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08-15-2022, 06:04 PM
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#1
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Junior Member
Join Date: Aug 2016
Posts: 9
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Soft start for AC?
I just bought a Generac 3300 Inverter Generator to run my 13500 BTU AC. Unfortunately, it cannot keep up and fails after only a few minutes. Since I cannot return the Generac, I am considering installing a Soft Start or something similar. I am a bit reluctant though as I feel like I just wasted $800 on a useless generator and don’t want to feel the same about the Soft Start which is $300. Any experience with one of these? Do they actually work as advertised? Is there any potential long term damage to the AC by using one?
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08-15-2022, 06:06 PM
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#2
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Senior Member
Fleetwood Owners Club
Join Date: Feb 2017
Location: Texas
Posts: 836
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watching
__________________
2000 Southwind 32v and a 03 Tracker 5 speed 2WD toad, Roadmaster off road tow bar & 2" drop hitch
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08-15-2022, 06:15 PM
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#3
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Senior Member
Join Date: Sep 2017
Location: SE Minnesota
Posts: 153
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Buy a SoftstartRV. I have them on both my AC units now. I can easily run both on 30A now. My startup current spike is basically gone.
__________________
2017 Winnebago Vista 29ve (Special Edition) Many Mods: Trimark Keyless Entry, Ride Rite Air bags, Roadmaster anti-sway bars, CrossFire dual tire system, TST TPMS, Roadmaster Sterling tow bar. Many little mods.
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08-15-2022, 06:24 PM
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#4
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Senior Member
Winnebago Owners Club
Join Date: Sep 2015
Posts: 1,810
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Quote:
Originally Posted by emmmin
I just bought a Generac 3300 Inverter Generator to run my 13500 BTU AC. Unfortunately, it cannot keep up and fails after only a few minutes. Since I cannot return the Generac, I am considering installing a Soft Start or something similar. I am a bit reluctant though as I feel like I just wasted $800 on a useless generator and don’t want to feel the same about the Soft Start which is $300. Any experience with one of these? Do they actually work as advertised? Is there any potential long term damage to the AC by using one?
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A soft start only reduces the start-up current draw. If your AC is starting and runs for a few minutes it would not do you any good.
The prime reason for a soft start is to lower the startup amperage starting the AC. Most use it to be able to run a second AC on 30 amp. The draw from a 13500 startup can reach 19 to 24 amps. Then drops to about 12 or 13. So if you're drawing 13 amps, and try to pull another 19 to start the second AC you're over 30 amps and the main breaker will trip. If you can get the second one started, 13 + 13 is 26 and you are under the limit.
3300 watts is 27.5 amps. You need to put a clamp-on load meter on it and see what it is doing. Either you are drawing a lot of amps before the AC starts. How much is your power converter drawing? If your batteries are not 100% charged a charger/convertor can draw 15 to 20 amps. Or the Generac is not putting out enough power to get your AC all the way up and therefore the startup load never drops.
$800 is not much to spend on a generator. To reasonably run an AC you should have one in the 4500 - 5000 range, considering other things that might be running.
__________________
2006 Winnebago Journey
39K
Cat C7
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08-15-2022, 07:14 PM
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#5
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Senior Member
Join Date: Jul 2014
Posts: 35,317
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30 amp RV service is 3600 watts. That runs 1 air conditioner, 1 microwave, 1 fridge and 1 converter/charger all at the same time.
You have a 3300 watt generator or is it ?
That may only be the surge rating. The specs will show running watts, that's your concern.
Before spending money, get up on the roof and clean the condenser coils under the AC cover. Flush them out with a garden hose.
I did that on my old class C and the amp draw dropped from 19 amps to 16 amps and I was no longer tripping my brothers 20 amp house breaker .
PS: Just looked up the specs, it's a 2500 watt rated running generator, 3300 watt startup.
Still should run the AC but make sure it's clean and things like the water heater is off.
RV type fridge is about 5 amps, so switching to gas will help alot.
Converter/chargers onlt draw a few amps if the batteries are charged and my old 55 amp converter/charger drew 8 amps at max output.
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08-15-2022, 08:41 PM
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#6
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Member
Join Date: Mar 2022
Posts: 56
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The soft start makes a night and day difference--BUT ONLY in the moment when the A/C's compressor is kicking on. If your A/C is able to turn on then it dies minutes later, that's a bit unusual and probably not something the soft start will solve.
A/C's will be generally harder to power as they warm up or it gets hotter outside so it could be that you're just over the wattage limit. My A/C would fire up in the morning with my 3200 watt gen but on a super hot day, I'd hear it die when the compressor cycled off-to-on later in the day. The soft start completely resolved that issue.
For your situation, I'd make sure other things aren't taking power (flip your fridge and water heater to gas!).
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08-15-2022, 11:29 PM
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#7
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Senior Member
Join Date: Dec 2019
Location: Bend,or
Posts: 464
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I have the smaller Generac 2500 (2200 running).
It runs a Dometic 15000BTU with Micro Air easy start.
You should have no problem...
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08-16-2022, 03:32 AM
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#8
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Junior Member
Join Date: Aug 2016
Posts: 9
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Thanks for all the responses. Some further details… my AC is brand new so I don’t think it is an issue of it being dirty. I only have one AC unit, not two. Everything else is turned off except for the battery charger as there is no switch for that on the control panel. I will look for a breaker for that but don’t know of any other way to turn that off. I have a 2020 Gulf Stream Vista Cruiser 23RSS.
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08-16-2022, 03:53 AM
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#9
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Junior Member
Join Date: Aug 2016
Posts: 9
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The generator claims a starting wattage of 3300 and running wattage of 2500 which according to what I have read should power the 13500 BTU AC.
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08-16-2022, 04:57 AM
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#10
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Senior Member
Join Date: Jul 2014
Posts: 35,317
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Best advice is to pickup a Kill A Watt meter and see if it's a generator issue or a AC unit issue.
The Kill A Watt measures amps, volts, and HZs. It's $25 and plugs In between the generator and RV.
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08-16-2022, 08:27 AM
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#11
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Senior Member
Join Date: Mar 2019
Posts: 465
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What exactly happens when it “fails after a few minutes” ? Does the motor keep running with no output? Breaker trip? Air conditioner shuts down? EMS indicates low voltage and shuts off?
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08-16-2022, 08:32 AM
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#12
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Moderator Emeritus
Ford Super Duty Owner
Join Date: Aug 2000
Location: Bryan, TX when not traveling.
Posts: 22,942
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Your Gererac should easily operate a 13,500 BTUH A/C unit. What else are you trying to operate at the same time? You will have to put the fridge on propane as well as the water heater. It cannot operate with both of those and the A.C unit. If you want to run the microwave, shut off the A/C unit.
It will help the A/C operation, to put the fan motor on continuous and not auto.
Ken
__________________
Amateur Radio Operator (KE5DFR)|No Longer Full-Time! - 2023 Cougar 22MLS toted by 2022 F150, 3.5L EcoBoost Tow Max FX4 Lariat Travel with one Standard Schnauzer and one small Timneh African Gray Parrot, retired mechanical engineer
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08-16-2022, 11:38 AM
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#13
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Junior Member
Join Date: Aug 2016
Posts: 9
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Quote:
Originally Posted by Jkwilson1989
What exactly happens when it “fails after a few minutes” ? Does the motor keep running with no output? Breaker trip? Air conditioner shuts down? EMS indicates low voltage and shuts off?
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The generator struggles for a for a few minutes (red engine warning light comes on) and then eventually shuts off completely. The breaker never trips on the RV. As noted, nothing else is on, nor is anything even plugged into the outlets. I am going to look tonight to see if there is a breaker for the battery charger in case that is the culprit. There is no on/off switch for that on the control panel.
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08-16-2022, 12:19 PM
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#14
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Senior Member
Country Coach Owners Club
Join Date: Feb 2019
Location: Tucson AZ
Posts: 456
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Quote:
Originally Posted by emmmin
The generator struggles for a for a few minutes (red engine warning light comes on) and then eventually shuts off completely. The breaker never trips on the RV. As noted, nothing else is on, nor is anything even plugged into the outlets. I am going to look tonight to see if there is a breaker for the battery charger in case that is the culprit. There is no on/off switch for that on the control panel.
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That's fine, but you are basically engaged on a fishing expedition at this point, as in, "Try this and see if it works."
As stated already, the first step in the real solution is to find out how much load you are putting on that generator, using the Kill-o-watt or similar current measuring device. Then you know the answer. Either the generator is not performing as rated, or the A/C is not performing as rated, or you have another load that you have not accounted for.
__________________
John
2007 Country Coach Tribute; Cat C9 400; 2012 Ford Edge toad; Roadmaster Blackhawk 2 10,000 lb tow bar; Demco AF1 Braking System; 2007 BMW K1200LT Hannigan Trike Conversion; Member, IEEE, NFPA, PMI, NRC SRO (Ret).
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