Turboburn Monitor part 2

Our TB4 snug inside its shed "in the bleak mid-winter"

This picture was taken just after stoking. Once the fire has got up to temperature the amount of visible smoke emanating from the chimney drops dramatically.

The beauty of the Turboburn boiler is its simplicity. Apart from the amount of fuel, the only boiler user-variable is its fire-box fan. At the simplest level this could simply be left on 24/7, but having the fan on with no fire blows heat out of the chimney. Also, turning the fan off before a fire has burnt out may damp the fire sufficiently to avoid unnecessary boiling.

In Part 1 of this series I mentioned that Frank supplied a 2-hour mechanical timer and a 95 degC thermal cut-out. The idea of the 2-hour timer is to ensure the fan turns off if the boiler is left unattended, 2 hours being a typical time for a fire-box full of logs to burn out.  The cut-out is a fail-safe should the water get to boiling point. So I mounted these two controls in a box, outlined in red in the photograph below, this position being in front of two available thermometer pockets Frank had inserted into the boiler water-bath.

The house heating system has its own controls of course: the circulating pumps and zone diverting valves are controlled by a room-stat and programmer (timer). The hot water is controlled by a cylinder-stat and the programmer.

Our boiler is located a good 50m walk from the house and that's far enough to make one think twice about checking the boiler especially when the weather is inclement. So my first enhancement was to echo the boiler fan circuit to an indicator lamp and to install at the boiler a thermostat-switch set to about 50 degC which lights a second indicator lamp, these lamps being located by the heating controls in the house. Thus we can see without leaving the house whether the fan is running and if the boiler temperature gets very low.

My next enhancement was to add a relay to automatically switch over to the oil-fired boiler and immersion heaters when the Turboburn temperature falls below the 50 degC. This switch-over only occurs if a switch is set. So far we have used this feature only once - it was in the early days before we had figured out how much wood to stoke and whilst we had a bunch of American visitors (these Americans were allergic to our Irish weather).

With a little experience one can gauge how long the boiler will run on a given amount of timber and about how many degree it will increase the water-bath temperature, all other things being equal. But all other things are seldom equal: during the night when the heating is off the temperature hardly drops at all, but when all heating circuits are demanding the temperature plummets. Even when the programmer has timed the heating to be "on" it is difficult to predict when the room-stat will be demanding. If you have stoked the boiler expecting the heating to stay on, and then the room-stat turns if off, the water-bath temperature might soar. Or conversely you might think there was enough heat to last and then someone hits the "boost" button on the programmer.

Enter "Turboburn Monitor". This is a box of electronics which I created from a dormant work project, mounted on the side of the boiler.  This box is outlined in yellow in the photograph below - double-click the photo to enlarge it. The box is connected to seven temperature sensors around the boiler and two relays in the main control box (outlined in red).

Our TB4 boiler with conventional control box and TurboBurn Monitor

Inside the box a PIC32MX microprocessor acts as a web-server and is connected by CAT5 cable to our local area network (LAN). We were able to pull the CAT5 cable through the 4" duct Frank had thankfully insisted we bury with the pipes for such a time as this.

Any web-browser (e.g. a smart-phone) connected to the LAN can surf this embedded web-site to display the boiler status and optionally over-ride the 2-hour timer.

Turboburn Monitor main screen in the morning

The first screen-shot was taken shortly after 09:00.  The boiler was not fired during the entire period shown. You can see how well the boiler retains its heat during the night when there is no demand, and how the temperature starts to drop as soon as the heating comes on at 06:30.

We have the seven temperature sensors fitted as follows:

•  one in each of two boiler thermometer pockets: the software takes the highest reading
•  one 'outside' in a plastic box mounted on the outside wall of the boiler-house
•  the remainder affixed to the copper flow-pipe about a metre from the boiler on each circuit: main house heating, main house hot-water, courtyard heating (not yet working) and courtyard hot-water, thus a sensor reads high when that circuit is demanding heat.

An hour or so after lighting the fire

The second screen-shot shows a steady decline during the day (today - Sunday - so the heating was on most of the time) until the boiler was stoked at 14:33.  We usually leave stoking until about 4pm - I guess Joe decided to light the fire earlier today because he had noticed, from this software app, that the temperature had dropped as low as 60 degC.

Turboburn Monitor "Settings" page

The web-site has a second page accessed by clicking the 'Settings' button. Here you can turn the fan off if it is on, or on if it is off, and synchronise the web-site's clock which isn't battery backed in this version.

Turboburn Monitor has proven to be most useful and the various people here who stoke the boiler like it. But most of the time it is used only to remotely gauge the boiler temperature.

Clearly it could do more.  It was built "upon" Frank's existing 2 hour timer control but, if I were starting from scratch, I would replace the mechanical timer.  Thus the new Turboburn Monitor would do all that the existing version offers PLUS:

• local display of boiler temperature and trend
• local control buttons to activate / deactivate fan
• software algorithm to detect when fire goes out, kill fan and send prompt to designated stoker-person
• software algorithm, taking as inputs the flow-pipe temperatures and outside temperature, to estimate
• send prompt when boiler temperature drops below say 55 degC
• automatic kill fan when temperature exceeds say 95 degC and send prompt
• provide battery backup at least of the real-time-clock

The prompts could be by text or email as well on a banner (that has to be dismissed) across the web-site main page.

I imagine the same concept would apply equally to any solid-fuel boiler that needs monitoring from a distance. We have it in mind to further develop the idea as outlined above and to make it available in "kit" form (since inevitably every installation will have differing requirements). To register your interest without any commitment please send an email to tb4monitor at gmail dot com (replacing the ' at ' with @ and ' dot ' with . unless you are a robot!).

Turboburn Monitor part 3
Turboburn Monitor part 1