Hello all. We have a Vaillant Ecotec plus 615 boiler. Our central heating system has an open tank in the attic and a hot water tank next to the boiler. There is a single three way motorised valve.
My main concern is that the boiler regularly fires up even when there is no call for heat.
As part of trying to diagnose the issue I switched off the boiler and disconnected the single 'call for heat' wire to the boiler. When I turn the boiler on the burner fires immediately. After a few minutes the burner goes off and the anti-cycle time is active. I think the burner fires up again as soon as that time is over.
The boiler could be firing for frost protection, if it were cold, but the ambient temperature is about 20°C. If there were a fault with the frost protection sensor perhaps that would cause this behaviour.
Are there any other reasons that a boiler might come on without a call for heat?
From the diagnostic menu:
D.016
Controller 24V DC:
Heating mode
1: On
Does this refer to an eBus control and is it normal for it to show this when there is no eBus controller? We've recently had a Nest installed, which I was hoping would fix the problem. It's now clear that the old thermostat and programmer were not the issue.
D.023
Heating mode status
1: Released
Does this indicate something like 'Anti-cycling time has completed' or 'Thermal cutout has reset'? In other words the burner will come on when there is a call for heat.
D.025
Ext. eBus signal:
Cyclinder charging
1: On
D.090
eBus controller
0:Not recognised
D.091
Status
DCF777
0:No reception
Wiring diagram
View media item 107594
Wiring (Call for heat on 12 was disconnected for testing)
View media item 107595
Wiring top connections.
View media item 107596
View media item 107593
View media item 107591
My main concern is that the boiler regularly fires up even when there is no call for heat.
As part of trying to diagnose the issue I switched off the boiler and disconnected the single 'call for heat' wire to the boiler. When I turn the boiler on the burner fires immediately. After a few minutes the burner goes off and the anti-cycle time is active. I think the burner fires up again as soon as that time is over.
The boiler could be firing for frost protection, if it were cold, but the ambient temperature is about 20°C. If there were a fault with the frost protection sensor perhaps that would cause this behaviour.
Are there any other reasons that a boiler might come on without a call for heat?
From the diagnostic menu:
D.016
Controller 24V DC:
Heating mode
1: On
Does this refer to an eBus control and is it normal for it to show this when there is no eBus controller? We've recently had a Nest installed, which I was hoping would fix the problem. It's now clear that the old thermostat and programmer were not the issue.
D.023
Heating mode status
1: Released
Does this indicate something like 'Anti-cycling time has completed' or 'Thermal cutout has reset'? In other words the burner will come on when there is a call for heat.
D.025
Ext. eBus signal:
Cyclinder charging
1: On
D.090
eBus controller
0:Not recognised
D.091
Status
DCF777
0:No reception
Wiring diagram
View media item 107594
Wiring (Call for heat on 12 was disconnected for testing)
View media item 107595
Wiring top connections.
View media item 107596
View media item 107593
View media item 107591
