Getting Started - Raspberry Pi & ZWave

Before buying any kit I took a brief look at the complete solutions on offer:

Heat Genius
Nest
Hive
Tado

I really liked the look of the Heat Genius solution and thanks to a demo available through a web browser or as a phone app I got to have a good play around. It uses ZWave as its communication protocol for which there are plenty of blogs around detailing diy-er's experiences.

J Heyman's Blog
Steve Prater's Blog
Darren Miller's Blog

The Heat Genius system consists of the following components (some of which are used by the bloggers above).

Controller (Heat Genius)
Master Thermostat (Horstmann HRT4-ZW  / Secure SRT323)
Boiler control (Horstmann ASR-ZW / Secure SSR303)
TRVs (Danfoss Living Connect)
Philio Multisensor PIR/Temp/Light

It has been around since at least 2014 and user experiences have been positive. Although the thermostat and phone app aren't as slick as those from Nest, Hive & Tado I think the functionality is better. I decided to model my own system roughly on that of Heat Genius and opted for a Raspberry Pi as a controller (mainly as I had one already). And by choosing some of the same devices I would always have the option to switch to the Heat Genius system if things didn't work out with my own design.

But before buying anything, I installed the zwave.me software on my existing Raspberry Pi image just to get a feel for what it involved. These were the instructions from the ZWave.me site:

First installation when Raspberry is already up und running
To download Z-Way for your RaZberry, login to your Rapsberry Pi box execute the following command:
wget -q -O - razberry.z-wave.me/install | sudo bash

This was a good sanity check to see if everything loaded okay before investing in the hardware. And in fact I managed to glean a lot more information just by poking around in the code than reading the documentation.

It had been a good few years since I had worked on a unix based system - the directory structure and commands largely a distant memory. Stepping carefully through the install process and seeing what processes were generated and where files ended up in the directory structure was an important step for me.

The most important directory and file changes made by the install script were as follows:

• /opt/z-way-server - where the zway software is installed and where any customization will occur
• /etc/z-way -  a depository for VERSION and box_type details
• /etc/init.d/z-way-server - a zway server startup script
• /var/log/z-way-server.log - anything that the zway system logs gets put here
• /etc/logrotate/z-way-server - z-way-server.log is added to the rotating logs

And the new processes created were:

• z-way_server - the all important ZWay server
• zbw_connect - for connecting to z-wave.me
• mongoose - provides a web interface (for upgrading the firmware?). It is not the same web interface available on port 8083

Next step, I bought the razberry daughter card and a Thermostat to play around with.

In the Beginning - The Central Heating

Our central heating / hot water is a standard system consisting of a boiler, hot water cylinder, thermostat (in the hall), programmer, 17 radiators (mostly fitted with TRVs), valves, pump and a tank in the loft. There is just one feed & return loop.

The programmer is used for both the heating and the hot water. It is set on a 24 hour basis.

Honeywell Thermostat	Honeywell ST699 Programmer	Potterton Profile 60E
Central Heating Pump	Typical TRV	Motorized Valves

In the Winter, the central heating is set to come on for a few hours in the morning and again in the evening with occasional boosts during really cold spells. When the central heating is activated, water is pumped around the whole house via a Grundfos pump.

Radiators are individually controlled by TRVs and are often left heating empty rooms - the biggest culprits are the living room, the utility room, my husband's office and the kids' rooms.

Hot Water Pump	Hot Water Timer

In addition, the hot water has a separate timer which is used to operate a pump responsible for delivering water to the whole house. When we moved in, I assumed that this was just to speed up the delivery of the hot water to more remote parts of the house. However, the reality is, that without this additional pump being activated no hot water ever gets delivered downstairs however long you wait for gravity to do its thing. Much of the pipework is concealed, so it is difficult to see what is going on. Plumbers have been puzzled by this too.

If the boiler is off and the pump is left running, a cylinder of hot water cools quite quickly despite no water being drawn off. This would suggest the circulation of the water is a huge waste of energy.

There are three main things I would like to achieve:

1. Create separately controlled heating zones (possibly down to individual rooms)
2. Operate the hot water pump from downstairs only when required
3. Control everything from a phone or tablet