Hi all My Glowworm Swiftflow 125e combi boiler is getting the boot at 8 years old after 5 years of major and minor problems that the maintence techs from my insurance policy cannot seem to solve. So After doing a bit of research I have decided to fit a Worcester Greenstar 30CDi for my 3 bed semi with one bathroom. My choice of the 30 CDI was based on its DHW supply capacity (12.6L/ Min@35c rise) and the power control knob avilaible for it, so that during the summer I could reduce the power setting. This would allow the hot water flow to the shower to be kept high with a lower temperature rise to prevent boiler cycling. Also I do like a good flow at a high temperature into the kitchen sink. I have had a few quotes and all the engineers (recommended installers from the B-W website) never disagreed with my choice of boiler or suggested an alternative, until yesterday. This engineer guessed at an 11L/Min flow into the kitchen sink and suggested a 28i boiler (11.4L/Min@35c rise). He said I would not see any benefit from the extra power as my water supply did not have enough flow and (if I understood him correctly) the 30CDi would not run at maximum efficiency because it would continually modulate the gas supply. I thought this was the whole point of modern combi design but is the boiler efficiency reduced when the burner modulates (cars are very fuel efficent at 56mph but can go faster). I measured the water flow at the kitchen sink at 12.5L/min cold tap only and 18.5L/min hot & cold together. The two boilers have very different heat exchanger designs and the 30 CDi is a much more complex beast than the 28i. Does any know if there are any reliability issues with the Greenstar
30CDi, is simpler better? Is the flow to my sink enough to make the most of the 30CDi or would I be just as well off with the 28i? any advice would be welcome. cheers ian- posted
16 years ago