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Author Topic: Pump Size Confusion  (Read 3777 times)

DBeleskey

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Pump Size Confusion
« on: August 21, 2019, 07:49:33 AM »

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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mlappin

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Re: Pump Size Confusion
« Reply #1 on: August 21, 2019, 08:54:29 AM »

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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DBeleskey

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Re: Pump Size Confusion
« Reply #2 on: August 21, 2019, 02:22:44 PM »

The total sq ft of the house is 3000, 1500 main floor with finished basement.
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hondaracer2oo4

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Re: Pump Size Confusion
« Reply #3 on: August 21, 2019, 08:52:48 PM »

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 arenít returning boiler water back to the boiler below 140 which can cause firebox sweating.
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Re: Pump Size Confusion
« Reply #4 on: August 22, 2019, 02:45:31 AM »

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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DBeleskey

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Re: Pump Size Confusion
« Reply #5 on: August 22, 2019, 07:39:44 AM »

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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Re: Pump Size Confusion
« Reply #6 on: August 22, 2019, 10:02:32 AM »

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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DBeleskey

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Re: Pump Size Confusion
« Reply #7 on: August 22, 2019, 11:20:43 AM »

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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wreckit87

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Re: Pump Size Confusion
« Reply #8 on: August 22, 2019, 03:38:36 PM »

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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Re: Pump Size Confusion
« Reply #9 on: August 23, 2019, 03:50:33 AM »

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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DBeleskey

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Re: Pump Size Confusion
« Reply #10 on: August 23, 2019, 07:51:04 AM »

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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E Yoder

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Re: Pump Size Confusion
« Reply #11 on: August 24, 2019, 08:31:08 AM »

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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DBeleskey

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Re: Pump Size Confusion
« Reply #12 on: August 24, 2019, 04:35:18 PM »

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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wreckit87

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Re: Pump Size Confusion
« Reply #13 on: August 25, 2019, 08:06:35 AM »

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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Re: Pump Size Confusion
« Reply #14 on: August 27, 2019, 08:59:35 AM »

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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