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Boiler swap - swap to combi or keep conventional?

Discussion in 'Plumbing and Central Heating' started by SDBradfo, 29 Dec 2020.

  1. SDBradfo

    SDBradfo

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    Hi al

    so my boiler is on its last legs and am weighing up our options.

    I live in a very small one bed house with 1 shower (plumbed in), no bath, 2 rads, and one towel rail.

    At the moment we have a very old Ideal Classic system boiler with a 90ltr unvented tank. The CH tank in the loft has a decent amount of sludge in it though it isn’t affecting the rads as all get hot at the bottom. All pipe work is from the original instal of the boiler in the 90s. The boiler is currently in the kitchen with a horizontal flue and less than two metres from the gas metre.

    I know the cheapest thing would be to swap to a system boiler but I am not sure whether we would be silly not having the tank replaced as well? It’s not leaking and retain water heat quite well, and the immersion still works on it. If I were to replace the tank it looks as if it’s be cheaper to swap to a combi (if Boxt is a reliable way to look at a guide price).

    Just for costs sake we’d keep the boiler on the same place anyway and I do like the ideal of getting a new compact system boiler just to save on space.

    Basically I’m wondering whether if we kept a system boiled, would we be silly not to replace the cylinder too?
     
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  3. Madrab

    Madrab

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    If everything is working well, the system is clean and your happy with the way everything works at the moment then no point in changing the fundamentals. If you have a small tank in the loft then chances are it won't be a system boiler, more a regular (heat only) boiler , does the system have a separate pump, say up where the hot water cylinder is?

    If it's just the sludge in the F&E tank then that can be easily cleaned out.
     
  4. SDBradfo

    SDBradfo

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    Yes sorry it is heat only, my terminology is not the best!

    thanks for the reply.

    yes there is a circulating pump but I left that out as I assumed a new heat only boiler would have a pump built in these days, again I think the pump is as old as everything else.

    would you trust the existing cylinder if it works fine then? My only concern is that I replace the boiler and then end up replacing the cylinder which means overall I have paid more than what a combi swap would cost.
     
  5. ianmcd

    ianmcd

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    A system boiler has a pump built in and an expansion vessel,a heat only boiler does not, your existing boiler is a heat only boiler, your incoming cold water flow rate will decide whether a combi is suitable
     
  6. SDBradfo

    SDBradfo

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    Ahh ok I’ll need to do some more research then.

    mains pressure is very good, even at peak times.
     
  7. ianmcd

    ianmcd

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    Should fine if you want a combi then and you can remove the HW cyl and both tanks in the loft
     
  8. Madrab

    Madrab

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    Nothing wrong with a combi but a combi will never replace the unvented cylinder's HW delivery albeit it is only 90L. Cold mains dependent, your unvented will deliver hot water at the rate that the mains can supply it, a combi will never be able to deliver the same, unless the cold mains flow is low.
     
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  9. SDBradfo

    SDBradfo

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    I quite like the system we have and I understand some regular boilers can be quite small these days which appeals to me as our kitchen is small.
    My real concern is whether I am stupid for not replacing the cylinder at the same time given our old it is...if it’s advised that I replace that then I think I’d be stupid not go for a combi. Boxt (doubt I’d go with them but might do...) say an extra £600 for a a new 90ltr cylinder, this makes it more than their fixed price quote to swap to a combi.
     
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  11. ianmcd

    ianmcd

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    But they only have one shower, so a combi would work for them, my other half lives in a LA house it has an electric shower and a 210L unvented for hand and dishwashing, total over kill she would have been far better with a combi
     
  12. SDBradfo

    SDBradfo

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    Is there such a thing as overkill for a combi boiler? Sorry if it’s a stupid question!

    On the heating side we literally only have two rads and a towel rail
     
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  13. ianmcd

    ianmcd

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    yes you will need a boiler with a really good modulation ratio, not all boilers have the same ratio, if you put too big a boiler in it will constantly cycle, why not get a decent installer round to chat about your options, if the unvented is in good condition, a system or heat only would suit you , you would only require a small boiler, dont expect to get such great service from any new boiler that you got from your Ideal Classic, they are fantastic boilers
     
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  14. SDBradfo

    SDBradfo

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    Have one coming at the weekend but just wanted a second opinion as I know some installers have preferences to particular heating systems and brands.

    it’s a shame we can’t fix the Ideal by putting a new fan assembly in but we want to get the kitchen done and I know any new boiler will have the flue in a different place, and require a condensate pipe, so don’t want to get tile work done only to change it when we eventually get a new boiler.
     
  15. ianmcd

    ianmcd

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    Which I deal Classic do you have nearly all replacement fans are still available, I done one last week
     
  16. SDBradfo

    SDBradfo

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    It’s an NF30 but more concerned about the alterations we’d need to do for a new boiler (gas pipe, condensate pipe, etc) that we’d may have to change after getting a new kitchen
     
  17. ianmcd

    ianmcd

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