Yet another AC question

[Edingale]

I am replacing both roof ACs on my Navigator. Originally they were both 13.5K units. My question is: With the new normal of high temps expected over the next decade, I am considering replacing the front unit with a 15K and the rear with a 13.5K. What should I consider before doing this?
The rear unit cools sufficiently for the bedroom, but I need more cooling up front. Any thoughts?

[450Donn]

Nothing. But the difference in cooling power is not enough to notice most of the time. The key to cooling an RV is park in shade, start the AC early and cover windows

[docj]

We're considering doing the same thing when our 18-year old units fail, but the difference between 13,500 and 15,000 is just ~11%. So the actual improvement in cooling won't be all that much. No doubt they will be more energy efficient and the cooling fins will be clean so they will perform better but don't let you expectations get too high.

[lrsses]

I purchased a new to us 2004 Sea Breeze LX8321 two a/c original equipment they didn’t cool well at so I cleaned the condenser with CR something from a auto part store. Found the units cooled a lot better also find the leak I had and replaced both gaskets no more leaks and lots more cold air!

[vito.a]

We replaced the front AC in our 97 Windsor with a 15,000 BTU Duo Therm. It out performed the older 13,500 BTU by quite a bit (mainly because it was newer).

Some of the things you need to consider are your 98 will have the old 4 button thermostat and all the new units come set up for the new 3rd gen digital Comfort Control Center.
First you need to understand: Dometic made the 4 button thermostat which came in your coach, then sometime around 2002 the 5 button, and now the newest digital Comfort Control Center.
You have a choice of updating the control board in your rear AC and furnace to the new style, or purchase a conversion control board for your new AC.
The issue is I do not think they offer a conversion board for the older 4 button thermostat, only the slightly newer 5 button. Please confirm this with Dometic customer service.
So you will have to convert everything to either the 5 button style, or the new digital CCC.
Changing out the AC is pretty straight forward once you get it on the roof. Just 4 bolts holding it down, the 120v wiring, and the RJ11 (phone cord) that are accessed from inside.
Hope this helps.

[docj]

Originally Posted by vito.a

Some of the things you need to consider are your 98 will have the old 4 button thermostat and all the new units come set up for the new 3rd gen digital Comfort Control Center.

With all due respect I'm not sure this is correct. I've been looking to replace my Penguin A/C with a new Penguin (either A/C or heat pump) and it appears that both come in two versions. One uses the basic single zone CT thermostat and the other uses the CCC. It would seem as if those of us with older coaches would be better served with the simple version.

Here's a link to the CT model: https://www.dometic.com/en-us/us/pro...uin-ii-_-20780

[Quincy]

We have a 25 and 13.5 AC also and the front unit will need a little help from the rear unit on hot Summer days.

Sounds as if you are going to replace the units while they are still functioning, which is fine if money is no problem. I just don't see throwing working units away.

I do respectively question the thought that new units will be more energy efficient. Unless they are designed differently or a new part or refrigerant is used.

All the changes over the years from the 70's on that improved efficiency of house AC's were design changes. The parts stay roughly the same.

Not until some engineer figured out that putting the compressor inside a wrap around coil with a top discharge was more efficient than multiple fan speeds and all the other things they tried did the efficiency increase.

JMHO

[docj]

Originally Posted by Quincy

I do respectively question the thought that new units will be more energy efficient. Unless they are designed differently or a new part or refrigerant is used.

From the Dometic Penguin website:

"...its R410A refrigerant is more eco-friendly and releases heat efficiently. Its high-performance motor and fan deliver a first-class cooling performance."

According to the website this unit produces 15,000 BTU's and uses only ~14.5A when running. I'm pretty sure that's significantly less current than my present 13,500 BTU Penguins use.

BTU's per watt used is the definition of energy efficiency.

[Edingale]

Originally Posted by docj

We're considering doing the same thing when our 18-year old units fail, but the difference between 13,500 and 15,000 is just ~11%. So the actual improvement in cooling won't be all that much. No doubt they will be more energy efficient and the cooling fins will be clean so they will perform better but don't let you expectations get too high.

I called Dometic and was told they don't sell a 15K Btu AC, but they have a "High Capacity" model which uses the 13.5K compressor and then upgrades the coil pack, etc. Because no manufacturer makes a 15K compressor, they emulate 15K with the mods but are not allowed to market it as a 15K unit.

I might as well stick with the 13.5K model.

[Edingale]

Originally Posted by docj

With all due respect I'm not sure this is correct. I've been looking to replace my Penguin A/C with a new Penguin (either A/C or heat pump) and it appears that both come in two versions. One uses the basic single zone CT thermostat and the other uses the CCC. It would seem as if those of us with older coaches would be better served with the simple version.

The single zone CT system is really for one AC installation. Dometic told me that by using the CCC system model, it will have an electronic board pre-installed in each unit (I have 2 zones obviously) and is compatible with the old wiring. To use the CT system requires running new wires... $$$$. I definitely will stick to ordering a CCC system model.

[Ivylog]

The Tstat issue is only if you have a heat pump or want to replace with one.

[docj]

Originally Posted by Edingale

The single zone CT system is really for one AC installation. Dometic told me that by using the CCC system model, it will have an electronic board pre-installed in each unit (I have 2 zones obviously) and is compatible with the old wiring. To use the CT system requires running new wires... $$$$. I definitely will stick to ordering a CCC system model.

"Compatible with the old wiring" may be true if your old wiring was a standard 4-wire phone line. Furthermore, the installation instructions state that the furnace control wiring must somehow be brought up to the A/C box area. My vintage coach uses standard thermostat wiring, not 4-wire phone wiring. And my furnace wiring comes up to the thermostat and not to the AC box.

By comparison, the wiring for the CT thermostat looks just like any other thermostat. I see no reason why my existing wiring can't be used for the CT. The color coding won't be correct, but as long as I keep track of the wires I don't see why this won't work.

My two A/C's are independently controlled now and I see no reason to combine them to create "zones". I don't have a problem walking down the hall to the other thermostat if I need to adjust it.

[Edingale]

Originally Posted by docj

"Compatible with the old wiring" may be true if your old wiring was a standard 4-wire phone line. Furthermore, the installation instructions state that the furnace control wiring must somehow be brought up to the A/C box area. My vintage coach uses standard thermostat wiring, not 4-wire phone wiring. And my furnace wiring comes up to the thermostat and not to the AC box.

By comparison, the wiring for the CT thermostat looks just like any other thermostat. I see no reason why my existing wiring can't be used for the CT. The color coding won't be correct, but as long as I keep track of the wires I don't see why this won't work.

My two A/C's are independently controlled now and I see no reason to combine them to create "zones". I don't have a problem walking down the hall to the other thermostat if I need to adjust it.

Thank you for this input. I know better than to trust the words of representatives of models that are out of production, so I will have a look-see of my own. Your comments will be invaluable to inform my inspection.
Right now my MH is 1500 miles away, so my arms and eyesight are somewhat restrictive. I will be on site by next week and I will let you know what I find. Since my coach is from 1998, I think I will find thermostat wiring and not telephone cable connected to my T-stat, so the advice that the CCC 2 box is compatible may not be true. We shall see.
In the meantime, thanks again. I appreciate your input.

[docj]

Originally Posted by Edingale

Right now my MH is 1500 miles away, so my arms and eyesight are somewhat restrictive. I will be on site by next week and I will let you know what I find. Since my coach is from 1998, I think I will find thermostat wiring and not telephone cable connected to my T-stat, so the advice that the CCC 2 box is compatible may not be true. We shall see.
In the meantime, thanks again. I appreciate your input.

Let me know what you figure out. I haven't yet made the replacement. What I've told you has been based on lots of online research, but hearing from someone who has actually made the change would be great. Good luck.