Results 1 to 10 of 10

Thread: Upgrading Existing Zone Valve System

Hybrid View

Previous Post Previous Post   Next Post Next Post
  1. #1
    Automated Home Guru
    Join Date
    Nov 2015
    Posts
    153

    Default Upgrading Existing Zone Valve System

    Hi

    I wrote before about upgrading my existing 3 zone heating system to Evohome I have 3 Heating Zones with a Zone Valve associated with each one no Hot Water zone

    The System I was playing with before I have now installed in my Daughters Apartment and it works great 3 Zones all with HR92s and Evocontroller as Temp Sensor in Living room Zone

    I am now going to do my own system I was wondering how to deal with existing Zone Valves if I decide to go all HR92 Route do people normally latch them open or wire them into Boiler Demand Relay so they always open when Boiler is on

    Or if i decide to keep zone valve on one zone with a Temp sensor for that zone can this be done

    thanks
    mylesm

  2. #2
    Automated Home Legend
    Join Date
    Sep 2014
    Location
    Scotland
    Posts
    2,361

    Default

    If your system is a combi with no hot water zone valve then the easiest way to bypass the zone valves would be to wire all three of them to the same power source as the pump, assuming that is possible and that it's a conventional switched 240v pump.

    That way they remain open any time the pump is running (including pump overrun) but they will close when the pump stops both to save power/heat and prevent seizing. If you have HR92's on all radiators you don't need any zone valves.
    Last edited by DBMandrake; 14th February 2017 at 03:52 PM.

  3. #3
    Automated Home Legend paulockenden's Avatar
    Join Date
    Apr 2015
    Location
    South Coast
    Posts
    1,719

    Default

    Won't that mean there will be a second or so when the pump is running but the valves are still opening? do opening valves start to pass water from the start of travel?

  4. #4
    Automated Home Legend
    Join Date
    Sep 2014
    Location
    Scotland
    Posts
    2,361

    Default

    Quote Originally Posted by paulockenden View Post
    Won't that mean there will be a second or so when the pump is running but the valves are still opening? do opening valves start to pass water from the start of travel?
    If there are two port heating zone valves already in place there must be an automatic bypass valve if there is any pump overrun, or the system would have already suffered from the problem of pump running with nowhere for it to go.

    Although it takes 15 seconds to fully open there is some flow after a couple of seconds.

  5. #5
    Automated Home Legend paulockenden's Avatar
    Join Date
    Apr 2015
    Location
    South Coast
    Posts
    1,719

    Default

    Just think it might be better to have the pump running off the back of the valves, rather than the other way round.

  6. #6
    Automated Home Legend
    Join Date
    Sep 2014
    Location
    Scotland
    Posts
    2,361

    Default

    Quote Originally Posted by paulockenden View Post
    Just think it might be better to have the pump running off the back of the valves, rather than the other way round.
    There are a few different approaches you could take with different pros and cons.

    If I take your suggestion literally you would have the BDR91 power the boiler, then have the pump control from the boiler which normally goes to the pump power the zone valves instead of the pump directly, and then power the pump from the orange wires of the zone valves.

    The advantage to that is you ensure the zone valves are always fully open before the pump starts so in theory you don't need an ABV. But that is also its downfall - the boiler will start burning for 15 seconds before the pump starts running - not good for the heat exchanger! I wouldn't recommend this approach for that reason.

    Any other wiring configuration will require an automatic bypass valve if there is any pump overrun, which there will be, unless it's an antiquated system like mine. (Which originally had no overrun until I added a timer) Also if you power the zone valve from the BDR91 directly you will end up with the zone valve being TPI modulated and pump overrun looping through the ABV every TPI cycle off cycle, which I think we agreed in another thread is not optimal, and hence why I documented the wiring changes I made in my S-Plan thread.

    Perhaps mylesm can tell us whether his system has pump overrun (boiler controlled or external timer) and also whether he has an automatic bypass valve, otherwise we could end up speculating on all kinds of different scenarios that aren't relevant.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •