Baxi 105HE cutting out every 12-24hrs

[anthonyl123]

About once or twice a day the boiler cuts out with the 60deg light flashing. I can also force this by turning the boiler to Off and then immediately back on again. If I wait 30 mins in either case the boiler will fire up and operate as normal including hot water and showers.

When I force a cut-out so the light is flashing then I can hear that the pump is running for about 3 mins then it will stop, but I still have to wait for 1/2 hr before it will kick in again by turning to Off then On (left hand knob).

House is bungalow, boiler at the back, pipes run above through attic, all rads at ground level.

Recent history:

July - boiler serviced all reported ok.

Aug - no hot water but radiators would warm up instead. Diverter valve replaced. Engineer had a minor panic as he got water on the circuit board which he immediately dried.
Next day pressure was dropping and drips in overflow pipe. Tried clearing by blowing out (quick releases of valve and repressurising). Problem cleared for a few days then continued. I kept topping up and tried to keep the pressure up until:

Mid Oct - PRV was replaced.

As there had been a lot of fresh water introduced I added 1 litre of inhibitor and bled the system. All running ok.

Nov - boiler started cutting out.
Bled the system again, and again. One radiator seemed prone but eventually was satisfied I'd got all air out.

Engineer visited today and showed him the forced boiler cut out - he's still at a loss and said he could replace this or that (eg pump) but no guarantee that it would fix the problem.

I need a better answer or a better way to diagnose the issue please, including items (if any) that can be ruled out.

Note the pressure gauge is fine, running at about 1.0bar when completely cold and up to about 2.5bar when all up to temperature, currently 50C

 

[ianmcd]

Not saying it will cure your problem , but the pressure guage should not be rising from 1.0 bar to 2.5 Bar, your expansion vessel needs checking

 

[gas112]

There is two pins on divertor the top one will be sticking in the up position it needs stripping cleaning and greasing

 

[anthonyl123]

Not saying it will cure your problem , but the pressure guage should not be rising from 1.0 bar to 2.5 Bar, your expansion vessel needs checking

Oh - it's on 2.4 Bar at the moment which the manual says is within spec but the manual doesn't say what pressure change is acceptable from cold to hot. What would you expect for a proper functioning expansion vessel?

 

[anthonyl123]

There is two pins on divertor the top one will be sticking in the up position it needs stripping cleaning and greasing

This is a brand new diverter valve fitted this August. It seems to be working in as much as hot water comes out when expected and radiators work when expected. Why would a pin be sticking and why would that cause the boiler to cut out every 12 - 24hrs?

 

[gas112]

tell you what try looking at it when it does it, when pump goes off pin should retract straight away everytime , bet it isnt ,

 

[anthonyl123]

@gas112 - there are two pins. The one on top, when everything off, is extended but just short of the microswitch. When the boiler is turned on it extends more and activates the microswitch. When the boiler is turned off it returns to its rest position after a couple of minutes when the pump stops. At a guess the pin would retract further if the system had no pressure but I've not tested this.

The end pin is fully in at rest, as soon as a hot water tap is opened the pin comes out and activates the microswitch. As soon as the hot water is turned off the pin fully retracts.

It really would help me if I understood your thinking on this. CH comes on when it should, HW comes on when it should. The pins are clear of the microswitches when the boiler is in its fault condition.

 

[gas112]

what bit of retract straight away is hard to understand

 

[anthonyl123]

I understand your words - I don't understand your reasoning. Why does the pin need to retract at all whilst the CH pump is on? I'm not arguing but things that I'm asked to do have to make sense to me otherwise I'm not understanding what's going on and you're not here to see what's going on.

Respectfully therefore I ask for less sarcasm and a bit more support.

 

[gas112]

i never said when the pump is on .i said needs to retract straight away when pump goes off.

 

[anthonyl123]

i never said when the pump is on .i said needs to retract straight away when pump goes off.

And indeed it does - as soon as the pump stops the top pin retracts sufficiently to release the microswitch as I explained earlier.

 

[Wigum]

It should retract all the way back.
I would take a guess that the water venturi beneath the diaphragm in partrially blocked.
If it was fully blocked you would get no movement

 

[DP]

And indeed it does - as soon as the pump stops the top pin retracts sufficiently to release the microswitch as I explained earlier.

What gas112 says is solid advice. Stop arguing with him address the problem he highlights
Unless you have a massive house with zillion radiators, pressure should not rise by 1.5 bar with temperature rise of 65 degrees. Every engineer does a bit of head scratching when stuck, but some of what you say should be elementary stuff for a service bod

 

[dilalio]

Try applying a little pressure on the pin to ‘park’ it back fully home. If the boiler then restarts without a 30 minute wait - you have your answer (or part thereof).
Also read up and check air pressure on ev.

 

[anthonyl123]

State of Play:

The top pin has been taken out and is clean and free moving. The diaphragm and spring moves freely when pressed by finger. The hole below the diaphragm lets water out freely.

The top pin stays stuck in the up position when operating even though it is clear of the microswitch. Pushing it down doesn't always allow the boiler to fire up immediately, a wait of about 30 mins consistently allows the boiler to re-start regardless of pin half way up or pushed all the way down.

Setting the timer with 30min breaks every 8hrs doesn't cure the problem.

I don't think I can go any further with this in terms of taking things apart as it is beyond my capabilities.

Questions:

1) If the diaphragm/spring/pin is freely moving and the hole below is not blocked then something else must be holding the pressure when the pump is off? What? Faulty internals to the diverter?

2) If the system set to 24/7 operation works for 8hrs then why doesn't it work for 10hrs? Does a Baxi 105HE pump have a "stop every 10hrs or so" logic?

3) Can air locks in the system cause an issue like this?

A note on the pressure - I had previously left the top-up hose connected. When I disconnected it and put the end in a bucket it had a gentle drip so I'd obviously not turned it completely off. Pressure now is 0.9bar cold and 2.0bar when on 60c.