Outdoor Wood Furnace Info
All-Purpose OWF Discussions => Plumbing => Topic started by: DBeleskey on August 21, 2019, 07:49:33 AM
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Hi Everyone
I am to the point of choosing the circulation pump for my Polar G2 furnace. I have mentioned pump sizes here before and it was suggested that I use the Grundfos UPS 26-99. I thought I was all set to go until I went to order the pump from my supplier. He said he had them in stock but asked why such a big pump. I told him my setup and he said he though the a UPS 15-58 would be all I needed and at a considerable less cost. Now I am really confused.
My boiler is about 80 feet from the house, the run is LogStor 1" pipe to the house. Once inside I switch to 1" copper, which goes from the LogStor up the wall about 8 feet to the ceiling. Then the copper goes across the ceiling about 16 feet to a plate exchanger for DHW then about 8 feet to the water to air exchanger in the furnace then back to the Logstor.
I have a heat loss done when I built the house last year but not sure how to use that information to do the correct calculations to figure out what pump size I need. I don't want to go under sized or over sized if possible.
Any help or suggestions would really be appreciated .
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The 26-99 on low is a step above a 15-58 on High.
Whats the sq ft of the house?
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The total sq ft of the house is 3000, 1500 main floor with finished basement.
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You want to shoot for a 20 degree drop after your hx when it is calling for heat. You have a relatively short run which is similar to mine. I have 75 feet of logstor and then about 50 feet of 1 inch in the house. With my 24x24 water to air hx I get around a 20 degree drop on speed 1 with a26-99. You may be able to get away with a 15-58 on high. You need to insure though thst when your boiler is at the low end of its set point (160?) that you aren’t returning boiler water back to the boiler below 140 which can cause firebox sweating.
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Does the Polar have a recirculation pump? If so it should mix the return water and prevent sweating? If so I'd do a 15-58 on high speed. The job I'm doing today will use a 15-58, they're great little pumps.
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The Polar G2 does have a recirculation pump..
I am a little afraid of the 15-58 running on high speed and not doing what I need. At that point I have no further to go other then get a bigger pump. I would try the 15-58 if it would work for my garage when I get it insulated but, it has more head than the house so, it won't work there.
The 15-58 is half the cost but I could end up eating it and buying the bigger 26-99 anyway ?
I don't know...
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The 15-58 should work fine and will use a lot less power than the 26-99.
Will your supplier exchange it for the 26-99 if it is too small?
What will be in the garage loop?
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I wouldn't imagine he would be willing to take it back if its too small. He is a few hours away from me and i have it shipped here so there is that too.
The loop to the garage is about 50 feet of LogStor to the garage slightly uphill. Then copper up to the ceiling where the air exchanger will hang, about 15 feet to ceiling. Don't think the 15-58 has enough head to push it that far ?
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What did the heat loss come back at? What size is your HX? The uphill battle to the garage plays no role in pump sizing, as the return trip will cancel out whatever was lost on the way up. With only 80 feet of Logstor, you should be able to push roughly 6-7 GPM with a 15-58 on high or 8-9 with a 26-99 on low. With a 20 degree delta T, those numbers are linear to BTU output (6 GPM = 60k BTU, 9 GPM = 90k BTU). With a worst case scenario DHW call of 4 GPM, you've got 120,000 BTU there alone to get 50 degree groundwater up to 110 degrees which at 6 GPM would hand you a 40 degree delta. If at the bottom of a cycle with 160 degree supply water, that brings your return down to 120- well below condensing temperatures. Add a simultaneous central heat call, you're flirting with disaster. What I would do, is head over to eBay and buy a 26-99 for $150, likely not much more than your supplier was going to charge for the 15-58, and yield the cheap insurance that your boiler will live a healthy life. As for the garage, same rule applies but will depend again on heat load and HX size to determine necessary flow rate.
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I guess I was thinking the recirc pump eliminated the concern about condensing. But anyway, like wreckit said height makes no difference once the air is purged out. Just plumb in a fill valve at the water heater and maybe a hose outlet on the shop loop to use domestic water pressure to purge.
Those eBay 26-99's are a great deal.
Interestingly, I used a 15-58 yesterday on a 130'+ loop. Heated fine with a five ton air handler.
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Sorry I am new to this. I don't know what you are asking for with the heat loss and HX ?
I am from ON Canada. I can't find those pumps for $150 here. If I order from the US I get nailed big time for duty and brokerage fees. Sometimes more than the price of what I buy. The cheapest I can find here is $298 USD or $398 CAD for the 26-99.
I was offered a Chinese knock off of the 26-99 for $275 but I think I will steer clear of those.
I did plumb in a fill valve in the basement, figured much easier then trying to fill outside in the winter.
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HX refers to the hot air heat exchanger. Also knowing the cfm of the blower would get some idea of heat load.
You could also look into a B&G NRF-25, it's a good compromise between the 15-58 and 26-99 at a good price.
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I actually found a fairly good price on the 26-99 flanges included for $380 CAD shipped, thats the best I found so far.I will likely go with that and see what happens. Now I have to figure how to connect the pumps at the back.
I will look around and see if anyone has any pictures of what they did.
Thanks again everyone .
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You said you had a heat loss done when you built the house. That number would be a 5 digit BTU amount, which refers to the amount of BTU lost through the walls, ceiling, windows, doors, etc on a "design" day (the coldest day of the year) that needs to be replaced with the furnace. With that number, we would be able to determine your necessary flow rate
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There are a lot of places with BTU numbers. The one that looks like what you are asking about says Heating Load: 44616 Btuh
Other s that I see:
Heating input 60000 Btuh Sensible cooling 12600 Btuh
Heating output 56400 Btuh Latent cooling 5400 Btuh
Actual air flow 1075 cfm Actual air flow 600 cfm
Air flow factor 0.024 cfm/Btuh Air flow factor 0.038 cfm/Btuh
Thanks
Dave
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Thanks- 44,616 would be the design heat load. They have installed a 60,000 BTU furnace, which at 94% efficiency will yield 56,400 output. With 1075 CFM across the coil, you'd need roughly 110 degree discharge air to meet the sensible load. This would require only about 5 GPM at a 20 degree delta from 175* EWT to 155* LWT. Add a domestic load to that however, and we have a problem with very low return temps. If I were me, and I'm pretty sure I am, I would still splurge for the 26-99 and keep the flow rate up at 8-9 GPM. That way there are never any surprises to your boiler, and never any trouble heating the house and DHW simultaneously. I don't mean to spend your money, but the extra couple hundred bucks for a proper system goes a long way when you're risking mistreating a $10k+ boiler. Why gamble?
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Thanks very much...believe it or not, that makes sense to me:)
I was still leaning toward the 26-99 but after reading your post, I am sure now. I agree, why play with trying to save a couple of hundred bucks and risk the investment on the furnace not working correctly. Then I would have to purchase the 26-99 later and eat the price of the smaller pump.
Thanks for the great explanation.
I feel more confident now.
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No problem, happy to be of assistance. Let us know when you get that thing fired up!
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Okay will do. Just trying to figure out how long to leave the logstor inside the furnace for pump connections. Would make it easier to cut the insulation off before the furnace is set on the pad. Might get a better idea of what needs to take place once the pump gets here and I can see it and the flanges. Like I said before, i am new to this so i can't get a picture in my mind what it should look like and i have searched around for some pictures but can't seem to find any.
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I'm not familiar with the Polar but anything else you want as much insulation on the Logstor as you can muster. It's not all that tough to get the jacket off even in tight spaces, and then what I do is wedge two pipes or pry bars in the pex and pull one toward me while pushing the other away. It usually blows the foam right off the pex and there you have it. Could always wait until the stove is sitting there and pre-plumb the pumps and get it ready to connect, measure from the feet to the adapters. Then head to the pad and measure up the Logstor whatever that distance was, plus 6" and TAPE THE ENDS SHUT. Drop the stove over the top while making sure nothing binds and when set, peel 18" of jacket off (heh, jacket off- get it?), then mark and cut your tubing to the correct height. Make connections and fill with water!
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Thanks for that suggestion. I have a small piece of pipe here that I can practice getting the "jacket off" on. Practice makes perfect :)
My pump will be here next week. I think if I leave about 6 inches of insulation on above the pad that it should be okay...I hope.