I have an existing 22mm gas pipe run, currently serving an old (multipoint?)
on-demand water heater. I'm looking to install a new CH boiler, and would
like to estimate the max boiler (KW/BTU) that can go onto the end of this
run without incurring the (not insignificant nowadays) Corgi cost of
upgradiung this pipe.

a) The 22mm pipe is about 10m long, runs along outside walls but has 8 x
90degr bends along the run. Nothing else braches off it, just the old boiler
at the end. I wouldn't know the pressure at the meter. Can this be
calculated?

b) Alternatively, the existing on-demand water heater is a 'Main. Medway
(automatic)' . It's about 420 x 750 and was in the house when I moved in
(1988) and would guess it's early or mid 1980's. It has a distinctive
winter/summer knob in the bottom right hand corner. I'm guessing it might be
20KW but don't really know - if you have one of these, and/or know what the
power rating is please let me know!.

Thanks,

DIYSOS

PS - hope a) doesn't prove to be smaller than b) !!!

a) The 22mm pipe is about 10m long, runs along outside walls but has 8 x
90degr bends along the run. Nothing else braches off it, just the old
boiler
at the end. I wouldn't know the pressure at the meter. Can this be
calculated?

Sorry I mean can the pipe carrying capacity be calculated - not pressure at
meter.

In message , DIYSOS
wrote
I have an existing 22mm gas pipe run, currently serving an old (multipoint?)
on-demand water heater. I'm looking to install a new CH boiler, and would
like to estimate the max boiler (KW/BTU) that can go onto the end of this
run without incurring the (not insignificant nowadays) Corgi cost of
upgradiung this pipe.

a) The 22mm pipe is about 10m long, runs along outside walls but has 8 x
90degr bends along the run. Nothing else braches off it, just the old boiler
at the end. I wouldn't know the pressure at the meter. Can this be
calculated?

The following link may help
http://www.cda.org.uk/megab2/build/pub124/sec3.htm#4.3



--
Alan

DIYSOS wrote:
I have an existing 22mm gas pipe run, currently serving an old (multipoint?)
on-demand water heater. I'm looking to install a new CH boiler, and would
like to estimate the max boiler (KW/BTU) that can go onto the end of this
run without incurring the (not insignificant nowadays) Corgi cost of
upgradiung this pipe.

a) The 22mm pipe is about 10m long, runs along outside walls but has 8 x
90degr bends along the run. Nothing else braches off it, just the old boiler
at the end. I wouldn't know the pressure at the meter. Can this be
calculated?

Each 90 deg bend is equiv to 0.5 metre pipe length so you've got 14m
equiv in all. I'm not looking up the tables and charts (you don't get
everything for free :-) but off the top of my head you start getting
into trouble with a 28kW appliance at about 20m of 22mm pipework, so 14m
should be OK for similar. If you need 35kW maybe you should be thinking
of more insulation, alternatively you have such a big and expensive
house you can affort to pay someone to work it out for you :-)


b) Alternatively, the existing on-demand water heater is a 'Main. Medway
(automatic)' . It's about 420 x 750 and was in the house when I moved in
(1988) and would guess it's early or mid 1980's. It has a distinctive
winter/summer knob in the bottom right hand corner. I'm guessing it might be
20KW but don't really know - if you have one of these, and/or know what the
power rating is please let me know!.

Thanks,

DIYSOS

PS - hope a) doesn't prove to be smaller than b) !!!

I don't know the rating of the water heater but it sounds as if the
pipework was generously specced for it.

Many thanks for the helpful replies.

OT, now this probably can't happen but...

I seem to be staring at 2.5k to 3k to fit a new central heating boiler for a
DIY CH system.

So, I'm amused by the concept of re-using the existing GWH to power a
thermal store. IE take it off the mains water supply, and re-plumb into a
primary water loop with thermostat and pump feeding the store. The 'stat
starts the pump and the flow fires up the boiler - in theory!. Space heating
and DHW taken off the store as usual. No new boiler and better still no
Corgi - cost virtually nothing!.

Like I say, for various reasons this probably can't happen, it might even be
dangerous (so don't try this at home, OK?) though I can't think why unless
water runs out?. And the boiler would be working for hours on end, not just
20 mins a day... and I know it's probably SEDBUK Z. But I can dream!.

Cheers,

DIYSOS

.... of course I'm 3 years too late anyway, being SEDBUK 'Z' boiler would
fall foul of Part L anyway.

Anyway I digress... thanks again for the earlier replies.

DIYSOS

I'd allow for a few sockets also and say 15m of pipe which gives you 3.3 m cubed per hour. The calorific value of natural gas is 10.76 so you can use a 35.5 kw appliance on the end of this pipe run.

"DIYSOS" wrote in message
...
Many thanks for the helpful replies.

OT, now this probably can't happen but...

I seem to be staring at 2.5k to 3k to fit a new central heating boiler for
a
DIY CH system.

So, I'm amused by the concept of re-using the existing GWH to power a
thermal store. IE take it off the mains water supply, and re-plumb into a
primary water loop with thermostat and pump feeding the store. The 'stat
starts the pump and the flow fires up the boiler - in theory!. Space
heating
and DHW taken off the store as usual. No new boiler and better still no
Corgi - cost virtually nothing!.

Like I say, for various reasons this probably can't happen, it might even
be
dangerous (so don't try this at home, OK?) though I can't think why unless
water runs out?. And the boiler would be working for hours on end, not
just
20 mins a day... and I know it's probably SEDBUK Z. But I can dream!.

It is not dangerous at all, it will work. This sort of thing is common in
the USA. Chaffotaux made an boiler with multi-point controls about 20-25
years ago. The pump pressure opened a water valve.

Boilers are so cheap these days it is probably not worth it.




_________________________________________
Usenet Zone Free Binaries Usenet Server
More than 120,000 groups
Unlimited download
http://www.usenetzone.com to open account

In article ,
John Stumbles writes:

I don't know the rating of the water heater but it sounds as if the
pipework was generously specced for it.

The Main range are all around 30kW input
(different models varied by a couple of kW).
I've got the spec of the Main Medway hidden
somewhere if someone wants the exact figure.

--
Andrew Gabriel

In article ,
"DIYSOS" writes:
Many thanks for the helpful replies.

OT, now this probably can't happen but...

I seem to be staring at 2.5k to 3k to fit a new central heating boiler for a
DIY CH system.

So, I'm amused by the concept of re-using the existing GWH to power a
thermal store. IE take it off the mains water supply, and re-plumb into a
primary water loop with thermostat and pump feeding the store. The 'stat
starts the pump and the flow fires up the boiler - in theory!. Space heating
and DHW taken off the store as usual. No new boiler and better still no
Corgi - cost virtually nothing!.

Like I say, for various reasons this probably can't happen, it might even be
dangerous (so don't try this at home, OK?) though I can't think why unless
water runs out?. And the boiler would be working for hours on end, not just
20 mins a day... and I know it's probably SEDBUK Z. But I can dream!.

Mine measures at 77.2% efficient, which makes it SEDBUK E
(actually, only 0.8% off from SEDBUK D -- would probably
get there with some fine tuning).

Unlike a conventional stored water system, there are no
losses from a cylinder or primary circuit, so you would
need to adjust this upwards to compare overall system
efficiency with that of a conventional boiler and stored
water system.

--
Andrew Gabriel

Wow 30KW!. And that applies to my 1980's model. Makes wonder why my shower
isn't warmer - I've a vague suspicion limescale has built up over the years
and never been removed during servicing, but I can't be sure.

DIYSOS

Boilers may be 'cheap' but putting one in certainly isn't (:-) - unless you
DIY it, of course.

So this idea actually seems doable and the boiler efficiency is almost
acceptable then (before April at least). So near and yet so far - I'm almost
glad it's hopelessly situated in a bedroom wardrobe to make me feel better
about not trying it out.

DIYSOS.

In article ,
"DIYSOS" writes:
Wow 30KW!. And that applies to my 1980's model. Makes wonder why my shower
isn't warmer - I've a vague suspicion limescale has built up over the years
and never been removed during servicing, but I can't be sure.

I used to take the heat exchanger out occasionally, stand it
upside down in an old plastic bath, and pour descaller through
it until it stopped fizzing. Made an enormous difference to
the performance. This was a 1978 Main Medina, which had no
thermostatic control. It was too powerful for a shower (choice
of being burned, or having the water jets drilling holes through
you), and you couldn't turn it down. I replaced the whole thing
in 2000; see http://www.diyfaq.org.uk/humour.html#uninstalling
The replacement unit has thermostatic control, better modulation
control, and has internal teflon coated pipework which hasn't
scaled up since.

--
Andrew Gabriel

......sssnnnniippp
So this idea actually seems doable and the boiler efficiency is almost
acceptable then (before April at least). So near and yet so far.....
ssnniipppp

What's happening in April ?? are we all going condensing or something ??

Nick

"DIYSOS" wrote in message
...
Boilers may be 'cheap' but putting one in certainly isn't (:-) - unless
you
DIY it, of course.

So this idea actually seems doable and the boiler efficiency is almost
acceptable then (before April at least). So near and yet so far - I'm
almost
glad it's hopelessly situated in a bedroom wardrobe to make me feel better
about not trying it out.

Having an existing multi-point heat a thermal store is no problem, even
after April. It is already there. It is not a replacement or a new
installation.


_________________________________________
Usenet Zone Free Binaries Usenet Server
More than 120,000 groups
Unlimited download
http://www.usenetzone.com to open account

Having an existing multi-point heat a thermal store is no problem, even
after April. It is already there. It is not a replacement or a new
installation.

I did wonder about this, the boiler installation is indeed not new (in fact
it's very old!) but the change of use is very radical!.

What's happening in April ?? are we all going condensing or something ??

Indeed we are.

DIYSOS

"DIYSOS" wrote in message
news
Having an existing multi-point heat a thermal store is no problem, even
after April. It is already there. It is not a replacement or a new
installation.

I did wonder about this, the boiler installation is indeed not new (in
fact
it's very old!) but the change of use is very radical!.

It's not radical, it is heating water by gas, just as it always has done.

What's happening in April ?? are we
all going condensing or something ??

Indeed we are.

DIYSOS



_________________________________________
Usenet Zone Free Binaries Usenet Server
More than 120,000 groups
Unlimited download
http://www.usenetzone.com to open account

It's not radical, it is heating water by gas, just as it always has done.

Very true... but what about this boiler interlocking... how to connect
'roomstat' to the boiler... would it *really* be every bit a safe as a
modern boiler if used this way - and readily seen as such should I sell
up... ie would the new setup 'pass' CORGI inspection... how long would this
boiler last if used flat-out for hours on end instead of 10 mins a day
(probably longer than a modern one!), what about running costs and the
planet... and as it's a new CH system with no Corgi involved, am I supposed
to raise a Building Notice?.

These are some of the unanswered questions in my mind that may or may not be
valid, but fortunately I don't have to addrtess them - yet!. The boiler is
in a bedroom where my thermal store (or HW tank) would probably need to go,
so I'm unlikely to proceed anyway - until I find out how much the new boiler
installation will be, of course!.

As my old boiler was really an OT subject, and my original question about
the gas supply have been comprehensively answered, I plan to bid this thread
farewell - so thanks all for your input.

DIYSOS

"DIYSOS" wrote in message
...

It's not radical, it is heating water
by gas, just as it always has done.

Very true... but what about this boiler
interlocking... how to connect
'roomstat' to the boiler...

As you have a heat bank between the boiler and the rads the boiler is not
connected to the rads. The boiler operates not even knowing the rads are
there just heating the water mass. The cylinder stats act as the interlock.

would it *really* be every bit a safe as a
modern boiler if used this way - and readily
seen as such should I sell up... ie would the
new setup 'pass' CORGI inspection... how
long would this boiler last if used flat-out for
hours on end instead of 10 mins a day
(probably longer than a modern one!),

Corgi is interested in the gas safety side. A multi-point connected to a
thermal store has an interlock via the cylinder stat. The stat controls the
pump. The pump is on the return to the multi-point and opens the gas valve
via pressure.

Does the multi-point have a thermostat?

what about running costs and the
planet...

A modern boiler will be far cheaper to run.

and as it's a new CH system with no
Corgi involved, am I supposed
to raise a Building Notice?.

Not that I an aware of. Others may know better.

These are some of the unanswered
questions in my mind that may or may not be
valid, but fortunately I don't have to addrtess
them - yet!. The boiler is in a bedroom
where my thermal store (or HW tank) would
probably need to go, so I'm unlikely to proceed
anyway - until I find out how much the new boiler
installation will be, of course!.

As my old boiler was really an OT subject,
and my original question about
the gas supply have been comprehensively
answered, I plan to bid this thread
farewell - so thanks all for your input.



_________________________________________
Usenet Zone Free Binaries Usenet Server
More than 120,000 groups
Unlimited download
http://www.usenetzone.com to open account

Does the multi-point have a thermostat?

I think so, though as it seems to be heading for the skip I doubt this will
count for much...

Just as a postscript, I eventually located documentation for this boiler on
Baxi Partsarena.com as follows:

Go to baxi/partsareana website... then go Main... goWater heaters... go
Medway... go Basic later production... go Installation instructions... go
Mersey, Medway automatic & Trent... and there it is!.

Heat input 30.27KW, heat output 22.7KW, raises 12.5L/min by 25C. Minimum
operating head if connected to static tank 2.29M, max pressure 13 bar. Also
interesting servicing stuff like how to descale and tweak burner fire up
times. Shame this document wasn't waiting by the gas meter for me when I
moved in many years ago...

DIYSOS

.... Incidentally I should mention that it doesn't in fact have a thermostat.