Ok, Im hot hot hot... No, really.

[BrianK]

I hope someone here can help me with troubleshooting my heating system.
I usually run the room thermo on 21.5 and hot water around 55c - continous, but the other day it suddenly started to get hotter and hotter.

I first set room stat to 17c and hot water to 40c but it still got warmer.
I then switched the programme to off but it still got warmer.

I've switched the system of at the mains when it got to 29c!

The controller is a honeywell smartfit YPlan. My first thought from reading through the forums is that it was a problem with the actuator. I have tried to remove it from the A/B valve and it seems to switch fine back and forth either manually or automatically when you power on the system.

Boiler is a Mexico Super 480FF.

There are no fault codes on the room unit and I have gone into installer setup mode to check through all the parameters which are set to default values.

Could it be a problem with the base/room unit, or does it still sounds like actuator (ML7300A)? What should my next step be in diagnosing the problem.

Thanks for any help!

 

[chrishutt]

Sounds like what happens when the micro switch in the motorised valve (actuator) gets stuck. I'm not sure off the top of my head of the details but there must be loads of threads covering this. you could also check the Y plan wiring diagram from the Honeywell site.