Central heating not working, hot water is

[bobonacus]

Hi,

I have a single gas boiler that runs my hot water and central heating.

Today the central heating stopped responding.

About 2 years ago I replaced the changeover valve, water pump and fitted a new RW29 control unit (box only as it just replaced the failed unit)

Everything has been working fine until this morning when the heating just wont run. The RW29 control unit says the central heating should be on, if I advance the hot water that comes on fine.

I've reset the RW29 box which made no difference. The wall thermostat (T40) is pretty old. With the power off I've tested continuity between 1 and 3 when the gauge is turned and it goes on and off fine. With the power on there is 240v (well, 250 actually!) so I am at a loss on what to check next.

There is power to the thermostat, it seems to swith ok, the hot water is working and the control unit says it has switched on the central heating but nothing happens ..... I've tried with the hot water on and off.

Any sugestions (other than call an electrician) greafully received

 

[seco services]

check the motorised valve.
if the stats sending a signal thats the next step.

(other than call an electrician)

be better with a heating engineer.

 

[bobonacus]

I assume that's the changeover valve? Is there an easy way to it other than just replace it!

cheers

 

[seco services]

what make is it ?

in your wiring centre box where all the cables join.
use a multi meter on the white wire.
switch heating on only water off, wall stat up and you want mains reading on the meter

 

[MANDATE]

seco didn't suggest replacing the valve, he suggested checking it.
It maybe needs a new motor, on the other hand it might have faulty microswitch. You have not said what make or model or type of valve.
You may be able to just replace the actuator head.

 

[bobonacus]

The pump and valve were bought from Wickes so not sure the make.

I've posted a couple of pics if that helps in the slightest

I've checked the white wire with a multi meter and its switching to 240v as I switch the central heating on and off.

Untitled

• bobonacus
• 19 Oct 2009
• 1

Untitled

• bobonacus
• 19 Oct 2009
• 1

Untitled

• bobonacus
• 19 Oct 2009
• 1

 

[bobonacus]

seco didn't suggest replacing the valve, he suggested checking it.
It maybe needs a new motor, on the other hand it might have faulty microswitch. You have not said what make or model or type of valve.
You may be able to just replace the actuator head.

Yeah, just my limited experience involves replacing rather than testing

 

[bobonacus]

btw, is using choc blocks normal, this is the first time I've taken the cover off the box so was a little surprised how "mickey mouse" it looked! The heating system was all in place when I bought the house several years ago

 

[seco services]

choc blocs normal don't worry.
when you have mains at the white check the orange aswell.
thats probably dead.

 

[bobonacus]

Nothing at the orange when heating is on or off.

 

[seco services]

wiring centre is abit of a mess inside and not in any order.

to the valve now
with heating on, calling at stat.
on the end is a lever with heating on the lever should be floppy no resistance to push it over.

is it loose or has resistance ?

 

[bobonacus]

the lever doesn't seem to do much, it's pretty stiff and seems to be set to manual/open. I can move it to auto but not sure it's doing anything, certainly doesn't make a difference with the heating on or off.

 

[seco services]

it won't do much as the grey wire probably holding it in last position.

if you can turn down the wall stat and isolate the power by the fused spur to your heating system then switch the power back on that will set the valve to it relaxed position hot water.
then watch the valve and turn up the wall stat you should see the valve move and hear the motor wind over if it don't i'd remove the motor and check that
if the motor winds over its a faulty micro switch
or the valves getting stiff and not quite activating the m/switch.

 

[bobonacus]

Switched it all off, stat on min and turned on again. Turned the stat up and nothing happened at the motor. Removed the motor, the physical valve turns, so is not stuck and the motor seems to wind ok so I guess faulty micro switch.

Are they replaceable/rebuildable or is it a new unit?

 

[MANDATE]

If the microswitch is the fault, I would say replace the whole unit. If just the motor, then just replace the motor.
Identifying and finding the correct microswitch is one thing, then you need the skills and tools to be able to fit them. It's time consuming.
Unfortunately Wickes don't appear to supply the valve head only, but worth asking. They may tell you the maker of the valve and if a head can be obtained.