13.5k vs 15K AC---Worth the $200 price difference?

[khantroll]

Hi all! I've got to purchase a new AC this weekend. It looks like my options are 13.5k unit for about $580, or a 15k unit for $700. Is it worth the price difference? The old unit was a 13.5k, and my recent roof replacement added a lot of insulation (foil backed foam and polyurethane).


What's the group consensus?


Thanks!

[M & J]

Unless weight  or power consumption is a concern,  go with the biggest unit you can afford.

[khantroll]

She's currently got the stock 30 amp service, but a 50 amp upgrade with loadshed are in the future (though it may be some time). The ACs are supposedly rated at 11 amps for 13.5 and 15 amps for the 15 unit.


My other loads on the AC system aren't that high. I have a microwave, but it gets used infrequently. I have several notebook computers and a small LCD tv.


It'll be tight. Will the 15 amp draw (+ surge) be okay on the 30 amp setup?

[HamRad Mobile]

Good morning, Khantroll, 

     An interesting question. 

     The 13.5 K BTU unit is about $43.00 per K BTU, and the 15 K BTU unit is about $46.50 per K BTU, or the bigger one is also about $3.50 more expensive per K BTU.  A curious anomaly.   

     And, as you are already aware, there is also the question of the starting surge or the starting current load.  We know that the 30 Ampere RV electrical service is already at just about its capacity when starting the second air conditioner while the first one is running.  You can try it.  You might get away with it.  If you notice that you need to go outside to the electrical power pedestal to reset the circuit breaker there, or to reset the circuit breaker in the panel inside your motor home, then you will know that you did hit the limit with the 30 Ampere electrical service. 

     It might be interesting to use an "Amprobe" with a "clamp-around-the-wire" AC current measuring capability (or other similar current measuring device) and see just what the starting current draw looks like on one of the wires carrying the 120 VAC shore power to the motor home 120 VAC breaker panel.  No, it is not truly 100% accurate with the time constants involved (that requires some pretty involved measuring technique), but it will give you a pretty good idea of what is happening.  If you have thermal circuit breakers, and not magnetic circuit breakers, a short term current overload might not be a problem.  With the magnetic circuit breakers, it is highly probable that they will trip with a short duration current overload.  I have seen a magnetic circuit breaker trip in time to save the fuse on the primary side of the power supply of a piece of equipment that developed a serious problem.   

     Anyway, with the clocks, small radios, computer and other similar power supplies plugged in all the time, the load for the 12 VDC electrical system and the charger for the coach batteries, there can be a surprising amount of "phantom load" current on the 120 VAC circuit in a motor home now.  If you can measure what you have, and what the running and the starting current draw for the air conditioner compressor motors are, and then make your decision based on those numbers, you will be better off. 

     It is a little like trying to decide what air pressures to run in your tires.  The only good way is to measure the weight on each of the wheel assemblies on your motor home, so that you have real numbers to work with when looking at the tire manufacturer's load weight and tire pressure chart.  Good luck with it. 

          Enjoy; 

          Ralph 
          Latté Land, Washington 

     

[khantroll]

Ralph,


You've summed it up much better then I did. The short answer is that I don't know. I've tried not to tax the electric system in the RV because I know how old it is.


Does anyone know what type of breakers are used on Eyebrow Winnies?


I guess the answer is to re-arrange my upgrade time table and move the electrical upgrade to the forefront (and only use the AC or the other items in the meantime and not both). 


P.S. I too was surprised by the pricing. I thought they'd be the same per BTU, or similarly price in general.

[ClydesdaleKevin]

Not sure where you are shopping, but when we bought a new AC for our Holiday Rambler last year, we went with a Dometic Duotherm 15K...and the price difference between it and the 13K was marginal.  As I recall, it was about 12.00 more.

Kev

[khantroll]

I tried Camperland of Tulsa, CampingWorld, and JJ's RV. I also tried eBay and Amazon. The prices were slightly different, but they pretty much came out (once figuring in taxes for buying local, and shipping for online purchases) to 550 to 600 for the 13.5, and about 700 or so for the 15k.


Where did you purchase yours Kevin?

[ClydesdaleKevin]

Camper's Paradise, in Charlotte, NC.  They are mostly online, but also have a storefront.  We ended up going to pick it up to save on the shipping costs.  To be honest, I can't remember if it was on sale at the time or not.  They have the Dometic Duo Therm Brisk 2 Air units right now for 480.00 for the 13K unit, and 525.00 for the 15k unit.  So the difference in price is marginal with them.  I highly recommend the Duo Therm units over the Coleman or Advents.  This price includes the inside ceiling unit.  http://www.campersparadise.com/store/index.php?main_page=product_info&cPath=9&products_id=15783

Kev

[khantroll]

I'm totally going with them. They are currently offering free shipping on the unit, so it's a great deal for the Duo Therm units. Thanks Kevin!

[Oz]

13.5 or 15?  I found the 13.5 to be very adequate for my 24' Winnies.  Perhaps a 15 would have been even better, but I was personally happy with the 13.5, with the cab curtain and window shades closed, and I even had one AC outlet routed to cool the bathroom.

[khantroll]

That was where I was coming from. The 13.5 (even being 40 years old), seemed to keep the unit cool enough, so I wasn't sure if it was worth the price difference and possible strain on the electrical system. Of course, I also never used it in the middle of Arkansas Summer (think Louisiana humidity meets Nevada temperatures).


It's outside the scope of this post, but how did you duct it to the bathroom?

[ClydesdaleKevin]

You're welcome!  Mark's bathroom routeing was nothing short of genius! You really couldn't implement it that way with a Duo Therm the way the vents are, but you still might be able to adapt the idea depending on where your bathroom is located in relation to the AC unit.

And I would still strongly suggest getting the 15K unit...just in case you need it in the summer.

Kev

[ClydesdaleKevin]

And a little about the Duo Therm unit:  The air filter is the best I've seen, super easy to remove and replace, and isn't that cheap foam like Coleman uses...its a plastic mesh similar to the no longer available Carrier units.  They are also extremely light in weight and easy to install.  There are 4 vents, front, back and sides.  They are all adjustable for angle, and you can close them off as well...we keep the side vents closed.  It also has an "air shower" feature...you can stand under it and open a vent in the middle, and cold air pours down on your head.  We love ours!

Kev