What's the current state of play for replacing back boilers with
another back boiler? I seem to remember hearing that the rule requiring
condensing boilers would kill back boilers off.
My mother has a back boiler which is nearing the end of its useful
life. There is nowhere convenient to put a wall-mounted boiler without
redoing the kitchen. Any chance of her getting another back boiler? I
also remember that there were some exemptions from the
My understanding as a non-plumber is that your mother may be able to have a
like-for-like replacement if the installation qualifies under the exemption
procedure, that is, if installation of a condensing boiler instead of a
non-condensing boiler is impractical or too costly. See
<http://www.communities.gov.uk/index.asp?id31464> or just Google for
exemption procedure back boiler.
A great many people are in the same position with faithful back
boilers giving up the ghost and needing replacement.
As has been said there may be a case for doing it in an above board
manner, but it may be a case of finding a friendly plumber/corgi who
does not think much of the regulations and does as he has always done,
Just going through that now. Seems to be solicitors making themselves
seem busy/covering their arses more than anything.
Demanding paperwork on 16 year old windows and 15 year old kitchens.
Problems seemed to vanish when told to go away. :))
most combi boilers have vertical flues now with many elbow/bend options,
dont bother with the expensive manufacturers roof slate and use a selkirk
flashing....biggest problem i find is getting a suitable waste for the
condensate when they are sited in the loft...dont forget the loft area up to
the boiler will need boarding, a fixed light and a ladder up to the
loft.....otherwise when your super efficient boiler gives up the ghost the
service engineer may refuse to repair..
The soil pipe usually rises in the loft. It can be teed into this. If no
facility for a condensate waste then buy an Amtos boiler. They are
condensing boiler that don't need a drain.
Top quality boilers - RR quality and very well designed. Plenty of UK
From my understanding of "two Jags" rules, it doesn't matter whether there
is anywhere "convenient" for the new boiler or not. There is a points system
and if you score "x" number of points you may qualify for an exemption and
be able to replace the existing back-boiler with a new back-boiler. If,
however, you "fail" the test, you'll have no choice but to have a condensing
Having said that, you don't really want to stay with a back boiler unless
you really have to because they are so inefficient. Our old one was
something like 65% efficient, as opposed to the 90-odd percentage efficiency
of the new condensing boiler. The cost of gas being what it is, it's well
worth trying to overcome the obstacles of positioning a new boiler. We had
our new boiler installed in the loft with the condensate drain poking out
between a couple of slates, so that the condensate just dribbles over a tile
or two, down into the gutter, and away.
I had this conversation with the tame plumber I'd found to fix our boiler
the other day when it gave up the ghost a couple of days before Xmas.
I'd like to replace the current backboiler with a loft mounted condensing
model (I also want to reclaim the room used for the airing cupboard/hot
water tank but have a fear of combis from past experience (ie. crap ones)).
plumber wasn't keen claiming that a) I'd need a vertical flue which narrows
the range drastically and b) it gets too cold up there so the frost stat
would been it would run so often in winter that it would wipe out a lot of
the efficiency gains.
Comments from people who have done this?
I can imagine building some sort of "shed" that is insulated a bit to
help with the later problem (loft is currently just slate - no felt or
I've never seen any convincing argument that condensing *systems* are
more efficient in real terms.
I don't doubt that the *boilers* may be more efficient in terms of gas
energy in vs hot water energy out, but that ignores the system such a
boiler is used in.
With recommendations that a certain percentage of radiators have no
TRV, in order to ensure the < 60 degC water-return temperature, then
heat is being lost by the system in order to run 'efficiently'. That
this waste heat is kept in-house in some way is no different to the
case of my back-boiler's pilot-light. Not only keeping the boiler warm
ready for the next burn-cycle, the chimney stack is in the centre of
the house, adjacent to four rooms and the airing cupboard. I doubt any
heat at all from the pilot gets out of the house.
We now have the silly system that DHW tanks are so well insulated that
airing cupbords need radiators in them! What was 'lost heat' is now
having to be supplied by the 'efficient' condensing-boiler system!
How many of these condensing systems are set up correctly?
My MiL had one fitted two years ago. The boiler return-water is
scalding hot and I doubt very much if the boiler is working in the
'condensing' mode. Turning the temperature down causes the boiler to
I could spend a couple of days with a non-contact thermometer getting
it all set up, but MiL is 'eccentric' and wouldn't welcome the
intrusion. It's easier to leave things be.
I'm not sure it is. My kitchen is about a foot longer and wider than
my arm-span. By the time the appliances have taken up the floor-space,
there is precious little floor-room left. All storage has to be in the
wall-cupboards, and getting rid of one for a condensing boiler would
be a considerable loss.
With W-shaped roof supports taking up much room in the loft, mounting
a condensing boiler on the flank wall, at the opposite end to the
hatch, means long pipe runs, and access that would be difficult even
for a fit person.
The 'dead space' in my house, ideal for a boiler, is where the current
one is; but apparently I've got to play some kind of stupid game in
order to get one according to the 'regulations'.
The man who last serviced my boiler, which is now 27 years old, said
his dad had one exactly the same that was 43 years old and in perfect
working order. I'll stick with what I've got.
On 2006-12-31 11:23:14 +0000, Frank Lee Speke-King
That's not correct. You are missing the point that the majority of condensing
boilers modulate the burner to reduce output and favour a low return
There isn't waste heat....
Most of the inefficiency of this type of boiler arises from heat going
out through the flue.
I would agree with you that the pilot is a second order effect.
A few years ago on the steps to increasing requirements for boiler
efficiency, there was
a requirement for better than 78% (IIRC) SEDBUK efficiency. Quite a
number of products that were just over and
that had had pilots were re-engineered with electronic ignition to
bring them under the limit. I believe there's
about a 3-4% or so difference.
Ah that's something else.
There is a common misconception here. There is not a sudden arrival
at orgasm or Nirvana when "condensing mode" happens. What actually
happens is an increase in efficiency with reducing return temperature all
the way down. At the dew point, around 54 degrees, the *rate* of improvement
increases. It is not a step function.
Is the boiler a modulating type? If it is, and is short cycling then
something is wrong.
Something else again.
I can see your point, and in this respect, the exemptions on points in
the building regulations
don't address these practical issues very well.
Which when one considers the additional requirements to provide safe
accesses such as boarding and rails
for servicing, can become a challenge.
You can run through the points system check and may be able to achieve
enough that fitting a wall mount condensing boiler is not a requirement
to the rules.
I did an exercise of this for my parents house (backboiler in centre of
house) and it was possible to achieve the minimum points requirement.
There's no requirement to change it out.
However, rather than trying to justify no having a condensing boiler on
grounds that are not really valid,
it would be interesting to know if some enterprising manufacturer has
made or is planning to make
a condensing back boiler that fits the footprint of existing models at
a reasonable price. I suspect in many cases a condensate pump would
be needed in order to handle that aspect conveniently, but this should
It ought to even be possible to arrange air intake and flue to be
concentric and run up a flexible liner to a roof terminal. This would
have the advantage of being able to do away with the room vent for air
supply to a conventional boiler. Considering the installed base of
back boilers, which will eventually become uneconomic to repair, this
should be an interesting propostion.
Many thanks for your helpful reply to my not necessarily well worded
posting; but essentially I was saying that the efficiencies quoted for
condensing boilers could be more imaginary than real, for some
I'd be very grateful if you could indicate the sort of things that you
put in to the 'points' exercise for your parent's situation.
I'd be glad of the information against the day my back boiler goes
belly-up - it pays to be prepared!
On 2007-01-01 11:43:57 +0000, Frank Lee Speke-King
Here's the starting point, and the following page.
For their case, the points totted up as follows. Remember that the
existing is a back boiler behind a fireplace in the lounge and is
located in the middle of the house:
Property type - others, fuel natural gas: 590 points
New boiler in different room? Yes. 350 points
of the two possible places for installation, one would
require an extended flue (>2m); the other would require a condensate
pump. These are scored with 200 or 100 respectively.
Either takes the points total to > 1000 which is the exemption threshold.
On Fri, 29 Dec 2006 15:48:47 -0800, Martin Pentreath wrote:
As people have said there is an exemption procedure for replacing a
gas (or oil) back boiler unit with a similar model, the exemption
procedure is usually possible for flats with BBUs.
If you or your installer contact building control they may be able to
argue the case for a non condensing unit on a one off case basis with the
officer, especially if they exceed the minumum standards in other respects
such as insulation and controls.
It might be possible to get a condensing BBU but they
are likely to be very expensive. Indeed the BBU replacement whether
conventional or condensing will probably cost more than a top of the range
wall hung unit.
It all comes down to weighing up the different approaches and seeing which
looks the least unattractive. (There will never be a really nice option
when replacing a BBU).
Ed Sirett - Property maintainer and registered gas fitter.
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