DHW Microswitch not engaging even with new diaphragm

[danielbb]

Boiler model potterton 30HE
http://www.potterton.co.uk/docs/Potterton_Performa_30_HE_Installation_and_Service_Instructions.pdf


Im having a few issues:

- DHW always hot when heating on.
- DHW not working unless tap fully open.

I read the manual and came up with the following.

I used an infrared thermometer and the plate heater exchanger is hot 70c even when the boiler in central heating only mode. This suggests the diverter valve is knackered?

Next the microswitch for DHW doesnt engage unless taps are fully open. I changed the diaphagm but the issue is still there, so am i right in saying its a hydraulic venturi issue?

Is this the part that is at the other end of the sensing tubes?

Many thanks all

[/b]

 

[gas112]

yes thats the venturi and providing you have fitted the diaphragm correctly then this does stop the proper pressures on either side of diaphragm being achieved.
When you take it apart you will find the plastic bit at end has fell apart and spring and bits are still left in housing , fish them out sometimes they have disappeared into the plate.
You need a 24mm ring spanner to get venturi out and when you order it you only need the end plastic bit with the spring , costs about a tenner

 

[danielbb]

Cheers matey, youre a star

 

[danielbb]

Lovely hot water again