Andy Hall wrote:

On Sun, 14 Dec 2003 00:47:43 +0000 (GMT), "Dave Liquorice"
wrote:


On Sat, 13 Dec 2003 20:23:32 +0000, Steven Briggs wrote:


I glad Andy's pointed out his interpretation of part L, as I did
think I was technically non-compliant having no room stat.

Andy's setup if *very* sophisticated and in the 30th centuary compared
to most heating systems in the UK. I don't doubt that with such a
level of monitoring and control very good effciencies can be achieved
but those levels do not exist on the vast majority of installed
systems.


Don't forget though that this part of the Building Regulations only
apply when a new boiler is fitted either into an existing property or
a new one.

My description of my own system was by way of illustration more than
anything else.

My conclusion from looking through the Approved Document and the Good
Practice Guide is that they are aimed at practitioners in the trade
who are still installing conventional simple boilers and simple room
stats because a) they understand them and b) they are cheap.


I think that is precisely the case.



Therefore, given that that is the status quo, the point that struck me
was that the authors are suggesting the marriage of the two as good
practice because realistically that is what is often installed. They
even refer to this as a minimum set of controls. With a simple boiler
firing to full output or off and with simple bimetal thermostats,
short cycle firing as a result of TRVs being virtually closed down is
going to use some amount of energy which can easily be saved by
hooking up a simple room stat.

However, even with a relatively simple modern condensing boiler is
modulating to quite a low level and most that I have seen fire up at a
level according to the amount of heat demand as referenced by the
water temperatures. After all 3kW firing up for a minute once an
hour is actually less than the pump uses.



Precisely.

The issue is 'conservation of heat and power'.

The modve away from single stat installations to TRV'ed installations is
there to reduce unwanted heating of unused or little used rooms, and
allow better control of house temperature. The gains are potentially
considerable.

Keeping a single stat is a complete nonsense, excepat in the one case
mentioned - some idiot who runs his heating in the summer. In which case
one would likley set the stat above the level where it would ever come
on in winter, to make sure the TRV'sd actually do their work.

The short bypass loop TRV solution is IMHO arguably better than no
TRV's, and in practice no worse than a single stat would up - and indeed
may be better, because if the single stat is wound up with no bypass,
the bloody pump will stall.

I am not aware how the flow swiych thing actually works, because no one
has explanied how the flow switch senses deamand when the pump is
stopped. And if it simply cuts the boiler, not the pump as it were, then
its no different from using the boiler internal stat.




The test is can the boiler fire to keep itself and/or a small primary
loop warm/hot, if can then then, IMHO, it fails Part L1. There are
many ways, from a simple room stat or flow switch to systems like
Andy's, to achieve the desired result.


My point was really that it strikes me that the Approved Document and
Good Practice Guide make a point about the interlock thing because it
can be easily achieved with what is often still installed today not
that the authors are prescribing what *must* be done.

The legislation requires only that reasonable provision is made to
save energy.


Precsiely. In the same way that I was able to install single glazing in
a new build, by demonstrating overall energy efficiency.

The spirit of the regulations is to avoid uncessary boiler firing, not
uneccessary pump action. Addong a single stat doesn't do anythung ecept
in the case where the whole house is already warmer than the heating
could actually make it, and the bozo has left the heating on..



Once modulating and condensing boilers become the norm as it is
suggested that will be the case within two years, the energy to be
saved by interlocking the controls with a room stat is likely to be a
lot less significant to the point where I suspect that using one will
not make a whole lot of difference.

I am assuming here that time controls will indeed remain as they are
which is to fully shut down the boiler and pump (notwithstanding
overrun) when the heating period has finished.

Remember that with burner modulation the heat output goes down to a
few kW to balance the heat loss so the residue of what we would be
talking about would be on days when for *part* of the heating period
boiler heat is required, but because of rising temperatures outside
not for all of it. The number of days a year when that scenario
happens in such a way that a very low burn rate of a few kW once or
twice an hour is too much is very small.
From an engineering standpoint at that stage it becomes very much a
corner case to worry about switching everything off.



Yup.
All I can say is that teh gains from 'single stat in the kitchen' to
'all TRV's and turn teh stat up to max' were significant for me. It
wasn;t ideal, but it worked pretty well for a few years.

I couldn't even use a single stat on my fan heaters now, because they
heating requirements for each room and the heat flow between then is far
too complex. AND they don't shut the flow down, because the stats
control the fans, not the flow, unlike TRV's.

One does the best one can with available technology.

Ideally one would have a stat in every room, and a zone valve, and some
temp sensors outside...and build a bigger version of what my car has -
they call it 'climate control - but as yet, no one makes such a control
box.

The cost to me to install, to save a piddly 50 quid of oil a year, would
be immense. Not least in terms of wioring, which would be equivalent to
a complete new lighting installation in complexity. Better savings are
assured by simply turning the whole heating system off when not
required. when I need heat, I simply slap the system on, overriding the
time clocks, and in summer its set to 'always off' and I simply punch it
on when the odd cold day turns up.








.andy

To email, substitute .nospam with .gl