Vaillant EcoTEC Pro Always Heating Heating

[trevor middlemas]

Hi,
I have a 2yr old EcoTEC Pro 28, just out of warranty. Two weeks ago it started making an intermittent buzzing noise from inside the boiler, quite loud can be heard upstairs and recorded it on a phone, sounded like a motor or valve struggling to open/run. On the first occasion I turned the boiler OFF/ON and the problem cleared, second time I ran the hot tap and that cleared it.

Forward two weeks......heating turned on this Sunday, room heated to preset 19C, but the heating continued to rise very slowly to 20.5 an stayed at that continually until the boiler was turned OFF/ON again. I have a NEST stat and heatlink, I'm sure the call for heating is not coming from them, I have done full resets on both and disconnected them. How can the boiler be heating and maintaining 20.5C. If I turn down the boiler radiator preset temp by ~5C the temperatrure the boiler maintains the room at drops as well, but still keeps heating despite the stat being set much lower and the heatlink not calling for heat....Seems its got a mind of its own. Anyone any ideas please?

Trev

 

[picasso]

Sounds like your diverter valve is sticking, turn the hot water comfort off and see if the boiler stops heating when there is no demand.

 

[trevor middlemas]

Thanks Picasso,
I'm thinking on the same lines as you, so when I left this morning at 7:30 comfort was off and heat set to 15C. I'm looking at the Nest app now on my phone and heat is still set to 15C and says not heating, but house temp is 19C..no its not sunny, its Manchester! so the boiler has been up to something of its own accord in the past 5 hours. I guarantee it will stay at 19C until 4pm when the heating officially comes on and takes it to 20C.
Maybe I should ground it and confiscate its Heatlink for a week?

Trev

 

[Agile]

I always recommend a background heat setting of much less on a Nest, usually about 12 C.

Be aware that if the Nest is very far from a heat source the temperature in the house can overshoot the set value.

Tony