10 September 2013

Swamp cooler review

Well, it seems summer has ended and autumn has begun. I've waited this long to mention how our swamp cooler was working, to make sure I could objectively review it's performance.

The verdict?

The swamp cooler has one flaw: it's too cold.

If you think that sounds like a glowing endorsement, that's because it is. I've read many opinions on swamp coolers online, and many of them are quite negative. They make your house soggy, some say. It can't compare to the performance of refrigerated central A/C, say others.

Now, I am admittedly biased since I spent many hours and dollars installing mine, so I'm liable to suffer from "sour grapes" syndrome -- I have a lot invested in my swamp cooler, so I would look foolish if it turned out to suck, and I don't want to look foolish. So, I offer the following objective observations:

The performance of a swamp cooler is directly related to outdoor humidity.

The relative humidity in Idaho is typically too high for good swamp cooler performance at night and in the morning. A swamper might only achieve a 5-10° drop in air temperature. But, outside air temperatures -- even in the peak of summer in of July/August -- often fall to 60-65° at night.

The relative humidity in Idaho is typically low enough for an evaporative 20 to 25° air temperature drop the afternoon and evening, when outside temperatures are around 90°.

When outside temperatures rise above 90°, relative humidity drops proportionally and the swamper achieves a 30 to 32° temperature drop.

What does all this mean, qualitatively? When it's cool outside at night, you only need a 10° temperature drop to make the house downright chilly. When it's 90-95° out, you only need a 20-25° degree drop to make the house a lovely 70°. And when it passes 100°, you still get 70° air coming out of the swamper.

In short, it works, and works well.

In fact, on many occasions, it works too well, outputting 65° air and anyone in the family room has to put on a blanket. We could turn the cooler off when this happens, but it's a hassle to go turn the cooler on and off all the time. A thermostat would solve this, but more on that later.

How about humidity?

Well, as I mentioned, Idaho is very dry ("semi-arid", whatever. Locals call it a desert). Many of our family members suffer from dry skin (elbows, knees) so the added humidity is very welcome. Our house has never gotten soggy because we open a few windows halfway, on the far side of the house. Exhaust air is essential for swamp cooler effectiveness! If you keep the windows shut, all you get is wet with no cooling.

Table salt does not clump. Doors do not stick. Furniture does not warp.

Ah, but what about the smell? My answer: what smell?

When our pads were new, they smelled wonderful (I love the smell of aspen). Sadly, this only lasted a month or so. After that, nothing. I have installed a "bleed kit" that constantly removes a trickle of water from the cooler whenever it is running, which brings in fresh water. This means the water is not in the cooler long enough to spawn life forms. Also, each night I run the cooler on "vent only" (the water pump is shut off) which allows the pads to dry. Bacteria and mold have a real hard time growing on dry pads.

But you say, the window thing is an issue: can't leave it running when you're not home (open windows being an invitation to burglars) and it's a pain to keep opening and closing them all the time. Well, this is true.

The solution is up-ducts in the ceiling of each room. These automatically open when you switch the swamp cooler on and exhaust air into the attic (thus cooling the hottest part of the house, killing two cooling birds with one stone). I have some up-ducts, but haven't installed them yet. Maybe next year.

The great thing about up-ducts is you can put a thermostat on your cooler and at that point, it's just like central refrigerated A/C -- set it and forget it, it takes care of itself. I should have that ready to go by next summer too, soon as the up-ducts go in.

At this point, I'm laughing all the way to the bank. At the peak of summer this year, our electric bill was less than $70 (and that includes a lot of irrigation water pumping). Electricity is cheap in Idaho, but from what I understand, most Idahoans pay $100-$150 a month to cool a 1,700sqft house. So the savings are definitely significant.

And while the cooler cost quite a bit more than I expected -- closer to $1,500 -- that's still a fraction of the price of central refrigerated A/C, and I can fix it myself with a screwdriver if it ever breaks. Try asking an A/C tech how much it costs to replace a coil or compressor, and get ready for sticker shock. Even the diagnosis for A/C is typically $100, whereas I can fix pretty much any part on my swamper for less than $100. And I can do it the same day and not wait weeks for the tech to fit me into his schedule.

Swamp coolers are useless in humid environments -- so they are, admittedly, pointless in much of the US. But, in the arid parts of California, east Oregon, east Washington, Utah, Colorado, Nevada, and New Mexico... they rock.

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