New Boiler Advice

Discussion in 'Plumbers' Talk' started by Jason Hodgkinson, Dec 18, 2017.

  1. Jason Hodgkinson

    Jason Hodgkinson New Member

    Hi - My old boiler is probably running on borrowed time so I'd like some advice on which type to go for.

    At present we have 4 bedrooms, 1 main bathroom, 2 en-suite shower rooms, 1 cloakroom and 17no radiators.

    The existing boiler is a Powermax 185 which as far as I can see is a traditional boiler with a built in cylinder.
    The boiler is gas fed on and on the top floor of a 3-storey house in an airing cupboard (centrally based, not on an outside wall but the loft space is directly overhead)
    The current system has an F/E tank in the loft directly above.

    The current boiler runs out of hot water fairly quickly when showering, although it reheats quickly, so we'd like something that can cope a little better.

    A couple of people have suggested a combi but from what I'm reading I might be better with a standard heat only with a separate hot water cylinder.

    Any advice would be very helpful and thanks.
     
  2. Wayners

    Wayners Well-Known Member

    Combi. Why would you not get a combi. Get rid of all them tanks with the space. Weight and possible leaks
     
  3. KIAB

    KIAB Well-Known Member

    A large combi (prefered choice) will give you flow, all depends on your mains water pressure though.
    Seen a few houses where they have fitted two smaller combi for same set up as yours.
    Could look at a system boiler with a unvented cylinder,say around 250-300ltrs,allowing 50ltrs per person & 50ltrs spare.
     
  4. Jason Hodgkinson

    Jason Hodgkinson New Member

    Hi Wayners - thanks for the reply - the only reason is the comment I've read a lot that says 'combi would not cope and standard type systems are better for multiple bathrooms'.

    I assume you think a good sized combi would be good here then?
     
  5. Jason Hodgkinson

    Jason Hodgkinson New Member

    Hi Kiab - thanks for the reply. The mains pressure seems ok but how can I know/check for sure?
     
  6. KIAB

    KIAB Well-Known Member

    There is a simple way to accurately measure your water pressure:

    1. Get a water jug (preferably 1 or 2 litres in size)
    2. Get a stopwatch (usually found on most mobile phones)
    3. Place your jug under a tap and turn it on
    4. Time 6 seconds on your stopwatch & turn your tap off.
    5. If you're a whizz at maths, you can do the next bit in your head (or simply use a calculator - found on most mobile phones). Take the amount of water in the jug in litres (e.g. 0.8 litres) and multiply this by 10. This will give you your flow rate in litres per minute (e.g. 0.8 litres x 10 = 8 litres per minute).
    6. If your flow rate is less than 10 litres per minute, you have what is considered low water pressure. Anywhere between 10 - 15 litres per minute is acceptable, but can be improved. A flow above 15 litres per minute is considered good.
     
  7. Wayners

    Wayners Well-Known Member

    Yeah. Big combi. Tanks are a pain and if you get heating leak then it's limited water damage with combi because it's a sealed system opposed to flooding the place continuously.. That swings it for me having seen water coming out a front door
     
    KIAB likes this.
  8. Jason Hodgkinson

    Jason Hodgkinson New Member

    9lts/min then so I am just under the good pressure limit :(
     
  9. KIAB

    KIAB Well-Known Member

    Stopcock fully on, what is supply pipe into house,plastic lead, etc.
     
  10. Jason Hodgkinson

    Jason Hodgkinson New Member

    Thanks- to be fair we rarely use more than one shower at the same time, just normally wait until someone has finished. I guess this would help too.
     
  11. Jason Hodgkinson

    Jason Hodgkinson New Member

    Plastic, stop cock is the new plastic one with the 90deg lever - it's fully on.

    I've done it a couple of time more and seems to get about 10lts /min. Slight improvement.
     
  12. KIAB

    KIAB Well-Known Member

    Well, that good,usually when you have flow issues you find it's a old grotty stopcock sometimes causing the problem or supply pipe is lead, or stopcock outside turned down.
     
    Last edited: Dec 18, 2017
  13. Jason Hodgkinson

    Jason Hodgkinson New Member

    When you guys recommend a 'big' combi are you talking 32-40kw?
     
  14. KIAB

    KIAB Well-Known Member

    Yes.
     
  15. dobbie

    dobbie Well-Known Member

    Have a look at Worcester Greenstar CDI Highflow,they are rated for larger premises.
     
  16. Jason, the only thing really wrong with your old system was the small size of the built-in storage tank, I'm guessing? So, if you want the best possible guaranteed performance, your new setup would be a system boiler (ie sealed - no tanks in the loft) and a larger unvented cylinder (basically a bigger version of what you had).

    This should work - it should deliver oodles of water just like the old system but deliver hot for longer 'cos it's bigger.

    (Mind you, it will be somewhat restricted in performance if your incoming mains is only 9 or 10lpm. In theory all you can get out is what you put in, so that's just 9lpm shared by all the taps.

    You really also need to check the incoming pressure as that has an equally important bearing on the flow - a decent pressure (eg 3 bar and upwards) should deliver that 9lpm constantly with little drop even if two taps are open. A poor pressure - say 2 bar or under - will see that flow drop away alarmingly once a second tap is opened.

    I'm quite a fan of combis, even tho' they do obviously have some shortcomings. However, I would NOT recommend on in your case due to the poor flow. And no point at all fitting a 'big' one - which can deliver, ooh, 13lpm and upwards - when all you have coming in is 9lpm. With only 9lpm coming in, the combi's output will almost certainly be less even than that, and that's truly pants.

    You can now get mains booster pumps, but I understand they are restricted to the min regulation flow, which is 9lpm. (But worth confirming).
     
  17. Jason Hodgkinson

    Jason Hodgkinson New Member

    My house was built in 2001 so it is fairly modern. I'll look at the combi ranges then. thanks ever so for your advice.

    Would you have any specific manufacturer that you would recommend or stay clear of. Baxi, Worcester, Valliant and Ideal seem to be fairly well represented.
     
  18. KIAB

    KIAB Well-Known Member

  19. Jason Hodgkinson

    Jason Hodgkinson New Member

    Thanks - some good stuff to consider there. I've just checked the pressure and having two taps running at once doesn't really affect the pressure, so I'm assuming that is good news too. I might try to check the flow on my outside tap as it is more of a traditional tap rather than the mixer taps in my bathroom and kitchen.

    :)
     
  20. Jason Hodgkinson

    Jason Hodgkinson New Member

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