ideal classicff260 water comes on lots of noise boiler trips

[needmorstuff]

Hi,

My water programme starts at 16:00, this is immediately followed by lots of noise from the tank area, then gushes of dirty black water come out of an overflow pipe in my gutter and shoots out about 4 feet onto my garden. The boiler then trips out (little red switch on side of boiler pops out)

I reset the red switch and everything works peachy.

any ideas?

 

[Gasescape]

Pump or choked cold feed ....
Red switch is the o/heat stat ..

 

[TCCHeating]

Could also be a faulty boiler thermostat?