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Roof Top AC/Heat Pump


SuiteSuccess

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I have Dometic 15,000 BTU ac/heat pump in living area in my Mobile Suites.  AlsoDometic 13,500 ac as second unit in bedroom.  Both are ducted with a common plenum.  The 15,000 is not cooling as well as previously but it's also ten years old. Bedroom unit fine so far.  I know you can pierce the line and add a charge port but probably just going to replace both units due to age.  Question is recommendations for replacement.  Dometic or Coleman? Or is there something better (could minisplits be retrofitted?)

2006 Volvo 780 "Hoss" Volvo D12, 465hp, 1650 ft/lbs tq., ultrashift

Bed Build by "JW Morgan's Custom Welding"

2017 DRV 39DBRS3

2013 Smart Passion Coupe "Itty Bitty"

 

"Don't go around saying the world owes you a living. The world owes you nothing. It was here first!"

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14 minutes ago, SuiteSuccess said:

The 15,000 is not cooling as well as previously but it's also ten years old. Bedroom unit fine so far.  I know you can pierce the line and add a charge port but probably just going to replace both units due to age.

Technical Trivia:  "If" an air conditioner is losing coolant (freon) the temperature across the evaporator will drop.  If too much coolant is lost the evaporator will freeze.  The thought-set of adding freon to an air conditioner that has the correct charge to make it cool better is wrong.  Those bolt on clam shell piercing valves are only temporary.  They are good for removing and recovering freon from a questionable system rather than just opening it to the atmosphere and that is about it.  They should be considered temporary as they will leak - not may but will.  Both the condenser (outside) and evaporator (inside) of RV roof mounted air conditioners get really dirty.  This will reduce air flow and efficiency.  Before tossing your units try cleaning them.  Outside - remove cover, spray Simple Green or other cleaner that will not damage your roof into the coils.  Rinse with garden hose to flush out dirt.  Inside - cover floor under AC unit.  Clean coil with a foam no-rinse cleaner like this one.  There are dozens available and they all work well.  Cleaning will often return your AC to top operating condition.  I do my units every year. 

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Randy, Nancy and Oscar

"The Great White" - 2004 Volvo VNL670, D12, 10-speed, converted to single axle pulling a Keystone Cambridge 5th wheel, 40', 4 slides and about 19,000# with empty tanks.

ARS - WB4BZX, Electrical Engineer, Master Electrician, D.Ed., Professor Emeritus - Happily Retired!

 

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My bedroom unit compressor fan went out. 14 years old. Didn't want to throw good money on it. Installed a mini split AC/heat pump. Super quiet and cools great. Works so good I want a second one and do away with roof units. I have a detailed post on here with link to pictures. 

 

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9 hours ago, RandyA said:

Outside - remove cover, spray Simple Green or other cleaner that will not damage your roof into the coils.  Rinse with garden hose to flush out dirt.

Just make sure to flush all Simple Green away.  It is pretty corrosive to aluminum.

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4 hours ago, bobsallyh said:

rickeieio, get a jug of Extreme Simple Green made for aluminum and the aircraft industry. Available at Fastenal, stocked in some stores, or they can order it for you.

Thanks for the tip. I had some leak onto a toolbox once and it made a mess of the lid.

KW T-680, POPEMOBILE
Newmar X-Aire, VATICAN
Lots of old motorcycles, Moto Guzzi Griso and Spyder F3 currently in the front row
Young enough to play in the dirt as a retired farmer.
contact me at rickeieio1@comcast.net

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If the unit in question is an AC/Heat pump, I would suggest having the reversing valve in the compressor system checked to see if it is working properly. Ours recently went out in the heating mode, thus not allowing the opposite direction on flow in the freon needed to cause the freon to cool rather than heat the air flowing through the a/c coil. Unfortunately, the barely four year old unit had to be completely replaced with a new one since this valve assembly is not removable and/or replaceable. Apparently this is a typical cause of a/c failures at the beginning of the season change from cool to hot.

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Thank you everyone for the replies.

2006 Volvo 780 "Hoss" Volvo D12, 465hp, 1650 ft/lbs tq., ultrashift

Bed Build by "JW Morgan's Custom Welding"

2017 DRV 39DBRS3

2013 Smart Passion Coupe "Itty Bitty"

 

"Don't go around saying the world owes you a living. The world owes you nothing. It was here first!"

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On 5/22/2017 at 10:00 PM, jkoenig24 said:

Randy, thanks for that link. I need to clean my roof units. Will one can do one AC unit?

Yes

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Randy, Nancy and Oscar

"The Great White" - 2004 Volvo VNL670, D12, 10-speed, converted to single axle pulling a Keystone Cambridge 5th wheel, 40', 4 slides and about 19,000# with empty tanks.

ARS - WB4BZX, Electrical Engineer, Master Electrician, D.Ed., Professor Emeritus - Happily Retired!

 

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I agree with most of what's been posted already--if the compressor is still running, there's not much reason to replace the whole thing.  It should be able to be brought back to the same mediocre, noisy operation as when brand new. ;-)

At least on the Coleman air conditioners, I find it easier to clean the evaporator coils from up on the roof.  Taking out a handful of screws, you can open up the plenum from the top, and clean the coils without standing under them.  And now that I think about it, your RV has ducted air returns, so that would be your only option anyways, short of unbolting the whole thing.

One other thing to check, if the Dometics are like the Colemans, is the placement of the blower wheel on the motor shaft.  They're just held in place with a set screw, and if the wheel slides away from the evaporator towards the motor, you won't get as much air flow.

45' 2004 Showhauler -- VNL300, ISX, FreedomLine -- RVnerds.com -- where I've started to write about what I'm up to

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Thanks David.  Hope your grandpa is doing well.

2006 Volvo 780 "Hoss" Volvo D12, 465hp, 1650 ft/lbs tq., ultrashift

Bed Build by "JW Morgan's Custom Welding"

2017 DRV 39DBRS3

2013 Smart Passion Coupe "Itty Bitty"

 

"Don't go around saying the world owes you a living. The world owes you nothing. It was here first!"

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50 minutes ago, SuiteSuccess said:

Thanks David.  Hope your grandpa is doing well.

Lots better.  Discharged to a rehab facility Tuesday, and getting 3 hours of therapy every day now.

45' 2004 Showhauler -- VNL300, ISX, FreedomLine -- RVnerds.com -- where I've started to write about what I'm up to

Headlight and Fog Light Upgrades http://deepspacelighting.com

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  • 3 weeks later...
4 hours ago, Pete Kildow said:

Have a question to go along with this post. How often should be be cleaning the units on top of the RV? And any issues with water getting inside with the top off the unit?

Thanks in advance.

Pete

Hey Pete - When you need to clean is going to be dependent on how much you run the AC and how dirty the environment is.  I clean mine every Spring when I do annual maintenance - you know, wheel bearings, wet bolts, roof clean, etc.  It is just part of the never ending list of what I need to do to keep things working right.  Since we snowbird to Florida in the winter months I use the two AC units in our trailer pretty much year round.  No issues with water getting inside with the shroud off.  I don't spray water directly into the evaporator from the roof.  Wash the condenser, clean out the drains, hope the wasp nest is empty.

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Randy, Nancy and Oscar

"The Great White" - 2004 Volvo VNL670, D12, 10-speed, converted to single axle pulling a Keystone Cambridge 5th wheel, 40', 4 slides and about 19,000# with empty tanks.

ARS - WB4BZX, Electrical Engineer, Master Electrician, D.Ed., Professor Emeritus - Happily Retired!

 

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I use a "Coil cleaner"  https://www.amazon.com/dp/B0026SIJ52/ref=asc_df_B0026SIJ525023053/?tag=hyprod-20&creative=394997&creativeASIN=B0026SIJ52&linkCode=df0&hvadid=167141040944&hvpos=1o4&hvnetw=g&hvrand=10451125976427483541&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9020955&hvtargid=pla-315047075732 on inside and outside.

Outside I remove the shrouds, spray the cleaner and rinse.  On the interior, I remove the grill and on our AC's I remove the control assembly- older Carrier models.  I cover the area- shove some towels into the area duct area and spray the cleaner onto the coils, the turn the unit on.  The condensation on the interior coils rinses the cleaner off.  If I'm careful enough I don't make a mess and get fussed at.....

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Did clean both units. Really not all that dirty.   Both working fairly well now. Guess you can teach an old dog new tricks but finally figured out that since we have a common plenum and ducting, running both ac units at the same time makes it much more comfortable. We had only been running the area we were occupying. 

2006 Volvo 780 "Hoss" Volvo D12, 465hp, 1650 ft/lbs tq., ultrashift

Bed Build by "JW Morgan's Custom Welding"

2017 DRV 39DBRS3

2013 Smart Passion Coupe "Itty Bitty"

 

"Don't go around saying the world owes you a living. The world owes you nothing. It was here first!"

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Carl, They have this new thinggie called a thermostat. It is a wonderful device that will turn things on and off Automatically according to the temp in that area. We leave both on all the time.

I have found that I set the bedroom temp a little colder than the living room. That way the BR unit will run more and give the LR unit a break. 

See ya in Hutch.

 

Brad

Brad and Jacolyn
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On ‎5‎/‎23‎/‎2017 at 5:15 PM, Gary Hage said:

If the unit in question is an AC/Heat pump, I would suggest having the reversing valve in the compressor system checked to see if it is working properly. Ours recently went out in the heating mode, thus not allowing the opposite direction on flow in the freon needed to cause the freon to cool rather than heat the air flowing through the a/c coil. Unfortunately, the barely four year old unit had to be completely replaced with a new one since this valve assembly is not removable and/or replaceable. Apparently this is a typical cause of a/c failures at the beginning of the season change from cool to hot.

The reversing valve is not economical to replace. However, there is a solenoid that operates the valve, and it can be replaced for about $35 IF YOU KNOW IT'S THERE. Even a RV repair shop didn't know about it, wanted me to buy a new unit.

I don't think so. If a "moderator" approves this post, you'll see it. Apparently I am censored.

2000 Volvo 635 A/S, N-14 Cummins
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On 6/9/2017 at 9:18 PM, RandyA said:

Hey Pete - When you need to clean is going to be dependent on how much you run the AC and how dirty the environment is.  I clean mine every Spring when I do annual maintenance - you know, wheel bearings, wet bolts, roof clean, etc.  It is just part of the never ending list of what I need to do to keep things working right.  Since we snowbird to Florida in the winter months I use the two AC units in our trailer pretty much year round.  No issues with water getting inside with the shroud off.  I don't spray water directly into the evaporator from the roof.  Wash the condenser, clean out the drains, hope the wasp nest is empty.

Thanks, I know ours had been cleaned 1 time. Its a 2012 but sat for the first 9 months. And only used one time last year. Parked under a roof when not being used. Keep filters cleaned and wil wash the condenser and drains next week. 

AS for Wasp, I applied screen to all openings on my cover. Used caulk to stick the screen to it. AS here in West Tn, wasp and dirt Daubers fill everything up in a few days..

Pete

 

 


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I cleaned my coils with an envioremently safe product and got good results. They did not tell me to wash all the cleaner out of my coils so it kept cleaning every time the ac ran and stopped up the drains thus poring condensation into the rig. Make sure the drains are open and the cleaner is washed out is my advice.

Take care JB

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