apollo myson - high low setting

[Notebook64]

Hi
how is the high low setting controlled on my boiler?

long story but got water on the pump that blew it. replaced and if set to high the central heating and hot water works all ok. If set to low on hot water - the pump runs all the time.
If I go to the clylinder strap stat and turn this down, then as I do I can get the pump to go off / turn it up and on it comes again.

If I turn the high low setting to high - it all regulates as it should.
Thanks

 

[twgas]

your cylinder stat is set higher than the low stat so the boiler never gets as hot as the cylinder wants so is always calling for more heat and keeping the pump on. Put the blr stat on high and you'll be fine, or leave the cylinder stat lower.

 

[Notebook64]

your cylinder stat is set higher than the low stat so the boiler never gets as hot as the cylinder wants so is always calling for more heat and keeping the pump on. Put the blr stat on high and you'll be fine, or leave the cylinder stat lower.

I follow you - the stat on the cylinder should be set at what temp ?

That might make sense as i woke up in the night with just the sound of the pump running, not the boiler firing up.

I think I had the same thing when the pilot light went out?

The high / low stat - are fixed I take it as there is only a switch, and these I take it are only operational with the central heating on.

How would this have changed? can I replace the low stat?

 

[mysteryman]

There are 2 fixed thermostats in the boiler - the selector switch selects one or the other. You are best to run it on high so as to get the fastest possible DHW reheat. Try the cyl thermostat at about 50C, and make sure it is well clear above the top of the coil. The old advice about fitting cyl 'stats one third of the way up a cylinder was OK in the bad old days of gravity primaries, but you will have a fully pumped layout with an Apollo.

They were the best little boilers about in the non-condensing era, the latest Myson versions being the best of all.

I once came a broken wire leading from the high 'stat on an Apollo - it was OK on low, but u/s on high. The 'stat was OK, just a wire broken inside the insulation.