Sime Format 100c Hot water problem..HELP!!

[np27np27]

Hi all,

I have the above combi-boiler and it is recently goving me a bit of trouble! When only the DHW is turned on, the water comes from the tap hot. Then after a short time the boiler burner cuts out and the water turns cold!
The interesting thing is that it seems to work fine if the central heating is on at the same time. Water comes out hot continuously.
I dont know much about combi's, but could the problem be with a flow switch? If so, is it easy to change or do i need to call an engineer?

All help would be greatly appreciated.

Thanks.

 

[ChrisR]

Probably. Do a search on "diaphragm"

 

[np27np27]

Probably. Do a search on "diaphragm"

Thanks. There seems to be alot aorund regarding that part. From what i read, this seems to be some part within the divertor valve? Is it the same thing as a pressure switch or is it different?

Sorry about all the questions, but i would like to learn about the workings of a boiler!

I also forgot to mention, the presure reading seems to drop to 0 when neither the DHW or CH are on. Pressure returns to normal when the DHW or CH are on. Is this normal on this model? or could this also be part of the problem?


Thanks.

 

[ChrisR]

They vary, suggest you try the manual...
Pressure on diaphragm when water flows, operates the diverter valve.
A split diaphragm loses the pressure.

presure reading seems to drop to 0 when neither the DHW or CH are on.
Pressure returns to normal when the DHW or CH are on.

See Boiler Pressure Problems in the FAQ

 

[np27np27]

So is a diaphragm replacement an easy job on the Sime format C boiler? Can i do it myself or should i call in the professionals? Also would Plumb centre have the part?