Hi all, been lurking for a while, but I finally bit the bullet on an evohome setup recently with the evohomeshop BOGOF deal on 4 x HR92 packs. My old system was a very basic room stat in the hallway connected to our bullet proof 8+ year old WB Greenstar CDi 30 (branded British Gas 532/i) with a couple of non-TRVed rads acting as bypass.

Our new setup is:

Evohome ATC928G3000 controller
BDR91 located in airing cupboard, couple of feet from boiler
Cloakroom zone: 1 x HR92
Hallway zone: 1 x HR92 + T87RF2033 as sensor
Lounge zone: 3 x HR92 + T87RF2033 as sensor
Kitchen zone: 1 x HR92
Bathroom zone: 1 x HR92 + non-TRVed towel rail
Bedroom 1 zone: 1 x HR92
Bedroom 2 zone: 1 x HR92
Bedroom 3 zone: 1 x HR92

Everything went pretty smoothly with setup, I still need to do some tweaking as we learn comfortable setpoints for various zones, but so far seems to work fairly well, no wireless issues or anything like that.

The main issue we're having right now is high pitched/unpleasant whistling from some rad valves, which we'd not had previously, and I just wanted to sanity check my thoughts on possible causes/solutions.

Thoughts on these notes pls...

- Only seems to happen when only one or two zones have open valves, ie when it's heating whole house from cold then no whistling
- HR92 heads might be holding the valves open at much finer positions (e.g 10% open) than would have happened with the clunky old heads.
- We've reduced the "bypass" volume of un-TRVed radiators from 2 (hallway and towel rad in bathroom) to 1 (bathroom towel rad only), increased speed through open valves.
- Due to above, is maybe the pump cavitating when it's trying to push hot water round the system to only one rad and creating fine bubbles which contribute to whistling noise? Pump speed too high?
- I've checked boiler pressure gauge while it's got only one zone in demand and rad valves are whistling but it doesn't increase, stays pretty stable between 1-2 bar which is normal operating pressure.
- Some of my TRVs appear to be on flow side and some on return, it doesn't seem to make a difference to which rads whistle. All valves are "bi-directional" too.
- I checked/lubricated all of the TRV pins before fitting the HR92 heads, and confirmed they open and close the full range with the black wheel. So I know none of them are physically stuck.
- I have bought an ABV which I plan to fit later this week (although I would imagine that the towel rad would offer enough more "bypass" on it's own than a valve)
- Can reduce/remove the whilstling by removing the head and moving the black wheel a little in one direction or another.

Thanks!