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ColoradoBnd · 08-03-2017, 01:53 PM

I have my Mountain Aire parked in the back yard about 200 ft from the house. There is a power pole (25A outdoor circuit) 50 ft out from the house and a 150 ft extension cord that is 10/3. I set the magnum shore power to 20 amps and also set the EMS on the Newmar to 20 amps. I have a Progressive Ind EMS-PT50X in line on the extension cords to the house.

I am showing about 109V (about 5% based on 115V) on the PT50X and I seem to be able to float charge or run the 1 front A/C at a pull of about 15 amps on the Newmar EMS. I am not running the charger and the front A/C at the same time.

I am assuming that the PT50X will ensure that I do no hurt the coach in any way. Is that correct? Am I missing something?

I just want a double check to make sure that the voltage is Ok prior to running the A/C or charger at length. Thanks in advance.

nothermark · 08-03-2017, 02:02 PM

The voltage spec is generally 120 +- 10%. That would make 108 the lower end it should pass without faulting.

If the power pole circuit has more than one outlet I would be inclined to check the voltage there just to see if a bigger cord would do any good.

ColoradoBnd · 08-03-2017, 02:08 PM

The PT50X faults the voltage at 104 volts. If I assume 115V at the pole, the voltage calculators predict right at 108 volts. Thank you very much for your response.

APhotoWizard · 08-03-2017, 02:10 PM

The nominal design voltage in the US is now 120 volts even though all the tables state 110. I would not use your configuration for my air conditioner. The voltage is too low and it will struggle when the weather is hot.

You can see from the table below that you need a larger wire, and I'll bet the wiring for the outside plug is also under sized for your needs.

I would devise a better plan.

Have a great day - Jerry

http://www.cerrowire.com/files/file/voltagedrop.pdf

ColoradoBnd · 08-03-2017, 02:28 PM

Just measured 119V at the pole.

nothermark · 08-03-2017, 02:48 PM

I'd be inclined to either get a bigger cord or set up a double extension cord setup. Even putting a 50 ft 30 or 50 Amp cord in the mix and a shorter extension cord would make a significant difference.

ColoradoBnd · 08-03-2017, 02:55 PM

I can do that from the pole to the coach. The house to the pole would still be a choke point. I guess it would still help on the 150' run where I loose a lot of voltage, right? I know I have close to 119V static at the pole. Called dometic and they didn't help much. They mostly quoted the amps required which is not much of an issue. I will run 2 10awg from the pole tomorrow and see what my voltage does.

ColoradoBnd · 08-04-2017, 12:20 PM

I called Newmar today and they had the exact answer. They are impressive. Anything above 105 V is acceptable. So as long as you are using a product like the EMS-PT50X there are no worries on voltage.

computerguy · 08-07-2017, 10:44 AM

Quote:

Originally Posted by ColoradoBnd

I called Newmar today and they had the exact answer. They are impressive. Anything above 105 V is acceptable. So as long as you are using a product like the EMS-PT50X there are no worries on voltage.

Hmmm. "no worries". Famous last words.
If it were me and I were going to have this situation on a regular basis I would be planning on premature failure of any device being run.
Lower voltage means higher amperage. That equates to higher heat and heat is any electronics enemy.
Call the AC manufacturer and ask them directly.
Best of luck to you and your decision to use this setup.

xrated · 08-07-2017, 10:57 AM

Quote:

Originally Posted by ColoradoBnd

I can do that from the pole to the coach. The house to the pole would still be a choke point. I guess it would still help on the 150' run where I loose a lot of voltage, right? I know I have close to 119V static at the pole. Called dometic and they didn't help much. They mostly quoted the amps required which is not much of an issue. I will run 2 10awg from the pole tomorrow and see what my voltage does.

The key word here is "static" or no load voltage. If the A/C unit is being used, and the distance of cord that you are talking about is being used, you will get a fairly large voltage drop when the load is applied. It may or may not operate, but running any AC motor on low voltage (if the EMS doesn't take it off line) is not good for the motor AND will result in the motor windings getting hot. Of course, the more load the motor sees, the higher the current will climb and it will eventually damage the motor windings......if the EMS doesn't drop it first.

nothermark · 08-08-2017, 01:01 AM

Quote:

Originally Posted by ColoradoBnd

I can do that from the pole to the coach. The house to the pole would still be a choke point. I guess it would still help on the 150' run where I loose a lot of voltage, right? I know I have close to 119V static at the pole. Called dometic and they didn't help much. They mostly quoted the amps required which is not much of an issue. I will run 2 10awg from the pole tomorrow and see what my voltage does.

I wonder how it worked out. Should have cut your voltage drop from the pole to the RV in half or around 114 VAC. That should be manageable. If that is a long term setup think about burying some #6.

ColoradoBnd · 08-08-2017, 11:44 AM

I doubled up on the #10 extension cord to improve the voltage drop. Now I have to find a male-male-female #10 adapter. Haven't found one yet. I guess I will have to make one myself.

Duner · 08-08-2017, 10:08 PM

It's not clear to me which end of the cord you have the Progressive EMS. Near the source or right at the coach end? If you have it measuring voltage at the pedestal and then running the long cord to the coach, it's not seeing the voltage that the coach is actually getting.

I have a Hughes Autoformer to boost low voltage and the built in Progressive EMS wired in after the Hughes and both inside my power compartment. So EMS sees the voltage after the power cord and before it gets distributed inside the coach.

If you are measuring 108 volts with the ac running, then it's very probable that when the ac compressor is starting the voltage is dropping a whole lot more during startup. With 11 volt drop in the cord and connectors (119-108 = 11 v) in the steady state, then my guess is an additional drop of 5-10 volts during motor startup. Anything below 100 volts at startup will shorted the life of the a/c unit. Ditto with the microwave.

A few years back I was at my cousin's farm for 3 months. I used two 50 ft extension cords thinking the Hughes will boost the voltage back up so I could use my basement a/c in heat pump mode on the colder nights. After being parked for 2.5 months I was braking camp and the connection point where the two cords were plugged together would not come apart. The plastic plug/socket was melted together at the surface. It took box cutter to separate them. Running anything near 20-30 amps on extension cords is asking for problems.