differance between 13500 BTU/Ac and 15000 BTU/AC

mikefos wrote:

ktmrfs wrote:

2) add more vents. easy to do, the duct runs are straight, follow them and add more. I added one more in our Bedroom, one in the bath that didn't have one, and two more in the living area. Made a very noticeable difference

I am entertaining adding an additional vent in the bedroom, as that seems to be our problem area w/ cooling down, if it would help enough to warrant the effort. Could you please provide some detail how you did this and what tools you used? Thanks.

the process in my case was pretty straightfoward. First locate the plenum run you want to install a duct in. Normally these are straight runs and often go beyond the last vent. Pull a vent and you should be able to see the plenum location. Hint. if there are two or more vents in a run, it's likely a straight run between them. Hint, they use as few runs as possible so likelyhood of 2 or more vents in on run is common.
Once you have located the plenum run, and got new vents measure them to see the hole size. To cut the hole there are at least three options. Best option use a hole saw on a drill, but this size hole saw isn't inexpensive. Next choice use an adjustable circle cutter on a drill, last choice use a jig saw to cut the hole. you will go through the ceiling and into the duct.

Once the opening is cut, use aluminum duct tape to mate the ceiling with the duct to avoid any air leak, install the vent and your done.

Let's see 15000-13500 = 1500 or 10% of the 15000 So it WILL make a difference, but you may need test equipment to find out how much (you won't notice it)

I do however recommend the upgrade on a "Burned out Bulb" basis.. When my A/C's failed I went from 13,5K to 15K. on the rear one this did NOT increase the power draw (but it is harder to start. fixing soon) the front one I draw 0.8 amps more again way less than 10% difference.

My front is a Coleman. works great Back is Advent Air. not so easy to work on but .. Well that's the hard to start one.. The fan blew up and I put a coleman fan in it so it sucks now instead of blows (makes it easier to clean the condenser).

Rhigley wrote:
I have a 31 foot class C motor home with a 13500 BTU/ac and it will not keep my unit cool. It runs all day and most the night. Will a 15000 BTU unit make a big enough difference or is their something else I can do to make this one work. I have single pain windows and know that's not helping. I have dark covers over all my vents.

NO! An additional 1500 BTU's will not make any noticeable difference when it comes to your comfort.

ktmrfs wrote:

2) add more vents. easy to do, the duct runs are straight, follow them and add more. I added one more in our Bedroom, one in the bath that didn't have one, and two more in the living area. Made a very noticeable difference

I am entertaining adding an additional vent in the bedroom, as that seems to be our problem area w/ cooling down, if it would help enough to warrant the effort. Could you please provide some detail how you did this and what tools you used? Thanks.

I kicked the air on today and at 85 deg. outside I am drawing 12 amps. I have a 20 deg difference from inlet to outlet on the closest ducts. I get good airflow out of all my ducts and took pictures of the ducting and see no blockage. I get 80 deg on inlet and 60 on outlet. Looks like putting another 13500 in the bedroom might be the only option.
.

Someone who had good results going to 15K A/C.

Bill

We previously had a 28 ft TT with a non-ducted 13.5 K rooftop ac unit. I recall camping in upper 90F temps and that unit was always adequate for keeping cool. Our ducted MoHo has 2 13.5 K units and we need both cranking at similar temps to maintain adequacy. I think the problem is that ducted units are constrained and cannot supply enough air to cool adequately, having owned both types of campers.

A suggestion to the OP: try using a fan to better circulate air in the TT and see if this helps the 13.5 K AC.

Good luck.

ol Bombero-JC wrote:
You should get about 20 degrees lower than outside temp.

I believe that's a common misconception about what to look for in a properly operating an air conditioner.

A properly operating air conditioner's output air temperature should read about 20 degrees lower than it's input air temperature.

Since an RV's air conditioner only recirculates air inside the RV and doesn't actually bring in "new air" from the outside (unless there's a leak in it's ducting somewhere), the air inside the RV is supposed to get colder and colder until the inside air temperature reaches what one sets on it's control.

HOWEVER ... if the cooling capacity of the RV's air conditioner isn't enough to swamp out the amount of heat gain of the RV from the outside (through windows, poorly insulated ceilings and walls, etc.), the air conditioner just keeps running and running trying to get the inside air temperature down to what is set on it's control.

All the while this is happening, a properly operating air conditioner's output air temperature should read 20 degrees lower than it's input air temperature. It's just that the inside air temperature (temperature of the input air to the air conditioner) is constantly getting heated faster from the outside than what the air conditioner can cool - capacity-wise ... so the setting on the control is never reached.

If you really want to add a second A/C to you 30 amp system, how about a Coleman Mach 8 Cub 9.2K A/C.

Richard

Dick_B wrote:
How cool is cool? Did the A/C EVER keep it cool enough? Is the A/C working efficiently, ie? Fins clean, filter clean. Assuming it is ducted does the air come out of each vent the same amount?
We use a fan all the time.

As above.......

Check to see if your A/C is working properly - cooling output.

Buy an air conditioner testing thermometer. Looks like a meat thermometer. It's placed (inserted) in a/the discharge vent.
(Cheap - any auto parts store).

You should get about 20 degrees lower than outside temp.
(You can test the tester by doing same on your auto A/C).

:C