Hi all,

I recently moved into a house which has a traditional CH and HW system,
ie cylinder/header tank/gas boiler, but no controls which allow me
independent control of either or both - there is one timeswitch that
turns the whole thing on or off. I would like to upgrade this to add a
proper control digital programmer that will allow me to program various
on/off times for the hot water and heating independently, as I'm finding
there are many times when I need one but not the other and it's clearly
not efficient to keep a cylinder of water warm all day in the winter
(and in the summer, I don't want to have to go around the house and turn
down all the TRVs manually when I just need water).

My understanding is that this is a matter of adding two motorized
valves, one to open the HW circuit and one to open the CH circuit - then
drop in the programmer and bob's your uncle. However, I recognize that
this means a control cables will need to be run to each of these valves.
Because the cylinder (where the valves will need to go near) is upstairs
and the boiler and present timeclock are downstairs, this will mean
gouging out of walls, requiring lots of tiling and replastering that I
don't want to contemplate at the moment.

What would be really great would be a way to add this wirelessly. This
way I could stick the box on the wall, and then have it talk over a
radio link to the two motorized valves as required.

Alternatively, the present timeswitch obviously sends a control signal
up to switch on the pump which is right beside the cylinder. I guess it
just switches mains onto it. I wonder could that arrangement be
reversed; I could put the new programmer beside the cylinder, have it
control the two valves from there, and then have it use the wire
currently used to operate the pump to switch mains downstairs which
fires the boiler ?

Advice greatly appreciated ..

On Mon, 23 Jan 2006 01:05:47 +0000, Geronimo W. Christ Esq wrote:

My understanding is that this is a matter of adding two motorized
valves, one to open the HW circuit and one to open the CH circuit -
then drop in the programmer and bob's your uncle.

Or a single three way valve, depending on the plumbing and boiler this
may be an easier option. Does the boiler require a bypass if fitted
into a fully pumped system?

Alternatively, the present timeswitch obviously sends a control
signal up to switch on the pump which is right beside the cylinder.
I guess it just switches mains onto it. I wonder could that
arrangement be reversed;

The only box that doesn't need to be close to the valves/pump is the
room stat. Get a programable and wireless one and a single channel
wired programmer for the HW. "Reversing" the cable between pump and
boiler is not a problem as such but where does the system currently
pick up its mains supply?

--
Cheers
Dave. pam is missing e-mail

In an earlier contribution to this discussion,
Geronimo W. Christ Esq wrote:

Hi all,

I recently moved into a house which has a traditional CH and HW
system, ie cylinder/header tank/gas boiler, but no controls which
allow me independent control of either or both - there is one
timeswitch that turns the whole thing on or off. I would like to
upgrade this to add a proper control digital programmer that will
allow me to program various on/off times for the hot water and
heating independently, as I'm finding there are many times when I
need one but not the other and it's clearly not efficient to keep a
cylinder of water warm all day in the winter (and in the summer, I
don't want to have to go around the house and turn down all the TRVs
manually when I just need water).
My understanding is that this is a matter of adding two motorized
valves, one to open the HW circuit and one to open the CH circuit -
then drop in the programmer and bob's your uncle. However, I
recognize that this means a control cables will need to be run to
each of these valves. Because the cylinder (where the valves will
need to go near) is upstairs and the boiler and present timeclock are
downstairs, this will mean gouging out of walls, requiring lots of
tiling and replastering that I don't want to contemplate at the
moment.
What would be really great would be a way to add this wirelessly. This
way I could stick the box on the wall, and then have it talk over a
radio link to the two motorized valves as required.

Alternatively, the present timeswitch obviously sends a control signal
up to switch on the pump which is right beside the cylinder. I guess
it just switches mains onto it. I wonder could that arrangement be
reversed; I could put the new programmer beside the cylinder, have it
control the two valves from there, and then have it use the wire
currently used to operate the pump to switch mains downstairs which
fires the boiler ?

Advice greatly appreciated ..

Depending to some extent on how many conductors there are in the cable
running between the boiler and airing cupboard, and on where the whole lot
is powered from, what you want to do is probably possible.

It makes sense to concentrate as much of the electrics as you can in the
airing cupboard. The pump is already there. The cylinder stat needs to go
there. It's the best [only viable?] place for the motorised valves. The only
items which need to be somewhere else are the boiler and the room stat. You
already have a cable going to the boiler. You can use a wireless room stat,
with the actual switching bit in or near the airing cupboard, and with the
wireless sensor/programming unit anywhere you like.

You will, of course, need a source of mains power in the airing cupboard. If
the cable from the boiler has enough conductors you may be able to use
that - otherwise you'll need to spur an FCU off a nearby power point.
Whatever happens, put a proper 10-way junction box in the airing cupboard
and wire it all up as per standard S-Plan stuff.

Your main constraint - if there is one - is going to be the existing cable
between airing cupboard and boiler - particularly if the boiler needs to
control the pump in order to provide pump over-run. You could potentially
need five conductors in this cable - Live, Neutral, Earth, Switched Live,
and Pump Control. If the boiler doesn't need to control the pump, and
doesn't need a permanent live, you can get away with three conductors.
--
Cheers,
Set Square
______
Please reply to newsgroup. Reply address is invalid.

On Mon, 23 Jan 2006 10:26:39 +0000, Set Square wrote:

In an earlier contribution to this discussion,
Geronimo W. Christ Esq wrote:

Hi all,

I recently moved into a house which has a traditional CH and HW
system, ie cylinder/header tank/gas boiler, but no controls which
allow me independent control of either or both - there is one
timeswitch that turns the whole thing on or off. I would like to
upgrade this to add a proper control digital programmer that will
allow me to program various on/off times for the hot water and
heating independently, as I'm finding there are many times when I
need one but not the other and it's clearly not efficient to keep a
cylinder of water warm all day in the winter (and in the summer, I
don't want to have to go around the house and turn down all the TRVs
manually when I just need water).
My understanding is that this is a matter of adding two motorized
valves, one to open the HW circuit and one to open the CH circuit -
then drop in the programmer and bob's your uncle. However, I
recognize that this means a control cables will need to be run to
each of these valves. Because the cylinder (where the valves will
need to go near) is upstairs and the boiler and present timeclock are
downstairs, this will mean gouging out of walls, requiring lots of
tiling and replastering that I don't want to contemplate at the
moment.
What would be really great would be a way to add this wirelessly. This
way I could stick the box on the wall, and then have it talk over a
radio link to the two motorized valves as required.

Alternatively, the present timeswitch obviously sends a control signal
up to switch on the pump which is right beside the cylinder. I guess
it just switches mains onto it. I wonder could that arrangement be
reversed; I could put the new programmer beside the cylinder, have it
control the two valves from there, and then have it use the wire
currently used to operate the pump to switch mains downstairs which
fires the boiler ?

Advice greatly appreciated ..

Depending to some extent on how many conductors there are in the cable
running between the boiler and airing cupboard, and on where the whole lot
is powered from, what you want to do is probably possible.

It makes sense to concentrate as much of the electrics as you can in the
airing cupboard. The pump is already there. The cylinder stat needs to go
there. It's the best [only viable?] place for the motorised valves. The only
items which need to be somewhere else are the boiler and the room stat. You
already have a cable going to the boiler. You can use a wireless room stat,
with the actual switching bit in or near the airing cupboard, and with the
wireless sensor/programming unit anywhere you like.

You will, of course, need a source of mains power in the airing cupboard. If
the cable from the boiler has enough conductors you may be able to use
that - otherwise you'll need to spur an FCU off a nearby power point.
Whatever happens, put a proper 10-way junction box in the airing cupboard
and wire it all up as per standard S-Plan stuff.

Your main constraint - if there is one - is going to be the existing cable
between airing cupboard and boiler - particularly if the boiler needs to
control the pump in order to provide pump over-run. You could potentially
need five conductors in this cable - Live, Neutral, Earth, Switched Live,
and Pump Control. If the boiler doesn't need to control the pump, and
doesn't need a permanent live, you can get away with three conductors.

Anyone know if you can get a plain wireless switch for use in any
application not just heating?
I expect it would be quite easy to modify a a wireless cylinder stat to do
this but I would like to know if there is an off the shelf product?


--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at http://www.diyfaq.org.uk
Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html
Choosing a Boiler FAQ http://www.makewrite.demon.co.uk/BoilerChoice.html

In uk.d-i-y, Ed Sirett wrote:
Anyone know if you can get a plain wireless switch for use in any
application not just heating? I expect it would be quite easy to modify
a a wireless cylinder stat to do this but I would like to know if there
is an off the shelf product?

The Easy Switch, from TLC, is meant for lighting but I can see other
applications. I use one for lighting and it works perfectly.

Well, almost perfectly. It's been 100% reliable but it's on when it
should be off and off when it should be on. I get round that problem by
using the other switch contact. Things might not be so easy in other
applications. The makers might have fixed that problem by now.

--
Mike Barnes

Set Square wrote:

Depending to some extent on how many conductors there are in the cable
running between the boiler and airing cupboard, and on where the whole lot
is powered from, what you want to do is probably possible.

I would have to take a look, but the only wire I know about running up
to the cylinder is to control the pump. This is via a fused switch, so I
suspect it is just a mains wire coming up from the timeswitch. I am not
100% sure but I do not believe there is any pump control coming from the
boiler (a Baxi Solo 3/50 PF); I think the switch just turns the both the
boiler and the pump on or off (the pump runs constantly when the system
is on). I wouldn't be surprised to crack it open and find both the
boiler and the pump appliances wired to the same terminals.

So my idea is, instead of sending the mains signal up to the pump, I can
just send the mains down to the boiler. That may involve ensuring that
an appropriate mains ring is available. Would it be really stupid or
non-compliant to try to get away with hanging it off the same ring that
the immersion heater is on ? Having an electrician in to run another
ring up to the cylinder would override my objective of avoiding having
to rip out walls or tiling to do wiring.

It makes sense to concentrate as much of the electrics as you can in the
airing cupboard. The pump is already there. The cylinder stat needs to go
there. It's the best [only viable?] place for the motorised valves. The only
items which need to be somewhere else are the boiler and the room stat. You
already have a cable going to the boiler. You can use a wireless room stat,
with the actual switching bit in or near the airing cupboard, and with the
wireless sensor/programming unit anywhere you like.

This is probably a stupid question, but is a room stat worth bothering
with in the first place, when TRVs are in use and installed ? I see them
in new houses around here but most people I know don't have a stat.

You will, of course, need a source of mains power in the airing cupboard. If
the cable from the boiler has enough conductors you may be able to use
that - otherwise you'll need to spur an FCU off a nearby power point.
Whatever happens, put a proper 10-way junction box in the airing cupboard
and wire it all up as per standard S-Plan stuff.

Good advice, thank you.

Your main constraint - if there is one - is going to be the existing cable
between airing cupboard and boiler - particularly if the boiler needs to
control the pump in order to provide pump over-run. You could potentially
need five conductors in this cable - Live, Neutral, Earth, Switched Live,
and Pump Control. If the boiler doesn't need to control the pump, and
doesn't need a permanent live, you can get away with three conductors.

I think I may just about get away with this. The timer seems to be very
simple, when it is on it seems to just switch mains into the boiler and
pump, when it is off both are stone-dead. I am assuming both the boiler
and the pump are not major power users so it should be simple enough to
wire them off the main that I have.

Thanks for the advice, greatly appreciated. I think I will see about
putting this plan into action.

Set Square wrote:

Depending to some extent on how many conductors there are in the cable
running between the boiler and airing cupboard, and on where the whole lot
is powered from, what you want to do is probably possible.

I would have to take a look, but the only wire I know about running up
to the cylinder is to control the pump. This is via a fused switch, so I
suspect it is just a mains wire coming up from the timeswitch. I am not
100% sure but I do not believe there is any pump control coming from the
boiler (a Baxi Solo 3/50 PF); I think the switch just turns the both the
boiler and the pump on or off (the pump runs constantly when the system
is on). I wouldn't be surprised to crack it open and find both the
boiler and the pump appliances wired to the same terminals.

So my idea is, instead of sending the mains signal up to the pump, I can
just send the mains down to the boiler. That may involve ensuring that
an appropriate mains ring is available. Would it be really stupid or
non-compliant to try to get away with hanging it off the same ring that
the immersion heater is on ? Having an electrician in to run another
ring up to the cylinder would override my objective of avoiding having
to rip out walls or tiling to do wiring.

It makes sense to concentrate as much of the electrics as you can in the
airing cupboard. The pump is already there. The cylinder stat needs to go
there. It's the best [only viable?] place for the motorised valves. The only
items which need to be somewhere else are the boiler and the room stat. You
already have a cable going to the boiler. You can use a wireless room stat,
with the actual switching bit in or near the airing cupboard, and with the
wireless sensor/programming unit anywhere you like.

This is probably a stupid question, but is a room stat worth bothering
with in the first place, when TRVs are in use and installed ? I see them
in new houses around here but most people I know don't have a stat.

You will, of course, need a source of mains power in the airing cupboard. If
the cable from the boiler has enough conductors you may be able to use
that - otherwise you'll need to spur an FCU off a nearby power point.
Whatever happens, put a proper 10-way junction box in the airing cupboard
and wire it all up as per standard S-Plan stuff.

Good advice, thank you.

Your main constraint - if there is one - is going to be the existing cable
between airing cupboard and boiler - particularly if the boiler needs to
control the pump in order to provide pump over-run. You could potentially
need five conductors in this cable - Live, Neutral, Earth, Switched Live,
and Pump Control. If the boiler doesn't need to control the pump, and
doesn't need a permanent live, you can get away with three conductors.

I think I may just about get away with this. The timer seems to be very
simple, when it is on it seems to just switch mains into the boiler and
pump, when it is off both are stone-dead. I am assuming both the boiler
and the pump are not major power users so it should be simple enough to
wire them off the main that I have.

Thanks for the advice, greatly appreciated. I think I will see about
putting this plan into action.

Dave Liquorice wrote:

My understanding is that this is a matter of adding two motorized
valves, one to open the HW circuit and one to open the CH circuit -
then drop in the programmer and bob's your uncle.

Or a single three way valve, depending on the plumbing and boiler this
may be an easier option. Does the boiler require a bypass if fitted
into a fully pumped system?

Easiest is definitely best. I am not sure about the bypass requirements
(what does this mean?). It is a Baxi Solo 3 50 PF (gas fired), but the
manual does not mention this.

The system is already fully pumped and is not gravity fed. I discussed
it about a month or so ago here; the setup is kind of very cheap and
non-standard, and not well known to the very helpful experts frequenting
the group. Basically there is one timeswitch which turns the entire
system on or off, and a pump for the whole caboodle. The cylinder was
fitted with a thermostatic valve and a temperature-sensitive strip. No
other controls. Needless to say, the assorted chaps on the group were
not impressed, for obvious reasons. I'm not too impressed myself either,
running the entire system when I just want enough hot water for a shower
in the morning, or heating a cylinder full of water when I just need to
run a few radiators.

When I moved into the house the termostatic valve on the cylinder was
found to be jammed mostly shut and refused to budge. My plumber as a
temporary measure removed it (I still have it here on my desk and still
can't shift it) just to get me up and running while I gave some thought
to a permanent solution up to and including the possibility of a combi.
I've decided that a combi is going to be disruptive and expensive to do
and potentially a disappointment, so I think I will stick with the
existing traditional arrangement, done up "properly" so that it is more
cost effective.

Alternatively, the present timeswitch obviously sends a control
signal up to switch on the pump which is right beside the cylinder.
I guess it just switches mains onto it. I wonder could that
arrangement be reversed;

The only box that doesn't need to be close to the valves/pump is the
room stat. Get a programable and wireless one and a single channel
wired programmer for the HW.

I am actually hoping for a single timer with fully independent control
over both systems - am I right in saying that the wiring would be a
little simpler ? I would like to be wireless everything. If stats are
necessary I will probably get a cylinder stat as well. I noticed a
programmer which I might get, that provides a temperature readout of
both systems - that's a nice touch.

"Reversing" the cable between pump and
boiler is not a problem as such but where does the system currently
pick up its mains supply?

I believe it gets it from downstairs at the timeswitch, and this is the
one possible snag in the plan. If I can do it without violating any
regulations/laws, I expect I will have to disconnect and isolate the
existing mains supply, and run mains down from the new programmer at the
cylinder, probably off the ring that the immersion heater is on.

Thanks very much for your help. If I can get the mains power question
sorted out then I think I will be armed with a plan to talk over with
the plumber.

On Mon, 23 Jan 2006 21:41:07 +0000, Geronimo W. Christ Esq wrote:

Set Square wrote:

Depending to some extent on how many conductors there are in the cable
running between the boiler and airing cupboard, and on where the whole lot
is powered from, what you want to do is probably possible.

I would have to take a look, but the only wire I know about running up
to the cylinder is to control the pump. This is via a fused switch, so I
suspect it is just a mains wire coming up from the timeswitch. I am not
100% sure but I do not believe there is any pump control coming from the
boiler (a Baxi Solo 3/50 PF); I think the switch just turns the both the
boiler and the pump on or off (the pump runs constantly when the system
is on). I wouldn't be surprised to crack it open and find both the
boiler and the pump appliances wired to the same terminals.

OK. Looks like it's a broken install. The Solo 3 DOES operate the pump
directly from the boiler. So it look like you'll need a multicore from the
airing cupboard to the boiler.






So my idea is, instead of sending the mains signal up to the pump, I can
just send the mains down to the boiler. That may involve ensuring that
an appropriate mains ring is available. Would it be really stupid or
non-compliant to try to get away with hanging it off the same ring that
the immersion heater is on ? Having an electrician in to run another
ring up to the cylinder would override my objective of avoiding having
to rip out walls or tiling to do wiring.

The actual load from the boiler, pump, valves etc is under 1 amp.
It is quite common and I beleive compliant to run the heating from the
immersion 15A radial circuit.



--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at http://www.diyfaq.org.uk
Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html
Choosing a Boiler FAQ http://www.makewrite.demon.co.uk/BoilerChoice.html

On Mon, 23 Jan 2006 21:40:54 +0000, Geronimo W. Christ Esq wrote:

That may involve ensuring that an appropriate mains ring is
available. Would it be really stupid or non-compliant to try to get
away with hanging it off the same ring that the immersion heater is
on ?

I doubt that the immersion is on a ring but on a 15A fuse or 16A MCB
radial. I'm fairly sure there is nothing wrong, regulation wise, with
taking a feed for the CH/HW system from that radial via a suitable
switched fused connection unit. However if a fault develops in the
immersion that requires it to be isolated you also loose power to your
CH/HW... Immersions do go faulty.

This is probably a stupid question, but is a room stat worth
bothering with in the first place, when TRVs are in use and
installed ?

Recent building regs say that when nothing is calling for heat the
boiler must be forced off. This is so that it doesn't cycle just
keeping itself hot, thus wasting energy. With a full TRV system you
can probably do this with a flow switch but the pump has o keep
running through a bypass of some sort, then balancing that flow
against a "demand" for heat as a TRV opens may become an issue. Easier
to fit a wireless programable room stat in your main living room and
take the TRV heads off the rads in that room. The TRVs and room stat
will "fight" if you don't.

--
Cheers
Dave. pam is missing e-mail

On Mon, 23 Jan 2006 21:57:02 +0000, Geronimo W. Christ Esq wrote:

Easiest is definitely best. I am not sure about the bypass
requirements (what does this mean?). It is a Baxi Solo 3 50 PF (gas
fired), but the manual does not mention this.

Probably doesn't need one then. A bypass is a means for water to
circulate through the boiler core after all the valves (TRV or
motorised) have shut. Low capacity aluminium boilers can go into melt
down if you just switch 'em off and stop the water flowing at the same
time. Larger and/or cast iron boiler don't object.

I am actually hoping for a single timer with fully independent
control over both systems - am I right in saying that the wiring
would be a little simpler ? I would like to be wireless everything.

Wireless adds pennies, quite a few pennies. If the pump, motorised
valves, wiring centre, programmer and room stat reciever are all in
the air cupboard they can be all hardwired. Wires are very reliable.

If stats are necessary I will probably get a cylinder stat as well.

I wouldn't run a system without tank and room stats.

--
Cheers
Dave. pam is missing e-mail

Ed Sirett wrote:

I would have to take a look, but the only wire I know about running up
to the cylinder is to control the pump. This is via a fused switch, so I
suspect it is just a mains wire coming up from the timeswitch. I am not
100% sure but I do not believe there is any pump control coming from the
boiler (a Baxi Solo 3/50 PF); I think the switch just turns the both the
boiler and the pump on or off (the pump runs constantly when the system
is on). I wouldn't be surprised to crack it open and find both the
boiler and the pump appliances wired to the same terminals.

OK. Looks like it's a broken install. The Solo 3 DOES operate the pump
directly from the boiler. So it look like you'll need a multicore from the
airing cupboard to the boiler.

Thanks for the reply, Ed. I need to check exactly what way this is
wired, but should I arrange to correct the problem if the pump is not
being controlled from the boiler ? Or put another way, if the system is
wired up correctly then what would I lose/break if I controlled the pump
from the programmer instead ?

The objective here is to avoid running any additional wires between the
pump and the boiler. Though, if push comes to shove, I could have a
check to see how easy this will be. I don't know if they have just
plastered the wire into the wall, or if there will be a duct - if
they've put a duct there then it should be nice and easy.

So my idea is, instead of sending the mains signal up to the pump, I can
just send the mains down to the boiler. That may involve ensuring that
an appropriate mains ring is available. Would it be really stupid or
non-compliant to try to get away with hanging it off the same ring that
the immersion heater is on ? Having an electrician in to run another
ring up to the cylinder would override my objective of avoiding having
to rip out walls or tiling to do wiring.

The actual load from the boiler, pump, valves etc is under 1 amp.
It is quite common and I beleive compliant to run the heating from the
immersion 15A radial circuit.

That clears that one up then, thanks.

Dave Liquorice wrote:

This is probably a stupid question, but is a room stat worth
bothering with in the first place, when TRVs are in use and
installed ?

Recent building regs say that when nothing is calling for heat the
boiler must be forced off. This is so that it doesn't cycle just
keeping itself hot, thus wasting energy. With a full TRV system you
can probably do this with a flow switch but the pump has o keep
running through a bypass of some sort, then balancing that flow
against a "demand" for heat as a TRV opens may become an issue. Easier
to fit a wireless programable room stat in your main living room and
take the TRV heads off the rads in that room. The TRVs and room stat
will "fight" if you don't.

OK. This is good advice, I will do as you have said - better to do it
right and once, rather than have to go in later and start poking with it
again.

Geronimo W. Christ Esq wrote:

OK. This is good advice, I will do as you have said - better to do it
right and once, rather than have to go in later and start poking with it
again.

OK, the penny has dropped on how this works after reading the FAQ. The
output of the time switch is connected through the thermostat's control.
I figure then that the three-port valve would be of the three-position
type, such that when two signals are received at once it remains in the
mid position, switching to either side position when only one signal is
received.

I imagine some slightly less trivial is required for wiring the pump +
boiler, since they will switch on if either or both signals are received
but never if both are off ? I will leave that part for the plumber to
worry about.

"Ed Sirett" wrote in message
news
On Mon, 23 Jan 2006 21:41:07 +0000, Geronimo W. Christ Esq wrote:

Set Square wrote:

Depending to some extent on how many conductors there are in the cable
running between the boiler and airing cupboard, and on where the whole
lot
is powered from, what you want to do is probably possible.

I would have to take a look, but the only wire I know about running up
to the cylinder is to control the pump. This is via a fused switch, so I
suspect it is just a mains wire coming up from the timeswitch. I am not
100% sure but I do not believe there is any pump control coming from the
boiler (a Baxi Solo 3/50 PF); I think the switch just turns the both the
boiler and the pump on or off (the pump runs constantly when the system
is on). I wouldn't be surprised to crack it open and find both the
boiler and the pump appliances wired to the same terminals.

OK. Looks like it's a broken install. The Solo 3 DOES operate the pump
directly from the boiler. So it look like you'll need a multicore from the
airing cupboard to the boiler.



If the boiler doesn't have a run-on timer, what's wrong with wiring the pump
in parallel with the boiler?

Then just 3 core (ie 2 and earth) would be required which is what I assume
he has already?

In an earlier contribution to this discussion,
Geronimo W. Christ Esq wrote:

Set Square wrote:

Depending to some extent on how many conductors there are in the
cable running between the boiler and airing cupboard, and on where
the whole lot is powered from, what you want to do is probably
possible.

I would have to take a look, but the only wire I know about running up
to the cylinder is to control the pump. This is via a fused switch,
so I suspect it is just a mains wire coming up from the timeswitch. I
am not 100% sure but I do not believe there is any pump control
coming from the boiler (a Baxi Solo 3/50 PF); I think the switch just
turns the both the boiler and the pump on or off (the pump runs
constantly when the system is on). I wouldn't be surprised to crack
it open and find both the boiler and the pump appliances wired to the
same terminals.
When installed properly, a Baxi Solo PF *definitely* needs to control the
pump in order to provide pump over-run. Imagine the scenario where the
boiler is going flat out, and is suddenly stopped by the room stat. The
metal parts of the boiler are *very* hot, and the water inside the boiler
will get dangerously hot if it doesn't continue to circulate for a while to
carry the residual heat away. If the pump is simply wired in parallel with
the boiler, it will stop when the boiler stops - and the boiler will
overheat. It may not be a problem with your existing installation because
the pump is always on. But when you put a 'proper' control system on it, it
will be!

So, as I suggested earlier, you actually need 5 wires beween the boiler and
airing cupboard *unless* you cheat! The boiler controls the pump via a
thermostat - and keeps it running until the water has cooled sufficiently.
But this over-run period is typically a minute or less. What you *could* do
is to use a timer - like the ones used with bathroom fans - to keep the pump
going for (say) 2 minutes after the boiler demand has been cut. The timer
could be installed in the airing cupboard.


So my idea is, instead of sending the mains signal up to the pump, I
can just send the mains down to the boiler. That may involve ensuring
that an appropriate mains ring is available. Would it be really
stupid or non-compliant to try to get away with hanging it off the
same ring that the immersion heater is on ? Having an electrician in
to run another ring up to the cylinder would override my objective of
avoiding having to rip out walls or tiling to do wiring.

The immersion heater is probably on a 15A radial circuit. You can spur an
FCU for the heating system - fused at 3A - off that with no problem.

This is probably a stupid question, but is a room stat worth bothering
with in the first place, when TRVs are in use and installed ? I see
them in new houses around here but most people I know don't have a
stat.
As others have said, for energy conservation you need to turn the boiler
right off once both the CH and HW demands are satisfied - and by far the
best way of doing this is by using a room stat and a cylinder stat.

One or two people have mentioned by-pass circuits. You may or may not need
one. A by-pass provides somewhere for the water the go - principally during
the pump over-run period, when the zone valves are closed. If you go for an
S-Plan system with 2 x 2-port valves, you will definitely need a by-pass. If
you go for a Y-Plan system, with a single 3-port valve, you may not -
because there is always at least one port open. Provided you follow the
recommendation of having one radiator with two lockshield valves and no
TRV - so that it can't be turned off - you're probably ok with a Y-Plan. If
you *do* need a by-pass, the easiest way would be to install an automatic
by-pass valve between the flow and return, just before the zone valve(s).
--
Cheers,
Set Square
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On Tue, 24 Jan 2006 10:09:55 +0000, Fred wrote:


"Ed Sirett" wrote in message
news
On Mon, 23 Jan 2006 21:41:07 +0000, Geronimo W. Christ Esq wrote:

Set Square wrote:

Depending to some extent on how many conductors there are in the cable
running between the boiler and airing cupboard, and on where the whole
lot
is powered from, what you want to do is probably possible.

I would have to take a look, but the only wire I know about running up
to the cylinder is to control the pump. This is via a fused switch, so I
suspect it is just a mains wire coming up from the timeswitch. I am not
100% sure but I do not believe there is any pump control coming from the
boiler (a Baxi Solo 3/50 PF); I think the switch just turns the both the
boiler and the pump on or off (the pump runs constantly when the system
is on). I wouldn't be surprised to crack it open and find both the
boiler and the pump appliances wired to the same terminals.

OK. Looks like it's a broken install. The Solo 3 DOES operate the pump
directly from the boiler. So it look like you'll need a multicore from the
airing cupboard to the boiler.



If the boiler doesn't have a run-on timer, what's wrong with wiring the pump
in parallel with the boiler?

Then just 3 core (ie 2 and earth) would be required which is what I assume
he has already?#

This boiler SHOULD operate the pump (it has an overrun stat).
Not to do so is wrong.



--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at http://www.diyfaq.org.uk
Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html
Choosing a Boiler FAQ http://www.makewrite.demon.co.uk/BoilerChoice.html

Set Square wrote:

When installed properly, a Baxi Solo PF *definitely* needs to control the
pump in order to provide pump over-run. Imagine the scenario where the
boiler is going flat out, and is suddenly stopped by the room stat. The
metal parts of the boiler are *very* hot, and the water inside the boiler
will get dangerously hot if it doesn't continue to circulate for a while to
carry the residual heat away. If the pump is simply wired in parallel with
the boiler, it will stop when the boiler stops - and the boiler will
overheat. It may not be a problem with your existing installation because
the pump is always on. But when you put a 'proper' control system on it, it
will be!

This sounds a bit scary, I better get a plumber to take a look at it.
Right now the boiler has been running for about an hour. I turned it off
at the timeswitch, and confirmed that the pump definitely goes off. Is
this like, a red alert situation or (merely) something that I should try
to get sorted at some point in the near future ?

When the timeswitch turns the boiler off, it appears to be completely
electrically isolated, so I don't see how it would have a separate mains
supply that would allow it to control the pump in that state. Best thing
to do is get someone in to have a look at the way this has all been wired.

One or two people have mentioned by-pass circuits. You may or may not need
one. A by-pass provides somewhere for the water the go - principally during
the pump over-run period, when the zone valves are closed. If you go for an
S-Plan system with 2 x 2-port valves, you will definitely need a by-pass. If
you go for a Y-Plan system, with a single 3-port valve, you may not -
because there is always at least one port open. Provided you follow the
recommendation of having one radiator with two lockshield valves and no
TRV - so that it can't be turned off - you're probably ok with a Y-Plan. If
you *do* need a by-pass, the easiest way would be to install an automatic
by-pass valve between the flow and return, just before the zone valve(s).

Yup, the bathroom radiator is setup with two lockshield valves, so I
suspect I'll go with Y-plan.

Dave Liquorice wrote:

I am actually hoping for a single timer with fully independent
control over both systems - am I right in saying that the wiring
would be a little simpler ? I would like to be wireless everything.

Wireless adds pennies, quite a few pennies. If the pump, motorised
valves, wiring centre, programmer and room stat reciever are all in
the air cupboard they can be all hardwired. Wires are very reliable.

I have noticed that is expensive, but I will only need a wireless room
stat; if I wire everything as you have said (this is the plan) then the
tank stat does not need to be wireless.

In an earlier contribution to this discussion,
Geronimo W. Christ Esq wrote:

Set Square wrote:

When installed properly, a Baxi Solo PF *definitely* needs to
control the pump in order to provide pump over-run.
Snip

This sounds a bit scary, I better get a plumber to take a look at it.
Right now the boiler has been running for about an hour. I turned it
off at the timeswitch, and confirmed that the pump definitely goes
off. Is this like, a red alert situation or (merely) something that I
should try to get sorted at some point in the near future ?

If the boiler overheats, it will trip out and have to be re-set manually
before it will work again. Presumably you haven't had this? What flow
temperature do you currently have? - i.e. what is the boiler thermostat
currently set at? If the flow temperature is quite low - maybe to stop the
DWH getting too hot - there's a bigger margin of error before residual heat
and trippiing becomes a problem. But when you've updated your controls, you
try to try to run the boiler at 80 degC - in which case tripping is likely
unless you've got some over-run mechanism for the pump.

When the timeswitch turns the boiler off, it appears to be completely
electrically isolated, so I don't see how it would have a separate
mains supply that would allow it to control the pump in that state.
Best thing to do is get someone in to have a look at the way this has
all been wired.
That's why I said you need *five* wires, as follows:
- Switched live (tells the boiler to fire, as at present)
- Neutral (as at present)
- Earth (as at present)
- Permanent Live [Needed as the source for the pump control signal]
- Pump live [Connected to Live whenever the boiler decides that the pump
needs to run]

The boiler is likely also to have a pump neutral and possibly pump earth
terminal in addition to the others - but there are plenty of alternative
options for neutral and earth floating round in the airing cupboard, so you
can leave these unconnected at the boiler end.
--
Cheers,
Set Square
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Set Square wrote:

This sounds a bit scary, I better get a plumber to take a look at it.
Right now the boiler has been running for about an hour. I turned it
off at the timeswitch, and confirmed that the pump definitely goes
off. Is this like, a red alert situation or (merely) something that I
should try to get sorted at some point in the near future ?

If the boiler overheats, it will trip out and have to be re-set manually
before it will work again. Presumably you haven't had this?

No, it has never tripped on me.

What flow
temperature do you currently have? - i.e. what is the boiler thermostat
currently set at? If the flow temperature is quite low - maybe to stop the
DWH getting too hot - there's a bigger margin of error before residual heat
and trippiing becomes a problem. But when you've updated your controls, you
try to try to run the boiler at 80 degC - in which case tripping is likely
unless you've got some over-run mechanism for the pump.

The setting is at about 9 o'clock on the dial which is pretty low. Even
then the boiler cycling is quite bad (off for about 40 seconds, on for
about two minutes continuously). When I set the thermostat higher than
this the cycling is even worse. It is the cycling that has led me to
consider taking action to get the system properly set up.

When the timeswitch turns the boiler off, it appears to be completely
electrically isolated, so I don't see how it would have a separate
mains supply that would allow it to control the pump in that state.
Best thing to do is get someone in to have a look at the way this has
all been wired.

That's why I said you need *five* wires, as follows:
- Switched live (tells the boiler to fire, as at present)
- Neutral (as at present)
- Earth (as at present)
- Permanent Live [Needed as the source for the pump control signal]
- Pump live [Connected to Live whenever the boiler decides that the pump
needs to run]

The boiler is likely also to have a pump neutral and possibly pump earth
terminal in addition to the others - but there are plenty of alternative
options for neutral and earth floating round in the airing cupboard, so you
can leave these unconnected at the boiler end.

Thanks. I don't feel sufficiently competent to start messing around at
this, but I appreciate being informed about how it should be expected to
work

In an earlier contribution to this discussion,
Geronimo W. Christ Esq wrote:


The setting is at about 9 o'clock on the dial which is pretty low.
Even then the boiler cycling is quite bad (off for about 40 seconds,
on for about two minutes continuously). When I set the thermostat
higher than this the cycling is even worse. It is the cycling that
has led me to consider taking action to get the system properly set
up.

Cycling occurs when the rate at which your boiler is producing heat is
greater than the rate at which the radiators and HW cylinder coil can
dissipate it. It should cycle *less* if you turn up the boiler stat because
with the radiators being hotter, they can dissipate more heat. Have you
tried increasing the pump speed?

If the boiler *still* cycles excessively when the house is hot enough in the
coldest weather, it sounds as if it's too big for the job. You can probably
reduce the boiler output a bit by reducing the gas pressure. This will be
explained in the installation manual.

Actually, re-reading what you wrote above - indicating that the boiler is
firing for 120 seconds in every 160 (i.e. 75% of the time) I wouldn't worry
about it if it only does it in steady state conditions. [I would expect the
boiler to run continuously for much longer than that when first starting up
from cold - does it?]
--
Cheers,
Set Square
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Thanks for the reply again. This is very useful.

Set Square wrote:

The setting is at about 9 o'clock on the dial which is pretty low.
Even then the boiler cycling is quite bad (off for about 40 seconds,
on for about two minutes continuously). When I set the thermostat
higher than this the cycling is even worse. It is the cycling that
has led me to consider taking action to get the system properly set
up.

Cycling occurs when the rate at which your boiler is producing heat is
greater than the rate at which the radiators and HW cylinder coil can
dissipate it. It should cycle *less* if you turn up the boiler stat because
with the radiators being hotter, they can dissipate more heat. Have you
tried increasing the pump speed?

I haven't tried messing with the pump speed (was concerned that this
might cause overflow into the header tank?) but I may experiment based
on your advice.

I will have a go at turning the thermostat up and measure the rate at
which cycling occurs. To be honest with you, I am not long moved into
the house and I'm still trying to find my feet regarding which radiators
to leave on or off while the system is running, and how long to run the
timer for. I'm in Northern Ireland and we pay stupendous amounts for gas
over here, so it's about trying to get a balance between heating the
place sufficiently and not getting an insane gas bill

Actually, re-reading what you wrote above - indicating that the boiler is
firing for 120 seconds in every 160 (i.e. 75% of the time) I wouldn't worry
about it if it only does it in steady state conditions. [I would expect the
boiler to run continuously for much longer than that when first starting up
from cold - does it?]

The boiler burns continuously for about 45 minutes from cold before it
enters the state where the cycling occurs. After this time I've got a
full cylinder of nicely hot water.

In an earlier contribution to this discussion,
Geronimo W. Christ Esq wrote:


The boiler burns continuously for about 45 minutes from cold before it
enters the state where the cycling occurs. After this time I've got a
full cylinder of nicely hot water.

That sounds perfectly normal to me - and certainly nothing to worry about.
--
Cheers,
Set Square
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