On 5 Nov 2005 10:52:19 -0800, "
wrote:
Hello
I wonder if someone can help me with a problem. I am currently trying
to organise a replacement condenser or combi boiler for my mother who
lives in a 4 bedroom semi detached property by herself. 8 rads will be
fiited with trc's however we have received conflicting advice based on
which type of boiler and where the condensation pipe will go if indeed
she has a condenser fitted. The long and short of this is that she
currently has a jonhson starley J25-32 ducted air system the boiler is
in the kitchen (ground floor) with a hot water tank in one of the
bedrooms. the initial idea is to fit a combi condenser (baxi 105 31kw
or platinium 33kw) into the airing cupboard where the hopt water tank
used to be however one installed is proposing taking the pipe for the
waste condensed water out of the wall under the bedroom floorboard then
run the pipe about 12 feet along the house horizontally then down to
the drain and the other is just saying a condenser is not suitable and
she will need a combi boiler as you can only fit condensers to an
outside wall. Can anyone advise if they think either of these methods
is unsuitable. Also one of the guys seems trust worthy however his
father is retired (so has no corgi reg anymore) he is starting and
waiting to complete the course so they have advised currently they are
having a colleague (who I have confirmed with corgi is registered with
them) to inspect install and pass for safety.
Any help greatly appreciated
Thanks
Neil
The first thing is not to confuse the terms "combi" and condensing
boilers. A combi boiler is one which has the ability to heat water
from the mains directly without the use of a cylinder. A condensing
boiler is one which has internals and a control system designed such
that there is condensing of some of the combustion products to water
inside the boiler. This causes release of additional (latent) heat
and results in greater efficiency. Said water has to be piped away.
You can have condensing and non-condensing versions of combi boilers
and condensing and non-condensing versions of heating boilers (i.e.
those that work with a HW cylinder etc)
So there are two decisions to make. The first is whether she wants a
combi boiler and to remove having the boiler in the kitchen and
cylinder in the bedroom. Bear in mind that the water flow rate from
a combi is unlikely to be as great as is currently being achieved from
a cylinder and baths etc. will take longer to fill, especially in the
winter. The boiler size is upper mid range and would work
reasonably well, especially for a person on their own who may not be
too concerned if it takes 10-15mins to fill a bath. However, if it
is on the radar to move within the lifetime of the boiler and the
house is such that a bath and shower in concurrent use is possible,
then this may be a consideration and a combi of this size could be
marginal for that. One thing that should be checked for a combi
implementation is the mains cold water flow rate. This can be done
at the kitchen sink with a bucket, a stop watch and a calculator.
One thing that is common in houses with a roof tank and cylinder is
that only a 15mm pipe is used from the stop tap to the roof tank. If
this is the case, then it may need to be replaced with a 22mm pipe.
On the condensing/non-condensing question, it is certainly not the
case that they can only be fitted to an outside wall. manufacturers
have gone to a great deal of trouble to provide solutions to address
fitting in other places.
For example:
- For many models, flues can be concentric pipes or separate intake
and outlet types. With some, flues can even be constructed with 50mm
high temperature waste pipe and run over tens of metres.
- Condensate production is usually no more than a trickle and can be
run through plastic pipe. The distances mentioned are relatively
long, so the important thing would be to make sure that there is some
slope, especially more so outside, to prevent water laying and
freezing.
- There are condensate pumps. These are used normally when a boiler
is installed where the drain is higher - e.g. in a cellar - to raise
the water to an outside drain level. However, another option could
be to run the condensate pipework across the loft and join a soil
stack. Pumps cost a few tens of pounds and perhaps this could provide
a neater solution?
The second installer may be a bit of a Luddite or may simply be trying
to suggest a lower cost option, or may simply have no experience of
condensing boilers. This is ridiculous really, because there is
only the issue of the condensate drain that makes the difference
anyway. There is a medium to long term cost saving with a condensing
boiler in terms of running costs and a reasonable assumption that gas
prices will increase.
You can refer to the exemption rules at the ODPM web site, where there
are details of an assessment procedure.
This leaflet is useful as a guide to that plus some installation
suggestions.
http://www.odpm.gov.uk/embedded_object.asp?id=1130731
It may be that the criteria for not having to have a condensing boiler
could be met if she wanted to go that way.
Semidetached house 590 points
New boiler in different room 350 points
Extended flue 2m 200 points
Total is 1140 (greater than 1000 limit) just with these things, so she
doesn't *have* to have a condensing model if she didn't want to do so
(assuming new flue is 2m).
--
..andy