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Discuss Combination Boilers Trash in the Central Heating Forum area at

  1. richard978

    richard978 Member

    Over the years I've seen the growth of combination boilers and how they have overtaken system and heat only.

    While combination boilers have their uses, its becoming increasing frustrating why so many plumbers choose this option.

    Heat only is by far the cheapest and effective way to heat a home and provide hot water. They are more reliable and will save the customer 1000s in energy and repair bills over the life of the boiler and cylinder.

    Increasingly I'm seeing more homes choosing 45 plus KW combination boilers to deal with hot water demand. But the plumbers fail to grasp that most homes will only have 13 litres a minute supply so what good is 20 litres a minute at the boiler.

    Also they fail to consider the gas service as most properties will not have a 35mm service. It states clearly in the regs that service should be considered. It won't be long before transporters start charging to upgrade when pressure problems are reported.

    A good quality heat only boiler and 170litre unvented cylinder is OK for most homes. In most cases 24kw will do.

    I really don't get it the concept of ripping out a system to fit an inferior water heater that will only last 10 years.
    • Agree Agree x 2
    • Like Like x 1
  2. scott_d

    scott_d Plumber GSR

    Space and money usually.
    • Like Like x 1
  3. townfanjon

    townfanjon Trusted Plumber GSR Top Contributor!!

    So Mr and Mrs Smith live in a 2 bed property and use an electric shower and have a dishwasher are you telling me they shouldnt have a combi ????
    Come on !!
    • Agree Agree x 2
    • Like Like x 1
  4. gmartine

    gmartine GSR

    I agree with the sentiment especially for larger homes, then again fitting a large combi boiler with an inadequate gas supply is verging on the fraudulent.
    Last edited: Feb 11, 2018
  5. snowhead

    snowhead Well-Known Member

    I also hate Combis, but occassionally there are circumstances where they'd work O.K.
    • Agree Agree x 1
  6. oz-plumber

    oz-plumber Plumber

    Combi's are quite rare over here.
    I only ever consider them in one bathroom homes and inform customers that only one hot tap can be used at any time.
    Also inform them that the heating will stop working when the hot water is being used.
    Some go for it, some don't.
    They do have their place, but it is a restricted place with user consideration required
  7. richard978

    richard978 Member

    I agree on space and money and also where this is very little hot water demand. But it seems to be the fault of the plumber, too many just offer combinations boilers as the best option which they are not.

    I've just serviced a Worcester Greenstar Highflow 55kw, put in 12 months ago and its getting just 15mb at the boiler with hotwater. 12mb in service mode. The internals are 22mm and should be 28mm but the problem is the service. It's inserted and therefore no where near enough for the boiler. The water supply was just 11lt per they will need a 35mm water service as well as GAS/

    As a result had to call gas transporter out who are now digging up the newly laid drive up because they can't mole it in.

    The is bordering incompetent and they should never been offered a combi.
    • Like Like x 1
  8. jonnyswamp

    jonnyswamp Plumber GSR

    There's still thousands of 2 bed, 1 bathroom properties around my way
    Not a lot of point shoving a 170l unvented in them
  9. scott_d

    scott_d Plumber GSR

    I think combis are suitable for most average households, providing people understand the limitations.

    Most people want them due to money and the fact everything is new when upgrading to a combi. its not a case of fitting a new heat only boiler to a system with a 5 year old pump, 10 year old controls and the original hot water cylinder
    • Useful Useful x 1
  10. Last Plumber

    Last Plumber Plumber GSR

    Personally, I take each and every case on its own merits.
    • Like Like x 1
    • Agree Agree x 1
  11. Lambed84

    Lambed84 GSR

    Personally, I agree.
    Combination boilers spot on for small households using electric showers. Any increase on demand like outlets or personal means a combi is simply inadequate in my eyes.
    So long as the customer has all the accurate and relevant information then our opinion here means nothing. Our job as a professional is to give advice on all options available and outline all benefits and draw backs.
    Just my humble opinion...
    • Agree Agree x 1
  12. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    But that could of been put down to a inexperienced gsr engy
  13. Ric2013

    Ric2013 Plumber Top Contributor!!

    I spend a lot of money and waste a lot of energy in the summer topping up the heat in my cylinder with my heat-only boiler running at extreme part load as it gets the cylinder up the last few degrees, although I often barely use any hot water some days.

    I agree that combis are naff, but I can also see the attraction of them.
  14. Stigster

    Stigster Plumber

    Unless its a 1 - 2 bed 1 bath situation, I'd always recommend a heat only boiler and a cylinder. Combis just have more complexity so more to go wrong, can take ages to fill a bath, can be awkward to work on (compared to heat only) so if you have room for a cylinder, put in a cylinder.

    I know there are differing opinions on it but that's how I feel about combis. I'm talking oil combis here because we only have mains gas in the capitol, everywhere else is mostly oil, electric and some LPG.

    My house is a three bedroom but only one kitchen, one bathroom and has an electric shower for daily use and as a decent backup for bathing if my gas combi went down. I'm in the town so have mains gas and the system was new when I bought the house. If I was starting afresh I'd install a cylinder because I have the space for one.
  15. quality

    quality Plumber GSR

    Its not your boiler thats the problem but more the control's you have and how you the user uses the system.
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