Running 2 AC units on 30 amp
Hello We are picking up our new 2018 Miramar 35.3 tomorrow! We are very excited as we have been waiting since mid February when we ordered it. We are coming from a 29' travel trailer so this will ...
Forum Discussion
Might be okay, might not... Some good advice above.
If trying to run 2 ACs on 30 amps, you better know how the voltage is doing. Actually, even with just one is important. Low voltage causes an AC unit to draw more current and can cause even greater voltage drop and possibly prevent one or both AC from starting. Most importantly, if you use an AC unit(s) often enough under low voltage conditions (105V and below), you can cause cumulative irreversible damage to the AC resulting in premature failure. You *might* get one or both AC units to run and all seems okay, but you won't know how much damage has occurred and how much sooner it will fail.
An AC unit draws about 13-15 running amps and the momentary inrush current at startup will be about 50-60 amps (per manufacturer's specs) at 120 volts which is the industry/code nominal system and equipment/appliance voltage. It's important to know that these figures will increase as voltage goes down. *IF* you got the 1st AC to start and voltage was 120, the total current at startup of the 2nd AC will be 15+60 = 75 amps, plus any other loads that are running when trying to start the 2nd AC. That's a lot, even at full nominal voltage. As mentioned above, depending on a number of various factors, the 2nd unit might not start. If the voltage is already low after the 1st unit is running, it's very likely the 2nd unit will not start. Installing a "hard start" capacitor can help in some cases.
At a min. I'd use either a plug-in LED voltmeter or permanently mounted one on a wall to monitor voltage. The best thing of all is to use a Progressive Industries EMS unit that will shut power off at 104 volts. The "other" brand shuts down at 102V which is too low IMO. Note that voltage may look okay before you turn high load items on but can drop quite a bit with more loads running.
Older RV parks have pedestals wired in a star arrangement to a remote panel. Newer parks have pedestals wired in a loop-fed arrangement from one to the next. The newer parks are less likely on avg. to have voltage drop issues because of the heavy wire to the pedestals (typically around 200 amps). Older pedestals usually have 30 amp wire to them and can be a long run. As well, the older editions of the NEC required demand allowances were much smaller. I can almost guarantee that you won't be able to start a 2nd AC on 30 amps in an older RV park, esp. with high occupancy.
Running a 2nd AC off the 20 amp recept. in a pedestal may or may not work because the NEC does not require wire size to pedestals to be based on 20 amp + 30 amps running together and this could cause the voltage drop to be too high. A newer CG would have more of a chance of this working.
If trying to run 2 ACs on 30 amps, you better know how the voltage is doing. Actually, even with just one is important. Low voltage causes an AC unit to draw more current and can cause even greater voltage drop and possibly prevent one or both AC from starting. Most importantly, if you use an AC unit(s) often enough under low voltage conditions (105V and below), you can cause cumulative irreversible damage to the AC resulting in premature failure. You *might* get one or both AC units to run and all seems okay, but you won't know how much damage has occurred and how much sooner it will fail.
An AC unit draws about 13-15 running amps and the momentary inrush current at startup will be about 50-60 amps (per manufacturer's specs) at 120 volts which is the industry/code nominal system and equipment/appliance voltage. It's important to know that these figures will increase as voltage goes down. *IF* you got the 1st AC to start and voltage was 120, the total current at startup of the 2nd AC will be 15+60 = 75 amps, plus any other loads that are running when trying to start the 2nd AC. That's a lot, even at full nominal voltage. As mentioned above, depending on a number of various factors, the 2nd unit might not start. If the voltage is already low after the 1st unit is running, it's very likely the 2nd unit will not start. Installing a "hard start" capacitor can help in some cases.
At a min. I'd use either a plug-in LED voltmeter or permanently mounted one on a wall to monitor voltage. The best thing of all is to use a Progressive Industries EMS unit that will shut power off at 104 volts. The "other" brand shuts down at 102V which is too low IMO. Note that voltage may look okay before you turn high load items on but can drop quite a bit with more loads running.
Older RV parks have pedestals wired in a star arrangement to a remote panel. Newer parks have pedestals wired in a loop-fed arrangement from one to the next. The newer parks are less likely on avg. to have voltage drop issues because of the heavy wire to the pedestals (typically around 200 amps). Older pedestals usually have 30 amp wire to them and can be a long run. As well, the older editions of the NEC required demand allowances were much smaller. I can almost guarantee that you won't be able to start a 2nd AC on 30 amps in an older RV park, esp. with high occupancy.
Running a 2nd AC off the 20 amp recept. in a pedestal may or may not work because the NEC does not require wire size to pedestals to be based on 20 amp + 30 amps running together and this could cause the voltage drop to be too high. A newer CG would have more of a chance of this working.
We Cant Wait wrote:A receptacle and a circuit breaker are designed to operate at their rating indefinitely. If a pedestal recept. or shore power cord plug gets warm/hot, the cause will be dirty contacts inside the receptacle, a dirty plug and/or weak contact pressure inside the recept. Always make sure your plug blades are kept clean (use emery cloth or sandpaper). As noted above, if a pedestal recept. looks in rough shape, try and find another site or run on minimal loads. Avoid plugging into a pedestal with the power on as this causes pitting and dirt buildup on plug blades.
Also pulling a full 30 AMPS for an extended period of time could in all likely hood over hear and melt the pedestal plug or your cord plug as shown above.
