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New Navien combi boiler installed with old Santon Premier problems.

Discussion in 'Plumbing and Central Heating' started by JohnHuson, 8 Oct 2021.

  1. JohnHuson

    JohnHuson

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    I enjoy a pint at my local pub/restaurant owned by a hardworking Chinese family. I have had many years experience on property maintenance and they asked for my help.
    He had an old LPG gas boiler feeding a Santon Premier unvented cylinder feeding 23 radiators and hot water for the kitchen. New boiler is a Navien combi and the pipework is a work of art!
    The installers came out again and said boiler works as it should so problems is not of their making.
    The upstairs living accommodation has a separate combi system.
    When the fitters arrived he was given an option to retain the unvented cylinder, so he did.

    The central heating no longer circulates around the building and about six radiators get warm.
    I have bled and done everything to get it going but no improvement. It worked fine before the boiler change. The system was not drained. It was flushed four years ago. All TG's are working fine.
    I notice that the original central heating Granfoss pump sucks the flow downwards to the cold feed of the cylinder at the bottom as a secondary feed. I found that the water temperature between 2 feet from the pump to the cylinder went from warm to cool indicating lack of flow?
    I cracked open the drain cock and the temp from the pump to the cold supply into the cylinder is now even.
    The expansion vessel is at 3 pressure whatsits.
    The pump is overheating which suggests sod all is happening and there is an obstruction to flow?
    I changed the pump to a nearly new pump which is trying to perform as it should.
    The problem is either; the installation of the new combi boiler? The routing of pipework not being correct? Or me not seeing the obvious?
    Your help appreciated please. They are really nice people and I might get a couple of freebie beers.
     
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  3. JohnHuson

    JohnHuson

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    The electrical supply to what I think is the central heating pump has been labelled 'secondary pump supply'.
     
  4. flameport

    flameport

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    Without a lot more information, this:
    would seem to be the problem, as it worked before the new boiler was installed and now it doesn't.

    Why was a combi boiler installed?
    What colour was the pump connected to the 'secondary pump supply'?
    Photos of the installation?
     
  5. JohnHuson

    JohnHuson

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    I replaced the normal type gold pump with a more powerful 110 green model which draws water downwards which then
    joins the cold inlet at the bottom of the tank. I will take photo's this evening and send in the morning.
    The original boiler was just knackered but system worked fine. It was an old Concord LPG floor standing.
    The installer offered to remove the cylinder but gave the customer a choice which in hindsight was the wrong decision.
    Now he has to run the boiler for 2 hours to get enough domestic water to use. Rather eliminates the reasoning for a
    combi don't you think?
    Thanks for helping.
     
  6. JohnHuson

    JohnHuson

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    No comment folks?
     
  7. muggles

    muggles

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    You've not provided the requested photos and no amount of trying to describe what you've done is going to help I'm afraid. You also seem to be somewhat confused as you say they have problems with the radiators not heating up, but you've replaced the secondary circulator which has nothing to do with the radiators. I hope you've replaced it with another secondary circulator type and not a standard central heating circulator, which will contaminate the hot water.

    Post photos and we may able to help further. Need photos of the boiler & pipework coming off it, photos of the cylinder and the pipework around that, and anything else that could be relevant
     
  8. cross thread

    cross thread

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    As muggles said it sounds like you are messing with the water secondary return pump, nothing to do with the heating
     
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  10. JohnHuson

    JohnHuson

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    Thanks for your patience. I am going up to the building again this morning if any more photo's are required. It has suddenly occurred to me that although the boiler is new perhaps the fault is with the circulation pump in the boiler?
    That could account for the first five rads in the circuit getting hot and then the rest gradually remaining cold? IMG_20211009_190711.jpg IMG_20211009_190714.jpg IMG_20211009_190826.jpg IMG_20211009_190832.jpg
     
  11. JohnHuson

    JohnHuson

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    I have no idea what the function of the white cylinder is? The Schrader valve will not accept
    a tyre gauge to check the pressure if it is meant to be an expansion vessel.
    The secondary pump is a 15/60 but I will replace it with the original pump today, which I have
    tested and found to be working OK.
    Thanks for your help.
     
  12. muggles

    muggles

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    The Wilo Gold in the photo is nothing to do with the circulation of the heating system, it's there to circulate hot water around the taps. It's not the correct circulator for the job though - it needs to be one with a bronze or stainless steel body such as the one lying on the floor below it. Can't help with the heating system from these photos, as the only heating system component visible is the expansion vessel which doesn't tell us very much
     
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  13. muggles

    muggles

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    The white cylinder is an expansion vessel for the hot water system. The hot water system should only be worked on by people with a G3 unvented cylinder qualification.
     
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  14. JohnHuson

    JohnHuson

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    Thanks, I will not attempt to make any changes
     
  15. Gasguru

    Gasguru

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    The fact that the boiler was replaced without draining the system, the poor choice of Navien (limited backup and spares) for a pub boiler that needs to be fixed asap and the idea of a combi driving 20+ rads tells me the installers were clueless. In the gas trade pubs are at the bottom of the list as potential customers...they're notorious for rough installs and landlords wanting a cheap job.
     
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