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UK diy (uk.d-i-y) For the discussion of all topics related to diy (do-it-yourself) in the UK. All levels of experience and proficency are welcome to join in to ask questions or offer solutions.

Central heating won't turn off



 
 
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  #1  
Old November 21st 11, 04:11 PM posted to uk.d-i-y
external usenet poster
 
Posts: 7
Default Central heating won't turn off

OK, I know other people have had this problem and have done a cursory Google
search, but have not been able to shed much light on what might be the
problem in my particular case.

Basically, the central heating round at my parents house refuses to switch
off, even when the thermostats aren't calling for heat and the timer is off.
The pump continues to run and the boiler continues to heat the water and the
only way to get it to switch off is to turn everything off at the mains.

I suspected it might have been a stuck 2-port valve, but having checked both
of these found that neither one (CH or DHW) were stuck and appeared to be
operating fine.

Their set up is a standard Gravity Fed System with the feed and expansion
tank in the loft.
Glow Worm hideaway boiler (in a small room next to the kitchen)
Danfoss Electronic Timer (in the kitchen)
Danfoss Room Thermostat (in the Hall)
2x Danfoss 2-port valves (for CH & DHW - in Airing cupboard next to hot
water cylinder)
Danfoss cylinder stat (in airing cupboard)
CH pump (unsure of make - in the airing cupboard)

Again, the 2-port valves were most definitely not jammed open, which was my
first guess. In fact when I went round there to check them, I found my
mother had switched the gas off on the boiler (it didn't occur to her to
switch off the power supply), the timer was off, both 2-port valves were
closed, but the pump was still running?

Any suggestions what to try next?

Thanks in advance.


--
Best Wishes
Simon (Dark Angel)
http://www.realmofhorror.co.uk
http://www.facebook.com/pages/Realm-...43030832454357

..


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  #2  
Old November 21st 11, 04:48 PM posted to uk.d-i-y
external usenet poster
 
Posts: 7,702
Default Central heating won't turn off

Simon T wrote:
OK, I know other people have had this problem and have done a cursory
Google search, but have not been able to shed much light on what
might be the problem in my particular case.

Basically, the central heating round at my parents house refuses to
switch off, even when the thermostats aren't calling for heat and the
timer is off. The pump continues to run and the boiler continues to
heat the water and the only way to get it to switch off is to turn
everything off at the mains.
I suspected it might have been a stuck 2-port valve, but having
checked both of these found that neither one (CH or DHW) were stuck
and appeared to be operating fine.

Their set up is a standard Gravity Fed System with the feed and
expansion tank in the loft.
Glow Worm hideaway boiler (in a small room next to the kitchen)
Danfoss Electronic Timer (in the kitchen)
Danfoss Room Thermostat (in the Hall)
2x Danfoss 2-port valves (for CH & DHW - in Airing cupboard next to
hot water cylinder)
Danfoss cylinder stat (in airing cupboard)
CH pump (unsure of make - in the airing cupboard)

Again, the 2-port valves were most definitely not jammed open, which
was my first guess. In fact when I went round there to check them, I
found my mother had switched the gas off on the boiler (it didn't
occur to her to switch off the power supply), the timer was off, both
2-port valves were closed, but the pump was still running?

Any suggestions what to try next?


Have you got a multimeter and do you know how to use one?


--
Adam

* Sometimes I like to lay in my neighbours garden and pretend to be a
carrot *


  #3  
Old November 21st 11, 04:49 PM posted to uk.d-i-y
external usenet poster
 
Posts: 55
Default Central heating won't turn off

On Nov 21, 4:11*pm, "Simon T" wrote:
OK, I know other people have had this problem and have done a cursory Google
search, but have not been able to shed much light on what might be the
problem in my particular case.

Basically, the central heating round at my parents house refuses to switch
off, even when the thermostats aren't calling for heat and the timer is off.
The pump continues to run and the boiler continues to heat the water and the
only way to get it to switch off is to turn everything off at the mains.

I suspected it might have been a stuck 2-port valve, but having checked both
of these found that neither one (CH or DHW) were stuck and appeared to be
operating fine.

Their set up is a standard Gravity Fed System with the feed and expansion
tank in the loft.
Glow Worm hideaway boiler (in a small room next to the kitchen)
Danfoss Electronic Timer (in the kitchen)
Danfoss Room Thermostat (in the Hall)
2x Danfoss 2-port valves (for CH & DHW - in Airing cupboard next to hot
water cylinder)
Danfoss cylinder stat (in airing cupboard)
CH pump (unsure of make - in the airing cupboard)

Again, the 2-port valves were most definitely not jammed open, which was my
first guess. In fact when I went round there to check them, I found my
mother had switched the gas off on the boiler (it didn't occur to her to
switch off the power supply), the timer was off, both 2-port valves were
closed, but the pump was still running?


The valves might be closing mechanically, but not electrically - the
resistance across brown/orange should be infinite (i.e. open circuit)
when the valve is closed. That still shouldn't cause the pump to run
though, without some other problem!

Take a look he

http://wiki.diyfaq.org.uk/index.php?...s_and_Zonin g

And get a multimeter out and start seeing where reality diverges from
what you expect.




However, even if the valve is faulty, if the timer is off then the
pump should still be off, so you either have a wiring fault or a timer
which is lying to you.

I would start by
  #4  
Old November 21st 11, 04:59 PM posted to uk.d-i-y
external usenet poster
 
Posts: 90
Default Central heating won't turn off

On 21/11/2011 16:11, Simon T wrote:
OK, I know other people have had this problem and have done a cursory
Google search, but have not been able to shed much light on what might
be the problem in my particular case.

Basically, the central heating round at my parents house refuses to
switch off, even when the thermostats aren't calling for heat and the
timer is off. The pump continues to run and the boiler continues to heat
the water and the only way to get it to switch off is to turn everything
off at the mains.

I suspected it might have been a stuck 2-port valve, but having checked
both of these found that neither one (CH or DHW) were stuck and appeared
to be operating fine.

Their set up is a standard Gravity Fed System with the feed and
expansion tank in the loft.
Glow Worm hideaway boiler (in a small room next to the kitchen)
Danfoss Electronic Timer (in the kitchen)
Danfoss Room Thermostat (in the Hall)
2x Danfoss 2-port valves (for CH & DHW - in Airing cupboard next to hot
water cylinder)
Danfoss cylinder stat (in airing cupboard)
CH pump (unsure of make - in the airing cupboard)

Again, the 2-port valves were most definitely not jammed open, which was
my first guess. In fact when I went round there to check them, I found
my mother had switched the gas off on the boiler (it didn't occur to her
to switch off the power supply), the timer was off, both 2-port valves
were closed, but the pump was still running?

Any suggestions what to try next?

Thanks in advance.


Is the thermostat wired or wireless?

Pete
  #5  
Old November 21st 11, 05:42 PM posted to uk.d-i-y
external usenet poster
 
Posts: 7
Default Central heating won't turn off

"Pete Shew" wrote in message ...
Is the thermostat wired or wireless?


Wired


--
Best Wishes
Simon (Dark Angel)
http://www.realmofhorror.co.uk
http://www.facebook.com/pages/Realm-...43030832454357
  #6  
Old November 21st 11, 05:44 PM posted to uk.d-i-y
external usenet poster
 
Posts: 7
Default Central heating won't turn off

"ARWadsworth" wrote in message...
Have you got a multimeter and do you know how to use one?


Yes to both!


--
Best Wishes
Simon (Dark Angel)
http://www.realmofhorror.co.uk
http://www.facebook.com/pages/Realm-...43030832454357
  #7  
Old November 21st 11, 06:18 PM posted to uk.d-i-y
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Posts: 1,081
Default Central heating won't turn off

On 21/11/2011 16:11, Simon T wrote:

I suspected it might have been a stuck 2-port valve, but having checked
both of these found that neither one (CH or DHW) were stuck and appeared
to be operating fine.


The micro-switch on a 2 port valve could be stuck closed even though the
valve itself had closed which action should have opened the micro-switch
contacts.

--
Roger Chapman
  #8  
Old November 21st 11, 07:38 PM posted to uk.d-i-y
external usenet poster
 
Posts: 2,168
Default Central heating won't turn off

On 21/11/2011 16:11, Simon T wrote:
OK, I know other people have had this problem and have done a cursory
Google search, but have not been able to shed much light on what might
be the problem in my particular case.

Basically, the central heating round at my parents house refuses to
switch off, even when the thermostats aren't calling for heat and the
timer is off. The pump continues to run and the boiler continues to heat
the water and the only way to get it to switch off is to turn everything
off at the mains.

I suspected it might have been a stuck 2-port valve, but having checked
both of these found that neither one (CH or DHW) were stuck and appeared
to be operating fine.

Their set up is a standard Gravity Fed System with the feed and
expansion tank in the loft.
Glow Worm hideaway boiler (in a small room next to the kitchen)
Danfoss Electronic Timer (in the kitchen)
Danfoss Room Thermostat (in the Hall)
2x Danfoss 2-port valves (for CH & DHW - in Airing cupboard next to hot
water cylinder)
Danfoss cylinder stat (in airing cupboard)
CH pump (unsure of make - in the airing cupboard)

Again, the 2-port valves were most definitely not jammed open, which was
my first guess. In fact when I went round there to check them, I found
my mother had switched the gas off on the boiler (it didn't occur to her
to switch off the power supply), the timer was off, both 2-port valves
were closed, but the pump was still running?

Any suggestions what to try next?

Thanks in advance.


Each of the zone valves has an auxiliary switch which closes when the
valve is open, and is independent of the motor circuit. These switches
on the two valves are wired in parallel - with a permanent live feed on
the grey wires and a switched live (which switches on the boiler and
pump) on the orange wires.

It's almost certain that one of these switches is stuck in the closed
position - even when its valve is closed. If you disconnect the valves'
grey and orange wires from the junction box, and check for continuity, I
think you'll find the problem - one or other switch is stuck shut.
--
Cheers,
Roger
____________
Please reply to Newsgroup. Whilst email address is valid, it is seldom
checked.
  #9  
Old November 22nd 11, 12:44 AM posted to uk.d-i-y
external usenet poster
 
Posts: 3,823
Default Central heating won't turn off

In message , Simon T
writes
OK, I know other people have had this problem and have done a cursory
Google search, but have not been able to shed much light on what might
be the problem in my particular case.

Basically, the central heating round at my parents house refuses to
switch off, even when the thermostats aren't calling for heat and the
timer is off. The pump continues to run and the boiler continues to
heat the water and the only way to get it to switch off is to turn
everything off at the mains.

I suspected it might have been a stuck 2-port valve, but having checked
both of these found that neither one (CH or DHW) were stuck and
appeared to be operating fine.

Their set up is a standard Gravity Fed System with the feed and
expansion tank in the loft.
Glow Worm hideaway boiler (in a small room next to the kitchen)
Danfoss Electronic Timer (in the kitchen)
Danfoss Room Thermostat (in the Hall)
2x Danfoss 2-port valves (for CH & DHW - in Airing cupboard next to hot
water cylinder)
Danfoss cylinder stat (in airing cupboard)
CH pump (unsure of make - in the airing cupboard)

Again, the 2-port valves were most definitely not jammed open, which
was my first guess. In fact when I went round there to check them, I
found my mother had switched the gas off on the boiler (it didn't occur
to her to switch off the power supply), the timer was off, both 2-port
valves were closed, but the pump was still running?

What do you mean by "thermostats"?

What resistance is the temperature sensor showing at the pcb connector?



--
geoff
  #10  
Old November 22nd 11, 09:01 AM posted to uk.d-i-y
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Posts: 18,242
Default Central heating won't turn off

Ben Blaukopf wrote:


However, even if the valve is faulty, if the timer is off then the
pump should still be off,


No.

thermostats and timers drive the valve, the valve has the high power
contacts that drive the boiler and pump.

Its perfectly possible for the contacts to weld shut so the switch is
closed, even when the valve has shut.

If the system is wired 'correctly; that is in fact the simplest explanation.

physical chafing and shorting of wires being another option.

 




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