Turning Up The Heat

So the first of the main components for my setup arrived today, starting off with my new digital controller. This is manufactured by an individual in Australia and surprisingly only took a week to get here. It's called the "Afterburner" which some of you may possibly have already heard of. It massively extends the functionality of the basic controller panel that you get with most diesel heaters plus it enables control of the heater through Bluetooth, it's own wireless AP or can connect to your own WiFi network, allowing you to control the heater from your mobile device or a laptop or PC. Furthermore if you set up an MQTT broker, you can access and control the heater from anywhere in the world. I plan to integrate it with Node Red, so as I can control it through Alexa as well.

The version I bought has the GPIO option which lets me connect the controller to two digital outputs and two digital inputs, for example I can use the run status of the heater to switch on/off a fan, or monitor and alert me about the diesel tank level or reset the fuel gauge remotely, when I refill the tank outside plus a whole lot more. The manual that comes with it is very comprehensive and there is an active Facebook group that is full of great information and tips to get the best out of the unit. I won't delve any further into just how much this controller can do at this stage, but rest assured it is a very clever piece of kit.

 

So here is the steel PSU enclosure I bought. This is going to be gutted as the PSU that comes with it (as shown in the picture) doesn't output enough current to meet the demands of the glow plug in the heater during start up, so I've ordered another PSU which can comfortably handle it. I've also received the back up 12v battery which will also fit inside this enclosure.

The basic architecture involves a 240V mains powered PSU that supplies 12V to the diesel heater. In addition the PSU also charges a 12V battery which is on standby, purely so that if the mains power fails the PSU will instantly switch over to this alternate 12V supply. This in turn provides enough power to allow the heater to perform a 'graceful shutdown'. This is vital, as with all diesel heaters, they need to run a cool down procedure before they shutdown, which involves ramping up the glow plug current to burn off any remaining fuel then running the fan to cool the heater body to an acceptable temperature before finally shutting down. If not, you run the risk of frying the electronic ECU and/or some of the temperature sensors, if all power is cut to the heater.

I've also bought some vents to assist in cooling the PSU (which has it's own cooling fan) that I need to fit to the enclosure and I will also need some modifications made to the LED PCB (which drives the indicator lights on the door panel) that is connected to the new PSU, such that it will fit in position, as per the original one in the picture. I plan on adding another LED status light to this array as well, to indicate the fuel level, using the GPIO digital option on the Afterburner and an outlet for the external temperature sensor that connects to it. Ignore the legends on the door, as these differ for the setup I'm after, so I will replace them with more appropriate wording. The Afterburner controller will be mounted on the door panel, so I've got to drill a small hole in it, to allow it's wiring to pass through. I will post up pics as I go along to explain the enclosure build.

The heater itself is going to be built into a flight case which will be housed in a weatherproof metal enclosure and which will sit on a purpose made concrete base outside the garage. Ducting will have to be fitted through the wall to enable the warm air from the heater to be transferred inside and a separate IP67 external socket fitted to transfer the 12V supply from the PSU to the heater, as well as the wires to the ECU from the Afterburner controller and two separate 12V wires to run the additional flight case cooling fan. Sounds a lot more complicated than it is, but this is a tried and tested setup, that I've simply modified to suit my needs.

 

Been sorting out some of the wiring to make use of the GPIO functions of the Afterburner and how I 'think' the wiring should be, for the two GPIO outputs and the one GPIO input I want to connect. (3) GPIO OUTPUT powers an LED that indicates a fuel low status by measuring the total dosage count of the fuel pump and shuts the heater down if it reaches a predetermined level, so as you don't run the pump dry and damage it and have a flame out and need to prime the system again. (2) GPIO OUTPUT controls a relay based on the run status of the heater, that switches on a 12v fan that sits inside the flight case where the heater will be, to aid cooling whenever the heater is running. (1) is a GPIO INPUT reset switch, which will be outside next to the fuel tank, so whenever I refill the tank, I press it to reset the fuel usage to zero on the Afterburner and clear the low fuel LED warning. The second image is an addition to the first as I omitted to include a 12v supply to the fan.

The relay module has a built in diode to protect the Afterburner from back EMF produced when the magnetic field collapses in the relay's coil when it is de-energised (heater run status is OFF which kills power to the fan)

 

It's alive! Very apt picture BTW!

 

Second major delivery lands on 3rd January from the US. Should see me able to make a start on building the heater flight case enclosure. I am still waiting on some exhaust heat wrap but I already have a lot of the parts I need to crack on with.

 

Stripped down the PSU enclosure and drilled out two 35mm holes for the vents and two additional 20mm holes. One for the digital controller and one for the heater wiring output. There was already a hole for the 240V input and some back box knock-outs but I don't need to use them. After some sanding, I applied some smooth white Hammerite to the bare metal to protect it. Tomorrow I can start building up some of the wiring.

 

Here are the vents I bought for the enclosure, one will be at the bottom of the case and one at the top. These were siliconed into position and allowed to cure. They should assist in promoting some airflow in and out of the enclosure as well as aiding the PSU cooling fan.



Here is one of the two vents fitted, as well as the gland nut for the 240V mains input (right) and the conduit fitting (left) for the wiring loom out to the heater.

 

I ordered these acrylic 10mm sheets to mount the connector blocks onto. They will be bonded onto the inside face of the front door panel and the interior of the enclosure, as you'll see shortly.



Earth bonding lead fitted



Acrylic sheets bonded into place, along with the connector blocks and relay module in position. You can also see the wiring routed through the door panel from the Afterburner, these being the GPIO bundle, the 3-pin controller connectors and the temperature sensor.

 

Now finally onto the wiring. First off was the GPIO wiring from the Afterburner. There are 7 GPIO wires in total. Two inputs, two outputs, one analogue ouput, one 5V supply and one ground. I will be using 5 of these in total to supply the fan relay, fuel reset switch and the fuel warning/low LED. I have split the GND and 5V supply wires using 1-2 connector blocks to service the relay and the LED light, these being the two GPIO outputs. The fuel reset switch is an input. All the wires are braided and heatshrunk, plus I fitted ferrules (using a dedicated crimping tool) on the ends for improved conductivity, as well as a cleaner more secure fitting into the connector blocks, as opposed to just bare wire. The gauge of these wires is very small, so stripping them required a delicate touch. The un-terminated wire is for the LED, yet to be fitted.



This tool is an absolute godsend.

 

First of many hurdles to overcome was the 4 colour LED status display PCB that came with the original 24V power supply in the enclosure. It is specifically designed and dimensioned in such a way to align with the 4 holes in the door panel and mounts onto two small metal studs inside. The LED PCB that came with the new 12V PSU however is not and furthermore uses 3mm LEDs as opposed to 5mm ones. Also the colour of the LEDs and layout on the 5mm board differ from the logic for the new PSU version, so some headscratching to do.

First off I detached the 3mm LED PCB from the ribbon cable emanating from the 12V PSU and connected the 5mm LED PCB, having first checked the voltage on each pin of the connector, as I didn't want to risk blowing an LED. Nothing lit up! It took me a while to realise that the two LED PCBs were laid out in reverse, in so far as the common ground wire was at the wrong end of the connector block, where it attached to the PCB to enable the 5mm LEDs to light up. I simply de-pinned the block and reversed it around et voila!

Having got that to work, the other problem was that the LED colours did not reflect those on the 3mm board which were more logical for the statuses they are meant to represent, so I took the plunge to desolder them and fitted new ones of the correct rating and colour. Quite a tricky job and it's a loooong time since I soldered anything this small but it worked out fine. I also decided to replace the crappy 5 strand ribbon cable that came with the new PSU with a colour coded one. It features separate wires to each appropriate LED + ground, and an appropriate new PH2.0 connector at each end, then wrapped the whole thing in TESA tape, which made it much neater and easier to route, as well as more flexible. I allowed enough slack to open and close the front door panel without the LED panel wiring being under tension. Job done.

Here's the original LED panel and ribbon cable as fitted to the 24V PSU. (As mentioned, this cable was replaced and I swapped some of the LEDS out for new ones of different colours to those in this photo, with some patient soldering and a very large magnifying glass)



The new LED colours now comply with the logic of the PSU, these being from top to bottom (as in the orientation in the image above)

1. BLUE - Battery Charging
2. YELLOW - Battery Low Voltage
3. RED - 12V Battery Supply
4. GREEN - 12V PSU Supply

 

Not the easiest of things to solder accurately, but this is how the LED board looks now. You can also see the new cable I made up, each wire being colour coded to aid identification.

 

So it's been a while. I've finished all the wiring in the enclosure and have now moved onto the heater build (more on that to follow) First up was to mark out where I wanted to mount the enclosure in the garage, and on a wall where the other side of which the heater will be located. Since the plasterboard is dot and dab over a cavity wall of Thermalite and breeze blocks and since this is quite a heavy unit with all the components fitted, I opted to use CoreFix plugs. They are specifically designed for this purpose and ensure the screw does not compress the plasterboard when tightened. You could hang an elephant of the enclosure if needed, so it's not going anywhere.



Once mounted I fitted the PSU and completed the remaining wiring. The gauge of wiring to the heater is 2.5mm to prevent a voltage drop by the time it reaches the heater. All wiring that is not on the digital controller side of the circuit is rated at 17A. The current draw of the glow plug on start can reach 10A so that should be more than enough, Additionally I added two inline mini-blade fuses rated at 15A. These are the LED "glow when you blow" variety, so I can easily see which has blown (should that ever occur). The fuses are inline from the PSU to the heater supply and from the PSU to the battery. This specific battery has a 10Ah rating but can discharge 150A in 1 second, in the event of a short, so the fuse is a must to protect the PSU. The battery itself is smart charged with both under and overvoltage protection by the PSU at 13.8V and 1.5A

Here is the 12V side of the circuit. The small sensor on the wall above the enclosure is the ambient temperature sensor for the digital controller. I found someone online who makes a 3D printed mount for it with vents, to neaten things up further. The battery is currently disconnected as once I tested the system, I've have yet to route all the wiring out through the wall and so I powered the whole thing off in the meantime.



Finished making up the 5V orange LED loom for the "Fuel Low" digital output function from the controller. I had to add in a 100 ohm resistor to protect the LED from burning out.



Here's the rest of the wiring, now completed. The two black feed wires will run inside some 20mm conduit down the wall, from where they will pass through the wall to an IP67 rated junction box.





The last thing to do was to add some legends to the LEDs on the front door panel, as the ones that came printed onto it were not relevant to this setup. I also added one for the Fuel Warning LED.



With 99% of the internal work now done, I can now move onto the heater itself and then the ducting through the walls, though I am probably going to tackle the latter when the weather gets warmer.

 

The heater being located outside would not fair well to exposure to the elements, since they are primarily designed to be fitted inside campervans/caravans, so my solution (which I discovered on a YouTube video) and which has been tried and tested over 2 years, is to fit the entire heater inside a flight case. The case and fuel tank will then sit inside a steel enclosure which will sit up against the exterior wall of the garage. Ducting from the heater will be fed through the wall into the garage. Contrary to popular wisdom, I will not be ducting the air intake into the garage as I prefer to have a fresh air feed into the heater as opposed to reheating the air in the garage. I appreciate this may seem counter productive, but these heaters are so efficient, that you won't really save an appreciable amount of fuel in having to heat ambient outside air over internal ambient air. There are numerous other ways to exploit the heat by setting up heat exchangers in combination with the exhaust on the combustion circuit but I am not going to go down that route.

Whilst fresh air into the heater and expelled hot air are totally isolated from combustion air and exhaust gas, I will still be fitting a carbon monoxide detector in the garage, just to be on the safe side. In addition to the flight case, I also found someone online who produces a fantastic 3D parts kit, to make the flight case build a much more professional affair.

This is my starting point, an Apache 4800 flight case. First job was to use a heat gun and remove all the stickers on it.



Next job was to mask up one side of the case and expose those ribs on the exterior of the case that would need removing to fit the air intake grill, power connection plate and internally the 12V fan support, as they wont sit flat against the side with these ribs in place. These 3 parts are amongst some of those in the 3D kit. I masked off the whole side as when cutting plastic it obviously gets very hot and I didn't want any of the shards damaging the surface of the case.



Here are the four ribs cut and sanded back



Not too shabby with the tape removed. You won't see any of this anyway with the intake and power plug plates fitted but I can't help with the details.



After this I have to drill the mounting holes and mark out and drill three much larger holes for the intake, 12V fan and the power plug connection.

Here is the 3D kit itself. It consists of the intake plate and fan support plate, the electrical connection mounting plate, fuel pump bracket, intake coupler, combustion air intake mount and a foot bracket



This last picture shows the quick disconnect plugs, 12V cooling fan and a bag of momentary switches, one of which will become the fuel reset switch on the external junction box next to the heater.



That's all for today as it's too bloody cold to carry on and I'll leave it there for now.

 

Time to continue "butchering" the flight case, to accept the new 3d parts. First up was marking out and drilling the holes for the power inlet, 12V fan and the main air inlet.



The 3d kit has been very well thought out and though specific to this case, really neatens the job up tremendously. This internal panel features a recessed section for the 12V fan.



Coutersunk screws hold the fan in place, allowing the mounting panel to sit flush inside the case



The gaping hole on the right is for the main air inlet duct



Time to break out my rusty soldering skills. I enlisted the help of some very powerful magnifying lenses that clip onto a headband (a hangover from modelling builds in my distant youth), as the gauge and size of the wires to be soldered is quite small (aside from the 12V wires supplying the heater).

This is the 7 pin quick disconnector plug (two wires feed the 12V fan, two for the 12V heater supply and three wires to the controller. Added some heatshrink to ensure isolation between pins.



Outer air intake and fan grille fitted along with the quick disconnect plug and panel. All the bolts used throughout this build will be A4 marine grade stainless steel.



Quick disconnect plug is waterproof, though the whole flight case will be sat inside a metal enclosure, so it is not really exposed to the elements. It is just handy to be able to disconnect the power supply if I ever need to remove the flight case to service the heater in the future.



Next up I will be shortening the loom internally, as by default it is supplied as 5 miles of wiring. After that I can move on to drilling out the remaining holes for the main hot air outlet and the exhaust outlet.