Noisy Boiler when pump switches off

[waltfen]

I have a Myson Apollo boiler which is approx 14 years old. The problem is that 4 or 5 minutes after the water or heating has turned on the following occurs.
There is an audible click from inside the boiler, the pump then turns off but the boiler still runs. The water then boils as the pump is not pumping which causes lots of bangs etc. in the boiler area. After 5 - 10 seconds of this the boiler trips out and when it restarts (a few second later), everything is OK!
The system then appears to run OK until either the water or heating comes back on with the timer!
Any help would be appreciated as I think it can not be doing the pipework any favours!

 

[kevplumb]

pump overun stat is faulty

 

[croydoncorgi]

Hang on....
If the pump runs, then stops, but the burner continues when there's no call-for-heat, it ain't the overrun stat. More likely the gas valve sticking open!! If so, stop using the boiler NOW and get a CORGI to look at it.

Anyway, ISTR that the Apollo has no 'overrun stat' as such: just two fixed temp stats for High and Low temp, plus an overheat stat that interrupts the thermocouple connection and knocks out the pilot.

 

[kevplumb]

according to myson it has

43 384-208 Pump Overrun Thermostat - Thermodisc 60T13-500073 402S088

 

[waltfen]

I have the installation manual and it states that there is a pump overrun thermostat, it also has stats for Hi and Low.
The Numbers for the pump overrun thermostat are :- GC No 382 374 and Part No 402S087.
Do these sound right?
System has been like this for about a month and run OK after the initial banging etc.

 

[kevplumb]

easy way to check if its the stat take the wires off and join them
pump will / should run all the time and not cut off

 

[croydoncorgi]

My mistake: there IS a pump overrun stat. It looks like in its 'cold' state the live for the pump comes off the connection which operates the boiler. In the hot state, pump-live is straight from the permanent live connection on the boiler.
SO....
If the overrun stat stopped working and was stuck in the 'cold' position you'd get exactly the symptoms you describe.

43 384-208 Pump Overrun Thermostat - Thermodisc 60T13-500073 402S088 agrees with the numbers on PartsArena for an Apollo 15/30

 

[kevplumb]

 

[waltfen]

Big thanks to kevplumb and CroydonCorgi. I have finally received the overrun thermostat. Fitted it in 5 minutes and I have a quiet boiler!!

 

[Ziderman]

Read the details and my family have lived with this problem for over a year! (I know, I know.....)
We've all got used to the sound now and sleep through it but now we've got a dog he goes mental when the boiler sparks up in the morning waking us an hour before we need to get up.

I could switch it in later and use the dog as a very effective alarm clock but would rather get it sorted once and for all.

We had the boiler serviced back in the spring of this year and the CORGI engineer suggested it was the wrong pump fitted and it was leaking etc...

Seems the whole issue may be down to the Pump Overrun Thermostat.

Problem, when we moved into the house I had no documentation for the system so whilst I can tell its a Myson Apollo I don't know if its a 15/30, 30/50..... and don't know if the part quoted in previous posts will work. Equally I don't have the details on on where and how to fit it!

Any help would be appreciated.

 

[rudigallo]

take the covers off the boiler, its on the right hand side of the outer frame at the bottom.

about 10.00 takes 10 mins, changed mine after 15 years of problems perfect now

 

[londonboy]

He's probably scrapped it after 3 years

 

[Biguns]

This link will take you to a download site. It will then tell you to click download button. This will give you the Myson Apollo MIs.- Fig 9 on page 17- will show you the pump overrun stat.


http://www.mediafire.com/?zm1mqwnrnz3

my Apollo is now 22 years old. All my expense amounts to is a thermo couple and pump overrun stat

 

[Ziderman]

Sadly the boiler is still there and in fact due to the help received from this site I have managed to replace the Over-run stat, the pump and the three way vale to cure various ills.

Still left with kettling and air getting in somewhere but we are warm and can shower!