Vintage Eurotherm Controller Information


Thread Starter

Stewart Gable

I've been given the job of looking after some equipment which is controlled by an FX10 and an FX11 plc. I only have ROM copies of the software running on these plcs and no way to edit or monitor their code. I'd like to hear from anyone with experience on these plcs, and copies of manuals or programming software would be greatly appreciated.


Linnell, Tim

Contact me off list and I'll see what I can dig up - no promises as I expect any documentation we had was disposed of several office reorganisations ago, but there are a few crusty old characters in the darker recesses of the
office who may dimly remember all of this (at least as much as they remember anything at all at their age). E-mail is timli-at-controls-dot-eurotherm-dot-co-dot-uk with obvious spam removal


Tim Linnell (Eurotherm Controls)
Hi, I'm jumping on this thread in the hope that someone here has knowledge of Eurotherm products and can shed some light on my issue.

I have acquired a 20 year old Lenton melting furnace. The control box has a Eurotherm 106 Process Alarm and a Eurotherm 815S Temperature Controller, wired together so the 815S is powered by the ALARM circuit of the 106. When the three phase mains are powered up the 106 lights up a single red LED (Alarm LED) but nothing else; the door microswitch is closed during this test, in a normally closed ALARM wiring setup. However when I detach the 815S and door microswitch, the 106 powers up fully, showing multiple LEDs. I have independently tested the 106, 815S, microswitch, buzzer, fuse and the voltage across all the positives and negatives of the 106 and all are working as expected. I think that maybe the the ALARM circuit of the 106 has the wires in the wrong place, but the only manual I can find is a German photocopy.

106 Manual:

815S Manual:

Any help would be greatly appreciated!



The 106 is just a thermocouple process alarm unit with a thermocouple input. When it gets to setpoint it trips. And the relay changes state.

The 106 manual, section 3.4, (page 5 pdf) shows that terminals 5, 6 and 7 are a Form C relay output: 5 is COM, 6 is N.O. and 7 is N.C.

106 alarm output Form C.JPG

Important: the 106 manual says that N.C. terminal 7 (buzzer) is 'made' in the alarm state and that the N.O. terminal 6 (door switch) is open in the alarm state.

It appears that in the non-alarm state, the 106 powers the door switch through the N.O. terminal 6.

Does the other side of the door switch power the 815 controller? Is that why you say that the 106 powers the 815?
Thanks for your help!

The door switch circuit runs parallel to the 815. On the 106 there are two black wires coming out of terminal 2, one of which goes to the 815 neg and the other to the mains negative. On terminal 6 there are two red wires coming out, one to the 815 live and the other to the door switch. So this is where this Form C relay powers the 815.
It isn’t clear exactly what the problem is.

When the door is closed, does the 815 turn on/power up?

Why did you disconnect wiring and do the checks?
Hi David,

I disconnected the wiring to test everything independently because I wanted to rule out any malfunctioning component.

The 815 doesn't power up with the door switch either open or closed.

I think that the relay is not being powered at all. I've tried translating a bit of the German manual online and it says that "in alarm state the relay coil is de-energised", and that "after power failure or switching on" the 'alarm acknowledgement' button must be pressed (my button is labeled 'Reset'). I have been pressing that button to no effect. So it could be that the unit is stuck in the just-powered-up alarm state because the button is faulty. I don't think the alarm state is being caused by the setpoint or thermocouple: I've tried many different set points, and even tested the thermocouple with reversed polarity to no avail.

...I'm stabbing in the dark, but maybe the unit lights up fully when the relay circuit isn't wired in as some sort of analog error alert and I'm seeing that as desirable because it's doing something more than just blinking the alarm LED.

The 106 Manual points fig 7.1 and 7.2 show two setups serving two different functions. I am going to disconnect the 815 and door switch and test at different set points to see if I can trigger the alarm state and make the buzzer buzz.

...needless to say that I'm looking at replacing the 106 too.

Thanks for your help :)