Electric Heater lowers Voltage ??? HARMFUL ???

HadEnough wrote:
Where are you measuring this voltage drop?

It can be dangerous because a drop in voltage means an increase in amperage assuming the same power output.

It's sometimes a precursor to an electrical fire.

I absolutely detest portable electrical heaters! My father was a Firefighter and saw way too many fires caused by them.
I preparation for full timing, we invested in the Cheap Heat System. I will say the initial cost is not exactly cheap, but heating with an electric furnace is awesome.
We will from time to time be on a 30 amp service, so I did purchase the auto switch over unit as it saves me about 20 to 30 minutes of work in tight spaces switching to the lower voltage.
In our mid range Copper Canyon 32' 5er, on 30 amps (1,800 watts) it will maintain a set temp down to about 33 degrees outside. To raise temp, we switch to gas, then back once at the higher temp.
We have been down to low 20's on a 50 amp service (5,000 watts), and never had an issue.

DrewE wrote:

Of course, the 30A and 20A receptacles in the campground power box are only single phase, so measuring the voltage at them only checks one of the two legs. Often they are wired to opposite legs so checking both can verify both legs, but I'm sure that's not universally the case.

50A is also single phase ;)
It's split phase Discription

It could be a sign of a bad connection in the wiring somewhere.

A good first step in troubleshooting would be to move the voltmeter around to every outlet, including the one on the pedestal. You should see some that aren't affected as they are on the other leg of the 50A service. Might give you a clue to where the problem is.

If you see any of the outlets increase in voltage when the heater is on, immediately shut the heater down, shut off power at the pedestal and disconnect your power cable. That probably means a missing or inadequate neutral connection which can cause serious damage.

In general, a modest voltage drop in response to a significant load is nothing more than evidence of Ohm's law in action. If it's a volt or two, it's nothing at all to worry about.

If it's several volts, the lower voltage is not in and of itself a problem in most cases (provided it's still in the right nominal range, not much below 110V), but the amount of change suggests a relatively high resistance between the heater and the power source. That could simply be long wires in the campground and not a real problem. It could also be a dirty plug or loose connection somewhere that's getting quite hot due to the power its dissipating, and that is very much a problem.

One good thing to check is to see if the voltage at the other outlets in the campground electrical box is drooping and how much. If you see an equal drop there, then the cause is in the campground wiring and there's not much you can do about it. If the voltage remains pretty much steady, then check your connections carefully: see if the plug is warm, check (with power off and disconnected!) that the wires are tightly connected in the breaker box for the RV and none of them look overheated, etc.

Of course, the 30A and 20A receptacles in the campground power box are only single phase, so measuring the voltage at them only checks one of the two legs. Often they are wired to opposite legs so checking both can verify both legs, but I'm sure that's not universally the case.

Is that the same outlet, or same circuit breaker, that the heater is plugged into?

Put the meter on a different circuit, measure with heater off and heater on
And post the numbers here

If you have more than one
Make sure they are on different circuit breakers

A 50 amp service should have no problem with a pair of portable heaters

Sorry but running a couple of space heaters in a 50A rig is NOT going to cause a fire.
Space heaters (and any other resitive load) use less current as voltage goes down.

You gotta tell us how much the voltage drops to before we can say if it's harmful or not. Dropping from 120 to 110 is no problem for example. Dropping to 90 is a problem. Also, measure at the source; where the RV plugs into. Is the voltage drop at the source so all electrical in the RV is dropped, or is it on the circuit the heater is on only. If the latter, then it's just undersized wiring in the RV to run that heater. Find an outlet that has a higher rated breaker as that will have heavier gauge wire and less voltage drop. If it's at the source then you may be plugged into 50amp circuit but you sure aren't getting it. An electric space heater has a typical amp draw of 12 to 15 amps, leaving you a reserve of at least 35amps for everything else.

Where are you measuring this voltage drop?

It can be dangerous because a drop in voltage means an increase in amperage assuming the same power output.

It's sometimes a precursor to an electrical fire.

A Vdrop is harmful to some electronics and motors. The important part of the equation is knowing what voltage your seeing.
Just because the voltage drops, which is normal in any circuit, doesn't mean it's a problem.

Depends on the severity of the drop. Space heaters save something... propane I guess.. but they don't heat the basement where the pipes are. Also, they draw a lot of current and if other high-wattage appliances come on at the same time you can find your shore cord plug melted.