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Topic: Rooftop ac (Read 682 times) previous topic - next topic

Rooftop ac

Does the front rooftop unit typically put out a little higher temperature of airflow than the rear unit.
It seems like it is colder back there, than in the front.  Could it be the larger sq footage in the front?

Thanks
Rick & MJ Berry
1998 U320 40'
Ohio

Re: Rooftop ac

Reply #1 –
When we run both units set to the same temp, it is always colder in the bedroom, and that unit runs less often.

Like you said, smaller area to cool seems the likely reason (assuming both units are the same size/model).
1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"

Re: Rooftop ac

Reply #2 –
Check the outputs with an inexpensive IR gun.

Pierce
Pierce and Gaylie Stewart
'93 U300/36 WTBI
Detroit 6V-92TA Jake
1140 watts on the roof
SBFD (ret)

Re: Rooftop ac

Reply #3 –

You front AC is also closer to the front door and near bigger windows, so all things being equal, it'll probably be the first one to "plug up". If Pierce's recommendation does confirm that the front is not as cold, I'd hop up there with a can of cleaner and spray the coils/fins. I'm going to be doing mine soon with this: Amazon.com: Frost King ACF19 Foam Coil Cleaner, 19Oz, 19 Ounce: Home Improvement

As an Amazon Associate Foretravel Owners' Forum earns from qualifying purchases.
1987 Grand Villa ORED
2001 U320 4010

Not all that wander are lost... but I often am.

Re: Rooftop ac

Reply #4 –
I'm never sure which position is recirculate on our window air so I tried both with the gun. I got the idea pushing the recirculate button in the car and checking temps.

The output temp of the AC changes as the TEV opens (A thermal expansion valve or thermostatic expansion valve (often abbreviated as TEV, TXV, or TX valve) is a component in refrigeration and air conditioning systems that controls the amount of refrigerant released into the evaporator and is intended to regulate the superheat of the vapor leaving the evaporator.) so the temp can change as more refrigerant is allowed into the evaporator.

For those new to AC, ice will form and block the evaporator unless a temperature controlled valve controls the amount of refrigerant allowed by the sensor in the fins on the evaporator.

Pierce
Pierce and Gaylie Stewart
'93 U300/36 WTBI
Detroit 6V-92TA Jake
1140 watts on the roof
SBFD (ret)

Re: Rooftop ac

Reply #5 –
I cleaned my evaporator and condenser coils on both AC units in November after watching a YouTube video. They did not operate properly afterwards. My mobile RV tech fixed in five minutes. The phone like control wires were either disturbed or got some cleaner in them. Unplug, shot of contact cleaner and replug. Everything worked fine after that. Lesson learned. 1998 Duotherm units with heat strips.
1998 36 foot U270 Build No. 5328 WTFE, 900 watts solar, Victron controller, B2B, bat monitor, 600 AMPH lithium with 2018 Chevy Colorado toad, SKP #110239, Motorcade #17781, 2021 Escape 17B for when Coach is broken down and campsites are too small, retired and full-timer since Dec. 2020. Part of RV family since 1963.

Re: Rooftop ac

Reply #6 –
I found someone to charge the front ac unit.  He tapped into two separate copper lines and added freon. 
So far it is working perfectly (very cold).  I will see how long it lasts. 
It only cost me $150 so it is worth a try.
Rick & MJ Berry
1998 U320 40'
Ohio

Re: Rooftop ac

Reply #7 –
Since it is a sealed system, if you had to have it recharged, there WAS a leak.

Did they find/fix the leak?
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: Rooftop ac

Reply #8 –
No just recharged.
He mentioned about a valve that was stuck.  I'm not sure what he meant.

Rick
Rick & MJ Berry
1998 U320 40'
Ohio

Re: Rooftop ac

Reply #9 –
Quote from: 18360 –
He mentioned about a valve that was stuck.  I'm not sure what he meant.
If air conditioner is a heat pump model, then he may have been referring to a stuck reversing valve, which could impact cooling performance.
1993 U280 SE 40' WTBI, Build: 4359
C8.3 300hp, 6-Speed, Exhaust Brake
960 watts on the roof (6 x 160)
Sorento (or BOLT) on a Kar Kaddy SS
"Nature abhors a vacuum"