13,500 BTU vs 15,000 BTU second AC

One thing to remember is don't get too large where it cycles. A compressor off does not cool . I would rather have it run than not. While running it dehumidifies.Years ago my father gave me a 3 ton unit for my house.It should have been a 2 ton. The 3 ton was off more than it was on because it cooled so quickly. We have better thermostats now so the differental could be less. I'd at least try what you have before changing it. The dealer is now aware of your concern and should be willing to fix it if needed but try it first.

Hey, Beltone!

As I was reading the thread and where the OP's from, TX, I thought of humidity and the location I thought of was Texas! I laid over in that airport. There was an outside deck so I walked out and it was a sauna. Humidity bad or worse than FL.

And Aruba, thanks for endorsing my "cycling" concern. A/C is Conditioning, not just Cooling and we don't feel as well in Cold/Humid as we do in Cool/Dry.

aruba5er wrote:
One thing to remember is don't get too large where it cycles. A compressor off does not cool . I would rather have it run than not. While running it dehumidifies.Years ago my father gave me a 3 ton unit for my house.It should have been a 2 ton. The 3 ton was off more than it was on because it cooled so quickly. We have better thermostats now so the differental could be less. I'd at least try what you have before changing it. The dealer is now aware of your concern and should be willing to fix it if needed but try it first.

This type response has been on these forums before. You CANNOT compare sizing a residential (oversizing) to a RV. Totally different operations. As too the argument about not running long enough because it is a 15k or such---NONSENSE. Just set the larger unit tstat to a different temp to prevent that. I have lived in North Texas for 35 years and we have regular 95 to 105 temps for 2 to 4 months and ANY RV needs to utilize the largest (15k) units that it can. Doug

Beltone Magoo wrote:
Don't think those Dometic reps have been to the Houston area. I have a 41ft MH and the 2 13,500 btu units were not getting the job done. I replaced the front unit with a 15,000 as that is where all the heat was coming from thru the windshield etc. Now works good at keeping a decent temp in the MH. One concession I made was to set the thermostat to always run only on high fan speed. Hasn't frozen up yet. That was something I learned when I had a TT that would freeze up if the fan speed was lowered. FWIW I am just north of Houston off I45. Good luck and safe travels!

I do NOT believe that the Dealer has even talked to the Dometic reps. I deal with Dometic weekly and I can guarantee that Dometic would never state such nonsense. Your TT did not have a wall tstat and did not have a freeze control. ALL RV roof top units with wall tstats have a freeze control that regardless of the conditions will NOT allow a AC to freeze. Your current motorhome IF you have wall tstats will not freeze no matter what fan speed or temp you set. Doug

I forgot to mention, IF the add on AC is a low profile Penguin Dometic, they do NOT have a 15k anymore and have not for over 2 years. They have the 13.5 and in place of the OLDER 15k, they have a HC model. The new designed Penguins with 410, they could not get them rated at 15k. So, they call them HC models. Larger than a 13.5 but not up to 15k, slightly lower than a 15k. Doug

Wow. Thanks fellas. I think the original sales guy was trying to get out of having to admit his mistake. The owner took over and has called me personally several times and has stated that he will take care of it and is still giving me the option on how to handle. I just want to make sure that I understand what I am asking for, whether it will make a difference, and be as thoughtful and reasonable before making a decision.

Here is what intrigues me. The second AC is a dometic low profile 13,500, ducted with the rest of the unit AND has a wall t-stat. During our first trip it was 96 and both units ran pretty much constantly. When we started to break down the unit to go home there was water dripping from the front unit (the 13.5 the dealer added) Looking in I discovered a thin sheet of ice that had formed on the evaporator and then slid off.

I really believe that I can use more cooling capacity if it can work effectively in the ducted system.

Regarding the 30 vs 50 amp, I will use 50 amp sites until the fall and hope that 30 amp will run the 15K unit in the main living area and be enough without cranking up the second AC. I think the 15k AC pulls about 17A at start up if I recall correctly.

So why am I getting ice with a wall t-stat on the add on unit?

Is the freeze sensor not wired correctly?

TexasRedNeck wrote:
Wow. Thanks fellas. I think the original sales guy was trying to get out of having to admit his mistake. The owner took over and has called me personally several times and has stated that he will take care of it and is still giving me the option on how to handle. I just want to make sure that I understand what I am asking for, whether it will make a difference, and be as thoughtful and reasonable before making a decision.

Here is what intrigues me. The second AC is a dometic low profile 13,500, ducted with the rest of the unit AND has a wall t-stat. During our first trip it was 96 and both units ran pretty much constantly. When we started to break down the unit to go home there was water dripping from the front unit (the 13.5 the dealer added) Looking in I discovered a thin sheet of ice that had formed on the evaporator and then slid off.

I really believe that I can use more cooling capacity if it can work effectively in the ducted system.

Regarding the 30 vs 50 amp, I will use 50 amp sites until the fall and hope that 30 amp will run the 15K unit in the main living area and be enough without cranking up the second AC. I think the 15k AC pulls about 17A at start up if I recall correctly.

So why am I getting ice with a wall t-stat on the add on unit?

Is the freeze sensor not wired correctly?

They either did NOT install the freeze sensor or they installed it wrong. Doug

We are running BOTH 13.5 units on 30A with NO problems, so you will have no problem with a 15 unit. Try running your fan on "high" instead of auto, when in high humidity and that should stop the icing.

I can't even figure out exactly which unit I have. I've googled every number on the label

You have a 13.5k Penguin model. Doug