New shower off combi boiler - water runs hot then cold

Discussion in 'Plumbing and Central Heating' started by LMN, 21 Jul 2011.

  1. LMN

    LMN

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    Can any body help? I have had a new shower installed (Grohe) connected to the combi boiler (Heatline) but cannot find a way to have consistant water temperature. It runs hot for 4 -5 minutes, then cold and back up to warm. I have lowered the combi boiler water temperature to the lowest it can be and the same happens. Any suggestions please?
     
  2. kevindgas

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    was a pressure Equalizing valve fitted to the shower inlets? i suspect not! as a result there isn't equal pressure on the showers cartridge causing it to move which in turn causes problems to the boilers modulation. an all too common problem caused by untrained plumbers that have done a 6 week course and think they now how to install
     
  3. Agile

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    I am often critical of inexperienced people working on boilers and plumbing but in this case I think Kevin may be being a little too critical.

    The Grohe are very good products and work well with combi boilers.

    In this case I would suspect a possible problem with the boiler temperature control system. Very unfortunately few boiler engineers would have the knowledge or interest to fully check all aspects of the boiler operation.

    There are a couple of tests you could do which may help us to assimilate whats going wrong. First identify the hot water outlet pipe from the boiler and feel it while the shower is being used and see what it is doing.

    Next run a hot water tap at about 3 litres per minute while the shower is being used and see if that makes any difference.

    An important aspect is to have the temperature control on the boiler lowish. You say you have done that but is it actually altering the DHW temperature?

    Tony Glazier



    PS
    May be a stupid question but it should be asked! Has the hot/cold been correctly connected to the shower?
     
  4. LMN

    LMN

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    the shower was fitted by the company installing my new bathroom, including the shower - this is something I can ask them. Thanks
     
  5. LMN

    LMN

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  6. Agile

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    DHW stands for domestic hot water.

    People installing bathrooms are usually primarily carpenters/tilers and many have only very basic plumbing knowledge as thats all thats required for that job.

    A real experienced plumber able to diagnose and repair shower problems are difficult to find. I usually suggest shower manufacturers service agents.

    In this case it seems you might be able to blame the bathroom fitters ( although it could still be the boiler.

    Does the shower temperature adjustment seem to operate correctly and in the expected direction?

    You have not answered my question about the DHW output temperature at the boiler while the shower is on.

    Tony
     
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  7. LMN

    LMN

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    thank again - and for the explanation - I will try the DHW output temperature at the boiler while the shower is on when I am back at home.
     

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