swamp cooler

[pianotuna]

Hi all,

I purchased a swamp cooler and today ran it for the first time.

The RV had been sitting in sun all day long with the fantastic fan on high, with the rear roof vent open. Temperature outside reached 29 C (84 f). Interior of the RV was at 31 C (88 f) and was heat soaked at that temperature. Humidity inside was 33% Time was 4 p.m.

I filled the unit with water and turned the fan on high. The output air fell fairly quickly to 26.1 C (79 f). Humidity level of output was 57%

After one hour of operation the swamp cooler had lowered the temperature in the RV to 30 C (86 f) and humidity in the RV had risen to 40%.

I left the unit running until 10 p.m. When the temperature outside reached 26 C (79 f) I opened the roof vents and turned on the fantastic fan on high.

The swamp cooler output was at least 3 C (5.4 f) lower than the temperature inside the RV. Output near the end was at 66% RH at 22.5 c (72.5 f). RV was about 52% RH at 26 c (79 f).

It is now 10:30 p.m. Fantastic fan is running on low, temperature is 25 C (77 f) and humidity is 51%. Ambient temperature is 19.9 C (67.8 f)

The cooler draws 11 watts on high fan, with pump and louvers active. During the 6 hour run it used approximately 2 liters of water.

Tomorrow I will attempt to run the swamp cooler with the roof vents closed to see if it can keep the temperature from spiraling up and heat soaking the RV.

It was nice to have the air from the unit blowing on me and made the 31 C (88 f) much more bearable.

[pianotuna]

Hi Phil and Rick,

I am urban docking without a generator because a weld failed.

It appears I can be comfortable up to 32 C (90 f) with the swamp cooler blowing on me.

It seemed to work best when I left the roof vents open with the fantastic fan on high. It was much more comfortable that just a fan.

Humidity today was 55%.

I'm now parked at a friends home who does have a 50 amp plug so tomorrow, I'll be using the swamp cooler in conjunction with the air conditioner to see if it helps in the cooling process. Humidity in the RV is 33% and temperature is 28.5 c (83.3 f). The air has been on for about one hour and the RV started at 31 c (87.8 c). The high for the day was
27 C (80.6)

I've had to add the autoformer to support the voltage.

pnichols wrote:
Don ... I'm scratching my head a bit.

Why are you trying to use a swamp cooler in Canada? Isn't average humidity there on the high side for efficient use of one?

(Or are you somewhere else trying to use it?)

[Rick_Jay]

Don,

I won't dispute your numbers as I believe you seem to be pretty objective in your statements. I enjoyed reading them.

However, when you compare the amount of cooling the swamp cooler gave in a day compared to the cooling an A/C gives in an hour, it's also important to remember the physiological effects of humidity and our body's ability to give off heat.

The swamp coolers generally raise the humidity of the air while lowering it's temperature. A traditional A/C not only cools the air drastically, but LOWERS the humidity level of that air as well. So the cool, DRY air ASSISTS the body in it's own cooling process. Albeit at the expensive of greater energy usage and initial cost.

The old "It's not the heat it's the humidity." saying sums that up. If your body can't rid itself of heat through the process of the evaporation of sweat, the perception to the individual is that it's warm/hot.

The swamp coolers can be effective in select applications under very specific circumstances, but they really can't be compared to a refrigerant based A/C unit.

Thanks again for the informative posts and discussions.

~Rick

[pnichols]

Don ... I'm scratching my head a bit.

Why are you trying to use a swamp cooler in Canada? Isn't average humidity there on the high side for efficient use of one?

(Or are you somewhere else trying to use it?)

[pianotuna]

For once I found something useful on facebook.

"Evaporating one pound (about a pint) of water absorbs 970 BTUs of heat and drops the temperature of the air it evaporates into. 12,000 BTU's equals one "ton" of air conditioning. Most RV AC units are either 13,500 or 15,000 BTU's per hour.The problem is that water evaporative cooling works best in hot dry air, and hardly does anything in hot humid air. So they are great in the arid areas like the southwest, but not so good in the humid areas like the southeast."

Yesterday the cooler used about 13 lbs of water over a time frame of 8 hours--so it removed about 12000 btu's or as much heat as running the roof air for nearly an hour.

I had re-positioned it to draw hot air from the glass of the window beside the dinette.

[imgoin4it]

Best way coolers work is, if possible, have cooler intake air from warm or sunny side. Let some of the exhaust air exit where you want to to cool. Ie if cooler taking air in from middle of RV let some exhaust in each end of the RV.. if you want just center to cool let intake be from one side and exhaust out the other. You need one square foot of exhaust opening for every 1000 cfm of intake are, or fraction there of. I would never run acnd and cooler at same time when you are exhausting air like you must to get max cooling avail from a cooler. Kind of like trying to cool the great outdoor.

[pianotuna]

I goofed.

The fan speed was set to medium not to high. I thought it was a 3 speed. So wattage draw on Max fan with pump and louvers active is 32 watts not 20.

Time is 11 a.m. on June 24th

I have moved the cooler so that the air intake is next to the dinette window (east). That particular surface is at 36 c (96.8 f) when the ambient outdoors is only 22.3 c (72.1 f) humidity 71%

The interior of the RV is 25 c (77 f) humidity 57%

Output at the new higher fan speed is currently 24 c (75.2 f) humidity 71%. Input air is considerably hotter.

I'm leaving a West window open about 8" x 6" with the roof vents open and fantastic fan on low. I tried it first without the fan hoping for a chimney effect but it doesn't "fill the bill".

north wall 28.7 c (83.6 f)

east wall 30.1 c (86.2 f)

south wall 28.4 c (83.1 f)

west wall 28.4 c (83.1 f)

[pianotuna]

Hi wa8yxm,

Nice idea on the swamp plus roof air. I'll try that sometime.

In humid weather when I have LOTS of power I've been known to run a small heater to force the air conditioner to remove more moisture. It gets rid of the cold clammy feeling.

At this moment I'm at a friends home who has ancient wiring. They have had problems before (fire in a outlet), so I'm extremely reluctant to use the auto former to keep the voltage up.

[wa8yxm]

Using both a Swamp Cooler and a A/C.. the swamp cooler makes the air more humid, but cooler. the A/C adds additional cooling and removes the excess humidity.

[mike-s]

As it gets more humid, you feel warmer. That's called a heat index - it tells you how warm it feels, which is different than the temperature. There are calculators which make it easy to figure out. I just showed and compared the results based on what you reported. e.g. 88 degrees @ 33% RH = 86 degrees (heat index).

[pianotuna]

Hi mike-s,

Thanks--but I don't understand the numbers you have drawn from my data.

I was able to find out that outdoor humidity at the time I was testing was about 40% RH

The unit is intended for 100 square feet--probably the interior of the class C is double that number. The rv was heat soaked, too, making it quite hard for the cooler to make much difference.

However, initially there was a drop from 31 c (88 f) (input) to 26 c (79 f) (output).

[mike-s]

I don't see where it's doing much. These are the heat indexes, calculated from the OP. It would be useful to know the outside RH, because that normally goes up as temp goes down. But the point is, swamp coolers make it more humid, so you really do need to adjust everything to the associated heat index to get a true feel for their effectiveness.

88/33=86 outside temp 84, 2 degree differential

86/40=85 after 1 hour

79/52=80 after 6 hours. outside 79 - 1 degree differential, not much different than starting

77/51=77 outside 68, time to open all the windows and crank the exhaust fans.

[pianotuna]

Hi MrWizard,

I'll check it with my watt meter. Read 12 watts--but KAW now says 20 watts. Owners manual says 60 watts.

https://www.sylvane.com/media/documents/products/honeywell-cs071ae-evaporative-cooler-owner%27s-manu...

MrWizard wrote:
11 watts ? seems awful small load

i have a 12inch oscillating fan running and its .24va aka 28w at 115v

that cooler must have a very small blower ?

can you check it besides using the KAW

[pianotuna]

Mchero

It still gave a delta T of 2 c (3.6 f). On a miserably hot day.

I agree not an ideal day for testing.

[MrWizard]

11 watts ? seems awful small load

i have a 12inch oscillating fan running and its .24va aka 28w at 115v

that cooler must have a very small blower ?

can you check it besides using the KAW