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Cylinder stat added - weird problems since.

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  • 10-12-2013 10:28am
    #1
    SpaceTime
    Closed Accounts Posts: 9,088 ✭✭✭


    We've a fairly large gas-fired system and we'd some issues with the water being too hot in the hot water cylinder.

    Plumber arrived and decided it was because there was no stat on the cylinder.

    We've three zones which are just controlled by pumps, no motorised valves but they've always worked quite well.

    Zone 1 - Upstairs (switchable)
    Zone 2 - Downstairs (switchable)
    Zone 3 - Hotwater cylinder (controlled by boiler).

    We've thermostatic valves on every radiator, so we keep the room temp controlled with those.

    Anyway, the plumber fitted a thermostatic valve on the cylinder (he'd originally come to fix a leaky pump which he thought was caused by the water being too hot and damaging plastic fittings)

    The problem:

    When the valve is shut on the hot water circuit, the boiler goes completely nuts! It started rattling like crazy and the emergency relief valves opened shooting hot water out into a drain outside. (I think this is when the other two circuits are also stopped)

    I'm beginning to think that the boiler used the cylinder as a heat sink?

    That or there's some kind of a problem with its thermostat?

    There was also no flow at all on the cylinder circuit last night so I'm resorting to heating with the immersion again which isn't really how we would rather do things.

    Any suggestions?

    Could it just be air locked ? (The system was drained)
    Or, was that thermostatic valve a bad idea?


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    #2
    Sparkpea
    Registered Users Posts: 1,118 ✭✭✭Sparkpea


    I would have put a cylinder stat on the tank and wired it back to the pump so when your timeclock is set for HW to come on it sends power to the stat, if the stat calls for heat because the tank is cool then the boiler and pump would start.

    Post a pic of where he has put the thermostat and surrounding pics of the pipework to try eliminate what he may have done.

    Yes there could have been an airlock, is there any automatic air vents? is the system sealed or open vented?


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    #3
    SpaceTime
    Closed Accounts Posts: 9,088 ✭✭✭SpaceTime


    He installed a non-electric stat. It's similar to a TRV.

    It's an open system and yes it has automatic air valves which have been hissing away since yesterday.
    I bled the pumps a couple of times too as they were gurgling (they're actually quite high up in the system as it's an unusual split-level house)

    The boiler's quite high up in the system and the cylinder's at the very bottom. So, it's a little different from most layouts.


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    #4
    Sparkpea
    Registered Users Posts: 1,118 ✭✭✭Sparkpea


    SpaceTime wrote: »
    He installed a non-electric stat. It's similar to a TRV.

    It's an open system and yes it has automatic air valves which have been hissing away since yesterday.
    I bled the pumps a couple of times too as they were gurgling (they're actually quite high up in the system as it's an unusual split-level house)

    Yeah a piped in one, those are fine if fitted in the correct place, is there a byepass built into it or is there a byroads already on the system or none at all?


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    #5
    SpaceTime
    Closed Accounts Posts: 9,088 ✭✭✭SpaceTime


    There's some kind of a loop in the boiler house that seems to go from that circuit to a radiator circuit, which I assume might be a bypass?

    I think I'll vent all the rads and just make sure there's no more air in the system before I call him back.

    I'm not convinced that the water temp stat in the boiler itself is very accurate. It's some kind of Potterton thing but the controls are very vague just dots on a dial rather than ºC which is a bit stupid.

    Set at about 1/3 down the dial the rads are roasting which seems a little off to me. The boiler is stopping and starting though so it hasn't just failed completely. I'm just wondering if the probe isn't working properly or something.

    Never liked that boiler, seems to have been one electronic problem after another for years!

    The old Bentone oil burner it replaced just worked for decades without a hitch other than the odd nozzle and filter change.


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    #6
    My Skoda
    Registered Users Posts: 1 ✭My Skoda


    Hi Space Time, Only just read your problem. If other 2 zones have shut down and the cylinder valve shuts down the water has nowhere
    to go. Pressure and temp build up in system and boiler safety systems cut in. There should be a bypass on the cylinder valve to prevent this from happening.


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    #7
    SpaceTime
    Closed Accounts Posts: 9,088 ✭✭✭SpaceTime


    It's working fine again. I simply disabled the cylinder stat as there's really no need for it.

    The cylinder itself is very heavily insulated and we weren't really suffering from massive costs associated with heating it while the system's on.

    The coil was also heavily air locked which took me quite a bit of work to resolve.


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