Just back from being away for two weeks and thought my water pressure was a
bit low.
I phoned the waterboard in case there was some known problem. Thy said no.

I realise now that the cold is okay but the hot is a low.

I have a Worcester Bosch Greenstar Combi. Is there anything I should look
for?

Roger Mills wrote in
:

On 23/12/2014 16:52, DerbyBorn wrote:
Just back from being away for two weeks and thought my water pressure
was a bit low.
I phoned the waterboard in case there was some known problem. Thy
said no.

I realise now that the cold is okay but the hot is a low.

I have a Worcester Bosch Greenstar Combi. Is there anything I should
look for?

Summer? The flow will be higher when it doesn't have to raise the
temperature so much!

How? Does the boiler moderate the flow in some way? I don't remember it
last winter.

On 23/12/2014 16:52, DerbyBorn wrote:
Just back from being away for two weeks and thought my water pressure was a
bit low.
I phoned the waterboard in case there was some known problem. Thy said no.

I realise now that the cold is okay but the hot is a low.

I have a Worcester Bosch Greenstar Combi. Is there anything I should look
for?

Summer? The flow will be higher when it doesn't have to raise the
temperature so much!
--
Cheers,
Roger
____________
Please reply to Newsgroup. Whilst email address is valid, it is seldom
checked.

On 23/12/2014 17:18, DerbyBorn wrote:
Roger wrote in
:

On 23/12/2014 16:52, DerbyBorn wrote:
Just back from being away for two weeks and thought my water pressure
was a bit low.
I phoned the waterboard in case there was some known problem. Thy
said no.

I realise now that the cold is okay but the hot is a low.

I have a Worcester Bosch Greenstar Combi. Is there anything I should
look for?

Summer? The flow will be higher when it doesn't have to raise the
temperature so much!

How? Does the boiler moderate the flow in some way? I don't remember it
last winter.

Yes, the boiler controls the outlet water temperature. If it's not hot
enough with the burner on full, the only way it can make it any hotter
is by slowing down the flow.
--
Cheers,
Roger
____________
Please reply to Newsgroup. Whilst email address is valid, it is seldom
checked.

On 23/12/2014 17:18, DerbyBorn wrote:
Roger Mills wrote in
:

On 23/12/2014 16:52, DerbyBorn wrote:
Just back from being away for two weeks and thought my water pressure
was a bit low.
I phoned the waterboard in case there was some known problem. Thy
said no.

I realise now that the cold is okay but the hot is a low.

I have a Worcester Bosch Greenstar Combi. Is there anything I should
look for?

Summer? The flow will be higher when it doesn't have to raise the
temperature so much!

How? Does the boiler moderate the flow in some way? I don't remember it
last winter.

Not sure about this model but some have a "temperature" knob; turn that
up and it reduces the flow (like an electric shower). Do you have an OH
who might have got at it?

Summer? The flow will be higher when it doesn't have to raise the
temperature so much!

How? Does the boiler moderate the flow in some way? I don't remember it
last winter.

Not sure about this model but some have a "temperature" knob; turn that
up and it reduces the flow (like an electric shower). Do you have an OH
who might have got at it?


It is in the loft - and the controls are under a cover. She would have
absolutley no interest in even going near it.
So the view is that intial temp setting is by flame height - if that can't
meet the target set then the flow is reduced. Logical - but is mine really
like this?

On Tue, 23 Dec 2014 18:00:38 +0000, DerbyBorn wrote:


Summer? The flow will be higher when it doesn't have to raise the
temperature so much!

How? Does the boiler moderate the flow in some way? I don't remember
it last winter.

Not sure about this model but some have a "temperature" knob; turn that
up and it reduces the flow (like an electric shower). Do you have an OH
who might have got at it?


It is in the loft - and the controls are under a cover. She would have
absolutley no interest in even going near it.
So the view is that intial temp setting is by flame height - if that
can't meet the target set then the flow is reduced. Logical - but is
mine really like this?

Hopefully a simple example.
Assume you want hot water at 50C.

Assume the boiler can raise the water temperature by 30C when going full
blast and full water flow.

In the summer the incoming cold is 20C so it raises the water to 50C going
full blast. A rise of 30C.

In the winter the incoming cold is at 5C, so at full blast full flow it
only raise the water to 35C. A rise of 30C.

So the only way to increase the temperature of the incoming water is to
reduce the flow so that the same amount of heat is used to heat less water.
With a target of 50C it has to slow down the water flow quite a bit.
(I would guess to 75% of full flow in this example).

HTH

Dave R



--
Windows 8.1 on PCSpecialist box

On 23 Dec 2014 18:37:57 GMT, David wrote:

In the summer the incoming cold is 20C so it raises the water to 50C
going full blast. A rise of 30C.

A flow of 10 l/min and 30 C temp rise requires 20.94 kW.

In the winter the incoming cold is at 5C, so at full blast full flow it
only raise the water to 35C. A rise of 30C.

A flow of 10 l/min and 45 C temp rise requires 31.4 kW.
A flow of 6.5 l/min and 45 C temp rise requires 20.41 kW.

(I would guess to 75% of full flow in this example).

Close enough. B-)

--
Cheers
Dave.

On 23/12/14 17:43, Roger Mills wrote:
On 23/12/2014 17:18, DerbyBorn wrote:
Roger wrote in
:

On 23/12/2014 16:52, DerbyBorn wrote:
Just back from being away for two weeks and thought my water pressure
was a bit low.
I phoned the waterboard in case there was some known problem. Thy
said no.

I realise now that the cold is okay but the hot is a low.

I have a Worcester Bosch Greenstar Combi. Is there anything I should
look for?

Summer? The flow will be higher when it doesn't have to raise the
temperature so much!

How? Does the boiler moderate the flow in some way? I don't remember it
last winter.

Yes, the boiler controls the outlet water temperature. If it's not hot
enough with the burner on full, the only way it can make it any hotter
is by slowing down the flow.

Can the OP's boiler actually modulate the water flow? I've not come
across a combi that does - but then I only come across older combis in
friends houses etc.

On 23/12/2014 20:25, Tim Watts wrote:
On 23/12/14 17:43, Roger Mills wrote:
On 23/12/2014 17:18, DerbyBorn wrote:
Roger wrote in
:

On 23/12/2014 16:52, DerbyBorn wrote:
Just back from being away for two weeks and thought my water pressure
was a bit low.
I phoned the waterboard in case there was some known problem. Thy
said no.

I realise now that the cold is okay but the hot is a low.

I have a Worcester Bosch Greenstar Combi. Is there anything I should
look for?

Summer? The flow will be higher when it doesn't have to raise the
temperature so much!

How? Does the boiler moderate the flow in some way? I don't remember it
last winter.

Yes, the boiler controls the outlet water temperature. If it's not hot
enough with the burner on full, the only way it can make it any hotter
is by slowing down the flow.

Can the OP's boiler actually modulate the water flow? I've not come
across a combi that does - but then I only come across older combis in
friends houses etc.

I think it must do. If not, he'd have reported a different problem -
with the water not being hot enough.
--
Cheers,
Roger
____________
Please reply to Newsgroup. Whilst email address is valid, it is seldom
checked.

On Tue, 23 Dec 2014 20:49:49 +0000, Roger Mills
wrote:

On 23/12/2014 20:25, Tim Watts wrote:
On 23/12/14 17:43, Roger Mills wrote:
On 23/12/2014 17:18, DerbyBorn wrote:
Roger wrote in
:

On 23/12/2014 16:52, DerbyBorn wrote:
Just back from being away for two weeks and thought my water pressure
was a bit low.
I phoned the waterboard in case there was some known problem. Thy
said no.

I realise now that the cold is okay but the hot is a low.

I have a Worcester Bosch Greenstar Combi. Is there anything I should
look for?

Summer? The flow will be higher when it doesn't have to raise the
temperature so much!

How? Does the boiler moderate the flow in some way? I don't remember it
last winter.

Yes, the boiler controls the outlet water temperature. If it's not hot
enough with the burner on full, the only way it can make it any hotter
is by slowing down the flow.

Can the OP's boiler actually modulate the water flow? I've not come
across a combi that does - but then I only come across older combis in
friends houses etc.

I think it must do. If not, he'd have reported a different problem -
with the water not being hot enough.

Must it?
Perhaps he didn't notice a temperature change.

Do boilers modulate the flow?
If they do, know body has said so.

It seems like an unnecessarily complication to me, after all the user
can reduce the flow by not turning the tap on as much or get full flow
albeit at a reduced temparature. Their call.

--

Graham.

%Profound_observation%

I cannot see anything on the schematic diagram that implies any mechanism
for reducing the flow.

On Tue, 23 Dec 2014 23:03:29 +0000, DerbyBorn wrote:

I cannot see anything on the schematic diagram that implies any
mechanism for reducing the flow.

However a thermostatic mixer shower will reduce the flow of cold to
maintain the required temperature if the incoming hot water is not up to
temperature - especially if the incoming cold is very cold.

I have no idea if it throttles the hot.

What I have observed is that with our thermostatic mixer it runs very
slowly until the hot water comes through then speeds up a lot. I assume
this is because it shuts off the cold until the hot water needs some cold
adding to it.

Cheers

Dave R


--
Windows 8.1 on PCSpecialist box