Circulator pump question?


Old 01-23-03, 08:32 PM
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Circulator pump question?

I've built a heat exchanger on my hot water tank. The exchanger will heat polypropolene glycose which will be pumped through some floor tubes in my garage pad. I've been looking at different pumps and its been suggested to me to use a Grundfos 1542 model. Now this model comes in a single speed configuration, and a 3 speed configuration. The sales guy said the 3 speed is the same as the single, just with a speed adjuster built on. He wasn't sure though how the speed adjuster works. My question is can most circulator pumps handle variable speeds?

I want to get the single speed version and vary the flow myself. I'm wondering if this is possible and will a simple dimmer switch do the trick. Thanks.
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Old 01-24-03, 06:12 AM
54regcab's Avatar
Join Date: Jul 2002
Location: Oklahoma City
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Lightbulb Why not single speed ??

I would just hook the single speed up to the thermostat directly, I see no advantage of a multispeed in your installation.
If you want to control water flow, all you need is a simple ball valve, it won't hurt the circulator
Old 01-24-03, 07:26 AM
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Running the pump at full power would waste power. Besides wouldn't that wear out the pump faster then necessary. I don't know much about pumps.
Old 01-24-03, 11:57 AM
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Join Date: Dec 2002
Location: Easton, PA
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I don't think those pumps ae made to start at all speeds. I remember an issue with a pump set to low speed and it would not start because of the reduced torque present at lower speeds. I also don't think you will see a pennys difference in your electric bill between runnin git on low or high. The newer pumps are way more efficient than the old 1/6 hp monsters. And quieter too. I prefer to use Taco pumps because I had problems with Grundfos pumps having impellers coming loose and not pumping water. Get the single speed and reduce the number of variables that can confuse a radiant setup.

The dimmer switch will NOT do the trick on an electric motor. You should not be planning on setting flows with the circulator. You should use a B&G circuit setter if you want to be fancy, or a full port ball valve if you are just a regular guy.

And I hope you meant propylene glycol. That glucose will draw flies.
Old 01-24-03, 12:30 PM
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Have had problems a couple places with trying to throttle with ball valves. Crud collected on the exposed part of the ball and made the valves very difficult to then close, and one pretty much tore up the seal and leaked.
Old 01-24-03, 12:49 PM
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Waste power? A Grundfos UP15-42 Pump has a 1/25 hp motor; that's .04 hp. They draw around 1 amp or a litle more than a 100 watt light bulb.
Old 01-24-03, 03:52 PM
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I guess I'll just go with a single speed pump. I was just concerned about the heat exchanger not having a long enough contact time with the liquid. I guess though the liquid will make more passes acrosss the exchanger in a given time slot. Maybe both methods work out to be the same amount of heat in the end.

I would think that installing a ball valve would make the pump work harder and limit its life span.

If the dimmer switch doesn't work then maybe using a transformer to step the 120 down would work. I probably won't do that, but I'm still curious.

The pump shop said they had a device that slowed down the pump and it basically frequency clipped the power. That sounds alot like a dimmer switch to me.

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