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Tony Had one of the senior Vaillant engineers spend 2 hours today on the boiler & VRF430f. End result is that it will run at max power without cycling, but the short run to DHW did mean that the auto bypass needed to be left wide open in order to maintain <30C delta between flow & return...

I have used the online heat loss calculator and get 18kw, but that's well at odds with a 2400sqft detached house on a hill, 26 windows, 18 radiators & 250L unvented cylinder, which does work out around 28-31kw. The rads alone are about 28 kw as some are beefy, but there are a couple of long...

Tony, I have a new 428 and have been having great fun with cycling issues. However I can observe that if d.0 is set to 18 instead of default 30, the start up firing is much quieter (right from the start) than when it's set at say 24 or 30. I can only assume from this that d.0 does set the...

I had the same on a downstairs rad. I was told this was symptomatic of crud settling in the radiator. I had a powerflush clean recently and it has made a huge difference.

Yes 22mm when possible (used about 30m in total), but 15mm on old existing runs to far bathroom. All cold water outlets (including kitchen) coming from the "3.5 bar" PRV. Stopcock is old one. Today the Water Board measured inflow at water meter point: 3.5bar 30l/min. Measured at garden tap...

Hi 1st post, looking for a little advice from the professionals ...this rambles a bit, sorry. 30 year old gravity fed system died last month. Of the various options (fully pumped & keep old tank, big combi, or unvented) I went for what was advised as the "Rolls-Royce" solution: Vaillant...