I posted this information online because someone else might need it, spent a couple of evenings in the garage.
A friend of mine made a heating system for campers, the heart of which was discussed earlier here is the Webasto Thermo Top C diesel heater.
Unfortunately, something happened and both the heater electronics and its separate fuel pump stopped working.
Repeated visits to the repair site, and now the system is working again (in the test facility in the garage, see picture), but with a reduced thermal output – 1 kW instead of 5 kW – the temperature rise is measured by determining the time it takes for the water to heat up to a temperature above 20°C.
Perplexed, and finally the answer: although they all look alike, not all diesel pumps are the same. Many diesel pumps designed for use with Webasto and Eberspatcher water and air heaters (among others) are calibrated to deliver varying amounts of diesel fuel per input pulse.
These pumps, which I now know are correctly called metering pumps, are driven by 12V (or 24V, depending on the model) pulses from the heater.
Each heating unit will only work properly with a pump that delivers a certain dose per pulse, as it regulates the flow by pulsing the pump at a fixed speed – if it is a unit with multiple heat outputs, multiple fixed speeds can be used.
Ignorant or deliberate, many people who sell aftermarket pumps ignore the fact that they list a long list of “compatible” heaters – after all, if it’s not very long, how many people will notice a change in heat output.
The system is open-loop, so if the wrong pump is installed, it will get the wrong amount of fuel – too little fuel per pulse and too little heat, too much – and you risk overheating.
Some other pumps measure in milliliters a fixed number of pulses (sometimes called “pumps”) – I’ve seen numbers for every 100 pumps, every 200 pumps and other numbers – and sometimes this number is equal to one pulse per minute, delivering the desired number of pulses. pulses or other heating settings.
There are also pumps “22 ml” and “16 ml”, which correspond to volumes per 1000 pulses. They seem free for 1-3 kW and 1-4 kW air heaters.
Another example of a pump would be the Eberspatcher block, rated at 5.5-6.0 ml for 200 strokes, which is half the pump needed, so if installed randomly, the heat output will be halved. Or a “22 ml” pump can provide about a third of the heat.
Didn’t measure, but it looks like the randomly selected pumps currently in use (from unbranded Chinese air heaters) (only visible in the top right corner of the photo) have a much lower output per impulse than the Top C requirement.
In addition to spending hours in the freezer garage, I used a lot of resources to put together this page. Especially recommended:
Berkshire’s marine varnish company B&D Murkin generously offered this – diesel heaters are often installed on board.
The Butler Technik technical library in Lincolnshire has established itself as a reliable supplier of diesel heater parts.
And pay attention to the controller with the red number in the upper right corner? – Made to control hot air and hot water systems and so far working fine. If someone wants to build a similar system, I’ll be happy to submit it to EinW.
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Post time: Apr-17-2023