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PID in my Classic 2015 - strange quirk

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I have a 2015 classic that I fitted a PID to today. Just used a Rex c100 and SSR with a bare k type thermostat.

The thermostat is clamped to the boiler underneath the old (disconnected) one. Connectors from the defunct thermostat reconnected to the AC of the SSR.

Thermostat goes to my REX c100

SSR to the Rex C100 SSR connection

AC power for the c100 I took direct from the power socket


Any obvious issues with the above? 


So here's the bit I don't quite understand.... I set the PID to 103, it will get to about 101 and the ready light will then stop going on/off (as you expect with a PID) and then stay on constantly. Then the temp won't go any higher.

However - if I have the steam button in it will operate as expected. Get to 103, and hold it. I would have thought that the steam button would be bypassing the PID control and rerouting via whatever silly temp the stock steam thermostat keeps? This definitely isn't the case.

The other question I have is that given this behaviour I'm raising the PID to 130 with the steam button in to use the wand. Is this OK? I've seen people using the alarm and a second relay instead but not sure why?


Any advice greatly appreciated!


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