Trying to understand my Faulty boiler understand - Help Please

Discussion in 'Plumbers' Talk' started by Jr23Smithy, Oct 1, 2016.

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  1. Jr23Smithy

    Jr23Smithy New Member

    I've been having a few problems with my boiling system over the past year and finally had enough. The system is quite old now came with the house (around 30 years old).

    It is a Sealed System, that auto fills fill from the mains and I believe its 'W plan with two port valve' from investigation last year. As the system has priority hot water over heating, we never get heating as the water temperature is constantly heating. We get around this my manually overriding the port valve to heating when we want heating.

    The system does work, meaning port valve switches over when I have set the room thermostat to high and the tank thermostat to low. I was advised that the tank thermo needed to be around 70-80 degC., but when the house gets down to 12 degC in winter (room thermo set the 20 degC) we still don't get heating as hot water apparently doesn't get up to temp...

    I found today that the expansion vessel (Zilmet Z50) on the system leaks water from the Schraeder valve, so I deduct the diaphragm has degraded. Do I have to replace this one for one or can I replace with any 0.5L vessel?

    Would you be able to advise me please?
     

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    Jr23Smithy, Oct 1, 2016
    #1
  2. Tricky Dicky

    Tricky Dicky Screwfix Select

    Hi
    I'm not a plumber, but the following might help:
    The boiler temp needs to be set at a higher temp than the Domestic Hot Water thermostat, otherwise the diverter valve will never 'move' to the Central Heating position.
    The W plan gives priority to DHW.
    Your DHW thermostat set to 70-80 C seems a little high, could it be reduced to 60-65 C ?
    Would a Y plan be better, as this gives sharing to both CH and DHW at the same time ?
    This would require a new diverter valve, and slight changes to the wiring at the control centre. A gate valve would surely be required on the hot water supply to the storage tank ( to balance the two circuits ie DHW and CH) otherwise when the diverter valve is 'sharing' all the hot water will still go to heating the stored hot water.
    My heating system, that I designed, is a S plan with 3 separate valves for HW, Upstairs heating circuit and Downstairs heating. Three separate valves, and timers, so that all 3 circuits can operate independently. (HW timed to operate when space heating not required, ie very early morning; Upstairs space heating left on overnight when outside temps very low, etc).
    Sorry can't help with the expansion vessel.
    Hope this helps.
     
    Tricky Dicky, Oct 1, 2016
    #2
  3. Dave does Gas

    Dave does Gas Screwfix Select

    Ill honest with you, given the amount of issues your having Id say its time to bite the bullet and get yourself upgraded to a modern system. Call in a couple of logal Gas Safe fitters, get a few quotes and make your decision.
     
    Dave does Gas, Oct 1, 2016
    #3
  4. kiaora

    kiaora Guest

    Hi
    Looking at the pipe work, I can't believe it ever worked properly.!

    The hot pipe from the tank seems to be connected at the bottom of the tank?

    The pump position ?
    Well, it's totally in the wrong place,

    Depending on the budget available, either, get an experience heating engineer the re pipe the system, or replace?

    It also doesn't look like a sealed system, the expansion vessel is for the hot water pipe work only.

    Regards
    Peter
     
    kiaora, Oct 2, 2016
    #4

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