Baxi 105e: CH/HW cutting out

[raidwi]

The central heating runs for c. 30 seconds, then cuts out for 20 seconds, then runs for another 30 seconds. Rinse and repeat. Same for hot water.

Solutions I have tried so far:

- Replaced diverter with new Baxi replacement as old one was in a bad way and radiators were warming when running a bath.

- Replaced plate heat exchanger and nearby wet pocket thermostat.

- Ran cleaner through the system. Have had a MagnaClean on the CH return for the last three years and it's not picking up much at all.

Any suggestions on what is causing this?

EDIT: video below (though might need to turn up your volume, it's a bit quiet). There's also a bit of a whistling noise that I haven't noticed before:

1.mp4

drive.google.com

 

[Wayners]

Pump working ok?
Not my area of knowledge but I have dabbled.
No warning lights?

 

[raidwi]

Pump working ok?
Not my area of knowledge but I have dabbled.
No warning lights?

Pump is running and sounds fine. Getting a warning light on fan for about two seconds after boiler shuts off, and then the light disappears as the boiler fires up again.

 

[gas112]

Pump is running and sounds fine. Getting a warning light on fan for about two seconds after boiler shuts off, and then the light disappears as the boiler fires up again.

if your on about it going to the neon below the fan symbol that is not a warning light unless it flashes

 

[raidwi]

if your own about it going to the neon below the fan symbol that is not a warning light unless it flashes

It flashes but only for a few seconds

 

[raidwi]

Something further.

After having replaced all of the above parts, there's now no hot water at all.

If the hot water tap is running, the heating also won't activate and pin at the top of the diverter isn't pushing the microswitch all the way. I can get in there and push it fully and then the heating comes on (but only for 30 seconds before cutting out as before).

If the hot water tap isn't running then the heating works fine for 30 seconds.

I have no idea what's causing this, it was allegedly a brand new diverter from eBay.

 

[Harry Bloomfield]

If the hot water tap is running, the heating also won't activate and pin at the top of the diverter isn't pushing the microswitch all the way. I can get in there and push it fully and then the heating comes on (but only for 30 seconds before cutting out as before).

Should you be messing about in there at all, are you gas qualified?

 

[richw]

Surely it's fine to work on the non-gas? (excluding any sealed areas)

It's possible your diverter is terrible. I had a Ravenheat RSF84 boiler which was similar-ish to a Baxi 105, and remember official diverters being expensive. I tried a £25 one, and it was a piece of junk. So I had to bite the bullet and get a proper one.

Can you monitor the flow temperature? Is the boiler cutting out because it's getting too hot? (close to 90 degC). If so, why is the heat not getting away? Blockage? Bad pump?

 

[gas112]

Think it is time you got someone in who can actually stand in front of the boiler and see exactly what its doing and not doing

 

[raidwi]

Surely it's fine to work on the non-gas? (excluding any sealed areas)

It's possible your diverter is terrible. I had a Ravenheat RSF84 boiler which was similar-ish to a Baxi 105, and remember official diverters being expensive. I tried a £25 one, and it was a piece of junk. So I had to bite the bullet and get a proper one.

Can you monitor the flow temperature? Is the boiler cutting out because it's getting too hot? (close to 90 degC). If so, why is the heat not getting away? Blockage? Bad pump?

It cuts out around 50C-60C (as hot as it can get in 30 seconds).

Diverter was from a place on eBay who are happy to take it back when I explained the issue, so have ordered one from a reputable place nearby to collect and will see if that helps.

 

[raidwi]

Think it is time you got someone in who can actually stand in front of the boiler and see exactly what its doing and not doing

Had a gas engineer round before and they said it was the plate heat exchanger. The eBay diverter's pin is definitely not reaching high enough so I'm happy to give a diverter from a local trustworthy supplier a try, but otherwise getting another professional in sounds sensible

 

[CountryFan]

Should you be messing about in there at all, are you gas qualified?

Ok on this model to remove front cover, it doesn’t have any seals.

 

[raidwi]

Is the new whistling sound something a dodgy diverter or plate heat exchanger would cause?

 

[gas112]

Is the new whistling sound something a dodgy diverter or plate heat exchanger would cause?

whistling is diverter, out of interest how much did you pay for it and how much is the next one

 

[raidwi]

whistling is diverter, out of interest how much did you pay for it and how much is the next one

Nearly £80, new one locally is over £100