Isn the Grant Multipass boiler as efficient?
The Multipass was ahead of its time and is one of the most efficient non-condensing boilers available today. However, to achieve very high efficiencies – as in condensing boilers – it is neccessary to reduce flue gas temperatures to a point where they condense. As standard oil boilers are constructed of mild steel, corrosion would occur if they were continually operated at these lower flue gas temperatures.
