you get the correct type of pex.  

Nodak Andy

I actually have 3 different tree services that give me all the wood I can handle.... I've currently got cottonwood, boxelder, oak, ash, elm, and lots of pine but the pine will be used for milling. We don't get big stands of trees here in ND like you folks on either side of us do, but there are always plenty of people having trees taken out of their yards, or farmsteads, or tree rows in their farm fields....  this last summer I'd guess we probably got 30+ full cords worth of tree service wood for free other than the cost of going and getting it...  The property we bought actually looks kind of trashy right now because there's stacks of milling logs and piles of firewood rounds everywhere waiting for me to finish my log splitter build...  I hauled 4 16' dump trailer loads of big cottonwood logs from 1 jobsite in 1 day...  the guy who owns that tree service said he has 2 crews running around town that take down that much wood every day...  They have to pay to dispose of it at the dump so I'm doing them a favor by taking it...
I know cottonwood isn't ideal for burning, in fact its pretty sucky, but if it's free it's free...  It can be used through the summer for the DHW or in the shoulder seasons and should work fine for that.  On top of all that, the city landfill requires any tree service that does come into town to dump logs and chips to separate the logs/rounds out so that if anyone in town wants to come get some for burning they can...  they don't charge anything to haul OUT logs or rounds, and told me that nobody has come in and gotten any for at least 3 years.... I hauled 4 16' dump trailer loads out of there over the summer, and left a few more loads sitting there still...

I'm currently leaning towards a Crown Royal gasifier unit because I've read so many good reviews and seen many videos praising their boilers.  I understand it's a big investment and will require some maintenance, but that's ok with me...  Like I stated before, I'm fairly handy  with tools, and have plenty of experience working on equipment.  I've been pretty mechanically inclined all my life thanks to my dad and my oilfield experience.

You make a good point hedgerow about heating with wood being a lifestyle.  I love working with chainsaws and splitters and doing the physical labor involved with wood.  In fact, I'm hoping it will help me get back into better physical shape...  Since becoming a plant operator my physical activity levels at work has gone way down from what it was when I was a field operator and a pipeliner...  I need more exercise, and firewood is a good way to get it.  The place that is building our house said the walls will have an r value of around r-30.  The way it looks right now, our basement will be poured using ICF forms which are about the best insulation you can get for a basement.  We won't be cutting ANY corners when it comes to insulating and sealing up the house.  I don't want to rely on propane for a main heat source because the price can fluctuate so much.  One of my coworkers has propane for a main heat fuel.  He told me that 4 or 5 years ago he needed to refill in the middle of winter and it cost him almost $5/gallon...  I know it's not always like that, but 1 season of prices like that will make a huge difference.  

There are a couple other factors that I should probably put out there as well.  I intend to build a big shop for woodworking and milling within a couple years of completing the house, so it will also be heated with in floor heat fed by the OWB.  The other factor is that with the milling business that my brother and I have, I'm always going out and getting logs from tree services anyways, so taking everything they have (that's worth burning) instead of just the big millable logs, isn't really an issue.... It only makes sense to take it all and use the non mill logs or rounds and use them for heat...  We make money off the cottonwood logs we get as well.  We mill them into windbreak planks and sell them to local ranchers.  They sell fast, even when green...  Theres not a whole lot competition for us with taking wood off TS hands as not many people around here burn wood for an actual heat source, and the closest person to us with a mill is like 60 miles away...  I don't really see that changing any time soon either lol

hedgerow

Nodak Andy   Sounds like you have your bases covered. Your a young guy you will love cutting and splitting wood. Around my farm the elm and cotton wood heats the brush pile. I not going to spend the time cutting it up and splitting it for the little heat it makes in my boiler. I have a farm that has more hedge {Osage Orange} on it that I will ever get cut in my live time. Throw that in your boiler and your making heat. Hope the new house build goes well kept us posted.Can't say what the best OWB is I just know I wouldn't buy another Garn its been a money pit.  

petefrom bearswamp

Both my domestic water (indirect) and baseboard heat go thru a plate exchanger.
Exchanges into my oil boiler then to the 2 systems.
Heat exchange typically gives about 9to 12  degrees drop in water temp.
When the circulator from the outdoor boiler runs for a time there is no heat loss showing on both thermometers (outdoor boiler and inlet to plate exchanger).
The run is approximately 35 feet.
I havent done this in a while but here are the various temps this morning.
OWB jacket temp 168
Plate exchanger in 168
plate exchanger out 156
indoor boiler jacket 151
System is set so that wife can flip a few switches to go to oil when Im gone.
Feeds back to the OWB to keep the water from freezing.
Inefficient, but you know "happy wife etc"
You can see by my profile that I am not a spring chicken but with my son doing the bulk of the heavy lifting I am still doing it.
I have a water to air Modine unit that keeps our garage at 55 degrees.
That cottonwood will keep you warm going back and forth to the wood pile and back.
Good luck with designing your system
Kubota 8540 tractor, FEL bucket and forks, Farmi winch
Kubota 900 RTV
Polaris 570 Sportsman ATV
3 Huskies 1 gas Echo 1 cordless Echo vintage Homelite super xl12
57 acres of woodland

Nodak Andy

Quote from: petefrom bearswamp on January 07, 2021, 01:34:56 PM
Both my domestic water (indirect) and baseboard heat go thru a plate exchanger.
Exchanges into my oil boiler then to the 2 systems.
Heat exchange typically gives about 9to 12  degrees drop in water temp.
When the circulator from the outdoor boiler runs for a time there is no heat loss showing on both thermometers (outdoor boiler and inlet to plate exchanger).
The run is approximately 35 feet.
I havent done this in a while but here are the various temps this morning.
OWB jacket temp 168
Plate exchanger in 168
plate exchanger out 156
indoor boiler jacket 151
Good luck with designing your system
Thanks for the info pete!  This confirms what I had thought.  The water leaving the exchanger for the DWH will still be too hot to run through the radiant heat system without a mixing valve installed.  

petefrom bearswamp

I added some to my last post Andy
Also we keep the domestic pretty hot
Also run the owb 170 to 180
Kubota 8540 tractor, FEL bucket and forks, Farmi winch
Kubota 900 RTV
Polaris 570 Sportsman ATV
3 Huskies 1 gas Echo 1 cordless Echo vintage Homelite super xl12
57 acres of woodland

krusty

I have a g200 boiler and it heats my house and shop. On the plate exchanger in my house there is no noticable temp drop in the output water sonitbwill hit 180F like my boiler or close it so you will need a mixing valve for domestic hot water. I also have myson wall radiators which i love. Even though they are fed with water 160 to 180F they dont burn skin to touch and make it nice and toasty in the winter.

DDW_OR

here is a link to my Central Boiler 750 Edge
https://forestryforum.com/board/index.php/topic,92218.0/all.html#top

I had to crawl into the 750, remove cover plate and scrape the heat exchanger
got two 5 gallon buckets of creosote.
https://forestryforum.com/board/index.php?topic=92218.msg1773073#msg1773073


the new 760 HDX is what i will be upgrading to in a couple years
Classic Edge HDX Outdoor Wood Furnace | Central Boiler
MUCH easier to clean!
several years ago i went to the plant in Minnesota
after the plant tour, they took me to the lot where the new 750's where stored
i asked the guide to remove the heat exchanger covers from inside the fire box.
he looked and thought, "how am i going to do this"
i then brought him to the back side
told him to put the cleanout on the back side, and rotate the exchanger 180 deg.
and i told him his competitors where using stainless steel.

so what did i get, a hat that i had to beg for.

the 750 that i have is way to big for the heat load i now have
plan to add the following
30x64x12 pole barn
18x32x8 shop under a lean-too on the barn
8x12x8 chicken coop under the same lean-too

the record low for Glendale Oregon is -1
most of the winter has been in the +20 to +50

FYI - here is a great Woodmizer mod
https://forestryforum.com/board/index.php?topic=113481.0#top
"let the machines do the work"

barbender

The Gasification outdoor boilers negate most of the reasons I got an OWB in the first place, other than the wood mess being outside. I have a bit of a sideline woodyard, with a sawmill and firewood processor. All of the debris and anything that can't be sold to someone else goes in the ol Heatmor. I rarely put up much of a woodpile for myself, it's kind of a garbage disposal that heats our house😁 (no I don't burn actual garbage)
Too many irons in the fire

Nodak Andy

Quote from: barbender on January 07, 2021, 07:58:09 PM
The Gasification outdoor boilers negate most of the reasons I got an OWB in the first place, other than the wood mess being outside. I have a bit of a sideline woodyard, with a sawmill and firewood processor. All of the debris and anything that can't be sold to someone else goes in the ol Heatmor. I rarely put up much of a woodpile for myself, it's kind of a garbage disposal that heats our house😁 (no I don't burn actual garbage)


What do you mean by they negate most of the reasons you got an OWB?  Are you saying you wouldn't go with one?  If so, Why?  From everything I've read and watched they seem to burn cleaner and use less wood.  Not sure how accurate that is as I have literally zero experience burning wood to heat a house/shop.

DDW_OR  I wish our record low was -1 :D...  we 20-40 day streteches every winter where we don't get above zero....  I've seen the thermometer on the truck read -53 before on the way to work in the morning.... I've also seen it read "ERR" because it was too darn cold for it to register...

I'm trying to get well ahead on my wood pile to allow for enough dry time that I hopefully won't have much issues with creosote.  I know that burning green wood will greaten the amount of creosote build up.  I also think that having a properly sized OWB will help to ensure proper run times and operating temps to hopefully minimize creosote build up.  

Our new house will have approximately 3700 sqft of living space and 1000 sqft of garage that will all be heated with radiant in floor heat with the OWB as the heat source along with the DHW.  On top of that, the shop that we plan to build will be either 40x60 or 40x80 with 12' sidewalls minimum.  Everything will be extremely well insulated, so I'm thinking the 7300e from Crown Royal will be sufficient for our setup... I know it says it's good for 4-5k sq ft. but I think with how well we will have everything insulated and sealed up, it will be sufficient.  We haven't decided whether or not we will be getting a hot tub... if we do decide to add a hot tub, I'll bump up to the 7400e model, which is rated for 8-10k square feet.

thecfarm

I have a 400 Heatmor. I have no idea how many square feet it will heat, had it since 2007. Must be a lot, it takes a 54 inch stick. I planned on a working garage.  ::)  But with cement costing so much and ground work, that is not going to happen. I heat a 30x40 house, basement is heated too. Never had a creosote problem with it. I know some brands do, but this one gets hot inside and burns it out. I have burned both hardwood and softwood right off the stump and still had no problems with creosote. But I do have the old style too.
Model 6020-20hp Manual Thomas bandsaw,TC40A 4wd 40 hp New Holland tractor, 450 Norse Winch, Heatmor 400 OWB,YCC 1978-79

hedgerow

Nodak  Andy  Seasoned wood is a must with these newer wood burners. My Garn will burn wood right off the stump no problem and no creosote problem but you burn a  lot more wood to stay warm as it takes a lot of energy to dry and burn that wet wood. When I installed mine and all the numbers were ran as I had heated my house on propane and my shop also but not the floor  in my shop or house we thought we knew our heat load. Wow did we miss it. Eleven heating seasons into this wood thing with the Garn it takes close to twice as much wood as we figured. We were hoping for 5-7 cord and we are running out 10-15 and that's running year around for domestic. I know we keep the house warmer on wood than if we were buying propane. So far we have had a fairly mild winter. Been down to zero only one morning and in that period I was running two loads a day have been running one load a day so far in Jan and usually this time of the year I am running three loads a day. I am at a cross road with heating with wood my Garn is leaking again and two years ago I spent $3,000 repairing it and now have a leak in a different place. Got it silicone for now hope to make it to spring. Have to see if we can repair it again as I am not ready to spend $15,000 for a new one. I would just buy propane. This free wood heat isn't free. Good luck with your project.  

Corley5

  At this point in my life I wouldn't install another OWB.  I'd go with a geothermal unit.  Affordable Heating and Cooling | Well-Connect Geothermal in particular.  The only thing stopping us doing it now is they aren't currently compatible with hydronic heat and we have baseboards and in-floor heat.  Installing duct work isn't something I want to do at the moment.  I'm in the firewood business too and wood still isn't cheap. 
Burnt Gunpowder is the Smell Of Freedom

Nodak Andy

Quote from: hedgerow on January 08, 2021, 09:53:10 AM
Nodak  Andy  Seasoned wood is a must with these newer wood burners. My Garn will burn wood right off the stump no problem and no creosote problem but you burn a  lot more wood to stay warm as it takes a lot of energy to dry and burn that wet wood. When I installed mine and all the numbers were ran as I had heated my house on propane and my shop also but not the floor  in my shop or house we thought we knew our heat load. Wow did we miss it. Eleven heating seasons into this wood thing with the Garn it takes close to twice as much wood as we figured. We were hoping for 5-7 cord and we are running out 10-15 and that's running year around for domestic. I know we keep the house warmer on wood than if we were buying propane. So far we have had a fairly mild winter. Been down to zero only one morning and in that period I was running two loads a day have been running one load a day so far in Jan and usually this time of the year I am running three loads a day. I am at a cross road with heating with wood my Garn is leaking again and two years ago I spent $3,000 repairing it and now have a leak in a different place. Got it silicone for now hope to make it to spring. Have to see if we can repair it again as I am not ready to spend $15,000 for a new one. I would just buy propane. This free wood heat isn't free. Good luck with your project.  
Good info sir.  When I first started researching this venture I figured we'd be burning a minimum of 10 cord a year for just the househeat and DHW with a gasifier.  I guess next winter will be fun :) .  I'm hoping to have my splitter done in the next month.  When that is done, I will begin splitting and stacking with my 10 year old son.  We get A LOT of wind here, and our property is literally on top of a hill, and our tallest tree row trees are only about 3' tall.  I'm fully confident all my wood will be plenty dry for next winter.  I do have considerably more than I think we will need, just to be on the safe side and will continue to grab more as the tree services call and also as we continue to mill planks, lumber, and slabs.  On top of that, once we get half way through the summer I'll start checking moisture levels and if need be, we have a decent sized kiln that I can load up and dry firewood in if need be.  If I stack the wood neatly I can fit over 5 full cords in it at a time.  I know that runs down the savings from burning firewood, but for the first year, if needed, I'm ok with that.  I will have propane backup, but the only thing I really want to use propane for is cooking...  back in 2014 one of my coworkers had to pay almost $5/gallon to fill his tank...  not really wanting to be subjected to the price fluctuations that are seen with propane usage and always wondering if the prices are gonna skyrocket again or fall...  Especially with our current and upcoming political climate... 
Corley5 - I hear ya on the geothermal and for quite a while I was considering considering it.  The only problem I have is that where I am at, there is 1 guy within about 100 miles that has any kind of experience working on geothermal systems.  If something was to go wrong, and I'm not able to figure it out myself it's gonna suck.  On top of that, the cost of a well is incredibly expensive, and I just don't have faith that an air exchange geothermal or a horizontal field is going to be efficient where we are in the middle of winter.  Also, the in floor heat is an absolute must to my wife...

PoginyHill

Andy,
Claims on new OWB's of "50% more efficient", etc... generally compare to an older OWB that can burn green wood. Depending on how/where it is installed, new ones are probably on par or maybe less efficient than an indoor wood furnace or wood stove. This is my 3rd year on a Classic Edge 750. I burn more wood (although probably keep the house warmer and use it to heat my garage frequently) compared to the indoor wood boiler I had for 15+ years. 12 cords now versus 8 cords then. But I wouldn't go back and enjoy the "lifestyle" of burning wood. Fill it twice per day and clean it once a week or less. I am a happy camper (so far).
Kubota M7060 & B2401, Metavic log trailer, Cat E70B, Cat D5C, 750 Grizzly ATV, Wallenstein FX110, 84" Landpride rotary hog, Classic Edge 750, Stihl 170, 261, 462

hedgerow

Quote from: Nodak Andy on January 08, 2021, 12:57:15 PM

  I will have propane backup, but the only thing I really want to use propane for is cooking...  back in 2014 one of my coworkers had to pay almost $5/gallon to fill his tank...  
I know a few folks that got caught on that one too. You need to get your propane contracted in July not be buying propane in the winter. I hadn't bought any propane in 10 years and when I had my first leak on my Garn two years ago I filled my tank back up just in case and paid 85 cents cash price. We dry our cloths with propane so we do burn some. If I end up taking my Garn out I may put a Geotheral unit in next to my propane furnace and just do a pump and dump system. I have tons of ground water were I am at so pumping my domestic well is no problem. I can by the equipment whole sale so it wouldn't be bad. The geo systems work pretty good around here. I have put a few in. Propane out in the country and small towns is the fuel of choice around here. Some electric heat but not a lot. Not a ton of wood being burned in my area.

barbender

Andy, when I decided to go with an OWB I wanted something that wouldn't give me headaches and would last a long time. I had hear horror stories of people's stoves rusting out in 3 seasons, but a couple if guys I worked with both had Heatmors with over 10 seasons apiece. They are dead simple, just a couple of limit switches, a blower fan, there's just not much to go wrong. I can burn the junkiest wood and it gobbles it up. I'm not overly familiar with the gasifier units, but I've heard stories. Simple and maintenance free was not how they were described, but again that's second hand.
Too many irons in the fire

DDW_OR

barn, go BIG. you will not regret it

Kiln: can the OWB be used to heat it?

OWB: look at a minimum of 2 different manufactures
and go talk to as many of the owners of the units as you can.

look at how the unit is cleaned and maintained, you will be doing that for years


"let the machines do the work"

thecfarm

Quote from: barbender on January 08, 2021, 11:35:25 PM
Andy, when I decided to go with an OWB I wanted something that wouldn't give me headaches and would last a long time. I had hear horror stories of people's stoves rusting out in 3 seasons, but a couple if guys I worked with both had Heatmors with over 10 seasons apiece. They are dead simple, just a couple of limit switches, a blower fan, there's just not much to go wrong. I can burn the junkiest wood and it gobbles it up.
That is why I went with a Heatmor. Dead simple is a a good use of two words. The limit switches are Honeywell too. No proxy switches, no solenoids, no fuses. Just really a round tube full of water.
I stopped at many houses when I saw someone out filling there OWB.  ;)
I doubt I will get another one. I got mine back in 2007. Prices was not all that bad. Them things are crazy high now.  :o
As said Heatmor is dead simple. A person could build one for far less.
I have and do burn a lot of dead wood in mine. I even burn dead cedar in it. Gives me a controlled burn. Yes, I probably do use more dead wood than I would good hardwood, because of no coals, but I have burned dead wood for 10 years and the supply is never ending.
Model 6020-20hp Manual Thomas bandsaw,TC40A 4wd 40 hp New Holland tractor, 450 Norse Winch, Heatmor 400 OWB,YCC 1978-79

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