Introduction

The Outbuildings are getting a Vent-Axia Lo-Carbon Sentinel Kinetic BH MVHR unit which will ventilate the heated-and-insulated half of the building. There will be Extract vents in the Shower Room, the Utility Room, and the Plant Room (one in each) – and Supply vents in the Workshop (three). The Vent-Axia unit is rather less fancy than the PAUL Novus MVHR unit in the House, but should be capable enough for its less demanding role – especially since any fan noise or inter-room noise transmission is really not an issue. The replacement filters are much cheaper than for the more ‘advanced’ MVHR units.

These Vent-Axia units are relatively common and several other people have explored the options for integration with home automation ‘hub’ applications such as Home Assistant. The manufacturer has also been helpful in publishing documentation that describes the (limited) integration capabilities – most notably this: Sentinel Kinetic Range BMS Capabilities (PDF). There is no option to (directly) control the unit via a smartphone app.

Integration Options

In summary, the integration options boil down to:

• Using the 230V ‘Switched Live’ input to trigger a ventilation Boost cycle
  • This input is intended to be connected to a light switch in a bathroom – the same as a standalone extractor fan might be connected to a bathroom light
  • The Switched Live wants to be from the same 230V circuit as supplies the Non-Switched Live – which would not normally be the case; Vent-Axia offer an Isolator Relay Controller which can address this
• Using a momentary dry-contact input on any one of the SW1 – SW5 terminals to trigger a ventilation Boost cycle (when the unit is running in Control Mode 1)
  • These are intended to be connected to momentary wall-switches but can be any input that ‘behaves like one of those – such as a relay driven in a short on-off cycle
• Using a persistent dry-contact input on one of the SW1 – SW3 terminals to force Low, Normal or Boost ventilation for as long as the input is active (when the unit is running in Control Mode 2)
  • Typically connected to relays controlled by a BMS or Home Automation system
  • Terminal SW5 can also force the unit to stop completely – primarily intended for integration with a fire alarm system
• Using a 0-10V analogue input to emulate a CO₂ or Humidity sensor and control the fan speed accordingly
  • This allows for more fine-grained speed control than the other options – rather than just the pre-set Normal and Boost speeds
  • The equivalent input on the PAUL Novus is used to enable Home Assistant to control the fan speed on the House MVHR – although that is the only available integration mechanism for the Novus
• Using a microcontroller to emulate the Vent-Axia remote keypad, which can select from the Low / Normal / Boost settings or trigger a timed Boost cycle
  • See the code for vent-axia-bridge on GitHub, which provides access over WiFi; the accompanying documentation is very limited

Conclusion

All of these options (apart from the last one) could be robustly integrated via KNX module(s):

• Using a KNX ‘switch actuator’ (i.e. a relay bank) module for the relay inputs – ideally with 4 channels (to cover all the ‘Control Mode 2’ SW1-3 and SW5 inputs)
  • Either a standalone 4-channel module – with separate terminals for each channel: something like the MDT AKS-0410.03 (Switch Actuator AKS Standard 10 A) or the MDT AKK-0416.03 (Switch Actuator AKK compact)
  • Or 4 channels of a larger relay bank, which might also provide relay inputs to e.g. the alarm system
• Using a KNX ‘analogue input / output’ module for the 0-10V input
  • Either one of the MDT KNX AIO modules should be suitable; about £75 for the 2-channel module

The main question is whether there is any real requirement to force the unit out of ‘Automatic’ operation – given that its built-in scheduling options seem reasonably comprehensive. Some owners report that they had multiple (manual) ‘Boost’ switches installed but never use them.

As the MVHR unit is being installed in the Plant Room, that’s the easiest location to retro-fit any of the integration options. Probably best to see how it performs with just its built-in controller before planning to integrate it.

Vent-Axia Sentinel Kinetic MVHR Integration with Home Assistant by Marsh Flatts Farm Self Build Diary is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.