Vaillant Ecotec Combi with actoSTOR

[blakie8]

Thinking along the lines of the Ecotec Plus 937, which has the actoSTOR bolted to a Plus 837, was wondering if you could use the actoSTOR setup for a smaller output boiler from Vaillant like the 824 or 831.
My thinking is what they can modulate down to could make them more economical in the long run but also achieve a better Flow Rate.

Anyone heard of it being available, I've heard on the continent their used quite a bit?

 

[Dan Robinson]

Not sure to be honest. Certainly not an advertised combination.

Still a bit like hanging a washing machine on the wall though.

Have Vaillant sorted the issues with these? Or is a blending valve the key?

 

[blakie8]

I've never stored a washing machine in the loft but I guess it wouldn't hurt on the eye when it's up there?
Can you see what I mean about delivering more hot water but with the ability to modulate down further on the CH.

 

[Dan Robinson]

It is one of my bug bears with combination boilers.

 

[St0rmer66]

Your installer can *very* easily down rate the boiler using just a few button presses on that model (it's also readily available in the installation instructions). So that shouldn't be a worry.

 

[Bunnyman]

How low do u want the heating to go down to? The 937 is fine as it is if you have enough pressure on the mains

 

[David937]

The older 937 only goes down to about 12kW which is awful but as far as I can recall, the latest one can modulate down to about 5-6kW which is much better.

 

[Bunnyman]

That's correct , that's y I asked. U don't really need anything lower than that do you?

 

[blakie8]

Well its 3 bed semi currently with extension to rear. Max I need is around 12kw, but thats worse scenario in winter. I'd probably gues that i'd need below 6kw which is what they drop to

 

[St0rmer66]

Even a 15kw system boiler generally only goes as low as that though... They all use the same heat exchanger and burner etc.

 

[Dan Robinson]

Even a 15kw system boiler generally only goes as low as that though... They all use the same heat exchanger and burner etc.

Current 612 goes down to 3.2kw...... still too high imho.


I've been , looking for a decent system boiler to go down to 1 or 2 kw for yonks. All I can find is Geminox..... and won't be fitting any french crap that's for sure.

I've even tried modifying my boiler to achieve what I'm looking for, and it's harder than you might think.

 

[blakie8]

You can't have it all with a combi, oh well stick with an Intergas.

 

[Dan Robinson]

Keep an open mind.... you're already considering the 3 best products on the market. It is now just a case of pinning down the best combination of product.

 

[ScottishGasMan]

well by the sounds of it your obviously sizing the boiler with the DHW as your main priority.

What DHW requirement will you have in the house?

And to answer the question, no the 937 is considered one unit in this country and sold as that.

its only a 15 litre store in the boiler, so once thats depleted you will essentially get the same performance as that of a non storage 837 boiler.

If modulation on heating is a concern (they are different) 937 Storage combi is 6.8kw, a 615 sytem boiler is 3.2kw, What I would reccomend is a small unvented cylinder, with vaillant controls. Which means you could use a 615 (assuming 15kw is enough for the heating load) witch will switch between heating the cylinder and rads separately meaning you have the 15kw output focused fully on one or the other demand at once.

If you dont want to go down the line of using a cylinder, then Id say an 837 combi, (or a 937 Storage combi if you like) But realistically you cant have a boiler with a massive output and very low modulation.

 

[ScottishGasMan]

Still a bit like hanging a washing machine on the wall though.

Have Vaillant sorted the issues with these? Or is a blending valve the key?

Their not small boilers Ill give you that! Best make sure you have a good sturdy wall for it.

What issues are u talking about in particular Dan? Blending valve generally is very useful, the 837 and 937 are both essentially 40kw(input) combis, regardless of the aco store they both have 40kw of energy to put into the incoming cold water so essentially they both have the same flow rate/hw temp rise ability. the 15 litre store helps, as it can be pre heated to a pre determined temp, and with a blending valve fitted can keep the hw leaving the boiler at a higher temp (to get blended down anyway) which helps keep a steady flow rate. As opposed to a 937 without one, if you ran say 20 litres/min off it, the first 15 litres could be as high as 60*c but after that your down to less than a 30*c rise, so youd have to slow the hw rate down to keep the higher temp,