When I moved to my present home I inherited a 6 year old Thermecon oil
boiler supplying 16 radiators. I have replaced all the 40 year old
radiators and converted the previously very antiquated system to a
fully pumped one with boiler interlock. It occurs to me that there
must be quite a bit of heat wasted at the boiler when the room stat
reaches temperature and the boiler shuts off, and that it might be
worthwhile arranging for the pump to overrrun so that the already
heated hot water is pumped round for a further 10 minutes or so rather
than just wasted heating up the utility room that houses the boiler
(at present the pump switches off the moment the stat reaches
temperature).

Any comments please? Would this be worthwhile, or is it a crazy
idea? How would one arrange it - what electrical equipment would one
need - please specify exactly, I have little technical know-how about
these sorts of things.

Keith

In article
,
Keefiedee wrote:
When I moved to my present home I inherited a 6 year old Thermecon oil
boiler supplying 16 radiators. I have replaced all the 40 year old
radiators and converted the previously very antiquated system to a
fully pumped one with boiler interlock. It occurs to me that there
must be quite a bit of heat wasted at the boiler when the room stat
reaches temperature and the boiler shuts off, and that it might be
worthwhile arranging for the pump to overrrun so that the already
heated hot water is pumped round for a further 10 minutes or so rather
than just wasted heating up the utility room that houses the boiler
(at present the pump switches off the moment the stat reaches
temperature).

Any comments please? Would this be worthwhile, or is it a crazy
idea? How would one arrange it - what electrical equipment would one
need - please specify exactly, I have little technical know-how about
these sorts of things.

I did just this to my old boiler - which was a basic electrics gas one.
But I'd say 10 minutes is too long. Think I ended up with three.
I'm not sure if there's anything available commercially to do the job - I
made my own. I've still got it somewhere - it's surplus to requirements
since the current boiler does all this itself. But like all this sort of
thing installing it requires a degree of knowledge to modify the wiring.

--
*There are two kinds of pedestrians... the quick and the dead.

Dave Plowman London SW
To e-mail, change noise into sound.

"Dave Plowman (News)" wrote in message
...
In article
,
Keefiedee wrote:
When I moved to my present home I inherited a 6 year old Thermecon oil
boiler supplying 16 radiators. I have replaced all the 40 year old
radiators and converted the previously very antiquated system to a
fully pumped one with boiler interlock. It occurs to me that there
must be quite a bit of heat wasted at the boiler when the room stat
reaches temperature and the boiler shuts off, and that it might be
worthwhile arranging for the pump to overrrun so that the already
heated hot water is pumped round for a further 10 minutes or so rather
than just wasted heating up the utility room that houses the boiler
(at present the pump switches off the moment the stat reaches
temperature).

Any comments please? Would this be worthwhile, or is it a crazy
idea? How would one arrange it - what electrical equipment would one
need - please specify exactly, I have little technical know-how about
these sorts of things.

I did just this to my old boiler - which was a basic electrics gas one.
But I'd say 10 minutes is too long. Think I ended up with three.
I'm not sure if there's anything available commercially to do the job - I
made my own. I've still got it somewhere - it's surplus to requirements
since the current boiler does all this itself. But like all this sort of
thing installing it requires a degree of knowledge to modify the wiring.

I would fit a pipe stat.
Just set it to pump until the temp drops below a useful level.
Wire it across the permanent live and the pump live.
About a tenner.

On Nov 5, 1:38*am, Keefiedee wrote:
When I moved to my present home I inherited a 6 year old Thermecon oil
boiler supplying 16 radiators. *I have replaced all the 40 year old
radiators and converted the previously very antiquated system to a
fully pumped one with boiler interlock. *It occurs to me that there
must be quite a bit of heat wasted at the boiler when the room stat
reaches temperature and the boiler shuts off, and that it might be
worthwhile arranging for the pump to overrrun so that the already
heated hot water is pumped round for a further 10 minutes or so rather
than just wasted heating up the utility room that houses the boiler
(at present the pump switches off the moment the stat reaches
temperature).

Any comments please? *Would this be worthwhile, or is it a crazy
idea? *How would one arrange it - what electrical equipment would one
need - please specify exactly, I have little technical know-how about
these sorts of things.

Keith

If it would increase efficency it would have been included, all heat
is still going into the home

In article
,
ransley wrote:
Any comments please? Would this be worthwhile, or is it a crazy
idea? How would one arrange it - what electrical equipment would one
need - please specify exactly, I have little technical know-how about
these sorts of things.

Keith

If it would increase efficency it would have been included,

Not necessarily. You might as well say all boilers are the same.

all heat is still going into the home

It might go into the place where the boiler is situated - but that could
well not be the best place.

--
*If a turtle doesn't have a shell, is he homeless or naked?

Dave Plowman London SW
To e-mail, change noise into sound.

Dave Plowman wrote:

Keefiedee wrote:
It occurs to me that there must be quite a bit of heat wasted
at the boiler when the room stat reaches temperature and
the boiler shuts off, and that it might be worthwhile arranging
for the pump to overrrun...

I did just this to my old boiler - which was a basic electrics gas one.
But I'd say 10 minutes is too long. Think I ended up with three.
I'm not sure if there's anything available commercially to do the job - I
made my own. I've still got it somewhere - it's surplus to requirements
since the current boiler does all this itself. But like all this sort of
thing installing it requires a degree of knowledge to modify the wiring.

I was also considering doing something like this as my boiler is located in
a boiler house, and I would prefer the boiler residual heat to be used in
the house. The boiler is an old cast iron design that doesn't need a pump
run-on circuit itself.

Unfortunately the circuit is quite complicated as I have three zones, and
each zone's motorised valve closes when its associated thermostat is
satisfied. The auxiliary contacts on the zone valves control the boiler and
pump, so all three zone valves have to be closed before the boiler (and
pump) shuts down.

I need the circuit logic to recognise when all of the zones have been
satisfied, and then keep the last zone valve open whilst the pump run-on
operates (no point pumping against a closed valve!). And then, if the last
zone to be satisfied is the Domestic Hot Water, would I want the pump run-on
to pump through the DHW circuit? Probably not, as it might overheat the
tank.

And what about during summer, when the CH is off? Where will the pump
run-on send the residual heat from the boiler then?

At the moment I have a gravity circuit that brings the residual heat from
the boiler into the bathroom towel rail. Maybe I should stay with that.
--
Mike
-Please remove 'safetycatch' from email address before firing off your
reply-

In an earlier contribution to this discussion,
mlv wrote:


I was also considering doing something like this as my boiler is
located in a boiler house, and I would prefer the boiler residual
heat to be used in the house. The boiler is an old cast iron design
that doesn't need a pump run-on circuit itself.

Unfortunately the circuit is quite complicated as I have three zones,
and each zone's motorised valve closes when its associated thermostat
is satisfied. The auxiliary contacts on the zone valves control the
boiler and pump, so all three zone valves have to be closed before
the boiler (and pump) shuts down.

I need the circuit logic to recognise when all of the zones have been
satisfied, and then keep the last zone valve open whilst the pump
run-on operates (no point pumping against a closed valve!). And
then, if the last zone to be satisfied is the Domestic Hot Water,
would I want the pump run-on to pump through the DHW circuit? Probably
not, as it might overheat the tank.

As you say, with an S+ Plan system, it is the closing of the zone valves
which switches the boiler off, so during any over-run period, the valves are
all - by default - closed, thus preventing any circulation to dissipate the
residual heat.

How about deciding which zone you want to dump to, and plumbing in an
automatic by-pass valve in parallel with the appropriate zone valve? You'd
have to adjust the by-pass valve so that it *only* opened when all the zone
valves were closed - much the same as a normal by-pass installation except
that the return is via a zone-worth of radiators rather than direct.

And what about during summer, when the CH is off? Where will the pump
run-on send the residual heat from the boiler then?


Using my suggested solution, via whichever zone you've selected. OK, you
don't *want* the radiators to get a bit warm, but it doesn't really matter.
[It relies on having at least rad open, of course - but presumably the one
near the room stat will be, and won't have a TRV on it].

As far as achieving pump over-run is concerned, you can do it with one of
these. http://tinyurl.com/6gk3k2
It's intended for keeping bathroom fans running for a while after you switch
the light off, but works just as well with a CH pump. I'm using one which is
set to about 2 minutes on my system, and it works fine. [My Baxi Solo MkI
*does* require pump over-run, but implements it rather crudely by initially
switching the pump off with the flame and switching it back on again when
the water temperature gets up to the stat setting - by which time it is
sometimes too late, and over-heats and trips. My system keeps the pump
running for a couple of minutes whatever, and ensures that the residual heat
can get away *before* the temperature builds up to trip point. I have an
automatic by-pass valve between flow and return in the airing cupboard (a
long way from the boiler) so there's plenty of scope for dissipating the
heat].
--
Cheers,
Roger
______
Email address maintained for newsgroup use only, and not regularly
monitored.. Messages sent to it may not be read for several weeks.
PLEASE REPLY TO NEWSGROUP!

On Wed, 5 Nov 2008 20:20:30 -0000, "Roger Mills"
wrote:

As far as achieving pump over-run is concerned, you can do it with one of
these. http://tinyurl.com/6gk3k2
It's intended for keeping bathroom fans running for a while after you switch
the light off, but works just as well with a CH pump. I'm using one which is
set to about 2 minutes on my system, and it works fine.


Sorry to reply so late but I clicked the link and saw that it is a
Manrose timer from TLC. How have you got on with this?

I've been sent a few of these but found them wildly inaccurate. When
set to 20 minutes on the front I get at most 7 minutes on. YMMV. I
suppose if you ignore the markings on the front and set it to the
required time and leave it alone it's ok, but it makes setting a new
delay a pain as it is trial and error, or was in my case. If the
legend on the box matched the time delay it would be so much easier.

In an earlier contribution to this discussion,
Stephen wrote:

On Wed, 5 Nov 2008 20:20:30 -0000, "Roger Mills"
wrote:

As far as achieving pump over-run is concerned, you can do it with
one of these. http://tinyurl.com/6gk3k2
It's intended for keeping bathroom fans running for a while after
you switch the light off, but works just as well with a CH pump. I'm
using one which is set to about 2 minutes on my system, and it works
fine.


Sorry to reply so late but I clicked the link and saw that it is a
Manrose timer from TLC. How have you got on with this?

I've been sent a few of these but found them wildly inaccurate. When
set to 20 minutes on the front I get at most 7 minutes on. YMMV. I
suppose if you ignore the markings on the front and set it to the
required time and leave it alone it's ok, but it makes setting a new
delay a pain as it is trial and error, or was in my case. If the
legend on the box matched the time delay it would be so much easier.

It seems to do the job. I agree that the scale isn't very accurate - and is
very small, with less than one revolution of a smallish knob covering a
range of 1-60 minutes (I think). So it's a bit "suck it and see" when
setting it - by nudging it a bit and then using a stop watch to see how long
it over-runs. This is not too bad, since I've set it to about 4 minutes - so
you're not waiting about for too long. Once set, it seems to be pretty
consistent.
--
Cheers,
Roger
______
Email address maintained for newsgroup use only, and not regularly
monitored.. Messages sent to it may not be read for several weeks.
PLEASE REPLY TO NEWSGROUP!

mlv wrote:

I need the circuit logic to recognise when all of the zones have been
satisfied, and then keep the last zone valve open whilst the pump run-on
operates (no point pumping against a closed valve!). And then, if the last
zone to be satisfied is the Domestic Hot Water, would I want the pump run-on
to pump through the DHW circuit? Probably not, as it might overheat the
tank.

no chance whatsoever of the cylinder 'overheating'