Honeywell at9400c Switching to ONCE Setting

[JamesL01]

Really hoping someone can help...!

Our timer keeps periodically swerving to the ONCE setting..! We have it permanently on Auto and with no set pattern some mornings we wake up to find the Heating (never water) coming on and the timer has seemingly changed itself to Auto.

Trying to figure out if this is a setting I've missed or whether I need to change, it's only 5 months old so in warranty...!

Thanks in advance for any help on this.

James.

 

[dilalio]

Sounds like a faulty programmer!
Just change it for a new one.
You could demount it today and bench test it with a standard 3pin plug and 3amp fuse just to power it up and see if it repeats the fault, but it is not uncommon to get a 'lemon' straight out of the box, with ANY electrical component!

 

[JamesL01]

Okay, and thanks for the quick response..!

Sorry to be really dumb but typical office worker here, how exactly do you do the bench test...?

 

[dilalio]

Well, without encouraging you to do something that might end up causing you harm, if you're not confident/competent messing with electrics...

It would involve turning off power to your heating circuit and removing the programmer from its installed location. Powering up the programmer "on a bench/table/worktop" by way of a plug and flex (with the 3amp fuse from the heating circuit in the plug) connected to the common and neutral terminals of the programmer. In effect you are connecting it to power "out of situ" to see if you can repeat the faulty behaviour in isolation of the rest of your heating and HW system!

 

[JamesL01]

Understand and thanks for the words of caution, my in laws are all electricians so will pass the honour to them..

Thanks again for the help.