Too much humidity from my swamp cooler

• posted on September 13, 2007, 8:48 pm
I think I got too much swamp cooler for my home (in Denver, CO). It's a nice, new pro unit and very efficient. Problem is that even on low power, to get the house down in the 72-73F range, the humidity it's putting into my home is an issue especially for all the guitars in my basement. It's corroding the strings and hardware on the electrics plus its wreaking havoc on the wood (which is the worse of the two issues. I'm coming up on winter so I'll be switching to hot water heat which doesn't introduce that kind of humidity, but for the next season of cooling, has anyone run a dehumidifier to combat the excess humidity a swamp cooler was introducing? If so, how did it work?
Thank you,
Matt
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• posted on September 13, 2007, 9:43 pm
( x posted to sci.engr.heat-vent-ac for Nick )
On Thu, 13 Sep 2007 13:48:09 -0700, Mtmartin71

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• posted on September 14, 2007, 10:20 am
Thank you Paul...

You might build a box around it with a vent to let indoor air flow through the pads and back into the house with a 73 F cooler thermostat and use an exhaust fan with a 50% humidistat.
But with an average daily max 88.2 F and an average humidity ratio wo = 0.0090 pounds of water per pound of dry air (Boulder in July) and Pi = 0.5e^(17.863-9621/(460+73)) = 0.414 "Hg and wi = 0.62198/(29.921/Pi-1) = .0087, swamp cooling won't work, since wi is less than wo. You might air condition instead.
Or change the setpoints to 80 F and 55% (the upper right corner of the ASHRAE comfort zone), with wi = 0.0120 and evaporate P pounds of water per hour and exhaust C cfm for Q Btu/h of net cooling, P = 60C0.075(wi-wo), ie C = 74.07P, and 1000P = Q + (88.2-80)C = Q + 607P, ie P = 0.0025Q and C = 0.19Q. Q = 24K Btu/h makes P = 60 lb/h and C = 4528 cfm (wow.)
Or turn off the cooler and store coolth in the thermal mass of the house when the outdoor temp is greater than 73.5 (the 24-hour average temp), which makes P = 0.00068Q and C = 0.05Q, eg P = 16 lb/h and C = 1200 cfm, max.
Or forget the cooler and ventilate the house with lots of night air (with a 58.6 F average daily min) and button it up during the day.
Airsealing helps. How about a blower door test?
Nick
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• posted on September 16, 2007, 12:50 am
On Sep 14, 5:20 am, snipped-for-privacy@ece.villanova.edu wrote:

Mr Martin
You are in a high altitude location. Nick loves to crunch numbers and sounds impressive but evaporative cooling is beyond the limit of his comprehension skills. He is actually not as stupid as he sounds, he just needs to swallow his pride and realize the theories he keeps trying to push are incorrectly applied.
This is evident by the fact that he runs a lot of numbers based on sea level atmospheric pressure, he likes to use 29.92 inches of Mercury in his calcs. He also looks at average temperatures everytime and this always leads him astray. The man is simply the world's oldest electrical engineer in training and has no real business giving advice in the field of HVAC.
Typical worst case air conditionijng design conditions for high altitude Denver are a dry bulb temperature of about 91.2F with a coincidental wet bulb temperature of about 60.6 F. A realistic supply air temperature out of an evaporative cooler could be about 67 dry bulb with the same wet bulb of 60.6 F.
If you were to keep your home about 78F, I doubt your internal RH would be much above 50F and this should be fine for wood products.
Trying to use a swamp cooler to maintain 72F is going to drive up the relative humidity up past 60 percent possibly around 70% and this will make the wood swell and is just asking for mold.
You could also look at the Coolerado products, they give the benfit of evaporative cooling without adding the humidity to the home.
Therefore Nicks advice of raising the set point was good, and if you kept your place around 78F, most likely your wood would not be swelling.
If you are insisting on the cool 72F temperature, then you should be using DX AC and not evaporative cooling.So this was the only other valid thing Nick had to say, consider conventional air conditioning.
Now concerning Nicks advice about applying evaporative cooling to return air. In the winter time, there will be some low RH in your place and this likes to make wood dry out and crack. In thgis situation you would need to humidify your home, and this is when you apply evaporative cooling techniques directly to the return air. Except you are not cooling per se, you are humidifying which is exactly what applying evaporative cooling to room air is.
Nick also promotes schemes that bring uncondituioned outside air into the space and this is yet another inherent flaw in his thinking.
To use evaporative cooling, you humidify hot dry outside air so that it is cooler than the temperature you want to maintain inside and you pressurize your home with this air. You need paths for this air pressure in the home to relieve itself from to prevent driving up the interior RH.
So take everything Nick has to say with a grain of salt and do not be impressed with the fact that he has to derive Pi when an an answer is a simple yes or no.
Denver also has a worst case humidity design level of a dewpoint of 61.2F and a coincidental dry bulb temperature of 68.7F. Situations like thios could driuve your indoor RH up around 80% and in these cases it would not hurt to have a cheap little Kenmore dehumidifier on hand, to protect your guitar collection.
If you try and keep your indoor set point up around 78F, I think your guitars will fair much better and should avoid the situation of running a swamp cooler and a dehumidifier at the same time.
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• posted on September 16, 2007, 9:18 am

I'd say the same about you, when it comes to evaporative cooling :-)

After lots of net.discussion, it looks like you'll never understand how that works. You might, in person. You might come to the Pennsylvania Renewable Energy Festival next week, where I'll be talking about how to heat a house with an auto radiator: http://www.paenergyfest.com .
Nick
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• posted on September 16, 2007, 6:29 pm
Mike,
My son and I are going on Sunday, when are you speaking.
--
Bob Pietrangelo
snipped-for-privacy@comcast.net (home)
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• posted on September 16, 2007, 7:09 pm

http://www.paenergyfest.com .
At 2:30 on Saturday in the yellow flag tent (1 of 8). PhD Nathan Hurst will be talking about his Mazda radiator solar heating experiments in Australia at 3:30 on Sunday in the red flag tent (a late program change.) PhD Rich Komp will be talking about energy-efficient food storage at 3:30 on Saturday in the blue flag tent and new developments in photovoltaics at 4:30 on Sunday in the white flag tent. We'll be at an "ask the engineer" table at other times. About 6,000 people came the first year and 12,000 last year. Will there be 24,000 this year? :-)
BTW, it would simplify the damper arrangements if we could pull hot sunspace air through the radiator with its fans during the day to heat water and push house air through it to heat the house at night. Does anyone know if late model Japanese radiators (eg my \$35 '95 Mitsubishi 2.0 Eclipse) 12V fans have brushes that are slanted in the normal rotation direction in a way that lets the commutators quickly grind them up in reverse?
Thanks,
Nick