Hi all.
My system is:
Vaillant ecoTEC 430 open vent boiler
Vaillant VRT360 programmable room thermostat
Vaillant VR65 control centre
Vaillant VR10 NTC sensor (tucked under insulation on a normal DHW tank)
It mostly all works super, but I have noticed that sometimes, when DHW is demanding heat, the flow temperature set via eBus is 80c and yet other times it is 65c (65c being the rad flow temp I have set on the boiler).
When it is 65c, this causes the boiler to cycle because at that flow temperature, the heat is not disspated into the hot water via the indirect coil as quickly/effectively as at 80c (i.e. the differential between flow temperature and the tank temperature is significantly less), and even when the boiler is modulated as low as it can go, the heat input is still greater than the heat being dissipated in the hot water. So, lots of very short cycles - the boiler starts up and shuts down almost immediately.
At 80c flow temperature, the system is amazingly good at heating the hot water, as it can modulate down and maintain that flow temperature without causing any boiler cycling, and will heat the tank in short order, I suspect this is quite efficient too.
If I reset the whole system, by power-cycling it, it usually causes it to revert to the 80c flow temp for a few days, before it then seems to go back to being pot luck whether I get 80c or 65c.
I am left wondering whether this is a fault somewhere in my eBus system, but I don't know how to narrow it down to whether it is the VR65 not requesting the correct flow temp, or whether that is done at the boiler? Or whether it is determined by the VRT360?
Any ideas/advice gratefully received (before I succumb to trying Vaillant technical support, who in my experience, aren't particularly technical, or supportive!).
Thanks in advance,
DH2
My system is:
Vaillant ecoTEC 430 open vent boiler
Vaillant VRT360 programmable room thermostat
Vaillant VR65 control centre
Vaillant VR10 NTC sensor (tucked under insulation on a normal DHW tank)
It mostly all works super, but I have noticed that sometimes, when DHW is demanding heat, the flow temperature set via eBus is 80c and yet other times it is 65c (65c being the rad flow temp I have set on the boiler).
When it is 65c, this causes the boiler to cycle because at that flow temperature, the heat is not disspated into the hot water via the indirect coil as quickly/effectively as at 80c (i.e. the differential between flow temperature and the tank temperature is significantly less), and even when the boiler is modulated as low as it can go, the heat input is still greater than the heat being dissipated in the hot water. So, lots of very short cycles - the boiler starts up and shuts down almost immediately.
At 80c flow temperature, the system is amazingly good at heating the hot water, as it can modulate down and maintain that flow temperature without causing any boiler cycling, and will heat the tank in short order, I suspect this is quite efficient too.
If I reset the whole system, by power-cycling it, it usually causes it to revert to the 80c flow temp for a few days, before it then seems to go back to being pot luck whether I get 80c or 65c.
I am left wondering whether this is a fault somewhere in my eBus system, but I don't know how to narrow it down to whether it is the VR65 not requesting the correct flow temp, or whether that is done at the boiler? Or whether it is determined by the VRT360?
Any ideas/advice gratefully received (before I succumb to trying Vaillant technical support, who in my experience, aren't particularly technical, or supportive!).
Thanks in advance,
DH2