I'm and architect and have a Gloworm Ultimate 120FF which has worked reasonably well for 9 years but I've had to replace the fan and the control board and now there is a problem with the electrode. It's a sealed system operating part radiator circuit and later installed underfloor heating circuit through blending valve. We need every kw of the output and I would like to replace with a condensing heat only boiler of similar output. I looked at Viessmann earlier this year and am keen to use the 100 but max output is well short of the 35kw I need. The Gloworm Ultracom HXI 38 & EcoTec Plus 438 are possibilities but after reading earlier posts everyone seems to favour the Viessmann. 'Which' have compared boilers and the HXI is highly rated but I guess my own experience of Gloworm to date says it all. Does anyone know of a good, reliable, 35kw or more output, heat only, gas, wall mounted boiler which will fit the bill (and the space) without having to completely rebuild the system.