Vaillant EcoTec Plus 630 dT

[John Carroll]

The boiler flow/return dT can be set in the above by changing  a few parameters to set the dT to between 10C and 20C, see attachment.

However this does not seem to work for someone I know, it worked to a fashion on CH only but not in HW mode (this isn't a big deal though)

The dT was set to its max, 20C in all the examples, below.

The best result (briefly) was a dT of 17C with flow/return temps of 64C/47C, pump speed 58%, next best gave 64C/50C, dT 14C, pump speed 64%, and on HW (cylinder), 64C/60C, dT 4C, pump speed 80%.

Can someone throw any light on this or if they have a EcoTec Plus try these parametrs to see wht results they get, this boiler is just 1 year old.

D.170 is set to 3, which is temperature spread control or dT.

Vaillant EcoTec Plus 630 dT.docx

[JohnMo]

dT is a combination of how much heat can be taken away compared to how much is being generated by the boiler. If your radiators can only transfer 4kW (dT between them and the room for example) and you are generating 16kW something has to give and it's dT. Reducing flow may cause the boiler to short cycle, increased flow will reduce dT.

 

The lower the flow, more heat is extracted from the water flow for a given heat input.

 

On the cylinder with a small coil and high flow rate your dT is always going to be small.

 

Bottom line is what are you trying to achieve?

[John Carroll]

Its not my boiler I have a oil fired boiler.

 

It was running (CH only for first 2 tests) at a modulation level of 4, I think it goes to 5 max?, 16 rads, all fully open so even with flow/return of 64C/44C, dT 20C will still give a rad(s) output of 60% so no way is this boiler output down to minimum, a dT of 20C with a target temp of 64C gives a return of 44C and a nice bit of condensing. if the boiler can achieve this dT of 20C then far easier than spending hours balancing rads to achieve it?, I would say its a excellent feature if it works.

 

[JohnMo]

6 minutes ago, John Carroll said:

If the boiler can achieve this dT of 20C then far easier than spending hours balancing rads to achieve it

Doesn't mean you don't need to balance, that is still needed. Balancing is required to ensure each radiator works as it should, without that the water could just circulate through a single radiator, boiler gives you dT 20, but house is cold because you have bypassed most the radiators.

 

Still not sure what you are trying to do?