Oversized boiler - efficiency issues?

[Agile]

Steel, rather than posting useless comments, why not help the OP with your experiences of passing ABVs?

I am the first to admit that I don't know everything, and stated above, that I have never encountered any problematic Vaillant ABVs.

 

[Steelmasons]

No shame in checking or trying to obtain further information from a manufacturer for non routine matters.

The OP's keen interest in his boiler performance would make one expect that he would have engaged someone very familiar with Vaillant boilers although he was only described as a Gas certified gentleman!

Because the internal adjustable bypass is a rather Vaillant feature, then I would expect anyone regularly installing and servicing the boiler to be pretty familiar with them and not to need to call the makers.

I'll take you to a few sites we attend and remove the boiler manuals from plant rooms , I'd enjoy watching you crack on diagnosing/repairing without any reference material.
As I've said before , you obviously suffer with an inferiority complex which is the reason why you constantly perch yourself on the imaginary pedestal of yours , just give it a rest FFS.

 

[Steelmasons]

I am the first to admit that I don't know everything, and stated above, that I have never encountered any problematic Vaillant ABVs.

You don't know much at all with regard to the plumbing/heating/gas industry , any advice you give would have been gleaned from others.

 

[Steelmasons]

Steel, rather than posting useless comments, why not help the OP with your experiences of passing ABVs?.

I've tried to help the OP although it falls on deaf ears as he is looking for an easy fix that doesn't exist.
There won't be a hydronic system on the planet that could maintain a constant deltaT with variable loads.
With regard to the 'useless comments' take a look at the nonsense you constantly spout to which has no relevance whatsoever with the subject in hand.
You're a charlatan of the highest order , you posses an "air of authority' when posting within the open forum although this doesn't happen when posting in the closed part of the forum where the experienced gas peeps hang out.

 

[Steelmasons]

Agile , you still haven't explained how you managed a 10:1 turndown ratio on that Vaillant Turbomax.
You have been asked numerous times now to which you don't acknowledge , this says an awful lot about someone , especially when trying to BS.

 

[ianniann]

The quick fix has been described several times. Get the return temperature below 57C, and ideally the flow temperature also. This is the way to get maximum condensing inside the boiler. We already know that the temperature differential in your system is quite low so you'll need to drop the flow temperature right down to 57C or as close to it as you can stand. With legacy radiators, your house will take longer to warm up so put the heating on a little earlier. People often say their house won't heat up at these low flow temperatures, but what they usually mean is just that their house won't heat up as fast as they're used to.

FWIW, 1,000 pounds for just about heating a five bed house is pretty normal. Short of turning the temperature down more, you aren't going to get any drastic reductions without major outlays (or ditching the CH and huddling round a fire in one room, ahhh, back to the 1960's). Particularly if it is just you in the house, the old cliche of two jumpers is a good one - and of course turn the thermostat down.

P.S. There has been some discussion on the condensing temperature depending on all sorts of things like humidity and air pressure. All this is pretty much irrelevant. The mix of gases passing over the heat exchanger is CO2 and water resulting from combustion (small traces of oxygen, CO) in fairly fixed proportions. The dewpoint of this combination is always near 57C, based on the standard fuel/air ratio used in gas boilers.

 

[Steelmasons]

Whenever my Stafordshire Bull Terrier clocks a cat the hairs on the back of her neck stand up , this is exactly how I feel when reading Agiles posts.