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New Build Dual Zone Heating.. help needed!

Discussion in 'Plumbing and Central Heating' started by Tom Dodwell, 19 Jan 2019.

  1. Tom Dodwell

    Tom Dodwell

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    Hi, I’ve recently moved into a new build house which has dual zone heating. The problem is the upstairs thermostat controls both the upstairs and downstairs radiators and the downstairs thermostat doesn’t seem to control anything! I’m wondering if something has been wired up wrong... the system has 2x Danfoss HPA2 valves. I’ve attached a picture of the wiring in the junction box, can anyone see anything noticeably wrong with the way it has been wired? Many thanks in advance!
     

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  2. stem

    stem

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    The photo doesn't really help that much without knowing specifically what each of the wires in the photo is connected to at their other end.

    Unfortunately, there is not set format for the wiring colours or cables used; they would have been chosen by the original installer based on their personal preferences and the various components used (ie thermostats & boilers) don't all have exactly the same connections.

    However, some things are identifiable. In the photo below

    Capture.JPG

    The two brown wires in the bottom of the terminals circled are the switched lives going to the two motorised valves (one for each zone) and the black wires with the brown sleeves above, that are in the same terminals should be the switched lives from the two room thermostats. So it looks as I would expect. The question is: Do the two black wires go to the 'switched live' of the appropriate room thermostat as they should, and from the photo it is impossible to tell.

    As it's a new build house the recourse should be for the builder to rectify it. If you try to DIY fix it and get it wrong, or damage a component they will be unlikely to honour any warranty.

    It is of course possible, albeit more unlikely, that the motorised valves could be wired and working as they should be, but they have been incorrectly installed into the plumbing.

    If you operate the room thermostats one at a time and have someone listening at the motorised valves you should be able to hear a whirring noise as they close when the thermostat switches off. If they both 'whirr' when the upstairs thermostat goes off they are indeed incorrectly wired. [If you do this test, allow 30 seconds for the valve to fully wind open first before turning the thermostat down]

    From the test, should you find that one room thermostat operates one valve, and the second thermostat operates the other valve then the wiring would appear OK.
     
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  3. Tom Dodwell

    Tom Dodwell

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    Firstly thanks a lot for your reply and help.

    I’ve done the test which you said and it seems extremely strange as both valves work as they should, I can hear the one engaging for downstairs and the same upstairs. However when the upstairs thermostat is turned on all of the radiators in the house heat up apart from the master bedroom and when the downstairs thermostat is turned up only the master bedroom radiator warms up! So I guess this could mean it has been incorrectly plumbed? I don’t understand how they can mess it up that much so only one upstairs radiator is plumbed into the downstairs circuit and all the rest are plumbed into the upstairs circuit! Very strange!

    I will speak to the builders about this, I was reluctant before as I’ve changed both thermostats to the Hive smart ones (I had the same problem with the original thermostats, just thought it was a dodgy thermostat). Didn’t know if it would void the warranty as I’ve changed these.

    Again, thanks for your time and help.
     
  4. stem

    stem

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    The wiring sounds OK then, and to be honest, even though it's not possible to see all of the wiring what is visible looks OK. Regarding the warranty, I was thinking more along the of if you accidentally caused any damage to the boiler for example. I wouldn't have thought changing a thermostat would be an issue.

    So it does sound like the pipework is at fault. Unless the way it's operating is the way it was designed to operate. Bit odd though if it was.

    Once you have resolved it, please post back the outcome. I would be interested to know.
     
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  6. jeff the gasman

    jeff the gasman

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    Some reverse circulation going on if valves are operating normally.
     
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