Low power?

Voltage drop through the extension cords.

if it drops below 108v i'd disconnect before damage is done. but what's a 'DS' and what is a 30-amp "server"? do you mean a 30-amp outlet at a campsite? but the first response is likely correct...voltage drop through the cords. did you measure the voltage at the post?

^^^ It says he's plugged into a 30 amp at his house.

I suspect DS is Dutch Star (Newmar). “Server” may be “Service”. Is it possible to move closer? You might want to consider upgrading the service to 50 amps.

As above the length of cords will reduce the voltage. Generator is properly sized for the MH providing 50 amps, and is really really close by.

For a nominal voltage of 120V, ANSI allows a range of 104.4 - 127.2 as acceptable. However, NEMA requires electrical equipment be able to operate within a range of 103.5 -126.5. Following either requirement, the OP is able to use his AC within a safe, specified range.

As an aside, the (one way) resistance of 50ft of #8AWG wire is 0.031 OHMS. The round trip resistance total would be .062 OHMS. Assuming a single A/C running at 14Amps, voltage drop is (E=IxR)=14x.062= 0.868V If both A/C units are turned on, total amps would be 28, or 28x.062=1.736V drop. With 111V in at the house, minus 1.736V drop, the voltage at the RV should be about 109V. OP claims 108V or about right.

Still within "code" range of 104.4V or 103.5V for acceptable operation.

What's the voltage if you check at the outlet?

When you apply an electrical load, one of the side effects is it pulls the voltage down. There 3 primary things that impact how much the voltage is pulled down:
- How many amps.
- How long is the electrical cable/wire run (if you coil up 100ft of cable, it still counts as 100ft)
- How thick are the wires
(there are a few other things but not too relevant to this discussion).

The air/con is generally the biggest load in an RV, so relatively high amps. (and as the voltage drops, the amps increase to compensate)
You've had to string together multiple cords, so relatively long cables.
You say it's 30amp service. Is it really 30amp service or is it a 15/20 amp household plug with an adapter. The wiring in your house counts as part of the cabling length and if it's thin, that could be increasing voltage drop.

Dropping by 3 volts is not uncommon with a heavy load like an air/con. If you are starting with a good strong supply up around 120v, that leaves you at 117v which is perfectly fine.

At 108v, that's getting borderline where I would be looking at pulling out the generator. Keep in mind, as houses in your neighborhood turn devices on and off the voltage will fluctuate, so it might be 108v while you are looking and it might drop to 105v a few minutes later.

I'm speculating a bit but if the 111v is while nothing is on in the RV (negligible voltage drop), the voltage at the outlet is likely marginal. Items you can check:
- Are all the connections in good shape with no corrosion? If you are capable, check inside the outlet and at the breaker panel for corrosion or lose wires.
- Check the voltage at other outlets around the house. If they are all down around 110v +-, it's likely nothing wrong with your RV and just that your house has low voltage. You could check with the power company but unlikely they would do anything about it.

What is the voltage at the house main panel? 111 with minimal load seems low for a grid powered home. May need the electric company to come out and verify. s/b solid 118-122

Possibly the RV water heater is on electric and pulling the voltage down.

I ran my 30 amp plug from my panel to where my trailer
is parked.I used 10/2 wire, had to run it through the
attic. I get 118/119 volts with no load but when ac runs
it drops to about 110 volts.I should have ran 8/2 even 6/2
due to the 50 ft.run and the heat in the attic during the
summer. Your voltage drops seems normal especially with extension
cords.

If those are true 50 amp extension cords, voltage drop should not be the problem on 30 amp power. Starting with 111 volts and dropping to 108 when you turn on the AC makes me think you have a supply source problem. Especially since it is ok with the generator. Make sure you have 120 vac at the outlet. And make sure the outlet wiring is good and the outlet contacts are not loose, worn, or corroded.

Consider an auto former at the RV end of the cords.

Roll your own extension cord with thicker wire.

Don't exceed 24 amps of demand.