roof AC issue, could this be causing it??

[SJ-Chris]

Greetings all!

I'm having an issue with one of my RVs and the roof AC (RVP RV Products 8000 series). This is on a 2008 Four Winds 31P Class C RV. I was parked at my house and plugged in via a 100 foot extension cord connected to a 20amp outlet in my garage. I don't think there is anything else connected to this outlet in my garage (it is a dedicated outlet for a whole house vacuum). The RV shore power line is a 30amp line/connector. I have a simple plug connector that allows me to plug in the 30amp plug into a standard 120v extension cord.

The 100 foot extension cord is a fairly standard gauge but seems lighter duty (thinner compared to some of my other heavy duty extension cords) and it is pretty old. And of course the 30amp plug on the RV has another ~30 feet as well. When plugged in to my home (aka shore power from a home outlet) the roof AC seems to struggle a bit. It will run for several minutes on High and seem normal, but then it will suddenly drop down to Low (perhaps even below what I would expect if I set it to "Low" on the thermostat) and then after 20-30 seconds it might jump back up to full force (High). It has also tripped the AC breaker on my converter box (Parallax) a few times if I have it running for more than 10-20 minutes.

I just did an experiment...I needed to drive to dump my RV waste tanks and run a few errands so I turned on the generator (4000w Onan) and ran the roof AC the entire time (for about 1.5 hours) off the generator. I had the roof AC set to High. It seemed to run perfectly the entire time. It didn't once struggle or drop down to a lower speed and it didn't trip the AC circuit breaker in my converter panel. I would consider it as having functioned completely as expected. That got me to thinking....could it be that my long 100 foot, older light-weight extension cord is causing my issue? Could there be some sort of voltage drop happening over that long distance and it is causing my roof AC to not have enough voltage/amperage? Do my symptoms seem to point in that direction? I just felt the extension cord and it even felt a little warm (could this be indicating that it is not heavy enough gauge for the load??).

Let me know your thoughts. I want to make sure my roof AC is functioning properly of course, and I can always bring it to an RV mechanic to have them take a look, but people on here are always incredibly wise and helpful so I thought I'd check with the RV.net community first to see if I can get some pointers/suggestions.

I do have a heavier duty extension cord and I think I'm going to give that a try to see if I have the same symptoms or not.

Thanks in advance! Let me know your thoughts.
Chris

[RSD559]

Just for giggles, what size wire is in the 30amp cord that comes with the RV? Mine is pretty thick. I actually Amazoned an extension that is the same thickness. I use it when I use the generator in the bed of the truck. If you want to invest in a 10amp cord, check out Harbor Freight. Hey! No more giggles!

[pnichols]

Your extension cord is too light for 100 feet plus the RV's built-in 30 foot shore cable to the air conditioner.

Use a 100 foot heavy duty contractor's extension cord to plug the RV's 30 foot shore cable into and you should be just fine.

[ksg5000]

Always important to check the voltages when running air conditioners off of questionable power supply - if the voltage drops too low (<108?) it can damage the air conditioner. Many use a Kill a Watt to monitor the voltage.

[pianotuna]

SJ-Chris,

What is the voltage when running with the heavier cord?

[SJ-Chris]

Update: I tried my heavier duty extension cord. It has a tag which says it is rated for 15amps (and it is certainly thicker than the other extension cord I was using). It doesn't have a gauge indicated on it though. I believe it also might be 25 feet shorter than my other extension cord.

I plugged it in and turned on the AC. After sitting in the RV for about 30 minutes it seemed to work exactly as expected. I will let it run for another hour and see if all appears well. If so, I think I'm back in good shape and with your help solved yet another issue.

RVs seem to be a never ending learning opportunity! 🙂

Thanks again all!
Chris

[Johno02]

Quick answer - YES! Lucky you haven't burned the whole thing down. I have a 30A 25' extension plugged into a 30A fused outlet. With the RV cable, total about 50'. I can one one AC unit and a few lights OK, with no voltage drop.

[jfkmk]

You most certainly figured it out, and every is confirming it was your issue.

[wa8yxm]

Extension cords are often 16 or even 18 Gauge. 14 gauge is the minimum for 15 amps over a 100 foot run (From the breaker box, not the outlet) and 12 ga is what I use for my 100' 15 amp cord.

Sears and K-Mart, while they last, sell a 12ga cord with a locking button on the outlet. you push the button when you plug in the adapter or unplug it. Very nice.

[pianotuna]

You need way thicker wire #8 would work. You may have caused some damage to the air conditioner already.

[Mandalay_Parr]

Try your other cord and see.

[ScottG]

Good advice from both posters above.
I would not use that extension cord to run anything more than a few lights and a TV - never the AC.

[Big_Katuna]

You need to measure the AC voltage inside the trailer.

You need 10 ga wire for that length and few ext cords are 10ga.

I hope you understand that low voltage can permanently damage the unit.

[2oldman]

Yes, the cord and length is a problem. You have low voltage. 100' is excessive.