1. Visiting from the US? Why not try DIYnot.US instead? Click here to continue to DIYnot.US.
    Dismiss Notice

Valiant 937 ecotec Combi boiler

Discussion in 'Plumbing and Central Heating' started by rizsher, 31 Dec 2009.

  1. rizsher

    rizsher

    Joined:
    3 May 2009
    Messages:
    75
    Thanks Received:
    0
    Location:
    Aberdeen
    Country:
    United Kingdom
    About to give the go-ahead on this one to replace my slightly dated conventional boiler and vented hot water tank.

    Would appreciate the experts' view, is it a good enough boiler to go for?.

    Thanks.

    Riz
     
  2. kevindgas

    kevindgas

    Joined:
    28 Mar 2006
    Messages:
    5,743
    Thanks Received:
    478
    Location:
    Hedge End Hants
    Country:
    United Kingdom
    how big is your house? i never spec the 937 as most people don't want a washing machine sized appliance hanging from their wall.

    would the 837 not be big enough. 15.2 litres a minute at 35k rise (12.6 litres at 42k rise) i have installed several and never had any problems with the hot water delivery.
     
  3. rizsher

    rizsher

    Joined:
    3 May 2009
    Messages:
    75
    Thanks Received:
    0
    Location:
    Aberdeen
    Country:
    United Kingdom
    Its a 4 bedroom detached with a fairly big living room (I think 3 x 9 meters) with one of the walls with just double glazed panels opening to the extension, and an extension which has 2 windows w/o double glazing.

    I have quotations for a Veissmann 35 kW combi, or this Vaillaint with integrated hot water cylinder, the former is about 400 quid cheaper, but being from a hot country, the idea of having atleast some stored hot water seems appealing to me, considering the cost differential isn't bank-breaking.

    Thanks.
    Riz
     
  4. D_Hailsham

    D_Hailsham

    Joined:
    18 Oct 2007
    Messages:
    10,385
    Thanks Received:
    1,300
    Location:
    Kent
    Country:
    United Kingdom
    How many baths/showers could be running at the same time?
    What is the mains cold water flow rate?
    What is the mains cold water pressure (static and dynamic)

    There is a danger that the 937 will be too large for your heating requirement, so you should work this out by using one of these calculators:

    Sedbuk Boiler Calculator

    EST online boiler calculator

    Do you know the total output of your radiators? If not, use Stelrad Elite Catalogue to find the approximate answer.

    Please post the information.
     
  5. Agile

    Agile

    Joined:
    26 Jun 2004
    Messages:
    63,560
    Thanks Received:
    4,511
    Location:
    London
    Country:
    United Kingdom
    "How big is your house" in relation to boiler sizing means to a heating engineer how many baths/showers do you have and how many do you want to be able to run together!

    A stored HW system is always better if there are more than two people living there!

    You also need to measure your dynamic mains water flow rate.

    Whatever hot place you think you come from its not of any significance in relation to hot water usage. The only slight difference is that having baths instead of showers is a rather British ( English ) fashion. ( I have to say that carefully because I remember a student time friend who was an asian from east africa and was VERY British! He paid a lot to be a member of the St James Club in Mairfair )

    Tony
     
  6. rizsher

    rizsher

    Joined:
    3 May 2009
    Messages:
    75
    Thanks Received:
    0
    Location:
    Aberdeen
    Country:
    United Kingdom
    Agile,

    I've had so much conflicting advice from the various plumbers/heating engineers who have visited the house over the last 2-3 weeks that I'm beyond confused now.

    I first got 3 plumbers, unanimous advice was the existing 24kW boiler is too small for the 13 radiators+extension+hot water cylinder. Quoted me for b/w 30 and 34 kW boilers of various types (condensing conventional with vented h/w cylinder, sytem, combi).

    The circa 30-34 kW number matched with the various online tools I had used to work out the optimum size of the boiler.

    However, to confirm everyone, I called British Gas and arranged an appointment with one of their heating engineers. The guy who came in said I need not more then 20.4 kW, and hence the existing boiler is big enough, therefore he will not be able to even quote me for a replacement!!!.

    Confused further, I got HydroElectric to come and do the same, and the chap who came in shat all over my existing boiler and quoted me a small fortune to replace it with a WorcesterBosch 30kW combi boiler.


    The EcoTec 937 gives an output of 37kW DHW and 28kW CH, which seems to sit right around my house's CH requirements. I believe (correct me if I'm wrong" the 37kW DHW just means h/w will arrive quicker at taps?...

    I'll ask the plumbing company to confirm the mains water flowrate/pressure before giving the go ahead for the installation.

    Thanks.
    Riz
     
  7. Agile

    Agile

    Joined:
    26 Jun 2004
    Messages:
    63,560
    Thanks Received:
    4,511
    Location:
    London
    Country:
    United Kingdom
    No one should ever quote for any combi unless the mains dynamic flow rate has been measured.

    Your heating requirement is likely to be about 15 kw to which should be added 2 kW for hot water cylinder heating.

    So the BG guy is probably the only one to corretly state that 24 kW is adequate for a cylinder system.

    I dont see how you could have calculated that you need 30 kW plus!

    The 937 only gives an enhanced flow rate until the store is depleted. Few will tell you that!

    The reality is that there is a poor level of training/understanding in this industry.

    Tony
     
  8. rizsher

    rizsher

    Joined:
    3 May 2009
    Messages:
    75
    Thanks Received:
    0
    Location:
    Aberdeen
    Country:
    United Kingdom
    Thanks Agile.

    I've just emailed the installer and asked him about the mains pressure and flowrate. Hopefully he'll get back to me next week.

    Please see the attached calc sheet. It gives an output of 30.3 kW, and I've not yet added the extensions which is sort of our usual hang-out area.

    Its a house made in the 60 with terrible insulation, I've already paid for the B&Q 198 pound loft insulation deal, they'll get back to me soemtime next week, but, the house apparently also cannot take cavity wall insulation.

    The existing boiler I have takes an hour and a half to heat the house, and that is when I've almost turned off the radiators in 3 of the 4 bedrooms. The living room has 60s vintage skirting heating fin type things which barely get luke warm. Replace these with a couple of radiators and I'm guessing the 1.5 hour it takes to warm up will shoot up significantly.

    I'm attaching the calculatiom from the website D_Halisham recommended, the answer matches what I was getting before.

    [​IMG]

    What happens on the 937 one the tank depletes?. To be frank, if the advantage of the 937 isn't all that great, I would rather I stuck with a normal combi as that would save the cost of the re-modelling of the storage area.
     
  9. Agile

    Agile

    Joined:
    26 Jun 2004
    Messages:
    63,560
    Thanks Received:
    4,511
    Location:
    London
    Country:
    United Kingdom
    You have calcaluted that on the basis of no loft insulation. Correcting that will reduce the heat requirement by up to 25%.

    That could reduce the heat requirent to 21 kW plus 2 kW for water and that gives 23 kW thus validating a 24 kW boiler. Its still a high heat loss though and anything you can do to reduce this would save a lot of gas! Why is cavity insulation not possible?

    The 937 is ideal for filling baths quickly. When the store is depleted it just runs at its basic heat input and gives about 15 li/min compared with over 20 li/min initially. Dont expect two long simultaneous showers though. It will run one outlet very well and usually provide limited flow in the kitchen as well.

    Can you measure the power input to your existing boiler at the gas meter ( see FAQ ) as well as the flow and return temperatures? There may be some problem there.

    Tony
     
  10. kevindgas

    kevindgas

    Joined:
    28 Mar 2006
    Messages:
    5,743
    Thanks Received:
    478
    Location:
    Hedge End Hants
    Country:
    United Kingdom
    absolute tosh !
    the 837 and the 937 will happily run both simultainiously even the 831 will just about cope with the shower/tap used at the same time.

    OP the 837 would be man enough to do the job, in my opinion with warm start active i doubt you will notice much of a difference between the 837 and 937.

    as for radiators allow 1.5Kw per rad and you won't be far off
     
  11. kevindgas

    kevindgas

    Joined:
    28 Mar 2006
    Messages:
    5,743
    Thanks Received:
    478
    Location:
    Hedge End Hants
    Country:
    United Kingdom
    tony the OP asked about a combi so how is this relevant? nothing would validate a 24 Kw combi they are crap at the best of times.
     
  12. Tipper

    Tipper

    Joined:
    1 Dec 2008
    Messages:
    1,144
    Thanks Received:
    103
    Location:
    Devon
    Country:
    United Kingdom
    One advantage not often advised of the 937 store is that it produces hot water as soon as you open a tap plus the time to get to the tap of course. Non-store combis take time to warm up prior to the heated water starting to flow. The store ensures HW is available immediately.

    I've got one and think it is very good. Compared to a similar sized conventional combi it's the bees knees.

    More expensive yes, takes up more space true (mine's in my garage where it's not an issue) but no need for expensive HW storage tanks etc., and more space in your loft and spare cupboard space on the landing!

    Modern combis, the 937 included, modulate the CH heat input to match the CH demand so the rated output is irrelevant assuming it's above about 20kW. Given the right controls no need to range rate the boiler either as the control system does it.
     
  13. kevindgas

    kevindgas

    Joined:
    28 Mar 2006
    Messages:
    5,743
    Thanks Received:
    478
    Location:
    Hedge End Hants
    Country:
    United Kingdom
    this is available from the 831 and 837 as well although in a smaller amount that is what warm start does.
     
  14. rizsher

    rizsher

    Joined:
    3 May 2009
    Messages:
    75
    Thanks Received:
    0
    Location:
    Aberdeen
    Country:
    United Kingdom
    To be honest, even with my current venred hotwater cyliner, I have to run the water for ~10-15 seconds before hot water starts appearing, I guess dead water doesn't take too long to become cold.

    Kevin: Is the warm start is a smaller version of the storage tank in the 937?.

    I currently have 2 options, either a Viessmann standard combi or the Vaillaint 937 with the h/w cylinder, the latter would add circa 700 pounds to the installation (cost of boiler differential + joiner + decorating to modify the storage area).

    If you think the 837 or a Veissman with similar storage would not be all that different in performance to the Vaillant 937 then I would much rather I went that way.

    THanks for all your assistance.
     
  15. D_Hailsham

    D_Hailsham

    Joined:
    18 Oct 2007
    Messages:
    10,385
    Thanks Received:
    1,300
    Location:
    Kent
    Country:
    United Kingdom
    Your calculations are correct.

    How thick will the B&Q insulation be? It should be a min of 250mm. On the continent they use 400mm.
    Why can't it take cavity insulation? Is it built of stone or something?

    We had skirting rads all round the house back in the 60s.
    Sounds as if the rads are not up to the job. Use the Stelrad Elite Catalogue to estimate their total output.
     
Loading...

Share This Page