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Swapping out a DHW heat exchanger

Discussion in 'Plumbing and Central Heating' started by Stringman_uk, 29 Jan 2021.

  1. Stringman_uk

    Stringman_uk

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    Hi all,
    Boiler is a Glow worm Ultracom 30cxi
    Our shower is starting to run hot and cold , We had this before ( about 4 years ago) and it was the DHW heat exchanger, this was replaced and all was good.

    So the plumber has said he can replace the heat exchanger for £250.
    As I can buy a replacement HE for £50 it seems a lot for the labour ( reading about it , it seems to be about an hours work)
    From what I can see its a matter of isolating the boiler water supply and mains, draining the boiler and then swapping the unit out.

    Is this correct? and if it is what is the best way to drain the boiler ?(There seems to be a view of not to use the PRV for draining.
    Many thanks in advance
     
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  3. sxturbo

    sxturbo

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    No one will answer this as you are allowed to work on the internals of the boiler unless you are gas Safe registered,
     
  4. ianmcd

    ianmcd

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    You wont get that heat exchanger for £50 they are a lot more expensive than that unless you are looking at dodgy ones on ebay
     
  5. Stringman_uk

    Stringman_uk

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    Thanks for the replies.
    I thought that as it was a water only job I was allowed to work on it (maybe thats old information now)
    To be fair the £50 was on ebay but I have seen them for under £100- so even £150 to fit seems a lot of money for fitting that or am being unrealistic
     
  6. endecotp

    endecotp

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    You may be able to remove and flush the existing heat exchanger, rather than replacing it.

    You are allowed to do this yourself on some boilers, but on others I believe any opening of the boiler casing exposes sealed parts and so is not allowed. I don’t know what your boiler is like.
     
  7. Stringman_uk

    Stringman_uk

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    Thanks for that reply.
    My boiler is a glow worm Ultracom 30 cxi this is what it looks like inside if that helps[​IMG]
     
  8. BoilerBob

    BoilerBob

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    Well there you are if that’s a room sealed job you’ve just left yourself open to
    prosecution and a big fine or even prison god almighty. Bob
     
  9. ianmcd

    ianmcd

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    Just ignore the doom and gloom brigade, you have not interrupted the combustion cover and nothing to stop you changing it yourself if you want, you should just clean it though and it will work, brick acid or one shot from screwfix will clean it, but be carefull when using , it is nasty stuff, follow all the safety guidelines
     
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  11. Stringman_uk

    Stringman_uk

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    Boiler bob, please explain. What do you mean by room sealed job?

    I think you are wasted as a plumber and really should be on the stage ;)

    And before you going off on one saying something like bloomin diyer not listening to our advice etc etc (as I see so many times on her- albeit often totally justified) I was asking for advice before I considered my options.
    Due to the pandemic, no Government support for me and the fact that I havent earnt any money from my job in 11months, blah blah blah, money is somewhat tight. So if I can legally and safely do the job myself I ought to do that.

    Now given that I have read that the job only takes about an hour and you can buy a HE from a reputable supplier (point taken ianmcd!) for £100 So £150 an hour seems to be rather a high , but again if I am being naïve on the time it takes or the hourly rate it would be good to be told that.
    Thanks
     
    Last edited: 31 Jan 2021
  12. Stringman_uk

    Stringman_uk

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    Thank you ianmcd. This is what i was hoping to do.
    I still havent decided whether to do it myself or pay someone to do it. It does seem an easy (if fiddly) job to do.
    I do actually have some brick cleaner in the shed, but wondered if it was worth buying the ebay one ( pretty sure thats what we got last time and its lasted 4 years) then i can clean the old one and have a spare.
    What I was really hoping for is confirmation that you just need to isolate the mains water supply to the boiler (ie do you just isolate at the feed to the boiler or do you need to turn off the mains water supply?) turn off the mains power and then just drain the boiler before you swap it out?

    Thanks in advance
     
  13. ianmcd

    ianmcd

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    you need to turn off the mains inlet below the boiler and open the lowest hot tap, drain the boiler, cover all the electrics, isolate the electrics then good to go, even doing all this , you will still get some water coming out , that is normal, one of the easier plates to change
     
  14. endecotp

    endecotp

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    The main things to worry about are water spraying over the electrics because you've failed to isolate or drain correctly, and losing vital screws down the back of the kitchen units, under the floor etc. Strategically-placed towels, even cling-film, can help.

    What sort of blockage do you think there might be? If I were you I'd try just flushing with mains-pressure water from a hose pipe first. If you're in a hard-water area and think it could be limescale in the "output" side, acid could help. If it's due to rust or similar from the CH circulation water blocking the "input" side, I would say that acid is not the right chemical. But I'm not an expert by any means...
     
  15. ianmcd

    ianmcd

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    Why do you think I advised to open the lowest hot tap ?

    It is only held in by two screws or 4 screws depending on the unit
     
    Last edited: 31 Jan 2021
  16. Stringman_uk

    Stringman_uk

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    Guys

    Thanks so much for that.
    We do have very hard water so limescale could well be one of the problems. we did have a powerflush done when we swapped out he old one- huge amounts of sludge. I am also getting lots of particles collected by the magnet thing.
    I guess that trying to clean/flush it cant do any harm.
    Is it advisable to fit new washers when refitting if so are they a standard size- it would be better to get them prior to removal?
    Thanks
     
  17. oilhead

    oilhead

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    Yes, A selection pack of washers, 1/2 and 3/4 should suffice.
     
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