Hi,
Our central heating has just started misbehaving. Even though the
temperature near the downstairs thermostat is above that which should
start the central heating, whenever we run the hot water and the
bolier fires up to heat the hot water tank, the radiators also start
heating. Now I assume this must be the two way valve not closing off
the central heating. The light on the downstairs thermostat stays on
while the hot water is heating even if I turn the dial right down to
zero. Does anyone know if this could be just a faulty valve or could
it be something electrical in the controller. Has anyone any ideas,
please, before I have to get someone in to look at it.
Lawrie

"Lawrie Davidson" wrote in message
...
Hi,
Our central heating has just started misbehaving. Even though the
temperature near the downstairs thermostat is above that which should
start the central heating, whenever we run the hot water and the
bolier fires up to heat the hot water tank, the radiators also start
heating. Now I assume this must be the two way valve not closing off
the central heating. The light on the downstairs thermostat stays on
while the hot water is heating even if I turn the dial right down to
zero. Does anyone know if this could be just a faulty valve or could
it be something electrical in the controller. Has anyone any ideas,
please, before I have to get someone in to look at it.
Lawrie

Can you take the head off the two way valve, if so you will be able to see
if the actator is turning when you turn the room stat up/down and you can
also try turning the valve itself with a pair of pliers (don't force it
though as they can start to leak), been there and done it :-( . It's
probable that the valve itself has seized and that probably means draining
the system to change it.

However it would be useful if you can tell us exactly what make/model the
various 'bits' are.

Peter

"Lawrie Davidson" wrote in message
...
Hi,
Our central heating has just started misbehaving. Even though the
temperature near the downstairs thermostat is above that which should
start the central heating, whenever we run the hot water and the
bolier fires up to heat the hot water tank, the radiators also start
heating. Now I assume this must be the two way valve not closing off
the central heating. The light on the downstairs thermostat stays on
while the hot water is heating even if I turn the dial right down to
zero. Does anyone know if this could be just a faulty valve or could
it be something electrical in the controller. Has anyone any ideas,
please, before I have to get someone in to look at it.
Lawrie

If the thermostat is telling it to turn on then that is the first thing to
suspect. Sounds like the contacts are stuck together.

As for the valve, in my experience the mid position valve is not what gets
stuck but the microswitches in the actuator which get burnt out. However,
in your case it sounds like the thermostat.

Anyhow, if you have the normal type of timer selector it will be easy for
you to check if the valve or actuator are stuck in the mid position. Simply
turn off the CH side. This will override the wall thermostat, and you
should also hear the actuator driving the valve fully across to the HW only
position.
Your rads will then cool down unless the valve is either stuck in the mid
position or being held there by a faulty actuator.

If the rads do cool down then you have a faulty thermostat. (You might just
be able to take it down and clean the contacts - remembering to turn off the
power first...) If the thermostat (disconnected!) itself looks good and a
resistance meter shows you that it turns on and off when you wind the dial
back and forth: then it should work. Mind you, the dial may have slipped
round, so when you think it's set to 15 say, it might really be set to 25.
You do well to keep a thermometer nearby it as an extra means of
calibration.

If the rads don't cool down even when you have sorted out the problem with
the thermostat and its light is going on and off properly (ours doesn't have
a light but we can still hear it click and then the boiler start up if it's
working): then you may also have an actuator fault, but it would be quite
bad luck to have both at the same time.

A simple way to detect if your actuator is giving trouble, is to stick an fm
radio next to it, and then alternately run ch on its own, hw on its own, and
both together. Listen for the motor driving the valve back and forth with
each one you press. When the actuator is having trouble settling, due to
burnt or burning or wearing out contacts, the radio goes pop pop pop pop
pop. If it does not settle down after a short time and continues to
interfere with the radio, you need a new one (the switches inside can be
changed but in my experience it is very fiddly dealing with all the springs
and then fine tuning.).

Also, if you can get your hands to the outlet pipes from the valve, you can
feel if the heat is going down the rad pipe when it shouldn't, without
having to wait for the rads themselves.

Luckily it looks like yours is just the thermostat playing up.

S

"Lawrie Davidson" wrote in message
...
Hi,
Our central heating has just started misbehaving. Even though the
temperature near the downstairs thermostat is above that which should
start the central heating, whenever we run the hot water and the
bolier fires up to heat the hot water tank, the radiators also start
heating. Now I assume this must be the two way valve not closing off
the central heating. The light on the downstairs thermostat stays on
while the hot water is heating even if I turn the dial right down to
zero. Does anyone know if this could be just a faulty valve or could
it be something electrical in the controller. Has anyone any ideas,
please, before I have to get someone in to look at it.
Lawrie

I am surprised that there is a light on the room stat if you a calling for
HW only. A sticking mid position valve could cause this to happen.

Adam

"ARWadsworth" wrote in message
...

"Lawrie Davidson" wrote in message
...
Hi,
Our central heating has just started misbehaving. Even though the
temperature near the downstairs thermostat is above that which should
start the central heating, whenever we run the hot water and the
bolier fires up to heat the hot water tank, the radiators also start
heating. Now I assume this must be the two way valve not closing off
the central heating. The light on the downstairs thermostat stays on
while the hot water is heating even if I turn the dial right down to
zero. Does anyone know if this could be just a faulty valve or could
it be something electrical in the controller. Has anyone any ideas,
please, before I have to get someone in to look at it.
Lawrie

I am surprised that there is a light on the room stat if you a calling for
HW only. A sticking mid position valve could cause this to happen.

Adam

How?
What's it got to do with the thermostat? all it does is override the CH
switch: and if the light says it's on then it obviously isn't overriding it!
For this to be a sticking valve or actuator the rads would have to be hot
when all the switches were off: not when one of them is clearly indicating
that it is on!

S

"spamlet" wrote in message
...

"ARWadsworth" wrote in message
...

"Lawrie Davidson" wrote in message
...
Hi,
Our central heating has just started misbehaving. Even though the
temperature near the downstairs thermostat is above that which should
start the central heating, whenever we run the hot water and the
bolier fires up to heat the hot water tank, the radiators also start
heating. Now I assume this must be the two way valve not closing off
the central heating. The light on the downstairs thermostat stays on
while the hot water is heating even if I turn the dial right down to
zero. Does anyone know if this could be just a faulty valve or could
it be something electrical in the controller. Has anyone any ideas,
please, before I have to get someone in to look at it.
Lawrie

I am surprised that there is a light on the room stat if you a calling
for HW only. A sticking mid position valve could cause this to happen.

Adam

How?
What's it got to do with the thermostat? all it does is override the CH
switch: and if the light says it's on then it obviously isn't overriding
it! For this to be a sticking valve or actuator the rads would have to be
hot when all the switches were off: not when one of them is clearly
indicating that it is on!

S

A stuck mid position valve is a very common problem. One of the main failure
modes is that the CH comes on when only HW is called for. This occurs when
the valve is stuck just after the mid position and both internal
microswitches have operated. If the valve is stuck in such a position then
calling for hot water will heat up the radiators as well as the HW.

The big clue is that there is a light showing on the room stat when the CH
is not being called for but HW is being called. This suggests that the
internal switch 2 of the mid position valve has operated (or has broken) and
the HW signal is backfeeding through the mid position valve via the white
wire to the room stat.

Adam

"ARWadsworth" wrote in message
...

"spamlet" wrote in message
...

"ARWadsworth" wrote in message
...

"Lawrie Davidson" wrote in message
...
Hi,
Our central heating has just started misbehaving. Even though the
temperature near the downstairs thermostat is above that which should
start the central heating, whenever we run the hot water and the
bolier fires up to heat the hot water tank, the radiators also start
heating. Now I assume this must be the two way valve not closing off
the central heating. The light on the downstairs thermostat stays on
while the hot water is heating even if I turn the dial right down to
zero. Does anyone know if this could be just a faulty valve or could
it be something electrical in the controller. Has anyone any ideas,
please, before I have to get someone in to look at it.
Lawrie

I am surprised that there is a light on the room stat if you a calling
for HW only. A sticking mid position valve could cause this to happen.

Adam

How?
What's it got to do with the thermostat? all it does is override the CH
switch: and if the light says it's on then it obviously isn't overriding
it! For this to be a sticking valve or actuator the rads would have to be
hot when all the switches were off: not when one of them is clearly
indicating that it is on!

S

A stuck mid position valve is a very common problem. One of the main
failure modes is that the CH comes on when only HW is called for. This
occurs when the valve is stuck just after the mid position and both
internal microswitches have operated. If the valve is stuck in such a
position then calling for hot water will heat up the radiators as well as
the HW.

The big clue is that there is a light showing on the room stat when the CH
is not being called for but HW is being called. This suggests that the
internal switch 2 of the mid position valve has operated (or has broken)
and the HW signal is backfeeding through the mid position valve via the
white wire to the room stat.

Adam

Well I certainly concur with the crap nature of the internal switches in the
actuators, as I've replaced three sets myself - and in units that can cost
£60 a time this is pretty disgraceful performance. Anyhow, our room
thermostat doesn't work like that, and it seems completely unnecessary for
current to flow through it when it's contacts are open - unless the light is
to tell you that the heating *isn't* on, which seems daft to me.

S

"spamlet" wrote in message
...

"ARWadsworth" wrote in message
...

"spamlet" wrote in message
...

"ARWadsworth" wrote in message
...

"Lawrie Davidson" wrote in message
...
Hi,
Our central heating has just started misbehaving. Even though the
temperature near the downstairs thermostat is above that which should
start the central heating, whenever we run the hot water and the
bolier fires up to heat the hot water tank, the radiators also start
heating. Now I assume this must be the two way valve not closing off
the central heating. The light on the downstairs thermostat stays on
while the hot water is heating even if I turn the dial right down to
zero. Does anyone know if this could be just a faulty valve or could
it be something electrical in the controller. Has anyone any ideas,
please, before I have to get someone in to look at it.
Lawrie

I am surprised that there is a light on the room stat if you a calling
for HW only. A sticking mid position valve could cause this to happen.

Adam

How?
What's it got to do with the thermostat? all it does is override the CH
switch: and if the light says it's on then it obviously isn't overriding
it! For this to be a sticking valve or actuator the rads would have to
be hot when all the switches were off: not when one of them is clearly
indicating that it is on!

S

A stuck mid position valve is a very common problem. One of the main
failure modes is that the CH comes on when only HW is called for. This
occurs when the valve is stuck just after the mid position and both
internal microswitches have operated. If the valve is stuck in such a
position then calling for hot water will heat up the radiators as well as
the HW.

The big clue is that there is a light showing on the room stat when the
CH is not being called for but HW is being called. This suggests that
the internal switch 2 of the mid position valve has operated (or has
broken) and the HW signal is backfeeding through the mid position valve
via the white wire to the room stat.

Adam

Well I certainly concur with the crap nature of the internal switches in
the actuators, as I've replaced three sets myself - and in units that can
cost £60 a time this is pretty disgraceful performance. Anyhow, our room
thermostat doesn't work like that, and it seems completely unnecessary
for current to flow through it when it's contacts are open - unless the
light is to tell you that the heating *isn't* on, which seems daft to me.

S

I'll bet your room stat does operate like that if you back feed a voltage.

You have 3 terminals at your roomstat. Live in, Call for heat and neutral.
If the call for heat terminal is made live due to a faulty 3 port valve back
feeding a voltage to it then the neon in your thermostat (which is across
the call for heat and neutral) will light up when HW is called for and thius
will not turn off whatever the setting on the room stat.

Adam

"ARWadsworth" wrote in message
...

"spamlet" wrote in message
...

"ARWadsworth" wrote in message
...

"spamlet" wrote in message
...

"ARWadsworth" wrote in message
...

"Lawrie Davidson" wrote in message
...
Hi,
Our central heating has just started misbehaving. Even though the
temperature near the downstairs thermostat is above that which should
start the central heating, whenever we run the hot water and the
bolier fires up to heat the hot water tank, the radiators also start
heating. Now I assume this must be the two way valve not closing off
the central heating. The light on the downstairs thermostat stays on
while the hot water is heating even if I turn the dial right down to
zero. Does anyone know if this could be just a faulty valve or could
it be something electrical in the controller. Has anyone any ideas,
please, before I have to get someone in to look at it.
Lawrie

I am surprised that there is a light on the room stat if you a calling
for HW only. A sticking mid position valve could cause this to happen.

Adam

How?
What's it got to do with the thermostat? all it does is override the
CH switch: and if the light says it's on then it obviously isn't
overriding it! For this to be a sticking valve or actuator the rads
would have to be hot when all the switches were off: not when one of
them is clearly indicating that it is on!

S

A stuck mid position valve is a very common problem. One of the main
failure modes is that the CH comes on when only HW is called for. This
occurs when the valve is stuck just after the mid position and both
internal microswitches have operated. If the valve is stuck in such a
position then calling for hot water will heat up the radiators as well
as the HW.

The big clue is that there is a light showing on the room stat when the
CH is not being called for but HW is being called. This suggests that
the internal switch 2 of the mid position valve has operated (or has
broken) and the HW signal is backfeeding through the mid position valve
via the white wire to the room stat.

Adam

Well I certainly concur with the crap nature of the internal switches in
the actuators, as I've replaced three sets myself - and in units that can
cost £60 a time this is pretty disgraceful performance. Anyhow, our room
thermostat doesn't work like that, and it seems completely unnecessary
for current to flow through it when it's contacts are open - unless the
light is to tell you that the heating *isn't* on, which seems daft to me.

S

I'll bet your room stat does operate like that if you back feed a voltage.

You have 3 terminals at your roomstat. Live in, Call for heat and neutral.
If the call for heat terminal is made live due to a faulty 3 port valve
back feeding a voltage to it then the neon in your thermostat (which is
across the call for heat and neutral) will light up when HW is called for
and thius will not turn off whatever the setting on the room stat.

No: as I would expect a thermostat to be, my Servowarm has an in an out and
an earth and no neon. (Just as is shown in the uk-diy faq in fact:
http://wiki.diyfaq.org.uk/index.php?...nSchematic.gif ) And
if it did need a neon I would put it on the controller side of the contacts:
not on the side of a subsidiary circuit that could feed back false
information.
It cannot 'call for heat' unless it is both powered up by the main selector
switch, and the temperature has closed its contacts. It is just a switch,
and when it is off there is nowhere for any 'back feeding voltage' to go.
Which, as your design seems to make it difficult to distinguish between a
thermostat fault and an actuator fault, I'm very glad to have my version!

S

"spamlet" wrote in message
...

"ARWadsworth" wrote in message
...

"spamlet" wrote in message
...

"ARWadsworth" wrote in message
...

"spamlet" wrote in message
...

"ARWadsworth" wrote in message
...

"Lawrie Davidson" wrote in message
...
Hi,
Our central heating has just started misbehaving. Even though the
temperature near the downstairs thermostat is above that which
should
start the central heating, whenever we run the hot water and the
bolier fires up to heat the hot water tank, the radiators also start
heating. Now I assume this must be the two way valve not closing off
the central heating. The light on the downstairs thermostat stays on
while the hot water is heating even if I turn the dial right down to
zero. Does anyone know if this could be just a faulty valve or could
it be something electrical in the controller. Has anyone any ideas,
please, before I have to get someone in to look at it.
Lawrie

I am surprised that there is a light on the room stat if you a
calling
for HW only. A sticking mid position valve could cause this to
happen.

Adam

How?
What's it got to do with the thermostat? all it does is override the
CH switch: and if the light says it's on then it obviously isn't
overriding it! For this to be a sticking valve or actuator the rads
would have to be hot when all the switches were off: not when one of
them is clearly indicating that it is on!

S

A stuck mid position valve is a very common problem. One of the main
failure modes is that the CH comes on when only HW is called for. This
occurs when the valve is stuck just after the mid position and both
internal microswitches have operated. If the valve is stuck in such a
position then calling for hot water will heat up the radiators as well
as the HW.

The big clue is that there is a light showing on the room stat when the
CH is not being called for but HW is being called. This suggests that
the internal switch 2 of the mid position valve has operated (or has
broken) and the HW signal is backfeeding through the mid position valve
via the white wire to the room stat.

Adam

Well I certainly concur with the crap nature of the internal switches in
the actuators, as I've replaced three sets myself - and in units that
can
cost £60 a time this is pretty disgraceful performance. Anyhow, our
room
thermostat doesn't work like that, and it seems completely unnecessary
for current to flow through it when it's contacts are open - unless the
light is to tell you that the heating *isn't* on, which seems daft to
me.

S

I'll bet your room stat does operate like that if you back feed a
voltage.

You have 3 terminals at your roomstat. Live in, Call for heat and
neutral.
If the call for heat terminal is made live due to a faulty 3 port valve
back feeding a voltage to it then the neon in your thermostat (which is
across the call for heat and neutral) will light up when HW is called for
and thius will not turn off whatever the setting on the room stat.

No: as I would expect a thermostat to be, my Servowarm has an in an out
and
an earth and no neon. (Just as is shown in the uk-diy faq in fact:
http://wiki.diyfaq.org.uk/index.php?...nSchematic.gif ) And
if it did need a neon I would put it on the controller side of the
contacts: not on the side of a subsidiary circuit that could feed back
false information.
It cannot 'call for heat' unless it is both powered up by the main
selector switch, and the temperature has closed its contacts. It is just
a switch, and when it is off there is nowhere for any 'back feeding
voltage' to go. Which, as your design seems to make it difficult to
distinguish between a thermostat fault and an actuator fault, I'm very
glad to have my version!

S

You have a cheap thermostat:-) The best ones require a neutral connection.

The OP on the the other hand does have a light on their room stat. That is
all the info that is needed to diagnose a stuck mid position valve.

Adam

"ARWadsworth" wrote in message
...

"spamlet" wrote in message
...

"ARWadsworth" wrote in message
...

"spamlet" wrote in message
...

"ARWadsworth" wrote in message
...

"spamlet" wrote in message
...

"ARWadsworth" wrote in message
...

"Lawrie Davidson" wrote in message
...
Hi,
Our central heating has just started misbehaving. Even though the
temperature near the downstairs thermostat is above that which
should
start the central heating, whenever we run the hot water and the
bolier fires up to heat the hot water tank, the radiators also
start
heating. Now I assume this must be the two way valve not closing
off
the central heating. The light on the downstairs thermostat stays
on
while the hot water is heating even if I turn the dial right down
to
zero. Does anyone know if this could be just a faulty valve or
could
it be something electrical in the controller. Has anyone any ideas,
please, before I have to get someone in to look at it.
Lawrie

I am surprised that there is a light on the room stat if you a
calling
for HW only. A sticking mid position valve could cause this to
happen.

Adam

How?
What's it got to do with the thermostat? all it does is override the
CH switch: and if the light says it's on then it obviously isn't
overriding it! For this to be a sticking valve or actuator the rads
would have to be hot when all the switches were off: not when one of
them is clearly indicating that it is on!

S

A stuck mid position valve is a very common problem. One of the main
failure modes is that the CH comes on when only HW is called for. This
occurs when the valve is stuck just after the mid position and both
internal microswitches have operated. If the valve is stuck in such a
position then calling for hot water will heat up the radiators as well
as the HW.

The big clue is that there is a light showing on the room stat when
the
CH is not being called for but HW is being called. This suggests that
the internal switch 2 of the mid position valve has operated (or has
broken) and the HW signal is backfeeding through the mid position
valve
via the white wire to the room stat.

Adam

Well I certainly concur with the crap nature of the internal switches
in
the actuators, as I've replaced three sets myself - and in units that
can
cost £60 a time this is pretty disgraceful performance. Anyhow, our
room
thermostat doesn't work like that, and it seems completely unnecessary
for current to flow through it when it's contacts are open - unless the
light is to tell you that the heating *isn't* on, which seems daft to
me.

S

I'll bet your room stat does operate like that if you back feed a
voltage.

You have 3 terminals at your roomstat. Live in, Call for heat and
neutral.
If the call for heat terminal is made live due to a faulty 3 port valve
back feeding a voltage to it then the neon in your thermostat (which is
across the call for heat and neutral) will light up when HW is called
for
and thius will not turn off whatever the setting on the room stat.

No: as I would expect a thermostat to be, my Servowarm has an in an out
and
an earth and no neon. (Just as is shown in the uk-diy faq in fact:
http://wiki.diyfaq.org.uk/index.php?...nSchematic.gif ) And
if it did need a neon I would put it on the controller side of the
contacts: not on the side of a subsidiary circuit that could feed back
false information.
It cannot 'call for heat' unless it is both powered up by the main
selector switch, and the temperature has closed its contacts. It is just
a switch, and when it is off there is nowhere for any 'back feeding
voltage' to go. Which, as your design seems to make it difficult to
distinguish between a thermostat fault and an actuator fault, I'm very
glad to have my version!

S

You have a cheap thermostat:-) The best ones require a neutral connection.

The OP on the the other hand does have a light on their room stat. That is
all the info that is needed to diagnose a stuck mid position valve.

Adam

"ARWadsworth" wrote in message
...

"spamlet" wrote in message
...

"ARWadsworth" wrote in message
...

"spamlet" wrote in message
...

"ARWadsworth" wrote in message
...

"spamlet" wrote in message
...

"ARWadsworth" wrote in message
...

"Lawrie Davidson" wrote in message
...
Hi,
Our central heating has just started misbehaving. Even though the
temperature near the downstairs thermostat is above that which
should
start the central heating, whenever we run the hot water and the
bolier fires up to heat the hot water tank, the radiators also
start
heating. Now I assume this must be the two way valve not closing
off
the central heating. The light on the downstairs thermostat stays
on
while the hot water is heating even if I turn the dial right down
to
zero. Does anyone know if this could be just a faulty valve or
could
it be something electrical in the controller. Has anyone any ideas,
please, before I have to get someone in to look at it.
Lawrie

I am surprised that there is a light on the room stat if you a
calling
for HW only. A sticking mid position valve could cause this to
happen.

Adam

How?
What's it got to do with the thermostat? all it does is override the
CH switch: and if the light says it's on then it obviously isn't
overriding it! For this to be a sticking valve or actuator the rads
would have to be hot when all the switches were off: not when one of
them is clearly indicating that it is on!

S

A stuck mid position valve is a very common problem. One of the main
failure modes is that the CH comes on when only HW is called for. This
occurs when the valve is stuck just after the mid position and both
internal microswitches have operated. If the valve is stuck in such a
position then calling for hot water will heat up the radiators as well
as the HW.

The big clue is that there is a light showing on the room stat when
the
CH is not being called for but HW is being called. This suggests that
the internal switch 2 of the mid position valve has operated (or has
broken) and the HW signal is backfeeding through the mid position
valve
via the white wire to the room stat.

Adam

Well I certainly concur with the crap nature of the internal switches
in
the actuators, as I've replaced three sets myself - and in units that
can
cost £60 a time this is pretty disgraceful performance. Anyhow, our
room
thermostat doesn't work like that, and it seems completely unnecessary
for current to flow through it when it's contacts are open - unless the
light is to tell you that the heating *isn't* on, which seems daft to
me.

S

I'll bet your room stat does operate like that if you back feed a
voltage.

You have 3 terminals at your roomstat. Live in, Call for heat and
neutral.
If the call for heat terminal is made live due to a faulty 3 port valve
back feeding a voltage to it then the neon in your thermostat (which is
across the call for heat and neutral) will light up when HW is called
for
and thius will not turn off whatever the setting on the room stat.

No: as I would expect a thermostat to be, my Servowarm has an in an out
and
an earth and no neon. (Just as is shown in the uk-diy faq in fact:
http://wiki.diyfaq.org.uk/index.php?...nSchematic.gif ) And
if it did need a neon I would put it on the controller side of the
contacts: not on the side of a subsidiary circuit that could feed back
false information.
It cannot 'call for heat' unless it is both powered up by the main
selector switch, and the temperature has closed its contacts. It is just
a switch, and when it is off there is nowhere for any 'back feeding
voltage' to go. Which, as your design seems to make it difficult to
distinguish between a thermostat fault and an actuator fault, I'm very
glad to have my version!

S

You have a cheap thermostat:-) The best ones require a neutral connection.

The OP on the the other hand does have a light on their room stat. That is
all the info that is needed to diagnose a stuck mid position valve.

No: all that is needed to determine a stuck valve or actuator, is to turn
off the CH and see if the rads come on when the hot water is on. Your neon
or heater resistor is just one more thing to go wrong.

S