Continuing an old install - how many BRD91s?

[newbie2024]

A few years ago we started to first fix our gas central heatin as part of which all pipework was installed, boiler and cylinder installed and Evohome partially installed.

We purchased a 'Honeywell evohome Wi-Fi Connected Value Pack A' but then lots of things happened including the pandemic and it got put on hold.

We are now coming back to the install and want to control 20 x radiators. The kit previously purchased had 8 x HR92s and so we can't to get 12 x HR91s but the gas engineer who started it is no longer available. Looking at the install, I just want to make head or tail of it before we continue.

I've attached a picture of 3 x relay boxes which were installed (ignore the rest of the wires!) - to me it looks like there are 2 x BDR91 Wireless Relay Box and a hot water relay box.

Are 2 x BRD91s necessary?

[Somebody]

You need 1 BRD91s - one for hot water and the other for heating. The box on the left is a CS92 which is the sensor for the temperature probe from the hot water tank.

[newbie2024]

Ah, that's really helpful, thank you!

How does the temperature probe go into the cylinder?

[Somebody]

See page 5 & 6 of manual here: https://www.plumbworld.co.uk/documents/ ... -guide.pdf

[newbie2024]

The instructions don't seem to mention how to insert the probe into an unvented cylinder?

I have a Telford Tempest.