DHW problems with Gas Sime Combi

[douger9999]

Hi there

A friend recently moved into a house with a Sime Gas Combi boiler, and is having a few problems, so I thought I'd post here and see what you guys recommend.

Firstly the CH side of the boiler works well, although the boiler is noisy to fire up.

The main problems are with the DHW side. Firstly in the bath, the water is only hot if the hot tap is on about 1/8 of it's capacity, which leads to a very long time to fill the bath. Secondly the shower does not give a suitably hot shower, the only way I have managed a hot shower is to run the shower, and also the cold tap in the wash basin.

The boiler has been serviced twice to try and fix this fault, but to no avail. I was wondering if you guys had any suggestions on what could be the possible problems with this boiler. I was thinking a clogged heat exchanger?! or a cracked diaphram??

Any help greatly appreciated...

Doug

 

[Rob]

With system cold try running a hot tap full. The flow pipe to the rads should not get hot. You may be losing power to the rads so the HW wont heat that well.

Im pretty sure this boiler uses the Gianonni diverter so you should be able to see the spindle react to when a hot tap is opened. If it doesnt lift enough when running a shower then suspect diaphragm.

To test HE you would need to measure the temp rise of DHW. Temp from hot tap minus the temp of cold inlet. Further tests would need a Corgi man.