Community Forums

denk · 07-13-2016, 03:22 PM

I've been reading up EMS devices but have not seen any mention of the AC voltage range, mainly low, that is not 'acceptable' to use.

I just checked the house AC voltage and was surprised it was at 107 v.

What's the low threshold to avoid?

nothermark · 07-13-2016, 03:39 PM

Typically we used 10% of nominal. That would put 107 below spec. A quick look indicates that the delivery tolerances are probably tighter than that. The "we" I was referring to was acceptance for various equipment when testing to spec. I'd be talking to my power company.

MartinP · 07-13-2016, 04:35 PM

Quote:

Originally Posted by denk

I've been reading up EMS devices but have not seen any mention of the AC voltage range, mainly low, that is not 'acceptable' to use.

I just checked the house AC voltage and was surprised it was at 107 v.

What's the low threshold to avoid?

My unit will dump AC at that voltage. Sorry but I can't remember the upper and lower limits but have lost power on several occasions due to low voltage and lose of a ground at several campgrounds.

windsorbill · 07-13-2016, 04:41 PM

Quote:

Originally Posted by denk

I've been reading up EMS devices but have not seen any mention of the AC voltage range, mainly low, that is not 'acceptable' to use.

I just checked the house AC voltage and was surprised it was at 107 v.

What's the low threshold to avoid?

I have a progressive industries EMS PT50C. it will allow power through as long as it's above 104 and below 132 volts. It will turn off outside those limits but will monitor and if the power comes back inside the window, it will re-connect.

denk · 07-14-2016, 06:02 AM

Thanks all for the information, it's helpful.

Gary RVRoamer · 07-14-2016, 08:41 AM

Quote:

Typically we used 10% of nominal. That would put 107 below spec.

Only if your "nominal" is 120v. Some areas still have only 110v or 115v power anyway. That used to be "standard" or "nominal".

My Surge Guard #40250 allows 102-132

Realistically, an RV a/c still runs ok at 107. I wouldn't want to see it too much below that, though. A long hot day at 102v is going to sorten its total lifespan a bit.

wigginsjsr · 07-14-2016, 09:32 AM

My progressive sets the range at 104 - 132 volts. I did bypass the EMS on one occasion when it was extremely hot outside. Big mistake, within 3 months compressor shot. I later ask myself why I installed the EMS only to ignore it. Never again!

TXiceman · 07-14-2016, 09:35 AM

The 120 volts, +/- 10% is generally at the parks power feed. Once inside the park, the voltage drop will depend on the wiring and number of users.

So 108 volts is generally the lowest you should see if a park is properly wired and has adequate power.

My EMS will drop off at 107 volts...like shut off the power to the RV.

Older A/C units had motors with more windings and could often run down as low as 103 volts. The newer A/C units have motors that are wound to just meet the requirements and will really suffer at 107 volts.

If you are in a park with voltage running low, switch your RV frig to gas and your water heater to gas. This may pick you up 2 to 4 volts on your incoming power and get you over the hump to run the A/C unit. You can also turn off or unplug the power converter to help out.

Ken