Thinking of replacing AC

etu · October 2, 2023

Considering replacing my AC. Current one is 13.5k btu and considering upgrading to 15k.
would really like a quieter one. Who makes the best? My current one has a 3 wire thermostat, is that common?

Kirk W · October 2, 2023

There are a lot of different RV thermostats available. There are a lot of RV thermostats available from Amazon and others so you do need to pair them properly. If you just upgrade to a larger capacity air conditioner of the same make and model that you have now it should work. Do you plan to do the work yourself? If not you need to be sure that you have a reliable RV tech to do the work.

TXiceman · October 2, 2023

It would help to know the make and model of the A/C you currently have.

Ken

etu · October 2, 2023

Thanks Kirk and Ken,

I just learned today my current ac is 15k btu so it should be doing a better job of cooling. It’s a Dometic B59516.711J0. product number 9360
Got a mobile RV Refrigeration & Air Tech coming tomorrow to check it out. I’ll post what I find out tomorrow.

Wrknrvr · October 3, 2023

Are the filberts clean. Are the fins clean.

Tell the Mobile rv tech to bring materials along to clean the fins.

have the tech check if any duct work is leaking anywhere.

Also check the temperature differences from room air to the conditioned air.

Edited October 3, 2023 by Wrknrvr

etu · October 3, 2023

I’ve cleaned the coil and the fins. I also sealed all the ducts. Every air outlet was poorly sealed to the duct work and had cold air leaking into the roof space. Now i have real good airflow even in the bedroom at the opposite end of the system. Had to do same thing with my previous camper. I’m convinced air ducts are one of the most poorly installed components in a camper.

Kirk W · October 3, 2023

What you found is not uncommon and more so with some brands/models than others. You haven't mentioned what your RV is or the age which could also play a part. If the RV isn't new you might want to check both coils, one in the air flow and the other on the roof. You may find this video to be helpful. RV AC Coil & Filter Cleaning If you have not done so, look for places that outside air could be getting into the RV as well and plug them with some expanding foam or similar product.

jbh · October 3, 2023

About 20 degrees below ambient is about all that should be expected because RVs generally have very little insulation and large windows.

TXiceman · October 3, 2023

5 hours ago, jbh said:

About 20 degrees below ambient is about all that should be expected because RVs generally have very little insulation and large windows.

That is an internet false tale. It is 20 degrees across the evaporator at the A/C unit. Related to the outside temperature, it is all about insulation and radiant load.

We had a HitchHiker Champagne that we had in full sun in New Mexico at 109 degF and could maintain 77 degF in the trailer and the A/Cs were cycling a bit. That us 32 degF lower than thew ambient. It was a true 4-season trailer, not a 3- season with a meanuingless "Polar Pak" sticker.

Ken

etu · October 4, 2023

Update. First, our camper is a 2016 cougar 303rl (33’ long). It has one 15k btu Dometic B59516 ac in the kitchen/ rear living area.
Had the Refrigeration/HVAC mobile tech come today. Fins and coils are clean and the best we could get is 16-17 degree differential between return air and cold side. Went ahead and changed out the control kit including thermostat but didn’t make any difference.
He said the unit behaves as if it’s low on charge but the cost of 410 and installation of ports don’t justify the cost (~$500) that could go towards a new unit with 2 year warranty.
We have a trip planned in 2 weeks in the north Ga mountains and cooler weather. I think I’ll wait until we get back from that trip to replace the AC.

I guess if I go with Dometic all the lower(interior) components are plug and play. If I go with another brand I’d have to replace the lower unit as well.
I’m leaning towards replacing the upper with the Dometic and do it myself but I’ll need to think about that and see some videos before I decide.

Kirk W · October 4, 2023

On 10/2/2023 at 6:25 PM, etu said:

It’s a Dometic B59516.711J0. product number 9360

That would be a DuoTherm B59516 Brisk Air II and this is a service manual. If you measure the air temperature as it enters the unit and then the air leaving the unit, the temperature should decrease by 18° to 24° so yours is below what it should be but not by a lot. A 33' travel trailer is a lot to try and cool with only 1 air conditioner.

etu · October 4, 2023

Thanks Kirk. Mine must be newer than that manual covers, mine has r410 refrigerant and 3 wire thermostat.

etu · October 5, 2023

Ok new ac options have been narrowed down to Dometic FreshJet FJX3573.
This is a 15k BTU model that should be compatible with my existing internal air distribution box, ducts and control kit. Should be “plug and play” according to the tech.
Based on all I’ve read and reviewed I think I’ll do the install. I’ll let y’all know how that goes in another month or so.

One thing that gets me is, why didn’t the manufacturer put refrigerant ports on these things? If I had ports I could top off the charge on my existing units and enjoy cold air.
How much could it add to the cost to put ports on compared to the crimping and welding they had to do to to seal the lines once they charged the unit?

D&J · October 5, 2023

On 10/3/2023 at 9:50 PM, etu said:

Update. First, our camper is a 2016 cougar 303rl (33’ long). It has one 15k btu Dometic B59516 ac in the kitchen/ rear living area.
Had the Refrigeration/HVAC mobile tech come today. Fins and coils are clean and the best we could get is 16-17 degree differential between return air and cold side. Went ahead and changed out the control kit including thermostat but didn’t make any difference.
He said the unit behaves as if it’s low on charge but the cost of 410 and installation of ports don’t justify the cost (~$500) that could go towards a new unit with 2 year warranty.
We have a trip planned in 2 weeks in the north Ga mountains and cooler weather. I think I’ll wait until we get back from that trip to replace the AC.

I guess if I go with Dometic all the lower(interior) components are plug and play. If I go with another brand I’d have to replace the lower unit as well.
I’m leaning towards replacing the upper with the Dometic and do it myself but I’ll need to think about that and see some videos before I decide.

First if I could get 500 to install a access valve I would come out of retirement.

When he checked the temp differential did he do it at the return vent and the first outlet or did he take the time to check it at the units out at the blower. If it was at the first outlet then your unit is working properly. To double check go up on the roof and remove the cover then start the unit and give it a good 30 minutes to balance out. Go back on the roof and you will see 2 lines coming out of the compressor and see if the bigger line is sweeting, if it is feel it and it should be what I call beer can cold. Don't touch the other small line because it will be very hot. If it's not sweeting it's either short if gas or the compressor is bad.

The thermostat and control box has nothing to do with how cold the air is coming off the coil, it just turns it off and on. Unless you have a freeze control that has failed it would turn the compressor off not the fan.

They don't put access valves on RV ac units because it's a point to leak and these units use so little gas that putting a gage set on it just a few times would make the unit short of gas.

It doesn't matter what gas it has in it all refrigeration works the same just at different pressures.

Your unit has R410A and in my experience it takes longer to balance out over R12, R22, R 134A so give it sine time.

I'm really afraid you may change the unit and still have the same problem. But it's your money.

Denny

TXiceman · October 5, 2023

On 10/3/2023 at 12:22 PM, jbh said:

About 20 degrees below ambient is about all that should be expected because RVs generally have very little insulation and large windows.

That is an internet false tale. It is 20 degrees across the evaporator at the A/C unit. Related to the outside temperature, it is all about insulation and radiant load.

We had a HitchHiker Champagne that we had in full sun in New Mexico at 109 degF and could maintain 77 degF in the trailer and the A/Cs were cycling a bit. That us 32 degF lower than thew ambient. It was a true 4-season trailer, not a 3- season with a meaningless "Polar Pak" sticker.

Next issue is you cannot use an infrared temperature sensor (laser gun) to read air temperature. Infrared sensors read radiated heat from a solid surface. If you use the infrared sensor, it will read the temperature of the vent or duct work.

Here is an article telling you why. infrared snesors

Ken

etu · October 5, 2023

Thanks Denny,

We removed the filter grid and checked temps as the air entered the evaporator coil fins. Our Air Distribution Box has an option to open and direct air flow from the blower immediately below the unit before going into the duct work. That’s where we measured cold side air. Our check points were close to the warm air return and the cold air out as you can get.

We used a magnetic mount digital thermometer to allow the thermometer to stay in place as long as necessary to get stable measurements.

We replaced the control box and thermostat because on last camping trip the unit had repeatedly failed to restart after room temp has exceeded set point by 10 degrees or more. (We’d leave the camper early in the morning while outside and inside temps were around 67 and set the ac to auto at 72 degrees. When we retuned late afternoon (outside temps around 82), the air temp inside the camper was around 84 and the ac had never cut on)

In those cases I had to switch the ac to off, reset CT thermostat to - -, then reset to auto ac at 72 degrees. Then the unit would immediately cut on, cool to the set point, drop from high to low and then shut off as normal. However it would not start back up unless I reset as described above. I replaced the CT thermostat but that did not help. So we replaced the control box in hopes it would solve that problem

After we replaced the control box and with a new CT thermostat we rechecked the air temps and there was no difference from the temps we checked initially. The tech then said it indicted low charge and recommended replacing the AC.

Perhaps you can tell me, why don’t they use R134 in these units.

D&J · October 5, 2023

They don't use R134A because it's not a good high temp gas and R410A was designed to be a A/C gas to replace R22 that's now one of the refrigerants phased out by the EPA. You will also see R134 phased out in the coming years and be replaced by R1234YF in automotive units.

Like I said check the suction line at the compressor before condemning the unit.

Denny

lappir · October 6, 2023

I've waited to respond for a while.

I had to replace my HVAC unit after a very short life. It wasn't a Roof Top model, but a "Basement" unit, but since I upgraded to an LG Mini Split system. I have much less power use, 90% quieter most of the time and so far several years of trouble free use.

I think they are getting to be a standard for both New Horizons and Spacecraft semi custom and full custom builders in the Midwest. Contact them to be sure.

Rod

Kirk W · October 6, 2023

19 minutes ago, lappir said:

I upgraded to an LG Mini Split system.

How does the cost of the Mini Split compare to the typical rooftop units? ls anyone still installing the basement air in new RVs?

lappir · October 6, 2023

58 minutes ago, Kirk W said:

How does the cost of the Mini Split compare to the typical rooftop units? ls anyone still installing the basement air in new RVs?

Kirk,

My first trailer had roof tops. I chose to have nothing on my roof with my custom build. I was told the Basements were more quiet and would preform well. I saw a few in Motorhomes in my earlier searches and the Owners said they were great (they were also trying to sell the Motorhome to me.)

The unit never worked well. It was quieter and if the temperatures were not too extreme it was tolerable and then it broke and was non repairable. I still didn't want "Holes cut into my roof" so I chose to go the Mini Split at around 10K installed as a retrofit (more costly).

I don't know what the price difference is on a new build.

Rod

ogaddcb · October 7, 2023

We installed a RV Air Conditioner 15K Quiet AC Unit with Heat Pump, Remote Control RP-AC3800-W-KT on our trailer about two years ago. Can’t tell you how impressed we are with this unit. Yes expensive but the interior noise difference is significant and we have used the heat pump portion of the AC in 20 degree weather with no problems. Bought ours at this link

jamtracy · October 9, 2023

Are you 50 amp pre-wired for a second AC? If so that is what I would do. I added a 3rd AC to our rig and what a difference. It's is a RECPRO brand non ducted with remote. They do make ducted units. Now inside the rig doesn't know it's 110 outside.

lappir · October 9, 2023

A guy parked next to me at the HDT Rally has a Mini Split 12 volt added to the back of his Volvo. He either said $500 or $700 installed a few years ago, and it works great. A/C went out in the truck and instead of $XXXX he went with $XXX. I'll post a photo of it later. (The ODU). He commented that the Mr. Cool is similar and with their "Charged" lines an easier install. May won't to add that to the Pro/Con list.

Rod

GlennWest · October 11, 2023

All I have used for years are mini splits. Upgraded to that and never want another roof top rv unit.

etu · October 22, 2023

On 10/3/2023 at 9:50 PM, etu said:

Update. First, our camper is a 2016 cougar 303rl (33’ long). It has one 15k btu Dometic B59516 ac in the kitchen/ rear living area.
Had the Refrigeration/HVAC mobile tech come today. Fins and coils are clean and the best we could get is 16-17 degree differential between return air and cold side. Went ahead and changed out the control kit including thermostat but didn’t make any difference.
He said the unit behaves as if it’s low on charge but the cost of 410 and installation of ports don’t justify the cost (~$500) that could go towards a new unit with 2 year warranty.
We have a trip planned in 2 weeks in the north Ga mountains and cooler weather. I think I’ll wait until we get back from that trip to replace the AC.

I guess if I go with Dometic all the lower(interior) components are plug and play. If I go with another brand I’d have to replace the lower unit as well.
I’m leaning towards replacing the upper with the Dometic and do it myself but I’ll need to think about that and see some videos before I decide.

I owe y’all a belated update. Even though I had cleaned the coil with water I went ahead and cleaned the roof top coil with a professional grade coil cleaner. It foamed up like shaving cream and boiled out a lot of dark residue. I repeated the cleaning and now I’m getting 18-20 degree differential.
unit cycles on and off after replacing the control kit so I’m ok I think.
thank you for all the advice and replies.