H E A T E R B O X EHB-C1 - a home heating device
Some time ago (Autumn 2017) I made a blow in the case and built a
fully-equipped hybrid heater for heating purposes, especially during the winter
months. The construction would be compact and relatively easy to handle (no
hoses and bottles that mess around and compromise safety). The choice was
to modify a Lixhult cabinet from IKEA, and then I do not need to build a new
box/body where the fuel tank, battery, pumps and hoses could be stored.
The result was a portable EHB which despite its smallness still can deliver a
considerable heat output and for a long time in addition. This thing has been
used extensively during the winter 2017-18 and still works fine.
However, I had to make holes in the bottom to make the 2.5l can fit. One
should be able to fill it with new fuel from a proper fuel can as well. I do not
think I could find a more suitable sheet metal box than this one. The legs follow
the package if you are a little bit ingenious - turn them around and attach with
rivets instead. When it is a little bit shaky it adjusts when the surface is uneven
- it is always steady. The fuel consumption for two burners in operation is
approximately 35-40 ml E80N per hour and 70-80 ml for all four.
It should be mentioned that this construction unfortunately is unsuitable in
environments where there are children or animals. The risk of fire and devastation
is imminent if someone bumps into this device during operation so that it breaks
and fuel leaks out. For commercial purposes must the fuel be free from flammable
components such as gasoline and everything must be done robust and enclosed,
not in the rickety/spidery manner as the tank and the burner are arranged here.
Since the heating power with two burners mostly is enough so it is seldom
necessary to use all four. All burners use copper cuttings (instead of sand bed)
as a catalyst, which minimizes air pollution. What smells is most lamp oil - implicitly:
the more burners in use the more smell. I use two clamps (the cheap variant)
to prevent fuel from reaching the two rear burners. If I want, I can only run
a single burner with a third clamp.
The specific feature of EHB-C1 is that it uses fuel pumps intended for RC
hobby use to transport fuel towards and away the tank (the white/black container
located in the center between the burners). The tank was originally a can for
One pump for filling and one for emptying. This pump brand I use here leaks fuel
when it's not in operation, so one can not use just one pump. If that were
the case, the fuel would slowly flow backwards to the can again, so far one would
not use valves? The pumps are powered by a 12V battery from Biltema
of lithium ion model. Only mechanical electronics are required to realize this,
however the automation is based on an timer circuit that fills up the tank
with fresh fuel every two hours. The time interval the pump is on can be set
differently for different designs and conditions - regular cmos technology and
a relay make this possible. One disadvantage of the automation is that the
noise scares when the pump suddenly starts.
The black upper part of the tank is a piece of a plastic pipe (sewage) with
a round polycarbonate disc inserted. This object rests on the red plug and
causes a small pressure on top so that the tank remains airtight. However,
the actual purpose of the upper part is to act as an additional fire barrier in
case any burner would start firing flames next to the tank - a purely safety
measure. This scenario can occur if one walks past the flames that start
flattening or if one move the EHBn during operation. The fastening arms
with which the burners are stuck are layered on the Lixhults cabinet ceiling
with M6 screw, nut and plastic washers (so that the paint is not removed).
Each burner can be fold inward so that they are better protected when this
device is transported or stored during the summer. The hose between the
tank and each burner is purchased on Conrad and by the brand
Kavan (207196). Since the burner and the inlet and outlet of the
tank are 4.8 mm brake pipe of copper, transitions must be made. Such can be
arranged with a shrink tube, which by the way is highly chemical resistant.
The yellow fuel hose for remaining drawings is also purchased on Conrad
(Pichler 1436845), as well as the pumps (Modelcraft 207894).
Download circuit diagram and PCB file: EHB-C1 Revision A-1.
The burner cork or what to call them is very important and ensures that
the burner does not leak bad smell into the room when the appliance is
off. They look like English bearskin caps and originated in a bicycle handle I
found at Bauhaus (2950997A) - they are very heat resistant and
gas-tight. The top of each cap is sealed with a round aluminum piece and
black silicone adhesive. Since the E80N fuel does not like to build up pressure
in a closed container, it is not as important to ensure that the ventilation is working.
However, venting should be done in operating mode when the fuel is consumed.
Before the vented air (gasoline vapor) comes out so must it first pass a half-liter
bottle filled with activated charcoal. This plastic bottle can be seen behind the
can into the cabinet. In operate downtime can the air vent be closed with a
small red silicone plug. Can be found behind the blue drain button.
There are different ways to design the burner top so that it consists of
copper. With my two extra burners I can test other constructions and
instead of a copper pipe it also works with a filter insert of compressed
metal grain (from a fuel filter). This along with a piece of soldering braid
provides a self priming top of copper.