vokeras mynute 14/48 SE boiler

[boilerwoes]

A few weeks ago water pressure inexplicably shot up from 2 to 4 when boiler was on. Usually the pressure does not go above 2 when on. Had to get engineer out. He drained it back down to 1 (usual cold setting) and could find no fault, he suggested it had been over-pressurised, which I know for sure it hadn't.

A week later, the boiler stopped coming on. They came out again, this time it was a pressure switch that was faulty, a thin narrow tube which he blew into, lo & behold the boiler came back on. He said this had nothing to do with the raised pressure the week before. He also said the switch would probably need replaced, but I said I would monitor it. A week later, the boiler is not coming on again.

What I need to know is, is there a possibility the pressure gauge is faulty & this is causing false water pressure readings, in turn causing the pressure switch safety mechanism to stop the boiler from igniting. Or is the pressure switch faulty?

 

[Gasguru]

Boiler pressure gauges are normally very reliable although the presure relief valve should open at 3 bar so the reading should not reach 4 bar.

The pressure increased due to the filling loop letting water through (loop should normally be disconnected)

or the expansion vessel connection pipe blocked

or you may have an unvented cylinder and the coil has perforated (even more unlikely).

The boiler does not have a sensor to detect the water presure but it does have a differential sensor that detects if the pump is running.

It appears the engineer found a problem with the air pressure switch - these are relatively inexpensive and easy to test. This device is not connected with the water side.

 

[boilerwoes]

Thanks so much for this, Gas guru. Assuming it's an airflow switch, is there a reason why an airflow switch would suddenly block & be okay for a week (after he cleared it by blowing) then block again? The boiler certainly has become more and more sluggish 'starting up' this last week, sometimes almost 30 secs. Also when it broke down again, I noticed the radiators seemed to go cold immediately rather than the usual slow cooling down you get with a normal switch off.

Appears I am confusing pressure differential switch and air flow switch? Just that looking at the boiler diagram, the little tube he blew through at the top looks to me like the pressure differential switch!

OR could I have a pump problem - the pump is failing & the pressure switch is responding by shutting down. . .

When the pressure shot up a few weeks ago, it went past three but the release valve did not kick in, which surprised me. It has kicked in before. I just feel the whole boiler is not right after last few weeks.

My filling loop is connected, but it is fairly new as the old one had grit so I can't see it being faulty & the engineer checked it wasn't 'passing'... I really am perplexed about why the pressure shot up.

The boiler is ten years old, it was already installed when I moved in, but it has been a real headache, one problem after another, would you recommend a replacement rather than constant repairs? I also have it serviced annually.

 

[nickso]

this should be an easy repair.

either:-

1) the water flow switch beneath and right of the pump has a burst/stretched diaphragm or there is dirt in the venturi.

2) the fan is choked (very common) or the fan venturi are partially blocked or the aps is intermittantly not making.

3) outside chance of the pcb being faulty....unlikely from your description

 

[boilerwoes]

Thanks, both. Was the pressure differential switch that was faulty and has now been replaced!