The Efficient Home Forum

Hi all, hoping someone can help with a bit of knowledge

We have quite a simple system as follows

1) Pressurised hot water cylinder with standard system boiler
2) total 7 radiators all with HR92's
3) Single zone underfloor heating system
4) A total of 3 actuators, one each to control hot water, radiator circuit and underfloor heating manifold.
5) 3 BDR91's, one for each actuator

I have set up the hot water system following the video for the S plan/ Y plan system. No problems following set up, the hot water can be independently controlled as expected

I have then introduced each of the 7 HR92's using the manual process (not guided configuration), Again the system works fine, each radiator is independent and each HR92 controls the BDR91 for the radiator circuit. This is independent from the hot water control, again all as expected.

I have then introduced the BDR91 controlling the underfloor heating circuit and set it up as a zone valve. This does not behave as I would expect. When the underfloor heating is turned on the radiator circuit is also activated, even though the HR92's are not calling for heat. This only happens when I turn on the underfloor heating, I can call for heat from the HR92's and this only triggers the radiator circuit (as expected)

I have had the system operating correctly in the past when only using 1 x HR92 which was setup as a zone valve. The problem has now only occurred when i have tried to introduce more HR92's and set the system up following the forum video for setting up an S plan / Y Plan system

Any advise greatly appreciated.

Hi Ricky,

OK, so firstly setting up a technology 'type' incorrectly can cause evohome system issues... Therefore setting up a HR92 as a 'Zone Valve' zone instead of a 'Radiator Valve' is not what I would advise.

However, this is not the cause of your issue... When you add multiple HR92's to a system, you change the very nature of how evohome operates and needs to be configured. If you look at the evohome Installation Guide Page 43 Figure 4 this is now the system you need to configure.

So for your system to operate correctly you would need HR92's on all radiators, the motorised zone valve for the radiator circuit is then electrically disconnected and left in the manual open position (there is no BDR91 for HR92 controlled zones in an evohome Figure 4 system). The UFH zone is bound as a 'Zone Valve' zone and the Hot Water is paired in as a 'Hot Water Only Valve' option, NOT as the '2x 2 Port or 3 Port Valve' option.

I hope that helps and any questions please let me know.

Thanks,

Richard