Return air temp vs supply air tem delta T

[Pairadice]

Hi and thanks for any help I can get!
I’ve been a member for about 5 years and come in time to time if I have valuable input, for the most part all of my issues have already been answered.
I recently got transferred to Las Vegas and I’m dying here!
I lost a fan on my center AC so its hot inside, running about 97-99 during the day and cooling to about 75-80 at night. I added a 10,000 btu portable unit ducted outside and it only made about 2* difference, then I added a swamp cooler also with little differences.
I believe my other two ACs are also failing or low on Freon, I had this unit in south Texas for over two years in temps north of 110 with no issues!
I used an infrared temp gun and read my supply and return air temperature readings and was only getting a difference of 9-12*, i would have thought that the reading shoul be closer to a 30* difference, meaning the return air temp was dropped by 30* on the supply side if I’m saying this correctly.
BTW, on 7/1 with an overnight low of 97* my RV temp was 61* inside, since then I have installed foil face bubble wrap on every window so any help is appreciated!

 

[wdk450]

I was in very hot California Central Valley summer weather for a couple of years and had bad insufficient cooling problems then. I did some measurements like you did, and noting current draws when my only 15K btu Dometic Brisk Air II was running, convinced me that my AC compressor was not running at the height of the outside heat (110 degrees plus). Research into the AC system revealed that there is a protective OVERTEMPERATURE CUTOUT SWITCH on the top of the compressor. If the ambient heat gets too high, and/or the refrigeration system is getting old, (mine was nearing 10 years old), this compressor temperature cutout can open power to your AC compressors at the worst (hottest) of times.

The first year due to limited funds, I did an economy patch by getting a medium sized indoor desk fan and mounting it to the outside of the AC shroud with mechanics wire, with the airflow directed inward at the top of the compressor where the cutout switch is located. I was in a situation in which I didn't move the rig for 2 years, and was in a very dry (drought) location. I ran an extension cord from the AC shroud on the roof to an outlet in the refrigerator slide outer access. By the next summer temperature onslaught, I had saved up, bought a new rooftop AC section online, and had an RV professional help me install it. The new rooftop unit did not have the overheat cutout problems in high temperatures.

An additional note: RV's are built with light insulation, and roofs that are minimally infrared heat reflective. I STRONGLY RECOMMEND that anyone who endures extended high heat challenges look into coating their RV roof with Henrys Tropi-Cool 887 Elastometric Roof Coating. A National reflective roof coating board rates it at 94% IR reflective. My experience was that before I had it applied by an RV professional, I had to put rags under may hands when crawling around the Dicor rubber roof during 75 degree sunny days, because of the roof heat. After it was applied (and as an added bonus it does a wonderful job of completely watersealing the roof system) in the same 75 degree temperatures the roof felt COLD to the touch.

Here is a link to 1 source for the roof coating: https://www.homedepot.com/p/Henry-8...-Reflective-Roof-Coating-HE887HS018/205049553

 

[Pairadice]

Thanks for the feedback I appreciate it and will look into the cutoff on the AC