Diesel Heaters

Sounds very excessive to me - have a 10L tank for mine which I'm reliably told will last for several days of constant use. I've only used my heater sporadically so can't confirm actual fuel usage but 20L seems a ridiculous amount. Suggest you talk to your installer. Best of luck
Cheers
TG

What brand?
My Webasto uses less than half litre per hour on full blast in sub zero conditions.
When van has warmed up and heater is running often enough to keep van at around 23º then about half that consumption.

Do you have raw fuel coming out the exhaust?

Bob

Include brand and specific model, plus size of tank etc. - more info gets better advice....... are you quite sure about the hours and the litres ? These things are super efficient........ if it was going to use that amount, I'd have thought it would have shut down with a fault.

my Webasto uses about 3 ltrs of fuel if i run it from about 7.30 p.m until about 7.00 a.m the next morning in our Kimberley Kamper. i have the temp set so it basically runs all night, no cutting in and out, as i find the noise of it starting up again in the middle of the night a touch annoying. i'm not sure exactly what temperature it was set at (about halfway on the dial), but it was warm enough for me to sleep on top of the bed in shorts and t shirt down near Stanthorpe in Winter.

Your heater is using approx 10 times the fuel it should. If your numbers are correct, as others have suggested, get it checked ASAP

Cheers
Racey