seer factor on roof top units?

[robertglines1]

I have tried Dometic site and Carrier ;any suggestions to find seer rating on roof top units??

[Sean]

You won't find them.  Like automotive air conditioners, RV units are not covered by the DOE's minimum SEER requirements and so the required testing is not done and the numbers are not published.

In actuality, SEER as defined does not even apply to RV air conditioners, since there is no standard definition of a "season," given how the "typical" RV is used.  More appropriate standardized efficiency ratings for RV air conditioners would be the EER or COP.  Those can be derived, even if not published, and  can be used to compare between brands or between different styles of RV units.

Generally speaking, rooftop package units will have fairly low EERs compared to larger residential style units.  In fact, the DOE's standards require a much higher efficiency for residential central air conditioners than for smaller package type units such as window air conditioners, and even through-the-wall split systems.  It's just not possible to achieve the same efficiency on a little one-ton package unit that is achievable on a 3-10 ton residential system.  This is the reason that I wrote, in the other thread, that three-ton basement units, when operating at capacity, are generally going to be more efficient than one-ton roof units -- or one-ton basement units, for that matter.

FWIW, I calculate the EER of my Dometic Penguin roof units at around 9.

-Sean
http://OurOdyssey.BlogSpot.com

[JohnEd]

I read here that the method used t calculate the BTU capacity for a home unit is very different than that used for the RV units.  Point was made that "there is no standard for RV rating".  So comparing the "tonnage" is not entirely valid as the actual tonnage for two brands rated equally may not be the same and each may vary from the home rating.  It can't be as bad as all that or people like SEAN would be all weepy and they don't seem to be.

I think I am quoting Nick but it was long ago and I'm not certain.

HTH
John

[Ncbob]

This was not a good year for our 2 10+year old rooftops...they both had heart attacks before we left Central FL.
Taking a tip from Florida Cliff I contacted Family RV in New Port Ritchie and bought two 13.5 BTU straight cool units at slightly less that $500 for each.

Change out time was about 40 minutes per unit, at the hands of seasoned AC installer, Cliff, and we were back to normal. I find no fault with either unit to date and given the opportunity to retrace my steps I would do it exactly the same way.

NCbob

[robertglines1]

my purpose was not to attack roof tops but to understand them..there is no scientific common measurement to compare is what I have learned...I will always keep a open mind and yes it can be changed...

[Sean]

Just to be clear, SEER is not a "scientific" common measure, either.  OTOH, "EER" or COP is.  The EER is easily measured.  I recommend using the EER to compare air conditioners anyway, rather than SEER which is open to a great deal of fudging on the part of manufacturers.  Here is a good write-up on the issue:

http://www.dr-fix-it.com/arc_seer.html

For the more technically minded, here is how SEER is done:

http://ari.org/ARI/util/showdoc.aspx?doc=1028

FWIW, The RV appliance industry has had little incentive to improve efficiency, or even publish performance data for that matter.  The market is simply too small and fractured.  It's hard enough to compete in the space anyway; witness Carrier's exit from the business last year, leaving Dometic and Coleman-Mach as the lone competitors in the arena.

All of that said, performance of package air conditioners is easy to measure, and there are plenty of folks out there with opinions about the relative performance of various models.  However, there is a great deal of variability from unit to unit even in the same make and model, as the manufacturing tolerances for these are very, very sloppy.

None of this, BTW, is specific to roof units -- it applies equally to basement units.  RV and marine models are simply not subject to the same rules and oversight as residential units.

-Sean
http://OurOdyssey.BlogSpot.com

[JohnEd]

NCbob,

I have a roof unit that is 1976 vintage working on my S&S.  It has had little usage as one unit cools me dwn in 90 plus weather.  The second unit is 22 years old and doing equally well.  Both are Dometic.  Both are of the 13.5KBTU size.  Sean must be correct about the lack of QA.

John