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#1
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Evaporative cooler question
I live in Las Vegas. We use evaporative coolers here. I want to add a
5,000 cfm for one side of my house. My questions a Is there a special ducting that is used for this and is different than AC ducting? Do I need to run ducts to all the areas, or would just ducting into the largest room do it? (The kitchen, living room, and family room are all open to each other.) I have to make a stand for this to go in through the attic. Making a hole in a wall is not an option. TIA Steve |
#2
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yes. they are typically bigger since you're moving a lot more air. you need
to talk to someone to design the ducting issues you're going to encounter. "SteveB" wrote in message news:vvfDd.51954$Cl3.7522@fed1read03... I live in Las Vegas. We use evaporative coolers here. I want to add a 5,000 cfm for one side of my house. My questions a Is there a special ducting that is used for this and is different than AC ducting? Do I need to run ducts to all the areas, or would just ducting into the largest room do it? (The kitchen, living room, and family room are all open to each other.) I have to make a stand for this to go in through the attic. Making a hole in a wall is not an option. TIA Steve |
#3
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"SteveB" wrote in message news:vvfDd.51954$Cl3.7522@fed1read03... I live in Las Vegas. We use evaporative coolers here. I want to add a 5,000 cfm for one side of my house. My questions a Is there a special ducting that is used for this and is different than AC ducting? Do I need to run ducts to all the areas, or would just ducting into the largest room do it? (The kitchen, living room, and family room are all open to each other.) I have to make a stand for this to go in through the attic. Making a hole in a wall is not an option. TIA Steve Yes, the ducting is larger than used for AC. To one room will be adequate. Much depends on where the air will be exhausted. There is lots of information on the web: Do a net search for evaporative cooler duct. http://hem.dis.anl.gov/eehem/96/960511.html |
#4
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5000 cfm is a very large amount of airflow for even a large residence,
so, you will need to take into account proper duct sizing and ways to reduce air noise levels. |
#5
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"Hello Friend" wrote in message ... 5000 cfm is a very large amount of airflow for even a large residence, so, you will need to take into account proper duct sizing and ways to reduce air noise levels. 5000 cfm is rather small. One source specifies that the unit needs to be sized to supply 2 to 3 cfm for each square foot of floor space. That is 5000 cfm would be adequate for a 666 to 1000 square foot residence. Another method says that to cool a 1500 sq. ft. residence (with 8 ft ceilings) needs 6000 cfm. That is the maximum. Usually I found I have run them at lower speeds. In any case if ducts are used they need to be large. |
#6
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"SteveB" wrote in message news:vvfDd.51954$Cl3.7522@fed1read03... I live in Las Vegas. We use evaporative coolers here. I want to add a 5,000 cfm for one side of my house. My questions a Is there a special ducting that is used for this and is different than AC ducting? Do I need to run ducts to all the areas, or would just ducting into the largest room do it? (The kitchen, living room, and family room are all open to each other.) I have to make a stand for this to go in through the attic. Making a hole in a wall is not an option. TIA Steve Ahhh the ole swamp cooler. aluminum ducting is best, holds up to the moisture better. You'll crap when you see the cost. Sheet metal is ok and used a lot in Phoenix. Plastic ducting is a no-no, can not handle the pressure for long. No fiber ducts and no insulation on the inside. If you do the moisture and dirt in time WILL grow mold. (Did in my first Phoenix home). Trying to cool part of the home is not a good idea unless you have a physical barrier like an outside door between the parts of the home. I had a home with 2 5500 coolers, had to run them both or the home would not cool well. You need ducts to each room just like A/C, only bigger. Install upducts 1 per each 12 square inches of register, cause you need an exhaust from each room especially if you close doors. When I ran a cooler on my last home (6500) mounted on the roof. I had a damper that prevented the cooler air from going into my a/c- gas furnace. Since the air handler was in the hall closet I used it as the up duct for the whole house. Really needed one in the kitchen especially when cooking. A 5000 cfm cooler will really only deliver about 4500 cfm, a mere whisper. Bigger is better with coolers. You will need an amp meter to set the unit up the first time. Set the motor to FLA, that is the only way to get close to the advertised air flow. You may have to change pulleys, I have several times. 2 speed motors help a bit in the early cooling season. As well as a t-stat. The stats do not have actual temp settings just numbers 1-5. They do prevent you from waking up and having the house 60 degrees. The stats also have a pre wet timer, helps stop that 120 degree air blast in the beginning. The single pad units are the best performers, 12 inch wet section, there is an 8 inch section as well. Forget about the "pre coolers". Unless they want to give you one. A friend had one and I did not. We would call each other and I was always within a degree of his output temp. A degree is nothing. The precooler was always clogging up and he finally ditched it. A timed dumping pump helps keep them clean. A little more in cost than a regular pump. You will replace the pad every couple of years, $100-200 bucks depending on who you know. Calcium is the killer here, no matter what chemicals you use. I ran my last cooler on soft water. Slowed the calcium down to changing the pads every 3 years. The soft water was an accident. Go with 220v for everything if at all possible. There are lots of places to get motors and pumps on weekends. Coolers are NOT for setting and forgetting. They need to be clean to work. I know you get the same kind of dust storms that we do here in Phoenix. I cleaned mine 3 times a cooling season. I was experimenting with air filtration when I moved. Coolers put a lot of dirt in the home. Now that I am approaching 55 I do not want to get on the roof nor do I want to clean them anymore. Del Web the original Sun City in west Phoenix mounted the a/c and cooler units on the gable ends of the homes. That way they were not on the roof (ambient summer heat) and there was a straight shot into the duct work. Better air flow. Several HVAC companies here sell cooler kits for installing into duct work. Do you have the chain called Evergreen Hardware there? Coolers only work until the dew point reaches 45 degrees, for me it is 40 degrees. It is just to humid after 40. I used to get a couple of months of cooling early in the season and maybe a month on the end. What I saved in electricity was used up in water and maintenance. Water here in the summer time gets pricey. A cooler can go through several hundred gallons a day. I would have 60 dollar electric bills and 80 dollar water bills, a/c cost 150. Good luck to ya. |
#7
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"SQLit" wrote in message news:mIjDd.78924$QR1.55624@fed1read04... "SteveB" wrote in message news:vvfDd.51954$Cl3.7522@fed1read03... I live in Las Vegas. We use evaporative coolers here. I want to add a 5,000 cfm for one side of my house. My questions a Is there a special ducting that is used for this and is different than AC ducting? Do I need to run ducts to all the areas, or would just ducting into the largest room do it? (The kitchen, living room, and family room are all open to each other.) I have to make a stand for this to go in through the attic. Making a hole in a wall is not an option. TIA Steve Ahhh the ole swamp cooler. aluminum ducting is best, holds up to the moisture better. You'll crap when you see the cost. Sheet metal is ok and used a lot in Phoenix. Plastic ducting is a no-no, can not handle the pressure for long. No fiber ducts and no insulation on the inside. If you do the moisture and dirt in time WILL grow mold. (Did in my first Phoenix home). Trying to cool part of the home is not a good idea unless you have a physical barrier like an outside door between the parts of the home. I had a home with 2 5500 coolers, had to run them both or the home would not cool well. You need ducts to each room just like A/C, only bigger. Install upducts 1 per each 12 square inches of register, cause you need an exhaust from each room especially if you close doors. When I ran a cooler on my last home (6500) mounted on the roof. I had a damper that prevented the cooler air from going into my a/c- gas furnace. Since the air handler was in the hall closet I used it as the up duct for the whole house. Really needed one in the kitchen especially when cooking. A 5000 cfm cooler will really only deliver about 4500 cfm, a mere whisper. Bigger is better with coolers. You will need an amp meter to set the unit up the first time. Set the motor to FLA, that is the only way to get close to the advertised air flow. You may have to change pulleys, I have several times. 2 speed motors help a bit in the early cooling season. As well as a t-stat. The stats do not have actual temp settings just numbers 1-5. They do prevent you from waking up and having the house 60 degrees. The stats also have a pre wet timer, helps stop that 120 degree air blast in the beginning. The single pad units are the best performers, 12 inch wet section, there is an 8 inch section as well. Forget about the "pre coolers". Unless they want to give you one. A friend had one and I did not. We would call each other and I was always within a degree of his output temp. A degree is nothing. The precooler was always clogging up and he finally ditched it. A timed dumping pump helps keep them clean. A little more in cost than a regular pump. You will replace the pad every couple of years, $100-200 bucks depending on who you know. Calcium is the killer here, no matter what chemicals you use. I ran my last cooler on soft water. Slowed the calcium down to changing the pads every 3 years. The soft water was an accident. Go with 220v for everything if at all possible. There are lots of places to get motors and pumps on weekends. Coolers are NOT for setting and forgetting. They need to be clean to work. I know you get the same kind of dust storms that we do here in Phoenix. I cleaned mine 3 times a cooling season. I was experimenting with air filtration when I moved. Coolers put a lot of dirt in the home. Now that I am approaching 55 I do not want to get on the roof nor do I want to clean them anymore. Del Web the original Sun City in west Phoenix mounted the a/c and cooler units on the gable ends of the homes. That way they were not on the roof (ambient summer heat) and there was a straight shot into the duct work. Better air flow. Several HVAC companies here sell cooler kits for installing into duct work. Do you have the chain called Evergreen Hardware there? Coolers only work until the dew point reaches 45 degrees, for me it is 40 degrees. It is just to humid after 40. I used to get a couple of months of cooling early in the season and maybe a month on the end. What I saved in electricity was used up in water and maintenance. Water here in the summer time gets pricey. A cooler can go through several hundred gallons a day. I would have 60 dollar electric bills and 80 dollar water bills, a/c cost 150. Good luck to ya. I think you are way off on the water use. They may use a few hundred gallons a month: This study goes along with my experience. (3.5 gallons per hour without a bleed. 10.5 gallons per hour with a bleed). Instead of a bleed I ran a hose down with a faucet on the end so I could dump the reservoir every now and then. I found they became marginal when the humidity level was above 30 to 35%. http://phoenix.gov/WATER/evapcool.html http://www.snwa.com/html/ch_evap_cooler.htm |
#8
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Well, I went to XYZ, Inc, yesterday, and was outfitted immediately. The
counter man was helpful in calculating which CFM I needed, and duct sizing. I called other supply houses, and they treated me like I was intruding. Smartass primadonna HVAC people, I assume. I am calling them XYZ because I want to protect them from any HVAC people who might call them and bitch that they are selling to "citizens." I got a bid from a "friend" who is a licensed HVAC person. 24' of 14" dia. spiral, 8 90 deg. elbows, two 14" cans, and two grates. Two custom made pieces of sheet metal. ................ $3200. I was to provide the swamp cooler and stand. All materials at jobsite, and cleanup by owner. So far, the total is $256 for parts, $550 for cooler, about $30 for stand. All materials are on site at this time, having picked them up yesterday. I estimate it will take two guys two days at tops for installation, and I would estimate we do it in less time. One of them will be me, and one is my hired ex-contractor friend who I pay $25 per hour, so I would estimate that cost at $800 if I were to pay myself. I know my other HVAC "friend" would have hired a $10 (or less) per hour grunt, therefore getting $40 per hour for his side. That leaves $1,564 for what? Some Primadonna HVAC person? I don't think so, Tim. Since this group is alt.home.repair instead of alt.HVACkvetching, I have chosen to post this here as an example of how one can save money getting a job done right, and for about half the cost. Hell, for the $1,600 saved, I could take a hell of a ski trip. Or a cruise. Or just go rent a couple of bimbos and spend a day diving in the hot tub. drool............... OR, I could just buy more tools ................ double drool....................... Figger it out, people. It ain't rocket science. BTW, the original contractor is yet to show up to give his estimate. I will report back if and when he does with his price. Steve |
#9
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SteveB wrote:
I live in Las Vegas. We use evaporative coolers here. I want to add a 5,000 cfm for one side of my house. Wow. I got a bid from a "friend" who is a licensed HVAC person. 24' of 14" dia. spiral... With a 5000cfm/1.07ft^2 = 4677 fpm (54 mph) air velocity? Nick |
#11
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"SteveB" wrote in message news:vvfDd.51954$Cl3.7522@fed1read03... I live in Las Vegas. We use evaporative coolers here. I want to add a 5,000 cfm for one side of my house. My questions a Is there a special ducting that is used for this and is different than AC ducting? Do I need to run ducts to all the areas, or would just ducting into the largest room do it? (The kitchen, living room, and family room are all open to each other.) I have to make a stand for this to go in through the attic. Making a hole in a wall is not an option. TIA Steve Just make sure you treat your water system regularly. Open tanks and Legionaires Disease are very friendly with each other ReRe |
#12
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On Tue, 11 Jan 2005 21:43:03 GMT, "chillermfg"
wrote: "SteveB" wrote in message news:vvfDd.51954$Cl3.7522@fed1read03... I live in Las Vegas. We use evaporative coolers here. I want to add a 5,000 cfm for one side of my house. My questions a Is there a special ducting that is used for this and is different than AC ducting? Do I need to run ducts to all the areas, or would just ducting into the largest room do it? (The kitchen, living room, and family room are all open to each other.) The main difference is that Evap Ducting is usually larger because on a hot day you need to blow a lot of air thru it. If you look at old homes that originally had Evap you generally see ductwork and registers that are larger then you would see on new homes that started out with Central air. If you are adding an Evap to a house that originally had AC you may have a hard time pushing 5000 cfm thru the ductwork and when it comes out the register it will possibly make a lot of "whooshing/whistling" noise. If you try to blow that thru the round plastic flexible tubes used for some central AC you may pop the tubes loose. I have to make a stand for this to go in through the attic. Making a hole in a wall is not an option. TIA Steve Just make sure you treat your water system regularly. Open tanks and Legionaires Disease are very friendly with each other ReRe -- Elbridge Gerry, of Massachusetts: "What, sir, is the use of militia? It is to prevent the establishment of a standing army, the bane of liberty. . . Whenever Government means to invade the rights and liberties of the people, they always attempt to destroy the militia, in order to raise a standing army upon its ruins." -- Debate, U.S. House of Representatives, August 17, 1789 |
#13
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AZGuy wrote:
...If you are adding an Evap to a house that originally had AC you may have a hard time pushing 5000 cfm thru the ductwork Perhaps the OP meant "500 cfm." Nick |
#14
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wrote in message ... AZGuy wrote: ...If you are adding an Evap to a house that originally had AC you may have a hard time pushing 5000 cfm thru the ductwork Perhaps the OP meant "500 cfm." Nick no. evap requires much more air movement than central a/c. 5000 was probably on the low side. |
#15
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Charles Spitzer wrote:
AZGuy wrote: ...If you are adding an Evap to a house that originally had AC you may have a hard time pushing 5000 cfm thru the ductwork Perhaps the OP meant "500 cfm." no. evap requires much more air movement than central a/c. 5000 was probably on the low side. He said he paid $550 for the unit. Bare 5000 cfm blowers cost over $1000. Evaporative cooling can be very efficient with small airflows in a well-insulated airtight house in a dry climate. Nick |
#16
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wrote in message ... Charles Spitzer wrote: AZGuy wrote: ...If you are adding an Evap to a house that originally had AC you may have a hard time pushing 5000 cfm thru the ductwork Perhaps the OP meant "500 cfm." no. evap requires much more air movement than central a/c. 5000 was probably on the low side. He said he paid $550 for the unit. Bare 5000 cfm blowers cost over $1000. Evaporative cooling can be very efficient with small airflows in a well-insulated airtight house in a dry climate. Nick Installed perhaps but a 5000 cfm window mount can be purchased for slightly over $300 from SAMS. |
#17
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Rich wrote:
wrote in message Charles Spitzer wrote: AZGuy wrote: ...If you are adding an Evap to a house that originally had AC you may have a hard time pushing 5000 cfm thru the ductwork Perhaps the OP meant "500 cfm." Still wondering how to push 5000 cfm through a 14" duct (at 54 mph :-) no. evap requires much more air movement than central a/c. 5000 was probably on the low side. He said he paid $550 for the unit. Bare 5000 cfm blowers cost over $1000. Evaporative cooling can be very efficient with small airflows in a well-insulated airtight house in a dry climate. Installed perhaps but a 5000 cfm window mount can be purchased for slightly over $300 from SAMS. Perhaps you are thinking about a 5000 Btu/h window AC. Grainger sells a 7F889 blower that will do 5000 cfm for $1324 in a box, vs installed. It has a 20" wheel and a 1 HP motor and weighs 240 pounds and measures 38"x37"x33", with a 25"x25" air outlet... Nick |
#18
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wrote in message ... Rich wrote: wrote in message Charles Spitzer wrote: AZGuy wrote: ...If you are adding an Evap to a house that originally had AC you may have a hard time pushing 5000 cfm thru the ductwork Perhaps the OP meant "500 cfm." Still wondering how to push 5000 cfm through a 14" duct (at 54 mph :-) no. evap requires much more air movement than central a/c. 5000 was probably on the low side. He said he paid $550 for the unit. Bare 5000 cfm blowers cost over $1000. Evaporative cooling can be very efficient with small airflows in a well-insulated airtight house in a dry climate. Installed perhaps but a 5000 cfm window mount can be purchased for slightly over $300 from SAMS. Perhaps you are thinking about a 5000 Btu/h window AC. Grainger sells a 7F889 blower that will do 5000 cfm for $1324 in a box, vs installed. It has a 20" wheel and a 1 HP motor and weighs 240 pounds and measures 38"x37"x33", with a 25"x25" air outlet... Nick here in phoenix, one can get a cheap rooftop 5000 cfm, with motor, blower, out the door for about $400. http://www.lowes.com/lkn?action=prod...0030386-BD5000 i imagine getting one 2nd hand would be less. getting it installed isn't that much more. the ductwork is a lot more. perhaps you wouldn't sound so pompous if you lived in a place where these were more common. |
#19
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wrote in message ... Rich wrote: wrote in message Charles Spitzer wrote: AZGuy wrote: ...If you are adding an Evap to a house that originally had AC you may have a hard time pushing 5000 cfm thru the ductwork Perhaps the OP meant "500 cfm." Still wondering how to push 5000 cfm through a 14" duct (at 54 mph :-) no. evap requires much more air movement than central a/c. 5000 was probably on the low side. He said he paid $550 for the unit. Bare 5000 cfm blowers cost over $1000. Evaporative cooling can be very efficient with small airflows in a well-insulated airtight house in a dry climate. Installed perhaps but a 5000 cfm window mount can be purchased for slightly over $300 from SAMS. Perhaps you are thinking about a 5000 Btu/h window AC. Grainger sells a 7F889 blower that will do 5000 cfm for $1324 in a box, vs installed. It has a 20" wheel and a 1 HP motor and weighs 240 pounds and measures 38"x37"x33", with a 25"x25" air outlet... Nick http://www.samsclub.com/eclub/main_s...73%20&fid=1S10 The URL is pretty long. If it doesn't work you can go to : http://www.samsclub.com and search on Evaporative Cooler you will see it. Others: http://www.kennspenns.com/phoenix/phx-window.html |
#20
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wrote in message ... Rich wrote: wrote in message Charles Spitzer wrote: AZGuy wrote: ...If you are adding an Evap to a house that originally had AC you may have a hard time pushing 5000 cfm thru the ductwork Perhaps the OP meant "500 cfm." Still wondering how to push 5000 cfm through a 14" duct (at 54 mph :-) That is probably to feed two or more rooms. The outlet of the cooler is probably 18 x 18 inches (324 sq in). Run that into a plenum and then feed two or more of the 14" ducts. Regardless there is still a significant amount of air being moved. That is the whole principal of a swamp cooler. You have to provide adequate exhaust too by keeping windows open. You open windows in rooms you want cooled.. For a single outlet unit such as a window mount it can get downright cold in the room it is installed. Note in the following chart if the humidity is 10% and the outside temperature is 85 degrees the outlet temperature will probably be about 63 degrees. http://kesq.com/Global/story.asp?S=1316062 |
#21
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Rich wrote:
Still wondering how to push 5000 cfm through a 14" duct (at 54 mph :-) That is probably to feed two or more rooms. The outlet of the cooler is probably 18 x 18 inches (324 sq in). Run that into a plenum and then feed two or more of the 14" ducts. I also suspect that swamp cooler cfms are inflated, as fans used to be. Air King's 9166 whole house fan is listed as 8908 cfm in Grainger's 394 catalog, but Air King says it only delivers 3560 under the current test method, which measures the actual cfm flowing through the fan, without adding the room air entrained by that airstream after it leaves the fan. Most of the swamp coolers in Grainger's catalog are now listed with an "industry standard rating" ("a numerical rating for comparing similar models and sizing purposes") instead of "CFM." For instance, their chart says a 5NV70 WisperCool model RW5000 cooler with an "industry standard rating" of 5000 can cool a 1200 ft^2 house in Las Vegas. Regardless there is still a significant amount of air being moved. That is the whole principal of a swamp cooler. You have to provide adequate exhaust too by keeping windows open... Moving lots of air wastes water and electricity. A Las Vegas homeowner might do better with Sam's portable 797895 Arctic Breeze cooler mounted inside a house near an open low window and an exhaust fan in a higher window with a one-way plastic film damper. Turn on the cooler when the house temp reaches 80 F and turn on the exhaust fan when the RH reaches 60% to keep the house air at the upper right corner (80 F and w = 0.012) of the ASHRAE 55-2004 comfort zone. A 1200 ft^2 house with R30 walls and R40 ceiling and 96 ft^2 of R3 windows and 0.2 ACH (I suppose nobody builds houses like that in Las Vegas) would have a thermal conductance of 1200ft^2/R30 for the ceiling + 96/2 for the windows + 1024/30 for the walls + 0.2x1200x8/60 for air leaks, totaling 128 Btu/h-F. July looks like the worst-case month for cooling, when it's 91.1 F over an average day, with an average low and high of 76.2 and 105.9 and humidity ratio w = 0.0066 pounds of water per pound of dry air. Keeping that house 80 F while evaporating P lb/h of water into C cfm of outdoor air means 1000P = (91.1-80)(128+C). P = 60C(0.075)(0.012-0.0066) = 0.0243C makes C = 108 cfm and P = 2.62 lb/h, ie 7.6 gallons per day. If the house has significant thermal mass (eg a floorslab), we can save more water and energy by only running the cooler at night. Why do we need 5000 cfm??? Nick |
#22
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wrote in message ... I also suspect that swamp cooler cfms are inflated, as fans used to be. Like an air conditioner you want to have one rated above what you need. I run mine at the lowest speed most of the time. Only if the humidity rises do I find it necessary to use high speeds. Moving lots of air wastes water and electricity. Why do you say that? They use relatively little water - only that which is evaporated and a bit more if some is bled off. A Las Vegas homeowner might do better with Sam's portable 797895 Arctic Breeze cooler mounted inside a house near an open low window and an exhaust fan in a higher window with a one-way plastic film damper. You can't recycle the air in the house. You have to get rid of the moist air as it will not cool. house temp reaches 80 F and turn on the exhaust fan when the RH reaches 60% to keep the house air at the upper right corner (80 F and w = 0.012) of the ASHRAE 55-2004 comfort zone. Your house would be like a steam bath. The maximum cooling is when the humidity is very low. Once it gets to 30% cooling becomes marginal. Keeping that house 80 F while evaporating P lb/h of water into C cfm of outdoor air means 1000P = (91.1-80)(128+C). P = 60C(0.075)(0.012-0.0066) = 0.0243C makes C = 108 cfm and P = 2.62 lb/h, ie 7.6 gallons per day. If the house has significant thermal mass (eg a floorslab), we can save more water and energy by only running the cooler at night. Why do we need 5000 cfm??? I think you need to live in the South West deserts for a summer and try cooling with a swamp cooler. You soon find out why most houses have refrigeration if they can afford it. |
#23
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On Fri, 14 Jan 2005 23:09:53 GMT, "Rich" wrote:
wrote in message ... I also suspect that swamp cooler cfms are inflated, as fans used to be. Like an air conditioner you want to have one rated above what you need. I run mine at the lowest speed most of the time. Only if the humidity rises do I find it necessary to use high speeds. Moving lots of air wastes water and electricity. Why do you say that? They use relatively little water - only that which is evaporated and a bit more if some is bled off. A Las Vegas homeowner might do better with Sam's portable 797895 Arctic Breeze cooler mounted inside a house near an open low window and an exhaust fan in a higher window with a one-way plastic film damper. You can't recycle the air in the house. You have to get rid of the moist air as it will not cool. house temp reaches 80 F and turn on the exhaust fan when the RH reaches 60% to keep the house air at the upper right corner (80 F and w = 0.012) of the ASHRAE 55-2004 comfort zone. Your house would be like a steam bath. The maximum cooling is when the humidity is very low. Once it gets to 30% cooling becomes marginal. Keeping that house 80 F while evaporating P lb/h of water into C cfm of outdoor air means 1000P = (91.1-80)(128+C). P = 60C(0.075)(0.012-0.0066) = 0.0243C makes C = 108 cfm and P = 2.62 lb/h, ie 7.6 gallons per day. If the house has significant thermal mass (eg a floorslab), we can save more water and energy by only running the cooler at night. Why do we need 5000 cfm??? I think you need to live in the South West deserts for a summer and try cooling with a swamp cooler. You soon find out why most houses have refrigeration if they can afford it. If you insist on continuing to bother Nick with facts and realities, he's gonna have another allergic reaction and swell all up and everything. Nick thinks the range of human comfort is defined by the highest setting available on your refrigerator, and the lowest setting available on your stove. Everything in between can be explained away with his little magic formulas. Paul ( pjm @ pobox . com ) - remove spaces to email me 'Some days, it's just not worth chewing through the restraints.' HVAC/R program for Palm PDA's Free demo now available online http://pmilligan.net/palm/ Free Temperature / Pressure charts for 38 Ref's http://pmilligan.net/pmtherm/ |
#24
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From:
http://www.consumerenergycenter.org/...e_coolers.html "With evaporative cooling, a complete air change in a home occurs every one-to-three minutes. This flow of fresh air means that evaporative coolers can be operated without using the water pump to replace warm stale air with cooler nighttime air, much like a whole house fan does. That's an added benefit." |
#25
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Rich wrote:
Moving lots of air wastes water and electricity. Why do you say that? They use relatively little water - only that which is evaporated and a bit more if some is bled off. "Evaporative cooler water use" by Martin Karpiscak and Mary H. Marion at http://ag.arizona.eduj/pubs/consumer/az9145.pdf cites a survey showing an average water usage of 7.6 gph, which seems like a lot compared to the 7.6 gpd below. And these things have 1/2 to 1 HP motors. A Las Vegas homeowner might do better with Sam's portable 797895 Arctic Breeze cooler mounted inside a house near an open low window and an exhaust fan in a higher window with a one-way plastic film damper. You can't recycle the air in the house. You have to get rid of the moist air as it will not cool. That's what the exhaust fan does, controlling the indoor RH precisely with a humidistat, vs a swamp cooler without a humidistat. Turn on the cooler when the house temp reaches 80 F and turn on the exhaust fan when the RH reaches 60% to keep the house air at the upper right corner (80 F and w = 0.012) of the ASHRAE 55-2004 comfort zone. The 80 F comes from a room temp thermostat. Your house would be like a steam bath. I disagree, as do 21,000 ASHRAE comfort survey participants. The maximum cooling is when the humidity is very low. Once it gets to 30% cooling becomes marginal. You are thinking about the air outside vs inside the house. Keeping that house 80 F while evaporating P lb/h of water into C cfm of outdoor air means 1000P = (91.1-80)(128+C). P = 60C(0.075)(0.012-0.0066) = 0.0243C makes C = 108 cfm and P = 2.62 lb/h, ie 7.6 gallons per day. If the house has significant thermal mass (eg a floorslab), we can save more water and energy by only running the cooler at night. Why do we need 5000 cfm??? Air-leaky houses with no insulation, poor controls, ignorant owners and HVAC criminals? :-) Nick It's a snap to save energy in this country. As soon as more people become involved in the basic math of heat transfer and get a gut-level, as well as intellectual, grasp on how a house works, solution after solution will appear. Tom Smith, 1980 |
#26
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A Las Vegas homeowner might do better with Sam's portable 797895 Arctic
Breeze cooler... Or a soaker hose on a slab and a solenoid valve from an old washing machine and a ceiling fan with a room temp thermostat and an occupancy sensor? :-) Turn on the cooler when the house temp reaches 80 F and turn on the exhaust fan when the RH reaches 60% to keep the house air at the upper right corner (80 F and w = 0.012) of the ASHRAE 55-2004 comfort zone. Herbach and Rademan (800) 848-8001 http://www.herbach.com sell a nice brass $4.95 Navy surplus humidistat, item number TM89HVC5203, with a 20-80% range, a 3-6% differential, and a 7.5A 125V switch that can be wired to open or close on humidity rise. Keeping that house 80 F while evaporating P lb/h of water into C cfm of outdoor air means 1000P = (91.1-80)(128+C). P = 60C(0.075)(0.012-0.0066) = 0.0243C makes C = 108 cfm and P = 2.62 lb/h, ie 7.6 gallons per day. If the house has significant thermal mass (eg a floorslab), we can save more water and energy by only running the cooler at night. A 30'x40' 4" slab has at least 4/12x30x40x25 = 10K Btu/F of capacitance, making RC = C/G = 10K/128 = 78 hours. Outdoor air is about 84 F at night and 99 F for 12 hours per day in Las Vegas in July. If the slab cools to to Tmin by dawn and warms to 80 by dusk, 80 = 99+(Tmin-99)e^-12/78, so Tmin = 77. If 12hx1000P = 12h(84-78.5)(128+C)+(80-77)10K and P = 0.0243C, C = 170 cfm and P = 4.14 lb/h, ie 6 gpd. Nick ...a research study initiated by the Office of Arid Lands Studies at the University of Arizona and the Water Services Department at the City of Phoenix with funding from the Arizona Department of Water Resources monitored evaporative coolers at 46 homes in Phoenix. Preliminary data from this study indicates that water usage... was about 7.6 gallons for each hour that the cooler was operated (4.4 gallons per hour for systems without bleed-off and 10.4 gallons per hour for systems with bleedoff.) from "Evaporative cooler water use" by Martin Karpiscak and Mary H. Marion at http://ag.arizona.eduj/pubs/consumer/az9145.pdf |
#27
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"Evaporative cooler water use" by Martin Karpiscak and Mary H. Marion at
http://ag.arizona.eduj/pubs/consumer/az9145.pdf cites a survey showing an average water usage of 7.6 gph, which seems like a lot compared to the 7.6 gpd below. And these things have 1/2 to 1 HP motors. Most home coolers have 1/2 HP or less. A Las Vegas homeowner might do better with Sam's portable 797895 Arctic Breeze cooler mounted inside a house near an open low window and That unit may be able to cool a 9 x 9 room. Not much more than that. an exhaust fan in a higher window with a one-way plastic film damper. Have you lived in Las Vegas or anyplace in the Southwest? You can't recycle the air in the house. You have to get rid of the moist air as it will not cool. That's what the exhaust fan does, controlling the indoor RH precisely with a humidistat, vs a swamp cooler without a humidistat. But the air is already quite humid when it enters the house. Turn on the cooler when the house temp reaches 80 F and turn on the exhaust fan when the RH reaches 60% to keep the house air at the upper right corner (80 F and w = 0.012) of the ASHRAE 55-2004 comfort zone. For an average good cooler pulling in 110 degree air at 10% humidity will lower the temperature to 80 degrees. The exhaust fan is working all the time if that dinky portable cooler can handle the load. Anyway a normal cooler which costs about the same will do the job. The maximum cooling is when the humidity is very low. Once it gets to 30% cooling becomes marginal. You are thinking about the air outside vs inside the house. No. At 110 degrees and 30% humidity the air coming out of the cooler is at 90 degrees. You can calculate it's relative humidity at that time. Keeping that house 80 F while evaporating P lb/h of water into C cfm of outdoor air means 1000P = (91.1-80)(128+C). P = 60C(0.075)(0.012-0.0066) = 0.0243C makes C = 108 cfm and P = 2.62 lb/h, ie 7.6 gallons per day. If the house has significant thermal mass (eg a floorslab), we can save more water and energy by only running the cooler at night. Have you ever lived in the Southwest where the overnight temperature does not get below 90? Most all houses in that area already have slab floors. The solution would be to move underground for the summer. And, I will agree that during the part of the season where the temperature does not get below 90 you may indeed us 7 gallons an hour to cool a 2000 square foot house. In that climate we usually set the thermostat at 80 or above. |
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Rich wrote:
A Las Vegas homeowner might do better with Sam's portable 797895 Arctic Breeze cooler mounted inside a house near an open low window and That unit may be able to cool a 9 x 9 room. Not much more than that. You have my numbers. Would you have any evidence for your article of faith? You can't recycle the air in the house. You have to get rid of the moist air as it will not cool. That's what the exhaust fan does, controlling the indoor RH precisely with a humidistat, vs a swamp cooler without a humidistat. But the air is already quite humid when it enters the house. Think "portable swamp cooler, indoors." Turn on the cooler when the house temp reaches 80 F and turn on the exhaust fan when the RH reaches 60% to keep the house air at the upper right corner (80 F and w = 0.012) of the ASHRAE 55-2004 comfort zone. For an average good cooler pulling in 110 degree air at 10% humidity will lower the temperature to 80 degrees. Think "portable swamp cooler, indoors." The exhaust fan is working all the time if that dinky portable cooler can handle the load. You have my numbers. Would you have any evidence for your article of faith? Keeping that house 80 F while evaporating P lb/h of water into C cfm of outdoor air means 1000P = (91.1-80)(128+C). P = 60C(0.075)(0.012-0.0066) = 0.0243C makes C = 108 cfm and P = 2.62 lb/h, ie 7.6 gallons per day. If the house has significant thermal mass (eg a floorslab), we can save more water and energy by only running the cooler at night. Nick |
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wrote in message ... Rich wrote: A Las Vegas homeowner might do better with Sam's portable 797895 Arctic Breeze cooler mounted inside a house near an open low window and That unit may be able to cool a 9 x 9 room. Not much more than that. You have my numbers. Would you have any evidence for your article of faith? I have no faith in your numbers because I think you have drastically oversimplified the problem. What is the efficiency of your heat exchanger. How much area is required to evaporate that much water? How much air movement is required? I have been indirectly associated with cooling problems for aircraft and space vehicles for 40 years. I know how complex such a system can become. If you really believe you can do it you are wasting your time trying to convice us. You should be in business building those units. |
#30
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On Sat, 15 Jan 2005 22:22:31 GMT, "Rich" wrote:
wrote in message ... Rich wrote: A Las Vegas homeowner might do better with Sam's portable 797895 Arctic Breeze cooler mounted inside a house near an open low window and That unit may be able to cool a 9 x 9 room. Not much more than that. You have my numbers. Would you have any evidence for your article of faith? Nick, you saying 'you have my numbers' is about like a streetwhore saying it. Just don't mean much, and not likely to impress anyone respectable. I have no faith in your numbers because I think you have drastically oversimplified the problem. What is the efficiency of your heat exchanger. How much area is required to evaporate that much water? How much air movement is required? I have been indirectly associated with cooling problems for aircraft and space vehicles for 40 years. I know how complex such a system can become. If you really believe you can do it you are wasting your time trying to convice us. You should be in business building those units. Paul ( pjm @ pobox . com ) - remove spaces to email me 'Some days, it's just not worth chewing through the restraints.' HVAC/R program for Palm PDA's Free demo now available online http://pmilligan.net/palm/ Free Temperature / Pressure charts for 38 Ref's http://pmilligan.net/pmtherm/ |
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Rich wrote:
You have my numbers. Would you have any evidence for your article of faith? I have no faith in your numbers because... You have none whatsoever! :-) Nick |
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wrote in message ... Rich wrote: You have my numbers. Would you have any evidence for your article of faith? I have no faith in your numbers because... You have none whatsoever! :-) Nick I have no faith in someone who can not answer questions. "Numbers" are meaningless unless you can explain how you derived them. Your arithmetic appears to be OK but you did not even explain how you derived the formula. You would have received a maximum of an incomplete in my class. I am trying to see if you can think. You are somehow going to magically evaporate 2.62 lb/h of water. As far as I know that can only be achieved with the largest of coolers using extremely hot and dry air. I want to know what apparatus will do such a thing in an environment such as you describe. The portable unit you picked can't evaporate more than about two gallons a day using 10%, 100 degree air. How are you going to make it evaporate 7 gallons using air that already has a higher water content and temperature approaching 80 degrees. It is rather simply to state that evaporating a gallon of water will remove 8100 BTUs of energy from the air. The mechanism is something else. A well designed pad for a whole house cooler has 3000 to 4500 square foot of surface area for evaporation. That portable one probably has about 500 square foot. |
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Rich wrote:
...I am trying to see if you can think. Amusing. Try some premises, Rich. Do we agree that: 1. Most people find 80 F at 60% RH (w=0.012) comfortable. 2. A C cfm airstream has an effective thermal conductance of about C Btu/h-F. 3. It takes about 1000 Btu to evaporate a pound of water. Cooling more outdoor air than we need to wastes water and energy. What's the minimum outdoor airflow C in cfm and water evaporation rate P lb/h needed to cool a house with a 128 Btu/h-F conductance to 80 F at w=0.012 if the outdoor air is 91.1 F with w=0.0066? Air weighs about 0.075 lb/ft^3. You are somehow going to magically evaporate 2.62 lb/h of water. As far as I know that can only be achieved with the largest of coolers using extremely hot and dry air. But your "5000 cfm" cooler might evaporate 5 gallons per hour. I want to know what apparatus will do such a thing in an environment such as you describe. We haven't talked about that. More premises: 4a. An A ft^2 pool of water loses about 100A(Pw-Pa) Btu/h by evaporation, where Pw is the vapor pressure ("Hg) at the water temp and Pa is the vapor pressure of the air around the pool (ASHRAE), or if you prefer, 4b. The ratio of heat loss by evaporation to heat gain by convection R = 100(Pw-Pa)/(Tw-Ta), in T (F) degrees, regardless of windspeed (Bowen, 1926). (R = -1 defines the wet bulb temp.) 5. A ft^2 in a V mph wind has about A(2+V/2) Btu/h of airfilm conductance. The portable unit you picked can't evaporate more than about two gallons a day using 10%, 100 degree air. Would you have any evidence for this article of faith? That portable one probably has about 500 square foot. Try 4a. How are you going to make it evaporate 7 gallons using air that already has a higher water content and temperature approaching 80 degrees. It helps if the cooler is near a window with incoming air. More premises: 6. Pa = 29.921/(1+0.62198/w) "Hg and 7. Pw = e^(17.863-9621/(Tw+460)) "Hg (a Clausius-Clapeyron approximation.) A well designed pad for a whole house cooler has 3000 to 4500 square foot of surface area for evaporation. But that's way too much air and water, with poor controls. Nick |
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Rich wrote:
You are somehow going to magically evaporate 2.62 lb/h of water... I want to know what apparatus will do such a thing... A portable swamp cooler near an open window comes to mind, or some Humidifalls (tm) with the heaters turned off, or a rock cairn with a $10 10 W fountain pump in a corner or a few toilet tank fountains or an indoor greywater wetland or (my favorite), a concrete slab. My PA neighbor has a 20-year old basement slab that was probably placed with no vapor barrier underneath, unlike present practice. The water table is high (my old hand-dug well has water 9' below ground) and water seems to be moving up through the slab and evaporating into basement air. We never see puddles or damp spots on the slab. The gutters and downspouts are in good shape, but after 3 blower-door tests and air sealing, the house air is never less than 60% RH in wintertime, even with a bathroom exhaust fan in series with a 60% humidistat. It's probably time to paint the slab. ...An A ft^2 pool of water loses about 100A(Pw-Pa) Btu/h by evaporation, where Pw is the vapor pressure ("Hg) at the water temp and Pa is the vapor pressure of the air around the pool (ASHRAE) Pw = e^(17.863-9621/(80+460)) = 1.047 "Hg and Pa = 29.921/(1+0.62198/0.012) = 0.566 "Hg, so each square foot of 80 F wet surface will evaporate 48 Btu/h (about 0.048 lb/h), if it's only exposed to house air. In that case, we need about 2.62/0.048 = 54 ft^2. I can imagine a 50' soaker hose in series with a solenoid valve making a 1'x50' perimeter strip of slab dampish. A new house might have plastic film on the caliche, under stone, under concrete, with a hole in the slab for water to enter and flow under the slab. Cooling thermal mass directly is more efficient than cooling air that cools mass, and a cool slab with a ceiling fan and a room temp thermostat and an occupancy sensor might allow good room air temp control with a cooler slab with a larger temp swing that stores more coolth and allows effective "AC setbacks" when a room is unoccupied. Nick |
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AZGuy wrote:
What you can't seem to understand is that your formulaes mean nothing if they don't result in the same outcome as occurs in the real world. I'm not aware that anyone's tried this yet. Seems easy enough. Why don't you? People who use evap coolers know how much CFM is needed to be comfortable on a 110 degree day with humidity of 20%. How much, for a house with a 128 Btu/h-F conductance? You're like the theorist who can "prove" that bees can't fly. That guys theory was inadequate, just as yours seems to be. Shades of Harry Thomason. See "Solar Heat in Snow Country" at http://www.ece.villanova.edu/~nick Nick |
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AZGuy wrote:
People who use evap coolers know how much CFM is needed to be comfortable on a 110 degree day with humidity of 20%. How much, for a house with a 128 Btu/h-F conductance? Pa = 0.2e^(17.863-9621/(110+460)) = 0.535 "Hg, so w = 0.62198/(29.921/Pa-1) = 0.0113. At 80 F and w=0.012, 1000P=(110-80)(128+C) and 60C(0.075)(0.012-w) = P make C = -142 cfm, so it can't be done. Do people who use evap coolers know that? :-) It's easy to see why it can't be done. Air has a specific heat of 0.24 Btu/lb-F. Each pound of air needs sensible cooling from 110 to 80 F, which takes 0.24(110-80) = 7.2 Btu, but we can only add 0.012-0.0113 = 0.0007 pounds of water per pound of air to raise its humidity ratio from 0.0113 to 0.012, which only provides 1000x0.0007 = 0.7 Btu of latent cooling. But there's still hope for evap cooling with cooler outdoor air at night or outdoor air that's passed through earthtubes, as well as indirect schemes. Nick |
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wrote in message ... AZGuy wrote: What you can't seem to understand is that your formulaes mean nothing if they don't result in the same outcome as occurs in the real world. I'm not aware that anyone's tried this yet. Seems easy enough. Why don't you? This is done to some extent all over the southwest. They sell those portable coolers everywhere as they are often used to cool one room. A family member had one for a while. It was worthless when sitting in the middle of the room. They would exhaust air with a fan but the cooling was minimal. Finally they devised a way to mount it by a window so they could use only dry outside air. Even then it was good for only a few feet near the cooler. Another problem is the intensity of the sun. Just a few years ago I was in Maryland during the hottest part of the day. I noted that my car air conditioner worked better there than it did in the Southwest. The difference being that the suns rays were so much more intense in the SW. I was doing something in the sun so I moved into the shade. It did not make any difference. The surface and interior of the car stayed much cooler there than in the SW. I have had tires rot from the heat before they wore out. In the SW the sun is so intense you can burn in a few minutes (Thus Cowboys with their wide brimmed hats and long sleeves). In the SW it can be like an inferno in the sun but quite comfortable in the shade. This also reminds me of a story about a friend from Europe who was on his way to Los Angles. He was traveling by train and got off at Albuquerque. he said he went around asking if it got that hot in California. He had never experience heat that intense. People who use evap coolers know how much CFM is needed to be comfortable on a 110 degree day with humidity of 20%. How much, for a house with a 128 Btu/h-F conductance? You are also using a rather small house for an example. Maybe that is the problem as most people in the Southwest live in houses twice the size you are using for an example. Most have slab floors. You're like the theorist who can "prove" that bees can't fly. That guys theory was inadequate, just as yours seems to be. Shades of Harry Thomason. See "Solar Heat in Snow Country" at http://www.ece.villanova.edu/~nick Nothing unusual there. Perhaps only that he is using trickling water instead of a network of pipes, but he still has 700 sq. feet of collector. They can be about 80% efficient. During the energy shortage of the 70s solar heat was very popular in Colorado where the sun is quite a bit more intense and more available (very few cloudy days) than in the northern part of the country. Now most of those units have been abandoned. They are effective when replacing electric heat. At present prices it is still cheaper to heat with natural gas. A plastic cover on a swimming pool will very rapidly result in a pool that is too hot. Some heat their pools by running their filter water through some black irrigation pipe on a patio roof. But those have nothing to do with cooling by evaporating water. One place where I worked the temperature often got to as high as 120 degrees. When those temperatures occurred the humidity was often about 2%. At 90 degrees the humidity would normally be about 20%. They had three large ponds between the buildings with multiple heads spraying water into the air. Surrounded by grass it was quite pretty. The ponds were actually cooling ponds for the buildings refrigeration units. Initially the heads were about a foot above the pond surface. The freon began to get too warm so they raised the heads about six feet to get more evaporation. Later they added another ponds. |
#40
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Rich wrote:
What you can't seem to understand is that your formulaes mean nothing if they don't result in the same outcome as occurs in the real world. I'm not aware that anyone's tried this yet. Seems easy enough. Why don't you? This is done to some extent all over the southwest. They sell those portable coolers everywhere as they are often used to cool one room. A family member had one for a while. It was worthless when sitting in the middle of the room. They would exhaust air with a fan but the cooling was minimal. Finally they devised a way to mount it by a window so they could use only dry outside air. Even then it was good for only a few feet near the cooler. There are many ways to do something badly :-) I suspect a lot more insulation and airtightness and more precise controls would help a lot. Another problem is the intensity of the sun. Just a few years ago I was in Maryland during the hottest part of the day. I noted that my car air conditioner worked better there than it did in the Southwest. The difference being that the suns rays were so much more intense in the SW. I was doing something in the sun so I moved into the shade. It did not make any difference. The surface and interior of the car stayed much cooler there than in the SW. I have had tires rot from the heat before they wore out. In the SW the sun is so intense you can burn in a few minutes (Thus Cowboys with their wide brimmed hats and long sleeves). In the SW it can be like an inferno in the sun but quite comfortable in the shade. We seem to have shifted from engineering to poetry. Nick |
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