back boiler problems

[norfolkinesox]

hi
i have a back boiler and for a while now ,when the hot water is selected the radiators get hot also when heating not selected,i know its the three way valve,but now when i only select heating(without hot water) the boiler doesnt kick in ,but control panel is lit,ive tried adjusting the room thermostat and on hearing the clicking it still doesnt kick in.
could this be something to do with the three way valve as in a knock on effect or something totally different ,any suggestions much appreciated

 

[Gasguru]

To start with check the 3 port spindle is not siezed.

 

[norfolkinesox]

the three port spindle as in on the 3 way valve? will this prevent the boiler kicking in then when selecting heating only?if not then were should i be looking-thanks

by the way we did have problems with radiators blocking with debris after having a radiator moved by a big kitchen fitter company(nightmare) can debris get to/ and become lodged in the three way valve causing the initial fault of radiators hot when hot water only selected

 

[gas4you]

Sounds like the microswitch has gone in the valve head.

 

[Gasguru]

Yes, if its a standard spring return type valve (as opposed to MOMO types)

If the valve is at rest in DHW mode (ie spring return) selecting heating will power the motor. When the motor turns the spindle (and closes the DHW port) a microswitch closes (at the end of travel) firing up the boiler etc. If the spindle is siezed or the motor burnt out (or partially burnt out) this will not happen.

 

[norfolkinesox]

thanks very much guys im getting the picture now, so what kind of cost would i be looking at to sort this if i paid someone would you say

 

[gas4you]

If its just the head, around £100 + vat, if the body has stuck as well, or it is one that you can't replace the head only on expect around £180 ish.

 

[norfolkinesox]

thanks dave and everyone else for their input much appreciated

 

[norfolkinesox]

i replaced the motor on the top of the three way valve and the heating now works!,i run through some tests and i still have the original problem of radiators hot when only heating selected when i put the hot water on boiler kicks in and the lever on the side of actuator is in the w position but when i turn off water and put on heating its still in the w position

i wired the motor exactly the same (just the two wires) should i try them the other way round as the motor is hot to touch,when i remove the motor the actuator does return under the spring tension so the valves not siezed and it seams the energised motors holding it in the w position,any ideas guys-thanks

 

[Gasguru]

Many 3 ports are never wired up correctly when they installed (customers just don't realise it). With no power to the motor the valve sits in hot water mode (flow to port B). Reversing the motor wires won't make any difference. Is the valve spindle easy to turn? What make/model of valve is it?