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Ed Sirett
 
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On Tue, 21 Jun 2005 21:14:29 +0000, Martin Evans wrote:



o plumber 2 (who spent a considerable amount of time with me - what
patience) suggested going to a combi boiler (although he would fit a
conventional one) - in fact a Worcester Greenstar 440 floor standing
combi boiler. He said

I Maybe wrong but IIRC all Greenstar boilers are condensing.

a) at 20l/min at 35 degrees C rise, running on mains pressure (subject
to testing mains pressure which I'm given to believe is good) it was
more than sufficient to match my existing pumped shower and everything
else.


Initially before the store of HW in the boiler gives out this is likely
true. The usability of the system is likely to be good enough except for
high speed bath running.


b) it would be cheaper to install than keeping my existing system as
it was far less components and mostly required ripping (bypassing)
existing system out rather than renewing/replacing. Basically, the
cold water tank would be bypassed, the cylinder goes, my shower pump
goes, electrics are trivial since all that is needed it something to
the boiler. I liked the sound of losing my shower pump IF the output
at the shower head was as good since the shower pump is noisy.


A wall stat (preferrably programmable) will also be needed to comply with
current regs.


c) my gas supply to boiler was 15mm and needed to be 22mm. There is no
easy way to get a 22mm pipe from the 22mm pipe at the back of my meter
to the boiler but it could be run outside (around a 3m run) so long as
the pipe was held off the wall.

And properly sleeved etc. etc. All true.


d) To check the new system would cope/match my existing shower pump I
needed to lookup the output from my pump (i've struggles with this as
the plate on it quote 3 l/min numbers). Also, I needed to check the
spec of the shower valve in my ensuite to ensure it was OK for the new
increased standing pressure.


These are not the end of the world to replace later if they are
unsatisfactory.


e) we discussed pluming etc and the flue would be routed outside and
up the wall to above head height. (=2m).


That avoids the need for a terminal guard but no word on the possible
pluming problems and air-space wars.


f) we discussed reliability of Worcester 440 and he said he had fitted
loads, it was good, needed to be serviced once a year and although
slightly more involved than a conventional boiler was not time
consuming or expensive. On board diagnostics would even detect a leak
in my heating system.

Fair comment.


g) Mentioning some pipework in concrete floor he was unperturbed,
suggesting the increased pressure of my new sealed system was not that
high and if existing system was working I'd be OK.


See my previous post, however a positive attitude has much to commend it.

h) I mentioned past experience of combi boilers (over 12 years ago) and
he said the worcester 440 was miles ahead of whatever I had then and I
would not suffer from excessive reduced flow in winter. He did go on
quite a bit about what temperature my shower ran at and how I was mixing
alot of cold water with hot to get confortable.


Fair comment. This boiler has good performance at the expense of floor
space, size and weight.



i) he said my existing cylinder (although only 5 years old) was not up
to spec since it did not have 2" of insulation (I might have the exact
number wrong).


Possibly true.



j) all (optional but included in his price) would be in the boiler
itself except for a room thermostat. He pointed out the problem with
having a room thermstat in the hall where the radiator had a TRV.


The TRV must go. As discussed.


k) the worcester 440 had an in built 12l (I think) vessel which had some
advantage in the speed in which hot water reached my taps - not sure
exactly.


See 'f' and 'a' and 'h'


Cost £2600 (for combi boiler worcester 440 floor standing boiler,
replacement gas supply to boiler, ripping out / bypassing old system) -
sealed system.

Probably about right.



o plumber number 2

quote not received yet but it was for a wall mounting Worcester 3XX
(something) 12l/min output at X degrees C rise (have not got the
brochure).

o concurred with plumber 1 than cylinder was not up to spec. Also said
the hot water feed to my shower pump was too high in the cylinder. Also
said the cylninder would be better turned through 90 degrees for easier
access to valve - fair enough.

o concurred with plumber 1 re TRV and room therm in same room.

o on business of 22mm gas feed to boiler - some needed it some don't -
often plumbers size up from 15 to 22 - a bit wishy washy - I was not
certain what was required but if a 22mm pipe was required as with
plumber 1 it could be run along outside wall.

o on combi boilers he would do a quote for both but a combi would be
more expensive since it required ripping out a lot of stuff - somewhat
at odds with plumber 1 who said the exact opposite.

o as with plumber 1 he'd need specs for ensuite shower valve as it might
not be up to increased standing pressure if we went combi boiler but the
myra shower valve in bathroom was certainly OK (I knew this anyway as
some tosser who previously installed shower in bathromm before we moved
here plumbed it in to the bath supply where the cold water was mains
pressure). When it leaked badly I needed to replace it in a hurry and
found I needed a more expensive valve to handle the imbalance. Since
then it has been replumbed to the cold tank.

o on combi boilers and my concern over loss of output in winter and at
my main ensuite shower he said it would cope so long as someone did not
use any water elsewhere in the house (whether cold or hot). He
recommended not having a combi boiler.

o servicing required for worcester 3XX was once every 12 to 18 months
and would cost around £50.

o room thermostat was required and they would not need to put cables in
as it was a (cableless) radio one.

o would quote for a powerflush at £395 which would take the best part
of a day as it involved connecting to heating system and flushing
through plus connecting to each radiator individually. When I suggested
this sounded alot (BG quoted £200) he said if the system had been
drained recently and was clean I could just ignore that in the quote.
They would have to drain the system twice anyway and lfush it with some
agent. He didn't try to sell it to me especially when I said the system
had been drained more than 5 times in the last 2 years alone and drained
out clean (also all of my radiators except one is brand new).

Someone who having got a powerflush gadget actually wishes to used only
when needed, a rare event, a mark of honesty perhaps?

o mains pressure was good in my area and not a worry.

o it cost them £5 to register the installation with Corgi who would
send me something I needed to keep as it would be required when I sold
my house.


Actually £4 by phone and £2.50 online. Hardly worth itemising really.
As to whether you _really_ will need it when you sell - who knows.
It is a legal requirement to register the exchange of a heating appliance
with building control it is done with this.


o gas mains was being updated in my area since it fell off too much (and
caused some boilers to shut down) early in the morning when all these
new condensing boilers switched on.


Some condensors are quite sensitive to under-pressure others are very
tolerant. Condensors use no more gas and possibly less than
non-condensors. Combis tend to place bigger peak
demands on the supply network. However if the mains are being fixed in
your area what's the problem?


What I think is a summary of the "true" bits of advice/information I
received from BG, local plumbers and this news group a

o you have to fit a condensing boiller unless you can amass 1000 pts on
a rather difficult to achieve scale. Certainly, a replacement boiler is
unlikey to achieve 1000 pts.

Yep


o plumning - I'm not going there - it seems a contentious issue.



o when moving to a condensing boiler you need a fully pumped system (no
gravity fed hot water) - this is law.

Yep

o don't have TRV on the radiator in the same room as a room thermostat -
also avoid rooms with other heat sources - kitchen, rooms with fires etc
Ed.

Just to be clear . TRVs are needed nearly everywhere. The roomstat is
needed somewhere but not with the TRV - in the hall is a good place.
remove existing TRV if needed.



o condensing boilers produce condensate which is slightly acidic and has
to have somewhere to drain away.

Yep


o some boilers come with bypass valves, some don't. You can't go all
TRVs without a bypass valve.


If the boiler says it needs a bypass you must have one TRVs or not.


o You need a "boiler interlock" that completely turns off the boiler
when the house is hot. Normally this is supplied by the room thermostat.
If there is none, another method must be used, such as a flow switch on
the heating circuit - thanks Christian/Andy/John.

Yep, but go for the room stat. The alternative gear will not be cheaper,
people will be less familiar with it. A programmble room stat can provided
an accessible heating control.

o some condensing boilers are modulating so instead of a constant power
output they adjust to conditions. Minimum outout of boiler is worht
looking at.

I don't think you'll find any fixed power modern boilers condensing or not.
The lower minimum the better. Provided the HW heating is OK (combi).
If you co for a cylinder then I suggest calculating the heating
requirements and then selecting the right sized boiler again lloking at
the minimum.

o There should be electrical bonding from the meter to the main earthing
point in the house. The service bonding ought to be done on the consumer
side of the meter rather than the supply as used to be the case.

Yep


o water cylinders are subject to building regs and upgrading a system
might (or must) mean upgrading the cylinder to current regs. Also, see
fast recovery cylinders (this was not mentioned to me by anyone
quoting).

A compliant cylinder is a fast(ish) cylinder.


Both plumbers seem to be saying the right sort of things give or take a
few details. The second one wishes to fit a cheaper lighter simpler combi
with much less HW output. Still good for shower (but probably not as good
as what you have with a pump).

If the wiring from the hall to the boiler is awkward then the £50 extra
for a wireless room stat could be worth the extra.

--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at http://www.diyfaq.org.uk
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