Myson Apollo Problem

[Bas]

I'm trying to diagnose a problem with my 12 yr old Myson Apollo boiler. Standard setup with rads and a tank. The problem is best described as a loud expansion like "ticking" noise about once a week when the thermostat is set to high. If I set it to low the boiler just cycles every 15 to 20 secs. I imagine its a thermostat problem but any pointers would be very appreciated. I should add that the system seems to be working just fine.

 

[ChrisR]

To diagnose I'd measure the temps the Hi and LO stats work at. Easy with the right kit. As for an explosive ticking.... Always could be a scale problem, or water supply from the header.

 

[Bas]

Thanks for the reply. I don't think its scale as I live in a very soft water area and the header tank is working ok

 

[ChrisR]

Sorry Not that sort of (lime)scale.

Call it sludge generally = oxides of iron from rusting radiators. Bakes hard on the inside of old boilers. Then they call it scale. The water boils UNDER the scale and makes a noise when it bursts out.

 

[Bas]

Appreciate the explanation. Thanks. Would you expect that problem to be intermittent? Is it worth changing the stats to diagnose before calling in the pro's?

 

[ChrisR]

NO, predictably when it gets hot, or sometimes only when the boiler first fires up from cold.

On second thoughts the rapid cycling on Low coupled with overheating on High could point to a circulation problem. Any strange pump noises? Sometimes old ones do strange things like go slow form time to time. Check its speed setting - making it slower would be expected to make the problem worse if it's that department.

I assume this is a new problem and nothing has been altered for a while? Did the problem start suddenly or gradually ?

 

[Bas]

NO, predictably when it gets hot, or sometimes only when the boiler first fires up from cold.

On second thoughts the rapid cycling on Low coupled with overheating on High could point to a circulation problem. Any strange pump noises? Sometimes old ones do strange things like go slow form time to time. Check its speed setting - making it slower would be expected to make the problem worse if it's that department.

I assume this is a new problem and nothing has been altered for a while? Did the problem start suddenly or gradually ?

I've only ever noticed it in the morning first thing, the pump does make a "swishing" noise when it comes on in the morning - I always thought it sounded like it was pushing a little bit of air around. It is a new problem which seemed to start suddenly and nothing has been changed for quite some time. Thanks for the help by the way

 

[Bas]

I've now changed the pump and the problem appears to have dissapeared, looks like Chris R was right it was a circulation problem. The pump was working but the inlets were almost closed with oxides. Very satisfying, can't wait until morning when hopefully I will have no alarm call from the boiler!