A gas powered instant water heat–experimenting with jet sizes

In this post I got over how I fixed this boiler up to work in my van. The gas wasn’t burning properly and was quite unsafe. This is to heat the water for the shower–see shower post

I knew nothing about water heaters or boilers before taking this apart and had a lot of questions to which a lot of my answers were along the lines of ‘if your asking that then you shouldn’t be messing about with it’. But messing about with it is EXACTLY what I need to do. Now I know this works and I can use it safely how I want.

This is a cheapo Chinese Ebay water heater.
The label on the unit says it runs on LPG but upon testing, It was clear the flame was not burning properly.
Running on propane at 37mbar. The carbon monoxide monitor alarmed almost right away and gave a reading of 900ppm which is ridiculous since it was being tested outside! scrap or investigate?
I had a look inside. There is nothing to these things – A water flow lever hits a microswitch which sparks the electronic piezo ignition and operates the incoming gas solenoid after a couple of seconds. The gas then comes in through a thermostat control (gas flow control) and enters the 6 jet assembly where it mixes with air and enters the 3 rows of gas diffusers to heat the water via the heat exchanger directly above. Water flow can also be controlled – less flow = hotter.
I removed the gas diffuser to access the jets (middle jet removed in this picture). I compared these hole sizes with the ones in the hob. They seemed larger which would confirm my suspicion of this heater being for natural gas which requires about 2.5 less oxygen than propane to burn.
Learning time. I wrapped masking tape around all of the jets and found a pin with the exact size of the jet in the hob and used it to create a new hole in the masking tape. Note, this is not a fix and certainly not a permanent solution! I am just trying to establish whether the factory fitted jet sizes are too large for propane
We cautiously fired the boiler up with the modified jets. Check out those nice blue flame! the monoxide monitor did not even alarm and the flames burnt smooth as anything with no orange flames in sight. The conclusion is that the jets are the wrong type for the quoted gas type on the label. I will be installing brand new LPG jets

Update: I contacted all the suppliers of this boiler I could find and none could help me find some replacement LPG jets so went for the next option – upgrade the masking tape for aluminium tape.

Here is the brass gas jet. I will wrap these in foil tape and puncture a new hole
I found a needle that perfectly fits an LPG jet (from the cooker) and used it to pierce a new hole in the foil. I was able to get a really clean hole with no tears in the foil
Tests were successful – after burning for about 15 minutes but I’ll see how the foil holds up after a few months.

Conclusion – should I use this heater?

These heaters work really well. The water heats up in seconds and the boiler only operates when the tap is open. No storing of water and waiting 20 minutes for water to heat up just so you can wash your hands. This is a neat and convenient little heater but should only be used for intermittent use (washing etc).

Potential safety risks with this type of boiler:

  • open flue–uses oxygen from room and may also vent CO if the flames do not burn properly
  • when used with a self priming pump, a leak after the output of the heater may be enough to engage the flow switch and turn the boiler on inadvertently
  • outer housing can get rather warm due to its very compact size–they’ve squeezed it all in.
  • has to burn a lot of gas to quickly get the water hot

The heater will only be used for a minute or 2 at a time–fill sink with hot water or wash hands. The amount of oxygen in the room it uses up will not be significant in that amount of time. A 12v extractor fan is also fitted to the roof for air ventilation and gases are vented through a fixed flue in the roof.

People seem to get very upset about these types of water heaters in vans but I think it all depends on how it is used. Let’s not forget about the gas hob–the flames are not contained, is used for longer periods and a lot easier to leave switched on. That’s more dangerous in my opinion.

I’m going to see how I get on with this water heater and if I find my self using a lot more hot water then I’ll look at other options.

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let me help you with that



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