Roof AC Needs Replacing Dometic DuoTherm > Brisk Air II - Questions

HammerToe · 06-11-2021, 02:31 AM

I own a 2008 Keystone Cougar Model 291 RLS fifth wheel trailer. It looks like the OEM roof air conditioner - a Domestic Dometic Duo-Therm Model 57915.541 - which came with the trailer has finally ‘packed it in’ and will need to be replaced.

Based on my research to date, it looks like the (probably most compatible) replacement unit would be a Dometic B57915.XX1C0 Brisk II Polar White Air Conditioner (13,500 BTU 410A).

In terms of installation, I’m trying to decide whether or not to undertake it myself OR go through a dealer to have it all done for me. I emailed a local dealer to ask for a quote.

In response, I was quoted:

• “You are probably looking around $1100 plus $300 for labor IF ‘NON-DUCTED’. There is a good possibility if your unit is a DUCTED unit, then you will have to change the ‘control box’ and the wall thermostat, which could cost you another $300 parts plus $150 labor”.

The latter possibility/expense I did not anticipate (even as a possibility).

I kind of figured that given and assuming that the Brisk II unit from Dometic was (as far as I know) the recommended replacement unit, that it would essentially be ‘more or less’ a relatively simple ‘Drop In Replacement’.

So anyway, I figured I would try to find out what would be involved in replacing my air conditioner, IDEALLY FROM SOMEONE WHO MAY HAVE EITHER PERSONALLY DONE IT OR HAD IT DONE, ASSUMING THE SAME STARTING POINT/UNIT BEING REPLACED WITH A BRISK II unit.

As far as I know - assuming we - the dealer and I are on the same wavelength insofar as the term – ‘ducted’ is concerned: well, the way the current unit works in my trailer is that, in addition to intaking and subsequently expelling cold air directly from the unit itself, it does ‘duct’ cold air through (as far as I can recall without checking) three additional ‘swivel outlets’ ‘forward’ in the interior roof of the trailer - two of them further forward in the trailers ‘living room’ and one more in the trailers bedroom.

This might seem like a stupid question but IS THAT what is Universally Understood the term ‘Ducting’ is supposed to mean? Is there some other ‘form’ or ‘type’ of ‘Ducting’ that I am not aware of?
And assuming that – correctly – that my current unit is ‘Ducted’ – I kind of wonder how that might complicate and thus increase the cost of a replacement being installed due to that fact alone ‘that much’.
Or perhaps it doesn’t… Perhaps it might be the other part of the response that makes me wonder…
“There’s a good possibility if your unit is a ducted unit, that you will have to change the control box in the wall thermostat?”.

I suppose (who am I to say?) that that might be true but I was kind of assuming and HOPING that the new unit would simply pretty much ‘drop in and plug-and-play’, that probably all it would be necessary to get it working would be to connected up to AC (the very final thing, perhaps) and, insofar as other low-voltage connections/communications with the thermostat and whatever else there might be involved, that ideally all you might have to do is plug together a couple of connectors.

So anyway, can anybody help clarify this for me? Would be appreciated.

Has anybody out there actually either ‘gol darn gone and dun it’ themselves and so have hands-on experience or, failing that, had a dealer do it who could help clarify things for me?

Thanks.

wiredgeorge · 06-11-2021, 02:56 AM

I replaced my 2002 Dometic A/C a few years ago. I have a Duotherm thermostat on the wall. I replaced my 13.5K btu unit with a 15K btu as they have the same footprint. My A/C system IS ducted and the process involved dragging the new A/C box up to the roof via a ladder. First take the bottom unit cover off and unplug the bottom unit. Unscrew the four long bolts that retain the top unit; these bolts are about a foot long as I recall. Get up on roof and lift off old A/C. My new A/C had a smaller overall footprint but fit in the same 14x14" hole. Put the supplied gasket in place and unbox new Brisk II and set it over the gasket centering the A/C on the hole. Go downstairs, and run the four bolts up through into the new A/C and snug. Plug in lower unit. I can't remember if the 120V AC needed to be connected but if so that needs done with the existing wires and the new A/C talked to my old Duotherm wall mounted thermostat just fine. Put the cover on the lower unit and you are done. This all took perhaps 1-2 hours. Wasn't hard and again, no new control box was needed. My thermostat is simple; Cold, Off, Heat and Fan Auto or High or Low.

This is my thermostat:
https://www.amazon.com/Dometic-31069...X9B4QB3ARW3418

**chuckster57** · 06-11-2021, 03:29 AM

We have changed numerous A/C units. As far as I know, as long as you use the same brand, it’s just a simple swap. I would upgrade to a 15K unit, as stated it’s the same size opening. 110 wiring will go to the control box and roof unit will plug into that.

You will have a freeze sensor that’s between the fins, just note it’s location and swap it over. When you mount the ring, go around the 4 long bolts in steps and compress the foam gasket to about 1/2 of its original thickness. Hardest part is getting the old unit off the roof and the new one on.

wiredgeorge · 06-11-2021, 07:09 AM

Quote:

Originally Posted by chuckster57

We have changed numerous A/C units. As far as I know, as long as you use the same brand, it’s just a simple swap. I would upgrade to a 15K unit, as stated it’s the same size opening. 110 wiring will go to the control box and roof unit will plug into that.

You will have a freeze sensor that’s between the fins, just note it’s location and swap it over. When you mount the ring, go around the 4 long bolts in steps and compress the foam gasket to about 1/2 of its original thickness. Hardest part is getting the old unit off the roof and the new one on.

Since our original 13.5K btu Dometic was original, I believe the new 15K btu Brisk II actually uses less electricity while running if I remember the specs. A bit more efficient I guess.

HammerToe · 06-11-2021, 09:53 AM

Hi, and thanks to BOTH of you for your DETAILED responses, and ‘Fast’, too. The information you provided me kind of ‘confirmed my suspicions’… To wit: ‘It t can’t be that hard!’

‘For the life of me’, I was having a problem trying to UNDERSTAND WHY whether the unit was ‘ducted’ or ‘un-ducted’, which in turn made me wonder if we (the dealer and I) were ‘talking about the same thing’. As I mentioned – to me ‘ducted’ simply meant that in addition to cold air being blown out directly into the interior from the unit itself, it was also ‘ducted’ to additional outlets - in my case, three of them – in the ‘forward interior’ roof of the trailer. HOW COULD THAT POSSIBLY MAKE THINGS MORE COMPLICATED? (At least – much ‘more expensively’ complicated?).

WiredGeorge: ‘THAT’ is EXACTLY the thermostat I have in my 2008 fifth wheel. EXACTLY.

And thanks for the detailed instructions as well – you pretty much confirmed what I saw and deduced from an EXCELLENT VIDEO on YouTube : https://youtu.be/UKajweIFh4M (‘RV Air Conditioner Maintenance - New Gasket Seal + Clean & Lube’).

Assuming I wanted to attempt to install a replacement myself, it appears that I can ‘pick up’ a 13,500 BTU unit on Amazon.CA (I live in Canada) for $1105.49 with ‘Free Shipping’ +5% sales tax which would bring the total to $1160.76.

The 15,000 BTU unit goes for $1293.06 - also with free shipping - which would come out to $1357.71 – $196.95 more…

I think I will probably though just go with the 13,500 BTU unit. The price difference doesn’t ‘bother me that much’ but I’m 75 years old and ‘starting to feel my age’ and I’m not sure how much longer I will be keeping the trailer before I decide to sell it. ALSO – I think the 13,500 BTU unit should be ‘plenty’ if it is anything like the current unit that I have in the trailer when it was new. Back then, ‘you could freeze your eyeballs out’. It was better, far better than the central air system in my house!

Here is a link to the unit on the Amazon.ca website. https://www.amazon.ca/Dometic-Black-...89&sr=8-3&th=1

The Product Description from that page:

Size :13,500 BTU | Color Name:Polar White

The Dometic Brisk II - the stronger, lighter, smaller and more RV air conditioner. The Brisk II uses its smart design, tighter specification allowances and improved materials to maximize air flow and performance. THIS RV A/C UNIT OFFERS A 15% AIR FLOW INCREASE AND IS 19% LIGHTER THAN PREVIOUS MODELS, MAKING IT THE SMALLEST ROOFTOP AIR CONDITIONING UNIT AVAILABLE. This unit fits standard 14 x 14 Air Vents. Center discharge air delivery for increased airflow and improved cooling capacity. Offers a stronger, more stable base pan and a more rigid shroud for improved durability. This unit is compatible with a Dometic Universal Air distribution box (ADB), Dometic Return Air Grill, and Dometic Single Zone LCD thermostat or Dometic Comfort Control Center II thermostat-all sold separately. (Not included with this unit). (ADB or Thermostat is required) Please note if replacing an AC on a Newmar please call Dometic (800-544-4881) before purchasing for further information. Brisk II is available with white or black shroud. The unit is Polar White.

The local dealer I emailed quoted me:

“You’re probably looking around $1100 parts + $300 labour if non-ducted” or $1400 in total. (“IF NON-DUCTED?” That part confused me a bit. That it might cost me MORE just because it was ‘ducted’?

In any event, by the time you’ve added 5% sales tax in +7% provincial sales tax (which I wouldn’t have to pay if I ordered from Amazon) the total comes out to $1568, compared to $1161 or $407 more.

IF it was only a couple hundred bucks or so, I think I would just pay somebody to do it but “$407 is $407”.

WiredGeorge: do you by any chance remember if - given that both the OEM version and the Brisk Air II were Domestic units, if all that was involved in wiring it up to the thermostat and everything involved ‘connectors’ and perhaps you could just unplug the old one and plug the new one in? (I suspect you actually have to do a little bit of manual connecting up here of these wires. No big deal I suppose; I’m sure I can figure it out but it would be nice if there were connectors involved.

I think before I make up my mind I’m going to pull the interior ceiling AC cover down and check things out and see what I can figure out about the wiring from inside, and then I’m going to take another look at that ‘Love Your RV’ video again - for the third time - and study it more carefully.

I’m currently leaning towards to trying to do the job myself. I’m sure I could get one of my next-door neighbors to help me get the unit up on my roof and get it into position. Just need to check out the wiring a bit more and get my comfort level up.

ONE FINAL QUESTION THAT JUST OCCURRED TO ME HAVING DONE A BIT MORE READING AND THINKING:

What did you wind up ‘doing’ insofar as the INTERIOR ceiling (what to call it) cover/grill/whatever is concerned?

Did you wind up simply reusing the one from your old OEM unit? Or did/does the new unit come with one, or do you have to buy one separately?

(I think the Correct Name for this thing is and ‘Air Distribution Box’).

I THINK/am Pretty Darn Sure that THIS is the one that is currently installed in the ceiling of my trailer: https://www.amazon.ca/Dometic-310593...s%2C205&sr=8-7

I guess, bottom line, I’m wondering if I would need to purchase a ‘compatible return air shell’ for the Brisk II or if I could just reuse my current one?

Thanks again for your help; much appreciated.

wiredgeorge · 06-11-2021, 12:35 PM

You don't touch the thermostat which connects to the A/C by the little box with a connector inside the bottom of the lower unit. A non-ducted A/C will have a couple knobs on it and NO thermostat. You turn on the A/C cooling via one knob and fan stuff with the other. I have had a couple non-ducted in the past but can't remember exactly how the controls work. I changed my A/C because here in Texas, the 13.5K BTU unit which was working fine just didn't cut it and I was looking for a bit more cooling on triple digit days in direct sunlight. When you take off the bottom cover and then if you take off the plenum frame you will see ducts exiting on the sides. I just added one of these last month:
https://rvairflow.com/

It did increase the airflow out my A/C vents (those are where the ducts run to). Since it was in the low 90s tops all weekend as it rained quite a bit, didn't get to see if it made the camper feel cooler but it did allow for more air to be pushed. Guess being in Canada you have a different perspective on cooling as you likely don't see a lot of days north of 110F.

The new A/C will not come with a new inside cover. Old one will be reused. To remove the cover, there are six sheet metal screws (memory not great) and two towards the rear are under round disks to hide them. The others (I think 4) are accessible when you remove the filter cover. When you pry out the disks over the two rear screws take care not to break the fingers which hold them in the holes. There is a thermostat that clips up inside the unit on top and connects to the lower unit by a wire; just watch where it clips on and remove it. Undo the plug this connects to thermostat and powers the upper A/C assembly.

Here is a good video. Take the time and use some foil tape like in this video to seal things and pop you vents off and do the same. The factory job was very likely miserable.

https://www.youtube.com/watch?v=jW-hrR-d80Y

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