No heating and hot water together

[steved101]

I have a weird problem...

Hot water is ok on its own

Heating is ok on its own

BUT... when both are on at the same time.... I only get Hot Wwater and no Heating!

My system uses a 3 port valve mid position. COULD it possiby be a faulty microswitch preventing the valve from stopping in mid position? It is annoying.....

Anyone have any ideas what else it may be?

 

[jackthom]

Can you check the voltage on the valve's grey wire which should NOT be live when both Heating and DHW are switched ON.

If it is close to zero voltage and the valve is still motoring right across to the Heating only position, it does sound like a microswitch in the valve has stuck, with the 240V from the white wire going permanently to the motor.

 

[steved101]

the grey wire is not live (so i presume the programmer is not faulty then)!

but .... with both on together, the motor must not move across as i only get hw!! the pipe to the rad circuit from the 3 port mid is not hot (it is hot, as it will be heated by conduction), but i mean not hot as if h/w is going through it, like the pipe to the hot water cylinder is.

 

[seco services]

are you still getting voltage on the white when both hw/heating on ?

 

[steved101]

yes the white wire has 243 (v) . ive checked that earlier.

thats why i don't know what's happened - it is not normal!! unless as i thought before, the microswitch was not allowing it to stall in mid and just keeps it in the hot water only (rest)position. although saying that, how comes i can get heating on on its own?! very weird...

 

[seco services]

when both are on is their power to the motor in the actuator ?
we know its getting power from the white to the actuator but if the motor don't receive power it will stay in hw mode only heating closed.

 

[steved101]

how will i test for this seco?

 

[seco services]

theirs two wires going to the motor in the top of the actuator
test each of them when heating/hw calling it should have a live to operate the motor across to mid position.

 

[steved101]

ok will do.

sounds like a dodgy actuator then. will probably have to buy a new one tomorrow now

 

[steved101]

there are many wires going to the valve , (after unscrewing the casing)... one is scrwed (pre-screwed) to the metal casing part, and lots to another part at the front, which has like a padded cushion thing covering them! what ones exactly do i need to test? some seem to have like clear plastic caps on???

 

[seco services]

can you see the two to the motor.

 

[steved101]

i'll have to get the torch out to check properley - it's in the airing cupboard. i will try and find them!! if no voltage to them, is a dodgy wire the fault? what if they are fine? is it a dodgy valve?

 

[seco services]

if no power could be the board etc.
if theirs power the motor should be moving to mid position.

 

[steved101]

the board?

how weird is it though that the motor must move, as htg on on its own is fine.

 

[samparker]

actuator must be knackered. replace it if possible, if not, replace the whole 3port.

sometimes, the microswitch #2 goes, which means you cannot get heating on its own, sometimes the motor fails and you only get h/w (thus need to move the lever across to get heating too, but only until the cylinder thermostat is satisfied).