Connecting a 110 Volt 300 watt generator to a 220 Volt panel

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snipped-for-privacy@aaronj.com wrote:

Running all three at same time could overtax a cheap 3KW genny.

no.. you'll probably overload your wires and create other hazards.

As for the electric water heater.. I'm assuming this is single element 3500 to 4000 watt heater?? Using a 20amp.. 220/240v circuit? Does the heater have a cut off switch mounted in a nearby conduit box?
If answer is yes to all three.. and you have the tools and the wiring know how.. You''ll need...
a. 20amp three position(center off), dual throw, dual pole switch... ~$50 at electric supply store. (Not avail at Home Depot or Lowes.. ) b. 1/2 in. Straight NM Clamp Connector c. 8ft ..14/3 120v cord & plug ... note: 12/3 is better (but rare).. d. Yellow spade connectors for 120v cord.
Using a ohm meter, insure three position switch always breaks from one pole before making with the other pole.
Use standard wiring conventions. (crimping, grounding, securing.)
Rewire hot water heater wire to CENTER poles of 3pos DPDT switch.. (both of them) Feed both legs of house 220/240 to one set of switched poles. Connect both hot and neutral 120v cord using crimp terminals to opposite poles of 3pos DPDT switch. Reassemble.
Label (center) off, 120v and 240v positions of your new disconnect switch. Note: DPDT switches connect poles opposite of switch position.
Test your new setup. (Use several gals of hot water and then time utility meter spin rates for both voltages.)
Make a Insulating cover for plug, roll up cord and wait for the next big power outage. Connect to gen using shortest possible 12 or 14 Gauge 3 wire extension cord and set HW to 110v mode.
Disclaimer:... If you don't understand any of the listed instructions. You probably shouldn't attempt this mod.. Hire an electrican to do the work.
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Water Heater has 2 4,000 watt elements, upper and lower.
AFAIK dual elements are energized one at a time.
If powering with 120 VAC, the power will be about 1,000 Watta.
With 1KW into 54 Gallons of water, there is not a high probability of boiling the tank.
Why wouldn't a pigtail 110 VAC receptacle wired across the lower element/thermostat be sufficient as a connect point if the main breaker and the WH breaker are both in the OFF position?
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Connecting a separate 110v source without physically disconnecting the 220 circuit is an accident just waiting to happen. You may not be the person who flips the circuit breakers back on.
As for boiling water, if 1KW is consumed long enough it can increase tank temp to boiling point, but it will become way too dangerous long before that point. As hot water over 125 degrees F represents a scalding hazard.
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As hot water over 125 degrees F represents a scalding hazard.
That is why thermostats were invented.
54 Gal of water weighs 448 pounds.
heating 448 pounds water at 70 to 120F requires 50 x 448 or 22,410 BTU's.
22,410 / 3412 BTU/KWH = 6.5 hours.
The generator gas tank will be empty before a 54 gallon WH would begin to boil, if there was no thermostat involved.
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snipped-for-privacy@aaronj.com wrote:

You're the one making a statement about not wiring in a thermostat.

ASSumption... that you're starting out HW filled with 70 degree water.
Which is an improbable event to reoccur more than once.. Most people won't tolerate 70 degree shower for very long. Hot water in the heater isn't going to magically cool down to ambient overnight.

For how many days???
2 days... 4 days.... a week... two weeks... ???
After Wilma's eye wall hit us hard (twice).. Our area was without grid power for 13.5 days ! Next block over was without grid power for 17 days !!!
Each morning I ran genny for 4 to 5 hours, make Breakfast & lunch.. power frig's, charge bat's..
And another 4 to 6 hours in evening, power frig's, make dinner, hot water(for morning showers), charge bat's, watch some TV.
For the most part, it took 110v mod running w/genny just a couple of hours to bring a 30 gal WH back to it's thermostat set point and disconnect.

ASSumption.. that you have a small fuel tank and you don't refill it. ASSumption.. that you are always aware of the temperture of water in HW heater.
Bypassing critical safety features is a good way to hurt someone..
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Oh!
I see the problem, you misunderstood.
"Why wouldn't a pigtail 110 VAC receptacle wired across the lower element/thermostat be sufficient as a connect point if the main breaker
and the WH breaker are both in the OFF position? "
The thermostat WOULD be in control.
Sorry.
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