Searching For The Impossible - A Truly Quiet RV AC

[JDinFbg]

Our RV has a single Coleman Mach 15, 15,000 BTU non-ducted, roof-mount AC. From what I've researched, it is supposed one of the quieter units at around 59 dbA on high fan speed. We always run on low fan speed so it should be less noisy, but we still find the fan noise unacceptable. The compressor 'rumble' does not bother us. Further, we have the choice of running the fan in auto where it cycles on and off with the compressor, or continuously on at the selected speed. The fan is too noisy to let it run continuously, but by cycling there are big 'comfort' temperature swing in the RV.


Does anyone make a 15,000 BTU AC that has a variable speed fan such that it would slow down to some 'idle' speed to keep some air movement going after the compressor shuts off, but at much, much less noise level, then slowly ramp back up after the compressor comes back on? If anyone know of such an animal, please post some links. But, as the title says, I may be searching for the impossible.

[Melungeon]

There are a couple of variable speed units on the market now. The Furrion Chill Cube is an LG variable split with a Furrion label on it. They have been out for over a year and Brinkley is now using them as OEM on some of their models. They have a non-ducted model and just since earlier this year offer a ducted model. It's actually 18K BTU.

There's also a Turbro Greenland which is only offered in non-ducted and is also a heat pump. You can find an excellent Youtube video about this one where they measure many performance parameters.

Not only are the variable speeds quieter, they always start on a very low speed and ramp up so there's no surge or inrush. They never stop completely, under a no cooling load time they continue to dehumidify.

[SafariBen]

Originally Posted by Melungeon

... under a no cooling load time they continue to dehumidify.

Interesting strategy. That's the reason an A/C doesn't want to run the fan after the compressor shuts off, you get the evaporator warming up and then the fan is circulating warm moist air. A variable speed could ramp up over ten seconds before starting the compressor just to hide the noise though.

[Melungeon]

Originally Posted by SafariBen

Interesting strategy. That's the reason an A/C doesn't want to run the fan after the compressor shuts off, you get the evaporator warming up and then the fan is circulating warm moist air. A variable speed could ramp up over ten seconds before starting the compressor just to hide the noise though.

The residential variable speeds keep the compressor running at a very low speed too, not sure about this one. This keeps the evap coil good and wet so it gets to max efficiency quicker, keeps the latent load in the room much lower, comfort level higher, adjusts to smaller temp increases. These are great for the "shoulder season" typically in spring when there's a lot of rain and humidity and little to no cooling load. All the while drawing 2-3 amps max. Typically the compressor, evap & condenser fans, and the EXV all modulate at same rate.

[Mudfrog]

Originally Posted by Melungeon

The residential variable speeds keep the compressor running at a very low speed too, not sure about this one. This keeps the evap coil good and wet so it gets to max efficiency quicker, keeps the latent load in the room much lower, comfort level higher, adjusts to smaller temp increases. These are great for the "shoulder season" typically in spring when there's a lot of rain and humidity and little to no cooling load. All the while drawing 2-3 amps max. Typically the compressor, evap & condenser fans, and the EXV all modulate at same rate.

I don't see a system like this working very well in a high humidity location. The compressor needs to be running to wring out the moisture. You're gonna feel it between compressor cycles if the fan runs constantly in a smallish RV with breathing humans inside. Probably ok in Arizona but not so great down here in southeast Texas. I also don't like the idea of the fan running all the time, especially if it's pulling 2 or 3 amps.

Can't help to give the OP a good answer. The air flow noise our old Coleman Mach makes when it's running seems to help us sleep better.

Now,, I have read on here where people bought aftermarket devices to help with the noise. I have no idea if or how well they work but there have been posts saying it helps.

Edited to add: This is the device mentioned in previous threads.

Wacko Products

[PS89]

We have a C-M 15 as the forward A/C unit factory-installed on our '18 29M. I installed the DIY insulation foam and metal tape mod on it and it helped quiet down the unit a little.

I later installed a second A/C over the bedroom. I picked the Houghton A3501 sold by Recpro. It has a selectable 3-speed fan that runs all the time (unless turned off) and the compressor cycles on and off as needed. As rooftop A/C units go, it is very quiet. It does have some operating quirks that are easily handled once you learn them.

If When the original C-M fails, I'll probably replace it with the Houghton A3801 which includes a heat pump.