Circ pump question

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Old 01-03-13, 10:35 AM
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Circ pump question

Almost two years ago, I installed a Tekmar 260....which is working just fine.

However, in this thread:

http://www.doityourself.com/forum/bo...ermostats.html


I mentioned that my single circ pump(a taco 007) does dead head a bit while the DHW zone valve opens up. It's been like that for two years, and it's still running fine, but I can't help but wonder if the pump is going to have an early failure due to the dead head?

So my question is....instead of installing a second pump just for the DHW, would an Alpha circ pump work in this situation? It's my understanding that it can sense the low flow, and adjust it's output to match.

Seems like I might save a bit on the electric bill as well.
 
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Old 01-03-13, 03:05 PM
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It won't be a problem. If it operated at shutoff head for a long duration, the plastic impeller might possibly overheat with no flow through the pump. You wouldn't save any electric energy - for one reason, a centrifugal pump consumes the least power at shutoff head. Not to worry.
 
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Old 01-04-13, 07:29 AM
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Thanks for the info. During heating season, the two heating zone valves are usually open most of the time. The indoor sensor on the Tekmar controls the room temp, so the t-stats are set 2 above the tekmar setpoint. Dead heading is not usually an issues during heating season.

During the off season though, is when I'll have about 1 minute of dead head time while the zone valve for DHW zone is opening. The tekmar wants to run the circ pump as soon as it gets a DHW call.
 
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Old 01-04-13, 08:19 AM
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I wouldn't worry about operating the pump at shutoff head for one minute.
 
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Old 01-04-13, 03:50 PM
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I wouldn't be concerned about it either...
 
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Old 01-04-13, 04:39 PM
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Taco 00-series pumps use a polypropylene impeller, which is good for at least 275 deg F. If you ran the pump at shutoff head for long enough, much longer than a minute, the water in the volute could heat up, form steam, and possibly damage the impeller.

On general principles, I keep a replacement pump cartridge on hand - it is the only moving part, and includes the impeller. If the pump shoots craps on Super Bowl Sunday, I can replace the cartridge in a matter of minutes (since I have isolation valves on each side of the pump). I also have a spare motor capacitor and a back-up generator. Beyond that, I could jack open my two flo-control valves, and go to gravity flow, assuming I still have natural gas. I'm sure there is another gotcha out there waiting to strike that I haven't thought of.
 
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Old 01-04-13, 05:12 PM
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I'm sure there is another gotcha out there waiting to strike that I haven't thought of.
Don't forget what's gonna happen on Dec 21, 2012 ! Or the New Madrid fault... or Yellowstone... or Nibiru...

The water flow also cools the motor to a degree so that could be damaged in the long term as well, but 1 minute of DH won't hurt a thing.
 
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