Control System Options

[TerryE]

I've posted a couple of related topics in the Boffin's Forum:

• An Aug 2019 topic: IoT / microcontroller based power switching.  
• And March 2020: Raspberry Pi based CH and HW control.

Some of my household services need an availability on a par with external utilities such as our electricity, water supply and sewage: our central heating (CH) and direct hot water (DHW) just need to work and be available without hiccup:  losing either of these systems would be a real hassle if the outage was greater than 24hrs.

 

I use a HomeAssistant (HA) system to integrate and to automate other IoT goodies stuff: e.g running various lights and timed appliances, together with a bunch of temperature / humidity and motion sensors, and a few smart button to sequence some of these.  However, for reasons discussed in the footnote HA is just too flaky for 24 × 365 service provision of critical services such as CH and DHW. 

 

In my view these require a separate dedicated and minimal system to run CH and DHW control.  There are many ways to achieve this, but some six years ago I opted to use an RPi3B with battery backup and SSD running a simple Node-RED stack and my own custom code.  This has performed flawlessly and non-stop for that time, and it still offers a lot of headroom for me to enhance the system.  I would recommend this approach to any other self-builder, if you have some basic programming skills.  However I am now about to switch to an Octopus Agile tariff (see this discussion), and this will require some changes that I will discuss in later posts in this topic.

 

One of the fey functional changes to my CH system is that I now use 3 small oil-filled rads to supplement my UFH during the colder winter months.  I used to control these from HA using Zigbee Smartplugs, but I can now remove this dependency on HA by switching to Athom Smartplugs with pre-installed Tasmota Firmware, as this will allow me to directly control and to monitor them directly from Node-RED using a couple of HTTP requests direct to each Smartplug.  Again, I can provide more details if anyone is interested.

 

 

Footnote: My View On Why HomeAssistant Is Just Too Flaky To Provide Critical Services

 

When I used to use an RPi to host HA I three had HA+RPi hardware failures that required me to rebuild and reinstall the system.  I ended up HA onto a VM hosted under Proxmox (an old laptop upgraded to 8Gb + SSD running closed) and this largely solved these sudden death events. 

 

The HA development team uses a monthly update cycle to minimise the delays in getting new functionality in use.  This means that new functionality is often not fully test and sometimes introduces breaking changes to an integrations and add-on module, or even another unchanged module which has an interdependence, but this means that any upgrade is game of Russian roulette.  At least the Proxmox functions to snapshot and restore VMs are a lifesaver as these take seconds to a minute to do, whereas a HA native restore takes a few hours.  If the bug introduced by the upgrade is a subtle one then it might be too late to roll-back to the old version once the symptoms become apparent.  For example, before we went on a long spring visit to Greece Jan went round turning off a lot of wall sockets — some of which were Smart plugs, acting as routers in my Zigbee mesh.  Logging remotely I could see that most of my Zigbee devices were now unavailable, and the Zigbee HA Integration marked these as dead.  No luck in reconnecting them when I got back.  The advice on the HA forums for this failure mode was to do a complete clean install,

 

I am annoyed but relaxed about all this because these devices are in the nice-to-have category, because we can always turn on and off lights the old-fashioned way.

 

In principle I could do all of my house automation in HA, but my view HA as serious issues for "production" use. 

 

Edited October 27, 2023 by TerryE

[Gus Potter]

Are you saving any money or just having fun playing with the tech, just like buying an old car?

[TerryE]

@Gus Potter, both, but definitely saving money in two ways: first in upfront costs during the build: our complete CH system including the UFH pipework in the slab came in at under £4K and that's for a reasonable 4 bed detached house (3 of which have ensuites and they are all decent doubles). The CW and DHW also under £4K.  Second in terms of maintenance and running costs, we don't have complex kit like UVCs, Gas boiler or ASHP or. expensive systems like Loxone that require a pricey annual maintenance contract with an approved maintainer.  We keep our house at just over 22°C 24×7, and we can only do that because the heating system is optimised for the house. 

 

And yes I do get a kick out of the intellectual side of modelling and designing these, and documenting them on the forum for others to follow.

 

Edited October 26, 2023 by TerryE