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System or heat only boiler

Discussion in 'Plumbing and Central Heating' started by waveuk, 15 Jun 2014.

  1. waveuk

    waveuk

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    I have a quite old (about 20 years) boiler that needs replacement. I had a few quotes with similar specs and prices. All of them were with a system boiler and a megaflo.

    My house is about 30 years old with good build quality. 15 years ago a big conservatory was build with underfloor heating. I have moved here 2 years ago so I do not know all the details but have not have any issue with the house so far.

    I have decided by one of the quotes and now the company is telling me about a remote risk os leaking in the underfloor heating as pressure is higher with the system boiler. For avoiding this the option is to have a heat only boiler with an external expansion vessel.

    Not completely happy they are telling me this now. Also the system boiler was a Valiant and the Heat only is a Worcester. The work is supposed to be done in 2 weeks and I am not very sure what to do.

    I would appreciate any advice.
     
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  3. St0rmer66

    St0rmer66

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    Rubbish, absolutely no difference. It's a sealed system either way. Or are you saying that the underfloor heating is open vented as it is? (unusual).

    However, you may still need an external expansion vessel anyway as the one built into the boiler may not be big enough. But that is an entirely different issue to "heat only vs system boiler".
     
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  4. waveuk

    waveuk

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    Many thanks!

    What they say is that with the heat only pressure can be 0.5 bar but with the system it will be 1.5 and if it drops below 1 it switches off.
     
  5. St0rmer66

    St0rmer66

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    It sounds like the underfloor heating is open vented then? Do you have an expansion vessel and filling loop anywhere at the moment? Perhaps they're suggesting leaving the system open vented. I can see the logic in that if the pipework is old... But then it might be fine sealed anyway.
     
  6. I can see what they are saying about running it at a lower pressure.

    Some points
    I have only ever had one system leak after sealing it

    I would personally avoid the Worcester

    I fit boilers that don't have a low water pressure switch and use a different method to ensure there is water in the boiler. Allowing me to choose the pressure it runs at ;)
     
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  7. waveuk

    waveuk

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    Yes currently the system is open vented. No expansion vessel. The idea is to have it unvented.

    Underfloor heating is about 10/15 years old so I do not know if this can be considered really old.

    I read cement can corrode the pipes but I have checked now and all pipes enter in the floor within a plastic pipe. Not sure is this protection is maintained in all the circuit.
     
  8. St0rmer66

    St0rmer66

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    Cement will corrode copper pipes, not plastic, so don't worry about that.

    If there is no cost implication then it might make sense to keep it open vented (and I can't see why there would be) but it "should" be okay sealed. You can still have unvented hot water (megaflo or similar) with an open vented system (they are 2 separate things) if that's what you were worried about.
     
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  9. Gasguru

    Gasguru

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    Why, what's wrong with a CDi Classic?
     
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  11. waveuk

    waveuk

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    What's your view about Valliant? I wante to fit a weather compensator and I am not very keen on Worcester one.
     
  12. This sounds like a job for.............












    INTERGAS!
     
  13. Dan Robinson

    Dan Robinson

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    An Intergas will do everything for less fuss than a Vaillant.
     
  14. Dan Robinson

    Dan Robinson

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  15. waveuk

    waveuk

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    The price is the boiler is less than a third of the quote so saving a bit on the boiler won't make a huge difference. To be fair I prefer a longer warranty.
     
  16. Dan Robinson

    Dan Robinson

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    2 years extra (at best)? And how do you think the warranty is paid for?

    And how tested do you think these long warranties are?

    And what are you chances of meeting the requirements of the warranty after 5 or 6 years?


    The Intergas has a 5 + 10 year warranty.... with less things to go wrong and a more robust construction.
     
  17. waveuk

    waveuk

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    I think these questions also aply for Intergas. Anyway as said I think a bit pointless to try to save a few pounds on the boiler when that is not the biguest costs.

    I will go with Valliant or Worcester. On heat only boilers which one would you recommend.
     
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