Evap-cooler VS Central AC when temps are high and dew point low

[CWO4GUNNER]

With all the talk about efficiency why hasten any AC companies found a way to create a system that automatically switches from AC to evaporative cooling automatically since evaporative cooling is 5-10 times more efficient than traditional AC “WHEN” conditions are right. I'm so tired of having to check the local weather forecast for Barometric pressure, Dew Point, and Humidity. Then go through the agony of switching between AC to Evaporative cooling by powering up and down, opening and closing vents and windows and turning water supply on and off.
Living in SW Arizona we have an unusual summer season, always hot but different based on the dew point and humidity. Summers always start out very dry here with a low dew point and humidity around 11%. This is when I turn on my 5000 CFM evaporative whole house cooler. This simple machine comprised of a blower fan and three 24x48 inch intake panels filled with wet straw, is able to make a temperature difference between the intake outside air and exhaust air into my home of approximately 40-50F drop in temperature. Amazing when you consider that the supply water in summer here is between 80-90F and the outside temperature is 100-120F, how is it possible for me get a temperature measurements of 52-58F coming off the exhaust grill inside the house, all while using only a 10th of the energy required to power my central AC unit? I will just say that it is only possible while there is a high pressure atmosphere, low dew point and low humidity can this miracle occur. The high pressure atmosphere acting as the compressor with its high pressure dry air is drawn in and catapulted by the blower fan through the wet straw intake panels acting as an evaporator. The high pressure dry air colliding with the water molecules respond like a refrigerant and undergo a rapid change of state from a liquid to a high volume gas resulting in a rapid temperature drop within and exiting the evaporative cooler exhaust vent. This happens according to Boyle's Law PV=K, where P is the pressure of the gas, V is the volume of the gas, and k is the temperature.
Only one big problem! As soon as monsoon season hits in SW Arizona where the atmospheric pressure drops (no compressor), the dew point rises, and humidity increases the effect of cooling drastically diminishes. With almost no change of state of the water inside the evaporative cooler from a liquid to a gas, Boyle's Law PV=K almost stops. Because there is almost no gas pressure (P), almost no gas volume (V), and almost no temperature change (K).

 

[Syberia]

Is it really that hard to turn on/off the swamp cooler and open/close a window or two? I leave the water supply to mine on all the time, the float valve only opens when it's running.

Such a system as you're describing it would be prohibitively expensive with all the sensors and electronics it would require, not to mention most a/c systems are whole-house affairs while most swamp coolers go through a window or wall and have their own set of controls.

IMO, you're overthinking it. If it's monsoon season, don't use the swamp cooler.

 

[CWO4GUNNER]

The reason why I ask is that I was told a split-system attic air handler with evap-cooler once existed. My late HVAC instructor told a story of a company back in the day like 30 years ago who had sold such a system that used a large vacuum operated devertion dampner pwered off the blower intake side and like on a car AC that open or close deverting return air from either the conditioned space or from an evaporative cooler inside the attic next to the air handler. Also a solonoid would unlock ceiling vents which then operated by supply air pressure and gravity. Once switch back over to AC, again the blower intake vacuum at the fan would move the large dampner cutting off supply air from the adjacent evaporative cooler to return air circuit. Then blower would stop momentarily allowing all ceiling vents to the hot attic to drop locked by solinoid and blower would restart AC. The blower powered both AC supply air and evap cooler box. But even though they were reliable and simple, no one hardly bought them back then because it cost extra (no more then a separate evap) and energy was way cheap back then so they stop making them. But today it would be ideal hear in the Southwest. I believe my teacher said it was a Carrier design.

 

[pseudorealityx]

Various guesses...

1) Locations where an EVAP cooler works are limited. Relatively small market.
2) For a lot of those locations, water is a limited resource, and likely expensive.
3) Cost/size/complexity
4) You would need a comparative ethalpy sensor as well as a dry bulb sensor to determine your control sequence, which adds cost.
5) DX cooling efficiency is a lot better than it was in the 1970's, where as evap cooling really hasn't improved much.

 

[CWO4GUNNER]

I plan to try and automate my setup once I replace my old Goodman 9 seer ducted split system with mini-split ductless systems. quite easy actually by just using wifi power switches to the AC and evap-cooler connected to the network. A program will monitor local weather so that when the humidity gets above 18% the evap-cooler powers down and the AC's power up automatically. The old centralize vents and duct work will be retrofitted to provide dispersed Evap-cooler exhaust air to a centralized point in the attic where it will be vented outside.

 

[EOC_Jason]

I would kill for 18% humidity.... Heck, even 50% humidity...

Imagine having 90%+ for 3 months or more... Welcome to Houston!

 

[TheEquineFencer]

I would kill for 18% humidity.... Heck, even 50% humidity...

Imagine having 90%+ for 3 months or more... Welcome to Houston!

Move to North Carolina if you want high heat and humidity, the only place I know with more is right off the coast here, the ocean.

 

[CWO4GUNNER]

I know, my last tour of duty 2000-20004 was Portsmouth VA. No evaporative cooler would ever work in that place. I really wanted to retire there and had a great house with an awesome 5 ton Trane unit, but outside I just couldn't take the humidity, junebugs, and mosquitoes. Anyway SW Arizona is so dry about 5-10% 10 months out of the year and the Evap-cooler works as good as any packaged unit AC and cost a fraction to operate, but when monsoon season hits humidity jumps as high as 35% and the evap-cooler is useless.

My point is that if you live in a dry climate, a Evap-cooler not only outperforms the highest seer rated AC unit at a fraction of investment cost $500/1600sf capacity, but also extends the life of your AC unit and offsets high repair and maintenance cost. And of course nothing is easier to DIY install than a whole house Evap-cooler.

 

[Falcon67]

Move to North Carolina if you want high heat and humidity, the only place I know with more is right off the coast here, the ocean.

Houston got you beat, trust me. People make a living blasting moss and algae off buildings and driveways. You can run from Houston the The Big Easy and it feels like you're in the same town.

Evap coolers work like gangbusters when the air is dry. My wife is from Albuquerque and I've felt it (What? That's not AC?!). BUT - you can't count on low humidity numbers unless you live in Death Valley.

 

[CWO4GUNNER]

We have enough of a dry season here in SW Arizona that I maintain a new spare 5000 cfm window unit to back up the AC's in my rental units. One tenant asked me why I don't just let them a yellow page tech. I tell them that its my choice and I'm the tech. But if they would feel more comfortable with the men in the little white vans, I will release them from renewing the lease when it due so the can rent from an agency that uses them after waiting 2 weeks. Lol

 

[AZhitman]

Gunner, I'm over in Surprise, and considering a large portable unit for my new build... I have a 5-ton Trane central AC unit going in, so basically, I want the evap unit just for knocking the temp down before kicking on the AC.

Where would you recommend me looking for one? I'm thinking I'll be ready to get it within the next 6 weeks.

Thanks in advance!

 

[CWO4GUNNER]

You smart for realizing that turning on an AC unit on a very hot structure known as a "hot pulldown is very hard on a system and it happens here allot with snowbirds returning to their 2nd homes here mid summer. A swamp cooler can not only save money during the dry season but knock down those high temps in structure far faster then AC and far cheaper in terms of energy and AC wear/tear. But obviously not everyone agrees depending on their motivating factors $$.

To answer your question I researched them all and this window unit the largest available manufactured in Phoenix, to be so effective in cooling my entire 1610 SF home plus 576 SF garage that I ordered I picked up a spare at ACE to have on hand for my rentals in case of AC delayed repair.

The Brisa 501 http://www.evapcool.com/frigiking-aspen/aspen-specialty/brisa-window-coolers/

 

[CWO4GUNNER]

Also here http://m.homedepot.com/p/Brisa-5000...r-for-1600-sq-ft-with-Motor-BW5002/204700100/

 

[CWO4GUNNER]

Math wise, my 16 seer runs much cheaper than my swamp did.
Nothing to maintain.
Does not humidity load the house on a day the weather turns.

Sometimes comfort outweighs a thirty dollar a year (or whatever amount) differential in price.

You told us the math and science, now tell us in dollars.

Perhaps where you live, but here in SW Arizona where dry season demands humidity for comfort, the benefits and savings atr unequivocal...

 

[AZhitman]

I like that Brisa unit. I'm wondering, if I run soft water to it, and use the cartridge filter, if it'll make a mess of my space (as far as excessive humidity and "fallout").

Seems to me it'd be a good way to get the garage from 100* down to 85* before turning on the central air.

 

[CWO4GUNNER]

I like that Brisa unit. I'm wondering, if I run soft water to it, and use the cartridge filter, if it'll make a mess of my space (as far as excessive humidity and "fallout").Seems to me it'd be a good way to get the garage from 100* down to 85* before turning on the central air.

When it comes to maintaining, like anything else you want to follow the instruction, edprcially safety, lubeing, cleaning. Having said that we have the hardest drinking watet (mountain mineral run-off) in the USA about 800 PPM.

As fat as application and effectiveness, my presumptuous critics have a point albeit misdirected at me...if you don't live in a dry climate or have a dry season where humidity is almost necessary (not above 25% humidity) your not going to get "better than AC results" across the board. However if you have extended periods of 5-15% humidity, the results are awesome.

 

[AZhitman]

Well, I'm in the Phoenix area, so I'm not terribly concerned with the critics...

Humidity is NEVER "necessary" when you're restoring antique cars, especially classic Japanese tin.

We'll be using well water, run through a softener, and then through the cartridge filter. Hoping it will accomplish my goal of knocking down the heat load before the AC takes over.

 

[CWO4GUNNER]

If your just going to use it to cool the garage for 20 minutes from 100F to 85F before turning on the AC, you can probably get away with a portable inside cooler unit for like $50 as long as humidity inside is also low. But if your garage is well insulated and your talking pre-AC temps of only 85F, there is no need, the AC can handle it especially if your planing to use AC exclusively anyway why go through the agony.

 

[AZhitman]

Makes sense. I suppose I'll wait until the summer and get a feel for where we're at and what kind of heat loads I'm dealing with.