Discussion:
Heating won't turn off - Potterton Profile
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decker
2008-12-03 20:35:51 UTC
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I have a strange issue with my central heating. Moved into a new house
3 years ago and heating worked fine for a year, then last winter we
had an issue where it wouldn't turn off.

We have a standard Gravity Fed System Setup
Potterton Profile (in garage)
Electronic Timer (in kitchen)
Thermostat (in Hall)
Zone Valve which switches between water and Heating (in airing
cupboard by water tank).

This is an intermittant problem and sometimes it doesn't happen for
weeks then happens everyday for 4 or 5 days its very hit annd miss and
unpredictable.

So when the heating reaches the correct temperature or you turn the
thermostat down the heating stays on, even if you turn the timer off
(for the Heating and Water). It just keeps running and the house gets
hotter and hotter.
We have to resort to flicking the main swich off so everything is
shutdown which is annoying.

I've had several things done to try and fix the problem but none has
worked:

1. replaced the Frost Stat in the garage (also bought a thermometer
that shows high and low temperature to see if it goes below the 5
degrees, and it doesn't).

2. Plumber suggested changeing the Zone value, so we did and this made
no difference.

I've had a plumber out and they don't know.

I could obviously replace the Timer and thermostat but then i'd have
change every part of the system, except the boiler.

Has anyone seen this issue before and have any suggestions to fix,
other than just replacing the boiler?

Regards
Stuart
PCPaul
2008-12-03 20:50:47 UTC
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Permalink
I have a strange issue with my central heating. Moved into a new house 3
years ago and heating worked fine for a year, then last winter we had an
issue where it wouldn't turn off.
We have a standard Gravity Fed System Setup Potterton Profile (in
garage)
Electronic Timer (in kitchen)
Thermostat (in Hall)
Zone Valve which switches between water and Heating (in airing cupboard
by water tank).
This is an intermittant problem and sometimes it doesn't happen for
weeks then happens everyday for 4 or 5 days its very hit annd miss and
unpredictable.
So when the heating reaches the correct temperature or you turn the
thermostat down the heating stays on, even if you turn the timer off
(for the Heating and Water). It just keeps running and the house gets
hotter and hotter.
We have to resort to flicking the main swich off so everything is
shutdown which is annoying.
I've had several things done to try and fix the problem but none has
1. replaced the Frost Stat in the garage (also bought a thermometer that
shows high and low temperature to see if it goes below the 5 degrees,
and it doesn't).
2. Plumber suggested changeing the Zone value, so we did and this made
no difference.
I've had a plumber out and they don't know.
I could obviously replace the Timer and thermostat but then i'd have
change every part of the system, except the boiler.
Has anyone seen this issue before and have any suggestions to fix, other
than just replacing the boiler?
Regards
Stuart
Got a multimeter? Happy with electrics? check to see if the stat actually
does stop calling for heat when it clicks - you can have the contacts
welded together but the bimetallic spring still clicking.

Check the frost stat calling as well while you're in there. Beware that
they use 240V for the switching, not nice safe logic levels :-(

Am I right in thinking that the system does go off when the timer tells
it to, it's just the temperature based switch off that fails?

TBH it sounds like the stat to me, well before I'd have suspected the
zone valve.

IANAP (I am not a Plumber!)
decker
2008-12-03 21:04:58 UTC
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Post by PCPaul
I have a strange issue with my central heating. Moved into a new house 3
years ago and heating worked fine for a year, then last winter we had an
issue where it wouldn't turn off.
We have a standard Gravity Fed System Setup Potterton Profile (in
garage)
Electronic Timer (in kitchen)
Thermostat (in Hall)
Zone Valve which switches between water and Heating (in airing cupboard
by water tank).
This is an intermittant problem and sometimes it doesn't happen for
weeks then happens everyday for 4 or 5 days its very hit annd miss and
unpredictable.
So when the heating reaches the correct temperature or you turn the
thermostat down the heating stays on, even if you turn the timer off
(for the Heating and Water). It just keeps running and the house gets
hotter and hotter.
We have to resort to flicking the main swich off so everything is
shutdown which is annoying.
I've had several things done to try and fix the problem but none has
1. replaced the Frost Stat in the garage (also bought a thermometer that
shows high and low temperature to see if it goes below the 5 degrees,
and it doesn't).
2. Plumber suggested changeing the Zone value, so we did and this made
no difference.
I've had a plumber out and they don't know.
I could obviously replace the Timer and thermostat but then i'd have
change every part of the system, except the boiler.
Has anyone seen this issue before and have any suggestions to fix, other
than just replacing the boiler?
Regards
Stuart
Got a multimeter? Happy with electrics? check to see if the stat actually
does stop calling for heat when it clicks - you can have the contacts
welded together but the bimetallic spring still clicking.
Check the frost stat calling as well while you're in there. Beware that
they use 240V for the switching, not nice safe logic levels :-(
Am I right in thinking that the system does go off when the timer tells
it to, it's just the temperature based switch off that fails?
TBH it sounds like the stat to me, well before I'd have suspected the
zone valve.
IANAP (I am not a Plumber!)
The heating stays on in both scenarios:
1) when you turn down the thermostat
2) and when the Timer/Controller is off (both Water and Heating off)

Thats what seems odd, I'm certainly no plumber but can't see the logic
of the boiler staying on and heating the radiators when the thermostat
and timer/controller is off.

The only way to turn is off the main on/off switch which shuts
everything down.

Regards
Stuart
Roger Mills
2008-12-03 22:16:03 UTC
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Permalink
In an earlier contribution to this discussion,
Post by decker
Post by PCPaul
Post by decker
I have a strange issue with my central heating. Moved into a new
house 3 years ago and heating worked fine for a year, then last
winter we had an issue where it wouldn't turn off.
We have a standard Gravity Fed System Setup Potterton Profile (in
garage)
Electronic Timer (in kitchen)
Thermostat (in Hall)
Zone Valve which switches between water and Heating (in airing
cupboard by water tank).
This is an intermittant problem and sometimes it doesn't happen for
weeks then happens everyday for 4 or 5 days its very hit annd miss
and unpredictable.
So when the heating reaches the correct temperature or you turn the
thermostat down the heating stays on, even if you turn the timer off
(for the Heating and Water). It just keeps running and the house
gets hotter and hotter.
We have to resort to flicking the main swich off so everything is
shutdown which is annoying.
I've had several things done to try and fix the problem but none has
1. replaced the Frost Stat in the garage (also bought a thermometer
that shows high and low temperature to see if it goes below the 5
degrees, and it doesn't).
2. Plumber suggested changeing the Zone value, so we did and this
made no difference.
I've had a plumber out and they don't know.
I could obviously replace the Timer and thermostat but then i'd have
change every part of the system, except the boiler.
Has anyone seen this issue before and have any suggestions to fix,
other than just replacing the boiler?
Regards
Stuart
Got a multimeter? Happy with electrics? check to see if the stat
actually does stop calling for heat when it clicks - you can have
the contacts welded together but the bimetallic spring still
clicking.
Check the frost stat calling as well while you're in there. Beware
that they use 240V for the switching, not nice safe logic levels :-(
Am I right in thinking that the system does go off when the timer
tells it to, it's just the temperature based switch off that fails?
TBH it sounds like the stat to me, well before I'd have suspected the
zone valve.
IANAP (I am not a Plumber!)
1) when you turn down the thermostat
2) and when the Timer/Controller is off (both Water and Heating off)
Thats what seems odd, I'm certainly no plumber but can't see the logic
of the boiler staying on and heating the radiators when the thermostat
and timer/controller is off.
The only way to turn is off the main on/off switch which shuts
everything down.
Regards
Stuart
Are you sure that there's only *one* zone valve - or are there two - one for
the HW and one for the CH?[1]

If there are two, you have what is called an S-Plan system - in which the
timer and stats drive the valves, and some auxilliary contacts in the valve
actuators - which close when the valve opens - drive the boiler and pump. If
a zone valve sticks open, these contacts continue to drive the boiler
regardless of what the timer and stats are doing. This would seem to fit
your symptoms.

[1] If there is only one valve, it will have 3 ports - one input and two
outputs. If there are two valves, each will have just two ports - an input
and an output, in line with each other.
--
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!
R D S
2008-12-03 21:00:53 UTC
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Post by decker
I have a strange issue with my central heating. Moved into a new house
3 years ago and heating worked fine for a year, then last winter we
had an issue where it wouldn't turn off.
I had something similar with a different type of heater.
I was told by the supplier (but never got around to it so dunno if it
would have worked) to surpress(?) the mains 'lead' near where it
connects within the heater by wrapping it around a ferrite ring.
BigWallop
2008-12-04 01:29:21 UTC
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Post by decker
I have a strange issue with my central heating. Moved into a new house
3 years ago and heating worked fine for a year, then last winter we
had an issue where it wouldn't turn off.
<<<snipped>>>
Post by decker
Has anyone seen this issue before and have any suggestions to fix,
other than just replacing the boiler?
Regards
Stuart
I take it that the plumber has tried removing one wire from the hall
thermostat? If not, try it. Leave it off until you are sure that the
boiler is not being told to fire because the 'stat is faulty. If you leave
it disconnected, it will not call for heating at all. Once you have tried
this, you'll know that the 'stat is not the problem. One down, not many to
go now.

Disconnect one wire from the timer / controller, preferably the wire that
feeds to the boiler live mains input. Leave it disconnected to make sure it
is not the controller that has gone faulty and is still calling for heat,
even when you think it is off. Two down, less bits to go.

Make sure that the controller is actually connected properly. The hall
thermostat and the zone valve should be connected in a loop, so that when
the 'stat opens, the valve has to close to tell the boiler to stop firing
up. This is also true with any water storage heating appliance with a
thermostat on it. Make sure they are connected in a loop wiring scheme with
the zone valve, so the zone is the only thing telling the boiler what to do,
and when to do it.

The wiring system should be connected in the following way.

Timer / Controller with live feed and neutral to make it work.

Switching in the controller for the heating system should be connected
through the hall thermostat, then on to the central heating connection of
the zone valve. From the valve it should be connected to the boiler to call
for heating.

Hot water switching in the controller should be connected through the
thermostat on the hot water cylinder, then on to the hot water side of the
zone valve. The valve switching is then connected to the boiler to call for
hot water.

This simple connection scheme makes it easier to diagnose faults with the
whole system. If the zone valve occurs a fault on the central heating
switching, the heating won't come on. Respectively, if the valve has a
fault on the hot water switching, the hot water don't work. If the hall
'stat has fault, the central heating will either stay on continually,
because the thermostat has stuck closed, or it won't come on at all because
the 'stat has stuck open. Again, this same fault occurrence on the hot
water 'stat shows the problem in the same way.

It sounds like you have a stuck thermostat or that two 'stats are fighting
with each other for the call to fire the boiler. When you say you have to
switch the whole lot off, it occurs to me that an automatic device on the
boiler is sticking in the closed (call) position until the power off cycle
resets it. So it is something that needs power on, to hold it closed
(calling for heat).

In this case, you have something that needs powered down to make it reset,
which could be the zone valve because it is wrongly connected into the
system. Or the controller switching is sticking closed (calling for heat)
because it is connected incorrectly or is being forced into fault condition
by some other wrongly connection scheme. It is simple to follow the
connections from either side of the controller. Look at where the wiring
goes from the controller to each of the devices, writing down how each
device is connected into the whole system. Check it against the wiring
scheme I have given above to make sure.

Remember that the electrician (whatever) will have used both, or maybe all
the cores in the cables to make his loop wiring. So following a brown wire
from the controller to the hall thermostat, will return from the hall 'stat
as a blue wire (assuming those colours have been used). But you get the
idea?

Good luck with your fault finding.
decker
2008-12-04 12:35:38 UTC
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Post by BigWallop
Post by decker
I have a strange issue with my central heating. Moved into a new house
3 years ago and heating worked fine for a year, then last winter we
had an issue where it wouldn't turn off.
<<<snipped>>>
Post by decker
Has anyone seen this issue before and have any suggestions to fix,
other than just replacing the boiler?
Regards
Stuart
I take it that the plumber has tried removing one wire from the hall
thermostat?  If not, try it.  Leave it off until you are sure that the
boiler is not being told to fire because the 'stat is faulty.  If you leave
it disconnected, it will not call for heating at all.  Once you have tried
this, you'll know that the 'stat is not the problem.  One down, not many to
go now.
Disconnect one wire from the timer / controller, preferably the wire that
feeds to the boiler live mains input.  Leave it disconnected to make sure it
is not the controller that has gone faulty and is still calling for heat,
even when you think it is off.  Two down, less bits to go.
Make sure that the controller is actually connected properly.  The hall
thermostat and the zone valve should be connected in a loop, so that when
the 'stat opens, the valve has to close to tell the boiler to stop firing
up.  This is also true with any water storage heating appliance with a
thermostat on it.  Make sure they are connected in a loop wiring scheme with
the zone valve, so the zone is the only thing telling the boiler what to do,
and when to do it.
The wiring system should be connected in the following way.
Timer / Controller with live feed and neutral to make it work.
Switching in the controller for the heating system should be connected
through the hall thermostat, then on to the central heating connection of
the zone valve.  From the valve it should be connected to the boiler to call
for heating.
Hot water switching in the controller should be connected through the
thermostat on the hot water cylinder, then on to the hot water side of the
zone valve.  The valve switching is then connected to the boiler to call for
hot water.
This simple connection scheme makes it easier to diagnose faults with the
whole system.  If the zone valve occurs a fault on the central heating
switching, the heating won't come on.  Respectively, if the valve has a
fault on the hot water switching, the hot water don't work.  If the hall
'stat has fault, the central heating will either stay on continually,
because the thermostat has stuck closed, or it won't come on at all because
the 'stat has stuck open.  Again, this same fault occurrence on the hot
water 'stat shows the problem in the same way.
It sounds like you have a stuck thermostat or that two 'stats are fighting
with each other for the call to fire the boiler.  When you say you have to
switch the whole lot off, it occurs to me that an automatic device on the
boiler is sticking in the closed (call) position until the power off cycle
resets it.  So it is something that needs power on, to hold it closed
(calling for heat).
In this case, you have something that needs powered down to make it reset,
which could be the zone valve because it is wrongly connected into the
system.  Or the controller switching is sticking closed (calling for heat)
because it is connected incorrectly or is being forced into fault condition
by some other wrongly connection scheme.  It is simple to follow the
connections from either side of the controller.  Look at where the wiring
goes from the controller to each of the devices, writing down how each
device is connected into the whole system.  Check it against the wiring
scheme I have given above to make sure.
Remember that the electrician (whatever) will have used both, or maybe all
the cores in the cables to make his loop wiring.  So following a brown wire
from the controller to the hall thermostat, will return from the hall 'stat
as a blue wire (assuming those colours have been used).  But you get the
idea?
Good luck with your fault finding.
Thanks everyobne for the info, I will certainly try some of them.

In answer to some of the comments:

<Roger> I'm 99% sure we only have 1 zone valve. The plumber has
already replaced this so i'm fairly confident that it should be
working OK, although there is a chance it has been connecte dup
incorrectly.

<BigWallop> Great suggestions I will try some. I am concerned that the
plumber didn' suggest any of these, although the issue was that you
could never get it into this faulty mode when the plumber was there,
as i've said it very intermitant (although it has been faulty for the
last week).
The power off, doesn't actually rectify the problem. It just enables
us to trun the heating off. For the last week the heating has been
faulty so we have been switching of the main power at night (so its
not running all night) and then turn it back on in the morning. The
wife has to remeber to switch the main switch off before going to work
otherwise there is a chance it will stay on all day.

This is half the battle, if you could initiate the fault at will it
would be easier for someone to fault find.

I think I may need to get someone else in who is interested in
resolving the issue, whereas the plumber I used seems to shrug his
shoulders without giving any ideas etc...

Thanks for your help.

Stuart
Roger
2008-12-04 12:28:22 UTC
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The message
Post by decker
Has anyone seen this issue before and have any suggestions to fix,
other than just replacing the boiler?
I tried to answer the question last night but eventually gave up through
uncertainty (which has not gone away).

I also have a Profile system but mine has several 2 port valves rather
than a 3 port and when it started behaving in a like manner earlier this
year it certainly was a zone valve microswitch that was sticking. But
Stuart says the valve has been replaced so if that includes the actuator
head then on the face of it a replacement valve being defective is
extremely unlikely. (But I don't know enough about 3 port valves to be
sure how faults manifest themselves).

Big could be right and the system really has two 2 port valves rather
than a 3 port but with a plumber in the loop is that likely to have been
overlooked?

I don't agree with Big that the thermostat is to blame, at least not
unless there is a double fault. If the setup is as described it is a
simple thermostat controlled by the timer so they would both have to be
faulty for the call for heat to get through when the control temperature
is exceeded.

For the moment I, like Stuart, remain completely baffled.
--
Roger Chapman
Roger
2008-12-04 13:56:55 UTC
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Permalink
The message
Post by decker
We have a standard Gravity Fed System Setup
Potterton Profile (in garage)
Electronic Timer (in kitchen)
Thermostat (in Hall)
Zone Valve which switches between water and Heating (in airing
cupboard by water tank).
Stuart

Couple of stray points.

You don't mention it but I presume you do have a thermostat on the hot
water tank.

What is the electronic timer? That might have some bearing on the
situation (but on the other hand might not).
--
Roger Chapman
decker
2008-12-04 22:07:51 UTC
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Permalink
Post by Roger
The message
Post by decker
We have a standard Gravity Fed System Setup
Potterton Profile (in garage)
Electronic Timer (in kitchen)
Thermostat (in Hall)
Zone Valve which switches between water and Heating (in airing
cupboard by water tank).
Stuart
Couple of stray points.
You don't mention it but I presume you do have a thermostat on the hot
water tank.
What is the electronic timer? That might have some bearing on the
situation (but on the other hand might not).
--
Roger Chapman
Roger,
The Programmer is a HorstMann (Channel Plus).
Yes there is a thermostat on the water tank, and oddly I checked the
temperature of the water coming out of the taps as it seemed
excessively hot (as the heating had been on for a while).
The water thermostat is set to about 54 but the temp of the water was
about 60 degrees so it appears it is not working.

I agree that if the thermostat was faulty then the Controller would
also need to be faulty as i'd expect both thermostats to be
deactivated if the controller was off but that is not whats happening.

Stuart
BigWallop
2008-12-04 22:35:32 UTC
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Post by decker
Post by Roger
The message
Post by decker
We have a standard Gravity Fed System Setup
Potterton Profile (in garage)
Electronic Timer (in kitchen)
Thermostat (in Hall)
Zone Valve which switches between water and Heating (in airing
cupboard by water tank).
Stuart
Couple of stray points.
You don't mention it but I presume you do have a thermostat on the hot
water tank.
What is the electronic timer? That might have some bearing on the
situation (but on the other hand might not).
--
Roger Chapman
Roger,
The Programmer is a HorstMann (Channel Plus).
Yes there is a thermostat on the water tank, and oddly I checked the
temperature of the water coming out of the taps as it seemed
excessively hot (as the heating had been on for a while).
The water thermostat is set to about 54 but the temp of the water was
about 60 degrees so it appears it is not working.
I agree that if the thermostat was faulty then the Controller would
also need to be faulty as i'd expect both thermostats to be
deactivated if the controller was off but that is not whats happening.
Stuart
If the system is wired from the controller to the thermostat and zone valve
in a parallel configuration, the hot water cylinder 'stat will keep calling
for the boiler to fire. This is wrong, and could be causing the problem you
are experiencing.

The wiring needs to be from the controller, through the hot water cylinder
'stat, through the zone valve and on to the boiler. That way, the boiler
only fires when both the hot water thermostat and zone valve have activated
correctly. If either zone valve or hot water 'stat show fault condition,
the boiler is not signalled to fire.

The same wiring configuration should be used for the central heating side of
the system. From controller to the hall thermostat, through the zone valve
and on to the boiler. The same effect is shown by not calling for heat at
the boiler, if either the hall 'stat or the central heating side of the zone
valve show fault condition.

It still sounds like a wiring fault, or that one of the switching points on
the thermostats of zone valve. You now seem to have found that the hot
water thermostat could be continually calling for hot water from the boiler.
But, are the zone valve and hot water 'stat being activated directly by the
controller, together or individually?
Roger
2008-12-05 08:35:05 UTC
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The message
Post by decker
The Programmer is a HorstMann (Channel Plus).
Not familiar with that. I presume it is a 2 channel programmer with
separate settings for CH and DHW.
Post by decker
Yes there is a thermostat on the water tank, and oddly I checked the
temperature of the water coming out of the taps as it seemed
excessively hot (as the heating had been on for a while).
The water thermostat is set to about 54 but the temp of the water was
about 60 degrees so it appears it is not working.
I agree that if the thermostat was faulty then the Controller would
also need to be faulty as i'd expect both thermostats to be
deactivated if the controller was off but that is not whats happening.
Stuart

As Big suggests it is not outwith the bounds of possibility that the
set-up has been wired up wrongly from inception.

If the tank thermostat had been wired up directly (say in parallel with
the frost stat) then you might not have noticed that the timer was
having no effect. It would be nowhere near as noticeable as central
heating without a timer.

If you alter the temperature setting on the stat you should hear a click
as it passes the set point even if there is no volts on the contacts.
If you can't hear a click it is very likely that the tank stat is
faulty.

How happy are you with meddling with mains wiring. If you disconnect the
tank thermostat and the problem goes away then you are on the right
track and circumstances should have proved that the timer is either
defective or not controlling the DHW.

Opening up the programmer and looking at the wiring should at least show
whether or not the domestic hot water channel has been wired up. That
might be the more sensible first step (after isolating the mains). That
way you might get an instant answer to the question of whether the
wiring is wrong.
--
Roger Chapman
Roger Mills
2008-12-05 19:13:23 UTC
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Permalink
In an earlier contribution to this discussion,
Post by Roger
How happy are you with meddling with mains wiring. If you disconnect
the tank thermostat and the problem goes away then you are on the
right track and circumstances should have proved that the timer is
either defective or not controlling the DHW.
Opening up the programmer and looking at the wiring should at least
show whether or not the domestic hot water channel has been wired up.
That might be the more sensible first step (after isolating the
mains). That way you might get an instant answer to the question of
whether the wiring is wrong.
Before the wiring can be checked sensibly, the OP needs to know what it
*should* be like - which in turn depends on the system configuration.

The OP *thinks* that there is only one zone valve - but hasn't yet confirmed
that there *is* only one, and that it has 3 ports.

[The sypmtoms sound to me much more like one of two 2-port valves stuck
open, rather than a 3-port valve problem].

Assuming that it *is* a single 3-port valve, it might be a diverter valve
(W-Plan) or a mid-position valve (Y-Plan) - and the wiring is substantially
different between these two options - and different again for an S-Plan
system with two 2-port valves.

May I suggest that the OP has a look at the Honeywell documents at
http://www.honeywelluk.com/article.aspx?ai=faq [1] in order to work out what
he's actually got, and then reports back here.

[1] Bollocks! Honeywell have changed their site, and the document I wanted
to reference ain't there any more. However, the reference I've given appears
to offer information about S, W and Y plans - once you've registered
--
Cheers,
Roger
______
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monitored.. Messages sent to it may not be read for several weeks.
PLEASE REPLY TO NEWSGROUP!
BigWallop
2008-12-05 19:29:26 UTC
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Post by Roger Mills
In an earlier contribution to this discussion,
Post by Roger
How happy are you with meddling with mains wiring. If you disconnect
the tank thermostat and the problem goes away then you are on the
right track and circumstances should have proved that the timer is
either defective or not controlling the DHW.
Opening up the programmer and looking at the wiring should at least
show whether or not the domestic hot water channel has been wired up.
That might be the more sensible first step (after isolating the
mains). That way you might get an instant answer to the question of
whether the wiring is wrong.
Before the wiring can be checked sensibly, the OP needs to know what it
*should* be like - which in turn depends on the system configuration.
The OP *thinks* that there is only one zone valve - but hasn't yet confirmed
that there *is* only one, and that it has 3 ports.
[The sypmtoms sound to me much more like one of two 2-port valves stuck
open, rather than a 3-port valve problem].
I think you'll find further up the thread, that it has been confirmed that
it "is" a 3 port valve on the system. Which has already been replaced by
the plumber.
Roger Mills
2008-12-06 00:13:49 UTC
Reply
Permalink
In an earlier contribution to this discussion,
Post by BigWallop
Post by Roger Mills
The OP *thinks* that there is only one zone valve - but hasn't yet
confirmed that there *is* only one, and that it has 3 ports.
[The sypmtoms sound to me much more like one of two 2-port valves
stuck open, rather than a 3-port valve problem].
I think you'll find further up the thread, that it has been confirmed
that it "is" a 3 port valve on the system. Which has already been
replaced by the plumber.
I don't think it's quite as explicit as that. I've just re-read the whole
thread - have you?

In the very first post, he only mentions one zone valve "which switches
between HW and CH". In a later post, he is "99% sure" there's only one
valve. At no time does he say how many ports it's got.

His description certainly *suggests* that it's a 3-port valve - quite likely
a diverter valve (W-Plan) rather than a mid-position valve (Y-Plan). However
there are other possibilities:
1. There could be another valve which he hasn't found, or
2. He *could* have a C-Plan system with gravity HW and pumped CH, with a
single 2-port valve which turns off the gravity circulation when the HW is
hot enough.

The problem is that none of these have any obvious failure modes which
continue to run the boiler when everything is turned off at the programmer -
which is why it's very important that we get to the bottom of what he's
actually got!
--
Cheers,
Roger
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monitored.. Messages sent to it may not be read for several weeks.
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Roger
2008-12-06 08:37:03 UTC
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Post by Roger Mills
2. He *could* have a C-Plan system with gravity HW and pumped CH, with a
single 2-port valve which turns off the gravity circulation when the HW is
hot enough.
I was a bit bothered by the use of 'gravity' in the original post but
translated that into open vent as my Profile installation instructions
say it is must only be used on "INDIRECT FULLY PUMPED systems". However
my Profile is described as a 'Profile Prima' and a vague memory from the
past suggests that there was a very similar boiler available which had 2
inlets and 2 outlets which presumably must have been intended for part
gravity installations. Unfortunately the advertising leaflet I have also
retained doesn't go into such detail so I don't know whether the other
boiler was also a Profile. What I do recall is that I originally set out
to buy the alternative back in Autumn 1991 but was persuaded to switch
by the retailer.

However even if the DHW is gravity circulation a 2 channel programmer
would need the 2 channels wired up separately with the programmer set so
the CH can't be used on its own.

Incidentally the installation instructions states:

"This appliance must be installed and serviced by a competent person as
stated in the Gas Safety (Installation and Use) Regulations 1984."

Funny how memory plays tricks. I would have sworn the regulations only
came in force shortly before I installed my boiler in 1991. 7 years is
hardly a short period. (Lifetime of a cheap modern boiler?)
--
Roger Chapman
Roger Mills
2008-12-06 23:00:27 UTC
Reply
Permalink
In an earlier contribution to this discussion,
Post by Roger
However even if the DHW is gravity circulation a 2 channel programmer
would need the 2 channels wired up separately with the programmer set
so the CH can't be used on its own.
In most cases, yes. *However* the C-Plan system is an exception to this
because it has a 2-port zone valve which cuts off the gravity circulation so
that you *can* have CH on its own.

[There used to be a diagram on the Honeywell site, showing how it works -
it's quite cunning! - but unfortunately, Honeywell have re-vamped their site
and the best I can find is
http://www.honeywelluk.com/product.aspx?r=ss&p=2388.]
--
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
2008-12-05 20:44:39 UTC
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Post by Roger Mills
Post by Roger
How happy are you with meddling with mains wiring. If you disconnect
the tank thermostat and the problem goes away then you are on the
right track and circumstances should have proved that the timer is
either defective or not controlling the DHW.
Opening up the programmer and looking at the wiring should at least
show whether or not the domestic hot water channel has been wired up.
That might be the more sensible first step (after isolating the
mains). That way you might get an instant answer to the question of
whether the wiring is wrong.
Before the wiring can be checked sensibly, the OP needs to know what it
*should* be like - which in turn depends on the system configuration.
That depends on the fault.

If the DHW channel on the programmer is not connected then a faulty tank
stat seems almost a certainty given what we have already been told. If
it is connected then it still could have been connected wrongly but the
investigation gets rather more difficult.
--
Roger Chapman
Cullie
2018-05-25 17:44:04 UTC
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Permalink
replying to decker, Cullie wrote:
I know it is 10 years ago but what was the problem, can you remember and how
was it solved?

--
for full context, visit https://www.homeownershub.com/uk-diy/heating-won-t-turn-off-potterton-profile-525400-.htm
t***@gmail.com
2018-05-25 18:38:31 UTC
Reply
Permalink
Post by Cullie
I know it is 10 years ago but what was the problem, can you remember and how
was it solved?
I suspect 'decker' is long gone. What do you reckon?

Come here via a more sensible portal and you won't be fed 10 yr old posts.


NT
Brian Gaff
2018-05-26 08:28:42 UTC
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With respect, I think they wanted to know the answer and all too often when
somebody does find a solution, they just do not take the minutes needed to
put it on the group, be it by a dodgy portal or not.
Brian
--
----- -
This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...
***@blueyonder.co.uk
Blind user, so no pictures please!
Post by t***@gmail.com
Post by Cullie
I know it is 10 years ago but what was the problem, can you remember and how
was it solved?
I suspect 'decker' is long gone. What do you reckon?
Come here via a more sensible portal and you won't be fed 10 yr old posts.
NT
t***@gmail.com
2018-05-26 19:30:30 UTC
Reply
Permalink
Post by Brian Gaff
Post by t***@gmail.com
Post by Cullie
I know it is 10 years ago but what was the problem, can you remember and how
was it solved?
I suspect 'decker' is long gone. What do you reckon?
Come here via a more sensible portal and you won't be fed 10 yr old posts.
NT
With respect, I think they wanted to know the answer
yes, that was in Cullie's question
Post by Brian Gaff
and all too often when
somebody does find a solution, they just do not take the minutes needed to
put it on the group, be it by a dodgy portal or not.
Brian
indeed. Keep up lad.


NT
Sev187
2021-10-13 22:31:20 UTC
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I have the same problem as was originally posted, however don’t know the valves involved in the system. The setup is the same as deckers and I have just started to experience the exact same problem with the heating being on, even with thermostat off or on low, controller switched off for CH and HW.

My basic understanding is, I have a potterman boiler in the garage, a water tank in the loft and a heater tank in the cupboard on 1st floor. I moved the property a year ago with no issues and haven’t needed CH for 6months and today when I turned it on, it wouldn’t turn off. After trying all the basic of hall thermostat, timer settings, boiler reset etc, I had to turn the boiler off at the mains in order to stop CH.
--
For full context, visit https://www.homeownershub.com/uk-diy/heating-won-t-turn-off-potterton-profile-525400-.htm
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