should my three port valve be running hot

They do run warm. It would be a good idea to relocate the valve so that it's at 90 degrees, so that the pipe doesn't additionally heat it. I suspect putting the valves in the return, if they can.

In particular, they can remain powered and in the mid or CH position when nothing particular is happening. It requires a demand for HW-only to bring it back to the HW position. [This actually works to your advantage. Imagine a situation where the HW demand is satisfied and the CH is cycling on and off on the room thermostat. If the valve returned to the HW (unpowered) position every time the room stat switched off, there would be delay every time the stat switched back on, while the valve moved back to the CH position, before the boiler and pump would start].

Check what position the valve is in when the actuator is warm even though everything is off. If it's anywhere other than in the HW position, the manual lever will flop about freely.

If you want to force the valve back to the HW position, turn off the whole heating system at the FCU (not the programmer). You should then see/hear the spring return operate. If it does that, it's probably ok.

That may have been the problem. If the valve was too stiff to move, the actuator may not have been able to move it all the way to the CH-only position - in which case the HW would have been (over)heated at the same time.

Run it for a bit, now you've freed it, and see what happens.

Thanks for that, It sounds like everything is ok, I'll run the system as normal and try your other tests if I get scalding water again.

cheers dedics

It can still stay in the middle position when all power is removed. This is because the middle position is held by locking the rotor with DC current, and it ends up magetising the yolk, often enough to prevent the spring return. In order to guarantee spring return to the HW position, a tiny AC current is supplied via a resistor to degauss the yolk, which hence needs power.