Relative lives in an inner, three story town house and needs a new boiler. The current ~20 year old boiler is located on the ground floor with the flue running up through the other two (concrete) floors. There's a garage to the front and a kitchen to the rear and the boiler is in a walk-in cupboard between the two.
She's been told that the boiler must go on an outside wall with the flue through the wall, or on the top floor with the flue through the flat roof. Question is, why can't it go where the existing boiler is? Is there a limit on the length of flues for modern boilers?
It t' old days this was not a problem as a conventionally flued boiler could draw air from the room in which it was sited and the exhaust gas was so hot that it could easily find its way up a long large bore flue to the top of house.
Nowadays it is not considered safe for new installations to draw air from the room in the appliance is sited and the regulated requirement for condensing boilers having low exhaust temperatures means that the flue gasses no longer have the oomf to make it up a long flue on their own.
The solution is fan assisted balanced flues which are frequently concentric (exhaust inside and inlet outside) and although extension pieces are available they are expensive and there is a limit on the length that the fan can suck and push the gasses.
Boilers do exist that are capable of driving long flues but this is a specialist requirement so there aren't that many around and some of them are expensive. Almost universally they split the flue into 2 pipes to drive long distances. I know of:
Keston - Reasonably priced boilers, and flues are formed from low cost (but inflexible) 50mm muPVC drainpipe. I have a Keston Celsius 25 boiler but I'm not sure I would give it an unqualified recommendation
Mann Micromat - A top quality German boiler but pricey, extension flue is flexible corrugated plastic tube which is cheaper than metal extension but still expensive for long runs. Formerly distributed by Eco Hometec but I've lost track of who are doing them now.
Ariston - Saw these in a block of flats a while back and noticed they were using long flues via adaptors, no detailed info.
To cut a long story short, if you chose to go the long flue route then you will be making life more difficult for yourself, you will be paying more and tying yourself to a number of specialist suppliers whose support network may not be as extensive as the mainstream market and as a result you may have difficulty with spares in the future.
More mainstream boilers are most easily fitted to outside walls but many can drive concentric flues of 3 or 4m which may mean that you can fit them in a cupboard and route the flue to the outside.
See also the group boiler choice faq from Ed Sirett:
Thanks for that. The alternative horizontal flue through the wall into the garage and then out above the garage door was one that I had thought of but, for some unfathomable reason didn't go down too well with her.
I ordered a set of servicing spares for mine a few weeks ago thinking they might arrive by end of March when its service is due, and unlike my previous experiences, every part was in stock and arrived next day.
BTW, Keston stopped making the C25 over a year ago, although I have seen stock still for sale quite recently.
Andy had me worried there for a minute but it looks like they have introduced the Qudos 28 as a mid level domestic replacement that fixes some of the original issues I had with the Celsius 25. There are separate control temperatures depending on the demand source with thermistor sensor modulated control of DHW temp and they promise compatibility with low grade heat from solar panels in the future. Full list is: Room Compensation, Weather Compensation, Solar Control, Modulating DHW Reheat, Solar Thermal, Analog Demand (0-10VDC), External Lockout Signal, Remote Fascia Panel plus LCD control panel and display of system params (flue temp, flow/return temp, other temp densors) in installer mode. They've retained the 20m/50mm maximum flue length and even extended it to 60m when increased to 65mm. Suffix H is heat only without pump or expansion vessel, suffix S is a system unit with those parts incorporated.
£722.08 and £788.13 inc vat for the 'H' & 'S' respectively at discountedheating.
The Qudos 28 has a spiral tube stainless steel heat exchanger top mounted burner design. They went back to their original designs. The Celsius by the time they dropped it had all it problems ironed out. A late model Celsius is good buy.
However, my neighbour has had a boiler installed in her loft. It went AWOL after a few months, BG came out to fix it (the original fitter couldn't get out to it and there were young children in a very cold house) and the guy refused to go up into the loft. Elf and safety! He was persuaded to change his mind when said neighbour asked him what his supervisor would say when he smelled the alcohol on his breath!
...at a price that commands attention for what it offers in design and function. Reliability? Not been around long enough. however they appear to be using proven parts from other boilers.
My biggest gripe -- lack of availability of spares in a timely fashion -- looks like it might have got sorted too, but that's on a sample of only one order. Might be as a result of Keston having been bought out a while back.
I might consider them when a 17 year old Profile pops its cloggs (although it's currently running faultlessly and has had no breakdowns that I know of, certainly none in the last 7 years). When I looked about
6 months back, I don't recall them having a low powered non-combi in the range.
The sophistication and the solar hook makes it attractive to the specialist market and the techies here but I do wonder whether it will make it in the mainstream market, it's just too clever. I hope that they and it make it, at last a company who listen.
It will work with just a simple switched live for the followers of Ned Ludd.
I doubt whether many people would use it domestically with more than a thermostat and the weather compensator. The smart move would be to include the sensor for that in the package because it's a very low cost item (basically a two wire semiconductor in a weatherproof box).
It may be interesting for small commercial installations involving multiple boilers controlled by an analogue or Opentherm controller.
Whether it makes it in the market will depend on the number of puffy anoraks for Plumbcenter counter staff and lunches for their managers.
The ideal setup for this boiler (the Keston C36 combi is the same boiler with a water section added) is to have the outside weather compensator fitted (cost about £22). The DHW cylinder sensor (not sure of price) and the Opentherm standard room temp controller/programmer/optimiser fitted (Keston use the Honeywell Chronotherm, which can be bought a lot cheaper elsewhere rather than the £133 Keston ask for it). Then this is a substantial setup and at a price people can afford. Anyone can do that, just as simple as rigging up crap stats.
The C38 combi can have the outside temp sensor fitted and the Chronotherm optimiser programmer too. DHW is not an issue as it is a combi. Then for what you get and pay this is also well priced. Keston have to offer advanced control interfaces to five the boiler a hedge. Broag also sell a well priced boiler offering similar specs using tried and tested parts too.
I have heard no bad reports on the Qudos range....yet. The Celsius turned me away from Keston after making some super simple and reliable boilers previously. It should be fine using parts from other boilers in the range.
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