My hot water tank has stopped getting properly hot. The heating is
working fine, so it's unlikely to be a boiler issue. The pump seems OK
and the thermostat ~seems~ to be operating fine (on the basis of a click
as you turn the knob). There's no air in the circuit judging by the
bleed valve. I'm tempted to replace the thermostat, just cos I can, but
I'm not convinced that's going to achieve anything.

Any (sensible) suggestions would be appreciated.

Standard open vented indirect tank and boiler with nothing fancy like
weather compensation etc. No recent issues. DHW timer set to run when
the heating is off.

Cheers people

On 28/02/2021 14:42, GMM wrote:
My hot water tank has stopped getting properly hot.Â* The heating is
working fine, so it's unlikely to be a boiler issue.Â* The pump seems OK
and the thermostat ~seems~ to be operating fine (on the basis of a click
as you turn the knob).Â* There's no air in the circuit judging by the
bleed valve.Â* I'm tempted to replace the thermostat, just cos I can, but
I'm not convinced that's going to achieve anything.

Any (sensible) suggestions would be appreciated.

Standard open vented indirect tank and boiler with nothing fancy like
weather compensation etc. No recent issues.Â* DHW timer set to run when
the heating is off.

Cheers people


Can you feel hot water entering the DHW coil as and when it should?

PA

On Sunday, 28 February 2021 at 14:50:08 UTC, Peter Able wrote:
On 28/02/2021 14:42, GMM wrote:
My hot water tank has stopped getting properly hot. The heating is
working fine, so it's unlikely to be a boiler issue. The pump seems OK
and the thermostat ~seems~ to be operating fine (on the basis of a click
as you turn the knob). There's no air in the circuit judging by the
bleed valve. I'm tempted to replace the thermostat, just cos I can, but
I'm not convinced that's going to achieve anything.

Any (sensible) suggestions would be appreciated.

Standard open vented indirect tank and boiler with nothing fancy like
weather compensation etc. No recent issues. DHW timer set to run when
the heating is off.

Cheers people

Can you feel hot water entering the DHW coil as and when it should?

PA

Faulty valve or diverter

Richard

GMM used his keyboard to write :
Standard open vented indirect tank and boiler with nothing fancy like weather
compensation etc. No recent issues. DHW timer set to run when the heating is
off.

Has the boiler flow temperature been reduced?

Check the cylinder stat temperature setting?

Check the HW time clock is on for long enough?

Check an HW tap has not been left on.

Harry Bloomfield, Esq. explained :
Check an HW tap has not been left on.

Check the 3-port valve is properly switching to heat the cylinder.

On 28/02/2021 15:28, Chris Hogg wrote:
On Sun, 28 Feb 2021 14:42:21 +0000, GMM wrote:

My hot water tank has stopped getting properly hot. The heating is
working fine, so it's unlikely to be a boiler issue. The pump seems OK
and the thermostat ~seems~ to be operating fine (on the basis of a click
as you turn the knob). There's no air in the circuit judging by the
bleed valve. I'm tempted to replace the thermostat, just cos I can, but
I'm not convinced that's going to achieve anything.

Any (sensible) suggestions would be appreciated.

Standard open vented indirect tank and boiler with nothing fancy like
weather compensation etc. No recent issues. DHW timer set to run when
the heating is off.

Cheers people

What sort of DHW/CH system is it?
S-plan: https://tinyurl.com/yaxejpa6 ?
or
Y-plan: https://tinyurl.com/yd69szy9 ?

If the first, the zone valve in the DHW circuit on the LHS in the
diagram may have failed, or the controller isn't sending the 'open
valve' signal correctly.

If the second, the mid-position valve may not be working properly and
be stuck in the CH position.

I've puzzled over those sort of diagrams in the past and neither fits
the situation precisely, but I suppose the S-plan is the closer (mine
splits to two separate pumps, with a valve on the heating circuit after
its pump. No valve on the DHW side apart from the thermostat-controlled
bypass)
So far as I can tell, both valves are operating correctly, as are both
pumps, which is why I'm a bit lost in terms of th mechanical side of it....

On 28/02/2021 14:50, Peter Able wrote:
On 28/02/2021 14:42, GMM wrote:
My hot water tank has stopped getting properly hot.Â* The heating is
working fine, so it's unlikely to be a boiler issue.Â* The pump seems
OK and the thermostat ~seems~ to be operating fine (on the basis of a
click as you turn the knob).Â* There's no air in the circuit judging by
the bleed valve.Â* I'm tempted to replace the thermostat, just cos I
can, but I'm not convinced that's going to achieve anything.

Any (sensible) suggestions would be appreciated.

Standard open vented indirect tank and boiler with nothing fancy like
weather compensation etc. No recent issues.Â* DHW timer set to run when
the heating is off.

Cheers people


Can you feel hot water entering the DHW coil as and when it should?

PA

It feels hot but of course I haven't held onto the pipe for the full
time the boiler is running....

On 28/02/2021 15:07, Tricky Dicky wrote:
On Sunday, 28 February 2021 at 14:50:08 UTC, Peter Able wrote:
On 28/02/2021 14:42, GMM wrote:
My hot water tank has stopped getting properly hot. The heating is
working fine, so it's unlikely to be a boiler issue. The pump seems OK
and the thermostat ~seems~ to be operating fine (on the basis of a click
as you turn the knob). There's no air in the circuit judging by the
bleed valve. I'm tempted to replace the thermostat, just cos I can, but
I'm not convinced that's going to achieve anything.

Any (sensible) suggestions would be appreciated.

Standard open vented indirect tank and boiler with nothing fancy like
weather compensation etc. No recent issues. DHW timer set to run when
the heating is off.

Cheers people

Can you feel hot water entering the DHW coil as and when it should?

PA

Faulty valve or diverter

Richard

They seem to b operating OK in terms of opening/closing when given a
signal...

On 01/03/2021 11:46, GMM wrote:
On 28/02/2021 15:07, Tricky Dicky wrote:
On Sunday, 28 February 2021 at 14:50:08 UTC, Peter Able wrote:
On 28/02/2021 14:42, GMM wrote:
My hot water tank has stopped getting properly hot. The heating is
working fine, so it's unlikely to be a boiler issue. The pump seems OK
and the thermostat ~seems~ to be operating fine (on the basis of a
click
as you turn the knob). There's no air in the circuit judging by the
bleed valve. I'm tempted to replace the thermostat, just cos I can, but
I'm not convinced that's going to achieve anything.

Any (sensible) suggestions would be appreciated.

Standard open vented indirect tank and boiler with nothing fancy like
weather compensation etc. No recent issues. DHW timer set to run when
the heating is off.

Cheers people

Can you feel hot water entering the DHW coil as and when it should?

PA

Faulty valve or diverter

Richard

They seem to b operating OK in terms of opening/closing when given a
signal...

When the DHW circuit is pumping, how hot are 22mm pipes feeding the
tank ?. Do you have a clip-on thermometer or one of those laser
ones to see what temp of water is arriving and leaving the tank.

On 01/03/2021 11:45, GMM wrote:
On 28/02/2021 14:50, Peter Able wrote:
On 28/02/2021 14:42, GMM wrote:
My hot water tank has stopped getting properly hot.Â* The heating is
working fine, so it's unlikely to be a boiler issue.Â* The pump seems
OK and the thermostat ~seems~ to be operating fine (on the basis of a
click as you turn the knob).Â* There's no air in the circuit judging
by the bleed valve.Â* I'm tempted to replace the thermostat, just cos
I can, but I'm not convinced that's going to achieve anything.

Any (sensible) suggestions would be appreciated.

Standard open vented indirect tank and boiler with nothing fancy like
weather compensation etc. No recent issues.Â* DHW timer set to run
when the heating is off.

Cheers people


Can you feel hot water entering the DHW coil as and when it should?

PA

It feels hot but of course I haven't held onto the pipe for the full
time the boiler is running....

If your boiler is supplyng water at 80+ C then it wouldn't 'feel'
hot, it would be 'ouch, fkit' hot.
Can you check your 3way valve and make sure it is operating properly ?.

On Monday, March 1, 2021 at 2:40:23 PM UTC, Andrew wrote:

It feels hot but of course I haven't held onto the pipe for the full
time the boiler is running....
If your boiler is supplyng water at 80+ C then it wouldn't 'feel'
hot, it would be 'ouch, fkit' hot.
Can you check your 3way valve and make sure it is operating properly ?.

Yup - that's about the temperature (!) I'll see if I can get my IR thermometer on it later and find out roughly what 'ouch fkit hot' equates to....

On 01/03/2021 11:43, GMM wrote:

the thermostat-controlled bypass

Can you explain this? A bypass of what?

PA

On 01/03/2021 16:29, Glenn Matthews wrote:
Yup - that's about the temperature (!) I'll see if I can get my IR thermometer on it later and find out roughly what 'ouch fkit hot' equates to....

IR thermometers aren't very accurate on shiny pipes. You might want to
stick some opaque tape on it.

See

https://www.flukeprocessinstruments.com/en-us/service-and-support/knowledge-center/infrared-technology/what-is-emissivity

AKA https://tinyurl.com/ybwqfn36

Andy

On Monday, 1 March 2021 at 19:16:03 UTC, Peter Able wrote:
On 01/03/2021 11:43, GMM wrote:

the thermostat-controlled bypass

Can you explain this? A bypass of what?

PA
Yes! The cylinder should be controlling a valve. Bypass that I am familiar with have no electrical connection being simple mechanical devices that you set separate on the bypass.

On 02/03/2021 11:30, Tricky Dicky wrote:
On Monday, 1 March 2021 at 19:16:03 UTC, Peter Able wrote:
On 01/03/2021 11:43, GMM wrote:

the thermostat-controlled bypass

Can you explain this? A bypass of what?

PA
Yes! The cylinder should be controlling a valve. Bypass that I am familiar with have no electrical connection being simple mechanical devices that you set separate on the bypass.


Had to read that a couple of times. The plural of Bypass is Bypasses.
As you describe, relatively dumb, set and forget components - which
could be in parallel with the DHW coil. If so, and set fully open,
problem identified - maybe!

Any response, GMM ?

PA