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Thread: Using a CS92 to control a DHW circulation pump ... ?

  1. #1
    Automated Home Sr Member
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    Nov 2017
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    Default Using a CS92 to control a DHW circulation pump ... ?

    Because Evohome can't be used as a timer my DHW circ pump is controlled by a standard CH programmer. I was about to add a pipe stat and then thought ... perhaps I can control it with Evohome by using a second CS92+BDR91, with the sensor strapped (with thermal paste) to the DHW return pipe.
    I presume I can't bind two CS92s to the same controller (is that correct?) but I have two controllers (lots of zones) so, presumably, I could use the DHW binding on the second controller for the circ pump control.
    Any reason why any of this wouldn't work, or any better ideas?

  2. #2
    Automated Home Ninja
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    Quote Originally Posted by DorrisMancer View Post
    Because Evohome can't be used as a timer my DHW circ pump is controlled by a standard CH programmer. I was about to add a pipe stat and then thought ... perhaps I can control it with Evohome by using a second CS92+BDR91, with the sensor strapped (with thermal paste) to the DHW return pipe.
    I presume I can't bind two CS92s to the same controller (is that correct?) but I have two controllers (lots of zones) so, presumably, I could use the DHW binding on the second controller for the circ pump control.
    Any reason why any of this wouldn't work, or any better ideas?
    Why would you want to control it with a pipe stat? The idea being it continuously pumps HW round the house during occupied times, I can't see any advantage to temperature control. What I can see is that when the cylinder is fully reheated, that then the pump kicks in so that it isn't pumping round HW when the cylinder is reheating. This would be easy to do by wiring the Circ pump to the C port on the HW BDR91. You can then add a standard programmer after this to control times.

  3. #3
    Automated Home Sr Member
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    Once the DHW loop is full of warm water there's no need to run the circulation pump, doing so just stirs-up the water in the cylinder. When the cylinder is up to temperature the water is leaving at about 60 degC, but my guess is that I would only want to run the pump when the loop temp has fallen to about 30 degC. Many DHW circ pumps have a built-in stat but mine does not.
    I can't see any reason why you would not want the pump to run when the cylinder is reheating - hot water is still needed at the taps.
    I already have a standard timer controlling the pump and was about to fit a pipe stat, but the ability to control the pump via the App would be useful. Whether the utility is worth the cost of a CS92+BDR91 is another question that I haven't resolved yet. Where's the cheapest place to buy them?

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