Add second air conditioner to 30 amp RV
I'm looking for advice from either a Master Electrician or Electrical Engineer on this question. I've seen a video showing how to add a second air conditioner to a 30 amp RV. The video shows wiring ...
Forum Discussion
Some comments:
- Running two AC units on 30 amps is a bad idea. You're looking at 2 units at 13 amps, plus at least a few amps for the converter, plus whatever else might be running on 120 volts. While a 30 amp breaker (in your RV or pedestal) technically speaking can run indefinitely at 30 amps, it will get very hot due to the thermal elements in breakers. To make it worse, RV panels have the 20 amp AC breaker right below the 30 amp main breaker. Besides the heat, the breakers can eventually trip.
- AC units have a 20 amp breaker which is sized to ensure it won't trip on the momentary startup inrush current, it's not based on the full load running current.
- Momentary startup inrush current is in the 50-60 amp range.
- Voltage is extremely important when running AC units. If the voltage gets down to 105 volts or less, that will cause damage to the motor windings. AC units will draw more current as the voltage goes down which will exacerbate voltage drop.
- Voltage may *look* okay when running, but can drop very low during startup and lead to AC damage.
- AC unit damage is cumulative over time and it can fail prematurely one day for no apparent reason. AC units are expensive to replace.
- Running a 2nd AC unit off the 20 amp breaker in pedestal may or may not work. "Modern" CGs have loop-fed pedestals on large amperage wire (like say 200 amps) and the possibility of excessive voltage drop is significantly reduced. Older CGs have distribution panels spread around the property with small gauge wire to pedestals, which can be as small as #10 wire and thus voltage drop can be high plus wiring runs to the pedestals can be long, further increasing voltage drop.
- If you plan to travel around a lot and not stay exclusively at newer CGs/RV parks with loop-fed pedestals, do not expect running a 2nd AC unit off the pedestal 20 amp breaker to work.
- Installing a permanently mounted voltmeter inside an RV is highly recommended. An EMS unit is also recommended.
- Choosing a site close to a pad-mounted transformer in a CG can help in some cases.
- Running two AC units on 30 amps is a bad idea. You're looking at 2 units at 13 amps, plus at least a few amps for the converter, plus whatever else might be running on 120 volts. While a 30 amp breaker (in your RV or pedestal) technically speaking can run indefinitely at 30 amps, it will get very hot due to the thermal elements in breakers. To make it worse, RV panels have the 20 amp AC breaker right below the 30 amp main breaker. Besides the heat, the breakers can eventually trip.
- AC units have a 20 amp breaker which is sized to ensure it won't trip on the momentary startup inrush current, it's not based on the full load running current.
- Momentary startup inrush current is in the 50-60 amp range.
- Voltage is extremely important when running AC units. If the voltage gets down to 105 volts or less, that will cause damage to the motor windings. AC units will draw more current as the voltage goes down which will exacerbate voltage drop.
- Voltage may *look* okay when running, but can drop very low during startup and lead to AC damage.
- AC unit damage is cumulative over time and it can fail prematurely one day for no apparent reason. AC units are expensive to replace.
- Running a 2nd AC unit off the 20 amp breaker in pedestal may or may not work. "Modern" CGs have loop-fed pedestals on large amperage wire (like say 200 amps) and the possibility of excessive voltage drop is significantly reduced. Older CGs have distribution panels spread around the property with small gauge wire to pedestals, which can be as small as #10 wire and thus voltage drop can be high plus wiring runs to the pedestals can be long, further increasing voltage drop.
- If you plan to travel around a lot and not stay exclusively at newer CGs/RV parks with loop-fed pedestals, do not expect running a 2nd AC unit off the pedestal 20 amp breaker to work.
- Installing a permanently mounted voltmeter inside an RV is highly recommended. An EMS unit is also recommended.
- Choosing a site close to a pad-mounted transformer in a CG can help in some cases.
