Combi boilers

Discussion in 'Diamond Lil's' started by Stevie Dore, Aug 26, 2016.

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  1. Hi All,

    I'm after a bit of advise from people who possibly know...... and even from those that don't ;). We are having a new extension built and need to move a 30+ year old standard boiler. Therefore we have decided to remove the old boiler and install a condensing combi in the new location. We have had four quotes, all roughly the same price but with different size and brand recommendations, hence this post.

    Quote one, 32kw Worcester Bosch CDi
    Quote two, 34kw Worcester Bosch CDi classic
    Quote three, 28kw Vaillant Eco Tec Pro
    Quote four, 36kw Worcester Bosch CDi

    What I don't understand is why the difference in capacity? It's only two or three l/minute hot water delivery difference between all of them. According to the latest guy, we get 18 l/minute mains water. All quotes were from apparently ex boiler engineers.

    Any advice appreciated.
  2. I'm not a gas boiler engineer, but look at it this way. If you have a constant heat source and pass water across it at say 1ltr a minute, then the water will get scorchio. If you pass the water over it at 15ltr a minute, then the water will not have the time to be fully heated, by a 15th factor.

    I'd be going for the 36kW option. But there are other factors to consider.
  3. witsend

    witsend War Hero Book Reviewer

    Hi Stevie,

    Just had a new one fitted this week in a 3 storey house I'm refurbishing. Pervious one was a Sime 80E or something.

    I'm not sure what the model now fitted is, but it's a Vokera condensing boiler. 5 years warranty once I register it online after I finish this post. I believe Vokera are cheaper than Worcester and you get a 7 year warranty with a Worcester. Also had 7 radiators and their valves replaced. Towel rail for the bathroom. All the pipework was fit for purpose apart from the main gas supply pipe from the gas meter. This was replaced as well. If they replace this make sure they ground the pipe back to the main board with a 10mm earth cable as per regs.

    Team of three took 1 day to finish it.

    The living room gas fire was also removed and I'm not going to refit another for a couple of reasons. One, I can't remember the last time I switched on a living room gas fire. Two, the cost and hassle to upgrade the flume and chimney.

    All in it was a £2700 cash in hand. I didn't even bother phoning British Gas for a good laugh. You can probably double or triple that price with them.

    Check out the reviews online for the companies and go with the who you feel comfortable with. When it comes to this stuff you have to trust the expert and your instinct.

    This was an easy job for them because the house is empty and basically a construction site. There wasn't any problems with lifting floorboards etc, because its just bare walls and floorboards.

    I have left the instruction/parts manuals at the boiler so I'm unable to tell you what litres per minute are for my system. I'll maybe be down over the weekend and dig the info out and take some phots.
  4. Thanks for the replies guys. I've had quotes from 4 reputable companies, one local, two national and one energy provider. I realise salesman and commission etc, etc, but what I don't get is the difference in recommended sizes. From a 28 kw to 36 kw is a bit of a jump.
  5. witsend

    witsend War Hero Book Reviewer

    You'll need to get a degree in thermodynamics to fully understand the system Stevie.

    Just ask them how many radiators you can fit onto the boiler.
  6. Thanks for the replies and the link. I'll have a read, see if I can get my head round it.
  7. I have the vaillant 28 eco pro, had it w few years now, been a good combi, I have it serviced annually. It does my water and 6 rads. I have been told that the vaillant is a very good boiler, some plumbers say better than the Worcester?
    Ask each quote giver how they came to select they given boiler, I even had a plumber in the past select a boiler because it was his favourite one to fit? When he could not fit in the gap the one he fitted was cheaper?
  8. Go for the biggest, expect it to last about 10 years, ensure drain pipe is well insulated where it leaves the house,lots of callouts for frozen drains(kettle of hot water usually cures it) worcester are good ,7 year warranty.
  9. Trainer

    Trainer War Hero Book Reviewer

    If you look up flow rates, it can help explain the power sizes - they quote them as, for example 9l/min of hot water. I'm in the same situation - about to spend about 3 grand - I'll be getting a Vaillant. I did have British Gas round a while ago for comedy capers. the advantage of being close to Pompey is that a lot of the fitters are ex Tiffs and come well recommended :D
  10. witsend

    witsend War Hero Book Reviewer

    Only found out this week that there is a drain line and valve for the system. In my defence it's the other side of the external gas meter and hidden by the hedge. I might have seen it if I chopped the hedge with any interest and saved a bit of mess removing the radiators.

  11. Thanks for the replies. Probably gonna go with SSE and the 28kw Vaillant. Trainer, didn't you forget to type a spit after you typed the word Tiff? hooooock Phuut!....Incoming! ;)
  12. If you go for the largest you can always add on extra rads and you will probably make the house warmer quicker, gas consumption more but for shorter periods
  13. What he said ^.
    18 l/Min allows you up to a 42kw cdi. Yes, a bigger boiler may cost more, but you may regret not having that spare capacity in the future.
    I assume, the calculations are based on using your old system, with the extension add on. These are assumptions, not proven values.

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