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Old 09-24-2011, 12:34 PM   #1
Festus2
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Question A/C Not Keeping You Cool??

It seems that this problem has appeared often during the past month or two. The unusually hot temperatures that many of you are experiencing is causing your A/C to work overtime or isn't keeping you cool enough. If you have run into this problem this summer, then you might find the following article (which I just came across) of interest.

"A problem often seen is the A/C isn't cooling. It's blowing but the air coming out is barely cool.
Most of the time, the problem is the unit is freezing up. Many people equate the use of an RV A/C with a residential A/C so they keep lowering the temperature setting to Cooler. This is almost the exact opposite of what they should be doing.
The roof A/C is a sealed system. When the compressor is running, it is under a great deal of pressure. In order to cool properly, the compressor must cycle on and off. If it is running constantly, it never shuts off so it never relieves the head pressure on the compressor. It then freezes up and when it does, it stops cooling.
After being off for an hour or so, it will again start cooling but wil just repeat the freezing up process if the thermostat is set to too low a temperature.
The first thing you need to understand is no RV A/C will keep the inside of an RV at 68 degrees in the midst of summer or on a hot day. The system simply can't do it and RV's are not insulated well enough to allow it to happen.
To get the most out of your A/C, never set the thermostat lower than 3/4 or 74 degrees. This will allow it to cycle on and off and will produce maximum cooling at this setting. You may be a tad warmer but overall you will end up being much cooler than you will by cranking the thermostat down. The coolest settings are not always the best settings in extreme temperatures.
You can maximize the effectiveness by: Closing all the shades, lower the awning, put alum reflective foil on your windows, and park, if possible in as much shade as you can." S. Franklin

I thought I would share this article with you --- now that summer is over .
Hope you find it useful --- for next year.

PS I am assuming that the author is referring to a single, standard BTU A/C.
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Old 09-24-2011, 03:17 PM   #2
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That doesn't sound correct to me, at least as a general rule. That advice may be true if the unit is freezing up (which if happening is something that should be corrected) but otherwise I don't see why there would be any reduction in cooling capacity when the compressor runs continuously. Of course the unit ideally should be matched to the heat load but if the load is excessive then running the unit continuously would provide more cooling then forcing it to cycle by setting the thermostat higher than you would like. But I might be wrong... I was wrong once before...

Maybe if we have any HVAC pros watching they could shed some light...
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Old 09-24-2011, 03:56 PM   #3
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Our A/C doesn't freeze up and has run constantly all day long on many occaisions, sometimes for weeks at a time. Thermostat set on 70 and the compressor will not start cycling until sometime after sundown.

I'm not an expert but freeze up is usually caused by low refridgerant or low air flow.
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Old 09-24-2011, 04:52 PM   #4
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On July 4th 2007 in Las Vegas it was 117 degrees mid-day. Inside my then motor home, it never got below 85 untill late afternoon. My two 13.5 units ran continuously without freezing up. Yes it can happen but it is not the norm & the thermostat was set well below 85.
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Old 09-24-2011, 08:08 PM   #5
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AC

In Las Vegas the reliative humidity is low enough that the AC will not freeze up but it will not have sufficient capacity the carry the heat load during the day.

John
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Old 09-24-2011, 08:49 PM   #6
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The author of this article, S. Franklin, didn't state what size A/C he was referring to -- the usual factory supplied 13.5 BTU or the larger unit nor did he mention about the increased cooling ability of having 2 A/C units. No reference was made about the size and interior space of the RV or the outside temps he was talking about. All of these would be variables to consider in your own situation and your own experiences with A/C may differ from his.
I posted the article for interest sake only. Those are his suggestions and may not be entirely factual.
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Old 09-25-2011, 07:26 AM   #7
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Postscript

Festus2 -

I think one of Hankaye's closing applies here:

Results not guaranteed. Your results might vary.


Ron
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Old 09-25-2011, 08:49 AM   #8
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Are Variables Relevant?

Festus2:

If S. Franklin is correct that running your AC continuously will result in freeze-up, then the variables you mention seem irrelevant to me. (Maybe that's why he didn't mention any variables.)

And if, as another poster said, freeze-up is a symptom of a problem that needs to be corrected, then the variables you mention might affect the frequency of freeze ups, but would not be the cause of freeze ups.

I think S. Franklin is just plain incorrect. If your unit freezes up, it needs to be fixed regardless of the variables.
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Old 09-25-2011, 01:51 PM   #9
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An AC freezing up does indicate a problem that needs to be addressed, but it's not the compressor running constantly. The main causes of icing are air flow restrictions(dirty return air filter, Dirty evaporator coil, improperly sized or installed ducting, discharge air leaking back to the evaporator) and low charge(not likely in a sealed unit unless a leak has developed), again, not a commom problem. I have many marine customers with ACs that run constantly(most of them are undersized) and they do not ice up. If the evaporator reaches a temperature of 32 degrees or lower, it will ice, and if you run it constantly on a cool night, that is sometimes possible and for that to happen, you would have to be trying to cool it down to 60 degrees, but when it's 85 degrees in the trailer and there's that kind of load on the unit, it's not going to happen.
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Old 10-03-2011, 12:34 PM   #10
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BOB THAT WAS A BRILLIANT ANSWER. I HAVE NEVER LOOK IN MY A/C ON MY CAMPER WONDER IF THEY HAVE A TEMP SENSOR ON THE EVAP CORE LIKE A UNIT IN A CAR. THAT PART IS CALLED AN ANTI ICING SWITCH FOR WHEN THE CORE TEMP GOES WAY LOW AND HIGH HUMIDITY. ONEDAY WILL HAVE TO CLIMB UP AND LOOK. IHAVE ALWAYS KEPT MY CONDENSOR AND EVAP CLEAN AS WELL AS THE DRAIN JUST NEVER LOOKED MY TWO UNITS WORK VERY WELL IN THE HIGH HEAT AND HUMIDITY IN THE NORTH EAST. CAMP ON!!
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