Time for Ecotec 615 Plus to achieve set flow temp?

[copea]

I have a recently installed Vaillant 615 Ecotec Plus boiler and a 170L Heatrae Sadia / Santon Premier Plus indirect cylinder.
It's wired up to a standard S Plan system - no weather compensation.

The boiler was specced having done a whole house heatloss calculation and is slightly smaller than the inefficient Ideal Mexico it replaced (15kW vs. 16.6kW).

There are nine radiators in the system in total.

It seems to me that the new boiler takes an age to achieve the set flow temperature of 68°c.
Sometimes it's not even achieved 45°c after 20 minutes of call for heat.

Having watched the display when it first responds to the call for heat, it seems to modulate down almost immediately after firing - before the temperature has had a chance to rise more than 8 degrees.

Should it be doing this? I could understand it if the flow temperature rose to somewhere near the set temperature and the boiler modulated down so that it didn't exceed it, but seemingly this isn't the case.

If it's left for a good long period of time it will reach the set temperature and maintain it, but in my opinion it seems to take too long to do this.
Other times it achieves the set temperature after 10 minutes, so there's no rhyme nor reason to it.

Anyone any ideas, or is this normal behaviour?

Thanks!

 

[Steelmasons]

Possibly been left in 'auto' mode within D.0. , change to manual setting.

 

[copea]

Thanks, I had read about changing D0 when Googling what might be causing this, but only in the context of downrating an oversized boiler.
I'll give it a go and see if it improves anything.

 

[wannocks]

The auto function can take a while to learn your heating system. It will work better and faster if you set D0 to the correct output for your system. It also helps to set your hot water to come on half an hour before the heating so that it isn't heating both at once from cold.

 

[Bunnyman]

U need to check the live status sounds like s53 to me circulation fault

 

[copea]

Thanks gents.
I've changed D0 to 15kW and it's now performing as I expected - full tilt until the set flow temperature is achieved and then modulating down to hold it at that temperature.

Bunnyman, I did check the live status before posting and there was nothing untoward there - just whatever the code was for 'burner on', I seem to remember.

 

[Dan Robinson]

Don't know why Vaillant ever bothered with auto mode.

It is crap.