On 7 Dec 2003 14:51:01 -0800, (lodtop) wrote:

Any help will be appreciated.

Got a combination boiler,it started leaking all over the place last
night.

Got an emergency plumber in today at £57 / half hour plus VAT.

He told me it's the heat exchanger ( will confirm this with Ideal
Boilers tomorrow) although he didn't pinpoint the leak.

He's quoting £1500 all in for a new boiler.

Our house is a small 3 bedroom end terrace - the current boiler size
is 90,000 Btu/h and the one he recommended is exactly the same size,
this is despite telling him we are extending next year and would need
a bigger boiler.

Not necessarily.

BTUs are a deprecated unit, but 90,000 of them equates to 26kW which
is a fairly powerful boiler for a small house.

Having said that, if it is an older property with solid brick walls
with no cavity or no cavity insulation, it may be close to its limit.
The only way that you could tell properly is by calculating the heat
losses and doing so properly. For an older property, by far the
largest losses are through the walls so it is important to check
properly and not rely on some plumber looking around and guessing with
a ready reckoner. The radiator manufacturers have programs on their
web sites to help calculate the heat losses. All you have to do is
measure the surfaces (floors, walls, windows) and plug them into the
program, room by room, choosing the correct material for each surface.
You'll then get a total heat loss for the property. Add about 20%
to this for boiler sizing.

When you add an extension, modern building regulations are going to
require cavity walls and double glazing and the heat losses in this
part are going to be a lot less (could be only a quarter) of the
equivalent size of existing house.




So.......any recommendations? Should I get a new boiler now (condensor
or combi) or should I get a new heat exchanger fitted as we'll be
extending next year and will have to get a new boiler anyway?

I would draw a line under the existing boiler and get a new one.
Generally the heat exchanger is one of the most expensive parts.

Are you happy with the hot water performance of the combi? If not,
and the water flow is adequate you could go for a larger one with more
output to hot water.

Modern condensing boilers (and you can get condensing combi boilers)
tend to have control systems which result in the boiler running at a
lower than full output (called modulation) to the heating when there
is less demand on a warmer day. For the hot water, and when required
for the heating, it will run at full power.

So it doesn't matter if you oversize the boiler for heating purposes
particularly. You could go for a 30-35kW boiler for example.

Whether the £1500 is a good price depends on what you would be
getting. It's worth spending a bit more for a decent condensing
product like Vaillant or others with a stainless steel heat exchanger
since these have a longer lifetime than most other materials.
You would most likely not get one of those fitted for £1500 though,


Certainly it is worth going for a condensing model as you'll shave
approx 25% or so off of your energy consumption if the existing boiler
is a fairly old type. Do make sure that the system is properly
flushed and dosed with corrosion inhibitor as this may have been a
contributing factor to the demise of your existing boiler.

Also, if you do have an older property, and it is practical, consider
insulating the insides of the outside walls. Something like 50mm
Celotex sheet would have an enormous difference with solid walls.








Thanx, Lod

..andy

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