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Thread: Zone valve motor failure Ideal concord

  1. #1
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    Default Zone valve motor failure Ideal concord

    I have an Ideal concord CXA and its control system wired as per their recommendation for spring return zone valve. There are 4 zones 3 heating and one for hot water controlled by a 4-channel clock and respective thermostats. There is a requirement for one zone valve to be nominated as being open to dissipate the heat during pump overrun. I have the hot water as the nominated zone. The recommended wiring system results in the nominated zone valve being almost permanently open only closing when the system is running and the hot water not calling for heat.
    This means that the valve motor is permanently energised when the system is idle as it has a permanent live feed via a relay through which this zone valve is controlled as per recommended wiring diagram. This permanent energising of the valve results in premature failure of the motor typically lasting about 12-15 months. I do not think that this is a good control design. I have raised the issue with Ideal who have not been particularly helpful in commenting on their wiring recommendation. Does anyone have experience of such a control system? . I imagine that similar control systems exist with other boilers. I would have expected that when the pump overrun controlled from the boiler controls timed out the relay would be de-energised causing the valve in turn to close. I do have a solution but do not think at this moment it is particularly elegant and that is to add 2 further relays one powered from the time clock and one via pump over run feed from the boiler wired in an either/or arrangement such that the relay controlling the problematic valve will only operate when asked by the heating controls or by the pump over run. When there is no heat requirement or pump over run requirement then the problematic valve would be powered off when idle.
    Any comments would be very welcome.
    Thanks

  2. #2
    Moderator sunbeam's Avatar
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    isn't there a bypass built into the piping?

    the easiest way is to take the zone valve off the hot water and turn the cylinder stat up,

    or pipe one of the zones together with the hot water into a diverter so one port will always be open.

  3. #3
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    Many thanks for your reply.
    isn't there a bypass built into the piping?

    Yes there is but this does not affect that the valve is permanently energised. With the boiler being 40kw it needs a bigger heat sink than going around a bypass loop so the residual heat needs to go into a heat sink somewhere which is why Ideal have given the recommended control wiring diagram.
    the easiest way is to take the zone valve off the hot water and turn the cylinder stat up,

    I am not sure I quite understand this, won't it mean I have no control of hot water temp and what would the thermostat be doing. Without the zone valve it will have nothing to control anyway and water will end up same temp as boiler which is too hot for the shower valves. I face this problem anyway as too hot, hot water is the sympton of failure of the hot water zone valve.

    or pipe one of the zones together with the hot water into a diverter so one port will always be open.

    This idea looks like it might work I need to think this one through wrt to my control configuration. I am hoping to solve this through wiring rather than plumbing. When I installed the control system I brought all of the control cables (valves, thermostats etc) into one central connection box this makes it easier to toubleshoot the system from one central point just by using a multimeter. It also gives me the flexibility to change and add to this system within this central point.
    As a heating system what I have works and controls very well apart from when the boiler finally shuts down and the pump stops, the zone valve remains open. Ideally what should happen is that when the pump stops running at the end of overrun the zone valve is de-energised. I think this is a weakness in the design of the recommended control system but I can't get Ideal to comment on this.
    Thanks again

  4. #4
    Moderator sunbeam's Avatar
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    I canít see any other way of using a bypass other than using the boiler stat to control the hot water so locking open or taking out the zone on the hot water,

    If the hot water zone is energised permanently you are getting the same result,

    Or maybe pipe the bypass to the other side of the hot water zone (Iím assuming itís piped to the return) this way you could do away with the relays.

  5. #5
    Automated Home Sr Member NeilUK's Avatar
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    I'm assuming there is both a system pump output as well as the overrun output on the boiler. If so can you wire a relay coil into the system pump output and use the contacts in series with the overrun output? This way the overrun is only energised when both the system pump AND overrun are active, allowing the zone valve to close if only the overrun is active. This would give you your timed overrun control of the zone valve as well as the pump.

  6. #6
    Moderator sunbeam's Avatar
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    hi neil,

    but don't we want the valve to open on overrun?

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    Neil has given me a great idea. Sunbeam is correct in that I do need the valve to be open during overrun, what I think I can do is to change the existing permanent live that powers the relay that operates the problematic valve to the live the drives the pump. The pump only runs when either the system is calling for heat or during overrun. Therfore valve only needs to be available for energising during pump running. I do not need another relay just a matter of swopping one wire that feeds the current relay over to the pump feed. Before I do it, I will think through why Ideal have recommended the wiring diagram that they have, our solution at first blush seems too simple. Great inputs guys thanks very much.

  8. #8
    Moderator sunbeam's Avatar
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    i think it will back feed so keeping the valve energised

  9. #9
    Automated Home Sr Member NeilUK's Avatar
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    Quote Originally Posted by sunbeam View Post
    i think it will back feed so keeping the valve energised
    Yes, I see where you are coing from but I am assuming that the mains supply to the hot water valve end switch is wired through the hot water timer contact so the boiler only fires if the hot water timeclock is on and the zone valve is open (stat calling for heat). If the zone valve is open when the hot water timeclock is off (ie during overrun) then there is no mains supply to the valve end switch and therefore no feed to the boiler.

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