On Wed, 26 Aug 2015 17:55:53 +0100, John Rumm wrote:

On 26/08/2015 13:21, Graham. wrote:
On 26 Aug 2015 09:49:28 GMT, David wrote:

WB combi and potential slow flow - still not got round to
comprehensive diagnostics.

I've just (duh!) noticed that if the upstairs shower is turned to full
cold then the water fairly blasts out - so there is pressure and flow
at least in some of the cold side.

Boiler is a WB Greenstar CDi Classic 38CDi.
Manual says 19.i lpm 30C temperature rise, 14 lpm 40C temperature
rise. It was sized to be able to run two thermostatic mixer showers at
the same time.
Well over specified to heat a 3 bedroom semi.

I'm still not clear if it throttles the water flow to enable it to
meet the chosen temperature setting.

If it does, I assume that if I turn the boiler off and just run cold
through it this should show if there is something in the pipework on
the hot side which is restricting the flow?

Still puzzled, because a smaller version with the same shower mixer in
a previous house managed a much higher flow rate when filling the
bath.

As mentioned a while back, I don't currently have an unrestricted hot
take off - everything goes through a mixer tap or a thermostatic
shower.

One day I will find time to do some proper measurements.


Some boilers modulate the gas burners, but do any modulate the water
flow?

A few do...

It doesn't make sense to me. I would have thought the flow through the
boiler would not be subject to unnecessary restriction and your taps
and mixers determine the flow rate.

The taps determine the flow rate, but the question is what happens when
you select a flow rate that is faster than the boiler is capable of
heating to the desired temperature.

With many combis you can set the maximum temperature and the boiler
will modulate / cycle the burner to not exceed that at low flow rates.
However at high flow rates you would experience water insufficiently
heated unless you either have a boiler that can automatically restrict
the flow, or do it manually (e.g. but throttling the cold input to the
boiler, or by simply turning the tap down a bit)


Looking more and more like some kind of restriction between the boiler and
the thermostatic shower mixer.

I think I'm just looking for excuses to avoid taking the bath panel of (if
it will come off).




--
Windows 8.1 on PCSpecialist box

On 27/08/2015 09:36, David wrote:

Looking more and more like some kind of restriction between the boiler and
the thermostatic shower mixer.

I think I'm just looking for excuses to avoid taking the bath panel of (if
it will come off).


You haven't got one of those shower savers fitted on the flexible hose
have you? They are designed to restrict the flow and are just a disk
with a very small hole.

On Thu, 27 Aug 2015 11:33:36 +0100, dennis@home wrote:

On 27/08/2015 09:36, David wrote:

Looking more and more like some kind of restriction between the boiler
and the thermostatic shower mixer.

I think I'm just looking for excuses to avoid taking the bath panel of
(if it will come off).


You haven't got one of those shower savers fitted on the flexible hose
have you? They are designed to restrict the flow and are just a disk
with a very small hole.

Not as far as I am aware - restriction is also on filler for the bath as
this is a combined thermostatic shower mixer/bath tap mixer.

Wondering if the wrong type of isolation valve has been used (i.e. not
full bore).

Cheers

Dave R


--
Windows 8.1 on PCSpecialist box

David wrote:
On Thu, 27 Aug 2015 11:33:36 +0100, dennis@home wrote:

On 27/08/2015 09:36, David wrote:

Looking more and more like some kind of restriction between the boiler
and the thermostatic shower mixer.

I think I'm just looking for excuses to avoid taking the bath panel of
(if it will come off).


You haven't got one of those shower savers fitted on the flexible hose
have you? They are designed to restrict the flow and are just a disk
with a very small hole.

Not as far as I am aware - restriction is also on filler for the bath as
this is a combined thermostatic shower mixer/bath tap mixer.

Wondering if the wrong type of isolation valve has been used (i.e. not
full bore).


Distinctly possible. Can you post a link to a picture?

Restricted bore ones look "waisted" whereas full bore ones are fatter in
the middle, though not by as much as you might imagine.

Narrow bo

http://s7g3.scene7.com/is/image/ae235?$p$&layer=0&size=281,281&layer=1&size=281,28 1&src=ae235/65251_P

Full bo

http://s7g3.scene7.com/is/image/ae235/43961_P?$p$

Tim

On 28/08/2015 11:44, Tim+ wrote:
David wrote:
On Thu, 27 Aug 2015 11:33:36 +0100, dennis@home wrote:

On 27/08/2015 09:36, David wrote:

Looking more and more like some kind of restriction between the boiler
and the thermostatic shower mixer.

I think I'm just looking for excuses to avoid taking the bath panel of
(if it will come off).


You haven't got one of those shower savers fitted on the flexible hose
have you? They are designed to restrict the flow and are just a disk
with a very small hole.

Not as far as I am aware - restriction is also on filler for the bath as
this is a combined thermostatic shower mixer/bath tap mixer.

Wondering if the wrong type of isolation valve has been used (i.e. not
full bore).


Distinctly possible. Can you post a link to a picture?

Restricted bore ones look "waisted" whereas full bore ones are fatter in
the middle, though not by as much as you might imagine.

Narrow bo

http://s7g3.scene7.com/is/image/ae235?$p$&layer=0&size=281,281&layer=1&size=281,28 1&src=ae235/65251_P

Full bo

http://s7g3.scene7.com/is/image/ae235/43961_P?$p$

However at (high) combi pressures you are unlikely to notice the
difference - its more of an issue on gravity fed systems.


--
Cheers,

John.

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On Fri, 28 Aug 2015 14:32:30 +0100, John Rumm wrote:

On 28/08/2015 11:44, Tim+ wrote:
David wrote:
On Thu, 27 Aug 2015 11:33:36 +0100, dennis@home wrote:

On 27/08/2015 09:36, David wrote:

Looking more and more like some kind of restriction between the
boiler and the thermostatic shower mixer.

I think I'm just looking for excuses to avoid taking the bath panel
of (if it will come off).


You haven't got one of those shower savers fitted on the flexible
hose have you? They are designed to restrict the flow and are just a
disk with a very small hole.

Not as far as I am aware - restriction is also on filler for the bath
as this is a combined thermostatic shower mixer/bath tap mixer.

Wondering if the wrong type of isolation valve has been used (i.e. not
full bore).


Distinctly possible. Can you post a link to a picture?

Restricted bore ones look "waisted" whereas full bore ones are fatter
in the middle, though not by as much as you might imagine.

Narrow bo

http://s7g3.scene7.com/is/image/ae235?$p
$&layer=0&size=281,281&layer=1&size=281,281&src=ae 235/65251_P

Full bo

http://s7g3.scene7.com/is/image/ae235/43961_P?$p$

However at (high) combi pressures you are unlikely to notice the
difference - its more of an issue on gravity fed systems.

I suspect one issue is that the pressure is only medium at best.
But then again the pressure limiting valve for the water softener is
showing 3 bar.

Another great mystery of the sea where I can't get it to the top of my
priority list.
Only high enough up to grumble occasionally. :-(

Cheers

Dave R



--
Windows 8.1 on PCSpecialist box

Tim+ wrote:
wrote:

On Thu, 27 Aug 2015 11:33:36 +0100, dennis@home wrote:


On 27/08/2015 09:36, David wrote:


Looking more and more like some kind of restriction between the boiler
and the thermostatic shower mixer.

I think I'm just looking for excuses to avoid taking the bath panel of
(if it will come off).



You haven't got one of those shower savers fitted on the flexible hose
have you? They are designed to restrict the flow and are just a disk
with a very small hole.

Not as far as I am aware - restriction is also on filler for the bath as
this is a combined thermostatic shower mixer/bath tap mixer.

Wondering if the wrong type of isolation valve has been used (i.e. not
full bore).


Distinctly possible. Can you post a link to a picture?

Restricted bore ones look "waisted" whereas full bore ones are fatter in
the middle, though not by as much as you might imagine.

Narrow bo

http://s7g3.scene7.com/is/image/ae235?$p$&layer=0&size=281,281&layer=1&size=281,28 1&src=ae235/65251_P

Full bo

http://s7g3.scene7.com/is/image/ae235/43961_P?$p$

Tim

Is the shower hose kinked? I fitted a new 11mm id one last week
and its rubber pipe was almost completely blocked when removed from the
packaging. Never seen that before.