heating and hot water - now not independant

[Oz1979]

Hello good people - I have a Vaillant Ecotek plus system boiler, controlled by a Honeywell ST9400C. Up until recently everything was working fine with heating and hot water working independently. Then the heating stopped working and only works now when the hot water is switched on. With both on the heating takes a lot longer to warm up and just seems inefficient to be doing both. When i select heating on the Honeywell programmer i get nothing, the pump doesn't even switch on. Yet when i select hot water we have both come on. I am not sure what is going on. I thought it might be an issue with the three-way but then thought the heating shouldn't come on at all if that is the case? Any help much appreciated.

 

[45yearsagasman]

. I thought it might be an issue with the three-way but then thought the heating shouldn't come on

It's most likely to be the 3 port from your description. That's where I'd start looking. What's the make/model?

 

[jackthom]

Is there a Honeywell 4073A valve or similay in the system?

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• jackthom
• 19 Dec 2008
• 18

It is fairly common for a three way valve to be the cause of this.
The valve could be sticky and not motoring right across to the Heating Only position, or the microswitch in the valve actuator which powers up the boiler/pump for heating only could be on the way out.

 

[Oz1979]

Thank you folks - I've had the Plumber around who has confirmed the same with the issue being the three way valve. Don't think i'll be trying to replace this myself though! First time i have used this forum and think its fantastic - it's you generous people with all that knowledge and are willing to share that really makes this work. THANK YOU!