Water Sprinkler on the Roof, Fact or Fantasy

I am still on the fence about replacing my air conditioning. I'm not convinced a new one is going to cool any better. Funding is tight, so I am really hoping this old one will hold up a while longer.

Today I was at $5 coupon day at Dollar General. They had assorted water sprinklers.  I chose the cheap one for $2 which was shaped like a doughnut and spits out liberally depending on the water pressure applied.

Now I am experimenting with the sprinkler on the roof during a hot day. The run off isn't that much and not a problem for the lay of the land.

Time will tell if this helps or just another urban myth.

If anything it will water the trees for bigger better shade in years to come.  ;D

While others suggested this when I was posting about my AC acting up before I moved, I've yet to hear from anyone who has actually done this. By the way, after I moved 25 miles, the AC stopped tripping breakers repeatedly.

Yes, I have permission to use the water. They said "Do whatever you need to do to stay cool." 

Besides I am normally so miserly with water due to my past life at sea and on far flung islands, that I am still probably using a lot less weekly than most people use taking a personal shower. It was fun setting up the sprinkler and getting all wet too.

Now I have a little yard toy to play with when I am not cooling the roof.  ;D

I didn't get the sprinkler up on the roof until late in the day, but already the inside temperature is slowly dropping faster than the outside.

Watering the roof can make a difference in the inside temperature.  What it will stop is the radiant heat coming down from the ceiling.  Most RVs are a bit skimpy on insulation, so lowering the temperature of the outside skin even 20-30 degrees will be felt in the interior.

Be aware that as the water evaporates off the roof it will leave behind any minerals contained in the water.  Make sure you have enough flow that they are carried away in the runoff and do not just sit and build up on your roof surface.

The evaporation of water (turning it from a liquid to a gas) actually requires quite a bit of energy (the so-called heat of vaporization).  Although some of that energy will be supplied directly from the sun shining on the roof, quite a bit of it will come from the roof that the water is in contact with.  So the roof will be cooled by the evaporating water the same way your body is cooled by sweating and for the same reason that a "mister" makes you feel cooler on a hot day.  If you can keep the roof wet continuously you should see a noticeable effect.

Here is a little idea that may help you.... just kidding of course.

The sprinkler must be on the ground, I think.

which breakers were tripping?

Just keep an eye peeled for leaks and enjoy the cooler temps.

Today I put the sprinkler on the roof about 130pm when I was ready to go inside. It was 72 inside and 88 outside. I should have put it up sooner. Oops.

3pm it is 92 outside and 75 inside.  All but one shade is open, cause I am tired and forgot to close a few. Now I will close off guest loft, should have done that this morning. I forget more than I remember.

I just have a trickle of water running on roof for now. Not sure this is making much difference, or maybe I need to crank up the water to spread it around more.

Water here is pretty soft so I don't think too many minerals in it. I forget when I first get here (after Florida winters of super hard water) and use too much soap then it take forever to rinse it out again.

Tripping breakers seem to be a mute point at this  new location. I tripped it twice in two weeks. First time was AC only, I unplugged other things, then turned it back on, no problems.

Other time I tripped big breaker outside, but OOPS I had too much running at once. So it was clearly user error. I was washing clothes, microwaving something and running AC plus the fridge and laptops and hot water all plugged in. The I turned on 800watt vacuum cleaner and OOPS. I plain forgot but I know that is too much.

Usually when I am running laundry washer I don't microwave or make coffee. 

Because it's summer, I now try to do my laundry early in the morning when the AC isn't under heavy load and I am not likely to need other stuff. It's a compact washer, so I do more loads than at a laundry center with regulation sized washer, but I just love being able to stay home and wash. Besides my 6 month workamping does not have laundry anywhere nearby.

I am with a different power company since I moved too. I think at the former place, I was having brown outs in the afternoon which might be why my AC was putting up such a fuss too.

I wish the RV builders would be a bit more thrifty and give us double paned windows with mini blinds between the windows and a bit more insulation. I don't like their idea of a lot less windows. I just refuse to live in a cave. I need my windows.

Well, I guess I need to be a bit more organized about this sprinkler on the roof to see if it really helps or not. Time will tell...

Have you ever had anyone clean the condenser coil on your roof top unit. These get a tremendous dirt buildup on the coil, which greatly reduces the efficiency of your AC. It's easy if you're not afraid to get on the roof.

There are usually four screws that hold the cover on the AC. Take them out and lift the cover off. You will see a bunch of copper tubing that is running back and forth in some aluminum finns. Get some good industrial cleaner and spray the entire coil pack, trying to get as much penetration as you can in the finns. Let it sit for 15-20 minutes then hose it off with lots of excess water.  You'll be amazed at the dirt that comes out. This is the one item that almost everyone forgets and it makes a HUGH difference in your AC efficiency and performance.

sounds like you have solved your problem with the move.

When using the sprinkler, be aware that if you are in a hard water area, you will have streaks and deposits of hardness (CaC03)  appearing on your roof and the sides of the RV where the water is running off.

Chet18013 said:

Have you ever had anyone clean the condenser coil on your roof top unit. These get a tremendous dirt buildup on the coil, which greatly reduces the efficiency of your AC. It's easy if you're not afraid to get on the roof.

Click to expand...

I was thinking the same thing.  Depending on how long since it's been cleaned, there could be years of dust, pollen, general road grime, bugs, whatever...

Could be the compressor is working a tad harder due to inadequate air flow through the condenser fins.  If the case, a cheap and easy fix.  And good preventative maintenance for optimum efficiency.  Could be also the start/run capacitors in the AC unit are getting tired due to age.