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Soft starter for AC units


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Hi, my first post here and grateful for what I've already learned!  We live in FL and have warm weather all year, so when we camp locally the A/C is on frequently.   We are taking a long trip out west later this summer and camping at some places where will have only 30 amp available.  We have 3 15kw air conditioners and we have read a lot about adding a soft starter to each unit.   Have you added those to your units and were you pleased with the results?  They aren't an inexpensive add (especially with 3 a/c units) and want to make sure they are worth the investment.   My hubby is handy so he will likely do the installs himself.   Would appreciate any advice on whether they are worth it and what brand you selected and why.  Thanks so much!  

 

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Welcome Aboard!

 

What exactly are you trying to accomplish? On 30 amps, I don't think you'll ever run all 3 simultaneously.   A soft start will minimize the 'spike' the A/C unit has when it's starting up, but it won't reduce the amp draw when it's running.   

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18 years with three 15Ks and no soft starts, often on 30 amps, but you can only run 2 of them. It’s all about energy management on 30 amps with a big rig. 
Contrary to some, a residential refrigerator is not an issue as it only draws 1 amp…a AC is around 13 amps. There are 2 often overlooked items that use up the 3 extra amps you have… the battery charger and the ice maker. 

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18 hours ago, Sharon L. said:

Hi, my first post here and grateful for what I've already learned!  We live in FL and have warm weather all year, so when we camp locally the A/C is on frequently.   We are taking a long trip out west later this summer and camping at some places where will have only 30 amp available.  We have 3 15kw air conditioners and we have read a lot about adding a soft starter to each unit.   Have you added those to your units and were you pleased with the results?  They aren't an inexpensive add (especially with 3 a/c units) and want to make sure they are worth the investment.   My hubby is handy so he will likely do the installs himself.   Would appreciate any advice on whether they are worth it and what brand you selected and why.  Thanks so much!  

 

We just had our first experience with a 30 amp hookup and no soft starts. We were able to run two ACs and residential fridge but turned off one of the ACs if using the microwave. Hot water heater is another draw to be aware of. Overall it was not difficult to manage if you monitor the amps being used. Of course you could always start your generator if you really needed to power everything at once.

Welcome to the group and happy camping!

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I ran 2 ac's off a 30 amp breaker last weekend on my Montana. Not a Monaco but a lot newer heat pump and ac than the Monaco.

Our home compressor went out, took 5 days to get it fixed (ended up buying entire outside condenser unit), and it was 100 degrees. Moved into the Montana.

 

I had the Montana plugged into the 30 amp at my shop and both ac's worked fine for a few days. Had the fridge on propane and no water heater on. On the hottest day the electricity to the 5th wheel went out. I went and checked the shop panel, the 30 amp breaker was hot as a pistol. So hot I couldn't touch it. I think I fried it because even after cooling off it wouldn't reset. Went into my other shop where I also have a 30 amp rv panel and took the breaker out of it and changed them out. Worked ok until the home unit got fixed and I was able to turn one ac off and turn the other one up to 85 which is what I do in the summer.

Would have stayed in the Monaco since it's hooked up to 50 amps but it's inside so no tv reception (have winegard pathwayx2 and antenna on the Montana) and I love my tv.

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I've had many issues running on 30 amps, who know why for sure, but I installed the soft starts on my 2 A/Cs and have had no issues with installing and using them. Good instructions and good tech support (if you overlook something in the directions, as I did for 1 unit).  I've only been on 30 amps a few times, but all worked well.

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On 6/19/2021 at 1:37 PM, Corkman said:

I've had many issues running on 30 amps, who know why for sure, but I installed the soft starts on my 2 A/Cs and have had no issues with installing and using them. Good instructions and good tech support (if you overlook something in the directions, as I did for 1 unit).  I've only been on 30 amps a few times, but all worked well.

Thanks Corkman, I'm curious what brand you installed.  Was it Soft Start?  There are so many other ones out there, some considerably cheaper.  I'm curious why you installed them, did you have issues running your AC's on 30 amp?   Everyone seems to have such different experiences.  Thanks so much!  

 

On 6/19/2021 at 11:49 AM, Mocephus said:

We just had our first experience with a 30 amp hookup and no soft starts. We were able to run two ACs and residential fridge but turned off one of the ACs if using the microwave. Hot water heater is another draw to be aware of. Overall it was not difficult to manage if you monitor the amps being used. Of course you could always start your generator if you really needed to power everything at once.

Welcome to the group and happy camping!

Thanks so much for the welcome.  We can't wait to take our first long trip this August.   Monitoring the amps seems like the ticket.   Even though I live in FL doesn't mean I like the heat, and it's not fun camping if you are too hot!  Appreciate the feedback.  

On 6/19/2021 at 1:07 PM, FishAR said:

I ran 2 ac's off a 30 amp breaker last weekend on my Montana. Not a Monaco but a lot newer heat pump and ac than the Monaco.

Our home compressor went out, took 5 days to get it fixed (ended up buying entire outside condenser unit), and it was 100 degrees. Moved into the Montana.

 

I had the Montana plugged into the 30 amp at my shop and both ac's worked fine for a few days. Had the fridge on propane and no water heater on. On the hottest day the electricity to the 5th wheel went out. I went and checked the shop panel, the 30 amp breaker was hot as a pistol. So hot I couldn't touch it. I think I fried it because even after cooling off it wouldn't reset. Went into my other shop where I also have a 30 amp rv panel and took the breaker out of it and changed them out. Worked ok until the home unit got fixed and I was able to turn one ac off and turn the other one up to 85 which is what I do in the summer.

Would have stayed in the Monaco since it's hooked up to 50 amps but it's inside so no tv reception (have winegard pathwayx2 and antenna on the Montana) and I love my tv.

Hi FishAR,

So it appears they worked for a while before the breaker problem.  Interesting.  Thanks!   

 

On 6/19/2021 at 1:07 PM, FishAR said:

I ran 2 ac's off a 30 amp breaker last weekend on my Montana. Not a Monaco but a lot newer heat pump and ac than the Monaco.

Our home compressor went out, took 5 days to get it fixed (ended up buying entire outside condenser unit), and it was 100 degrees. Moved into the Montana.

 

I had the Montana plugged into the 30 amp at my shop and both ac's worked fine for a few days. Had the fridge on propane and no water heater on. On the hottest day the electricity to the 5th wheel went out. I went and checked the shop panel, the 30 amp breaker was hot as a pistol. So hot I couldn't touch it. I think I fried it because even after cooling off it wouldn't reset. Went into my other shop where I also have a 30 amp rv panel and took the breaker out of it and changed them out. Worked ok until the home unit got fixed and I was able to turn one ac off and turn the other one up to 85 which is what I do in the summer.

Would have stayed in the Monaco since it's hooked up to 50 amps but it's inside so no tv reception (have winegard pathwayx2 and antenna on the Montana) and I love my tv.

 

On 6/19/2021 at 10:42 AM, Ivylog said:

18 years with three 15Ks and no soft starts, often on 30 amps, but you can only run 2 of them. It’s all about energy management on 30 amps with a big rig. 
Contrary to some, a residential refrigerator is not an issue as it only draws 1 amp…a AC is around 13 amps. There are 2 often overlooked items that use up the 3 extra amps you have… the battery charger and the ice maker. 

Hi Ivylog, that is encouraging.  Since we can close the bedroom off nicely, maybe that is solution, just run the ones in the bedroom.  I never thought of the ice maker as a big draw, thanks for telling me that.  We have had a weird issue with the middle unit, it short cycles on occasion, but an "expert" told us to always use our fans on "high" not "auto" and that will solve that problem.  Do you keep your fans on high?  Thanks so much for the information, I really appreciate it.  

 

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On 6/18/2021 at 7:37 PM, windsorbill06 said:

Welcome Aboard!

 

What exactly are you trying to accomplish? On 30 amps, I don't think you'll ever run all 3 simultaneously.   A soft start will minimize the 'spike' the A/C unit has when it's starting up, but it won't reduce the amp draw when it's running.   

Hi windsorbill06, I was hoping to ease the load so we could run all three units when it's really hot.  I guess I was hoping that would be possible if the "spike" was reduced at start up.  The reviews on those are all over the board, and since we haven't taken any really long trips yet, I want to make sure we have as much done in advance so we don't have any surprises that we could have headed off in advance.  

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I never had any luck drawing more than 24 amps (80% of 30 amps) at a campground without burning up the cord plug and the socket in the power pedestal.  The contact points in the socket just aren't big enough to carry any heavier load and will heat up.  When they heat up, they'll turn black with oxidation.  The oxidation is a poor conductor and causes more and more heat to build up.  That's when the plug melts and socket looses its tension.  You can sometimes get by with scraping the oxidation off the plug and use it again but the next poor sap trying to use the power pedestal won't have much luck trying to get his plug to make good connection.  The only remedy is to replace the socket and I'm sure the campgrounds can't afford to do that for every stay. 

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On 30 Amps and it's hot, I'll throw the breakers between the main panel and the Magnum inverter (non hybrid kind) powered subpanel, and let the pedestal run 2 A/Cs on the main panel while the rest of the coach (including residential fridge, TV, etc) runs off batteries and solar from the subpanel. But that 30A pedestal is going to get very hot!  At night when it's cooler, I'll drop back to just one A/C and flip the breakers back on to top off the batteries.  Load sharing the Aqua Hot and one A/C unit also helps as most of the time the AH draws nothing when the water is hot (Just like the rear A/C load shares with the washer...) or just flip it to diesel.  Three A/Cs on 30amp is way to much run current.  I guess a large hybrid inverter might be able to supplement if the 3rd unit had a very low duty cycle and big battery bank, and the wiring was done appropriately such a that one A/C could be optionally powered from the inverter subpanel.  Too complex for my thinking.  If it's hot enough for 3 A/Cs, it's hot enough to find a 50A site.

FWIW

 

 

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13 hours ago, Sharon L. said:

Hi windsorbill06, I was hoping to ease the load so we could run all three units when it's really hot.  I guess I was hoping that would be possible if the "spike" was reduced at start up.  The reviews on those are all over the board, and since we haven't taken any really long trips yet, I want to make sure we have as much done in advance so we don't have any surprises that we could have headed off in advance.  

Sharon,

You will not be able to run 3 air conditioners on a 30 amp shore power connection even with the Soft-Start gizmo. All the Sort-Start does is reduce the start up current on the compressor. It does this by supplementing power from a stored capacitor. That capacitor will be discharged in a very short period of time and charged again at a slow rate before the compressor needs to start again. I have never seen inside one of these Soft-Starts but imagine there is a steering mechanism that blocks current from the main AC input during compressor startup forcing all the startup current to be supplied by a large capacitor. After the compressor starts and the capacitor is discharged the current flow reverts back to the main AC input and a resistor limits the charge current to the capacitor thus keeping the overall current drain from the main AC line on a average of what the air conditioner would draw with both the fan and the compressor running after the startup up surge. A 13K or 15K BTU RV air conditioner is going to average between 12 to 14 amps with both the fan on high and the compressor running. Multiply 12 x 3 and you get 36 amps which is 6 amps over the maximum of 30 amps. In most campgrounds you will not even be able to draw 30 amps from the pedestal because of weak circuit breakers and bad sockets. With two units running with the compressors on you will have very little power left for the rest of the RV. Don't even try to run the microwave or a hair dryer.

The unit that is short cycling is most likely because one of the registers is blowing cold air on the thermostat.

If you know it is going to be a hot day then by all means put the fans on high a the beginning of the day and leave them there. Remember the largest source of heat in a Class A motorhome is the windshield so consider using outside screens to reduce the heat that enters the coach.

I would not waste money putting a Soft-Start on the middle unit and just know you must leave it turned off when on 30 amp shore power.

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16 hours ago, Sharon L. said:

Thanks Corkman, I'm curious what brand you installed.  Was it Soft Start?  There are so many other ones out there, some considerably cheaper.  I'm curious why you installed them, did you have issues running your AC's on 30 amp?   Everyone seems to have such different experiences.  Thanks so much!  

 

Thanks so much for the welcome.  We can't wait to take our first long trip this August.   Monitoring the amps seems like the ticket.   Even though I live in FL doesn't mean I like the heat, and it's not fun camping if you are too hot!  Appreciate the feedback.  

Hi FishAR,

So it appears they worked for a while before the breaker problem.  Interesting.  Thanks!   

 

 

Hi Ivylog, that is encouraging.  Since we can close the bedroom off nicely, maybe that is solution, just run the ones in the bedroom.  I never thought of the ice maker as a big draw, thanks for telling me that.  We have had a weird issue with the middle unit, it short cycles on occasion, but an "expert" told us to always use our fans on "high" not "auto" and that will solve that problem.  Do you keep your fans on high?  Thanks so much for the information, I really appreciate it.  

 

I do not run the fans on high but I do close the ceiling vents in the area I do not want to AC. I actually run the front AC at night to cool the BR…much quieter and do the reverse during the day by closing the ceiling vents in the BR (run the # 3 AC) and opening the ones up front.

Short cycling after a minute ir 2 is because cold air is blowing on the sensor. If it immediately shuts of it’s a remote sensor issue…there was a recent thread on this titled “Outside Temperatures”.

Edited by Ivylog
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Unfortunately, there's a lot of misunderstanding of exactly what "soft-starters" are, what they do and how they work in this topic.  I won't take the time to go over each and every error but - Please, everyone, read these webpages to clear this up:
https://www.thomasnet.com/articles/machinery-tools-supplies/motor-soft-starters/

https://www.plantengineering.com/articles/soft-starter-101-how-do-they-work/

https://camperreport.com/softstartrv-questions/

Edited by Moonwink
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