How cold should roof ac blow???

[doublehooked]

I live in FL. it's 98 deg. outside coach is 92deg . 1 ac unit running for about two hrs. Roof ac blowing out at about 69-70 degs. Should it be blowing colder?

Thanks
Gary

[AFChap]

Common "wisdom" from ac techs says if your ac output is 20 degrees less than the return air temp, it is "working properly." I don't have roof air so cannot say for sure. But, with my basement air running one compressor it is right at 20 degrees difference ...with both compressors running it is closer to 40 degrees.

[JoeT]

That 20 degree differential is called the 'Delta T'. 20 degrees at 50% humidity is what a properly working unit should produce. It can be a little more or less depending on the humidity.

[wa8yxm]

Two things

1: If you go to the A/C maker's web site they will likely have a chart you can download, It requires you take a wet bulb temp both inside and out, then a dry bulb reading at the air inlet top side, at the air outlet top side, and at both inlet and outlet bottomside (inside) and then go to the chart and it will say.. Most likely.. NOT WORKING PROPERLY.

Now, back topside,, You will need.. screwdriver, Garden hose, Sprayer

TURN OFF AC BEFORE CLIMBING LADDER (in fact turn off it's circuit breaker)

Now up the ladder

Remove the cover,, Look at the 'Back side" (Inside) of the condenser coils (The hot coils) see all that crud covering them.. HOSE IT OFF.

Replace cover
Tools (And you) to ground level

Breaker on

A/C on

Take new mesaurements...... I'm guessing you'll be happier.

I know I was

[TXiceman]

Difference between supply air and air out let on the roof top of for that matter even home A/C unit is 18 to 20 deg F. As for cooling the RV...get shade on as much of it as possible. The windshield is a hug heat gain. The insulation in the big plastic and metal box is generally less than 1/2 of what you have in a home. A 15,000BTUH unit is 1.25 tons of cooling capacity.

Any RV over about 28' should have 2 units, dual 15K or 13.5K BTUH.

Ken

[Gary - K7GLD]

FWIW - the ancient Dometic rooftop AC on our '88 Winnie registers 38-42 degrees at the output with inside ambient at 90 degrees or better - but still pretty warm inside due to all the large glass area - the single unit is OK, as long as we are careful to close windows and blinds before internal temps get too high...

[hamguy]

Quote:

Originally Posted by doublehooked I live in FL. it's 98 deg. outside coach is 92deg . 1 ac unit running for about two hrs. Roof ac blowing out at about 69-70 degs. Should it be blowing colder? Thanks Gary

The 20°+ differential is very good. As the interior cools down the differential will stay at 20+ and continue until you hit the thermostat temp.

Of course, the key is, is the AC capable of keeping up with the interior heating from outside.