Vaillant ecoTec Plus 630 boiler not reaching target temp

[windsortg]

so I changed d.00 to 28kw. The speed of the boiler immediately increased and the modulation level went up to 4. I am now finding that the boiler flow temp is reaching the boiler target temp of 65C and the rads are heating up nicely.

Reading my IHD linked to my smart meter, I have found that I am using approx £15 per day of gas in the last few days of this cold weather spell so I may look to reduce the boiler set temp to see if that makes a difference.

 

[Johntheo5]

LLH don't lend themselves to very efficient boiler operation without adjusting the boiler (primary flow rate to match the secondary flowrate.

For example 25kw "worth" of rads with flow/return temps of 65/49.7C will give a output of 17.1kw at a flowrate of 16LPM (secondary side). If the boiler flowrate is 21LPM then the boiler return will be 53.3C, now the difference (53.3-49.7), 3.6C might seem very little but if the boiler is just hovering in the condensing state then it can become much more significent.
If one had a UFH system then there are huge condensing gains to be made, A 10kw UFH system with the same boiler flowtemp/flowrate of 65C/21LPM and a manifolf flow/return/temp of 54/44C, flowrate 14.3LPM will return 6.51LPM to the boiler but because the boiler flowrate is still 21LPM then the boiler return temp will be 58C, if its flowrate is reduced to 6.51LPM then the boiler return will only be 44C, which will have a huge effect on condensing.

 

[Mottie]

so I changed d.00 to 28kw. The speed of the boiler immediately increased and the modulation level went up to 4. I am now finding that the boiler flow temp is reaching the boiler target temp of 65C and the rads are heating up nicely.

Hurrah! My guess was right. Then again, even a blind squirrel will dig up a nut eventually!

 

[Johntheo5]

Hopefully, that will permanently "cure" the problem, this bug has been a Vaillant feature for years now, there is no reason why you shouldn't be able to run in either Auto or range rating mode, if there is a controlled temperature ramp up rate then it should apply and work in either mode.