Outdoor Wood Furnace Info
All-Purpose OWF Discussions => Plumbing => Topic started by: GUSWHIT on May 04, 2017, 11:07:28 AM
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I am too dumb to understand these head charts apparently and I have asked 2 of my plumber friends to help get my main flow pumps set up and they both come up with answers different than I can decipher from the literature I have been reading. HELP, please from someone knowledgeable!
Here is what I have: OWB, 20' from house then a run to the basement for 52', so the 1 1/4" Logstar comes in approximately 4' below the level of the stove. I am placing my infloor heat manifolds on this wall for the tie ins. The main line will then run another 31' to the plentumn on the forced air unit before returning another 31' to the water heater heat exchanger then the 72' back to the stove(103' all together each way). I will have 2 separate infloor heat manifolds which one will have 9 runs of 275' of 1/2" pex in the basement floor and the other has 6 runs od the 1/2" pex for the garage floor. Planning on using grundfos-alpha 15-55's for the manifolds, but trying to figure out the best, most efficient for the main line is really confusing me. Any help would be appreciated.
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What heat exchanger are you using for your domestic water, what size coil in the duct and cfm of the air handler, and what temp are you putting into the infloor loops might be helpful to know.
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30 plate with 1 1/4" inlet/outlets, 139,000 btu exchanger with 1" ports, 2100cfm max on the furnace. Going to hit 110 on the floor water.
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What kind of forced air furnace is it? And what air temps does it currently put out, and what percent of the time does it run on the coldest day of the year?
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Some rambles here. .
Another Alpha might squeak by, but run a really big delta t when everything kicks in. Would have to be plumbed dhw>air handler>infloor to work. That's a pretty big load when that air handler kicks in. Would knock out the dhw. Counter flowing through the coil can gain some air temp.
Something like a 26-99 Grundfos 3 speed would be a much safer and flexible option I would think... ? Dial your speed according to the delta t you can tolerate.
But I'd like to hear other opinions. Are there any bigger ecm pumps out there that are halfway affordable?
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What kind of forced air furnace is it? And what air temps does it currently put out, and what percent of the time does it run on the coldest day of the year?
Its a York- 96% efficient. Don't know the air temps and since the last winter was not that normal/cold here it's hard to say. Not really worth it to burn wood as I haven't even burned 900 gallons of L.P. in 16 months-January through april of 2016 house was being heated to 65 while finishing construction. This includes the furnace, DHW and the oven/stove. If I wasn't already in the firewood business, didn't have the stove and didn't want the floors in the basement and garage heated, I wouldn't be doing it. The house is extremely well insulated. Realistically, I'm sure I could have put in a small gas boiler and would be ahead if I wasn't able to use culls from firewooding. Just want to get the flow right the first time.
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The hard part about this is we don't know yet if the air handler is oversized or not with the air temps that you will get off of the coil. If the outdoor furnace that you're getting can tolerate low return water temps then low-flow with a smaller circulator won't be nearly as much of an issue. I would guess the 26 - 99 would have plenty of flow on high speed even if everything ran non-stop which it probably won't. There's where having a three speed is nice so you can adjust it back to save electricity.
But again I want to emphasize that if the domestic water is after any of the heat loads the required flow rate will have to be a lot higher because the water will not be hot enough to make a flat plate operate properly.
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The difference between the heat load the house will pull and what the emitters (coil, pipe in the slab) are capable of putting out might be quite a bit different. Sizing by the second may or may not be overkill, I have no way of knowing. So I'm guessing with the info we have to work with so far.
On my house I'd do another alpha, but I don't mind turning down the radiant til I could swap pumps if the radiant ran a little low on a bitter night.
I would not tee off for the radiant first in line on the main loop or when you kick it in the first day or two your forced air heat could suffer.
But putting a bigger pump would be the "safe" route if you don't want to worry about it, I just don't like burning extra electricity.
Ask three guys and you'll get three answers on flow rate needed based on what order the loads are pulled off the loop. I ways aim for the most efficient use of water temps and use a large delta t if possible. But a Heatmaster furnace return water is dispersed in the tank well enough and with recirc pump flow really low return water temps aren't an issue. On some the return water hits the firebox and can create a wet spot and rust it out. So my advise is for the brand I've worked with.
Is that too long-winded? :)
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Not too long winded at all. I appreciate the input. You are very correct about asking 3 people and getting 3 different answers on this one. I have my results from the furnace inspection guy when he was out setting it for the final time, but its all greek to me. If that would help, I could post that info for reference. I have the rest of the summer to decide. I am finishing hooking up the manifolds and soldering all of the piping in the basement, so I could just leave the pumps out for now.
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Any info about the gas furnace would help, also what order you are piping the flow on the main loop (this can change flow needed dramatically), what model of outdoor furnace you are installing.
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It's a York furnace, 96% effiencey rating, 100,000 btuh. Putting a Portage and Main BL3444 OWB in. Flow to appliances has not been established. Main line is into house-72' from stove, from here I need to hook up to furnace plentumn, DHW and to the infloor heat manifolds. I can go any direction I want to first. Was planning to go through 30 plate exchanger for DHW first, then 31' to the furnace and then pull out secondary piping, close spaced tee's for the infloor heat. What other info would you like for the furnace?
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Setup looks good to me, I'd be surprised you would need a 26-99, but a 3spd would let you slow it down if needed. That 1 1/4 main line is going to cut down on the friction and therefore need less head. Think you could use something a little cheaper. I'll let E Yoder coach you through it as it looks your getting it right.
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The BTU rating helps. So I'm assuming the coil in the duct is slightly oversized but that's great for airflow. Probably could run a 30 degree delta t and still put out 100,000 btu's to match (assumption being it was sized correctly). That would need 6.66 gpm. Since domestic water load is first in line and very intermittent that really doesn't affect gpm needed.
Looking at the Alpha pump curve I think it would work especially if you really try to minimize 90's. I'm assuming 1 1/4" all the way through except the coil.
That would give you 166,500 btu's (if we started at 170, 30 Dt across the coil, = 140) to dump into the floor at a 20 Dt on the 110 ℉ floor loop. 50℉ Dt on the main loop before and after the floor heat tees. Will that heat your basement and other building? I don't know. I don't know what heat loss they have.
I would check with P&M as to what they think about potential for occasional 90℉ return water temps. I do it on what I install but I'm not familiar with how the BL return water is dumped into the tank. You wouldn't want to cause continuous sweating on mild steel.
So I'm still thinking another alpha but I'd like to hear some other opinions. Actually I'be used quite a few B&G NRF-25's as it has a slightly higher gpm but still fairly low cost. Would gain you several gpm but use more electric as it isn't ecm.
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The BTU rating helps. So I'm assuming the coil in the duct is slightly oversized but that's great for airflow. Probably could run a 30 degree delta t and still put out 100,000 btu's to match (assumption being it was sized correctly). That would need 6.66 gpm. Since domestic water load is first in line and very intermittent that really doesn't affect gpm needed.
Looking at the Alpha pump curve I think it would work especially if you really try to minimize 90's. I'm assuming 1 1/4" all the way through except the coil.
That would give you 166,500 btu's (if we started at 170, 30 Dt across the coil, = 140) to dump into the floor at a 20 Dt on the 110 ℉ floor loop. 50℉ Dt on the main loop before and after the floor heat tees. Will that heat your basement and other building? I don't know. I don't know what heat loss they have.
I would check with P&M as to what they think about potential for occasional 90℉ return water temps. I do it on what I install but I'm not familiar with how the BL return water is dumped into the tank. You wouldn't want to cause continuous sweating on mild steel.
So I'm still thinking another alpha but I'd like to hear some other opinions. Actually I'be used quite a few B&G NRF-25's as it has a slightly higher gpm but still fairly low cost. Would gain you several gpm but use more electric as it isn't ecm.
I would like to think the furnace/air are sized correctly since I sent the house plans into the supplier and they designed the layout and made me move my location for the unit.
I have 1 1/4" run the entire way from the OWB to the furnace. The ports on the DHW plate exchanger are 1 1/4" as well. The way I have run the lines, I only have 3-90 degree elbows before reaching the furnace(total of 6 counting the return run). I have the capability to run the floor manifolds off a separate pump from the furnace if you think that would help. I actually put 2 main runs in from the furnace to the basement where the manifolds are so I could do it this way if it would end up being more economical. It may well be better to do this and run the ECM pumps to save the electrical costs. What do you think?
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What is the actual ID of the Logstor? (they use metric pex so if it was sold as 1-1/4 it is hard to say what you actually have)
What size is the plate heat exchanger and how many plates?
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I'd like to here RSI's opinion. Just from my experience I think one run could work.
I'm trying to think how you would do a second run and heat two different loads, would have to do P/S? separate circ from the boiler in, then tee off to the manifold pumps. I'd be a little hesitant to let the manifold pumps pull water that far, risks cavitation.
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The plate exchanger is a 30 plate, 1 1/4" ports, 5"x12". If I were to use both main lines from the OWB, I would definitely run 2 supply pumps as well. Since I am at work, I do not have the exact dimensions of the Logstar 1 1/4" pipe. I want this to work efficiently, but I don't want to end up using a boat load of electricity either though. I thought maybe I could run the infloor heat manifolds on 1 main line and the DHW and furnace on the other , but then after more research(possibly incorrect) it appears that I may be able to run it all on 1????????????? I just don't want to have to do it twice! Perhaps there is a way to run the infloor manifold pumps on 1 line and not run the main circulator until the infloor calls for more heat and the 3 way valve opens calling for hot water?????????????? Of course, maybe this is just not a cost effective thing to be doing either.
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I don't see any reason it won't work to put everything on the same line. When you get a chance, measure the ID of the logstor and post it.
I think an ECM pump would be enough. If it ends up being too small, you could add another in series and still use a lot less power than a large non ecm pump would use.
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That's about where I was heading. I'd do one line with an Alpha, then see how it works through a cold winter and add another Alpha in series if needed. I'll bet you won't.
You may have mentioned this but what is the total sq footage of both infloor slabs? Depending on the surface area of the floor you may be nowhere close to maxing out one line.
It might sound like I'm being too vague but without knowing the exact heat loss of the buildings pump sizing is a bit of a guess. To me, the small chance of needing to swap or add another pump after one winter is worth it to see if you can save some electricity. With an oversized pump you'll never know.
And having a spare Alpha on hand that can replace any of them is nice too.
Just my opinion.
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The garage is 1464 square ft, with 11' side walls. Basement is 2374 square ft with 9' walls. 1 wall of the basement is a walk out, 45' long. 3 windows-36"x54" and a patio door-72"x82". Wall is 2x6 with R-21 insulation, no other windows/doors in basement. Not really going to worry about keeping garage real warm, mostly to keep truck/car thawed in the winter-perhaps around 50 deg. With 3 garage doors(9'x8') it would be tough to keep real warm. Garage door company claims an R-13, just don't buy that when there is only 1 1/2" of insulation sandwiched in there. Floors are 5" concrete with 2" foam taped in place, vapor barrier under that and at least 6" of 3/8" clean chips I smoothed under that. Also have 2" foam glued to the foundation on the inside down 4' for a thermal break. I forgot to measure the Logstar last night when I got home. Maybe I can find it on my paperwork(doubtful). Just got my 1 1/4" copper pipe in this morning so maybe I can start the inside piping.
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Just looking at the sq footage... Radiant is limited to about 30 btu's per sq ft unless you run the slab surface temp over 85 ℉. Garage could do some more with the cooler temp walls/ ceiling.
So realistically the two slabs together can't pull more than 115,000 btu's total except on a cold startup. So add that to the 100,000 the forced air can pull... Am I thinking right?
I think a single 1 1/4" line with an Alpha should be fine. Some water may recirc back the second time through the floor but that's OK.
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Measured inside pipe the best I could without a micrometer, it appears that it is 1 1/8" inside. It is slightly deformed, and I was twisting it around to get an accurate measurement with my tape, but again, not a micrometer. Hope this helps.
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If it is Logstor brand then it should be 1.032" or 1.280". There is a huge difference between the two as far as head pressure.
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Well, I guess I'll cut off a chunk farther back and bring home a micrometer, but it should be 1.280 inches as you say. The piece I was trying to measure was an end that has had a deformity from being cut and tied up against the wall for some time.