Cylinder Stat wiring - 542902

[marev]

I'm replacing a faulty cylinder stat (no click when adjusting temp) and when checking the wiring on it the common link wire and red cable appear to be connected the wrong way round.

As you can see from the pic of the adjuster side, the brown wire (being used as a link) has been connected to #1 terminal and the red has been connected to #C. Just to add, the brown link is connected to C on the limiter side.

Just wanted to check first before I remove the stat and connect a new one that has the same terminal layout.

 

[ianmcd]

your thermostat has two fuctions, the right hand one is a thermostat and the left hand one is an overheat lockout, try pressing in the small button on the left hand stat , if it clicks your thermostat will now work

 

[marev]

Tried that already. No click on the reset button.

 

[marev]

I have traced the stat wiring back to the main junction box as follows:

Red to Brown (HW on)
Yellow to Grey (3 port) & Black (HW off)
Blue to Brown (2 port)
Earth to Earth

I have attached a pic of a stat wiring diagram I found online, which seems to make sense.

So using that diagram, the stat connections would therefore appear to be:

Red to C (limiter)
A link wire from 2 (limiter) to C (adjuster)
Yellow to 2 (adjuster)
Blue to 1 (adjuster)

Does that look right?

 

[marev]

Just to add. The 2 port valve is between the 3 port valve and cylinder. Presumably acts as the safety shutoff if the limiter kicks in.

 

[ianmcd]

Just to add. The 2 port valve is between the 3 port valve and cylinder. Presumably acts as the safety shutoff if the limiter kicks in.

yes that is why it is there that is correct, do not go by any wire colours in a heating system, the only colours that mean anything are the factory fitted flex on motorised valves , they are all industry standards, every other wire colour is just a lottery, just depends on who wired it,you have an unvented HW cylinder and this thermostat is a safety device so you shouldnt be touching it as you are not G3 qualified

 

[marev]

you shouldnt be touching it as you are not G3 qualified

I am aware of that. I was just curious as to why it has been connected in this way.

Having traced the stat cable back to the junction panel the SL (red) is connected to the common on the adjuster.

Every wiring diagram i have seen says it should be connected to the common on the limiter. Also, the link wire, which is normally factory pre-wired on dual thermostats from C on adjuster to 2 on limiter, is incorrectly connected from 1 on adjuster to C on limiter.

I'm certainly no expert, but the way this stat has been connected I cant see how the limiter will get any power if it is ever needed.