Hello all,

I need to reboiler my place.
The boiler is at least 45 years old and obviously cannot last forever.
I am somewhat older and the same conditions apply.

The supply to existing boiler is 1/2" steel pipe.
I'm told that I need to have a 22mm supply for a new condensing boiler.
The routing of existing pipework cannot be followed without demolishing
about half of the interior of the house. I'm not willing to do that.

Would it be legal to run the majority of the pipework in armoured
rubber/flexible pipe?

The last metre or two at each end would be in metal tubing. All above
ground at high level (2M) and nothing external to the house.

I would appreciate your views.

Many thanks,
Nick.

On 02/03/2021 23:28, Nick wrote:
Hello all,

I need to reboiler my place.
The boiler is at least 45 years old and obviously cannot last forever.
I am somewhat older and the same conditions apply.

The supply to existing boiler is 1/2" steel pipe.
I'm told that I need to have a 22mm supply for a new condensing boiler.
The routing of existing pipework cannot be followed without demolishing
about half of the interior of the house. I'm not willing to do that.

Would it be legal to run the majority of the pipework in armoured
rubber/flexible pipe?

The last metre or two at each end would be in metal tubing. All above
ground at high level (2M) and nothing external to the house.

I would appreciate your views.

Many thanks,
Nick.

It is a great shame that the website
http://wiki.diyfaq.org.uk
is still down as it includes pressure drop calculations of pipe runs.

If you know the kW of your boiler you would be able to calculate the
size of pipe you actually need. In domestic situations with limited pipe
runs 22mm copper pipe is a safe bet, plus to save embarrassment to Gas
Safe installer Gas Safe have made a blanket requirement to combis where
they must be piped in 22mm. Though I would be happy to have the last
sectionin 15mm.

There is no need for any mechanical protection. The only exception is
using a sheath is through a wall, to ensure that no gas can leak into a
cavity and to stop the chemical effect of mortar. Usually a larger sized
PVC pipe.

Depending on the pipe runs and if the existing pipe is gas tight then
this may be reused. When you say 1/2" steel pipe this normally
corresponds to an internal diameter of 18.6mm if 1/2" BSP.
https://en.wikipedia.org/wiki/British_Standard_Pipe

I believe it is generally said they should not be run in voids. So
behind kitchen units is fine, as is outside. Under floorboards is also
considered a ventilated space.

BICBW

Nick wrote:
Hello all,

I need to reboiler my place.
The boiler is at least 45 years old and obviously cannot last forever.
I am somewhat older and the same conditions apply.

The supply to existing boiler is 1/2" steel pipe.
I'm told that I need to have a 22mm supply for a new condensing boiler.
The routing of existing pipework cannot be followed without demolishing
about half of the interior of the house. I'm not willing to do that.

Would it be legal to run the majority of the pipework in armoured
rubber/flexible pipe?

Im not an expert but I doubt it very much!

Things to consider, if your boiler is on an outside wall, the pipe could be
routed externally. Not pretty but would avoid internal disruption.

If your boiler *isnt* on an outside wall then its probably discharging
into a chimney. This will be hard to do with a new boiler (as the flue
must be accessible for inspection). Consequently you may be looking at
boiler relocation and replumbing.

Tim
--
Please don't feed the trolls

Nick wrote:

The supply to existing boiler is 1/2" steel pipe. I'm told
by who?

that I need to have a 22mm supply for a new condensing boiler.

It might be true, or it might be a lazy installer not wanting to do the
sums ... British Gas tried that trick when my father had a new boiler
fitted, it didn't wash with my Dad who used to work for British Gas* and
did the sums for them!

Would it be legal to run the majority of the pipework in armoured
rubber/flexible pipe?

Rubber no, but you could suggest corrugated stainless steel tracpipe
[*] misplaced loyalty means he still expects them to be "good".

On Tuesday, 2 March 2021 at 23:28:29 UTC, Nick wrote:
Hello all,

I need to reboiler my place.
The boiler is at least 45 years old and obviously cannot last forever.
I am somewhat older and the same conditions apply.

The supply to existing boiler is 1/2" steel pipe.
I'm told that I need to have a 22mm supply for a new condensing boiler.
The routing of existing pipework cannot be followed without demolishing
about half of the interior of the house. I'm not willing to do that.

Would it be legal to run the majority of the pipework in armoured
rubber/flexible pipe?

The last metre or two at each end would be in metal tubing. All above
ground at high level (2M) and nothing external to the house.

I would appreciate your views.

Many thanks,
Nick.
I'd say no f***ing way - could you expect rubber hose to be gastight in a fire! You really need to determine the actual gas rate of your proposed CONDENSING (not combi) boiler to discover if the steel pipe is adequate[y sized for the job. It might help if you ask someone who knows what they are doing to measure the current boilers gas rate and the pressure drop from meter to boiler under load. This would give you a good idea of the feasibility of reuse. Don't forget steel pipe corroded so it would also be sensible to do a soundness check while he/she is there. I've seen installations in steel pipe where permitted drop increased year on year until it eventually exceeded that allowable. Then it was a case of having to sort it and rerun the pipe in copper.

On 02/03/2021 23:57, Fredxx wrote:

snip

If you know the kW of your boiler you would be able to calculate the
size of pipe you actually need. In domestic situations with limited pipe
runs 22mm copper pipe is a safe bet, plus to save embarrassment to Gas
Safe installer Gas Safe have made a blanket requirement to combis where
they must be piped in 22mm. Though I would be happy to have the last
sectionin 15mm.


I don't want to give false hope to the OP who may well need a new gas pipe.

But I've seen before on some sites that "Gas Safe regulations now state
that gas supply pipes from the meter to a combi boiler must be at least
22mm". Smelt to me like a way to get more work and avoid the bother of
calculating pressure drops. Gas Safe have no power to make regulations.
And while the Gas Safety (Installation and Use) Regulations were
amended in 2018 I can't see anything in them about a minimum pipe size.
Have I missed something?


--
Robin
reply-to address is (intended to be) valid

On 03/03/2021 09:36, Robin wrote:
On 02/03/2021 23:57, Fredxx wrote:

snip

If you know the kW of your boiler you would be able to calculate the
size of pipe you actually need. In domestic situations with limited
pipe runs 22mm copper pipe is a safe bet, plus to save embarrassment
to Gas Safe installer Gas Safe have made a blanket requirement to
combis where they must be piped in 22mm. Though I would be happy to
have the last sectionin 15mm.


I don't want to give false hope to the OP who may well need a new gas pipe.

But I've seen before on some sites that "Gas Safe regulations now state
that gas supply pipes from the meter to a combi boiler must be at least
22mm". Smelt to me like a way to get more work and avoid the bother of
calculating pressure drops.Â* Gas Safe have no power to make regulations.
Â*And while the Gas Safety (Installation and Use) Regulations were
amended in 2018 I can't see anything in them about a minimum pipe size.
Have I missed something?


When our old gas boiler was replaced at our last house the engineer said
he would have to take up the parquet flooring right through the length
of our hall to install a new pipe. We objected telling him to find
another route.

He then agreed to test the gas flow through the old pipe and guess what?
Yes it was more than adequate to feed the new boiler.

Mike

Nick expressed precisely :
The supply to existing boiler is 1/2" steel pipe.
I'm told that I need to have a 22mm supply for a new condensing boiler.

Did you mean a new 'COMBI' boiler to replace a heat only?

Combi boiler usually need a larger supply pipe, heat only tend to be OK
on the existing, especially if the central heating demand has been
reduced over the years, with extra insulation.

Muddymike wrote on 03/03/2021 :
When our old gas boiler was replaced at our last house the engineer said he
would have to take up the parquet flooring right through the length of our
hall to install a new pipe. We objected telling him to find another route.

He then agreed to test the gas flow through the old pipe and guess what?
Yes it was more than adequate to feed the new boiler.

We had the very same situation, except the guy wanted to charge us to
run an ugly pipe all the way around the outside of the house. I did the
calcs for him and proved him wrong/ unecessary.

On Wed, 03 Mar 2021 09:42:44 +0000, Muddymike wrote:

When our old gas boiler was replaced at our last house the engineer said
he would have to take up the parquet flooring right through the length
of our hall to install a new pipe. We objected telling him to find
another route.

He then agreed to test the gas flow through the old pipe and guess what?
Yes it was more than adequate to feed the new boiler.

Our guy (who we have used for years and trust) said he was a bit worried
about the flow rate. He measured and calculated, then found that a small
part of the run was in 15mm pipe. The rest was in steel pipe.

He changed the 15mm part (which was not disruptive) and it's all fine.



--
My posts are my copyright and if @diy_forums or Home Owners' Hub
wish to copy them they can pay me £1 a message.
Use the BIG mirror service in the UK: http://www.mirrorservice.org
*lightning surge protection* - a w_tom conductor

In article , Robin
writes
On 02/03/2021 23:57, Fredxx wrote:

snip
If you know the kW of your boiler you would be able to calculate the
size of pipe you actually need. In domestic situations with limited
pipe runs 22mm copper pipe is a safe bet, plus to save embarrassment
to Gas Safe installer Gas Safe have made a blanket requirement to
combis where they must be piped in 22mm. Though I would be happy to
have the last sectionin 15mm.


I don't want to give false hope to the OP who may well need a new gas pipe.

But I've seen before on some sites that "Gas Safe regulations now state
that gas supply pipes from the meter to a combi boiler must be at least
22mm". Smelt to me like a way to get more work and avoid the bother of
calculating pressure drops. Gas Safe have no power to make
regulations. And while the Gas Safety (Installation and Use)
Regulations were amended in 2018 I can't see anything in them about a
minimum pipe size. Have I missed something?


Only that when combi boilers first appeared a lot of installers used the
existing 15mm which was then found to be inadequate.
--
bert

On 03/03/2021 10:24, Bob Eager wrote:
On Wed, 03 Mar 2021 09:42:44 +0000, Muddymike wrote:

When our old gas boiler was replaced at our last house the engineer said
he would have to take up the parquet flooring right through the length
of our hall to install a new pipe. We objected telling him to find
another route.

He then agreed to test the gas flow through the old pipe and guess what?
Yes it was more than adequate to feed the new boiler.

Our guy (who we have used for years and trust) said he was a bit worried
about the flow rate. He measured and calculated, then found that a small
part of the run was in 15mm pipe. The rest was in steel pipe.

He changed the 15mm part (which was not disruptive) and it's all fine.



Surely the actual connection at the boiler is always 15mm, and
the installation instructions that I have seen say that the last metre
or so can be 15mm pipework.

Just because the OP can see 15mm ?iron pipe does not mean it is
15mm all the way from the meter. What size of pipe exits the meter ?.

On 03/03/2021 07:31, Tim+ wrote:
Nick wrote:
Hello all,

I need to reboiler my place.
The boiler is at least 45 years old and obviously cannot last forever.
I am somewhat older and the same conditions apply.

The supply to existing boiler is 1/2" steel pipe.
I'm told that I need to have a 22mm supply for a new condensing boiler.
The routing of existing pipework cannot be followed without demolishing
about half of the interior of the house. I'm not willing to do that.

Would it be legal to run the majority of the pipework in armoured
rubber/flexible pipe?

Im not an expert but I doubt it very much!


There is something called tracpipe?? which is flexible stainless
steel pipe intended for gas, which has fittings at each end to
join up with existing pipework. This could? be wangled through
the ceiling void if needed.

On 03/03/2021 11:22, bert wrote:
In article , Robin
writes
On 02/03/2021 23:57, Fredxx wrote:

snip
Â*If you know the kW of your boiler you would be able to calculate the
size of pipe you actually need. In domestic situations with limited
pipeÂ* runs 22mm copper pipe is a safe bet, plus to save embarrassment
to GasÂ* Safe installer Gas Safe have made a blanket requirement to
combis whereÂ* they must be piped in 22mm. Though I would be happy to
have the lastÂ* sectionin 15mm.


I don't want to give false hope to the OP who may well need a new gas
pipe.

But I've seen before on some sites that "Gas Safe regulations now
state that gas supply pipes from the meter to a combi boiler must be
at least 22mm". Smelt to me like a way to get more work and avoid the
bother of calculating pressure drops.Â* Gas Safe have no power to make
regulations.Â* And while the Gas Safety (Installation and Use)
Regulations were amended in 2018 I can't see anything in them about a
minimum pipe size. Have I missed something?


Only that when combi boilers first appeared a lot of installers used the
existing 15mm which was then found to be inadequate.

Thanks but I was aware of that. And it's a bit of a leap from that to
"you *must* use 22mm even if it's a run of 1.5m with one bend to a 24 kW
combi". Only makes sense to me if Gas Safe members can no longer be
trusted to do sums and measure pressure drops at existing boiler.

--
Robin
reply-to address is (intended to be) valid

On 02/03/2021 23:28, Nick wrote:

Hello all,

I need to reboiler my place.
The boiler is at least 45 years old and obviously cannot last forever.
I am somewhat older and the same conditions apply.

The supply to existing boiler is 1/2" steel pipe.
I'm told that I need to have a 22mm supply for a new condensing boiler.

That may or may not be true - it depends on the power of the boiler, and
the length of the pipe run. Although beware many gas fitters seem
reluctant to actually do sums, and just go for rule of thumb answers!

(whether it is condensing or not has no bearing)

You would need to do a calculation on the size of pipe required. The
process is described in the wiy wiki, but that is offline at the moment.
However watch this space - it should be back soon.

Alternatively if you have access to BS 6891:2005 "Installation of low
pressure gas pipework of up to 35 mm (R1 1/4 in) domestic premises
(2nd family gas) €”Specification", that also describes the process.

I have put s short extract from that he

http://diyfaq.org.uk/docs/GasPipeSize.pdf

that covers the basics.

You also need to know the gas rate for the boiler - you can get that by
multiplying it power in kW by 0.09, and that will get an approximate
figure in m^3/hour.

So a 24kW boiler would be around 2.16 m^3 / hour - allow a bit for

A 15mm / 1/2" pipe can shift that within the 1mBar allowable drop for
about 5m maximum. (and that is effective length where elbows count as
0.5m of pipe, bends as 0.3m)


The routing of existing pipework cannot be followed without demolishing
about half of the interior of the house. I'm not willing to do that.

Would it be legal to run the majority of the pipework in armoured
rubber/flexible pipe?

No - although that does depend a bit on what you mean by flexible pipe.
While the normal flexible pipe used for say a cooker connection would
not be acceptable, products like Trackpipe (a stainless corrugated
plastic coated bendable gas pipe) are ok.

The last metre or two at each end would be in metal tubing. All above
ground at high level (2M) and nothing external to the house.

You can run normal copper externally, clipped to a wall. That is a
common solution to this kind of problem.



--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On 03/03/2021 11:22, bert wrote:
In article , Robin
writes
On 02/03/2021 23:57, Fredxx wrote:

snip
Â*If you know the kW of your boiler you would be able to calculate the
size of pipe you actually need. In domestic situations with limited
pipeÂ* runs 22mm copper pipe is a safe bet, plus to save embarrassment
to GasÂ* Safe installer Gas Safe have made a blanket requirement to
combis whereÂ* they must be piped in 22mm. Though I would be happy to
have the lastÂ* sectionin 15mm.


I don't want to give false hope to the OP who may well need a new gas
pipe.

But I've seen before on some sites that "Gas Safe regulations now
state that gas supply pipes from the meter to a combi boiler must be
at least 22mm". Smelt to me like a way to get more work and avoid the
bother of calculating pressure drops.Â* Gas Safe have no power to make
regulations.Â* And while the Gas Safety (Installation and Use)
Regulations were amended in 2018 I can't see anything in them about a
minimum pipe size. Have I missed something?


Only that when combi boilers first appeared a lot of installers used the
existing 15mm which was then found to be inadequate.

Yet another reason why combis are ****.

My peak hot water requirements are easily met with a mains pressure
cylinder allowing me to use a mere 12kw boiler.
You need around 50kW to get a decent hot water supply.




--
If you tell a lie big enough and keep repeating it, people will
eventually come to believe it. The lie can be maintained only for such
time as the State can shield the people from the political, economic
and/or military consequences of the lie. It thus becomes vitally
important for the State to use all of its powers to repress dissent, for
the truth is the mortal enemy of the lie, and thus by extension, the
truth is the greatest enemy of the State.

Joseph Goebbels

On 02/03/2021 23:57, Fredxx wrote:
On 02/03/2021 23:28, Nick wrote:
Hello all,

I need to reboiler my place.
The boiler is at least 45 years old and obviously cannot last forever.
I am somewhat older and the same conditions apply.

The supply to existing boiler is 1/2" steel pipe.
I'm told that I need to have a 22mm supply for a new condensing boiler.
The routing of existing pipework cannot be followed without
demolishing about half of the interior of the house. I'm not willing
to do that.

Would it be legal to run the majority of the pipework in armoured
rubber/flexible pipe?

The last metre or two at each end would be in metal tubing. All above
ground at high level (2M) and nothing external to the house.

I would appreciate your views.

Many thanks,
Nick.

It is a great shame that the website
Â* http://wiki.diyfaq.org.uk
is still down as it includes pressure drop calculations of pipe runs.


Accessible of sorts through the wayback machine (the search won't work)

https://web.archive.org/web/20200217...heating_design




--
Adrian C

In message , Andrew
writes
On 03/03/2021 07:31, Tim+ wrote:
Nick wrote:
Hello all,

I need to reboiler my place.
The boiler is at least 45 years old and obviously cannot last forever.
I am somewhat older and the same conditions apply.

The supply to existing boiler is 1/2" steel pipe.
I'm told that I need to have a 22mm supply for a new condensing boiler.
The routing of existing pipework cannot be followed without demolishing
about half of the interior of the house. I'm not willing to do that.

Would it be legal to run the majority of the pipework in armoured
rubber/flexible pipe?
Im not an expert but I doubt it very much!


There is something called tracpipe?? which is flexible stainless
steel pipe intended for gas, which has fittings at each end to
join up with existing pipework. This could? be wangled through
the ceiling void if needed.

I used that for a run through screeded floor from the intake point. In
the event the boss chose an induction hob so it was never connected. The
gas fitter installing the boiler refused to consider certifying it
anyway.


--
Tim Lamb

On 03/03/2021 12:16, Robin wrote:
On 03/03/2021 11:22, bert wrote:
In article , Robin
writes
On 02/03/2021 23:57, Fredxx wrote:

snip
Â*If you know the kW of your boiler you would be able to calculate
the size of pipe you actually need. In domestic situations with
limited pipeÂ* runs 22mm copper pipe is a safe bet, plus to save
embarrassment to GasÂ* Safe installer Gas Safe have made a blanket
requirement to combis whereÂ* they must be piped in 22mm. Though I
would be happy to have the lastÂ* sectionin 15mm.


I don't want to give false hope to the OP who may well need a new gas
pipe.

But I've seen before on some sites that "Gas Safe regulations now
state that gas supply pipes from the meter to a combi boiler must be
at least 22mm". Smelt to me like a way to get more work and avoid the
bother of calculating pressure drops.Â* Gas Safe have no power to make
regulations.Â* And while the Gas Safety (Installation and Use)
Regulations were amended in 2018 I can't see anything in them about a
minimum pipe size. Have I missed something?


Only that when combi boilers first appeared a lot of installers used
the existing 15mm which was then found to be inadequate.

Thanks but I was aware of that.Â* And it's a bit of a leap from that to
"you *must* use 22mm even if it's a run of 1.5m with one bend to a 24 kW
combi". Only makes sense to me if Gas Safe members can no longer be
trusted to do sums and measure pressure drops at existing boiler.

Again, simple rules for simple people. I had huge arguments with the
building inspector when I wanted to use single glazing. But a report by
a heating engineering consultancy revealed that with enough insulation
in the walls and floor it met the regulations, was, in the end enough.

heating engineers of te corgi flavour doi not come equipped with brains
sufficient to deal with complex rulesets. 'use 22mm' is as simple rule
even a CORGI man can understand....

--
"When a true genius appears in the world, you may know him by this sign,
that the dunces are all in confederacy against him."

Jonathan Swift.

"The Natural Philosopher" wrote in message
...
My peak hot water requirements are easily met with a mains pressure
cylinder allowing me to use a mere 12kw boiler.
You need around 50kW to get a decent hot water supply.

The important thing is that your cylinder is fed by mains cold water rather
than a header tank. Our present house had a cylinder and a conventional
(non-combi, non-condensing) gas boiler. It took ages to heat up a tank of
water if you wanted more than one bath, and it also took about 5 minutes for
the water to run warm due to the length of pipe runs and the very low flow
rate, determined by a) 15 mm instead of 22 mm pipe for hot water, b) header
tank so only about 3 metres head.

When the cylinder developed a leak, we were originally going to have it
replaced, but the heating engineer found that the boiler was badly corroded
and wouldn't last much longer. So we had a combi/condensing boiler fitted,
giving mains-pressure hot water which runs hot much more quickly and is much
easier to mix with cold water in a shower or sink tap: the old one was so
low pressure that the cold tap could only be slightly open, otherwise the
combined water was virtually cold.

Our previous house had a cylinder (so the same time-to-reheat problem) but
at least it was mains-fed.

On 03/03/2021 14:39, NY wrote:
Our previous house had a cylinder (so the same time-to-reheat problem)
but at least it was mains-fed.

I have no ideas how long it takes to get my 150l tank back up to
temperature. I occasionally see the boiler fire up to do it in summer -
for maybe half an hour tops.

I do know that there is always enough hot water at 60C and 2 bar
pressure for any shower or bath




--
Future generations will wonder in bemused amazement that the early
twenty-first centurys developed world went into hysterical panic over a
globally average temperature increase of a few tenths of a degree, and,
on the basis of gross exaggerations of highly uncertain computer
projections combined into implausible chains of inference, proceeded to
contemplate a rollback of the industrial age.

Richard Lindzen

On 03/03/2021 14:24, The Natural Philosopher wrote:
On 03/03/2021 12:16, Robin wrote:
On 03/03/2021 11:22, bert wrote:
In article , Robin
writes
On 02/03/2021 23:57, Fredxx wrote:

snip
Â*If you know the kW of your boiler you would be able to calculate
the size of pipe you actually need. In domestic situations with
limited pipeÂ* runs 22mm copper pipe is a safe bet, plus to save
embarrassment to GasÂ* Safe installer Gas Safe have made a blanket
requirement to combis whereÂ* they must be piped in 22mm. Though I
would be happy to have the lastÂ* sectionin 15mm.


I don't want to give false hope to the OP who may well need a new
gas pipe.

But I've seen before on some sites that "Gas Safe regulations now
state that gas supply pipes from the meter to a combi boiler must be
at least 22mm". Smelt to me like a way to get more work and avoid
the bother of calculating pressure drops.Â* Gas Safe have no power to
make regulations.Â* And while the Gas Safety (Installation and Use)
Regulations were amended in 2018 I can't see anything in them about
a minimum pipe size. Have I missed something?


Only that when combi boilers first appeared a lot of installers used
the existing 15mm which was then found to be inadequate.

Thanks but I was aware of that.Â* And it's a bit of a leap from that to
"you *must* use 22mm even if it's a run of 1.5m with one bend to a 24
kW combi". Only makes sense to me if Gas Safe members can no longer be
trusted to do sums and measure pressure drops at existing boiler.

Again, simple rules for simple people. I had huge arguments with the
building inspector when I wanted to use single glazing. But a report by
a heating engineering consultancy revealed that with enough insulation
in the walls and floor it met the regulations, was, in the end enough.

They must be tiny windows then, and dripping with condensation in winter.

On 03/03/2021 14:47, The Natural Philosopher wrote:
On 03/03/2021 14:39, NY wrote:
Our previous house had a cylinder (so the same time-to-reheat problem)
but at least it was mains-fed.

I have no ideas how long it takes to get my 150l tank back up to
temperature. I occasionally see the boiler fire up to do it in summer -
for maybe half an hour tops.

I do know that there is always enough hot water at 60C and 2 bar
pressure for any shower or bath




A cheapo 24kW combi is perfectly adequate for one person and
more suited to smaller houses, provided the mains water can
supply sufficient pressure and flow.

On 03/03/2021 12:16, Robin wrote:
On 03/03/2021 11:22, bert wrote:
In article , Robin
writes
On 02/03/2021 23:57, Fredxx wrote:

snip
Â*If you know the kW of your boiler you would be able to calculate
the size of pipe you actually need. In domestic situations with
limited pipeÂ* runs 22mm copper pipe is a safe bet, plus to save
embarrassment to GasÂ* Safe installer Gas Safe have made a blanket
requirement to combis whereÂ* they must be piped in 22mm. Though I
would be happy to have the lastÂ* sectionin 15mm.


I don't want to give false hope to the OP who may well need a new gas
pipe.

But I've seen before on some sites that "Gas Safe regulations now
state that gas supply pipes from the meter to a combi boiler must be
at least 22mm". Smelt to me like a way to get more work and avoid the
bother of calculating pressure drops.Â* Gas Safe have no power to make
regulations.Â* And while the Gas Safety (Installation and Use)
Regulations were amended in 2018 I can't see anything in them about a
minimum pipe size. Have I missed something?


Only that when combi boilers first appeared a lot of installers used
the existing 15mm which was then found to be inadequate.

Thanks but I was aware of that.Â* And it's a bit of a leap from that to
"you *must* use 22mm even if it's a run of 1.5m with one bend to a 24 kW
combi". Only makes sense to me if Gas Safe members can no longer be
trusted to do sums and measure pressure drops at existing boiler.

On the other hand if you can do the sums, it can only point to you being
more "competent" than the average Gas Safe installer. So possibly a bit
of an own goal

On 03/03/2021 14:52, Andrew wrote:
On 03/03/2021 14:47, The Natural Philosopher wrote:
On 03/03/2021 14:39, NY wrote:
Our previous house had a cylinder (so the same time-to-reheat
problem) but at least it was mains-fed.

I have no ideas how long it takes to get my 150l tank back up to
temperature. I occasionally see the boiler fire up to do it in summer
- for maybe half an hour tops.

I do know that there is always enough hot water at 60C and 2 bar
pressure for any shower or bath




A cheapo 24kW combi is perfectly adequate for one person and
more suited to smaller houses, provided the mains water can
supply sufficient pressure and flow.

That is my view and policy. It also saves space, thermal losses for a
hot cylinder with the downfall of being less reliable and having no
backup hot water supply.

For a larger house where there are multiple occupants in the household
then a hot water cylinder approach with a smaller boiler seems to make
more sense.

On 03/03/2021 14:23, Adrian Caspersz wrote:
On 02/03/2021 23:57, Fredxx wrote:
On 02/03/2021 23:28, Nick wrote:
Hello all,

I need to reboiler my place.
The boiler is at least 45 years old and obviously cannot last forever.
I am somewhat older and the same conditions apply.

The supply to existing boiler is 1/2" steel pipe.
I'm told that I need to have a 22mm supply for a new condensing boiler.
The routing of existing pipework cannot be followed without
demolishing about half of the interior of the house. I'm not willing
to do that.

Would it be legal to run the majority of the pipework in armoured
rubber/flexible pipe?

The last metre or two at each end would be in metal tubing. All above
ground at high level (2M) and nothing external to the house.

I would appreciate your views.

Many thanks,
Nick.

It is a great shame that the website
Â*Â* http://wiki.diyfaq.org.uk
is still down as it includes pressure drop calculations of pipe runs.


Accessible of sorts through the wayback machine (the search won't work)

https://web.archive.org/web/20200217...heating_design

Thanks, I forgot about the wayback machine.

Does anyone know how long the wiki will be down?

On 03/03/2021 11:43, Andrew wrote:
On 03/03/2021 07:31, Tim+ wrote:
Nick wrote:
Hello all,

I need to reboiler my place.
The boiler is at least 45 years old and obviously cannot last forever.
I am somewhat older and the same conditions apply.

The supply to existing boiler is 1/2" steel pipe.
I'm told that I need to have a 22mm supply for a new condensing boiler.
The routing of existing pipework cannot be followed without demolishing
about half of the interior of the house. I'm not willing to do that.

Would it be legal to run the majority of the pipework in armoured
rubber/flexible pipe?

Im not an expert but I doubt it very much!


There is something called tracpipe?? which is flexible stainless
steel pipe intended for gas, which has fittings at each end to
join up with existing pipework. This could? be wangled through
the ceiling void if needed.

Looks good stuff, but £15-20/m. Mind the way copper pipe is getting more
and more expensive you never know it may be cost effective and
convenient for DIYers!

On 2021-03-03 12:16:53 +0000, Robin said:

On 03/03/2021 11:22, bert wrote:
In article , Robin
writes
On 02/03/2021 23:57, Fredxx wrote:

snip
*If you know the kW of your boiler you would be able to calculate the
size of pipe you actually need. In domestic situations with limited
pipe* runs 22mm copper pipe is a safe bet, plus to save embarrassment
to Gas* Safe installer Gas Safe have made a blanket requirement to
combis where* they must be piped in 22mm. Though I would be happy to
have the last* sectionin 15mm.


I don't want to give false hope to the OP who may well need a new gas pipe.

But I've seen before on some sites that "Gas Safe regulations now state
that gas supply pipes from the meter to a combi boiler must be at least
22mm". Smelt to me like a way to get more work and avoid the bother of
calculating pressure drops.* Gas Safe have no power to make
regulations.* And while the Gas Safety (Installation and Use)
Regulations were amended in 2018 I can't see anything in them about a
minimum pipe size. Have I missed something?


Only that when combi boilers first appeared a lot of installers used
the existing 15mm which was then found to be inadequate.

Thanks but I was aware of that. And it's a bit of a leap from that to
"you *must* use 22mm even if it's a run of 1.5m with one bend to a 24
kW combi". Only makes sense to me if Gas Safe members can no longer be
trusted to do sums and measure pressure drops at existing boiler.

We had a 20 year old 24kWh boiler replaced in the autumn - it was fed
by a fairly long15mm run. To play it safe and not change the pipework
the installer put in a 18kWh unit. As it is a more efficient condensing
boiler it seems to do pretty much the same job as the old one.

On 3 Mar 2021 at 14:52:38 GMT, "Andrew"
wrote:

On 03/03/2021 14:47, The Natural Philosopher wrote:
On 03/03/2021 14:39, NY wrote:
Our previous house had a cylinder (so the same time-to-reheat problem)
but at least it was mains-fed.

I have no ideas how long it takes to get my 150l tank back up to
temperature. I occasionally see the boiler fire up to do it in summer -
for maybe half an hour tops.

I do know that there is always enough hot water at 60C and 2 bar
pressure for any shower or bath




A cheapo 24kW combi is perfectly adequate for one person and
more suited to smaller houses, provided the mains water can
supply sufficient pressure and flow.

My 30kW boiler gives a very respectable shower.

Hot water is that it takes a good 30s to come through - tedious and wasting
water.

--
Cheers, Rob

The Natural Philosopher brought next idea :
heating engineers of te corgi flavour doi not come equipped with brains
sufficient to deal with complex rulesets. 'use 22mm' is as simple rule even a
CORGI man can understand....

+1