Drayton Tempus 2 Problem

ray-bentos · Nov 19, 2014

Hello

Attended a property where a local boiler care company have attended a fault with the heating and have replaced the stat and then traced a fault on the programmer (Drayton Tempus 2).

However the engineer refused to change the programmer as in his words 'there is a wiring fault, voltage present on neutral when boiler is isolated'

He has 'bypassed' the timer so the heating is constantly on. Upon testing this I found that when the boiler is isolated there is no voltage on any of the wires at the programmer. When the boiler is turned on there is a backfeed of approx 20v from the live switch wire to the boiler. I assume this is just leakage from the PCB/components within the boiler and is unlikely to have caused the demise of the programmer.

Shorting the live feed to the programmer with this live switch wire fires the boiler up as expected so do you think the fault is simply a dodgy switch within the programmer itself?

ImpededLoop · Nov 19, 2014

There's a few unanswered questions in your post, but if linking out the programmer works, it looks like you've found the fault.

Have you checked the wiring to see if the heating engineers comments were unfounded?

ray-bentos · Nov 19, 2014

I inspected the wiring for correct connection to both the boiler and the stat. I think I explained badly in the first post, the voltage is on the switched output from the timer that feeds the stat. Isolating the boiler at the FCU eradicates this. Once power is isolated here there is nothing at any point in the setup.

My real question was could this random voltage have damaged the timer or be causing it not to switch but then when I actually engaged my brain this is designed to carry the full 240 so why would ~20 cause any issue?

The programmer is a 3 wire job with volt free switching. The live feed to the programmer is bridged across to the common terminal and there is an 'on' and 'off' terminal. In this case the live switched wire is fitted to the 'on' terminal. Fitting this to the 'off' terminal results in the heating being constantly powered up (whether the programmer is set to run or off) which leads me to believe that the programmer switch is stuck at off. Also linking the live switch wire to the live feed powers up the boiler so there cannot be any fault with the boiler itself.