On 24/03/18 19:25, Harry Bloomfield wrote:
I have decided my Ideal Icos HE18 is beyond sensible repair cost, I have
chucked enough at it, so I am looking now for a replacement...

It needs to be a regular, vented system type boiler, but if possible
with separate boiler output temperature controls when heating the hot
water tank, to that when heating the radiators. Yes I presently have a
room stat and a water tank stat. I just like the hot water to be able to
be very hot 80C, I appreciate that is above the efficient condensing
range, but to heat the radiators the boiler output temperature need not
be quite so hot. 18+ Kw needed as present boiler is adequate. The
predecessor to that was around 32Kw, but some good insulation has made
that high an output unnecessary.

I had no input into the boiler make last time around, this time I am
looking to Vailant or Worcester/Bosch for a more reliable boiler.

I heavily researched Viessman and Worcester Bosch:

I went with WB, but I would not be that unhappy with Viessmann either.

Pros and cons (WB substantiated, Viessmann is based off anecdotal
evidence and on paper specs - at least one person here has a Viessmann
and will probably comment)


WB:

1) Highest DHW output for a wall mounted unit;
2) Reasonable price;
3) Easy to wire and operated (either dumb knobs or LCD depending on model)
4) Quiet and well behaved;
5) According to my Gas Fitter, WB parts are quicker to get hold off than
Viessmann, maybe because it's more common???? *Anecdotal*


Viessmann:
1) Weather compensation that WB don't have (unless you buy their fancy
controller that precludes using your own controls) - you only need add
the sensor to a north wall (or shaded area I assume);

2) Slightly more "Waitrose" than WB's "Sainsbury" - stainless heat
exchanger supposed to be a selling point.


I went WB mostly because it had enough DHW power in theory to run a
shower and a bath (latter is throttled to 20l/min by flow restrictors).


I do miss not having weather comp, but I have measured the flow and
return temps for each number on the knob - and have a rough manual scale
of "this time of year, turn knob to 4" kinda thing.