Views on Heat Input - Vaillant EcoFit Pure System boilers

[EvilDrPorkChop]

We fit a few Vaillant Ecofit Pure system boilers, usually the case when an old Heat Only boiler goes and we replace with a system rather leaving OV, better all round solution. Ecofits are great as they're rear flues and fit in cupboards.

So when replacing we usually replace like for like in terms of heat input, usually as they're correctly sized and you're tied to what the current gas main is. Many are 15/18kws which are on 22mm runs then the last bits 15mm - fine if boiler is 18kw.

So the Ecofit Pure range if you buy a 18kw boiler it'll actually output 25kw on P.01 mode. This is the only time it'll ever do this or if you use Vaillants own controls to do HW priority. It'll only ever output 18kw on heating or when in Chimney sweep mode.

So my question really is, how would you size your gas pipe? If you're fitting what's advertised to do 18kw, it'll only do 18kw in heating mode (And for instance if you're replacing an 18kw boiler) but it'll do 25kw in p.01 test mode then what should you be sizing your gas pipe for? My argument is really that you would size it to 18kw but i'd be interested to hear what everyone else thinks?

Luckily on all the ones i've fitted it's been just within the inlet allowable range. It did puzzle me on my first one why it was 25kw and not 18kw when I gas rated! Should add that this only applies the to EcoFit range and not any of the EcoTec Plus system ones.

 

[Aire]

Problem is when commisoning the boiler it's going to ask you to put into maximum rate using p.01 mode. If you can't reach the desired operating pressure during commisoning then you can't properly commsion the boiler. You've also got a potential future problem if the customer upgrades their controls to the vsmart and you haven't put a large enough gas pipe in then the boiler could be under gassed. For me id be putting a 22mm supply in at point of install instead of risking getting called back to do it in the future.

 

[Scott_D]

Which controls allow it to give 25kw on hot water?

 

[ShaunCorbs]

Maximum gas usage so maximum input for me

 

[EvilDrPorkChop]

The Vaillant Controls when paired with their wiring centers. It'll allow HW priority in with them controls, hence the 25kws for quicker reheat. The 25kw version actually will do 30kw! Bit a of headache when all you really want to do is replace like for like.

On the bottom on the boiler it'll actually shows like it would on a Vaillant combi. E.g Radiator = 18kw. Tap = 25kw.

@ShaunCorbs I'd usually agree but i'm not overly sure on this one?

If it's never going to be used for that purpose then surely you could argue the boiler is 18kw. Especially when it says 618 on the front of it!

 

[Scott_D]

I have been looking for a bit of info on this as it would be handy for an upcoming job
15/18kw heating and more when the unvented cylinder needs reheating
I can’t find anything about it on the vaillant website or in the pure MIs

 

[EvilDrPorkChop]

I have been looking for a bit of info on this as it would be handy for an upcoming job
15/18kw heating and more when the unvented cylinder needs reheating
I can’t find anything about it on the vaillant website or in the pure MIs

It'll work when using Vaillant Controls and their own wiring centre (A VR66) as it'll do HW priority. The increased output only applies to the pure range, and i'm not sure if it only applies to the system boiler range as I've not done any Heat Only Pures.

I'm not sure whether you need the cylinder temperature probe (Vaillant VR10) or not for it to do the increased output however If you are using a VR66 it would make sense as you can control the temperature of the cylinder with the boiler. - Vaillant said you can't use the probe with other cylinders however I have but as a fail safe I have left the high limit stat wired in with the zone valve so if the probe fails the high limit will still as a cut out.

You can then set the KW output in HW priority (Under the D. settings) to suit what your coil is. The MegaFlo cylinders will do 24kw I know but I think some others are less.

I have HW priority on my own system that i've wired myself - it does help reheat times especially in winter.

Hope that's of help?

As a side line to my original question - I was looking at the data plate the other day on one I was servicing. And it says in small print the High Output is ONLY when using the Vaillant controls to use the HW output function. Guess thats make your own interpretation of the output?