Dual A/C still not enough in 90 degrees, sun, wind, humidity?

[lewster]

Originally Posted by Jammer

Lew,

I'll try that. The temperature differential is definitely less than 18 degrees. I suspect based on the other posts here though that there is exterior air leakage into the shroud around the evaporator. The unit is new this year and should still be under warranty should there be a refrigerant leak.

That temp differential should be the same regardless of the outside ambient temps since it measures the performance of the unit from the inside of the coach, so less that 18* is a definite problem!

Another 'trick' that I use is to use heavy aluminum tape around all of the seams on the evaporator cover and be sure that the 2 or 3 openings in that inner shroud are completely sealed.

Another problem on the newer Duo-Therm units is improper foam sealing. This 2 X 2" strip of foam usually runs along the top of the condenser coils, across the top rear of the evaporator shroud, down the right side along the rear edge of the control box and also along the rear seam of the condenser from the top left to the base pan. This foam is really important for proper cooling efficiency in the Duo-Therm units. If you don't see it on top of teh coils, it might be stuck to the inner top of the A/C shroud.

If you have one of the newer units that have a molded plastic evaporator shroud, you might check to see that all of the screws are in place and that the friction clasps (IIRC, there are about 6-7 of these spaced around the seam of the shroud) are properly snapped down. These newer covers are much better than the older ones, but only if they are properly installed....... and I have seen some that were NOT !!

[HowieE]

Unfortunately without a tap on the suction line it is hard to determine the super heat. What you can do is remove the shroud and check for any outside air infiltration. If the that is OK and after the unit has run for at least 15 min. look at the suction line, the larger of the 2 at the compressor. Pull back the insulation. The pipe should be wet if there is any level of humidity. If it is dry or shows ice close to the compressor you are low on gas and need a replacement.

[Jammer]

New twist on an old problem.

As I have posted elsewhere, my trailer went to the dealer on several occasions for warranty work. A/C problems were on the "punch list" on most of these visits, and I did find and resolve some A/C-related problems myself. The dealer fixed a vibration problem in the rear A/C, and I found and fixed a wiring problem in the temperature sensor for the rear A/C. Ultimately, the dealer declared that there was nothing wrong with the front A/C and it was cooling sufficiently. By then it was fall and I quit pursuing the matter.

With both A/Cs operating, the trailer cools marginally, as I have reported in other threads. Performance is unchanged since the unit was new.

I have been up on the roof and have opened up both A/C shrouds. The front A/C is the "high capacity" model, 15,000 btu/h. The rear one is 13,500 btu/h. These were among the first R-410a Penguins made. They are the heat pump model. There are no problems with blockage or missing foam, etc.

I recently took an accurate measurement of amp draw and voltage, which showed that the front A/C is drawing less current than it should. I rechecked the temperature differential, which is around 15 degrees on the front A/C and 25 degrees on the rear A/C.

I've decided to try again to get the front A/C fixed and am taking the trailer to a different Dometic service center. I anticipate that there will be a spirited discussion over whether this repair is covered by warranty.

[HowieE]

Not sure what refrigerant is in your unit but when I was working with ACs in an earlier life time 18 to 20 degrees was consider the limit in efficiency for a unit. Given the 15 degree differential on the front unit I would say it could use some help.

I would request that who ever looks at the unit test the superheat on it. That is where the rubber meet the road and can't be faked.

[Jammer]

Some measurements I took that may be helpful to others.

118v supply voltage under load.
88 degrees F. ambient temperature. Windows open, same temp in and out.

Rear A/C appears to be working properly. 13,500 BTU Dometic Penguin with R-410a:
Low fan 2.8a
High fan 3.4a (nameplate 3.5a)
High cool 10.0a (compressor only) (nameplate RLA 12.5)
Outlet temperature 64 degrees, 24 degrees below inlet

Front A/C (insufficient cooling). Dometic "high capacity," also R-410a.
Low fan 2.3a
High fan 2.7a
High cool (compressor only) 7.8a
Outlet temperature 74 degrees, 14 degrees below inlet.

Readings were taken one unit at a time after each unit had been operated for several minutes to allow it to stabilize.

I didn't photograph the front unit's nameplate so I'm unsure of its ratings. Dometic's web site shows 13.4 RLA for the compressor and 2.6 for the fan, but I know that there can be some variation depending on production date.

The trailer is at a Dometic service center now and I'm trying to get Dometic to cover repairs or replacement under warranty.

[J. Morgan]

Assuming that there is sufficient refrigerant in the unit, my guess is that the heat pump valve is leaking internally.

This makes everything fit including the front units lower current draw.

[J. Morgan]

And since the manufacturer doesn't see fit to manufacture a unit that is really repairable I would say that with your record of service history......

Well

[Jackcat2]

We've used that insulated reflective roll material, cut to fit between the windows and screens, and in skylights and fan tas tic fans (in the interior) and found 105 full sun bearAble in full AZ sun, with our 30' classic, one ac unit. Our blessing was the very low humidity.

[J. Morgan]

"The last failure situation is the valve stuck somewhere between cycles, which is usually a difficult situation to diagnose. The valve slide position is such that the net result is a significant amount of leakage between low and high side pressures, producing symptoms of a faulty compressor…high suction and low head pressures."

http://wayneshirley.wordpress.com/20...ersing-valves/

[JFScheck]

Originally Posted by Jammer

Was out camping in Western Minnesota this weekend in 90+ degree temps, full sun, no shade, and wind, and could not keep the traylah cool with both A/Cs blowing. Rear A/C was keeping the bedroom cool but front part of the trailer was still 84 degrees.

Is this is as good as it gets or do I have an A/C problem? Front A/C was blowing on high fan, measured outlet temps in low 70s, inlet in high 80s.

Exact same experience with my 2011 30" Classic with one 13,500 in the bedroom and one 15,000 in the main living space. Opening Awnings does help but.....

I have two 13,500's with the Couch within 35 feet of living space and two bump outs, hoping the ducted A/C works a bit better....

[lewster]

Originally Posted by Jammer

Some measurements I took that may be helpful to others.

118v supply voltage under load.
88 degrees F. ambient temperature. Windows open, same temp in and out.

Rear A/C appears to be working properly. 13,500 BTU Dometic Penguin with R-410a:
Low fan 2.8a
High fan 3.4a (nameplate 3.5a)
High cool 10.0a (compressor only) (nameplate RLA 12.5)
Outlet temperature 64 degrees, 24 degrees below inlet

Front A/C (insufficient cooling). Dometic "high capacity," also R-410a.
Low fan 2.3a
High fan 2.7a
High cool (compressor only) 7.8a
Outlet temperature 74 degrees, 14 degrees below inlet.

Readings were taken one unit at a time after each unit had been operated for several minutes to allow it to stabilize.

I didn't photograph the front unit's nameplate so I'm unsure of its ratings. Dometic's web site shows 13.4 RLA for the compressor and 2.6 for the fan, but I know that there can be some variation depending on production date.

The trailer is at a Dometic service center now and I'm trying to get Dometic to cover repairs or replacement under warranty.

With a compressor amp draw of only 7.8A, you have lost refrigerant and need a replacement unit.