Replacing Duo-Therm AC unit

[Froadin]

Well, I am pretty sure my AC unit is on it's way out.
I have a Duo-Therm 13.5k ducted unit on my 5ver, and I was looking at replacing it with the Coleman 13.5 (actually 13.7k) Mach 3 PS (power saver) unit.
I like the lower power consumption, and the slight increase in cooling (anything will make a HUGE difference compared to the current unit right now).
Do I have to replace the inside piece as well as the main unit on top? I see they sell them seperately, and was wondering if that was for 'new' installs. Or if they are required even if I have a unit in place.

Anything else I should be aware of before I get this AC unit?

[Froadin]

Well, I am pretty sure my AC unit is on it's way out.
I have a Duo-Therm 13.5k ducted unit on my 5ver, and I was looking at replacing it with the Coleman 13.5 (actually 13.7k) Mach 3 PS (power saver) unit.
I like the lower power consumption, and the slight increase in cooling (anything will make a HUGE difference compared to the current unit right now).
Do I have to replace the inside piece as well as the main unit on top? I see they sell them seperately, and was wondering if that was for 'new' installs. Or if they are required even if I have a unit in place.

Anything else I should be aware of before I get this AC unit?

[RV Wizard]

Froadin, since you are wanting to swtich manufacturers, you will need to replace not olny the roof and ceiling assmy; you will also have to replace the thermostat that will be compatible with the Mach 3 PS and the heating system you have. Are you going to do the work yourself? Make sure the wiring from T'stat is compatible as well. What T'stat did you previously have? Good luck and keep us posted.

[Froadin]

JUNK wall tstat for AC and furnace.
It looks like it's common to use a remote setup when using it on the ducted setups.

I was also looking at the Carrier 15k unit that only uses like 13.5 amps (maybe 14.5 amps).
This would give me a bit more cooling for about the same power I use now (or less even!).

Still not sure why they put a 13.5k AC unit on a 37' trailer! That and the 30 amp service make life a real pain sometimes.

[Ray,IN]

Your thoughts to buy a 15K unit are right. If you desire to add a 2nd unit in the bedroom vent opening it is do-able with 30A service. My last 5er came pre-wired for a 2nd unit, and a 3-way switch on the ceiling beside the main A/C. This switch allowed me to select which unit to run. Another, and I think better idea, is to run the wiring down into the basement, and install a receptacle box for plugging in a heavy extension cord from the power pedestal. This allows the use of both if the 30A and 20A outlets are on separate circuits, or opposing legs of the 50A receptacle.

[Froadin]

Good idea on running the power separate for a 2nd AC.
Went and looked at my ac, it is the Duo-Therm Brisk Air, High Efficiency 13.5 unit. Only around 10 amps.
Thing is, this trailer spent 2 years on the gulf coast before I bought it, so the AC unit is rust and oxidation holding hands. Evap coil is freezing up, and there isn't that much restriction in the system (it's ducted, they are ALL restricted to a point.) All ducting is open and in perfect condition.
Evap coil looks pretty clean. Cleaned a little dust and hair off the front of it. But not too much.
Took the top of the unit off to look at the evap coil from above, looked clean enough, but it was frozen into a solid block of ice!
When I turn the unit on, the air at any vent is 15 to 20 degrees cooler then inside temps. And it's only in the mid 80s outside (I am in the sun though right now, and can't move).

I was looking at Duo-Therm's website, and their Brisk Air 15k unit only takes 14.7 amps, and I think I can use my same setup (meaning I only have to buy the top unit).
That would save me a chunk of money!
Question, is there anything in the ceiling fixture part of this that wouldn't work with the 15K unit?
And is that digital stat worth it? My old one isn't very good about turning on/off like I think it should.

[RV Wizard]

There are two ways to buy the same top section of these a/c's. You will have to decide which t"stat system you want to use. once you decide then order the pacakge that matches.

[Froadin]

Odd how timing works out sometimes.
Friday I put in an order for the Duo-Therm Brisk Air 15k unit from the semi-local RV service place.
Saturday morning I went to start the unit, the freon pump started up perfectly, but the fan motor started up VERY slowly. I quickly turned it off, put the temp up to max and just turned the fan on. It started to slowly turn again, obviously a very unhappy motor.
I wait a few minutes, check the breakers, and try the fan switch again, CLICK and nothing. Zero fan movement.
Climb on top the 5ver and I can easily spin the fan on top, so it's not frozen.
I wait a longer period, and try again. Nothing but a click for the fan.
The motor is DEAD.

I guess this explains how all the vents were open and in great shape, the evap coil was clean, I was getting a 20 degree drop typically, but hte coil was freezing.
Not enough air flow because the fan motor was dying.

Please note, there is not much worth saving on this AC unit. It sat exposed to salt air for a couple years before I got it, so the condenser coil was rotting at the bottom, many of the metal parts had mild to wild rust. This thing ran constantly on the gulf coast (south Padre I think). So there was no real use in trying to repair this unit.

I guess I never really noticed the declining performance of the fan motor because it was a slow death.
I knew it didn't blow as much after it ran for a while, but I chalked that up to the evap coil freezing and blocking off the air flow.

Picked up the 15k unit last night. Weather permitting, I will install the unit today or tomorrow.

[Froadin]

The hardest part of this install was getting that sucker up onto the roof!
Another good thing about doing this, one of the only ways to see what the ducting looks like directly under the unit is by lifting it off. And I guess I had been air conditioning my ceiling some through one fairly decent sized gap.

Taped it up (with the aluminum tape), set the unit down, squared it up and bolted it on.
Overall, a LOT easier then I expected, even though I didn't expect a real big deal.

Plugged in the one and only wire/plug needed. hooked the 5ver back up to AC, and fired the AC up. And it blows a LOT of air now!!! Woo hoo!
I still need to seal up the barrier between the intake and ducting, which I can do tomorrow now that it's all inside work.

No real test of how well it works, we just had a decent storm blow in, and it's 50 degrees right now.

One odd thing, the previous 13.5 unit had a sensor that went to the side of the evap coil. It went on one of the small bent tubes. I guess it was the sensor for when it freezes.
Well, there is no where on the new unit to put this one now. The 15K unit shows having a probe style sensor rather then my clip on one from before.

Other then that, everything from the previous smaller unit worked perfectly with the new unit.

[Froadin]

Update:
I found that there was some heavy aluminum tape over the hole where I could use my type of freeze sensor. So all is well on that front.

Finished sealing the unit up on the inside. And now it's time to test it.

Ok, it's only around 65 - 70 outside, so this isn't a great test so far, but....

Inside temp at 72 degrees. Turn the stat down to 60 and let it rip.

Within maybe 5 to 7 minutes, the temp at the first vent back is at 36 degrees and falling. Inside temp already dropped to 69 degrees.

After a few more minutes, the temp is at 34 degrees. And inside temp is down to 68 degrees.
I can't see any frost on the evap coil, but it does look a little 'shiny'.

After a few more minutes, I pulled the filter to get a better look at the evap coil. The temp at the vent was near 33 degrees before I did this, and went up to 34 after I did this.
Trailer temp almost down to 67.

It's still cooling the trailer down fast. But that isn't a surprise with the outside temps. But the lack of frost on the evap coil is a surprise when it's blowing air SO cold!

I put the filter back in place, the vent temp dropped back to 33 degrees within 2 minutes.

I will have to wait for a HOT day to truly test the unit out.
But I can say that this was a VERY EASY swap/upgrade to my AC unit. It now blows a LOT of air, which is a great thing with a ducted system.