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Thread: Circulating pump - start capacitor

  1. #21
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    So, the pump's quite dead, and I've sourced a replacement. I had to track down a retailer by starting at the top - non-affiliated recommendations follow - Xylem Australia were very helpful* and put me in touch with Brown Brothers in Brisbane, who put me in contact with The Pump House in Beerwah. A new pump is on the way, and more about its future below.

    *The sales manager for Xylem was keen to hear about the way the pump was being used, and was surprised that it didn't last longer, but conceded that running it for long periods quite close to its rated temperature probably contributed to its demise.

    Now, onto the purpose of this post - how to make the new pump last longer?

    Heat management is the issue - the pump needs to be able to run cooler - specifically, the pump motor where the electronics live. Quite difficult when there's hot water only 1 or 2 cm away, running through a highly-conductive bronze housing. There's a couple of ways to do this, and I'd like some opinions on my ideas.

    1. The pump is located on the hot part of the loop - quite close to the output of the boiler. Would it be better to relocate the pump to the "cool" side of the loop, i.e. after the water has been through the towel rail and is considerably cooler than before?

    2. Provide active cooling for the pump. I can put some cooling fins around the jacket, dab a little arctic silver to help, and wire a ducted computer fan in parallel with the thermostat circuit, i.e. the pump turns on, so does the fan. This is obvioulsy more complex than option 1, maybe I should do both?

    2a. Drill holes either side of the motor housing (where all the electronics live), and duct some of the fan's air through the inside of the motor housing to carry heat away. Suitably grommeted and/or siliconed to keep moisture out. Also use netting or a filter on the fan's input side to keep dust and insects out.

    Thoughts?



  • #22
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    Perhaps look at a pelter plate or move the motor away from the heat source ie extend the shaft but the thing to know is how long does it take to heat up to how long is it on for ???
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  • #23
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    1. The pump is located on the hot part of the loop - quite close to the output of the boiler. Would it be better to relocate the pump to the "cool" side of the loop, i.e. after the water has been through the towel rail and is considerably cooler than before?
    I think you have your answer right there.
    I'm out of my mind, but feel free to leave a message...

  • #24
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    Hi - I can't move the motor away - it's an electromagnetically-powered impeller that's motivated by the rotating magnetic field in the pump motor. The impeller is also "part" of the motor pump housing, and it mounts on to the bronze housing, using a bronze screw-ring.

    It goes: plastic housing with electronics, bonded to a metal cup, in which sits the impeller on top of a ceramic bead (the bearing), which mounts to the bronze water inlet/outlet housing, using a bronze screw-ring. I literally cannot move the motor (electronics) away from the heat, I can only mitigate the heat, by moving the whole pump onto the cooler side of the loop, or by removing heat from the pump motor more effectively, or both.

    Worst part - the pump motor housing is plastic and doesn't conduct heat from inside to outside very well, so I don't really like the cooling fins/heat-sink idea. Getting outside air to circulate through the inside of the pump motor is the preferred option at the moment. Moving the whole pump to the cool side of the loop is not accounted for in the original installation instructions. Crude picture: yellow 'O' are holes drilled through the sides of the pump housing, using a pipe to force air through the inside, and out the exit hole.


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    I think LSemmens is right. The best solution, the simplest, is to move it away from the heat altogether. I *could* also just point a fan at it without heatsinks or ducting or drilling holes. hinekadon, the pump's duty cycle overall is less than 50% - it'll switch on, work for as long as it takes to reduce temperature and then off again. It takes less time to reduce temperature than it takes to build up again. I've never measured it, but - grabbing vague memories here - it's on for about 30-60 minutes, then off again for an hour or two. It depends on where I set the thermostat. It tends to be higher during winter. Thanks everyone for your thoughts.

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    thanks for that you, may find that you can fit a piece of 6mm ali plate on to the housing that will increase the time difference to allow you to run it for less duty cycle just sitting in free air depending what size plate you can fitt in the area the bigger the better ??? should save moving this and that around and the plate only has to have a small contact area with the pump body to be effective .
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  • #27
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    Drilling holes will void your warranty.

    The pump has intense thermal contact with it's metal part to flowing hot water. Moving air can't compete very well with that, heat sinks would have to be very large to have any effect and getting good thermal contact with the surface all around the pump is difficult.

    The best you could do is remove the plastic cover entirely and mount a fan right over it, the fan becomes the cover but with a gap for the air to escape. This wouldn't void your warranty unless there is a sticker between the pump housing and the cap.
    You would periodically need to check for dust build up, although that is less likely than if you were to force air through the closed enclosure.
    Wrap the entire thing at least loosely with fly screen to avoid vermin excrement.

    Moving the pump to the cold side is still the best option if you can do that yourself. Getting a plumber will exceed the cost of a new pump.
    Last edited by Uncle Fester; 05-05-19 at 12:55 PM.
    This era of thoughtless consumption must end so we can encourage a world of creative geniuses rather than consumer idiots.


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  • #28
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    "remove the plastic cover entirely and mount a fan right over it,"

    Now there's an idea!

  • 12-07-19, 06:28 PM


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