glowworm space saver 40b mk 11 problem

[Hobo128]

Called to job, customer reports that the f and e tank has started to overflow. Went into the loft and f and e tank was full of scolding hot water. Ran the bolier and every couple of minutes the open vent pipe would spit out boiling water.
I have this down to sludge in system and possibly pump set to fast. Also maybe the thermostat on the boiler is on its way out.
I want to know if anyone has had this before and also is there anyway to test the thermostat on the boiler (it's the type with the copper probe inserted into the cast heat exchanger)

 

[Leo21]

The only way I know of testing the stat is to turn it down low, and see if it cuts off and then on later. More than likely it's the cold feed and vent piped wrong, promoting build up of sludge or calcification. Take the pump out, bung it and remove pump valves and inspect the bore and condition of pipes.

 

[Hobo128]

Yes I have turned it low and it cuts out, you say it could be feed and vent piped up wrong, could you explain please

 

[Leo21]

It needs to be in the right order. Vent then cold feed (max 150mm apart) then pump. But that's closing the gate after the horse has bolted. It'll need flushing or pipe replacement in areas, usually by the pump.

 

[diamondgas]

If it's spewing out the vent then it's usually due to 'surging' once the pump is turned off! Quick fix is to raise the hight of the vent pipe. Otherwise consider combining the feed and vent or reconfiguring F&V pipes to overcome the 'pumping over'?

 

[Hobo128]

Okay, went back to the job, took a look under the floor, first of all it was a one pipe system, not one single clip on it, all pipes where layed on the sleeper walls sagging, at first glanse I told customer they needed new boiler which they accepted. I have it down to pump struggling to pump round rads down stairs. I have the pump with me so when I get time I'm going to check it over.