Adding 2nd A/C

Skippy38 · 08-24-2021, 06:15 AM

Ok, so I have decided to add a second a/c unit in the front bedroom vent spot. I have a 50amp coach and the front vent is already pre wired and has its own breaker so I am good. I have no doubt that I can install it myself. Question is...my main unit is a Dometic Brisk Air II 15k, I assume that I can get away with a 13.5k unit in front? Also, should I stay with a Dometic unit or can I put another brand up there?

Javi · 08-24-2021, 06:16 AM

Quote:

Originally Posted by Skippy38

Ok, so I have decided to add a second a/c unit in the front bedroom vent spot. I have a 50amp coach and the front vent is already pre wired and has its own breaker so I am good. I have no doubt that I can install it myself. Question is...my main unit is a Dometic Brisk Air II 15k, I assume that I can get away with a 13.5k unit in front? Also, should I stay with a Dometic unit or can I put another brand up there?

Save yourself the pain and just put another matching 15K in the bedroom..

**flybouy** · 08-24-2021, 06:27 AM

I would recommend anyone in FL, the Deep South, or in the SW desert areas to go with a matching 15K unit. As Javi said, a matching unit will save you some heartache with any interface.

Skippy38 · 08-24-2021, 06:29 AM

Quote:

Originally Posted by flybouy

I would recommend anyone in FL, the Deep South, or in the SW desert areas to go with a matching 15K unit. As Javi said, a matching unit will save you some heartache with any interface.

Thanks. The front unit will be non ducted and it is on its own 20amp breaker and prewired so it should not be hard for me to install.

**flybouy** · 08-24-2021, 07:30 AM

Quote:

Originally Posted by Skippy38

Thanks. The front unit will be non ducted and it is on its own 20amp breaker and prewired so it should not be hard for me to install.

If the unit is not “tied in’ to the controller/thermostat of the fron unit then brand isn’t critical. I would still recommend the 15k unit if you stay in the south during the summer.

Skippy38 · 08-24-2021, 07:39 AM

Quote:

Originally Posted by flybouy

If the unit is not “tied in’ to the controller/thermostat of the fron unit then brand isn’t critical. I would still recommend the 15k unit if you stay in the south during the summer.

It is not tied in, it will be a stand alone unit with its own controller. It is very hot this year, especially in July and August, so I think a 2nd a/c for next year is a must. The single a/c now can barely hold it at 85deg during the hot days so I am thinking a second unit would help greatly as I could probably run both on low and keep the rig much cooler.

**JRTJH** · 08-24-2021, 08:08 AM

I'd urge you not to consider the "Penguin" or "low height" air conditioners. They have significantly smaller air exchange boxes and the air movement makes quite a bit more noise. Some people like that "air rush" noise to sleep. Other people dislike it for the same reason. The "standard height" units don't make as much noise when operating, so if watching TV or conversation under the unit is part of the living conditions, test run a "low height unit" before you spend your money.....

I agree with the others about installing a 15K unit. Humidity control with "oversized units" (typically an issue in homes) is not a primary issue with RV cooling systems. In some conditions you might get some increased humidity, but typically, RV's are so poorly insulated that the units are going to run long enough to control humidity even if they are slightly oversized.... I don't think it's possible to install "too many BTU's" in an RV because of the poor insulation, single pane windows and air leaks around the slides and at every plumbing run through the floor.

Skippy38 · 08-24-2021, 08:22 AM

Quote:

Originally Posted by JRTJH

I'd urge you not to consider the "Penguin" or "low height" air conditioners. They have significantly smaller air exchange boxes and the air movement makes quite a bit more noise. Some people like that "air rush" noise to sleep. Other people dislike it for the same reason. The "standard height" units don't make as much noise when operating, so if watching TV or conversation under the unit is part of the living conditions, test run a "low height unit" before you spend your money.....

I agree with the others about installing a 15K unit. Humidity control with "oversized units" (typically an issue in homes) is not a primary issue with RV cooling systems. In some conditions you might get some increased humidity, but typically, RV's are so poorly insulated that the units are going to run long enough to control humidity even if they are slightly oversized.... I don't think it's possible to install "too many BTU's" in an RV because of the poor insulation, single pane windows and air leaks around the slides and at every plumbing run through the floor.

I just got done reading about the Penguin and their issues and have decided to just go with another Dometic Brisk Air II 15k unit with stand alone controller. I think that this will allow me to run both units on "Low Cool" and have a much better result next summer. Does it matter that the unit will be kind of "nose down" and not level due to the curvature of the roof in the front?

**sourdough** · 08-24-2021, 08:47 AM

Matt just wanted to concur with your decision on the 15k Brisk Air. I installed a 13.5k non ducted Penguin on our last trailer (32' box) in the bedroom. It is a bit louder than the full profile units but we are some of those that like the noise at night and in the daytime it didn't matter "in the other end". The 13.5 worked well with the use of a fan on the dresser pushing the non ducted cold air out into the living area; you will likely have to do the same thing or the bedroom becomes a meat locker.

That front vent is wired and prepped for a 2nd AC with the existing slope. I'm not aware of it causing a problem from an OE design perspective and have seen lots of them, including one for sale on RV trader that I looked at this morning. I wouldn't hesitate to put it up there....you'll be glad you did.

Skippy38 · 08-24-2021, 08:53 AM

Quote:

Originally Posted by sourdough

Matt just wanted to concur with your decision on the 15k Brisk Air. I installed a 13.5k non ducted Penguin on our last trailer (32' box) in the bedroom. It is a bit louder than the full profile units but we are some of those that like the noise at night and in the daytime it didn't matter "in the other end". The 13.5 worked well with the use of a fan on the dresser pushing the non ducted cold air out into the living area; you will likely have to do the same thing or the bedroom becomes a meat locker.

That front vent is wired and prepped for a 2nd AC with the existing slope. I'm not aware of it causing a problem from an OE design perspective and have seen lots of them, including one for sale on RV trader that I looked at this morning. I wouldn't hesitate to put it up there....you'll be glad you did.

Thanks Danny, that is exactly what I needed to know.

wiredgeorge · 08-24-2021, 09:13 AM

Quote:

Originally Posted by Skippy38

I just got done reading about the Penguin and their issues and have decided to just go with another Dometic Brisk Air II 15k unit with stand alone controller. I think that this will allow me to run both units on "Low Cool" and have a much better result next summer. Does it matter that the unit will be kind of "nose down" and not level due to the curvature of the roof in the front?

An RV A/C can freeze up if the unit is placed on Low Cool and the lower fan speed. I did this once with a Brisk II by running it on the lower cool setting and low fan thinking to keep our camper from becoming real hot when not used for a few days. I went in and had a chunk of ice that will drip all over the floor when it melts. The easiest way to clear it is to shut off the A/C and just run it on fan at the highest speed.

**JRTJH** · 08-24-2021, 11:25 AM

I agree with Danny. I can't think of any trailer with a "nose roof" that sloped too much for a rooftop air conditioner. I think that's no problem at all... The only issue I can think of hearing as a complaint is the "moisture trail stain" from the front unit. There's no drip rail along the front cap to catch the condensation and direct it to the trailer sides, so there's likely going to be a "dirty streak down the middle of your front cap. Otherwise, no problems with the slope.

As for running the air conditioners (note two units) on low shouldn't be a problem. Typically, it's a "one unit trailer being run on low" that can't remove enough humidity through the evaporator coils and the excess humidity freezes on the fins causing an "ice block". With two air conditioners, both running on low, typically the humidity is low enough that it doesn't overwhelm either unit and ice buildup isn't a problem....

That said, your trailer might be that "one in a hundred" that does have ice buildup when both are running on low fan speed. If that happens, try turning the unit in the space where you aren't at to high and leave the one in the room where you are on low. That way you avoid most of the noise and still remove the humidity preventing a freezeup. There's lots of "individuality" in the way owners use their rigs. Just install a good unit and experiment with what works best for your lifestyle. I wouldn't expect a problem with repeated icing of the evaporator coils in most RV's with two A/C units, both on low. But then again, anything "can" happen, given the right circumstances. If it does, then address it, but until then, do what is most comfortable for the moment LOL

Skippy38 · 08-24-2021, 12:34 PM

Quote:

Originally Posted by JRTJH

I agree with Danny. I can't think of any trailer with a "nose roof" that sloped too much for a rooftop air conditioner. I think that's no problem at all... The only issue I can think of hearing as a complaint is the "moisture trail stain" from the front unit. There's no drip rail along the front cap to catch the condensation and direct it to the trailer sides, so there's likely going to be a "dirty streak down the middle of your front cap. Otherwise, no problems with the slope.

As for running the air conditioners (note two units) on low shouldn't be a problem. Typically, it's a "one unit trailer being run on low" that can't remove enough humidity through the evaporator coils and the excess humidity freezes on the fins causing an "ice block". With two air conditioners, both running on low, typically the humidity is low enough that it doesn't overwhelm either unit and ice buildup isn't a problem....

That said, your trailer might be that "one in a hundred" that does have ice buildup when both are running on low fan speed. If that happens, try turning the unit in the space where you aren't at to high and leave the one in the room where you are on low. That way you avoid most of the noise and still remove the humidity preventing a freezeup. There's lots of "individuality" in the way owners use their rigs. Just install a good unit and experiment with what works best for your lifestyle. I wouldn't expect a problem with repeated icing of the evaporator coils in most RV's with two A/C units, both on low. But then again, anything "can" happen, given the right circumstances. If it does, then address it, but until then, do what is most comfortable for the moment LOL

Thanks John! Dirty streaks dont bother me a bit, gives me something to clean off lol

Javi · 08-24-2021, 01:22 PM

Generally speaking LOW SPEED is not in my vocabulary with temps in he high 90's and humidity at 75% plus.

I leave both on HIGH and let them cycle. When it cools down in the evening and we're ready for bed I'll bump the downstairs unit up a few degrees and put the bedroom unit on about 65... we like it cool to sleep.

JRK · 09-05-2021, 07:36 AM

We changed ours to ducted and being in the In Command! Was too loud in stand alone. Being in In command it allows us to set the AC front and back so that the bedroom one doesn't come on as often. Makes a difference when camping in 99 with heat index 107. Also try keeping front of trailer so it gets the lest amount of sun as the front cap on Cougar 5th wheels isn't insulated.

rlh1957 · 09-05-2021, 08:12 AM

Keystones that are 50A with optional additional AC usually are ducted and ducting is inner connected. That way you can run either or both ac’s to cool.
A 13.5btu AC in bedroom alone would really chill it if non ducted.
Mine really helps boost the 15K for the whole RV on super hot days.

If you have the In-Command system you have to not only have the Dometic AC unit but the gateway and controller to integrate the two AC zones through the In-Command.
They are individually controllable.

You can still choose to connect it without using a gateway to integrate with the In-Command and hooking to it’s own stand alone thermostat. Instructions come that way. It would still dump into the inner connected ductwork.

Only difference I see is the bedroom AC wouldn’t be controllable from In-Command screen or mobile phone. You just go to the second AC thermostat in bedroom to change settings.
Going Dometic AC & controller to Dometic wall thermostat is a little easier and cheaper than the extra components needed for In-Command.

If I had my choice I’d prefer a regular switched control center for everything and not the integrated electronic computer giz of In-Command system.

Domino3665 · 09-05-2021, 08:25 AM

Before you add the 2nd A/C unit, do THIS.
Inspect the duct connection at the main A/C unit. Your rig is old enough that the adhesive on the tape holding the ducts to the A/C has let go a bit and you are most likely pouring cold air into the rafter area and not as much into your forward bedroom.
There are YouTube videos describing this condition. It is an EASY FIX.
I had this issue in my 309 Springdale. The results could make you change your mind about a 2nd A/C unit.
BTW: Are you thinking you are going to sleep with the noise from an A/C unit running right over your head?

skmct · 09-05-2021, 08:48 AM

Skippy I would consider the height issue. I went with a 13.5k low profile to keep the hight down. We we live in south fl . And have camped all over the country Seen Temps over 110 f in the high deserts out west and never had a problem keeping our fifth wheel cool. As long as both units could be run together. When on 30 amp service you can only run one. I don't know what size your rig is or where you travel but I would keep height in mind when adding a ac to the front of a fifth wheel. I know low profile cost more but consider the cost if it's left behind at a under pass.

rlh1957 · 09-05-2021, 09:59 AM

Yes definitely will want to get the silver tape for HVAC Duct work and re-tape all factory joints and seal the air gaps they left.
If you look at YouTube there are many tips on sealing air leaks as well as quieting the AC some.
There are AC quiet kits but get up in price. Watch You Tube and you can make your own.

jsmiller47 · 09-05-2021, 10:50 AM

I bought a 23.5K Coleman Mach 10 NDQ Ductless Ultraquiet AC for our 2020 Cougar Half-Ton Travel Trailer in the bedroom. IT IS MUCH QUIETER THAN THE DOMETIC IN THE REAR. You can install a thermostat control in the bedroom or if your ceiling is low like ours you can control it manually. They also make a 600 watt heat strip that installs inside of the ceiling unit. An optional ceiling unit has Bluetooth, but it has problems connecting to our phone. The Coleman also comes in a model with Soft Start installed. Important if you use a generator. Going ductless simplifies the install. The bedroom unit is not integrated with the controller upfront. We had it installed locally by an independent RV repair company. It has worked out very well.

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