Dual pump supply lines?

[Sawyer]

I have 2- 350’ loops of 1” Wirsbo Hepex off a 1 ¼x1x1” tee to supply 90,000btu min for the house and domestic h/w. Andrew at Wirsbo said that hepex 1”, 350’ loop, pumping 9gpm would produce a 10.55’ head. I am figuring a 12’ head including the fittings and HX.

Initially I was going to go to a Grundfos 15-58 but realized I would be running at the borderline of the curve on 3rd speed so I chose the Grundfos UPS 26-99 but after the recent discussions on flow and variable pumping conditions I am rethinking my order and plan to use 2- 15-58 Grundfos pumps, one on each 1” supply leg. I am thinking my head should stay the same but my flow would be cut in half. If I look at 4.5gpm @ 12’ it seems I am in the mid range of the pump speed. If I find out Slant Fin calculated high or low I am automatically covered by speeds 1&3;. in the summer when only the hot water is needed I should be able to run on one pump. The wto pump set up will be less costly also at $140 as compared to $239 and overall energy consumption will be lower. Another advantage is my other two pumps will be 15-58’s so only one spare would be needed if I chose to have one.

Before I order the pumps a question, is my thinking faulted?

Thanks, George

 

[BrownianHeatingTech]

I have 2- 350’ loops of 1” Wirsbo Hepex off a 1 ¼x1x1” tee to supply 90,000btu min for the house and domestic h/w. Andrew at Wirsbo said that hepex 1”, 350’ loop, pumping 9gpm would produce a 10.55’ head. I am figuring a 12’ head including the fittings and HX.

Initially I was going to go to a Grundfos 15-58 but realized I would be running at the borderline of the curve on 3rd speed so I chose the Grundfos UPS 26-99 but after the recent discussions on flow and variable pumping conditions I am rethinking my order and plan to use 2- 15-58 Grundfos pumps, one on each 1” supply leg. I am thinking my head should stay the same but my flow would be cut in half. If I look at 4.5gpm @ 12’ it seems I am in the mid range of the pump speed. If I find out Slant Fin calculated high or low I am automatically covered by speeds 1&3;. in the summer when only the hot water is needed I should be able to run on one pump. The wto pump set up will be less costly also at $140 as compared to $239 and overall energy consumption will be lower. Another advantage is my other two pumps will be 15-58’s so only one spare would be needed if I chose to have one.

Before I order the pumps a question, is my thinking faulted?

That's correct.

You'll have to figure out a control strategy. That could be a switch, or you could use a controller (eg, Tekmar 132). One nice thing about a pump sequencer is that it will automatically switch which pump is "lead" and which is "lag" after certain amounts of accumulated run time, so neither pump runs more than the other.

Joe

 

[Sawyer]

That's correct.

You'll have to figure out a control strategy. That could be a switch, or you could use a controller (eg, Tekmar 132). One nice thing about a pump sequencer is that it will automatically switch which pump is "lead" and which is "lag" after certain amounts of accumulated run time, so neither pump runs more than the other.

Joe

Boy Joe, if I had to use the Tekmar 132 it would sure eat up the potential savings. I will look at the idea of a switch and see if that will work out.

Thanks, George