Carrier A/C blows too hard--slow it down?

[kevinkatz]

my new carrier 15000 btu fan just blows too hard and loud for sleeping.
this is even on the low cool setting. can i put a rheostat in and slow down the fan motor? i would like the compressor and thermostat to work as normal but just slow the blower motor down.
anyone done this and have any tips?
thanks
kevin

[Silverwanabe]

You are correct about the noise level,

My 15k Carrier heat pump is also too loud.
Low speed is louder than the high speed on my Coleman.
Solution, I do not know.

[Maryw164]

I'd be interested in this too. We have the same unit in ours. Hopefully someone will have a brilliant idea.

Mary

[Steve & Mary]

I agree with the loud noise. One of our "must have" items when shopping for our AS was dual AC's. My thinking at the time was I wanted to make sure we would always be able to cool the trailer, regardless of how hot it was outside. Now we have learned the dual AC's are nice for addressing exactly the noise problem mentioned here. During the day when we spend most of our time in the forward end of the trailer, we use the rear AC. At night we run the forward AC. Seems to work out well for us. Our solution doesn't help out here but it may help someone shopping whether they opt out for single or dual AC's..........steve

[Phoenix]

When it's 115 degrees, we gladly put up with the noise just to have the cool air...

With all the mechanical parts just inches from your head, I don't think there is much one can do to reduce the noise. Also, the rheostat is a good idea; but I suspect the blower motor is AC, and I think that rheostats only work with DC motors. (Please correct me if my basic electronics knowledge has faded.)

Home air conditioners use jumpers or switches that set the blower speed, but I don't know if there is a way to do this on an RV AC unit.

[kevinkatz]

i am thinking of a rheostat where i put the asterisk. what do you think?
i have also posted this diagram in the airstream photos where it is bigger and easier to see.
kevin

[Minno]

I wonder if reducing the airflow by slowing down the fan will cause the unit to ice up? Ford had problems with A/C's icing up on the low fan speed a number of years ago. The fix, if I remember correctly, was to replace the resistor pack so the low speed wasn't so slow. Plus that voiding the warrenty issue of you modify a new unit. Just two things to think about.

[Aerowood]

Most AC's have to have the fan blowing at a minimum speed in in order to cause the coolant to evaporate. If liquid coolant enters the compressor it can cause the compressor to liquid lock or slug. This can cause damage to the compressor. There should be a pressure safety switch to turn off the unit in the event that this happens before damage can occur. So the short answer is, do not slow down the blower slower then the slowest speed or you could damage the compressor. At least this is how the units I work on operate as I get complaints all the time about how loud our units are, and why can't I slow them down so that they will be quieter.

[kevinkatz]

appeciate input from aerowood, phoenix and minno. in my new house that i built, the a/c man suggested that i put really big vents and return air in. what that does is blow the air through larger area and make it less noisy. i may try modifying the vents so that the air is not forced out of the smaller ducting and see if it quietens down. can easily try this by taking inner unit down but still leaving it electrically connected.
i am not near my caravel now, but when i am, i will experiment.
ideas?

[Pahaska]

We had a problem with the cold air blowing right in our faces while sitting on the couch. The new Dometics have a 3rd vent in the bottom of the shroud that blows downward. I installed a furnace vent in the bottom of my AC shroud to do the same thing. I used a vent with flappers that allow me to turn the new vent almost off when we really want air in the ends of the trailer.

I notice that the noise is less with the new vent open. This might help your situation. You could even install two additional vents to further reduce air velocity.

[Grumpycamper]

I really like the idea of adding extra vents. I know in my MH the extra vents would help cool the area directly under the units as well as help with sound, however the sound is not bad in it. I plan on doing some work to the Penguin unit in my Bambi and will try that also. When I was younger I worked for an A/C contractor and when we had a complaint of excessive noise in homes we insulated the return air space with carpet or insulation to absorb the noise and it worked very well. I don't know that there is a lot of places or room for foam or something inside the unit but I am going to try that also. The Bambi with its small area and all hard surfaces the A/C is really loud and it seems to be a common problem.

[moosetags]

Originally Posted by Pahaska

We had a problem with the cold air blowing right in our faces while sitting on the couch. The new Dometics have a 3rd vent in the bottom of the shroud that blows downward. I installed a furnace vent in the bottom of my AC shroud to do the same thing. I used a vent with flappers that allow me to turn the new vent almost off when we really want air in the ends of the trailer.

I notice that the noise is less with the new vent open. This might help your situation. You could even install two additional vents to further reduce air velocity.

John,

Do you have any tips on installing the furnace vent in the bottom center of the A/C shroud?

Thanx, Brian

[Pahaska]

Originally Posted by moosetags

John,

Do you have any tips on installing the furnace vent in the bottom center of the A/C shroud?

Thanx, Brian

I used the same kind of vent that is on the furnace, but I chose one that had adjustable dampers. I put some masking tape on the shroud and marked the center line. I then took the vent apart, lined up the back part of the vent against the shroud, and marked around it with a sharpie pen. I used a flashlight to look through the end louvers to make sure I would not hit anything inside and then used a sabre saw with a short blade to cut around the mark. Three screws hold the back of the ven t in place and the front of the vent snaps into the back part. It was a 10-minute job.

The airflow tends to blow the dampers shut. I cut little notches in the ends of the arms that catch on the edge of the vent when I want the vent held open. Even with the dampers closed, there is some airflow out of the new vent.