Brunnhilde said that is too loud

 

The Coleman Mach 8 Polar Cub roof top air conditioner is a very loud machine to operate, partly because of its low profile design at the time. I am not at all impressed with all the RV rooftop ACs designed in the US. They are very crude in design, loud, and far from ergonomic, but this is the market we are in. There were not much choices when I install it about 5 years ago. The excessive exterior noise is one of the biggest problem, and I finally ready to confront it head on.

armed with a noise meter I first wanted to take some baseline measurements; I use 3 meter distance for the sound pressure measurement about level with the middle of the air conditioner in elevation

I took many measurements using both A weighted and C weighted. The A weighted reading is lower due to its compensation for human auditory characteristics. 

once I establish the baseline readings, it's time to get to work; the day is forecasted with strong wind and since I need to open the big Heki skylight to do much of the work I started early in the morning, also taking advantage of the cooler ambient

By the next day noon, I have this conquered. It is now much quieter now on the outside, that it is no longer objectionable. While you can spend about $400 for a kit and install it yourself, I wanted to seek my own solution. It is not rocket science, but to sort out idiots that "designed" these RV air conditioners. Along the way I also corrected the sagging problem with the soft plastic cover where at a couple of spots the fan blades begun to grind off a bit of the plastic fan grill.

So how much quieter is now. Rather than using SPL measurement, to describe it in layman's terms relative to a good reference that is the Honda EU2000i generator. Before the AC's noise when the compressor is on the dominant noise is the Coleman AC on the roof for an observer any distance around Brunnhilde. Now the Coleman AC is not the dominant noise source when on. The Honda generator is louder for the observer. Not just when the compressor is running, but now even when it is off and the generator is idling in Eco mode. You cannot discern as an observer if the compressor is off, except by the RPM and sound of the generator. It is that much quieter.

It is too windy to take the "after" sound pressure level measurement. Just climbing up the ladder and listen to it 3 feet away the difference is huge, as is standing 25 ft away up on my side porch which I have good idea how loud it was before. Another vexing pest issue sorted.

In reviewing the recent works I did to sort out the Coleman air conditioner. All that transformed it from one of the worst unit to a very usable and livable system, far more than you can achieve by buying all these aftermarket improvement kits. Additionally, not using the very restrictive indoor unit from Coleman for this AC but to reuse the cabinet in the James Cook the comfort air flow is far less restricted and hence quieter and more efficient. I easily invested over 50 man hours in all adapted this unit in place of the Kerstner DC one, and overcame countless challenges and constraints along the way.