Initially I received this product and needed it for a 24 volt system. When I opened the box, the instruction manual said 12 volt, the device said 12 or 24 volt, and the diesel pump said 12 volt. After asking for clarification and contacting Amazon, I ended up being refunded. However, I later received a reply stating that the pump which says 12 volt, also can be used with 24 volt. I decided to try installing the device. First I opened it up, and discovered that the internal screws weren't fully tightened. I therefore torqued all the internal screws down and made sure the device seemed in order. I installed it, expecting it to maybe not function. To my surprise, it self-primed the 4 meter long fuel line (I used 2 mm nylon fuel line) in just 3 tried. The heater turns on fast, and it ran for 12 hours last time without a problem. I am very happy with the heater and would recommend it to anyone who is handy, so that you can open it up if needed and tighten screws or fix any issues. As a product, it really does work and heats my space well.