Will getting a larger roof A/C solve the problem?

It's probably getting time to replace.

Ours are 13.5 btu in a 17 year old motorhome. We have the sun shining on the passenger side from the time it pops up in the morning until about 3pm when we are then shaded. Awning is out to provide as much shade on that side as possible. Even in 90 with humidity, we are around 75-78 inside running only 1 of the ducted A/C units. We have a small oscillating fan blowing from front to back and we are very comfortable. When they start not cooling well, we will then replace because of their age but for now even with full-time use we are always cool enough.

There will a real benefit if your old ac unit isn't actually making the BTU it's rated for.

Older units rarely run like new. outside coils get dirty and damaged, fan blades get dirt on them that inhibits the correct flow, inside coils get dirty, seals between the supply and return leak, thermostats quit controlling the temperature correctly.

All of this can be delt with but sometimes a new unit is what you need.

2,500 btu increase isn't very much. Yes it will help a little but when the temperature is over 95 degrees you won't get the full 2,500 btu increase anyway. I don't think it will be miraculously cool but it will be better

Hi,

The trick is to not allow the RV to get hot it the first place. Don't wait until the unit is uncomfortably hot before starting the roof air.

Reduce the heat load by using vent pillows.

Create roof pillows for any skylights.

Reduce HL by using reflectrix on the exterior of any windows that face the sun.

If possible spray water on the sun side walls.

Finding some shade to park under can be a Godsend in the summer Sun.
Make sure your current AC is working as it's designed to.

As others have shared, to get the heat out of the condenser coil is essential to the interior cooling. Just as important is a roof surface that reflects the Suns heat. Black is very bad, grey is bad and white is best for reflecting the Suns heat. Any heat load you can reduce is equal to adding AC capacity.

Another problem is unit short cycling because of cold air on the outlet inside the ac bypassing the outlet and getting in the return side, causing the thermostat to turn off the compressor, even though the interior is hot. The cover has walls inside it that have a seal on their edge to prevent this from happening, it's just a foam weather strip that rots over time and no longer seals.

All of this contributes to what you describe.

psalm10720 wrote:
I have a 1993 Winnebago Brave 27RC and it has a coleman roof A/C. The BTU's are about 12,500. If I install a 15,000 Coleman roof A/C will it stay cool better in the hot Florida summer afternoon?

Not really. The heat load is the big culprit, and 2,500 more BTU's will do very little. Ask yourself, how much cooling would I get from a 2,500 BTU air conditioner? Would a unit that size cool down my RV just a little? However much a unit that size would cool down your RV, that is how much effect the 15000 unit will have.

Save your money and invest in other strategies such as window tinting, extra insulation, or even a portable air conditioning unit.

hi

Hello ???

Thanks for all the feedback... when I get home I'll definitely take the outside cover off and look at the fins... adding a second one is impossible in my case.... you've answered my question about the difference in BTUs.. my present unit works okay up until around the afternoon during the summer months.. while home I run the air conditioning all day long with the shades drawn and then the late afternoon I can tell that it just isn't powerful enough to keep the edge off the heat,,, when the Sun goes down and catches up again

1. They do not make and never have made a 12.5 k btu AC. You have either a 11.0 or a 13.5.
2. A 13.5 AC WILL NOT cool a RV 25 foot or longer to comfortable temps in 90 plus ambient
3. Going to a 15k will help a lot. That extra 1500 BTU's will be enough to get you comfortable on a 27 foot unit.
4. Since the AC is almost 25 years old, it will be better to replace it and not wait until it fails. Doug