Replacing rear 13,500btu with 15,000btu A/C?

I am NOT suggesting anything. I never stated anything about the wire gauge of the 30 amp shore cord. What I am stating is simple. I have worked on RV's for 38 years and NEVER has a lower amp draw been suggested for a 30 amp rated system in an RV. Remember, I am old enough to have worked on RV's for almost 20 years BEFORE 50 amp was even an option or available. I have seen numerous 30 amp ends pitted and melted and that was caused by using a 30 to 15 amp adapter. NOT really low voltage, but when you adapt down and most RV'ers are pretty ignorant about adapting down and the problems that causes, the voltage does drop and the AMP draw goes up and that generates HEAT. That causes the pitting and melting of the adapter and if on a regular 30 amp shore CG plug and you do indeed draw MORE than 30 amps, which a LOT of RV'ers do, will cause the melting and pitting on the 30 amp shore cord ends. I have customers(probably thousands over the years), come into my service center and the 50 to 30 adapter is pitted and melted on the 30 amp end and rarely will I find one not damaged from running MORE amps than 30 thru that adapter. A LOT of RV'ers think that if they overload the system the breakers will protect the system. THEY DO NOT. You must have knowledge and manage your amp draw when connected to 30 amp service or when connected with a 50 to 30 dogbone if you do NOT have a onboard EMS system. Doug

Are you suggesting that there is something "special" about the #10 wire used in the shore power cord of an RV. That it is somehow "exempt" from a continuous rating of 80% (3 hours). BTW that is 24 amps, not 25.

I've had 30 amp cord ends melt with a 15 amp shore power supply. The culprit appears to be low voltage. The "ends" that failed were 30 amp female Cameco. The male Cameco seem to be ok but the females burn up easily.

dougrainer wrote:
Please reference any codes or NEC your statement that an RV 30 amp PLUG and 30 POWER CORD is only rated at 25 amp continuous. We are talking RV wiring, not regular home circuits. They have designed 30 amp RV's for over 45 years and in 38 years as a tech, I have NEVER heard the 25 continuous running as it applies to RV's. I have seen and heard it on various forums, but NEVER from an expert, just posters that heard of this from other sources. Doug

dougrainer wrote:

valhalla360 wrote:
I wouldn't bother to swap them out if it's just to upgrade but if you are replacing anyway the cost difference should be small, so sure.

As mentioned, two on 30amp is questionable regardless of BTU rating.

The 30amp outlet is actually only rated at 25amp continuous, so while it may or may work, there is a good chance of overheating wires and connections. In a worst case scenario, it could lead to a fire if the breaker doesn't trip.

Please reference any codes or NEC your statement that an RV 30 amp PLUG and 30 POWER CORD is only rated at 25 amp continuous. We are talking RV wiring, not regular home circuits. They have designed 30 amp RV's for over 45 years and in 38 years as a tech, I have NEVER heard the 25 continuous running as it applies to RV's. I have seen and heard it on various forums, but NEVER from an expert, just posters that heard of this from other sources. Doug

I work with a group of master electricians who set policy for a major state agency and this subject came up and they argue over just about anything electrical. To a man they all said the continuous rating is lower.

I don't have the specific rules. No one's going to stop you if you want to overload your system. You pay for your ticket, you take your chances. I've seen people do a lot of stupid things and get away with it.

dougrainer wrote:

valhalla360 wrote:
I wouldn't bother to swap them out if it's just to upgrade but if you are replacing anyway the cost difference should be small, so sure.

As mentioned, two on 30amp is questionable regardless of BTU rating.

The 30amp outlet is actually only rated at 25amp continuous, so while it may or may work, there is a good chance of overheating wires and connections. In a worst case scenario, it could lead to a fire if the breaker doesn't trip.

Please reference any codes or NEC your statement that an RV 30 amp PLUG and 30 POWER CORD is only rated at 25 amp continuous. We are talking RV wiring, not regular home circuits. They have designed 30 amp RV's for over 45 years and in 38 years as a tech, I have NEVER heard the 25 continuous running as it applies to RV's. I have seen and heard it on various forums, but NEVER from an expert, just posters that heard of this from other sources. Doug

It is not directly in the code per say. However there is a section that describes dedicated loads of continuous nature need a supply rated 125% of the load. Or interpreted as continuous load should be not exceed 80% of supply. Continuous load described as 3+ hours.

Granted this does not apply to thermostatic controlled loads such as a water heater or air conditioner at home or in an RV. Still we well know an RV air conditioner can run 12+ hours continuous. Walks like a duck, quacks like a duck..... So it is what it is.

Ever wonder why so many 30 amp plugs get over heated? It is not just worn out connectors.

IMO best to stick with 24 amps max if running continuous.

For the OP... unless you are having cooling issues Iwill suggest staying same or even going to 2x 13.5 units. When shopping do compare amp draw specifications. Look for high efficiency units.

Cocky_Camper wrote:
Currently, not cool enough to our liking. The front was struggling last year. Both units are 14 years old.

Has the condensers ever been cleaned? You might be spending money replacing perfectly good units that just need cleaning. ACs don't work well if they can't dissipate the heat.
My 23 years old OEM ACs are still performing like new.

Richard

I would go to 15,000 and I would also go to heat pumps (which would require replacing the thermostats). They aren't that much more and it would be a nicer upgrade than just increasing the Btuh a little. The heat pumps are nice to take a chill off and save on other fuels.

I've got by running two ACs on 30A before, and it's definitely pushing it on overload. Much of the heat gets lost in the cord so the breakers on the pedestal may not even see the overload condition until things start to melt. I've grabbed my 30A cord a few times and knew it was time to start shedding loads.

Here is something more important than the above arguing over a couple of amps! Make sure that your new A/C's will talk to your thermostat and each other. Many older models used an older style thermostat that will not work with the newer A/C units.

PPL Motors has pretty good prices on A/C units and they're also good at making sure the replacement units will work with your thermostats.

theoldwizard1 wrote:

dougrainer wrote:
Regardless of what you have done in the past, running a 15k and a 13.5k is NOT advisable on 30 amp service.

That is a VERY BROAD BRUSH statement ! I certainly would NOT condemn running 2 A/C units on 30A, assuming ALL of the wire is in tip top shape. Check the specs. Newer A/C ARE more efficient (draw less current).

You might need to install Micro Air Easy Start units on both to reduce the start surge.

Here we go. I base MY comments on 38 years and still working as an RV tech. Newer Units draw less amps. NOT so. BROAD STATEMENT. It depends on the unit and its parameters. But, MOST RV AC units draw the same amperage as units 35 years ago. The reason is simple. While they have improved the compressors, the law stated they had to go to 410 for coolant and that causes the compressors to run at higher PSI. Which requires more work and higher amps. I stated the CORRECT amp draw would be for 2 AC units. That adds up to a marginal few amps for the rest of the RV. What is YOUR expertise to claim my statements are NOT factual? Doug

dougrainer wrote:
Regardless of what you have done in the past, running a 15k and a 13.5k is NOT advisable on 30 amp service.

That is a VERY BROAD BRUSH statement ! I certainly would NOT condemn running 2 A/C units on 30A, assuming ALL of the wire is in tip top shape. Check the specs. Newer A/C ARE more efficient (draw less current).

You might need to install Micro Air Easy Start units on both to reduce the start surge.

If I had to replace a non working 13,ooo unit I would upgrade to a 15,000 only in the front of the coach. I just did this. My13,000 unit in the bedroom will make it cold enough to store hanging meat. It makes it cold so I would not change it to larger. The front is usually considerably more area, more windows etc so that’s where I put the larger unit. I also run it at night in an effort to keep it cool enough in the bedroom so that the back unit does not run. Usually works.