drayton digistat scr not turning boiler off (yes off...opposite of everyone else!)

[Adzb1]

Hi all...help!!

So I have a wirless drayton digistat scr connected to a valiant boiler. The thermostat is working (new batteries) and is telling the receiver to turn on and off the boiler. Relay seems to be working inside the unit as I can hear a click and green light appears.

I can't overright the boiler to force on with the top over right button (does nothing).

When the thermostat gets to optimum temperature the green light goes off but the boiler stays on.

Problem is we moved in recently so we will never know if it used to work correctly.

What's your thought?

[John Rumm]

Disconnect the stat from the boiler temporarily, and use a multimeter to see if the actual instruction coming out of it matches the LED indicators. It might be fore example that the relay contacts have fused shut leaving a permanent demand for heat.

[Roger Mills]

We need to know a bit more about your system. Does the boiler heat the radiators *and* a cylinder for the domestic hot water? Are there any motorised valves in the system? If so, how many, and what type - i.e. 2 or 3 port?

If you could post[1] a few photos showing pipe arrangements in the vicinity of the boiler and in the airing cupboard (if you have one) together with any motorised (zone) valves, we'll be in a better position to help you.

[1] You'll need to upload then to somewhere like Flickr (unless you've got your own website) and post a link here.

[Brian Gaff]

Or perhaps it is via a thyristor and the break in the circuit required to snap the scr out of conduction is not happening due to any number of things in the circuit. Brian

[Harry Bloomfield]

on 30/04/2018, Brian Gaff supposed :

The OP mentioned it being a relay in his text, but called it an SCR in the subject line.

[Harry Bloomfield]

Harry Bloomfield submitted this idea :

Would it not have been a triac anyway, passing ac?

[Dave Plowman (News)]

My first one would be to find the installation manual for the boiler and check the thermostat is suitable and correctly wired in. As, for example, some boilers may use a temperature sensor rather than thermostat to measure room temperature. Or give you the choice.

Most plumbers are plumbers, not electricians.