Hi, can anyone help me identify why my CH is constantly on? Following
the recent cold snap I set my Honeywell controller to switch the
heating on the following morning. All was well in the morning, however
when the hot water only was due to come on in the evening, the heating
came on aswell, even though the heating controller was set to off and
the thermostat was turned to its lowest setting (off!) I'm beginning to
boil, walking around in my underware and the kids are sharpening the
harpoon!!

In an earlier contribution to this discussion,
wrote:

Hi, can anyone help me identify why my CH is constantly on? Following
the recent cold snap I set my Honeywell controller to switch the
heating on the following morning. All was well in the morning, however
when the hot water only was due to come on in the evening, the heating
came on aswell, even though the heating controller was set to off and
the thermostat was turned to its lowest setting (off!) I'm beginning
to boil, walking around in my underware and the kids are sharpening
the harpoon!!

Have you got a Y-Plan system [See
http://content.honeywell.com/uk/homes/systems.htm ] with a 3-port
mid-position valve to control the water flow to the CH, HW or both?

If so, sounds like the valve is sticking. The motor will have moved it to
the mid or CH position when you had the heating on. A spring is supposed to
move it back to the HW-only position when the CH demand is removed. If the
valve is stiff - particularly after not being used during the summer - the
return spring may not be strong enough to overcome the stiction.

If you think this may be the problem, remove the actuator from the valve
(couple of screws). If the actuator then rotates when it's no longer
attached to the valve, that is fairly conclusive. Try to move the valve by
hand. The shaft should rotate through 45 degrees either side of the mid
position - either using just finger and thumb, or with *light* pressure from
a pair of pliers. If it needs a lot of force, it is too stiff. You may be
able to free it by turning it to and fro. Otherwise, it will have to be
replaced.
--
Cheers,
Set Square
______
Please reply to newsgroup. Reply address is invalid.

formulated on Wednesday :
All was well in the morning, however
when the hot water only was due to come on in the evening, the heating
came on aswell, even though the heating controller was set to off and
the thermostat was turned to its lowest setting (off!)

It sounds like your 3 port valve has stuck. Turn the system of and undo
the two screws which hold the actuator (the motorised bit), onto the
valve. Check the water valve is free to turn with just a little more
than finger pressure. Make sure the actuator returns to it default
position when not powered up.

--

Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.org

We had a similar thing, have the heating switched off and hot water on,
then when the timer kicks in all the rads got hot, and the room stat had
no effect. Not knowing if it was the roomstat, the controller or the
three position valve I purchased a complete kit from Screwfix for less
than £60 (enter quote number 94777 in the box on the screwfix website)

Now the system is working fine and hopefully our gas bills will be a lot
lower this winter

Malcolm


wrote:
Hi, can anyone help me identify why my CH is constantly on? Following
the recent cold snap I set my Honeywell controller to switch the
heating on the following morning. All was well in the morning, however
when the hot water only was due to come on in the evening, the heating
came on aswell, even though the heating controller was set to off and
the thermostat was turned to its lowest setting (off!) I'm beginning to
boil, walking around in my underware and the kids are sharpening the
harpoon!!

Thanx for the help Set Square, as you can see by the time I have been
hard at it, sadly the Valve was so corroded i had to drain the whole
system down and replace it! you were spot on with the diagnosis