Outdoor Wood Furnace Info
Outdoor Furnaces - Manufacturers WITH EPA-Certified Models => HeatMaster => Topic started by: reggart on April 09, 2017, 09:12:40 PM
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Hi I'm a soon to be owner of a G200. I'm heating a 2300 sf home and a shop floor. I have enough engineering skill to be dangerous and I can't really afford to pay a licensed engineer to design the system for me. I've done all my load calculations utilizing various methods online as a check, which is how I determined the G200 should be adequate. I have several questions on system design that I was hoping a few of you experts out there might help me out with. The first is regarding storage. I see many of the other owners who own EKO or TARM style units are installing either pressurized or non-pressurized storage tanks but I'm not seeing many, if any, heatmaster owners talking about storage. Why? I was considering installing a 500 gal storage tank but the design question I have is: with the heatmaster being atmospheric does that mean I need to either install a heat exchanger to use a pressurized storage tank or use a non-pressurized tank? In either case, it seems to me that this would provide a way to decouple system storage from boiler so that I could put glycol in the boiler for protection for weekend getaways.
Regardless of storage, are most of you using a primary/secondary configuration? It seem to me that heatmaster already kind of assumes that because the boiler comes with a circulator with literature that says it is for boiler flow only.
If the boiler is atmospheric then does that mean you don't need to consider system expansion at warm up (expansion tank?)
I would like to post some basic equipment and load data with some of my design assumptions and have you guys shoot holes in it. Would you be willing to do that?
Much appreciated,
Robert
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Some of the units you mentioned if I’m thinking correctly have very little storage themselves so storage is added then batch burns are performed. One thats known for that is a Garn, they start at a 1000 gallons I believe and a fire is lit once a day then allowed to go out once the water reaches temp. Most OWB’s have enough water storage in them that adding storage usually isn’t required although I do have an additional 450 gallons of storage I’ll explain shortly.
My 450 gallons of storage also doubles as a waste oil boiler I built a few years ago, in the shoulder seasons I let the wood boiler go out and just fire up the waste oil boiler to heat my water once a day, usually at night so if we have any call for heat plenty of BTU’s are available. With my old boiler it couldn’t keep up so I’d run the waste oil boiler during the day as well to heat the shop. While you’ll have much longer burn times bringing all the water up to temp you’ll also have MUCH longer idle times, this became very apparent my first year with a G400. So figure while having to heat up 700 gallons of water I also had to wait for 700 gallons to cool off enough to call for the G400 to run, this lead to excessive idle times and a lot of creosote unless very dry wood was used. My solution was to install a solar differential controller, this monitors storage temperature and the temperature coming from the G400, I had a fifty plate flat plate heat exchanger between the two so the water would never mix, the solar differential controller would start the pump on the storage that ran to the FPHX only when the G400 was hotter than the storage temp, another nice feature is you can set at what temp it starts to run as well, I set it so it doesn’t start the pump until the G400 was up to 150℉.
This system works much better since I moved down to a G200, the 400 would come up to temp so quick the water in storage rarely got above 170℉, with the lower high end output of a G200 it runs much longer allowing the water in storage to average around 175℉ instead. I also use the 450 gallons of water as a buffer tank, normally unless I’m abosulutely positive I’ll be working in the shop the next day I usually keep the night temps at 45, going out in the morning and cranking 200,000 BTU’s worth of heaters up to 65 would really pull hard on about any boiler, however having 450 gallons of water at 175℉ works very well. Also would take a LOT more flow from the boiler to keep up with 200,000 BTU’s. I have a single 100,000 BTU air handler then a 50,000 BTU under the bolt bin directed at the lathe, bridgeport and drill presses, another 50,000 BTU is under the refrigerator I store welding supplies in pointing at the welding bench. I have the 50 plate HX installed thru the back of the fridge as well, the heat that radiates off that keeps all my rods nice and toasty and dry, a few holes drilled between the fridge and freezer on top keeps several forty-five lb spools of wire dry and rust free as well.
As are most OWB’s, HeatmasterSS is an open system so no need for expansion tanks, on my storage I just took a 3/4” pipe cap, chucked it in the lathe and cut the threads out, this I just drop on the 3/4” pipe that acts as a breather.
Being that your shop is radiant it will be kept at one temp, so the large heat load every morning won’t occur so no need for storage or a buffer tank.
Instead of glycol as long as you can install your heat exchanger after the furnace, the warm air from your furnace will keep your water above freezing if the fire is out for an extended period. I’ve thought about this a bit and maybe others will chime in, but I’ve thought that if a person was going to be gone for awhile, it would almost be best to let it go out before you leave, then place a metal bucket or cap over the stack to hold all the heat in the stove as possible instead of trying to cram it clear full before leaving.
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The G200 was designed to be used without additional storage. Adding storage will extend the time between cycles and likely cause the fire to go out. Or if there is enough storage to use up all the wood in the firebox, you will lose the coal bed each time. Starting back up without a coal bed will not burn as efficient.
It is an open system and requires no expansion tank. The boiler comes with an internal pump. This is to provide adequate internal flow and removes the minimum flow requirements and minimum return temp that had to be met before that feature was added.
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RSI and mlappin are correct.
We use a lot of primary/secondary setups but- every job is different and there is no perfect one size fits all method. Sometimes with just domestic water and one air handler we pump them in series with an L port valve to bypass the coil in the duct in warm weather.
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Garn would have built in storage,a lot of others have very little and are added separately. I personally think it's not enough benefit to be worth it.. unless you have a sudden load as was mentioned.
If you go with storage you will need to batch burn with somewhat different controls.
(in my opinion)
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My house load is about 50,000btu and my shop looks like it's going to be 30 x 60 but only putting pex in 30 x 45 portion of slab. I calculated my shop to be about 32,000 btu. The boiler will be located on a slab right outside and next to my shop, which is about 80 ft from the house. I was going to route my piping from my boiler to the shop with 3/4" pipe. From there I'll go to a 5 loop header for my slab. I assume a small circulator would be all that I need for that configuration. My house will have 8 zones and I was hoping I have enough boiler capacity to support a side arm on my existing electric water heater so let's just assume 9 zones at my house. I was planning on running about 80ft of 1 1/4 underground thermopex to the house, penetrate the basement wall (about 4 ft underground) I would immediately go to a circulator and then the zone header where I'd control the zones with valves.
Does the above sound reasonable? Knowing the boiler has two inlets and outlets, I'm still confused about how I will run the piping to both house and shop but still have adequate flow through boiler using it's circulator for that? It kind of looks like the circulator for the boiler has its own separately piped inlets and outlets, is that true?
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It sounds like depending on your location a G100 would be better suited to your needs, being radiant in slab your shop will take the least amount once the slab is up to temp.
I heated a 200 year old 2800 sq ft farmhouse using standard 1” pex for my underground line. With the mention of 8 zones what kind of radiant will you be using in the house?
While the G100 only has one outlet, you could run to the house, back to the shop then to the stove, the house to shop connection could be made in the stove. A lot of people have also T’d off a G100 and run two small pumps off the T.
I’ve run my G100 at a few shows with a 90,000 BTU air handler pulling outside 50℉ air and the G100 had no problems keeping up and cycling off, I didn’t even have that much wood in it as I was trying to avoid having it cycle off.
You’ll have no problems with a sidearm even with a G100, sidearms eventually get the water hotter than a flat plate can but since they do take longer they don’t pull near as hard doing it.
Far as sidearms, I tried one that had the center tube twisted, think like an auger flighting, it does work in a small package, however I think my original had more capacity. A 1” copper pipe inside a 2” inch copper pipe, I made it to fit the water heater to gain as much surface as possible.
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The circuit for the boiler has absolutely nothing to do with your house or shop loops, it is there only to guarantee adequate flow within the boiler in order to eliminate hot/cold spots, they will each need a separate circ unless you do as Mlappin suggests and I'm not sure I would suggest a continuous loop through both the house and shop. One thing I'm missing is your location, this can be a big deciding factor in sizing your boiler.
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Something I might add, I have a 2800sq ft farmhouse and heating DHW, last addition was 1908, all new double pain windows, still have the last peg and post to get out of the attics, so maybe only 4-5 inches of blow in for the attics. 1800 sq ft of converted cow barn for a shop, no vapor barrier under the floor even, only insulated with foil-bubble-foil insulation. Keep it at 65 when working, also have a 120 feet of heated sidewalk, the G200 has zero issues keeping up.
On some of these calm days when it’s above freezing or better a G100 would probably handle it, my waste oil boiler is only around 160,000 input, since working on the shop last summer and some more work on the house awhile back, it will keep up on its own once the house and shop are up to temp for the day regardless of outdoor temp.
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I selected the G200 for a handful of reasons one of them being that I also have plans of converting an additional 1200 sf of log garage into a small cottage and I'd eventually route pipe to it too AND if I still had capacity I even considered a small hot tub by the house. When I did my house, cottage and shop calculations (including house DHW) I came up with 122265 btu. I live in Northern Idaho at about 3200 ft elevation. I know the 1" is borderline for serving my house load so I decided 1 1/4 in case i did decide to add a hot tub to that load. I already ordered the G200 so there's no going back now. Part of the problem is the published numbers on the rating. I was confused about the difference between the 8hr output and max BTU numbers and I figured I'd rather be a little over sized than a little undersized. I've recently read some material on another site that explained the difference.
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If you haven’t already ordered the underground pipe another option is Logstor, is metric but actually runs a touch over a true 1” ID. Pretty good stuff, can be difficult to handle, think mounting an old semi tire on a rim during a polar vortex, but is good stuff none the less. Ran Logstor to both the house and shop here, I have zero issues with lack of flow and thats heating DHW, the house and the sidewalk all at the same time, if all three start at the same time it can make the ΔT pump cry a little.
By time you’re finished the G200 will be a pretty good fit it sounds like.
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My choice would be the G200. It'll do more than you think. And run hot and clean.
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Just curious, what outside design temps were you figuring?
My G100 did 10 hour minimum burn time with all I'm heating at about 5℉ this winter and pretty stiff wind.
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If you haven’t already ordered the underground pipe another option is Logstor, is metric but actually runs a touch over a true 1” ID. Pretty good stuff, can be difficult to handle, think mounting an old semi tire on a rim during a polar vortex, but is good stuff none the less. Ran Logstor to both the house and shop here, I have zero issues with lack of flow and thats heating DHW, the house and the sidewalk all at the same time, if all three start at the same time it can make the ΔT pump cry a little.
By time you’re finished the G200 will be a pretty good fit it sounds like.
It's amazing what you can pull off of a single 1" line IF the loads are stacked in order of priority and temp. Basically you leverage occasional spikes in Dt.
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It's amazing what you guys down there can get away with in heating with Luke warm water, I would caution against those practices in the north country!
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If the house needs 50,000 btu's at the coldest day then at a 20℉ Dt it would work out to 5 gpm. Easily done on a 1" line, small circ. If the hot tub and domestic kicks in it might go up to 30-40 Dt for a bit but no big deal.
But I might be missing something... My mind gets swimmy after a long day.
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It's amazing what you guys down there can get away with in heating with Luke warm water, I would caution against those practices in the north country!
:thumbup: :thumbup:
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Here is a PDF from Taco on selecting the right circulator and figuring head pressure.
http://www.taco-hvac.com/uploads/FileLibrary/SelectingCirculators.pdf
Well shoot, I had another page I was gonna link, went to explain the wonders of primary/secondary loops, T spacing to eliminate or allow ghost flow, etc but it appears the page is no longer on the web.
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I'm glad you posted that link because it reminds me of another question I have. I ran through that whole taco circulator selection step by step and I got stumped when you determine the length of the piping. Are you supposed to include all piping from the the boiler to the header in the house and are you supposed to times that by two because it is a supply and return? Are you supposed to add all of your circuits together or just use the longest run?
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It's amazing what you guys down there can get away with in heating with Luke warm water, I would caution against those practices in the north country!
I agree. Water temps at 130 and my house drops under 70 quick
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The point is Eldon, in Virginia you may be able to heat your home with 5 GPM and your 20 degree diff, you may even do that here with a new, tight, small building on a reasonable day in early December, this forum however serves us all and some of us live a long ways north of the Mason Dixon line, most homes that I service up here have a heat load of 100,000 -300,000 BTUs, believe me, you will not get 30 GPM through your 1 inch nominally sized pipe with those short pex 90s that you use down there and you certainly won't be heating a 4000 square foot 200 year old home with a fieldstone foundation in February here in the North East with that same setup.
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The 50,000 # came from what he said he had calculated for the house heat load. Somewhere back on this thread I thought I read that. The other buildings were on separate lines I thought? If not then I'm definitely off.
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Your reply number 13
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You are correct. That would be for situations where there's maybe a forced air duct for the main house, radiant in the basement slab, hot tub, etc. Where the loads are different temps.
I should have explained it was for specific situations. Your concern is very valid.
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Well Thank You for that, there are some folks in this industry that are so pigheaded that they cannot be prodded into admitting that they made a mistake, I think we may both know a few!
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Well Thank You for that, there are some folks in this industry that are so pigheaded that they cannot be prodded into admitting that they made a mistake, I think we may both know a few!
So what gives? Your in my area, met my pigheaded in-laws, father, aunt, and a few of my uncles but you didn’t stop in for a cold one here? Not cool dude.
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You know darn well that if I were in your area, we would be having a few cold ones, I'm thinking that perhaps we aren't talking about the same folks!
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so anyone got an answer to my circulator sizing questions?
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If you are only going 80' with 1-1/4" then you shouldn't need a real big circulator. The zones may determine size though. What is on each zone?
If all the zones are fairly low heat load, it should be fine. If you need multiple gpm in each all at once you would need a pretty large pump.
Without knowing all the details and only going off what I am assuming, I would use an Armstrong 20-20CI pump.
Also, I would mount the pump in the back of the boiler, not in the house. If the house is lower than the boiler, that should work but if higher it won't.
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Again, there are many variables and one of the very important ones to consider is one that you have not answered, where are you at? Eldons place in Southwestern VA. Heats a great deal differently than my place here in the Northeast or Marty's place in Indiana.
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Again, there are many variables and one of the very important ones to consider is one that you have not answered, where are you at? Eldons place in Southwestern VA. Heats a great deal differently than my place here in the Northeast or Marty's place in Indiana.
He said he lives in Northern Idaho at about 3200 ft elevation and has 55k btu heat load,
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I'm not real familiar with the area but I'm thinking that the heat load seems pretty low for that much space.
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I'm not real familiar with the area but I'm thinking that the heat load seems pretty low for that much space.
Depends, I’ve seen a lot of shops in ag magazines they doubled the insulation up in the radiant, and have a foot in the walls with two foot in the ceilings, minimum of double pain windows and claim to be able to heat it on less than $500 propane for an entire year, these are in places like Minnesota, North Dakota, etc.
Personally I find it hard to believe as these were rather spacious shops, 60x80 and so on, but thats what they claimed.
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Isn't this the house we are talking about? I don't think he said how much heat load the shop is.
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Isn't this the house we are talking about? I don't think he said how much heat load the shop is.
Possibly, but how well it’s insulated will effect the end numbers regardless of house or shop.
A person in the next county had a cinder block house, had the absolute best windows money could buy installed, then filled the walls with insulation somehow, then had 2” of expanding foam sprayed on the outside and in the attic, ended up so tight had issues keeping the water heater lit.
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sorry, I've been off line for a while. I used several methods to come up with the 50,000 heat load to the house using online calculators but that didn't include the sidearm for DMHW I calculated at 21000 btu or the future hot tub (no idea yet on BTU). It's a 2300sf log home, well chinked and very few openings in the walls. The shop is 1800sf but only heating about 1700sf because some of it will be a walk in cooler for hanging meat. I came up with 33,000 btu on the shop keeping it at 65 deg.