Chinese Diesel Heater

Now a for bit of a run down, of what I hav.4e found, since buying a CDH....

I paid £67.39, for a suitcase type, 8kw heater, as the suitcase version appeared to be cheaper, and include all the bits. It was bought to replace a wood stove, which took time to warm my workshop up, and caused dust. It came with all that was needed, but I decided to add a filter, plus change the green fuel pipe to white nylon, move the tank to somewhere more easily accessed to fill it. I also bought a spare parts kit, glow-pin, spanner, mesh, along removal tool, plus gaskets.

I did investigate running it on waste oil, waste chip oil, and various other substances, as a cheap option, but the research suggested that was a bad idea. It did suggest it was fine run on white or red diesel, kero/heating oil, or Jet A1. White seems to be particularly cheap at the moment, but the cheapest fuel I was able to find was the Jet A1 at 94p per litre, from my local aero club.

The unit seems well-made, comes with a remote control, to turn its stat up and down, plus on or off, and so far 100% reliable, the little use I have made of it. You apply the 12v, press the on button, then 2 or 3 minutes later it is producing some heat. The amount of heat then gradually increases, as it warms up to maximum output. In a matter of ten minutes, my workshop is warm. Turning it off, it continues to run it's fan, to cool itself down, for a few minutes, which is essential to avoid the electronics, inside the unit, being cooked. For that reason, it is best run from a 12v battery, itself on a charger, rather than just a mains adaptor, in case mains power is lost. They draw around 13amps to start the burn, then 2 to 4amps once fully lit.

They are simple enough - just a solenoid dosing pump, injecting a pulse of fuel, each time the pump is fired. A wire mesh, around a glow-pin, into which the fuel is injected. The pin heat the mesh, ignites the fuel, then a variable speed blower, blow air into the chamber. Eventually, the glow pin can be switched off, and the burn self-sustains. The burn chamber is an allow casting, which gets hot. The same blower motor, has an air fan on the other end of the shaft, blowing air through the hot casting, which is the hot air which exits via a large duct. So you have 4 -ports on the unit, combustion air in, exhaust gas out, room air in, hot room air hot. The combustion, is entirely sealed away inside the unit, so not combustion products get into the room.

Rather than waste the heat from the exhaust, and as the unit was mounted on my work bench, I decided to risk spirally the exhaust round, below my bench, before exiting out through the wall, and add a small fan, to blow cold air over it. I've added a CO and CO2 monitor alarm, for safety, but the space is generally well ventilated anyway.
 
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I have the pair of W1209 modules wired up, and working just fine on the bench, next trick is to connect them to the heater control and test them in earnest.

Which I did this afternoon....

For ID purposes, my control is the black, 5 button control, with a cog like symbol, below the setting button, middle button on the left, serves both as on and off, depending on whether it is already on, or off. It is opened up, by unsticking the stuck on face cover panel, through which the button tops poke. Best teased up around the edge, with a knife. That panel, hides a screw in each corner, undo those, tease the PCB out.

Two thin flexible wires, now need to be soldered across the switch button. The button when pressed, connects the two pins on the left, to the two on the right, so the wires need connecting one to either of the left pins, and the other to either of the right pins. Those two wires then go to BOTH of the W1209 K0 and K1, so that either W1209, can short out the on/off button.

My W1209's, were mounted side by side, the left one sets on switch on temperature, the right, the switch off temperature. I set the left up for H (heat), right for C (cool), each with an hysteresis, of 0.1C. Left to trigger on at 16C, right to trigger off at 17C. Both thermocouples, taped together, then tried running it with several cycles. It worked absolutely fine, but due to the pre-heating cycling, and cooling down cycle, the heater over and undershot the set temperatures - no way to escape that, with this type of heater.
 
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