Quote Originally Posted by Drpepper View Post
Interestingly a couple of evo certified installers have now both told me that as I have HR92s on all but two rads (recommended at time to ha e two without), there's no point having the CH valve at all and the BD91 should be wired directly to the boiler for demand as the HR92s control the opening and closing process at a rad level.
That would only be true if you had HR92s on all of your rads (and an ABV).

Without them, if you did as you've described, you'd have those rads coming on every time your hot water tank needed a top up, even on a sweltering hot summer day.