Conneticut Electric Transfer Panel EmerGen Switch

I have a 10-7501 Emergen manual transfer switch for my generator. I want to hook my hot water tank to this panel for use when the power is out during our hurricane season. Here's what I have - the hot water tank says 4500 watts on the upper and 4500 watts on the lower for a total of 4500 watts. Wired at 240v - if I did my math right, that should be about 18.75 amps. Currently it is on a 25 amp breaker on my main panel. The Emergen switch has 20 amp breakers. So if I use the switch bar to combine two 20 amp breakers to pick up both wires, one on each breaker, on the Emergen panel, I should be ok, right? My generator is rated at 5250w, so I know that all other breakers on my Emergen switch need to be off while the hot water tank is on, but I only plan on running the hot water tank maybe for an hour every other day. Thanks much fo your responses.
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On my Generac 6 circuit the 2 center breakers are prewired for locking together for 220. Or separate 120. Yours might be this way also, my panel was prewired so it was easy, I dont know if yours is
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The switches in your transfer panel are to light for the water heater. you need a double pole switch rated at 30 amps or you'll burn it out. Keep in mind that the electricity from the utility company is going to run through your transfer switch as well, so you will constantly be overloading the 20 amp switch, not just when the generator is in use

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My transfer panel is prewired and designed for 220 heavy loads, yours may be , call the manufacturer.
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"Here's what I have - the hot water tank says 4500 watts on the upper and 4500 watts on the lower for a total of 4500 watts. Wired at 240v - if I did my math right, that should be about 18.75 amps. Currently it is on a 25 amp breaker on my main panel."
Thats 18.75 amps per heating element. Aren't these normally wired so that both elements can be on at the same time? That would then be 37 amps on a 25 amp breaker?
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Not usually in my experience. The upper stat should be set higher and only works when there is a large demand. Most of the time the lower stat (set ~5 F less than the upper) is the one that runs. At least on the ones I have seen.
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"Not usually in my experience. The upper stat should be set higher and only works when there is a large demand. Most of the time the lower stat (set ~5 F less than the upper) is the one that runs. At least on the ones I have seen. "
The issue isn't what happens MOST of the time. The issue is whether water heaters are usually wired so that both elements CAN be on at the same time. If they are, then the circuit and breaker need to be able to support both elements at a time, not one.
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The thermostats are interlocked so that only one element can be on at a time.
Otherwise, not even a 30A circuit would be big enough for a 4500W HWT.
Note that it said: "4500 lower, 4500 upper, 4500 total". Meaning, it can't be more than 4500W.
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Both elements are never on at the same time. And with utility power running through it, it has never thrown the breakers. Hope this helps
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DW wrote:

Depends on how it may be wired. Many water heaters have the option of having both to come on independently which means that can be on at the same time. Most come factory wired in cascading operation where one is off when the other is on.
That can mean the difference of 4500 watts or 9000 watts. Of course if not wired can be for the latter operation so that only 4500 watts would be needed at any time.
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It is not likely that you have 240 volts coming into your house. The voltage coming in is probably somewhere between 208 and 220. In that case the calculated amperage draw will be higher than 18.75. I suggest that you put an ammeter on the circuit to see what the actual load is. I'm guessing that it may be lower than what you calculated.

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Uh, no. The voltage will be somewhere between 230v and 250V approximately. The utilities are required to provide 240V +/- 5% or so at the panel.
208V is an entirely different type of electrical service (part of a three phase circuit), most often seen in industrial/commercial situations, and is fairly rare in residential situations. Extremely rare in detached homes.
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Our voltage at my house is 248 volts. When I lived up north, it was commonly about 220 volts due to older transformers and power distribution systems (power company) It all depends on where you are. Around here many condos are fed with 3 phase. Each unit gets single phase 208 volts.
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How is 4500w on the top and 4500w on the bottom a total of 4500w? I get 9000w.
My water heater is small and draws 23a, so I expect yours is probably 37a.
Just in general, resistance heating is not a good use for a generator.
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Elements are powered either/or, not both. Thus 4500w & 4500w elements draw 4500 between them.
IMHO resistive heating is lousy, inefficient use of energy input. Max overall efficiency about 30%. One reason gas costs so much less.
Too bad you can't use generator's waste heat (exhaust) to heat the water! About the same actual power (energy rate) available there as at alternator output.
J
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I learn something new everyday, mine had just one element. What is the point of two elements then?
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I suppose because the hot water rises, the upper thermostat powers the upper element, then when its temp is satisfied it disconnects power and sends it to the lower thermostat which powers the lower element. They never work at the same time.

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Think of it this way: when you need hot water fast, the upper unit is on.
When you want a lot of water maintained, the lower unit is on.
The amount of heat stratification in a HWT can be pretty amazing. Only when you heat from the bottom do you get uniform heat. The top element acts somewhat like an "on demand" when you pull a lot of water.
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The elements and thermostats are wired so only ONE element can be on at any one time. When first turned on, the top thermostat powers the top element and disconnects the bottom element. This heats the only top few gallons, so for that few gallons recovery is fast. Then when the top part gets hot, the upper thermostat switches power to the botom thermostat. The bottom thermostat powers the bottom element till the entire tank has hot water. Then the bottom thermostat opens and the power is off to both elements. When you start to use hot water, the cold water comes into the bottom of the tank through the dip tube and the bottom thermostat closes first. Since the top is still hot, the bottom element comes on and you heat the water in the bottom, which will convect up and therefore heat the entire tank. The hottest water stays at the top and the coldest water stays at the bottom. If you use all the hot water in the tank, the top thermostat switches power on to the top element for quick recovery in the top of the tank, then switches power back to the bottom again.
NOTE: Because there is no flue or flue losses, the efficiency is 100%, not 30%. Electricity usually costs more than gas, so a gas water heater that is 75% efficiency is usually cheaper to operate and recovers faster because the burner usually provides more BTUs than an electric element.
Your breaker should be sized at 125% of the continuous load.
That means that you need at least 25 amps. If your voltage is a little high, you may need a 30 amp breaker, because with high voltage, the amps will be higher as well.
Hope this helps.
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