RV air conditioner switches to inverter on gen power – Update

Hi Dave,
I thought I would give you an update on my last question to you regarding my air conditioner unit always going to battery when turned on and not plugged in to a post.

After some more troubleshooting, it turns out my problem was with my EMS (Electrical Management System). I use a Surge Guard 30-amp plug EMS. I was using it between my generator and my transfer switch, which is a manual plug-in. When I first got the EMS it worked perfectly in between my generator and my coach. I figured if I filter the power between coach and pedestal I should filter the power coming from my generator.

It turns out that my EMS is no longer working properly in this configuration. As soon as I turn on the A/C, my EMS trips and stops all power for 7 seconds. Then, when it comes back on, it trips again, resulting in a 107-second delay before attempting to power on again. This would explain why, when running the A/C, it would flip to battery power.

By removing the EMS from the genny circuit, the A/C stays on and my inverter charger continues to charge my batteries, and there is power to the coach. Kinda weird that it worked before but not now. In any case, I will look for a new EMS to replace my 7-year-old unit. —Steve, 2010 Fleetwood Jamboree GT

Hi Steve,
Thanks for the update. [Here’s a link to yesterday’s post on this topic, for those who missed it.]

The Surge Guard, which is owned by Southwire, should look similar to this.

How an electrical management system works

What makes an electrical management system such as the Surge Guard work are joules, which is the amount of energy a surge protector can absorb. This model has 2650 joules of surge protection. The higher the number, the more energy it can absorb, or the longer it can absorb a surge and still work. It has an LED reading that should show wiring issues, so I still have a couple of questions.

Does the Surge Guard work when the shoreline cord is plugged into a campground source? If it does, the issue is with the generator and a possible open neutral. This is common with portable generators that have a “floating neutral” and has been addressed by Mike Sokol many times. He developed a Ground Neutral Bonding Plug that is sold by Southwire and others. An open or floating neutral will be detected by an EMS as a fault and shut the power down.

Air conditioner wired through the inverter

Your air conditioner is evidently wired through the inverter to draw from the house batteries. It is possible that the air conditioner start capacitors are getting weak due to the high amp draw during initial startup and drawing even more amps than normal. This could also make the generator surge for the higher draw and cause the issue.

I would make sure the return air filter is cleaned and not obstructed as well as the evaporator coil. Any airflow restriction will also increase the amp draw and could cause an issue.

If it is the Surge Guard EMS, you should get the same shutdown and switching to inverter as you are seeing with the generator. If not, it is the generator and possible power consumption at startup.

Just got this tonight from Steven

Here’s another update on this issue.

I currently have a Surge Guard 34930 – 30amp EMS. It was purchased back in 2018. It has worked and still works like it was brand new at least to my knowledge. As far as I know I have not had any surges to the EMS unit. My RV when purchased new to me back in 2018 I had the converter removed and a new 2000watt Pure Sign Inverter/charger by Samlex installed. It was wired up professionally. Yes I also had two extra batteries added to my bank at the same time. I have since replaced the original batteries with four Rolls 240amp LAB’s.

I recently took the RV out to a Classic Rock festival, where the Temps daily were around 35c. So we definitely had to run the Air conditioner for the three nights and four days we were at the festival. Now I plugged the genny into the manual transfer switch without the EMS attached, and started up the genny. I waited for it to warm up for about 5min, then tried to turn on the air conditioner. On every attempt the Inverter would crash and say Low Battery Voltage warning.  I would then have to shut everything down and restart. In the end to get the air conditioner started I had to wait on the genny for about 20min to fully warm up before the entire system would take the extra surge of the air conditioner. You may be right that the capacitors on the air conditioner may need to be replaced. I have also purchased a SmartStart for my Air conditioner ( the hard wired kind) and will install this shortly to see if this makes starting the air conditioner a little easier. I have not tried a pedestal start as I have not been in a campground with full hookups or electrical. I mostly dry camp or boondock. I have not yet tested for an open or damaged ground/neutral yet, but will most likely on the weekend, and will let you know my results, as well as the result of installing the SoftStart.

Cheers,

Steven

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