No-one seems to have picked up on the rating of a replacement boiler. If
the old boiler was 60,000BTU/hr and ther new one is also 60,000BTU/hr then
it will modulate "down" from there and never up past it. Thus the rate of
heat up at maximum will only be the same as before. (Give or take a little
bit for a cleanbrand new heat exchanger)


In the mist of a shed load of confusing remarks on this debate, someone at
last makes sense.