Fuel for Thought

Out with the New and In with the Newer

As mentioned in a previous blog, The Hole Project was a success. Cutting a hole in the roof of my new truck and installing a rooftop heat pump went as planned. What was not planned well was the unit I installed on the roof of my mid roof sleeper. The unit itself worked great. It put out plenty of heat and cold air, however, it was just a little too big for the space.
Whenever you plan to install a heat pump, be it in a house or on a truck sleeper, bigger is not necessarily better. If it is too large, it will cycle often since it heats or cools the space quickly but that means it starts and stops often. This can lead to increased power consumption and also swings in temperatures rather than a steady comfortable temperature.
In my previous truck, I had installed a 9000 BTU mini split heat pump and it worked great for an 82” OEM sleeper. For the new truck, I installed a 15,000 BTU rooftop heat pump. It turned out to be too large for the 72” OEM sleeper I now have.
So, off with the new and on with the newer. When considering any power using appliances on your truck you have to consider that your generator or APU will be providing the power and the more power the appliance uses, the more fuel you will use to run it. Air conditioners and heat pumps tend to have a power surge when starting the compressor. While the 15,000 BTU unit I initially chose did not use a lot of power after the initial startup, the fact that it started and stopped too often did increase the power consumption, thus increasing the fuel consumption.
I replaced the new unit with a 13,500 BTU Inverter heat pump. While the unit is not that much smaller in BTUs, the inverter style compressor makes it run more efficiently. This new unit ramps up slowly when starting and only runs around 1100 - 1200 watts on high. This is akin to the inverter generators which only ramp up RPMs when power is needed, instead of running full throttle all the time. The result is quieter operation, less power needed to run and uses less watts to run all while keeping a steady temperature in the cab and sleeper. As you may know, using fewer watts equates to less amps which means you could even run it on a small generator, but with a 4000 watt or larger generator, you can run the heat or A/C and still use the microwave or air fryer at the same time.
If you are looking to add a rooftop heat pump to your truck or replace an old rooftop air conditioner, consider the new technology available with an inverter compressor style unit.
I still consider The Hole Project a success, although I had to make a modification to achieve the results I wanted. When your first attempt is lacking, try a different Iteration for a different and better result.

There is nothing permanent except change.
- Heraclitus

See you down the road,
Greg