(B)util kitchen din rm (st) liv rm
______________________________________________ 22mm gas

I I I I I
I I I I I
I I I I I
I I I I I
I I I I XI
I I I I I

(B) = Boiler (st) = room stat. X= gas meter, the rest is self evident

so I went ahead and bought the biasi condensing combi and flue
during B&Qs last 20% off bonanza. less than £500 all in, which
was nice. then I read a bit more into the new installation regs and
discover I need TRV on ALL the rads rather tham all but one, and
a room stat into the bargain.

fair enough on the TRVs, I'm replacing one rad and adding another
when the system is drained down and I'm hoping that the rads which
didn't have TRVs aren't siezed.

the main question I have is regarding the room stat and how to wire it
back to the boiler. 10 years ago when the house in question was refurbed
(toshed out) the 22mm gas pipe was run along the wall at skirting height,
through the living room, dining room and kitchen where the crap plumber
dropped it down to 15mm* and continued into the utility rom. a few months
later, the boiler was installed in the utility room and all was well.

the 22mm gas pipe was boxed in behind the 7" skirting, clipped onto
the brick and follows through under the kitchen units into the utility room.

here's the part P question. how can I run the connecting wire for the room
stat from the boiler to the living room ? I'm ok in the utility room as there
are no units, the kitchen will be a right pain as there is no way I can remove
the units, access under the kitchen will be by the plinth only. the dining
room skirting can be popped off as we are redecorating that room anyway,
same goes for the living room.

I plan to run the cable with the gas pipe, behind the skirting, the full length
of the house as it would be one really simple cable pull of about 12m but
I'm guessing there will be issues with part P and possibly part L ?

the big Q: does a simple 2 wire stat connection come under part P OR part L ?

can anyone see any regulatory problems with what I plan to do ?

the boiler work is being commissioned and signed off by my brother in law
who is corgi regd and has done part P and part L but he has got it wrong in
the past and I'd like some second opinions as the house will be on the
market soonish and I don't want any legal hiccups.

thanks in advance




* being changed to 22mm

here's the part P question. how can I run the connecting wire for the room
stat from the boiler to the living room ?

Room stat wiring will usually be low voltage, hence outside scope of Prat P.

discover I need TRV on ALL the rads rather tham all but one, and
a room stat into the bargain.

You are mistaken. Fitting TRVs on the room with the room stat is not
permitted by regulations and will make energy consumption worse, as it
defeats the boiler interlock.

If you wish to have all rads with TRVs, then you'll need to abandon the room
stat and fit a flow switch interlock and possibly rewire the pump.

here's the part P question. how can I run the connecting wire for the room
stat from the boiler to the living room ?

Use an RF thermostat. No fixed wiring required. No redecorating. As the
central heating is on the other side of an FCU, you can probably get away
without Part P.

You can get cheaper ones than the following, but it is the best. (Honeywell
CM67RF).

http://www.plumbworld.co.uk/761-12687

Christian.

here's the part P question. how can I run the connecting wire for
the room stat from the boiler to the living room ?

Room stat wiring will usually be low voltage, hence outside scope of Prat
P.

That is not true. Room stat wiring is usually at full mains voltage. Some
combi boilers (but certainly not all) may have low voltage signalling, but
almost all system boiler installations will not be. With a combi, you
certainly can't assume that it is low voltage without investigating the
installation manual.

Christian.

Christian McArdle wrote:
here's the part P question. how can I run the connecting wire for
the room stat from the boiler to the living room ?

Room stat wiring will usually be low voltage, hence outside scope of
Prat P.

That is not true. Room stat wiring is usually at full mains voltage.
Some combi boilers (but certainly not all) may have low voltage
signalling, but almost all system boiler installations will not be.
With a combi, you certainly can't assume that it is low voltage
without investigating the installation manual.

Christian.

the only reference to stat voltage that I can find in the inatallation
manual / service manual is "DO NOT CONNECT LIVE WIRES TO
TERMINALS TO WHICH THE ROOM THERMOSTAT MUST BE
CONNECTED"

from which I deduce that the boiler /needs/ a stat and is low volatge ?

Christian McArdle wrote:
discover I need TRV on ALL the rads rather tham all but one, and
a room stat into the bargain.

You are mistaken.

I'm not, well, I wasn't, it was the brother in law who said /all/ rads need TRVs
and the interweb said all but one. I was firmly with the web on that one but
he disagreed. I thought that having two stats would confuse the boiler.

I /must/ have a room stat so the front room will be the rad without the TRV,
the only issue now is the cable run through the kitchen and behind the
skirting. if it is low voltage I shouldn't have a problem with parts P & L

is that right ? I'm only using a cheap £5.99 bimetallic room stat.

Mike Harrison wrote:
here's the part P question. how can I run the connecting wire for
the room stat from the boiler to the living room ?

Room stat wiring will usually be low voltage, hence outside scope of
Prat P.

fingers crossed :-)

I /must/ have a room stat so the front room will be the rad without the
TRV,
the only issue now is the cable run through the kitchen and behind the
skirting. if it is low voltage I shouldn't have a problem with parts P & L

Well the good news is that it will be low voltage. The bad news is that it
will probably be 230V "low voltage".

is that right ? I'm only using a cheap £5.99 bimetallic room stat.

Seriously, throw away that w*nky bimetallic stat and fit a proper RF
programmable thermostat. It will be a fraction of the work and it will
probably earn its value back through optimum start and more accurate
control. You can also program it in the comfort of your living room, rather
than requiring a torch in a cupboard to an old style programmer. With an RF
stat, you can normally program it from your chair, as you can unclip it from
the wall.

Christian.

the only reference to stat voltage that I can find in the inatallation
manual / service manual is "DO NOT CONNECT LIVE WIRES TO
TERMINALS TO WHICH THE ROOM THERMOSTAT MUST BE
CONNECTED"

from which I deduce that the boiler /needs/ a stat and is low volatge ?

Nope. You may deduce no such thing from that statement.

Christian.

"." [email protected] wrote in message
...
Christian McArdle wrote:
discover I need TRV on ALL the rads rather tham all but one, and
a room stat into the bargain.

You are mistaken.

I'm not, well, I wasn't, it was the brother in law who said /all/ rads
need TRVs
and the interweb said all but one. I was firmly with the web on that one
but
he disagreed. I thought that having two stats would confuse the boiler.

I /must/ have a room stat so the front room will be the rad without the
TRV,
the only issue now is the cable run through the kitchen and behind the
skirting. if it is low voltage I shouldn't have a problem with parts P & L

is that right ? I'm only using a cheap £5.99 bimetallic room stat.

To have TVRs on all rads one method is have an auto by-pass valve fitted
between the flow and return. Have a boiler which can maintain a constant
flow temp. Have a it set to 80C. Balance the system to 10C across the rads
and boiler, if an existing system. Install a pipe stat on the boiler
return, so that the burner is off at 71C.

Christian McArdle wrote:
I /must/ have a room stat so the front room will be the rad without
the TRV, the only issue now is the cable run through the kitchen and
behind the skirting. if it is low voltage I shouldn't have a problem
with parts P & L

Well the good news is that it will be low voltage. The bad news is
that it will probably be 230V "low voltage".

eh ? low 230V as in not 415V ? elaborate.

is that right ? I'm only using a cheap £5.99 bimetallic room stat.

Seriously, throw away that w*nky bimetallic stat and fit a proper RF
programmable thermostat. It will be a fraction of the work and it will
probably earn its value back through optimum start and more accurate
control. You can also program it in the comfort of your living room,
rather than requiring a torch in a cupboard to an old style
programmer. With an RF stat, you can normally program it from your
chair, as you can unclip it from the wall.

thanks for that. the bimetallic stat is being fitted in the front room, close to the dining
room door for even temperature sensing and1.5m (thereabouts) directly above the
line I wish to run the single 12m cable for which the holes are alread drilled. no torches
or cupboards will be used in this installation.

£5.99 vs at least £20 for a digital version, it's cost effective for me and any future cost
effectiveness can be dealt with by the new owners. all I really need to determine is the
cable run in relation to the various regulations.

keeping it simple and cheap is the prime mover, adding a £100 RF stat does
not make any sense within this context and as the walls have to be re decorated
anyway, chasing the walls out and running themover with a trowel full of jollop
isn't really a problem.

it's the cable run that's at issue.

tia

Doctor Drivel wrote:
"." [email protected] wrote in message
...
Christian McArdle wrote:
discover I need TRV on ALL the rads rather tham all but one, and
a room stat into the bargain.

You are mistaken.

I'm not, well, I wasn't, it was the brother in law who said /all/
rads need TRVs
and the interweb said all but one. I was firmly with the web on that
one but
he disagreed. I thought that having two stats would confuse the
boiler.

I /must/ have a room stat so the front room will be the rad without
the TRV,
the only issue now is the cable run through the kitchen and behind
the skirting. if it is low voltage I shouldn't have a problem with
parts P & L

is that right ? I'm only using a cheap £5.99 bimetallic room stat.

To have TVRs on all rads one method is have an auto by-pass valve
fitted between the flow and return. Have a boiler which can maintain
a constant flow temp. Have a it set to 80C. Balance the system to
10C across the rads and boiler, if an existing system. Install a
pipe stat on the boiler return, so that the burner is off at 71C.

how about the cable run ?

what's your thoughts on that in relation to the various regs ?

tia

from which I deduce that the boiler /needs/ a stat and is low volatge ?

Nope. You may deduce no such thing from that statement.

P.S. A bimetallic thermostat REQUIRES a 230V connection, or it will work
very badly...

A "volt-free contact" requirement from the boiler will mean that you need
some sort of electronic stat with built in batteries. Almost all
programmable (and many electronic) thermostats meet this requirement.

Old style bimetallic thermostats have a 3 terminal connection and use 230V
power from the programmer to run a tiny heater that gives much more accurate
control to the bimetallic strip. This heater will not function as intended
on a low voltage supply and the temperature stability will be all over the
place.

Christian.

Christian McArdle wrote:
from which I deduce that the boiler /needs/ a stat and is low
volatge ?

Nope. You may deduce no such thing from that statement.

P.S. A bimetallic thermostat REQUIRES a 230V connection, or it will
work very badly...

A "volt-free contact" requirement from the boiler will mean that you
need some sort of electronic stat with built in batteries. Almost all
programmable (and many electronic) thermostats meet this requirement.

Old style bimetallic thermostats have a 3 terminal connection and use
230V power from the programmer to run a tiny heater that gives much
more accurate control to the bimetallic strip. This heater will not
function as intended on a low voltage supply and the temperature
stability will be all over the place.

Christian.

so I will have to up the budget by £13 and buy a battery powered digital stat
/if/ the boiler is compatible with such a device ?

thanks for your continuing input, how about the cable run in relation to the regs ?

To have TVRs on all rads one method is have an auto by-pass valve fitted
between the flow and return. Have a boiler which can maintain a constant
flow temp. Have a it set to 80C. Balance the system to 10C across the
rads
and boiler, if an existing system. Install a pipe stat on the boiler
return, so that the burner is off at 71C.

How is interlock achieved? You don't have a flow switch in this design.
Explain how the burner never fires if the outside temp is, say, 30C.

As it stands, this system will cycle, as when the water drops below 71C, it
will fire up again even if there is no call for heat.

Christian.

Well the good news is that it will be low voltage. The bad news is
that it will probably be 230V "low voltage".

eh ? low 230V as in not 415V ? elaborate.

Indeed.

If you're thinking of the around 12V sort of mark, that is officially "extra
low voltage".

£5.99 vs at least £20 for a digital version, it's cost effective for me
and any future cost
effectiveness can be dealt with by the new owners. all I really need to
determine is the
cable run in relation to the various regulations.

Well if the cable run is simple, then there's nothing to worry about. I
would only use an RF stat if a wired one was not possible. Remember that a
mechanical stat can't work on a twin wire installation. It requires 3 wires
including a 230V supply from the programmer, which may not available from a
combi.

keeping it simple and cheap is the prime mover, adding a £100 RF stat does
not make any sense within this context and as the walls have to be re
decorated
anyway, chasing the walls out and running themover with a trowel full of
jollop
isn't really a problem.

Well, if redecorating is not a problem, then you can't beat wires for
reliability.

Christian.

so I will have to up the budget by £13 and buy a battery powered digital
stat
/if/ the boiler is compatible with such a device ?

The boiler will be compatible with a battery powered digital stat.

thanks for your continuing input, how about the cable run in relation to
the regs ?

Either:

(a) claim you know nothing about it
(b) get it signed off at great expense by an electrician
(c) get it signed off at great expense by the local council
(d) use an RF stat

With it buried in plaster, I doubt you'd be able to claim it wasn't fixed
wiring, despite the fact that the whole lot sits off an FCU/plug+socket. You
could always ask your local BCO for their opinion.

Christian.

Christian McArdle wrote:
Well the good news is that it will be low voltage. The bad news is
that it will probably be 230V "low voltage".

eh ? low 230V as in not 415V ? elaborate.

Indeed.

If you're thinking of the around 12V sort of mark, that is officially
"extra low voltage".

ah, of course.

£5.99 vs at least £20 for a digital version, it's cost effective for
me and any future cost effectiveness can be dealt with by the new
owners. all I really need to determine is the cable run in relation
to the various regulations.

Well if the cable run is simple, then there's nothing to worry about.
I would only use an RF stat if a wired one was not possible. Remember
that a mechanical stat can't work on a twin wire installation. It
requires 3 wires including a 230V supply from the programmer, which
may not available from a combi.

keeping it simple and cheap is the prime mover, adding a £100 RF
stat does not make any sense within this context and as the walls
have to be re decorated anyway, chasing the walls out and running
themover with a trowel full of jollop isn't really a problem.

Well, if redecorating is not a problem, then you can't beat wires for
reliability.

right, now you're up to speed :-) can you see any problems with the cable run
following the gas pipe in the diagram depicted in my original post, in relation
to the various regulations ?

right, now you're up to speed :-) can you see any problems with the cable
run
following the gas pipe in the diagram depicted in my original post, in
relation
to the various regulations ?

Well a quick look shows that it is non-viable, as you may not conceal wiring
behind the skirting board unless mechanically protected or bury it more than
50mm deep.

You might get away with it ELV (although I'm not entirely sure on this), but
this will require a relay at the boiler if the boiler isn't already ELV on
its thermostat connection.

Christian.

Christian McArdle wrote:
so I will have to up the budget by £13 and buy a battery powered
digital stat /if/ the boiler is compatible with such a device ?

The boiler will be compatible with a battery powered digital stat.

thanks for your continuing input, how about the cable run in
relation to the regs ?

Either:

(a) claim you know nothing about it

is one option I am seriously considering. when we toshed the house out about
10 years ago, several cables were installed which haven't yet been used.
remote control for the ex immersion heater, extra HD shower circuit, etc. and I
do have a large amount of pre harmonisation T&E

it would be difficult to prove that the cable wasn't installed 10 years ago.

(b) get it signed off at great expense by an electrician
(c) get it signed off at great expense by the local council
(d) use an RF stat

With it buried in plaster, I doubt you'd be able to claim it wasn't
fixed wiring, despite the fact that the whole lot sits off an
FCU/plug+socket. You could always ask your local BCO for their
opinion.

thanks again for your input, I'll print this thread out, pass it to brother in law
and make a descision off the back of /his/ signature, I think.

Christian McArdle wrote:
right, now you're up to speed :-) can you see any problems with the
cable run following the gas pipe in the diagram depicted in my
original post, in relation to the various regulations ?

Well a quick look shows that it is non-viable, as you may not conceal
wiring behind the skirting board unless mechanically protected or
bury it more than 50mm deep.

mechanically protected you say ?

perhaps behind a 22mm gas pipe behind a skirting board which has already been
passed by a BCO ? see where I'm going ? quick, dirty yet within the regs

On Tue, 03 Jan 2006 15:49:36 +0000, Christian McArdle wrote:


You might get away with it ELV (although I'm not entirely sure on this), but
this will require a relay at the boiler if the boiler isn't already ELV on
its thermostat connection.

Christian.

Hi

I'm pretty sure you can do what you like with ELV. Consider HiFi cables
and burglar alarm wiring - stuff goes everywhere. Ditto CAT5 (though I was
naughty and stuffed ISDN down it for a time, and that's not ELV).

Cheers

Tim

On Tue, 03 Jan 2006 14:51:19 +0000, . wrote:

Christian McArdle wrote:
discover I need TRV on ALL the rads rather tham all but one, and
a room stat into the bargain.

You are mistaken.

I'm not, well, I wasn't, it was the brother in law who said /all/ rads need TRVs
and the interweb said all but one. I was firmly with the web on that one but
he disagreed. I thought that having two stats would confuse the boiler.

Your BiL is definately wrong, unless there is some other mechanism to cut
off the boiler when there is no call for heat. The TRVs can't control the
boiler directly unless they are very fancy.

On the subject of the Honeywell RF units, are you aware that they also do
an RF TRV head as a more obscure part of the range?

I've toyed with that idea, makes multiple zoning a doddle (and
reconfigurable). You might get some benefit by replacing the odd TRV in
certain key areas piecemeal over the course of time.

ie if you fitted the RF roomstat and receiver it leaves the possibility to
add more roomstats and TRVs later.



I /must/ have a room stat so the front room will be the rad without the
TRV, the only issue now is the cable run through the kitchen and behind
the skirting. if it is low voltage I shouldn't have a problem with parts
P & L

There might be something about ELV in special locations (kitchen,
bathroom, with telecomms excepted) and part P, but I
wouldn;t worry too much about it (personal opinion). Part L, well, IMO do
what you like. If it ever becomes a "problem" it's not going to be very
expensive to "rectify" it in this case. Your local BCO's probably got more
to worry about than your boiler controls.

HTH

Tim

In article ,
"Christian McArdle" writes:
here's the part P question. how can I run the connecting wire for
the room stat from the boiler to the living room ?

Room stat wiring will usually be low voltage, hence outside scope of Prat
P.

That is not true. Room stat wiring is usually at full mains voltage. Some
combi boilers (but certainly not all) may have low voltage signalling, but
almost all system boiler installations will not be. With a combi, you
certainly can't assume that it is low voltage without investigating the
installation manual.

Also, there is no exemption from Prat P for extra low voltage
wiring (which is I presume what you mean, as mains wiring is
"low voltage").

--
Andrew Gabriel

On Tue, 03 Jan 2006 15:24:21 GMT, a particular chimpanzee named "."
[email protected] randomly hit the keyboard and produced:

thanks for your continuing input, how about the cable run in relation to the regs ?

In relation to Part P; strictly speaking, any electrical work in the
kitchen is controlled. However, if your installer is CORGI
registered, he is exempt from giving notice provided the installation
is, "as a necessary adjunct to or arising out of other work being
carried out by the registered person".

WRT Part L; the installation of a central heating boiler is
controlled, but once again, if the installer is CORGI registered, he
is exempt from giving a notice. The work to replace the boiler would
include for upgrading controls.
--
Hugo Nebula
"If no-one on the internet wants a piece of this,
just how far from the pack have you strayed?"

Tim S wrote:
On Tue, 03 Jan 2006 14:51:19 +0000, . wrote:

Christian McArdle wrote:
discover I need TRV on ALL the rads rather tham all but one, and
a room stat into the bargain.

You are mistaken.

I'm not, well, I wasn't, it was the brother in law who said /all/ rads need TRVs
and the interweb said all but one. I was firmly with the web on that one but
he disagreed. I thought that having two stats would confuse the boiler.

Your BiL is definately wrong, unless there is some other mechanism to cut
off the boiler when there is no call for heat. The TRVs can't control the
boiler directly unless they are very fancy.

On the subject of the Honeywell RF units, are you aware that they also do
an RF TRV head as a more obscure part of the range?

I've toyed with that idea, makes multiple zoning a doddle (and
reconfigurable). You might get some benefit by replacing the odd TRV in
certain key areas piecemeal over the course of time.

ie if you fitted the RF roomstat and receiver it leaves the possibility to
add more roomstats and TRVs later.



I /must/ have a room stat so the front room will be the rad without the
TRV, the only issue now is the cable run through the kitchen and behind
the skirting. if it is low voltage I shouldn't have a problem with parts
P & L

There might be something about ELV in special locations (kitchen,
bathroom, with telecomms excepted) and part P, but I
wouldn;t worry too much about it (personal opinion). Part L, well, IMO do
what you like. If it ever becomes a "problem" it's not going to be very
expensive to "rectify" it in this case. Your local BCO's probably got more
to worry about than your boiler controls.

HTH

Tim

Why not just fit the stat next to the boiler, that complies, no
worrying over cable runs!!

Hugo Nebula wrote:
On Tue, 03 Jan 2006 15:24:21 GMT, a particular chimpanzee named "."
[email protected] randomly hit the keyboard and produced:

thanks for your continuing input, how about the cable run in
relation to the regs ?

In relation to Part P; strictly speaking, any electrical work in the
kitchen is controlled. However, if your installer is CORGI
registered, he is exempt from giving notice provided the installation
is, "as a necessary adjunct to or arising out of other work being
carried out by the registered person".

WRT Part L; the installation of a central heating boiler is
controlled, but once again, if the installer is CORGI registered, he
is exempt from giving a notice. The work to replace the boiler would
include for upgrading controls.

that's just the sort of information I was seeking, thank you.

in relation to the Part P bit, would pulling a single, unbroken, cable /through/
a kitchen be classed as work /in/ the kitchen ?

thanks again.

legin wrote:
Tim S wrote:
On Tue, 03 Jan 2006 14:51:19 +0000, . wrote:

Christian McArdle wrote:
discover I need TRV on ALL the rads rather tham all but one, and
a room stat into the bargain.

You are mistaken.

I'm not, well, I wasn't, it was the brother in law who said /all/
rads need TRVs and the interweb said all but one. I was firmly with
the web on that one but
he disagreed. I thought that having two stats would confuse the
boiler.

Your BiL is definately wrong, unless there is some other mechanism
to cut
off the boiler when there is no call for heat. The TRVs can't
control the
boiler directly unless they are very fancy.

On the subject of the Honeywell RF units, are you aware that they
also do
an RF TRV head as a more obscure part of the range?

I've toyed with that idea, makes multiple zoning a doddle (and
reconfigurable). You might get some benefit by replacing the odd TRV
in
certain key areas piecemeal over the course of time.

ie if you fitted the RF roomstat and receiver it leaves the
possibility to
add more roomstats and TRVs later.



I /must/ have a room stat so the front room will be the rad without
the
TRV, the only issue now is the cable run through the kitchen and
behind
the skirting. if it is low voltage I shouldn't have a problem with
parts
P & L

There might be something about ELV in special locations (kitchen,
bathroom, with telecomms excepted) and part P, but I
wouldn;t worry too much about it (personal opinion). Part L, well,
IMO do
what you like. If it ever becomes a "problem" it's not going to be
very
expensive to "rectify" it in this case. Your local BCO's probably
got more
to worry about than your boiler controls.

HTH

Tim

Why not just fit the stat next to the boiler, that complies, no
worrying over cable runs!!

is what BiL said but I've got the cable from stock and the stat really ought
to be in the living room, soooooo, if I could pull the cable along the route
laid out in my original post, it would be no more difficult than siting the stat
in the utility room. 12m cable and a hand full of clips, I've got a bag of one
coat plaster and some spare capping.......

there's cutting corners and there's bodging. it's a fine line :-)

On 03 Jan 2006 19:00:12 GMT, Andrew Gabriel wrote:

Also, there is no exemption from Prat P for extra low voltage
wiring (which is I presume what you mean, as mains wiring is
"low voltage").

Isn't there? You mean you can't DIY a battery operated doorbell any
more? ISTR a recent thread about this some where that concluded that
stuff like ethernet etc was excluded but phone lines weren't as
ringing was above the voltage levels that defined the Part P cut off.

--
Cheers
Dave. pam is missing e-mail

On Tue, 03 Jan 2006 14:30:54 +0000, Mike Harrison wrote:


here's the part P question. how can I run the connecting wire for the room
stat from the boiler to the living room ?

Room stat wiring will usually be low voltage, hence outside scope of Prat P.

Generally the wiring is at mains voltage.

--
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

"Christian McArdle" wrote in message
...

To have TVRs on all rads one method is
have an auto by-pass valve fitted
between the flow and return. Have a boiler
which can maintain a constant
flow temp. Have a it set to 80C. Balance
the system to 10C across the rads
and boiler, if an existing system. Install
a pipe stat on the boiler
return, so that the burner is off at 71C.

How is interlock achieved?

Via the pipe stat.

You don't have a flow switch in this design.
Explain how the burner never fires if the
outside temp is, say, 30C.

The pump is always on. Lag the return pipe around the pipe stat too.

As it stands, this system will cycle,
as when the water drops below 71C, it
will fire up again even if there is no call for heat.

If the temp drops below 71C the system requires more heat and the pipe stat
brings on the burner. The design is 10C across boiler and rads with 80C
flow temp. If the 10C differential narrows (higher return temp than 71C)
the house has warmed up, so the burner is switched off. An interlock that
detects when the house has reached temperature.

If the TRVs close up and the by-pass valve opens the return temp will rise
above 71C, then the burner will be switched off. The house cools and some
TRVs open and a flow of water goes to the rads dropping the return below
71C, then the burner switches in.

If the design is 70C flow with 22C across the rads and and boiler then set
the pipe stat to 49 or 50C. It then ensures condensing at all times, and no
by-pass returning 75-80C water back through the return and lowering
efficiency, and ensures the flow temp to the rads is low.

In an earlier contribution to this discussion,
Doctor Drivel wrote:


If the temp drops below 71C the system requires more heat and the
pipe stat brings on the burner. The design is 10C across boiler and
rads with 80C flow temp. If the 10C differential narrows (higher
return temp than 71C) the house has warmed up, so the burner is
switched off. An interlock that detects when the house has reached
temperature.
If the TRVs close up and the by-pass valve opens the return temp will
rise above 71C, then the burner will be switched off. The house
cools and some TRVs open and a flow of water goes to the rads
dropping the return below 71C, then the burner switches in.

If the design is 70C flow with 22C across the rads and and boiler
then set the pipe stat to 49 or 50C. It then ensures condensing at
all times, and no by-pass returning 75-80C water back through the
return and lowering efficiency, and ensures the flow temp to the rads
is low.

But as someone else has pointed out, there is a major falicy here - and the
boiler will cycle. As soon as the return *pipe* falls below 71C, the boiler
will fire again. It doesn't require the *house* to cool and a TRV to open.
So it won't satisfy Part L. Or are you suggesting keeping the pump running
all the time? - in which case you'll waste a lot of electrical energy. Even
so, the boiler will still needlessly heat the water to 71C in mid summer!
--
Cheers,
Set Square
______
Please reply to newsgroup. Reply address is invalid.

"Set Square" wrote in message
...
In an earlier contribution to this discussion,
Doctor Drivel wrote:


If the temp drops below 71C the system requires more heat and the
pipe stat brings on the burner. The design is 10C across boiler and
rads with 80C flow temp. If the 10C differential narrows (higher
return temp than 71C) the house has warmed up, so the burner is
switched off. An interlock that detects when the house has reached
temperature.
If the TRVs close up and the by-pass valve opens the return temp will
rise above 71C, then the burner will be switched off. The house
cools and some TRVs open and a flow of water goes to the rads
dropping the return below 71C, then the burner switches in.

If the design is 70C flow with 22C across the rads and and boiler
then set the pipe stat to 49 or 50C. It then ensures condensing at
all times, and no by-pass returning 75-80C water back through the
return and lowering efficiency, and ensures the flow temp to the rads
is low.

the boiler will cycle. As soon as the return *pipe* falls below 71C, the
boiler will fire again. It doesn't require the *house* to cool and a TRV
to open. So it won't satisfy Part L. Or are you suggesting keeping the
pump running all the time?

That is what I said

- in which case you'll waste a lot of electrical energy.

Not much at all. You could have another stat set 3 degrees above to switch
out the pump.

Even so, the boiler will still needlessly heat the water to 71C in mid
summer!

Nope. If the return cools the house has dropped in temp and/or the TVRs
have opened.

In article ws.net,
"Doctor Drivel" writes:
If the temp drops below 71C the system requires more heat and the pipe stat
brings on the burner. The design is 10C across boiler and rads with 80C
flow temp. If the 10C differential narrows (higher return temp than 71C)
the house has warmed up, so the burner is switched off. An interlock that
detects when the house has reached temperature.

If the TRVs close up and the by-pass valve opens the return temp will rise
above 71C, then the burner will be switched off. The house cools and some
TRVs open and a flow of water goes to the rads dropping the return below
71C, then the burner switches in.

If the design is 70C flow with 22C across the rads and and boiler then set
the pipe stat to 49 or 50C. It then ensures condensing at all times, and no
by-pass returning 75-80C water back through the return and lowering
efficiency, and ensures the flow temp to the rads is low.

This fails to comply with Part L.
Such a scheme would need to use a flow switch to
detected all zone valves closed and keep the boiler
off.

--
Andrew Gabriel

"Andrew Gabriel" wrote in message
.. .
In article ws.net,
"Doctor Drivel" writes:
If the temp drops below 71C the system requires more heat and the pipe
stat
brings on the burner. The design is 10C across boiler and rads with 80C
flow temp. If the 10C differential narrows (higher return temp than 71C)
the house has warmed up, so the burner is switched off. An interlock
that
detects when the house has reached temperature.

If the TRVs close up and the by-pass valve opens the return temp will
rise
above 71C, then the burner will be switched off. The house cools and
some
TRVs open and a flow of water goes to the rads dropping the return below
71C, then the burner switches in.

If the design is 70C flow with 22C across the rads and and boiler then
set
the pipe stat to 49 or 50C. It then ensures condensing at all times, and
no
by-pass returning 75-80C water back through the return and lowering
efficiency, and ensures the flow temp to the rads is low.

This fails to comply with Part L.
Such a scheme would need to use a flow switch to
detected all zone valves closed and keep the boiler
off.

Part L says an 'interlock'.

In article ews.net,
"Doctor Drivel" writes:

"Andrew Gabriel" wrote in message
.. .
In article ws.net,
"Doctor Drivel" writes:
If the temp drops below 71C the system requires more heat and the pipe
stat
brings on the burner. The design is 10C across boiler and rads with 80C
flow temp. If the 10C differential narrows (higher return temp than 71C)
the house has warmed up, so the burner is switched off. An interlock
that
detects when the house has reached temperature.

If the TRVs close up and the by-pass valve opens the return temp will
rise
above 71C, then the burner will be switched off. The house cools and
some
TRVs open and a flow of water goes to the rads dropping the return below
71C, then the burner switches in.

If the design is 70C flow with 22C across the rads and and boiler then
set
the pipe stat to 49 or 50C. It then ensures condensing at all times, and
no
by-pass returning 75-80C water back through the return and lowering
efficiency, and ensures the flow temp to the rads is low.

This fails to comply with Part L.
Such a scheme would need to use a flow switch to
detected all zone valves closed and keep the boiler
off.

Part L says an 'interlock'.

Which is precisely the bit you're missing.

Your scheme keeps the boiler and bypass loop maintained at
80C when no heat is required. Part L requires the boiler to
be switched off when no heat is required. This is to avoid
the energy wasted in keeping the boiler and pipework up to
temperature when there's no demand for heat.

--
Andrew Gabriel

In message , .
writes
Christian McArdle wrote:
right, now you're up to speed :-) can you see any problems with the
cable run following the gas pipe in the diagram depicted in my
original post, in relation to the various regulations ?

Well a quick look shows that it is non-viable, as you may not conceal
wiring behind the skirting board unless mechanically protected or
bury it more than 50mm deep.

mechanically protected you say ?

perhaps behind a 22mm gas pipe behind


a skirting board which has already been
passed by a BCO ? see where I'm going ? quick, dirty yet within the regs

No that wouldn't be mechanically protected - it needs to be in steel
conduit, or covered with suitable steel plate
--
Chris French

On Wed, 04 Jan 2006 01:05:54 +0000, chris French wrote:

In message , .
writes
Christian McArdle wrote:
right, now you're up to speed :-) can you see any problems with the
cable run following the gas pipe in the diagram depicted in my
original post, in relation to the various regulations ?

Well a quick look shows that it is non-viable, as you may not conceal
wiring behind the skirting board unless mechanically protected or
bury it more than 50mm deep.

mechanically protected you say ?

perhaps behind a 22mm gas pipe behind


a skirting board which has already been
passed by a BCO ? see where I'm going ? quick, dirty yet within the regs

No that wouldn't be mechanically protected - it needs to be in steel
conduit, or covered with suitable steel plate

Having just conferred with someone on the IEE forums, there is another
option, which is to use a cable with an earthed screen designed to provide
protection in the event of being punctured by a conductive object.

Specific cables which are quoted as OK to run outside of the permitted
zones are Lapp XL-Shield and FP200.

XL-Shield is interesting stuff - earth core which remains in contact
with a foil screen along the entire length of the cable. No special
termination techniques or fittings needed. Details he

http://www.lapplimited.co.uk/product...fixedcable.htm

FP200 is more common, though, being used in fire systems. I'm not sure if
it required special termination.

Both types are fiendishly expensive (1-1.50 per metre), friendly trade
counter might sell it cut.

HTH

Tim

Nope. If the return cools the house has dropped in temp and/or the TVRs
have opened.

********.

Say the outside temperature is 30C. The rads require no heat, therefore the
return temp drops below 71C. What prevents the boiler firing?

The answer is nothing. The boiler will fire. It will heat the primary
circuit, wasting energy and it WILL NOT comply with Part L1.

There is nothing in your scheme that prevents the boiler firing if the house
is hot. OK, there is something to stop the boiler firing if the house is hot
AND the system is already running. However, if the system has stopped and
cooled down, then it will restart, cycling forever, despite there being no
call for heat at all.

Christian.

Tim S wrote:
On Wed, 04 Jan 2006 01:05:54 +0000, chris French wrote:

In message , .
writes
Christian McArdle wrote:
right, now you're up to speed :-) can you see any problems with
the cable run following the gas pipe in the diagram depicted in my
original post, in relation to the various regulations ?

Well a quick look shows that it is non-viable, as you may not
conceal wiring behind the skirting board unless mechanically
protected or
bury it more than 50mm deep.

mechanically protected you say ?

perhaps behind a 22mm gas pipe behind


a skirting board which has already been
passed by a BCO ? see where I'm going ? quick, dirty yet within the
regs

No that wouldn't be mechanically protected - it needs to be in steel
conduit, or covered with suitable steel plate

Having just conferred with someone on the IEE forums, there is another
option, which is to use a cable with an earthed screen designed to
provide protection in the event of being punctured by a conductive
object.

Specific cables which are quoted as OK to run outside of the permitted
zones are Lapp XL-Shield and FP200.

XL-Shield is interesting stuff - earth core which remains in contact
with a foil screen along the entire length of the cable. No special
termination techniques or fittings needed. Details he

http://www.lapplimited.co.uk/product...fixedcable.htm

FP200 is more common, though, being used in fire systems. I'm not
sure if it required special termination.

Both types are fiendishly expensive (1-1.50 per metre), friendly trade
counter might sell it cut.

HTH

Tim

Outstanding example of the glory of usenet !

many thanks Tim