Mira Combi 415 , no hot water

[barbstiddard]

Hi , Help please

Came into this fault late !! Mira 415 installed for over 10 years with no problems. Then only gave cold showers and not hot. Cartridge had been changed as advised ( black cartridge ). worked a few times and then stopped, i.e. just cold again. Cartridge supplier suggested needed a Grey Cartridge and so swapped. This was installed but stopped working after a short while. This is where I came in !! Water pressure Hot and Cold appears OK ( fed from a oil fired central heating boiler at mains pressure.) Discovered Grey cartidge installed with with some Black cartridge parts by previous installer. I Ordered and installed new black cartridge and parts . Worked fine a couple of times , but now again only gives cold water out !! If cartridge removed and water switched on , get hot & cold into cartridge inlets !!

Anyone any ideas ...fed up with cold showers and buying cartridges.

 

[picasso]

Check that the boiler continues to fire when the shower is running, I take it that the boiler is an oil fired combi ?

 

[barbstiddard]

Boiler is a mains pressurised stored system. I have removed the cartridge and felt hot water arriving at the shower input to the cartridge . The feed is off of the bath hotwater supply and running the bath tap the water is red hot , but shower cold. So boiler functioning correctly also have had bolier checked and engineer says there is no problem with it or water presure !!

 

[picasso]

unbalanced hot and cold supplies at a guess, do you know if the cold is straight off the mains (rather than being taken after any pressure reducing valve) and what the mains pressure is ?

 

[barbstiddard]

Hi

Do not know what the mains pressure is and believe shower is fed directly off the mains for the cold water side !!

The starting point was that the shower did work for around 10 years and nothing has been changed in that time. My understanding of how the cartridge works is that if the hot pressure is reduced then the diaphram moves towards the hot input restricting the cold input to mainatin the balance .

thanks for your input to date