Almost boiling water out of bathroom taps

[pcdj]

We recently had a new cylinder thermostat fitted as the old one was broken and seemed to be permanently on (or off, whichever it is!). Having adjusted it to about 40 degrees the water coming out of the taps was perfect, however we sometimes turn it up when running a bath before turning it back down again.

Nowadays it seems that although the thermostat is set to the 40 degree mark again, the water coming out of our taps is too hot to touch. The strange thing is when it is adjusted to somewhere around its lowest point well below 40 i can hear the motor on the pipe next to it opening/closing the valve - so it still seems to be working.

It's a Honeywell L641. Would anyone happen to know what's up with it? Or should i just try turning it down to something silly like 20 degrees (even though this isn't marked on the unit)?

 

[gas4you]

The motor may sound to be turning but the valve body might be stuck open.

40C is the optimum temperature for legionella bug to grow

 

[pcdj]

How can i check whether the valve body is stuck in that case?

The stat is graduated from 40 up to 80 so i didn't realise there was a problem leaving it at 40! Even so, the water coming out of the taps feels more like 80 as i'm sure something's not working quite right.

 

[gas4you]

Assuming you have a zone valve with a removable head, if Honeywell this will have a 'pip' on the top at the grub screw end, then remove head and see if you can turn the spindle.

If you can it must be a wiring/ cyl stat problem.

 

[tryitandsee]

Make sure the thermostat has good contact with the cylinder to register the heat increase/decrease.
i.e. shaped hole for thermostat to fit against bare metal and wire strap around cylinder holding thermostat in place.

 

[bengasman]

cylinder stat should be set around 65, and sit snug against the cylinder

 

[twgas]

check to make sure immersion heater has not been turned on