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Old 06-06-2016, 10:57 AM   #1
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Installing a New Roof Top AC Unit (with pics)

Last year our roof top AC unit died in the late heat of summer. The compressor/gas system had issues. The hot side of the compressor system was hot and the cold side was also hot. I really do not know if the compressor itself went out internally or there was a gas leak in the system. These RV units are not really setup well for recharging and then the gas in the older units is outlawed now.

In this case I chose to replace the roof unit. After living through high heat in a camper, one get's spoiled real quick, you need an AC unit to have a good sleep at night. After some research, Dometic discontinued the original Brisk Air unit like ours and enough time had passed I could not get a new older style one.

So now to get a new design unit. After researching, the gas systems are different and the entire unit is redesigned on the Brisk Air II. The new gas system requires a higher pressure and the noise on some of the Penguin units is close to obnoxious. I have heard them in one of my buddies 5'er. The higher pressure means the compressor has to work harder to get it that high and noise comes from this. OK not going the thin profile route but even the normal unit still uses the higher pressure gas due to regulations. And the unit does not appear as rugged as the older Brisk Air.

The next item is the control system. To be more efficient, I think this is why they are doing it, the new control units have the fan run non stop and only cycle the compressor. Well on a camper, for folks who like the great outdoors, hearing a AC unit run non stop is not something we like.

So the hunt was on. The new units just did not appeal to me even though the reports are they cool well and the control feature of not shutting off was a real turn off.

I found the Dometic Commercial Grade unit. H'mm OK this is different. Yes it still uses the newer gas system, but it is built significantly different. These are used more on commercial applications, concession stand trailers etc. I called Dometic customer service and asked about this unit and if it was OK to use on a RV camper and will it fit in the standard 14 x 14 opening? They said by all means, yes. Then I went to, does it use the standard 6 prong plug of my older unit and can I use my original analog control unit? She looked it up and yes, it will plug right in and your original ducted air box will work just fine.

Great! These means I only need the roof unit and I get a much better built AC unit, better warranty and the system will shut down the fan when the T stat is satisfied. I asked, why are these not offered on RV's? Then the rest of the story comes out... She said, the RV industry is so price competitive, they do not offer the commercial unit. The RV manufactures only request the standard unit. Granted the cost is much more for the commercial unit but it is built better and the cost reflects what you are getting. Since we plan on keeping the T310SR for a good long time, we made the choice to get the better unit. This cost choice is about double, but I was doing the install so no cost from the install labor, only the roof unit.

We ordered one from American RV in CA. I have bought from them before and they handled this transaction very good. Due to the weight, it had to be a truck shipment which was not a problem. I had it shipped to the local freight terminal and I went to pick it up. You could have it shipped to your house, but that would cost more for a drop gate truck.

Here is the removal. I'll do this in pics.

You start on the inside. Take down the control unit and the air box.




Unscrew the control unit from the large air box plate, then take down the air box. There are 4 long screws/bolts in the corners that hold the roof unit in place. Take them out and the air box will come out. The foam insulation is glued to the wood opening. I used a sharp putty knife to carefully take this off to reuse it. Here is the air box on the camper floor

Take the 2 sheet metal screws off the lower air box plate for the control unit




You need to unhook the control unit. It is all plug in


And take the frost control off the evaporator coil


Here is what the ceiling ducts look like. There are 2 of these. They are a foam core duct with foil on the outside.


Next is up on the roof. Tarp and plywood down as this is not a walk on roof..


The roof unit off, yuk.. a bit dirty under there since Nov 2003 when the camper was built


Also notice there was bolts on the bottom that about cut through the roof


The old unit down on the ladder/scaffold


And the bolts that were resting on the rubber. I do not know if the original gasket was over compressed or not. The bolts inside holding the AC unit down were not loose but it was for sure too low.


I'll do the install on the next reply
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Old 06-06-2016, 11:21 AM   #2
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Now to the install. First here is how the new AC unit comes to you. All in a big box. Really need 2 people to get it out of the box and or manage the lifting. Son Ben helped.



We took the shroud off to check for internal shipping damage. There was some fin squeezing issues on the coils that we dressed up. During assembly they must of brushed up against them as they are all enclosed inside the shroud and was not shipping damage.

This unit is for sure built better then the older Brisk Air. Heaver duty unit.








I did see the screws on the top of the unit was rubbing the inside of the shroud. I gorilla taped over them to help the abrasion before it ground a hole in the shroud.

Now the install. Cleaned up the roof and Eternabonded over the bolts impressions


New AC unit up on the roof. We left the shroud off to not flex it or worse, lean on it by accident.


Lift, must lift and not slide or you will damage the gasket on the bottom, the new unit over the hole


Here it is 2 people again. One inside and one on the roof to line up the inside hole with the AC unit in the correct place.

We had to make 2 new foam board blocks as Sunline only has rigid boards around the opening. Made up 2 blocks and double sided taped them in place.

You can see the new pink block here. The black ones at the back end do not touch they are too far out and the roof pitches away


You compress the gasket about 50%. The roof is not 100% dead flat so there may be some areas ~ 45-ish % and some 55%. This aligns with just touching down on the foam blocks and applies even pressure on them.

And here we are all done up top. I upgraded the screws to stainless and added the larger fender washers as this is a place of cracking over time and rusting.


Inside you just reverse the unhook. We taped and stapled the air box foam back in place and plugged in the control box and frost sensor.

All works great now. I really do not notice a lot more noise with this unit even with the higher pressure gas system.

We are now happy and cool campers

Thanks for looking

John
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Old 06-06-2016, 01:58 PM   #3
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Poor Ben, after helping lift that thing up there, he probably regretted that "I owe you one" offer after the winter reconstruction!

Interesting on the commercial offering, I hadn't heard that before. I wonder if it'll be any more efficient over the old one? I would hope so, in 13 years time.
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Old 06-06-2016, 06:46 PM   #4
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One day the US manufactures will catch on the Europeans and the Asians are using mini splits heat and cooling in their MH's and campers.
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Old 06-06-2016, 10:25 PM   #5
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John B, you continue to amaze. What a magnificent install. And, it's good to know that Dometic has its Commercial Grade series, should any of us need to replace the A/C in future.

Sunline Fan: No (when it comes to efficiency, that is). Assuming that the new units run R-401a, they cannot be as efficient as the older units which used R-134 (much less the old, old units which still used R-12), even taking into account compressor and coil design, as well as improved digital controls. The overall difference in efficiency is not something any end-user would notice, but it is there.

Mainah: What are these 'mini-splits' to which you refer? Obviously you're talking small split systems, I presume like those which Mitsubishi and Sanyo have made for years for residential and light commercial use; but I can't feature that kind of setup in an RV.
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Old 06-07-2016, 06:22 AM   #6
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I think you'll find up to somewhere around 2010 the AC units had R22 after that they switched to R410-A. The newer refrigerant requires a much higher compressor head pressure it’s been in use in Europe for quite some time now in automotive applications. Yes the mini splits just like a house hold unit with a small evaporator inside the camper and the condenser unit in a side compartment. They have become extremely efficient even heating down to 17* and are using inverter technology in the compressor and fan assemblies. I have heard of people running a unit with a small Honda generator because of the soft start inverter compressor drawing far less current than a normal compressor.
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Old 06-07-2016, 10:05 PM   #7
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Quote:
Originally Posted by Sunline Fan View Post
Poor Ben, after helping lift that thing up there, he probably regretted that "I owe you one" offer after the winter reconstruction!

Interesting on the commercial offering, I hadn't heard that before. I wonder if it'll be any more efficient over the old one? I would hope so, in 13 years time.
Hi Jon,

Trust me, Ben has bailed me out 10X over the last year and a half. We exchange projects of "stuff to do" often. No need to keep track even...

The commercial grade AC unit, yes I too did not know about them either. But they are out there now. Need to be careful when searching for one. The commercial grade is the 479 series numbers

The standard Brisk Air II is the 459 series numbers. The rest of the part numbers are the same between the 2 series.

This is the one I got. A 15,000 BTU. unit, Dometic number 479516
Dometic 479516 15,000 BTU Commercial Grade Air Conditioner Upper Unit Trailer Camper RV

The T310SR had a 13,500 BTU in it before, yet the 2004 brochure called for the 15,000. There are so many windows in this floor plan, the 13,500 would barely cut it on a real hot day. I can tell the difference real quick with this 15,000 unit.

Camping World sells them too. Pricing is all over the place. They offered them for less a few months ago when I was looking
Dometic Commercial-Grade Air Conditioner, White - 15,000 BTU - Dometic 479516.XX1C0 - Air Conditioners - Camping World

The odd thing on the pricing, it is really all over. Some sites offer the standard Brisk Air II for the same cost as the Commercial grade. Other places, the commercial grade can be a lot more. And there is a price difference between the 13,500 and the 15,000.

Shop around to reputable dealers.

John
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Old 06-07-2016, 10:09 PM   #8
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Quote:
Originally Posted by Wannabes View Post
John B, you continue to amaze. What a magnificent install. And, it's good to know that Dometic has its Commercial Grade series, should any of us need to replace the A/C in future.
Hi Matthew,

Thanks for the good words. Much appreciated.

I see your industrial back ground still shines through. Kind of like riding a bike ah?

The one I bought has R-401A gas in it.

Thanks

John
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Old 06-10-2016, 09:24 AM   #9
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Thats looks awesome! Great job!
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