Turning Up The Heat

Several metres of wiring removed and this is the end result. The main plug is to the heater ECU and the smaller plug is for the fuel pump. Where necessary, I've added Loctite to all the bolt threads.



You will notice some other holes in the case, these are for the heater mounting bracket and fuel pump.The heater bracket I purchased online. It is 3mm thick stainless steel, so more than robust enough to support the heater. The cut-outs are for the combustion inlet pipe, fuel delivery pipe and the exhaust outlet. As stock the bracket was meant as a wall mounting and was way too big, so I had it cut and re-welded, so when bolted into the flight case the heater sits perfectly flat against the bottom.



Last few holes to drill out were for the main hot air duct outlet and the exhaust outlet



And finally a few more holes to fit the stabilising foot to the lid of the case, the fuel pipe inlet and some through-vent holes (more on these later). Here is the stabilising foot.






That's it for the drilling and internal electrics. Next job is to line the case with heat reflective panels, after which I can start assembling the main components into the case, firstly the fuel pump and the through-hull exhaust assembly.

 

When dealing with diesel heaters, the fuel pump is a dosage pump, so rather than run continuously, it pulses and delivers the fuel in metred amounts. Because of this, they are very finicky about the size and bore of the fuel lines and rubber connection pipes you use. Both have to be rigid enough to prevent trapping any bubbles that form in the fuel (due to cavitation from the pump pulses). Hence the main fuel line is typically made of a rigid plastic and the rubber connections are of a similar sturdy nature. These Eberspacher reinforced ones are 9mm OD and 3.5mm ID. The internal diameter is quite critical, else it will throw up error codes on the controller if you use normal bore fuel pipe, since the pump just isn't man enough to move large volumes of fuel when running at higher rates (Hz), typically when you want to crank up the heat.

Diesel heaters control heat output via a temperature sensor that adjusts the pump rate (Hz) and fan speed accordingly. This correlation needs to be tuned to minimize the amount of CO output down to zero or a negligible level. Most come factory set, but if necessary I can adjust this with a CO meter inside the garage, once the whole thing is up and running.

 

These are the heat outlet ducts I had made up by a local fabrication company. Outlet hot air temperatures can reach up to 110C, so you cannot use plastic ones. I'm having some custom silicone gaskets made up to sandwich between each pair and they will be painted in a heat resistant black paint shortly along with a heat resistant foil liner inside the duct tubes. The shorter of the four is for inside the flight case, joined to the heater by a flexible silicone ducting.



These are the two through-hull exhaust fittings that have an inner metal tube that is isolated from the outer housing to prevent heat transfer. Usually fitted to boats, I have had these modified by having a short pipe welded onto the exterior. This allows me to connect additional exhaust tubing to route the exhaust out the flight case and then out of the steel enclosure to a silencer and then finally to atmosphere, hence the need for two.

 

Finished adding heat shield panels to the "hot end" of the flight case. Fuel pump installed and fitted the first of the modified through-hull fittings. A lot of head scratching to come up with a suitable design for the fuel lines on the pressure side of the pump, that would enable me to mount the pump in the correct orientation and closer to the heater, whilst routeing the line through 2 x 90 degrees bends, something you can't achieve with the normal rigid fuel pipe, used with diesel heaters. I resolved it by using 1.5mm bore ID rigid rubber pipe and 4mm brass barb connectors. These are compliant with the limitations of a dosage pump and the arrangement should not cause any issues with trapped bubbles that arise normally through cavitation.

Heat shielding fitted





Fuel pump and exhaust through-hull fitting installed





I added four 8mm ventilation "through-holes", so that air drawn in by the fan on the opposite side of the case, to feed the combustion intake, can also exit the case, along with any warmer air surrounding the combustion exhaust outlet. Also in the event of a fuel leak, these holes will allow fluid to drain out of the case and not pool inside.

 

Just waiting on some silicone custom laser cut gaskets for the heater outlet ducts (silicone rubber is ideal at withstanding typical outlet temperatutes) and the ducts themselves to come back from the painters and I can get cracking to complete the heater flight case build. After that, I'm probably going to wait until the weather warms up a bit to install all the through wall ducting and electrical ducting from the control enclosure inside the garage.

 

Air duct adaptor plates back from powder coating.



Initial mock-up of the new 15 litre tank completed. I have yet to add the inline fuel filter. Tank features a vented cap, to avoid a vacuum.



90 degree fuel elbow makes life a lot easier than trying to contort the semi-rigid fuel line around a tight bend



Measured and marked out some fuel levels, then printed out the labels so I can quickly check the remaining quantity of diesel in the tank. The Afterburner digital controller has the ability to monitor the fuel usage, so you can set it to warn you when you reach a certain quantity remaining and then shut the heater down when you reach your minimum set quantity. This avoids you running the fuel tank dry and having to re-prime the fuel system and potentially damaging your pump. The GPIO function of the Afterburner also allowed me to fit a "FUEL LOW" warning LED in the garage on the control panel door (see earlier posts for pictures), so I can visually see it needs topping up without me having to venture outside.



I installed a top fitting pipe pick up (cut to length about 15mm from the bottom of the tank, to avoid sucking up any water or debris in the fuel)



Finished up installing the conduit in the garage. I now have to drill a 20mm hole through the cavity wall, to route more conduit and then the cables themselves to the external junction box which will mount on the other side. From there a cable will connect to the junction box with a quick disconnect plug fitted at the other end. This will pass through the metal box enclosure and to the QD port on the flight case containing the heater. In this way I can quickly disconnect power to the heater and remove the flight case from the metal box enclosure, for future servicing or repairs.

 

Spent a few hours yesterday afternoon, soldering and insulating the seven wires that go from the external junction box to the heater and terminating in the QR connector plug. Quite fiddly to solder all seven to the pins but with this out the way, that's about 95% of the wring complete.



Quick release 7 pin waterproof connector

 

Back from a 3 week holiday in NZ. Finished the external junction box. The momentary switch means I can reset the fuel usage to zero whenever I refill the tank and saves me doing so on the Afterburner.

 

I am a fussy barsteward, I must admit.

 

Spent yesterday afternoon drilling through the wall to install the external junction box. Decided to bite the bullet and bought a pretty meaty SDS drill. It's a heavy unit and doubtless will be more than man enough when it comes to drilling the much larger hole out for the ducting pipe with a diamond tipped core drill bit. That is going to have to wait until the warmer weather, as once drilled I want to have everythig in place, so as I minimise the time spent with a gaping hole in the building. If it ever stops raining today, I plan to seal in the 20mm conduit pipe that passes through the wall, then seal it into the back of the junction box, before I run the wires through the wall. The periphery of the box will also be sealed to the wall to prevent any moisture getting behind it. I will post up some pics once done. First job today is to repair the very small blow out on the render outside, where the drill broke through, but that is a quick fix.

 

Here are a few pictures of the completion of the flight case build that I omitted to post up earlier.

Laser cut silicone gaskets will fit between the outlet manifolds and the case to prevent heat transfer and seal the plates correctly, to minimise any air leaks.



To further mitigate heat issues, I lined the bores of the outlet plates with heat reflective foil.



Finally, I was able to fit the heater into the case. The flexible ducting is thermally resistant and allows for any difference in position/height between the heater and the outlet. Stainless steel Mikalor clips ensure a tight seal.



At the inlet end, this is the 3d printed coupler that has an offset, allowing you to fine tune the alignment of the heater body.



Here is a view of the heater now bolted into place. As mentioned before the mounting bracket is 3mm thick stainless steel, so this together with the inlet and outlet fixings, ensure the whole unit is rigidly secured inside the case. You can also see the completed fuel connection into the heater.



Now awaiting the exhaust and inlet plumbing

 

Exhaust paste will ensure a gas tight seal when fitting the pipe inside the case. The glass fibre matting/sleeve, was cut to length before being slid over the exhaust pipe (which you cannot see but is underneath). This will reduce any heat emitted inside the case, the fan will help extract it.



Now secured and fitted in place. Again stainless steel clips used throughout. These ones from Mikalor have a smooth internal band, so they don't chew into the pipe when tightened and apply a uniform pressure.



Next job was to bond the last of the 3d printed kit components into place. This is the carrier for the combustion air inlet filter.



Finally, the air inlet filter itself. As for the exhaust the same Mikalor clips were fitted to ensure a good seal around the joints, even though these are not as critical.

 

So with the flight case element of the build complete, here are some images of it in it's entireity. Pretty pleased with how it turned out.













Here you can see the fuel line where it exits the case. This will be connected via an inline filter to the fuel tank at a later stage.



This final image shows the heater and the angular orientation of the pump (which is critical) when the whole case will be standing in the normal vertical position. There were other options for mounting the pump into the lid of the case but I went for this set up, as it keeps the pump as far away from the exhaust as possible, while still keeping it out of the elements inside. Last thing I did was to add in a few cable clamps and zip ties, to neaten the whole thing up. You can also see the four vent holes at the bottom of the case. As mentioned before these serve as an outlet for the hot air and any cooling air drawn in from the fan and as an exit point for any fuel to leak out (should that occur)

 

On the software side, one of the advantages of the Afterburner digital controller is being able to control the heater from anywhere, not just over bluetooth or my local wifi connection at home. Using an MQTT broker I created a control panel within a dedicated app on my phone, so that I can access the heater from anywhere with an internet connection. For example, if I want to turn on the heating in the garage on my way home from work I can. This little unit is worth it's weight in gold. This screenshot was me testing the system connections/wiring with the heater in standby mode.

 

My wife labelled it as my mad contraption. I prefer to think of it as something Q might have cooked up.

 

Bought some Toupret Masonry Repair filler for the small blow out in the render and I have to say it's amazing stuff, sets rock hard in 24 hours and waited a further 48 hours to paint it as per the instructions. Second coat of paint went on the wall today (almost impossible to see where I made the repair now, which is a good thing). Tomorrow I can fit the junction box in place and seal the backbox to the wall. I should then be able to feed the wiring through from the control box in the garage to the connector blocks. Once that's done, all that's left in terms of the electrics, is to connect up the 7pin QD lead I made up earlier, but that will have to wait until the concrete base and enclosure are completed. The duct pipe position in the wall is predicated by the position of the enclosure outside, so that will be the last major job on the list. Photos to follow.

 

Finished wiring up the internal wiring from the control box in the garage to the exterior junction box, which is now mounted in place. That just leaves the exterior wiring from the junction box to the heater to be done and the duct hole through the wall and I'll be on the home straight. Concrete base and the metal enclosure for the flight case and fuel tank are next on the list.