1 pump or 2 that is the ?

[taxidermist]

Right now I have a eko 60 with a taco 013 on the boiler and a taco 009 hooked up from my storage tanks to my HX and side arm. Some have told me that I should try using 2 taco 008 pumps instead of 1 big 013 pump. If my system is a closed system with no check valves and my 009 runs all the time wouldnt this add to my pump flow when my boiler is running?


Rob

Ps I am ready for winter to be over!!

 

[Clarkbug]

Just out of curiosity, why did they tell you to replace a single pump with multiple pumps? Were you having any problems?

Taco has the pump curves available online for the 008 and the 013. I would say that you should get the pumps with a check, just to save future headaches.

http://www.taco-hvac.com/uploads/FileLibrary/curves003-008-IFC.pdf

http://www.taco-hvac.com/uploads/FileLibrary/curves009-0014-IFC.pdf

 

[taxidermist]

pumping 300' round trip with a taco 013 has to much head pressure.

 

[heaterman]

Rob, what you're up against is pretty simple. Once you reach a certain point trying to force more water through a given size tube or pipe, all you do is create more head. Sure you can stack more horsepower on it but you are still fighting the laws of physics and fluid dynamics. Diminishing returns is the concept at play here.
Personally I wouldn't advise going with two circs. You're just not going to gain that much compared to the ongoing electrical requirements plus you'll just wind up burning two of 'em instead of one.

Crunching some numbers using 300' of 1" pex and adding nothing more for other restrictions like your heat exchanger and fittings, the gpm and head look like this.

Taco 007/ 4.9gpm/ 9.7'head/ 4.1 psi differential pressure
Taco 008/ 5.8gpm/ 12.4'head/ 5.4 psi differential pressure
Taco 009/ 6.2gpm/ 14.4'head/ 6.1 psi differential pressure
Taco 011/ 8.3gpm/ 24.3'head/ 10.2 psi differential pressure
Taco 013/ 8.9gpm/ 27.3'head/ 11.5 psi differential pressure

You can see that once you get past around 6gpm in 1" tube, the head about doubles in order to produce only 30% more flow. (Again, send lumps of coal to the guy who sold you that pump and tube combination at Christmas time.)

Go back to the Taco charts posted above and look at where my numbers for each pump fall on their respective curves. Bear in mind that you always want to try and have a pump operating in the middle of its curve. That is where it's going to be most efficient wire to water.
The issue then becomes, can you maintain enough head on the suction side of that circ to keep it in positive pressure territory, especially if your water temps get into the 190-200* range occasionally. Keeping as much vertical distance between the top of the boiler's water level and the circ is about all you can do on an open system. Large diameter pipe feeding the circ will help to some extent.
Remember that 2.31 ft of head = 1psi. The only pressure you can generate on the suction side of the circ in an open system is the vertical drop to the circ. Usually this is less than 4-5 feet or only about 2-3psi. Look at the differential pressure on that 0013 (11.5) and you can see why you are having all the problems. The pump is probably almost always in a suction boiling mode and that ain't good if you want it to live a long and happy life.

If it was me, I'd look at increasing your heat emitter capacity so you can drag more btu's from a given water flow and decrease the pumping power required to do the job. Drop that 5-6gpm 30* and you can move some useful amounts of heat.

The 009 comes closest to hitting its sweet spot at a hair over 6gpm near the center of it's curve. Next in line would be the 007 & 8 but they are all going to be running on the high side of their respective curves.

Best of luck to ya.......and AMEN.......I am ready for winter to be done and gone too. My cousin with the sugarbush hung 500 buckets out this week so it's gotta be close.

 

[taxidermist]

Heaterman,

Thank you for your help. I have a new 009 I will try in the am when things cool off. I will have to look at what size my HX is its pretty big as I can heat my house with 120* water. I was just wondering if my 2nd pump in my closed system is still adding to my system? I want to make it only come on next year when the furnace calls for heat. I also want to maybe switch to a flat plate and pump on my DHW. As for the coal HELL no I will burn that! I should send him a pile of Dog Sh!% in a box


Rob

 

[heaterman]

Heaterman,

Thank you for your help. I have a new 009 I will try in the am when things cool off. I will have to look at what size my HX is its pretty big as I can heat my house with 120* water. I was just wondering if my 2nd pump in my closed system is still adding to my system? I want to make it only come on next year when the furnace calls for heat. I also want to maybe switch to a flat plate and pump on my DHW. As for the coal HELL no I will burn that! I should send him a pile of Dog Sh!% in a box

Rob

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