Hi all,

I have a problem with my boiler (Potterton Kingfisher boiler CF40 from
1992)... The hot water in the tank does not seem to warm up very much,
even when I increase the thermostat on the boiler to MAX. It fires up
for about 1 minute then goes off for 10 minutes. I can hear the boiler
thermostat "click" at between 1 and 2 but increasing the thermostat to
above the click does not make the boiler fire up as I would expect it
to (hot water setting is turned to "constant" on the controller).

However, if I turn the heating to "constant" too, the boiler does fire
up and stays on. The radiators get very hot (I increased the thermostat
on the boiler to MAX) but the water from the tank is still lukewarm.
There is no thermostat in any room for central heating by the way. The
thermostat on the boiler then clicks between 4 and MAX.

Is there usually one thermostat for the hot water tank and another for
the heating? If so, maybe the thermostat for the hot water tank may be
dodgy...?

Any ideas?
thanks,
Andrew

In an earlier contribution to this discussion,
Andrew wrote:

Hi all,

I have a problem with my boiler (Potterton Kingfisher boiler CF40 from
1992)... The hot water in the tank does not seem to warm up very much,
even when I increase the thermostat on the boiler to MAX. It fires up
for about 1 minute then goes off for 10 minutes. I can hear the boiler
thermostat "click" at between 1 and 2 but increasing the thermostat to
above the click does not make the boiler fire up as I would expect it
to (hot water setting is turned to "constant" on the controller).

However, if I turn the heating to "constant" too, the boiler does fire
up and stays on. The radiators get very hot (I increased the
thermostat on the boiler to MAX) but the water from the tank is still
lukewarm. There is no thermostat in any room for central heating by
the way. The thermostat on the boiler then clicks between 4 and MAX.

Is there usually one thermostat for the hot water tank and another for
the heating? If so, maybe the thermostat for the hot water tank may be
dodgy...?

Any ideas?
thanks,
Andrew

How many water pipes (not to be confused with the gas feed pipe) are
connected to your boiler?

Do you have any motorised valves anywhere (such as in the airing cupboard)?
If so, how many, and how many water connections does each have?

Answers to these questions will help to establish whether you have a gravity
hot water or fully pumped system. The cause of your problem is different,
depending on what type of system you have.
--
Cheers,
Roger
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thanks for your reply.

The boiler is in a single floor flat at the same height as the
cylinder. There are 2 pipes going to the cylinder and 2 other pipes
which I assume to be the central heating circuit.

There looks to be one motorised valve inside the boiler cabinet itself
- placed on one pipe after the output from the pump splits into 2. It's
on the central heating pipe.

I investigated the cylinder further and found the thermostat there, set
to 60

The hot water tap was a bit spluttery. So I'm thinking now of air lock
rather than dodgy thermostat...?

Andrew

In an earlier contribution to this discussion,
Andrew wrote:

thanks for your reply.

The boiler is in a single floor flat at the same height as the
cylinder. There are 2 pipes going to the cylinder and 2 other pipes
which I assume to be the central heating circuit.

There looks to be one motorised valve inside the boiler cabinet itself
- placed on one pipe after the output from the pump splits into 2.
It's on the central heating pipe.

I investigated the cylinder further and found the thermostat there,
set to 60

The hot water tap was a bit spluttery. So I'm thinking now of air lock
rather than dodgy thermostat...?

Andrew

Hm - I'm afraid your description doesn't fit anything with which I am
familiar.

Any chance of taking some piccis of the boiler, pump and cylinder
connections - and uploading them somewhere where we can see them?
--
Cheers,
Roger
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I tried to take some photos but apart from one of the boiler front,
showing no pipes, the cupboard was too cramped to get the camera to
focus.

I did follow wires from the controller junction box and found that
there is actually another motorised valve on the hot water pipe at the
back of the boiler. I wouldn't fancy changing that, it is quite
inaccessible.

Which aspect of the system sounds odd? - I might be able to clarify.

Is it worth testing the tank thermostat? That's the easiest bit to
remove! I don't think that the motorised valve has shut totally because
the water in the cylinder does warm up a bit.

Thanks for your help,
Andrew

In an earlier contribution to this discussion,
Andrew wrote:

I tried to take some photos but apart from one of the boiler front,
showing no pipes, the cupboard was too cramped to get the camera to
focus.

I did follow wires from the controller junction box and found that
there is actually another motorised valve on the hot water pipe at the
back of the boiler. I wouldn't fancy changing that, it is quite
inaccessible.

Which aspect of the system sounds odd? - I might be able to clarify.

Is it worth testing the tank thermostat? That's the easiest bit to
remove! I don't think that the motorised valve has shut totally
because the water in the cylinder does warm up a bit.

Thanks for your help,
Andrew

It sounded odd when you said that there was only one motorised valve - on
the CH circuit. I would expect either two 2-port valves - one on each
circuit - (S-Plan) or one 3-port valve at the point where the circuits
divide after the pump (Y-Plan).

Now that you have found the second valve, it sounds less odd! It sounds as
if you have a fairly conventional S-Plan system. You can see how it is
supposed to work by looking at the schematic and wiring diagram for S-Plan
in http://content.honeywell.com/uk/homes/systems.htm

In essence, the HW valve is driven by the programmer and tank stat. The CH
valve is driven by the programmer and room stat. Both valves have a set of
auxilliary contacts which close when the valve opens. These contacts are
used to switch on the boiler and pump.

If your hot water isn't getting hot enough, it could be due to:
* programmer not turning it on for long enough
* faulty cylinder stat (or incorrect setting) closing the valve too early
* valve not opening, or faulty auxilliary contacts

That should give you a few things to check!
--
Cheers,
Roger
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thanks a lot for the info Roger.

1. I'm using the programmer on Constant setting for testing. I did open
up the wiring centre junction box and tested some terminals with neon
screwdriver. There seemed to be a voltage to the HW ON terminal
regardless of the setting (Const/OFF) of the hot water on the
controller, which seemed a bit odd to me. The CH ON terminal switched
as I would have expected, when CH was moved between Const and Off on
the controller.
2. Tested the cylinder stat and it is working fine, so I've ruled that
out.
3. Tried activating the manual lever on the HW valve when HW had been
on for its 2 minutes and then switched itself off. The boiler and pump
came on for 1 second and then off again, even when I locked the lever
in manual position.

Is the auxiliiary switch a feedback from the valve to the controller to
turn on the pump and boiler? Would moving the lever to manual trigger
that switch?

I was thinking of swapping the heads on the 2 valves since the CH is
behaving fine and the HW is not. The HW valve has 6 connections but the
CH one has 5 (no white).

Does it sound like the valve is at fault? Is there any voltage test I
could do on the terminals that would help diagnose the problem?

Thanks again for your help,
Andrew

In an earlier contribution to this discussion,
Andrew wrote:

thanks a lot for the info Roger.

Can I repeat the plea made in other threads - when replying to someone's
message, PLEASE, PLEASE quote at least some of it so that people can see the
context. I had to pull up the whole thread to remind myself what had already
been said. A lot of people - quite understandably - wouldn't bother, so you
wouldn't get a reply.

1. I'm using the programmer on Constant setting for testing. I did
open up the wiring centre junction box and tested some terminals with
neon screwdriver. There seemed to be a voltage to the HW ON terminal
regardless of the setting (Const/OFF) of the hot water on the
controller, which seemed a bit odd to me. The CH ON terminal switched
as I would have expected, when CH was moved between Const and Off on
the controller.

As has been said many times before, a neon screwdriver is just about the
*least* reliable way of testing for 'liveness' - and can often give
misleading results. [Just copping hold of the wire is more accurate! g]
Seriously, though, you need a 250v AC voltmeter referenced to neutral to
determine what is truly live - and preferably a lowish impedance analog one
at that.

2. Tested the cylinder stat and it is working fine, so I've ruled that
out.

How did you test it?

3. Tried activating the manual lever on the HW valve when HW had been
on for its 2 minutes and then switched itself off. The boiler and pump
came on for 1 second and then off again, even when I locked the lever
in manual position.

Is the auxiliiary switch a feedback from the valve to the controller
to turn on the pump and boiler?

Not if it's a conventional S-Plan system. Did you look at the schematic and
circuit diagram which I referenced earlier? Did you understand it? If you
did, you will realise that the auxilliary switches are provided with a
permanent live - so that when they switch, they turn the boiler and pump on
regardless of what the programmer and stats are doing. [This can sometimes
lead to a different sort of fault where a valve sticks open, and the system
runs even when everything is turned off!]

Would moving the lever to manual trigger that switch?

I would expect it to, but am not 100% sure.

I was thinking of swapping the heads on the 2 valves since the CH is
behaving fine and the HW is not. The HW valve has 6 connections but
the CH one has 5 (no white).

Again, if it's conventional S-Plan, the white wire is not needed - and won't
be doing anything on the valve which has it - so you should be able to swap
heads.

Does it sound like the valve is at fault? Is there any voltage test I
could do on the terminals that would help diagnose the problem?

Well, it could be interesting to swap heads, and see whether the HW then
works ok but the CH doesn't. My hunch is that it won't make any difference.

Looking at your initial post, I suspect that there is *some* flow from the
boiler to the coil in the hot water cylinder, but not very much - which
might explain why the boiler only fires for a small percentage of the time
when trying to heat the HW. Are you *sure* that when the boiler stops, the
pump also stops? My hunch is that the boiler's own thermostat is turning
that off, but the pump is still running. Are the pipes which go the HW
cylinder hot under these circumstances? Is there a manual balancing valve in
the HW circuit which may be almost closed, preventing the necessary amount
of flow? Is there a bi-pass valve which could be stuck open,
short-circuiting the HW coil?

Finally, is it a vented system, or a sealed (pressurised) one?
--
Cheers,
Roger
______
Please reply to newsgroup.
Reply address IS valid, but not regularly monitored.

Summary so far: Honeywell S-Plan system. The problem started on its
own, not following any modifications or maintenance to the system. CH
works fine. When HW switched on alone without CH, boiler ignites and
pumps for a couple of mins only before turning off. It sometimes comes
back on after about 10 mins but only for 1 minute.

Switching on the CH and HW together and moving the HW motor valve to
Manual sometimes gets a full tank of water. But, sometimes when I try
this, the lever on the HW valve moves back to about half way across and
the valve is shut.

When HW only is on and the boiler is not doing anything, the pump is
not running. Tested with multimeter that the brown wire to the HW valve
is 240V with respect to neutral. The orange from the microswitch is not
live at this point. Moving the lever to manual makes the boiler and
pump active but literally for 1 second, before dying.

Tested tank thermostat with multimeter. It switched fine between
terminals 1 and 2. Tank thermostat is set to 60 degrees, the boiler
stat is set to MAX. Can't see a manual balancing valve. The pipe on the
cylinder side of the motor valve is not hot when the HW is not working.
It's a flat so I can't be sure where all the vertical pipes are
actually going. Apart from the coil in and out, there are only 2 pipes
to/from the cylinder fill at bottom and outgoing out from the top of
the cylinder - does that alone mean a sealed system?

We've been away from the house but the wife is now getting fed up with
using the immersion heater so I need to do something! :-)

Thanks for any help,
Andrew

Roger Mills wrote:
In an earlier contribution to this discussion,
Andrew wrote:

thanks a lot for the info Roger.

Can I repeat the plea made in other threads - when replying to someone's
message, PLEASE, PLEASE quote at least some of it so that people can see the
context. I had to pull up the whole thread to remind myself what had already
been said. A lot of people - quite understandably - wouldn't bother, so you
wouldn't get a reply.

1. I'm using the programmer on Constant setting for testing. I did
open up the wiring centre junction box and tested some terminals with
neon screwdriver. There seemed to be a voltage to the HW ON terminal
regardless of the setting (Const/OFF) of the hot water on the
controller, which seemed a bit odd to me. The CH ON terminal switched
as I would have expected, when CH was moved between Const and Off on
the controller.

As has been said many times before, a neon screwdriver is just about the
*least* reliable way of testing for 'liveness' - and can often give
misleading results. [Just copping hold of the wire is more accurate! g]
Seriously, though, you need a 250v AC voltmeter referenced to neutral to
determine what is truly live - and preferably a lowish impedance analog one
at that.

2. Tested the cylinder stat and it is working fine, so I've ruled that
out.

How did you test it?

3. Tried activating the manual lever on the HW valve when HW had been
on for its 2 minutes and then switched itself off. The boiler and pump
came on for 1 second and then off again, even when I locked the lever
in manual position.

Is the auxiliiary switch a feedback from the valve to the controller
to turn on the pump and boiler?

Not if it's a conventional S-Plan system. Did you look at the schematic and
circuit diagram which I referenced earlier? Did you understand it? If you
did, you will realise that the auxilliary switches are provided with a
permanent live - so that when they switch, they turn the boiler and pump on
regardless of what the programmer and stats are doing. [This can sometimes
lead to a different sort of fault where a valve sticks open, and the system
runs even when everything is turned off!]

Would moving the lever to manual trigger that switch?

I would expect it to, but am not 100% sure.

I was thinking of swapping the heads on the 2 valves since the CH is
behaving fine and the HW is not. The HW valve has 6 connections but
the CH one has 5 (no white).

Again, if it's conventional S-Plan, the white wire is not needed - and won't
be doing anything on the valve which has it - so you should be able to swap
heads.

Does it sound like the valve is at fault? Is there any voltage test I
could do on the terminals that would help diagnose the problem?

Well, it could be interesting to swap heads, and see whether the HW then
works ok but the CH doesn't. My hunch is that it won't make any difference.

Looking at your initial post, I suspect that there is *some* flow from the
boiler to the coil in the hot water cylinder, but not very much - which
might explain why the boiler only fires for a small percentage of the time
when trying to heat the HW. Are you *sure* that when the boiler stops, the
pump also stops? My hunch is that the boiler's own thermostat is turning
that off, but the pump is still running. Are the pipes which go the HW
cylinder hot under these circumstances? Is there a manual balancing valve in
the HW circuit which may be almost closed, preventing the necessary amount
of flow? Is there a bi-pass valve which could be stuck open,
short-circuiting the HW coil?

Finally, is it a vented system, or a sealed (pressurised) one?
--
Cheers,
Roger
______
Please reply to newsgroup.
Reply address IS valid, but not regularly monitored.

In an earlier contribution to this discussion,
Andrew wrote:

Summary so far: Honeywell S-Plan system. The problem started on its
own, not following any modifications or maintenance to the system. CH
works fine. When HW switched on alone without CH, boiler ignites and
pumps for a couple of mins only before turning off. It sometimes comes
back on after about 10 mins but only for 1 minute.

Switching on the CH and HW together and moving the HW motor valve to
Manual sometimes gets a full tank of water. But, sometimes when I try
this, the lever on the HW valve moves back to about half way across
and the valve is shut.

When HW only is on and the boiler is not doing anything, the pump is
not running. Tested with multimeter that the brown wire to the HW
valve is 240V with respect to neutral. The orange from the
microswitch is not live at this point. Moving the lever to manual
makes the boiler and pump active but literally for 1 second, before
dying.

Tested tank thermostat with multimeter. It switched fine between
terminals 1 and 2. Tank thermostat is set to 60 degrees, the boiler
stat is set to MAX. Can't see a manual balancing valve. The pipe on
the cylinder side of the motor valve is not hot when the HW is not
working. It's a flat so I can't be sure where all the vertical pipes
are actually going. Apart from the coil in and out, there are only 2
pipes to/from the cylinder fill at bottom and outgoing out from the
top of the cylinder - does that alone mean a sealed system?

We've been away from the house but the wife is now getting fed up with
using the immersion heater so I need to do something! :-)


One more plea! You've mastered quoting what you're replying to - but will
you now please put your response *below* the previous message, *not* above
it!

I suspect that the problem is down to the actuator on the HW valve. It
sounds as if the valve isn't opening properly under its own steam, and that
the manual lever doesn't open the valve far enough to operate the
microswitch reliably.

Have you tried swapping the heads? If you do that, and the HW then works but
the CH doesn't, it points fairly conclusively at the actuator.

If you don't want to do that, try this instead. Remove the HW actuator from
the valve. Turn the valve spindle manually to the open position. Check that
the spindle can be turned fairly easily. [If it is very stiff, the problem
may be that the 'wet' part of the valve is partially seized, and the
actuator is stalling before it's fully open]. At the point where the HW
actuator connects to the wiring centre, temporarily bridge the orange and
grey wires. If the boiler and pump then run properly and heat the hot water,
it proves that:
* the water circuit is not blocked or airlocked
* the boiler is ok when powered properly - so there must be a problem with
the actuator
[Don't leave it bridged while unattended, otherwise the HW may get *too*
hot].


Don't worry at this stage about whether it's a sealed or vented system. If
what I've suggested doesn't work, we may need to re-visit that in order to
investigate airlocks or low water level - but that's probably not necessary.
--
Cheers,
Roger
______
Email address maintained for newsgroup use only, and not regularly
monitored.. Messages sent to it may not be read for several weeks.
PLEASE REPLY TO NEWSGROUP!

Roger Mills wrote:
In an earlier contribution to this discussion,
Andrew wrote:

Summary so far: Honeywell S-Plan system. The problem started on its
own, not following any modifications or maintenance to the system. CH
works fine. When HW switched on alone without CH, boiler ignites and
pumps for a couple of mins only before turning off. It sometimes comes
back on after about 10 mins but only for 1 minute.

Switching on the CH and HW together and moving the HW motor valve to
Manual sometimes gets a full tank of water. But, sometimes when I try
this, the lever on the HW valve moves back to about half way across
and the valve is shut.

When HW only is on and the boiler is not doing anything, the pump is
not running. Tested with multimeter that the brown wire to the HW
valve is 240V with respect to neutral. The orange from the
microswitch is not live at this point. Moving the lever to manual
makes the boiler and pump active but literally for 1 second, before
dying.

Tested tank thermostat with multimeter. It switched fine between
terminals 1 and 2. Tank thermostat is set to 60 degrees, the boiler
stat is set to MAX. Can't see a manual balancing valve. The pipe on
the cylinder side of the motor valve is not hot when the HW is not
working. It's a flat so I can't be sure where all the vertical pipes
are actually going. Apart from the coil in and out, there are only 2
pipes to/from the cylinder fill at bottom and outgoing out from the
top of the cylinder - does that alone mean a sealed system?

We've been away from the house but the wife is now getting fed up with
using the immersion heater so I need to do something! :-)


One more plea! You've mastered quoting what you're replying to - but will
you now please put your response *below* the previous message, *not* above
it!

I suspect that the problem is down to the actuator on the HW valve. It
sounds as if the valve isn't opening properly under its own steam, and that
the manual lever doesn't open the valve far enough to operate the
microswitch reliably.

Have you tried swapping the heads? If you do that, and the HW then works but
the CH doesn't, it points fairly conclusively at the actuator.

If you don't want to do that, try this instead. Remove the HW actuator from
the valve. Turn the valve spindle manually to the open position. Check that
the spindle can be turned fairly easily. [If it is very stiff, the problem
may be that the 'wet' part of the valve is partially seized, and the
actuator is stalling before it's fully open]. At the point where the HW
actuator connects to the wiring centre, temporarily bridge the orange and
grey wires. If the boiler and pump then run properly and heat the hot water,
it proves that:
* the water circuit is not blocked or airlocked
* the boiler is ok when powered properly - so there must be a problem with
the actuator
[Don't leave it bridged while unattended, otherwise the HW may get *too*
hot].


Don't worry at this stage about whether it's a sealed or vented system. If
what I've suggested doesn't work, we may need to re-visit that in order to
investigate airlocks or low water level - but that's probably not necessary.
--
Cheers,
Roger
______
Email address maintained for newsgroup use only, and not regularly
monitored.. Messages sent to it may not be read for several weeks.
PLEASE REPLY TO NEWSGROUP!

The valve turned fine without the head on it so I ordered a new one and
replaced it. It works fine now. hooray

Thanks very much for all your help.

Regards,
Andrew

In an earlier contribution to this discussion,
Andrew wrote:


The valve turned fine without the head on it so I ordered a new one
and replaced it. It works fine now. hooray

Thanks very much for all your help.

Regards,
Andrew

Good result! Hopefully you've learned a bit in the process.
--
Cheers,
Roger
______
Email address maintained for newsgroup use only, and not regularly
monitored.. Messages sent to it may not be read for several weeks.
PLEASE REPLY TO NEWSGROUP!