inverter vs shore power

[Dick Skeers]

I'm plugged into my son's 20 amp garage outlet which shows 122 volts with the household refer running. however, if i turn on the electric heat or microwave, it immediately drops to 108. if i disconnect shore power the inverter by itself registers 124 to 126 and drops very little when the same electrical loads are applied. So, apparently when plugged in the inverter is bypassed? Is there a way to have the shore power just replenish the batteries and operate the coach from the inverter?

[formerFR]

no, you can’t have two different power sources at the same time - which is why the inverter has it’s own built in transfer switch

[formerFR]

the other option would be to attach an external battery charger, leaving the coach on the Inverter power - just like when you have off-grid solar

[formerFR]

I doubt, tho, that you need to be running electric heat on the inverter - too many amps for too long - the charger won’t be able to keep up

[valleyduo]

Where are you getting this 108 reading? If it's on the camper end you may need a heavier extension cord. Voltage is usually drawn down by resistance as opposed to quantity of items using it.

[formerFR]

right, your ext cord to the RV may be too small

[Wolf Alaska]

Dick, if your shore power is 20 amp 110VAC then you will have to watch your loads. I ran my Coach House Type B for years from an adapter on my mother's porch light...so it can be done.

If your refer runs on 5 amps, then you have 15 amps left. Battery when full likely draws 2 amps to run the 12VDC lights. Now, 13 amps left.

A coffee maker draws 12 amps 110VAC. So does a 1500 watt electric heater. On low, a heater may draw 750 watts or 6.2 amps @ 120VAC.

There will be little reserve if you are running an electric refer + a heater. If the refer is propane, run on propane, the 12VDC draw is very low, the refer works better, & it's safer.

Let's Roll !
Wolf

[Wolf Alaska]

PS: if you load over the 20 amps, expect the house circuit breaker to trip OFF, & you will have no shore power. Your inverter may pick up the load & you may not know that until your battery(s) run down.

[cavie]

Originally Posted by Dick Skeers

I'm plugged into my son's 20 amp garage outlet which shows 122 volts with the household refer running. however, if i turn on the electric heat or microwave, it immediately drops to 108. if i disconnect shore power the inverter by itself registers 124 to 126 and drops very little when the same electrical loads are applied. So, apparently when plugged in the inverter is bypassed? Is there a way to have the shore power just replenish the batteries and operate the coach from the inverter?

what size is your extention cord. and how long is it. It's called voltage drop.

[KRedburn]

1st off your extension cord is too small. For 20 amp should be 12/3 or better 10/3 would be better.

2nd Your inverter/charger is probably set for a 50 amp circuit under the power share menu. You should reset this to 5 amp on a 20 amp circuit. This will result in only 5 amp being used for recharge of batteries and the rest for usage.

3rd. A portable heater is 1500 watt which is 12.5 amp at 120 volts. At 108 volts it would run 13.9 volts. Your frig most likely requires somewhere around 7 - 9 amps to run.

This puts a 120v 20 amp circuit very near its max. A light cord (many extensions are 14/3) will add to the issue of lack of power.
Also, cut back any power usage items (ie. microwave shut breaker off, electric heating of hot water, etc.)



So, if you only have a 20amp circuit your extension cord must be 12/3 or better and as short as possible.

[wanderer44]

What size is the cord you are using to plug into the 20 amp outlet? Could it be too small or too long for the load you are pulling????

[ScottBrownstein]

Maybe, but it all depends on the specific inverter installation. If you have a converter/inverter combination...the answer is NO! Too many other possibilities to give you a simple answer. The others are correct, your extension cord is too small and you are drawing enough current to drop the voltage to 108.

[jimmoore13]

This does not address your actual question....

I have a hunch that your shore power may be only 15 amps. Check the breaker.

Also check for other household loads on that circuit. It's likely that there are many loads on that circuit, including a second fridge or freezer, other "garage" appliances, and so on.

But an electric heater typically produces 1500 watts. That's pulling 12.5 amps all by itself. If your shore power circuit is wired with 14 AWG for a 15 amp circuit, the voltage drop should be expected if there are several other loads sharing the 15 amps. Even with 20 amps, you have fewer than 8 amps to spare with that heater running.

And then there's distance...how many feet of wire from the circuit breaker to your heater? Every foot counts. Your rig's cable may be 10 AWG wire, but is there a lead cord from the house to your rig's 30 amp to 15 amp plug adapter? If so, what gauge is it? #10 is better. #12 will do in a pinch.

Also, what's the condition of the outlet? A worn outlet won't transmit power like a new one. I once had the power company diagnose a brownout in my home only to discover that the meter and meter box (a male plug and female socket situation) was decrepit enough to cause a 20 volt drop from corrosion and heat-induced fatigue in the connection. Replace the duplex outlet, make sure the screws are tight on the wire (don't use the push connectors) and try again. Also check the connections in the panel. Shut off the main breaker and go to town with a screwdriver tightening every terminal on the panel...every screw.

So, if the ONLY load on the circuit is the electric heater (or microwave) and the voltage drops 10 to 20 volts, it's time to check the household circuit from the panel to the rig. A 15 amp circuit should NOT experience that significant of a voltage drop with a 12.5 amp load unless something's wrong. Push comes to shove, install a new breaker. And if that doesn't work, you have your work cut out for you. Get a 10/3 AWG extension cord and plug in to other circuits in the house and check your voltage in the rig. If things improve elsewhere, the home's electrical circuit feeding "your" outlet is suspect...with a loose connection in a junction box, a bad daisy chain from outlet to outlet, or something else. At any rate, that's a fire waiting to happen.

If you need heat in your parked rig, perhaps you should revert to the furnace. An electric heater may be convenient, but they really tax your power supply. And if you're pulling 1500 watts through an inverter drawing off batteries, you're pulling over 120 Amps from your battery bank. It may deliver that, but not for long.

This calculator is helpful. Bear in mind that power pulled through an inverter has a 12 Volt source...the batteries...not a 120 volt source. Use 12 volts in the calculator (or X10 on 120 volt amps).

There are many such charts, but this is a handy guide for estimating power delivery based on distance and wire gauge. These rules apply to household wire running from the breaker to the outlet just as much as they apply to the run from the outlet to your rig.

Good luck. You may have stumbled on a problem in the home's wiring, or you might be using a light weight (16 AWG) extension cord, or you might be expecting too much from a 15 or 20 amp circuit. But it would be wise to figure out which it is and deal with it before bad things happen.

[Dick Skeers]

thanks for all of your responses:
there is no extension cord, we are connected directly via our 50 am cord adapted to 15/20 amp plug. so in this situation with inadequate shore power, and wanting to run multiple appliances, I'd best disconnect shore power and work off the inverter. when back to a lighter load I re-connect and refill the batteries?

[formerFR]

if you are concerned about the drop in voltage you are seeing, then you'll have to find another circuit to pull power from, as it looks like the one you are using is having issues, regardless of whether you are using an extension cord, or just a 50/15amp adapter(of course, the adapter itself could be the issue)...

otherwise, I wouldn't worry about it, as your heater will not really care if the voltage is not high enough - it just won't operate to it's full capacity.
If you want to use the microwave, though, that's when you might want to shut down the heater while you do it. You might find that the voltage then does not drop.

personally, I have no way of knowing voltages coming into my rig, and have never had any issue for the over 4 years, 86,000+ miles, and many, many different campgrounds and power supply options. We've plugged into many 15amp or 20amp outlets, usually with lengthy extension cords, many, many times.

[FFred]

"I'd best disconnect shore power and work off the inverter. when back to a lighter load I re-connect and refill the batteries?'

Unless you have many hundreds of pounds of house batts this will not work.

To make 10Amps of 120V will take about 110 Amps from the 12V battery bank,not possible for very long.20Amps would double the load.

Forgetaboutit.

There is a short term very expensive solution .

Some inverters can be purchased with a boost pass thru setup , where the incoming power is augmented by the inverter using the coach batteries.

But the math is the same over 100A from the batt to make 10A of 120V.

Just watch your loads , or go to a better power supply.

[sseaner]

Could also be a faulty 50/30 adapter.