I'm looking at a couple of these "add-on" controllers - such as the Beckett HeatManager
Does anyone have any direct experience? Actual cost of unit and actual savings?
They claim to save 10-20% on fuel consumption - one supplier even guarantees a "buy back" if you don't save at least 10%.
The basic theory seems to be that the units "hold off" a call for heat based on the heat load (as determined by rate of cooling), thus capturing residual heat stored in the boiler/system before allowing the burner to fire. Call for a firing by the Aquastat for domestic hot water (tankless system) put the units in bypass mode.
The web sites have lots of glossy brochures, and slick testimonials, but I'm looking for real user experience.
Thanks for info!
Grov