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Thread: 2021 Ac has soft start
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07-29-2021, 06:54 PM #31
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Hey Jeff,
Also like the detailed answer. My question is with my 15k unit and 59 locked rotor amps puts me at over 7000w at start up. Is it true to say most all people running with generators out there, or inadequate shore power are slowing wearing down their AC compressors prematurely? Seems the only solution is a soft start. And if this is the norm out there with AC units why in the ^%@! wouldn't the manufacturer just put the dang soft starts in from the get go. Thanks again for you info.
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07-29-2021, 07:04 PM #32
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Hey Jeff,
Also like the detailed answer. My question is with my 15k unit and 59 locked rotor amps puts me at over 7000w at start up. Is it true to say most all people running with generators out there, or inadequate shore power are slowing wearing down their AC compressors prematurely? Seems the only solution is a soft start. And if this is the norm out there with AC units why in the ^%@! wouldn't the manufacturer just put the dang soft starts in from the get go. Thanks again for you info.
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07-30-2021, 06:03 PM #33
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Please note that the locked rotor starting amps is only needed for a few seconds and on most OEM units their is a "start capacitor" or "hard start capacitor" in the system that is used to provide SOME (not all) of the required amperage boost needed to jumpstart the compressor. The problem is the output of the start capacitor is very short (measured in milliseconds) and only "assists" in starting the compressor. To further complicate things, the power required to start the compressor changes as the environmental conditions change. For example: As I stated in my previous response, as the outside air temperature increases, the rated operating wattage goes up exponentially. The same hold true for the starting wattage. However, the output of the "start capacitor" or "hard start capacitor" is fixed so the more extreme the conditions get, the more power that is required to start the compressor. As you can see, this puts everything into that grey area since nobody truly knows how many amps you truly need to provide during compressor startup unless you have the right equipment (oscilloscope) that can measure this draw realtime and is fast enough to catch it and even then, the requirements are constantly changing baed on environmental conditions.
The only upgrade that I am aware of that is currently available that addresses this is the Micro-Air EasyStart as it measures the amp draw during start up and uses a proprietary algorythm to calculate how much amperage is needed and for how long at several points during the compressor startup cycle (a few seconds) and spreads out the amp draw across this period of time resulting in significantly less amps required at any given time.....the end result is a lower power requirement for compressor startup (i.e. locked rotor load rating)....this does nothing for the rated "running watts" needed to keep the compressor running once it is started though.
So it is difficult to answer you question, with either a yes/no answer given the variables I have touched on above. The safe answer is to ensure you are not operating at the very top end of your power supply source's rated capability and that you have some margin in your supplied capacities versus your loads. Meaning don't think because you have an A/C unit that is rated for 1400 running watts and you are using a 2200 watt rated generator (1800 watts continuous use rated) that you have plenty of margin. That margin get's quickly depleted when you take into account all of the "variables".
Example: Your 1400 running watts rated AC unit may require up to 1800 watts if the outside air temps are high. This alone puts you at or above the maximum rated continuous running wattage out put of your generator before you then add in all of the other power requirements you are putting on your generator at the same time such as your onboard power inverter supplying all of your DC powdered devices as well as the built-in DC charger that is trying to keep your battery(s) charged while on an AC power source.
The best advice I could give is if your RV is equipped to work off of a 30amp power source and you want to use a generator to augment the use of shore power that you simply purchase a generator or multiple generators and a parallel kit that will provide a rated 30 amps (3600 Watts) of continuous power as a minimum requirement. This will allow you run things in your RV just as if you are on shore power with all of the active load protections in place in the power control panel (i.e. circuit breakers and fuses). I have learned over the years that even though the smaller 2200 watt generators can/will run many AC units that it is putting a very heavy load on the generator making it run at a much higher duty cycle...this translates into more fuel consumption and higher decibel levels as the generator is under heavy loads. A 4200 watt generator (3600 running watts) will very likely be able to run anything in the trailer and remain in "ECO" mode which translates into fuel savings as well as lower decibels. The generator will also likely last longer as it is being run at a much lower duty cycle.
Again, I hope this helps put things into perspective for you.Jeff and Debbie
2021 Imagine 2250RK
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08-04-2021, 08:51 AM #34
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On our 310 GK-R, I was able to fire up each AC independently the other day, on a standard extension cord shore power plugin. I'm not sure if the outlet at our storage facility is 15 or 20amp, but it didn't blow.
I even switched on the fridge with the main AC to see what would happen (we need to run the fridge the night before heading out) and it didn't pop the breaker.
This is very helpful for us, especially in the NC summers! Our Purple gel mattress holds a lot of heat, so first night out last time was a warm evening, even with the AC cranked down. Now I can fire up the bedroom AC the night before and easier sleeping first night out!Colin & Tracy
'21 Chevy Silverado 3500HD LTZ/Z71/SRW, Long bed, Anderson UH
'21 Solitude 310 GK-R
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08-04-2021, 10:15 AM #35
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I want to add that to check FLA-full load amps at start up you could use an analog ammeter with a dial and pointer. Or I know Fluke makes a modern meter to capture and record start up current draw but then you are getting into something that is a tool of a professional and we will never use.. As mentioned a digital multi meter will average over time and give a median current reading. An Oscilloscope is not a good way to measure current as it cannot do it directly. It can be use used in conjunction with a your digital multi-meter a little understanding of Ohm's law and a few resistors.
https://www.homedepot.com/p/Gardner-...-500/202867879
Or you could look up the data sheet and it will tell all you need to know: https://www.airxcel.com/DesktopModul...sheet_1012.pdfLast edited by Wicked ace; 08-04-2021 at 10:21 AM.
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