Stelflow Thermostat query

[Dannyk]

Recently had two "engineers" look at a hot water problem.

To the left of the temperature setting knob on cylinder stat there is an unscrewable cover, which exposes what looks like a reset. Neither of them knew what this was for! One managed to trip RCD on consumer unit while looking at motorised valve, but didn't realise why no power. Problem now corrected itself.

Anyone know what this "reset's" function is please.

 

[Gasmk1]

Overheat trip

 

[Dannyk]

Overheat trip

Thanks. So if this tripped would it mean the thermostat has failed and needs replacing?

 

[chris watkins]

It would mean it is time to call an engineer with their Part G / unvented ticket, clearly the two you have had so far didn't.
The water is likely to have got to up to 80-85degC and the cause would need to be investigated.
Don't play around with these things It is a legal requirement to have the ticket to work on them.

 

[Dannyk]

Thanks, it's very worrying that there are people working out there that aren't qualified. Next time I shall ask if they've got the ticket.
Having seen videos of rocketing cylinders I can assure you I wouldn't play around with the system.
The fault is intermittent so I'm waiting before calling out an engineer.
Whilst the boiler has been serviced annually, no maintenance has been done on cylinder. When I mentioned this to last engineer he did something to expansion vessel above cylinder which caused it to hiss. He said all was ok. Satisfactory or not?

 

[chris watkins]

What is the intermittent problem ?
Expansion vessel charge should be checked on every service water need to turn off & drop the system pressure to do this not just push the valve to see if gas comes out. Safety valves & controls all have to be checked for correct operation.

It is standard level 3 plumbing stuff (not rocket science) but you will be amazed just how few have the knowledge or the ticket to be able to.
Please always ask to see their card.

 

[Dannyk]

No hot water despite CH working. Both bods had ruled out the valve and the second one reckoned fault was in the single channel controller. I put it back on backing plate and HW came on so I've left it. I won't have the second engineer back regardless of competence. On his last visit which was scheduled at 13:30 he didn't turn up until 17:30! No phone calls no apologies.
Thanks for the advice. Presumably part G will be noted on back of Gas Safe card.

 

[chris watkins]

or is a separate photo Card or Certificate.

 

[Dannyk]

Just found that this info is on Gas Safe site. It's a pity this isn't publicised more.
I'll being using it before engaging anyone.

 

[Chalked]

Trip can happen if the electric immirsion heater is accidentally left switched on.
.