Nest Hello: UK installation

Elliot West
3 min readJun 16, 2018

When I had my UK home refurbished a few years ago, I had Cat6 installed to the front door in anticipation of future developments in internet connected doorbells. I expected that PoE would be a likely choice to power such a device, and it was already supported by Doorbird, a nice device but with some quirks I couldn’t live with. The old AC doorbell was removed and a cheap wireless unit was installed to tide me over.

But the future proved me wrong. I’ve recently purchased a Nest Hello, and was surprised to see that connectivity is purely WiFi based, and curiously, it expects a 16–24V AC supply. No problem I thought, I can simply install an appropriate transformer and chime, and run the power over the Cat6. What quickly became clear however, is that while 16–24V AC doorbells may be common in the USA, it doesn’t seem that this was ever used by equipment in the UK which generally seems to favour the Nest unsuitable range of 8–12V AC. My attempts to purchase compatible chimes also seems to support this; no one sells them. I have found a rare example of a bell transformer from Screwfix that has a 24V output, however, without a suitable chime my Hello would remain silent.

To work around this I put a relay in place of the chime, this then provides a volt-free switch to trigger a doorbell circuit running at a different voltage. Sourcing a suitable relay was very easy as those with 24V AC coils are common.

Rube Goldberg

For the chime I used a modern wireless doorbell set from Honeywell, ironically with an adapter intended for retro-fitting to prehistoric wired doorbell pushes. Of course in my case the ‘legacy’ bell push switch is being emulated by the volt-free relay contact.

This whole situation is mind boggling; in what I can only imagine was an attempt to produce a product with broad compatibility with existing USA wiring, the Nest Hello is not only incompatible with probably every home in the UK, but also requires a non-trivial bespoke installation with a ‘difficult to find’ component.


The customer experience could be somewhat improved if Nest had done one or more of the following:

  • Included a suitable transformer to power the Hello
  • Added a volt-free contact option to the chime connector for easier integration with existing chimes running at other voltages
  • Provided the option of a wireless chime, preferably something ‘direct’ that doesn’t require additional infrastructure (so as not to be reliant on the owner’s WiFi network)
  • Bet on the future with a Power-over-Ethernet option

Given these hurdles, it’s hard to imagine anyone having an easy install experience in the UK. There’ll be a lot of head scratching going on, and I expect Screwfix will want to increase their stock of transformers.

Bill of materials

  • BRITISH GENERAL CUB1–01 24V AC Bell transformer (Screwfix)
  • REPOL 24v AC 8 Pin Relay 2 Pole (CPC)
  • REPOL GZP8-BLACK 8 pin relay base (CPC)
  • Honeywell Wired to Wirefree Convertor Kit c/w Doorbell (TLC)
  • HYLEC DN16T enclosure with DIN rail (CPC)
  • DIN rail clamps (CPC) — I used 2


I’ve recently invested in a Google Home Mini. This integrates well with the Nest Hello, providing ‘bell’ like functionality and some limited visitor announcements. The sound output if surprisingly high and I probably would consider this simplified approach if installing again. The Home Mini is often on offer, available for as little as £30.