Myson Apollo 40S - Gas cut off

[Kav69]

I'm having this problem for a while. Basically, when the temperature gets close to the set temperature, gas cuts off and boiler shuts off and after 1-3 seconds it fires off again and works for a short while and then the same story again. There are three thermostat on the water pipe (limitstat (green), highstat (brown), lowstat(white)).
Any idea what the problem might be?
Cheers

 

[Agile]

We cannot do anything other than guess unless you can measure the flow and return temperature at the boiler.

There are several possibilities.

If you dont want to bother with any measurements then you could change all three thermostats and that may well cure the problem as they can drift a long way after 15 years! Needs thermal transfer paste!

However, there could be several other possibilities, too low flow rate or wrong gas settings or scalled up heat exchanger etc.

Tony

 

[Kav69]

thanks for the swift response.
Unfortunately I don't have the equipment to do the measurements. However I will change the stats next week to see if it does the trick (I think they've been in service long enough!).
One thing that I noticed was that when I set the pump to low (it's got 3 levels) this occurs much less or sometimes it does not happened at all!! But as soon as the hot water starts running, gas cuts off and boiler fires up again etc...

 

[mickyg]

poor circulation, but the case back on. problem eslewhere.

pump, c'feed, header tank...

 

[Kav69]

poor circulation, but the case back on. problem eslewhere.

pump, c'feed, header tank...

Actually the pump sometimes makes some ratteling noise when works on high speed. Is there any ways to check if this is really faulty and if so is there any ways to fix it?

 

[kevplumb]

replace it