Electric Heater Question

Gdetrailer wrote:
Nvr2Loud writes “You are still wrong.

50 amp two pole breaker on a 240 VAC circuit will only allow 50 amps of total power draw. The breakers are NOT additive. I have no problem with your math, 240 volts x 50 amp is 12,000 Watts, I have a problem with your statement that a 50 amp trailer actually has 100 amp draw. It is a confusing statement, since we don't break down 240 volt appliances by amperage per leg. A 30 amp 240 volt heater will run 15 amp per leg, not 30 amp per leg.

At 240 Volts, the maximum draw is 50 AMP, not 100 AMP.

I see what you are trying to explain, but 50 amp service is 50 amp service, not 100 amp, period.”

You plain don’t get it.

Your are confusing 240V ONLY with 120V/240 SERVICE, there IS a difference.

Here in the States, RVs TYPICALLY DO NOT USE 240V, they USE 120V, the panel ACCEPTS 120V/240V as an input but distributes only 120V.

A RV “50A” shore connection IS NOT USING 240V ONLY, instead they are using as TWO SEPARATE 120V legs at 50A connections and the "service" is known as 120V/240V.

A 50A RV shore connection panel is wired the same way you would like a SUBPANEL. This means there is FOUR WIRES (L1, L2, NEUTRAL, EQUIPMENT GROUND).

L1 and L2 ARE THE 120V “legs” which if you put a meter across those legs you would indeed get 240VAC and if you plugged in a 240V ONLY APPLIANCE you would only get 50A AT 240V…

A meter from L1 to NEUTRAL will read 120V and be capable of 50A (6,000W).

A meter from L2 to NEUTRAL will read 120V and ALSO be capable of 50A (6,000W).

The total amount of 120V load draw you can get is 100A or 12,000W. Granted you are limited to TWO separate 120V draws of 6,000W for a TOTAL of 12,000W but is far more wattage than what a 120V 30A and 120V at 20A can supply.

In a RV you are using TWO 120V legs at 50A EACH LEG (6000W EACH LEG for a TOTAL OF 12,000W)..

120V AT 100A IS 12,000W which IS THE SAME WATTAGE AS 240V AT 50A (12,000W).

This is not the same as grabbing two 50A 120V circuits off the SAME leg, if you used the SAME leg your NEUTRAL MUST BE TWICE THE SIZE (which it is not and I am not bothering to explain that one to you since it most likely would make your head explode..).

A TRUE 240V ONLY appliance (home water heater as an example) there is NO NEED FOR THE NEUTRAL AT ALL. Your RV IS NOT A TRUE 240V ONLY APPLIANCE.

The last time I checked we do not live in Europe so we do not typically have 240V only devices like hair driers, TVs and such, pretty much all normal home electrical devices are setup for 120V.

So, to be extremely clear, using ONE 120V 30A CIRCUIT (Shore cord/panel) AND ONE 120V 20A CIRCUIT (extension cord plugged into a 20A outlet) DOES NOT ADD UP TO A 120V/240V at 50A shore connection. That configuration only gets you HALF THE WATTAGE of a “50A” 120V/240V shore connection.

One 120V at 30A panel and one 120V 20A extension cord only gives you 6,000W (this is equivalent to only ONE LEG or ONE HALF OF THE WATTAGE CAPACITY of a 120V/240V 50A panel).

One 120V/240V at 50A shore connection gives you 12,000W, 120V at30A and 120V at 20A DOES NOT GIVE YOU 12,000W and therefore IS NOT the same..

Your confusion is pretty much normal, many folks can’t understand as to why a 5000W 120V/240V generator will not have enough power to start their A/C..

The reason.. 120V usage you only are using ONE leg of the gen which can only provide ONE HALF the rated output of the 5K gen for EACH leg.. Basically the gen only supplies 2500W of the 5Kw on EACH 120V outlet (leg).