Grant combi - no hot (or cold) water

[willgordon73]

hi, i have a grant combi 90 boiler with a fault. The central heating works ok but there is no flow from the hot water taps. There is no water flow at all at any hot tap. If i push a matchstick into the microswitch on the front of the diverter valve then the boiler fires up. The pin on the diverter doesnt seem to move out though when i turn on a tap?
I took out the diverter valve, blending valve and plate heat exchanger and cleaned all 3 with vinegar, (there was limescale evidence) but it hasnt made any difference. I also took the diverter apart but couldnt see any holes in the diaphragm.
Please can anyone tell me whats wrong?
Thanks, will

 

[simond]

I'm not that familiar with Grant Combis, (fit Worcesters) but if there's no water there's a blockage.

There'll be a cold in and a hot out (mains water). Would start at the blending valve looking for water and work back. Diverter valve isn't going to detect water flow if you haven't got any, so that was a waste of time.

 

[willgordon73]

Thanks simon, i'll look at the blending valve tomorrow. Is it cleanable or am i better to replace? Is the hot water 'driven' by the pump or is it the mains cold pressure that pushes the hot water?
Thanks

 

[simond]

Mains cold drives it

 

[willgordon73]

Must be a blockage then. The cold supply comes straight from a jet pump with 25lit storage at 3-5 bar. I'll break open a connection at the blend valve and work back till i find water.
Thanks

 

[Boilerman2]

While you had it stripped down I assume that you checked for a Cold water supply to the boiler?? there is an appliance isolating valve which is tucked under the plate heat exchanger, near the filling loop is this valve on? I have had a blockage occur in the pipe work taking hot water from the plate into the blending valve, is this pipe clear?

 

[willgordon73]

Simon and Boilerman, thank you for your help. I have found a small inline filter/mesh just before the cold inlet isolating valve. It was packed off with crud and hence no flow. Its all working again now . There are lumps of scale coming out of the taps ocasionally, i'm thinking this might be from the inside of the heat exchanger?
Anyway, very happy to get it working again. Thank you both very much
Will

 

[Boilerman2]

Do your self a big favour and get a Water softener!