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Thread: Upgrading Existing Zone Valve System

  1. #1
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    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

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    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 02:52 PM.

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    Automated Home Legend paulockenden's Avatar
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    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?

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

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    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.

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    I Have a worcester Bosch 24ri Open Vent Boiler this is switched externally by the Zone Valves via Boiler Interlock Pump is a wilos Pico Modulating Pump powered from Boiler which has a pump over run

    I have no ABV but I have a bypass Rad in a hall which up to now has always worked well I am now awaiting Delivery of new Evo Controller and 8 HR92 Heads

    I think now I will Disconnect Zone Valves and take heads off them and put Valves into open Position makes life easier

    Thanks for input and advise

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    Quote Originally Posted by mylesm View Post
    I Have a worcester Bosch 24ri Open Vent Boiler this is switched externally by the Zone Valves via Boiler Interlock Pump is a wilos Pico Modulating Pump powered from Boiler which has a pump over run

    I have no ABV but I have a bypass Rad in a hall which up to now has always worked well I am now awaiting Delivery of new Evo Controller and 8 HR92 Heads

    I think now I will Disconnect Zone Valves and take heads off them and put Valves into open Position makes life easier

    Thanks for input and advise
    If your bypass radiator is AFTER one of the zone valves, it's not a bypass radiator as that zone valve would isolate it.

    I think given what you describe disconnecting the zone valves and fitting fixed heads (you can usually get a head with a manual knob to lock them fully open) is your best bet. At a pinch you could set them in the latched filling position but as this only opens the valve about half way it can cause some flow restriction that is probably best avoided.

    I would probably manually close and re-open the valves once a year just to make sure they don't seize up.
    Last edited by DBMandrake; 15th February 2017 at 08:57 AM.

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    Quote Originally Posted by DBMandrake View Post
    If your bypass radiator is AFTER one of the zone valves, it's not a bypass radiator as that zone valve would isolate it.

    I think given what you describe disconnecting the zone valves and fitting fixed heads (you can usually get a head with a manual knob to lock them fully open) is your best bet. At a pinch you could set them in the latched filling position but as this only opens the valve about half way it can cause some flow restriction that is probably best avoided.

    I would probably manually close and re-open the valves once a year just to make sure they don't seize up.
    Thanks

    Bypass Rad is before all Zone Valves I think I will Just open Zone Valves and install all Hr92 Valves except on bypass rad

    I will Then have one Boiler Relay and 8 Hr92s some controlled by Yr87f stats in Living areas and use HR92 Sensors in other areas

    Should be Fun next weekend setting it up

    thanks again
    mylesm

  10. #10
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    Well all my New Evohome Gear arrived last night just spent this morning installing 8 Hr92 Valves all are single Zone except Kitchen which has 2 actuators in same zone

    Kitchen and Hall have Round Wireless Stats as Rads are covered Living room is using Evohome Controller as sensor with a 1.5 degree offset

    All the rest are using Hr92 sensor for temp measuring

    I took Heads off Existing Zone Valves and disconnected them electrically and opened them so they are basically gone

    Boiler is now switched by BDR bound as a Boiler Demand Relay All seems to be working well so far

    One Question As the Hr92s are Modulating Valves do People leave their Pump at Constant Speed or if they have a modulating pump as I have do they leave it modulating

    Thanks SO far Glad I upgraded

    mylesm

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