Biomass Boilers

Basquelle

Something to watch out with bio fuel is the modulation range.  Gas and oil operate effectively and efficiently over a huge modulation range, 10% to 100%, ie, a 30kW boiler can work anywhere between 3kW and 30kW (figures are not exact, it's been years since I was involved, but they're somewhere about right).

Biomass modulates between 80% and 100% only.  Below this, it becomes very inefficient and polluting.  So the 30kW boiler can only work well between 24kW and 30kW.

Because of the high modulation range and the low-per-kW-installed cost of fossil fuel boilers, plumbers have become lax with heat calculations and simply bang in over-size kit.  They had no reason not to.  But if you are being quoted the same size bio-fuel boiler as your gas boiler, be suspicious.

You should expect a bio-fuel installation to include heat loss assessments, and there should be a discussion about the highs of winter demand and the lows of summer.  A good installation may not cover the usual winter low, I think it's -5°, they may only run down to 0°, with an expectation to make up the difference on the coldest days with fan heaters, and in summer, to switch off the boiler and use electric immersion heaters for DHW.

Without these compromises, bio-fuel will not deliver the expected benefits or performance.