Category Archives: Technical

Tim’s Tech Talk

My Mains Monitor 2.0


Avid readers will recall a previous post My Mains Monitor, which described a simple circuit designed and built to alert us to mains power failures.

Every so often, the mains power circuit breaker in the van trips for no apparent reason. Sometimes, it even trips for a good reason (air-conditioner + hair dryer + microwave oven + etc. >15 amps).  Keeping an absorption fridge at temperature in very hot weather can be challenging. We went to bed one night expecting the relative cool overnight to help get the fridge temp down to something reasonable but woke the next morning to find that the van and hence the fridge had lost mains power sometime during the night.

You may also recall a number of limitations of that design:

  1. If you leave the monitor turned on when travelling, it flashes and buzzes continuously. If you turn it off but forget to turn it on when you are next connect to mains power, it is a waste of space.
  2. Depending on the internals of the AC-DC adapter you use, there may be a delay before loss of mains is indicated by the monitor (mine takes about 30 seconds). 
  3. When the input signal is not present, LED1 may be dimly lit. 

Needless to say, My Mains Monitor 2.0 solves all of these problems.

  1. It alerts us to the loss of mains rather than the absence of mains. Whilst the lights indicate the presence or absence of mains, the audible alarm is triggered when previously present mains power becomes absent and can be muted by pushing a button. The mute is then disabled the next time that mains is present so that the next loss of mains will again trigger the alarm.
  2. The delay before loss of mains is indicated by the monitor is reduced to 2-3 seconds.
  3. There are no erroneous glimmering LEDs.

Continue reading My Mains Monitor 2.0

My Mains Monitor


Every so often, the mains power circuit breaker in the van trips for no apparent reason. Sometimes, it even trips for a good reason (air-conditioner + hair dryer + microwave oven + etc. >15 amps).  Keeping an absorption fridge at temperature in very hot weather can be challenging. We went to bed one night expecting the relative cool overnight to help get the fridge temp down to something reasonable but woke the next morning to find that the van and hence the fridge had lost mains power sometime during the night.


I built a simple mains power monitor to alert us to mains power failures. It uses old technology: lights and buzzer. Maybe one day its successor will use Twitter (or its successor) to send us the bad news.

Green is Good
“Green is Good!”

In summary, it:

  1. is powered from the van battery (even when van is connected to mains);
  2. lights a green LED to show that both battery power and mains power are present;
  3. takes its “mains on/off” signal from an off-the-shelf AC-DC power adaptor;
  4. lights a red, flashing LED and sounds a buzzer when mains power is not present.

It has not yet experience a real life mains failure but it is tested regularly: every time we decamp I forget to turn it off before I remove the mains power lead and the monitor always reminds me!


For those interested, here is the circuit I used.



In essence, it is just two transistor switches in series, each driving an LED, and with the first transistor inverting the input signal for the second transistor.

  • The monitor is powered from the van’s 12V system and therefore, importantly, from the van’s 12V battery when mains is not connected. I use a short cable between J2 and one of the van’s “cigarette lighter” sockets.
  • An 240V AC to 12V DC adaptor (not shown in schematic above) is plugged into J1. It provides safety isolation of the monitor from the high voltage AC mains supply as well as a conveniently low voltage DC signal that indicates the presence or absence of mains power (note 2).
  • The voltage divider R1 & R2 reduces the input signal voltage from 12V to approximately 2V, which saturates T1 without cooking it.
  • R3 & R6 are current-limiting resistors for LED1 & LED2, respectively.
  • Jumper JP1 is normally shunted; removing the shunt mutes the buzzer.
  • Both transistors operate as switches rather than amplifiers, i.e. they are either fully off or fully on (note 4).
  • When input signal is present:
    • voltage applied to base of T1 is significantly more than 0.7V above its emitter;
    • T1 turns fully on and current flows through LED1;
    • base of T2 is pulled down to ground by T1;
    • with its base voltage less than 0.7V, T2 is fully off and no current flows through LED2 or B1.
  • When input signal is not present:
    • base voltage of T1 is pulled down by R2 to less than 0.7V above its emitter;
    • so, T1 is fully off and no current flows through LED1 (note 3);
    • T1 is not pulling down the base of T2;
    • so, R5 pulls the base of T2 to significantly more than 0.7V above its emitter, turning  it fully on;
    • With T2 on, current flows through LED2 and B1.
  1. If you leave the monitor turned on when travelling, it flashes and buzzes continuously. If you turn it off but forget to turn it on when you are next connect to mains power, it is a waste of space. A future redesign could indicate the loss of mains rather than the absence of mains (i.e. trigger on a falling edge rather than a low level).
  2. Depending on the internals of the AC-DC adapter you use, there may be a delay before loss of mains is indicated by the monitor (mine takes about 30 seconds). The monitor draws very little current from the adaptor so the smoothing capacitor in the adaptor on the DC side takes that time to discharge to a voltage low enough to trigger the monitor. This is not necessarily a bad thing: it allows deliberate short term disconnection without setting off the alarm.
  3. When the input signal is not present, LED1 may be dimly lit. T1 is off, but a small amount of current flows from the positive supply (VCC) through LED1, R3, R4 and T2’s base-emitter junction to ground.  This could be avoided by a more complex circuit, probably using two more transistors. In practice, with LED2 flashing red and B1 buzzing, a faint, green glimmer in LED1 goes unnoticed.
  4. For a discussion of transistors operating as switches, I suggest


  • J1 is a socket chosen to suit your AC-DC adaptor, in my case J1 is a 2.1mm socket
  • J2 is a socket chosen to suit the cable that you use to connect to 12V battery power: I used a cable with a cigarette lighter plug on one end and a 2.1mm plug on the other so my J2 is also a 2.1mm socket
  • my B1 is a 3-30V DC buzzer (Jaycar part AB3458); any noisemaker that works from 12VDC and does not draw more current than the maximum collector current of T2 should do it
  • for LED1, I used a green, 5mm LED (Jaycar part ZD0150)
  • for LED2, I used a red, flashing, 5mm LED (Jaycar part ZD1785)
  • for each of T1 & T2, I used a BC237 because I had them on hand, but any  NPN transistor with sufficient collector current to drive an LED plus the chosen  buzzer should work (e.g. 2N2222)
  • the value of R3 should be chosen to suit your choice of LED1 when used with a 12V supply
  • the value of R6 should be chosen to suit your choice of LED2 when used with a 12V supply
  • the values of R1 & R2 should be chosen to reduce the input signal voltage to a voltage that will saturate T1 without cooking it. I used a 240V AC to 12V DC power adaptor to generate the input signal because I had one on hand, not because it was 12V. I then choose R1=10K and R2=47K, which reduces that 12V DC by a factor of 10/57 (approximately 1/6), resulting in approximately 2V begin applied to the base of T1 when mains is present (and 0V when it is not)
  • the other resistor values (R4 & R5) are not as critical: I settled on them after experimenting with values that minimised the issue noted above whereby LED1 glimmers dimly when LED2 is on; different transistors may require different resistor values for R4 & R5 to minimise this effect;
  • for the enclosure I used an ABS plastic box (Jaycar part HB6120)
  • the board was cut from a piece of Pre-Punched Experimenter Board (such as Jaycar part HP9550).


If you read this far, you probably know how to solder all of that onto a board and put it into a box. Here is a picture of the insides of mine before it was screwed together.

  • The white, cylindrical component is the buzzer. At 25mm in diameter it is relatively large; fitting it into the box in a way that avoided the board’s mounting screws was a bit of a squeeze.
  • The LEDs are glued using epoxy-resin into holes drilled in the lid of the box.
  • Pairs of breakaway header pins on the board and wire pairs with female sockets on one end are used to connect the LEDs and sockets to the board. (I used female-female breadboard wires cut in half.)
  • The ink doodling on the board itself should be ignored!

Next Episode

Coming up (hopefully), is a Three-Way Fridge Monitor …


Portable Potable Pumping

We have come to enjoy so-called “free camping” in National Parks and similar locations. Whilst often not free of fees, they are are certainly free of mains electricity and mains water to the van. Some have one tap with drinking water but many do not. Our van’s water tanks are good for 5 days or so if we don’t shower. Beyond that, we have three (3) 20 litre jerry cans with which we drive to the nearest town or location with a publicly accessible drinking water tap where we fill them, then drive back and empty them into the van’s tanks.

IMG_4812We use a hose  to fill the jerry cans without removing them from the back of the tug, but emptying them into the van’s tanks is another matter. Whilst 20kg is an acceptable weight for one person to lift, holding it on the angle that gets the water into the tanks without spilling it or dropping the jerry can or pulling off the spout is tricky. Being mindful of this and our ageing backs, a “no lift” solutions is needed.

They key objective was to transfer the water from the jerry cans into the van tanks without removing the jerry cans from the tug. A  12 volt, self-priming pump that tolerated running dry and was not of the submersible variety for less than say $50 was first sought. We tried numerous camping stores, aquarium suppliers and hardware stores but without success. Pumps on offer were not certified for use with drinking water, or were submersible, or both. (A submersible pump is not suitable because you can’t get it down the jerry can’s neck!)

IMG_4819_FotorWe ended up buying a pressure pump like those used in caravans, but with the lowest rating available: 4 litres per minute. This size of pressure pump is used in camper trailers that have a small tank and  one tap, and sells for approximately $100. Whilst this application does not need a pressure-switched pump, that turned out to be the most suitable, albeit expensive, type available.

IMG_4821The pump’s inlet and outlet are barb fittings to suit 10mm hose. We purchased a 6 metre length of clear, beverage-grade plastic hose from the pump supplier for a couple of dollars per metre. You can buy this type of hose at camping or hardware stores but be sure that it is beverage-grade. Cut into one 2 metre length and one of 4 metres, we have one short hose from the jerry can to the pump inlet and the other from the pump outlet to the tank fillers. In the interests of hygiene, we first sterilised the hose with Milton and, when not in use, store it in a zipped plastic carry bag.

IMG_4823The pump’s electrical connectors out-of-the-box are two insulated wires with stripped, bare ends. I crimped four (4) pairs of bullet connectors like so:

  • one pair to the bare leads on the pump,
  • one pair to the bare cable ends of a 12V “cigarette lighter” plug (e.g. Jaycar PP1995); and
  • one pair to each end of a length of insulated twin-core cable.

Our current tug (Ford Territory SZ, 7 seater) has a 12V outlet in the boot compartment so the overall cable did not need to be very long. This arrangement is more complex than necessary and was based on what I had on hand at the time. Simpler solutions include:

  • a cigarette lighter plug with a long tail (e.g. Jaycar PP1998) joined with crimped barrel connectors or screw terminals to the pump wires;  and
  • a cigarette lighter plug with a short tail (e.g. Jaycar PP1995) joined to the pump wires together with an off-the-shelf 12 volt extension lead (e.g. Jaycar PP1992).

2015-04-28 20.57.08As expected from the 4 litre/minute specification, one 20 litre jerry can is emptied in about 5 minutes. To get out the last couple of litres, we found it necessary to tilt the jerry can on a 45 degree angle and manipulate the hose to the bottom corner. There is no manual lifting, and the manual tilting occurs when the jerry can is near empty.

The pump and cables are stored in a sealed plastic box. The hoses are stored in a soft plastic  carry bag with zip closures (which originally contained an awning shade).

IMG_4826_Fotor IMG_4827

Hints and Tips


Note that:

  • flushing the pump and hose by running some water through them before inserting the outlet hose into the tank filler seems like a good idea;
  • the outside of the hoses will come in contact with the water in both the jerry cans and the van tanks and so giving them a clean before each use also makes sense.
  • residual water will be left in the hose and pumps regardless of how hard you shake them, so if the most recent use was not recent, consider sterilising them before use.


A pump for this purpose should:

  • be self-priming (since it will not be gravity fed from the jerry can);
  • be able to run dry for a short time without damaging itself;
  • have a maximum current demand that is less  the 12 volt accessory sockets in your vehicle can supply;
  • be certified for use with drinking water.

Note that these pumps:

  • are not able to run dry indefinitely, so don’t leave it running unattended whilst it  tries to pump out of an empty jerry can;
  • are not designed to run continuously, so give the pump a rest every so often (check the specifications for “duty cycle”).

Water Connections

Naturally, your hoses should be sized and adapted to suit your pump’s inlet and outlet. Our pump has 10mm barbed connectors over which we push 10mm tubing. Hose clamps could be used but we have not found them necessary (the pump is only ever run with someone present).

Some larger pumps have a male threaded inlet and/or outlet, which would support a more robust, though complex, fitting. If your pump has a threaded inlet or outlet, it will most likely be of the BSP thread standard for which a variety of adapters are readily available in hardware and plumbing supply stores.

I suggest taking your pump to a self-serve hardware store and playing with their hoses and fittings to invent the simplest, cheapest and most effective arrangement. Use only BSP fittings for a BSP thread or you will suffer leaks and/or use a lot of teflon tape.  BSP connections should not need teflon tape (one or both sides of a join has a tapering diameter, which gives a water-tight joint). Alternatively, take the pump to a plumbing supply store, tell them your application and they should easily do the same. If you are buying the pump from a plumbing supplier and describe your application, they should be able to supply all the “wet” parts required for an optimal end-to-end solution.

Electrical Connections

If using crimped spade or bullet connectors, remember that a connector supplying +12V should be female to avoid shorts and blown fuses (or worse) when it accidentally touches a metal part of the vehicle. (Hence the connector receiving +12 volts is male.) I use opposite genders for the earth (a.k.a. ground or 0 volts)  connectors. This prevents accidentally connecting one cable to the other with polarities reversed and hence reverse polarity being applied to the pump motor, though it does allow the 0V supply male to be inserted into the +12V supply female, which is also not good.

If using connectors (e.g. screw terminals) that leave any live +12V points exposed, wrap them with electrical tape.

Cembre-Disconnect-Terminals-Halogen-Free-Cable-ConnectorsIf using insulated crimp connectors for the first time, it helps to know that the colour of the insulation on this type of connector corresponds to the diameter of the copper in the wire to be crimped (red is smaller than blue is smaller than yellow) rather than to the size of the spade, bullet, etc. The spades and bullets themselves are the same size, for example, a red male bullet fits a blue female bullet.

Soldering of these electrical connections is not recommended unless care is also given to the “mechanical connection”. When the ends of two flexible wires are soldered together, the two points at which the flexible copper meets the less flexible solder are subject to extra stress when the wires flex and will eventually break.

wholesales-car-font-b-cigarette-b-font-font-b-lighter-b-font-plug-with-fuse-andSome cigarette lighter plugs have an internal fuse; this can cause confusion if it blows and you don’t know it is there.

If you are not confident in choosing appropriate connectors and cables to suit the current draw of your pump, and/or in making reliable connections, you should use off-the-shelf components or engage an auto-electrician.

Water Containers

Given that the jerry cans no longer leave the tug’s boot, at least not when full, they do not need to be limited to a gross weight that can be manually lifted. You might consider using fewer but larger and more efficiently sized and shaped containers. Your choice!

Water Sources

For  accessible drinking water taps in country towns we have found the following locations fruitful:

  • around the back of community halls;
  • at fish cleaning stations next to boat ramps;
  • RV Friendly Towns – the conditions of “RV Friendly Town” certification by CMCA mandate access to of potable water and encourage the existence of an Information Centre (e.g. to tell you where that water is).

We always remove any existing hose from the tap, run some water to flush the tap, and connect our own hose to fill the jerry cans (being sure, of course, to replace the pre-existing hose before leaving!).

Estimating the length of the two hoses can be fraught. Consider where the pump will be located when operating to help decide the length of the inlet hose; don’t forget the metre or so needed to get to the bottom of the jerry can. The outlet hose length depends on how close to the tank fillers you expect to be able to get the vehicle; think about how to route and secure it so that it doesn’t fall out of the tank filler and doesn’t trail in the dirt.


A couple of weeks after buying and setting up the small pump described above, we had to replace the larger (11 litres/minute) pump installed in the van. Whilst the old pump worked OK in the forward direction, it developed a slight flow in the reverse direction. Because the van is plumbed in a way that relies solely on the pump to prevent mains water entering  the tanks, this resulted in the tanks overflowing when mains water was used.

As a result, we now have a spare 11 litres/minute pump that would be quite suitable, and indeed quite fast, for transferring water from the  jerry cans into the tanks!

Temperature Trouble, Galvanic Grief and Hydrological Horror

After arriving at Trial Bay Gaol Campground (in Arakoon NP near South West Rocks on the mid-north coast of NSW), we didn’t use the car for a couple of days, there being plenty to do on foot and a fair bit of rain.  On starting the vehicle for the first time after that, it exhibited a number of concerning symptoms.

  1. check engine indicators alight and beeping;
  2. engine temperature gauge beyond the red zone;
  3. a message warning us that cruise control was not available.

check-engine-lightThe engine was patently not warm let alone hot, so “instrumentation error” was top of mind, but that was also the first response to the Apollo 13 oxygen tank explosion, so I called the NRMA. Tom arrived in seemingly less time than the NRMA call centre took to fail to find the vehicle on either of its two(!) computer systems,  telephone the RACV and finally agree that yes, the vehicle did indeed have roadside cover. Tom confirmed with his OBD tool that the engine management system thought the temperature was at extreme levels even though it was not. We located a black-box attached to a radiator pipe and awarded it the “most likely to be the temperature gauge” prize. Its electrical connectors looked clean but I gave them a bit of a rub anyway; that did not clear the fault. Tom checked all the fluids and pronounced the car OK to drive with a recommendation that it be checked by a mechanic soon in case a genuine fault was to occur and go unnoticed. My tentative diagnosis was confirmed.

A couple of hours late, we headed out in the car for our planned day trip. The windscreen was dusty so I gave it a squirt – water from the passenger-side jet went everywhere except onto the windscreen. (“Houston, we’ve had another problem.”) Being extra cautious as a result of the earlier events, we returned to camp to investigate. A few days earlier the rear window washer had failed due to a push-fit pipe join coming adrift, so something similar was assumed. Chewed Water PipeOn inspection, this fault was obviously different: there was hole in one side of the rubber pipe that carried water from the pump to the passenger side sprayer. Looking closely at the hole (with the aid of cameras, magnifying glasses, etc. given the official heritage status of our eyesight) we could see what the folk on CSI call striation marks: parallel grooves, in this case made almost certainly by teeth. Did some animal hop up there while the bonnet was raised in the universal “here I am” signal to the NRMA guy? I asked our neighbours on that side whether they had seen any wildlife displaying a rubber-fetish in our engine bay, but no, they had not. Repaired Water PipeAfter sealing the hole in the pipe with Recovery Tape(*), we rescheduled our day trip to the next day and test-drove the car to the nearest pub. (*) A particular brand of self-amalgamating tape that is even more expensive than generic self-amalgamating tape but if applied according to the directions will not only repair leaks in a radiator or holes in a crank case but will also contain nuclear accidents and ebola outbreaks) Wiring Harness with Vegetables

Having a spare 5 minutes before we set off the next morning on the rescheduled day trip, I had a look around under the bonnet, this time sensibly with the aid of a torch to (refer to earlier comments about eyesight). This revealed some interesting new facts …

  • the black, outer insulation was stripped from a section of wiring harness;
  • chunks of coloured insulation were missing from some of the inner wires;
  • a 5cm length of one inner wire was entirely missing (and later found lower down in the engine compartment) ;
  • a collection of blades of grass and shells from some type of nut;

Undigested InsulationLastly, there were droppings of a size and shape that I recognised from previous crusades against the evil empire that the Romans named ratus ratus. Ever the clinician, Helen spotted a dropping in which an undigested piece of black insulation had been passed. After noting that the insulation on the severed wire was the same aqua colour as that on one of the wires to what Tom and I had previously decided was the temperature sensor, my trusty multi-meter confirmed that they were indeed one and the same circuit.   So, here was not only the cause of the engine temperature “instrumentation error” but a root cause shared with the windscreen washer fault. Whether it is also the cause of the lack of cruise control or air conditioning (did I mention that?) is yet to be determined. We set off for the trip later than intended. The lighthouse at Smoky Cape was nice but the snorkelling adventure was a write-off due to the recent rains pushing copious mud out of the rivers and into the ocean.

The Missing Wire
The Missing Wire

I considered repairing the wiring loom on the spot, but to do so would require removing things I didn’t recognise and may struggle to replace, and we were in what is  best described as a “one tow truck town”. Given that the vehicle is drivable, we will seek expert assistance at our next stop, Coffs Harbour.  We look forward to driving there tomorrow, towing a 2 tonne caravan with the temperature gauge beyond the red zone, the check engine warning lights aglow, no cruise control and no air-conditioning. But it is only two hours away, so could be much worse. If the Ford dealer at Coffs can’t accommodate us this week, I hope to find an auto electrician that will. Otherwise, I will “DIY” it, comfortable that if it goes badly Coffs is large enough to have multiple tow trucks, mechanics and auto electricians, even if that means being forced to stay longer than we had intended in the city that claims to have the most liveable climate in Australia.

Not knowing where the vehicle’s comprehensive insurance policy was comprehensive enough to cover rodent damage but mindful that insurance companies don’t like retrospective claims, I made a coffee, took a deep breath, and made the call. After the advertised human answered the call within the advertised time and then promptly put me on hold, I spent 15 minutes learning about how much they cared about my call,  how they were experiencing an unusually high call volume and how lucky I was to be with them. Eventually “Level 1” answered, reminded me of the policy excess and explained the process of getting the vehicle to their assessment centre etc. etc. After convincing said agent that the vehicle was not in Victoria, that Coffs Harbour was not in Victoria, and that no, the assessment centres in Sydney were not really appropriate, I spent a further 10 minutes on hold,  presumably while a supervisor and/or atlas were consulted. The agent was then pleased to advise me that, there being no assessment centres near the suburb(?) of Coffs Harbour, the assessor would come to the vehicle rather than the vehicle to the assessor. Deciding that even the most liveable climate in Australia would wear thin by the time that happened, I got my reference number and bailed out, making a mental note to locate our policy document and determine whether rodent damage is excluded as force majeure (a term invented by Roman lawyers meaning “Act of God” because saving one word was worthwhile in Roman times, there being so many gods and them being so active). evidence bag Samples of wire, fur and poo have been saved in a clear, zip-lock plastic bag for the CSI team.


The next morning there was a knock on our door. Aforementioned neighbours had packed up and were setting off for their next adventure when their vehicle exhibited a number of warning indicators: no cruise control, no traction control, etc. but fortunately also still drivable. Armed with my information of the previous day, they were able to diagnose the cause somewhat more quickly than I did. Coincidentally, we met again two days later at a caravan park in Coffs, when they had just collected their car from repair and I had just dropped off ours. Suffice to say that the rat contributed a joint total of about $1,000 to the local automotive repair industry …

Solar Setup

We ordered the van with the maximum number of solar panels that Jayco could fit on the roof, namely three (3) panels of 120 kilowatts each. Unfortunately the other things on the roof (e.g. antenna, air conditioner) mean that there are fewer panels possible than you might expect. Also fitted was a 100 amp-hour deep cycle battery, a Topray TPS-555 1230 Solar Change Regulator and a battery monitor (as part of the SETEC Drifter).

Projecta 600W InverterWe added a Projecta 600W inverter. This is a “modified sine wave” (i.e. not a pure sine wave) inverter with which we run limited mains powered appliances when they are needed off the grid, specifically electric blankets and a small washing machine. We do not attempt to run anything with more current draw than them from the inverter, and certainly not electronic equipment.

In the summer and autumn, the battery recharged by 11am on most days and never fell under voltage. However in winter with limited sunlight hours, the battery did not fully recharge every day, and with cold nights off the grid using electric blankets, the battery did sometimes drop under voltage overnight.

Topray TPS-555 1230Aside from the obvious inconvenience of not having lights etc. until the sun had done its work, driving the battery under voltage uncovered an undesirable feature of the TPS-555 1230 solar charge regulator. When the battery voltage falls below a set threshold, an alarm sounds. Initially we thought there was a cricket loose in the van, such was the chirp…chirp…chirp sound of this alarm. Once the cause was identified we then discovered that this alarm could only be reset by either returning the battery to sufficient voltage, requiring sunlight, or by disconnecting the battery altogether from the controller, requiring a screw driver. There was no other way to silence the cricket that was keeping us awake.

We have addressed these various limitations with some modifications:

  • an LPG heater to avoid use of the inverter on cold nights (see blog post),
  • 1418895786_upload_products_263_300-249_2a replacement solar charge controller (the Victron BlueSolar MPPT 100/30) that includes an alarm reset function amongst many other features and has Maximum Power Point Tracking (MPPT) to squeeze some additional charge from the available sunlight,
  • provision made for a second battery when rewiring for the replacement solar charge controller, which we will add if battery capacity rather than sunlight hours proves to be a limitation (and if not, we will avoid its weight and space).

We gave these modifications, along with the LPG heater and the waste water replumbing, a shake down on a short trip to the Grampians. For updates on the effectiveness of the solar system, watch this space …

Trumatic E 2400 LPG Heater Installation

Revision History

This post has been updated based on experience from 2014 to 2017 – see “Hindsight” section below.


Soon after starting our caravaning adventures, we got a taste for free or cheap camp sites, not so much for the economics but for the relative peace and beauty of many of the sites around the country as compared to caravan parks. This meant learning to stretch the limited resources (water, toilet cassette, solar/battery amp hours, LPG tanks) in order to stretch the time spent off grid. A mid-winter trip to central Australia with four people in the van and annex emphasised the need for heating at night (despite daily temperatures in the high 20’s). When mains power was available, the reverse-cycle aircon in the van and an electric fan heater in the annex did the job. Off the grid, electric blankets fed from an inverter helped, but left the van battery under-voltage (and once flattened the vehicle battery when I had neglected to disconnect it). LPG is the available energy resource that travels and stores well. (Perhaps hydrogen fuel cells will overtake it soon?) With twin 9kg bottles on the van and refills available at van parks and country hardware stores, it seems that gas should be the last thing to run out. So an LPG heating solution made sense.


Trumatic E 2400 We chose  the Truma Trumatic E 2400 LPG heater. It is designed for RVs by a company with a track record in diesel fired heaters for RVs. Operating on the heat exchange principle, it exhausts the combusted gases to the outside rather than into the van. Internal air is drawn in, passed through the heat exchanger and recirculated back into the van. Various Air FlowsThis heater has four openings:

  1. LPG;
  2. inlet for air to be heated;
  3. outlet for heated air;
  4. combined exhaust gas outlet and external air (for combustion) inlet.
Combined External Outlet & Inlet
Cowl combines external exhaust outlet & air inlet

The last one combines two things into one using a coaxial arrangement, i.e. one is inside the other. This means there is only one external hole and one hose between it and the heater. Aside from reducing the number of holes and hoses, with this arrangement:

  1. the outgoing exhaust gas  pre-heats the incoming air, improving the efficiency of combustion; and
  2. the hotter hose is shielded from combustibles, fingers, etc. by the cooler hose.

This heater can be purchased in Australia for between $1,500 and $2,000. The best deal I have seen offered that includes installation was $1,650 for the heater and $600 for installation (mid 2014.) Tip: If buying online, beware of units that are not accompanied by Australian installation and certification documentation. The gas connection must be done by a gas plumber licenced for mobile installations. The remainder of the installation can be DIY but be aware that you need to be willing and able to:

  • cut and later seal a 70mm diameter hole in your van’s wall,
  • cut at least one 80mm diameter hole in a cupboard wall,
  • do the 12 volt DC wiring and connection,
  • securely mount a 5kg object in a vehicle that moves about.

Having done it ourselves, my opinion is that $600 is a very fair price for installation, especially given that the gas plumbing is likely to cost about half of that. Of course, the $600 offer referred to above was conditional on purchase of the heater from the same supplier: don’t expect to buy it for the best online price and then pay only $600 for someone else to install it!


Where in the van to install this heater was not obvious. Aside from the space, there are a number of safety and technical limitations. For example, the exhaust cannot be under a window or into an awning, you need a practical pathway for the gas plumbing, there are minimum and maximum lengths for the exhaust and the hot air hoses and there is a minimum separation between the hot air outlet and the cold air inlet. According to a local supplier and installer, under the bed is a popular location, with the exhaust hose going through the bottom bedside cupboard on the driver’s side. However our van has a side-opening boot under the head of the bed and below the side cupboards so (short of running the exhaust hose through the boot) that was not an option. We considered locating the heater under one of the bench seats, but the maximum distance to the outside for the exhaust hose (1 metre) was a problem as it would have had to wind around the HWS and/or the wheel wells.

Chosen Location Showing Hole for Hot Air Outlet
Chosen Location Showing Hole for Hot Air Outlet

Fortunately, on the driver’s side of our van, between the fridge and the back of one of the bench seats is a stack of three very narrow, very tall cupboards. Of all the cupboards, they are the least useful for storage because of their shape. We settled on re-purposing the top cupboard as home for the heater (and its two boxes of electronics), with the controller/thermostat on the outside of the same cupboard, just above the seat back. With gas already supplied to the (three way) fridge, the gas pipe for the heater could be tee-jointed into the fridge plumbing and brought up through the lower cupboards. Tip. Have your gas plumber to review your intended location and orientation before you commit yourself.  This may cost you a service call, but it is better than cutting a second hole in the wall of the van.

Heater Installed
Heater Installed

This heater can be mounted in a number of, but not all, possible orientations. Factors in choosing an orientation include: where the hoses need to go, their maximum length and, importantly if space is limited, their turning circle (radius of curvature). We ultimately choose the orientation with the exhaust port facing the van wall and the heat vent pointing upward. This was driven by the respective shapes of the heater and cupboard, and by the fact that the turning circle of the heat outlet hose was significantly worse than that of the exhaust hose and so it needed more space in which to make a right-angled bend. If you need a tighter right-angle in the hot air hose than can be achieved with the 80mm flexible hose supplied, have a look at the fittings in the Truma catalogue. As well as a fixed elbow, it shows fittings to suit installations with multiple hot air outlets. Tip. Don’t cut any holes until you are confident that your chosen location and orientation is going to fit. Put everything in place as much as possible, without cutting anything irreplaceable, to prove that your proposed location and orientation is doable. Remember that you need access to tighten screws and the plumber needs access to connect the pipe.

Hindsight (3 years later)

After several years use, we regret putting the hot air outlet so high in the van.  In very cold weather, with the heater on, we have measured a difference of many degrees between the air near the ceiling and the air near the floor.  This means overheated faces but cold feet!

The reasons for this include:

  • hot air rises;
  • the floor of a caravan is less insulated than the walls and roof;
  • in wintry weather, the ground outside is wet and hence the air underneath the caravan is colder than the air to its sides and above.

Combined, these factors mean that the air near the floor needs heating more than the air near the ceiling. If we did it again, would put it the heater’s warm air outlet at floor level, and therefore mounting the heater as close to floor level as practical. Apparently, newer versions of this heater support multiple, distributed warm air outlets.  This seems like a good thing, but based on the above experience, we suggest that it should still be configured so that the majority of the warm air is expelled nearer to the floor than the ceiling. Unless the distribution system enables the flow from each outlet to be adjusted, this still means locating the heater near floor level.


Depending on the orientation, the heater is fixed to its surrounds at either three or four points, using the supplied metal “L” or flat brackets. That does not seem like many mounting points for a 5kg object attached to the gas pipes in a moving vehicle; they need to be robust fixings, as does whatever they are fixed to. Our heater’s vertical orientation meant fixing it at one point underneath it, to the shelf and in two places on the side of it, to one cupboard wall. The gas fitting protruded below shelf level.  We made a replacement shelf from 13mm MDF to avoid cutting the original shelf and to give ourselves the option of starting over if we got it wrong.   To reinforce the cupboard wall, two lengths of 42x19mm dressed pine were screwed (using an excessive number of screws) to that wall. The side brackets of the heater were then fixed to the pine with hex-head timber screws. Tip. A small, cordless screwdriver is invaluable when fixing the heater into a cupboard not much bigger than the heater. We bought one especially for this job, but found it so useful that it has a permanent place in the van. It is much lighter than  a cordless drill, occupies less storage space and has surprisingly good torque. It came with right-angle and offset screwing attachments, which actually work very well.

External Hole for Exhaust
External Hole for Exhaust

The exhaust requires a 70mm diameter hole in the van wall. This is not the first hole we have cut in that wall, but is the largest (previous was 22mm for an Ezy Eye antenna cable inlet). The position of the hole depends on a number of things, including: location of the heater and interior pathways for the exhaust hose, the profile of the exterior van wall (ours is aluminium with a profile reminiscent of weatherboards) and, less visible but very important, anything inside the wall such as electrical cabling. If you are unsure about whether there is something in the wall, try calling the manufacturer’s customer service team. We have found Jayco to be very helpful in this respect. Given the chassis number they can refer to the layout diagram: whilst it may not include details of actual cabling, they know the principles of manufacture and can tell you which areas to stay away from.

IMG_3654The position of the hot air outlet also deserves some thought. The black, plastic vent supplied has fixed, slanted fins and rotates so that the air stream can be directed. Our outlet is close to the ceiling (see picture) so by directing it sideways or downward, the ceiling is not overheated. You might not want hot air streaming onto your face or body so that might help decide it. Unless you position the heater so that the hot air outlet is flush with the cupboard wall, you will need to use the hose supplied to channel the hot air. Whether or not you use the hose, a hole will be required in the cupboard wall.

Tip. Don’t cut the hoses to length or fix them to the walls until as late as possible. Cut the holes but leave the pipes overlength and loose in the holes. This gives you more wriggle room when positioning and fixing the heater. The cold air inlet can either draw air through a hose (similar to the hot air outlet), or from within the cupboard, in which case the cupboard must be sufficiently vented. We cut down a wooden, rectangular vent and installed it in the door of our heater cupboard (see previous picture). Good quality hole saws are expensive and this may be the only hole you ever cut of this size, so borrow if you can but make sure that it is sharp. Hole-saws drill a pilot hole before the larger hole: this will tell you whether you lined up the inside and outside positions correctly so be sure to check where it came out on the other side before going further. If you are less than one radius out, you get another chance! Tip: Sometimes it can make sense to drill the pilot hole from one side and then cut the larger hole from the other. It all depends on the materials involved, what determines the position of the hole and which side has more margin for error.

Combined Controller & Thermostat
Combined Controller & Thermostat

The controller/thermostat can be mounted flush, which requires a 50mm (?) diameter hole in the woodwork, or using the supplied casing, which requires a hole drilled for the cable. The cable supplied is ample in length: where you locate the controller/thermostat is limited by available pathways for routing the cable. We used the casing and put it on the outside of the heater cupboard because that was as good a position as anywhere else. Another advantage of the chosen location for the heater was its proximity to the battery management system, which is under the fridge, and hence to a 12VDC supply. Our unit has some spare, separately fused 12V connections available, of which I used one for the heater.


Cowl Combine Air In and Exhaust Out
Cowl Combines Air In and Exhaust Out

It was late spring when we installed the heater and we have not yet had a winter in which to use it to its fullest. Our coldest morning in the van since installation of the heater was 12 degrees Celsius, so we took the opportunity to try it out. It took 40 minutes to raise the temperature to 22 degrees, which is encouraging.