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| [GMCnet] Atwood air conditioners [message #274349] |
Wed, 25 March 2015 18:10  |
Advanced Concept Ener
Messages: 112
Registered: December 2014
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There are two fans on every air conditioner. One blows air over the evaporator to cool the spaces and the other blows air over the condenser to get the heat out of the system. Some air conditioners have both fans attached to one motor. This one seems to have individual motors for each fan. Two fans might give you a unit that can be more compact and also might use a little less energy on cool moist days when you need AC to remove moisture rather than hot air from the coach. That assumes they run the two fans independent of each other. To pick a unit check current draw or watts for a given BTU rating. Remember units that are too big cycle too much and don't remove humidity as well as a smaller unit that runs constantly.
Jon Darcy ACES
North Jersey 76 stretch, flares, 4 bag, Alcoa's, bunkhouse,MAC Dash
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| Re: [GMCnet] Atwood air conditioners [message #274350 is a reply to message #274349] |
Wed, 25 March 2015 19:07  |
Joe Weir
Messages: 769
Registered: February 2013
Location: Columbia, SC
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Love ya brother, but I have twice been snookered with that argument by well meaning ac professionals.
Both times I wanted to step up to the next half ton. Both times talked out of it. Both times I ended up with a unit that would not cool the house on the hottest days.
My other favorite from ac guys is " well, a 20 degree differential in the outside temp is about all they are good for" when you want to know why that "properly sized, and efficient" unit is not cooling off the house.
A pox on all their houses... 
Advanced Concept Ener wrote on Wed, 25 March 2015 18:10...Remember units that are too big cycle too much and don't remove humidity as well as a smaller unit that runs constantly.
Jon Darcy ACES
North Jersey 76 stretch, flares, 4 bag, Alcoa's, bunkhouse,MAC Dash
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76 Birchaven - "Wicked Mistress" - New engine, trans, alum radiator, brakes, Sully airbags, fuel lines, seats, adult beverage center... those Coachmen guys were really thinking about us second hand owners by including that beverage center...
Columbia, SC.
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| Re: [GMCnet] Atwood air conditioners [message #274353 is a reply to message #274349] |
Wed, 25 March 2015 20:33 |
kerry pinkerton
Messages: 2565
Registered: July 2012
Location: Harvest, Al
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LOOOOOOOONG time ago I was in the AC business. In THEORY, the perfect unit would run 100% of the time. In THEORY the temperature and humidity is constant 24x7x365. In THEORY heating and cooling LOSSES/GAINS are also constant rather than effected by sunshine, shade, and wind. In practice, that ain't ever gonna happen.
To keep your home cool (or warm) enough, the unit(s) have to be sized to address the heating/cooling loads and #cubic feet being conditioned on a WORSE CASE day. Sizing the unit for the average daily temp is going to mean you'll be cold in the winter and hot in the summer.
As for me and my house, I'll usually go with at least a half ton more than the recommendation and have happy with that approach for 45 years.
Kerry Pinkerton - North Alabama
Had 5 over the years. Currently have a '06 Fleetwood Discovery 39L
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| Re: [GMCnet] Atwood air conditioners [message #274358 is a reply to message #274349] |
Wed, 25 March 2015 21:40 |
Chr$
Messages: 2690
Registered: January 2004
Location: Scottsdale, AZ
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Advanced Concept Ener wrote on Wed, 25 March 2015 16:10There are two fans on every air conditioner. One blows air over the evaporator to cool the spaces and the other blows air over the condenser to get the heat out of the system. Some air conditioners have both fans attached to one motor. This one seems to have individual motors for each fan. Two fans might give you a unit that can be more compact and also might use a little less energy on cool moist days when you need AC to remove moisture rather than hot air from the coach. That assumes they run the two fans independent of each other. To pick a unit check current draw or watts for a given BTU rating. Remember units that are too big cycle too much and don't remove humidity as well as a smaller unit that runs constantly.
Jon Darcy ACES
North Jersey 76 stretch, flares, 4 bag, Alcoa's, bunkhouse,MAC Dash
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If this is in response to my last quote, (not sure, thread was split) Let me be more specific: Two fan MOTORS
The cheaper units use a motor with a shaft coming out both ends. One runs the indoor fan, one the outdoor fan. They suck. When you put the fan on low, BOTH fans slow down on single motor units. Hence, less heat transfer on the condenser.
-Chr$: Perpetual SmartAss
Scottsdale, AZ
77 Ex-Kingsley 455 SOLD!
2010 Nomad 24 Ft TT 390W PV W/MPPT, EV4010 and custom cargo door.
Photosite: Chrisc GMC:"It has Begun" TT: "The Other Woman"
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| Re: [GMCnet] Atwood air conditioners [message #274366 is a reply to message #274350] |
Thu, 26 March 2015 00:29 |
roy1
Messages: 2126
Registered: July 2004
Location: Minden nevada
Karma: 6
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Joe Weir wrote on Wed, 25 March 2015 17:07Love ya brother, but I have twice been snookered with that argument by well meaning ac professionals.
Both times I wanted to step up to the next half ton. Both times talked out of it. Both times I ended up with a unit that would not cool the house on the hottest days.
My other favorite from ac guys is " well, a 20 degree differential in the outside temp is about all they are good for" when you want to know why that "properly sized, and efficient" unit is not cooling off the house.
A pox on all their houses...
Advanced Concept Ener wrote on Wed, 25 March 2015 18:10...Remember units that are too big cycle too much and don't remove humidity as well as a smaller unit that runs constantly.
Jon Darcy ACES
North Jersey 76 stretch, flares, 4 bag, Alcoa's, bunkhouse,MAC Dash
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A 20 degree differential in temperature is the accepted temperature split of the air measured before and directly after the evaporator coil in package and split a/c units (not auto a/c units). The building insulation ,ceiling height amount of glass, wall exposure to south&south west sun, extreme ambient temperature square footage etc all need to be considered before the tonnage can be determined. In hot country the compressor should not be running non stop in 90 degree weather or it won't cool worth a damn when the osa reaches 110 degrees. When it is that hot outside the inside temperature still needs to be capable of being in the high 70's or the system wasn't sized properly. At this high osa I would expect the compressor to be running continuously . True if the unit is too large in a small space it will blow too much cold air and cycle too much .sometimes 2smaller units are better then 1 big one some units have multiple compressors and or variable speed evap fans. It can get complicated. In very humid areas electric strip heaters can be added to the duct work to force the compressor to run longer controlled by a humidistat but I'd hate to be paying that power bill.
Roy Keen
Minden,NV
76 X Glenbrook
[Updated on: Thu, 26 March 2015 00:35] Report message to a moderator |
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| Re: [GMCnet] Atwood air conditioners [message #274369 is a reply to message #274366] |
Thu, 26 March 2015 06:45 |
Joe Weir
Messages: 769
Registered: February 2013
Location: Columbia, SC
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roy1 wrote on Thu, 26 March 2015 00:29Quote:
My other favorite from ac guys is " well, a 20 degree differential in the outside temp is about all they are good for"
A 20 degree differential in temperature is the accepted temperature split of the air measured before and directly after the evaporator coil in package and split a/c units (not auto a/c units).
And there is the fine print. Sure, 20 degrees per pass through the.evaporator. If the temperature is equal to outside air temp by the time it gets back to the evaporator the unit ain't big enough... 100 degree days: never cycles off and never gets below 80. We get a lot of those here.
I just always luck out and get the efficiency nut who insists I don't need a larger unit.
76 Birchaven - "Wicked Mistress" - New engine, trans, alum radiator, brakes, Sully airbags, fuel lines, seats, adult beverage center... those Coachmen guys were really thinking about us second hand owners by including that beverage center...
Columbia, SC.
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| Re: [GMCnet] Atwood air conditioners [message #274414 is a reply to message #274369] |
Thu, 26 March 2015 20:58 |
roy1
Messages: 2126
Registered: July 2004
Location: Minden nevada
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Regardless of the tonage of the unit for residential units and most comercial units the evp TD should be around 19 to 21 degrees or the system has a problem. It doesn't matter if the outside ambient is 80 deg or 100 degrees. Larger systems just move more air over the coil.sure if you suck a lot of outside air in it will be warmer and you won't cool but that can be restricted or shut off. It's that simple but if the system isn't sized properly or the ducts are wrong you won't be comfortable .weither you are hot or cold the TD should still be 21 degrees just more or less air depending on the size of the unit.Yeah If the unit isn't big enough when the air returns to the evap it is warmer each time but the TD is still 21 degrees even if it is 90 in the room. On the other hand if the unit is oversized and the stat is set low you will freeze your ass but the TD will still be 21 degrees till the coil starts to ice up due to the cold coil temperature. Things aren't quite as simple on large comercial systems as those compressors have cylinder unloaders and variable speed evap fans etc. but you weren't talking about those. I doubt things have changed much since I retired from the comercial a/c service industry after 40 years of work except most everything is now computer controlled and not as much fun just like new cars versus old carbureted cars.
Roy Keen
Minden,NV
76 X Glenbrook
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| Re: [GMCnet] Atwood air conditioners [message #275580 is a reply to message #275578] |
Fri, 10 April 2015 15:10 |
Dolph Santorine
Messages: 1236
Registered: April 2011
Location: Wheeling, WV
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Valves.
It's pretty clever.
Dolph Santorine
DE N8JPC
Wheeling, West Virginia
1977 ex-Palm Beach TZE167V100820
1-ton, Sullybuilt Bags, Reaction Arms, 3.70 LSD, Manny Transmission, EV-6010,
> On Apr 10, 2015, at 4:02 PM, Larry Davick wrote:
>
> As I reported in a different post I ran the heat pump on my coach and it warmed up nicely. I’m wondering if reversing cycle of the refrigerant from hot to cold is accomplished with valves in the refrigerant line, or if the compressor simply runs backward?
>
> In any case I like this Atwood AC150 even if it is taller than my old unit.
>
> Larry Davick
> A Mystery Machine
> 1976(ish) Palm Beach
> Fremont, CA
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| Re: [GMCnet] Atwood air conditioners [message #275584 is a reply to message #275578] |
Fri, 10 April 2015 15:57 |
roy1
Messages: 2126
Registered: July 2004
Location: Minden nevada
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ljdavick wrote on Fri, 10 April 2015 13:02As I reported in a different post I ran the heat pump on my coach and it warmed up nicely. I'm wondering if reversing cycle of the refrigerant from hot to cold is accomplished with valves in the refrigerant line, or if the compressor simply runs backward?
In any case I like this Atwood AC150 even if it is taller than my old unit.
Larry Davick
A Mystery Machine
1976(ish) Palm Beach
Fremont, CA
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It is called a reversing valve . In the heat mode the evap coil becomes the condenser coil and the condenser becomes the evap. Go on the roof you will feel the cold air blowing out of the unit.
Roy Keen
Minden,NV
76 X Glenbrook
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| Re: [GMCnet] Atwood air conditioners [message #275795 is a reply to message #274353] |
Mon, 13 April 2015 15:14 |
stick miller
Messages: 1036
Registered: March 2010
Location: Americus, Georgia
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kerry pinkerton wrote on Wed, 25 March 2015 21:33LOOOOOOOONG time ago I was in the AC business. In THEORY, the perfect unit would run 100% of the time. In THEORY the temperature and humidity is constant 24x7x365.
Kerry - I think my 105 year old house proves your theory. Units never shut off. It's hot in the summer and cool in the winter, but the damn things run 24 X 7 X 365.
Stick Miller
'78 Royale - "White Trash" - she left me for another man
'76 Eleganza - "Cousin Eddie" Sold
'84 Bluebird Wanderlodge - "Past Tents"
Americus, GA
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