The object of my repair efforts this time: a Coleman Instant Hot Water system for camping. The product is nice, the company is lousy and unwilling to sell any spare parts; but that kind of plot does not work with me.

Rob got this very nice gadget a few years ago from a bunch of us as a birthday present. Since then he (and I amongst others) have used it quite a number of times for having a nice shower (while|despite) camping in Killarney.

Only last time we wanted to use it at easter it burned. Which usually is a Nice Thing in a gas water heater, but unfortunately not when the fire happens somewhere outside the heat exchanger. On the first whiff of burning plastic and smoke coming out of the vents we shut it down and went on being dirty.

Rob then tried to get Coleman to have a look, but they wanted ridiculous amounts of money just for an inspection. Instead, Rob gave me the broken heater. By now he knows my insatiable curiosity and stubbornness when non-working things are involved, so that was obviously a smart move on his part.

A few days ago I ripped the sucker apart and found out that the battery charging board was toast, literally.

 toasted-pcb toasted-pcb

A number of wires in the vicinity were fried, too, but the main controller board (potted in some silicone-like jelly) seemed ok except for a medium-rare relay. So the first step was to rewire all the mess. Goodbye charging board, we'll have to use the Swallow externally in the future.

Initially I couldn't find any good reason for the fire, so I assumed that the charging board had shorted. Next step: a function test. The electrical bits were now fine, but without gas the controller shuts things down quite quickly. So I carefully screwed in a cartridge, only to be greeted with LOTS of gas blowing out somewhere. Rechecked the sealing washers, tried again, no luck: thar she blows!

After stinking up the back yard a number of times I realized where the leak was: the builtin gas pressure regulator had ripped its diaphragm, so all the gas went out the stupidly positioned vent hole...into the case, where it ignited and toasted things. I'm somewhat underimpressed by that design.

And of course that pressure-and-flow-regulator is made from unobtainium. But when in doubt I'm happy to use industrial strength Brute Force and Ignorance.

So I got a garden-variety regulator with hose, a 2kg LPG bottle and some semi-matching fittings. Removed the dud regulator and replaced the main switch. I had to fab a new mount for the gas solenoid valve but in the end I managed to keep all the safety features working. The heater setup is quite nice actually; a fail-closed solenoid gas valve, flame detector and auto-ignition, water flow sensor, tilt switch and thermostat.


Controlling the temperature of the resulting Franken-heater now involves manipulating the source (UTSL!) - one has to judiciously frob the gas bottle valve. To aid that I made the flames properly visible from the outside: the Coleman idiots have provided a nice viewport in the copper heat exchanger shroud but no hole in the surrounding plastic shell.

 coleman-burntest coleman-burntest coleman-burntest

Net cost: about $55 for regulator, hose and gas bottle, and a bit of my time.
Gross result: it works again, I'm happy, let's have some of those BTUs.

[ published on Fri 01.08.2008 23:23 | filed in interests/tinkering | ]
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