240v 3800 watt electric water heater?

[red31]

Dual 3800-Watt heating elements

Existing heater wired to 2x 20A breakers

Why is it only rated 3800 watts with 2 elements?

[Bobbo]

Actually, UPPER element is primary, LOWER is secondary. That means if both need to run, the UPPER is the one that actually does.

When hot water is pulled out at the top, cold water comes in at the bottom. When the bottom cools down, the lower element comes on to heat it. If you pull enough water out that the cold reaches the upper element, the lower element is cut off and the upper element cuts on. That way, it is only heating the top half of the tank, the half actually supplying hot water to the outlet. When the top half of the tank gets hot (after you turn off the water), the upper element cuts off, and the lower element cuts back on till the whole tank is hot again.

[Chris_Bryant]

DrewE wrote:
Sounds typical. Both elements are 3800 watts, but the thermostats are wired such that only one can be active at a time. I don't remember whether the upper or the lower typically has priority--I believe it's the one closest to the water outlet. This setup allows for more even hot water temperature/better recovery as the tank starts to get depleted (and refilled with cold water) than having a single 3800W element would or than having a pair of 1900W elements would.

A 20A 240V circuit, per the NEC, should only be used for a continuous load of 80% of that, or about 16A. That works out to 3800W. Of course, for a 240V circuit, you need a pair of ganged breakers.

If you have two separate 240V 20A circuits, it should be possible to hook them up to the two elements independently and bypass the sequencing circuitry. I'm not sure whether this would be permissible per electric codes, or rather how one would go about wiring it up in a way that meets all the code requirements. It may be necessary to have a single 40A circuit going to the heater so as to have a single shut-off, and use a sub panel for the two 20A circuits, or something like that. I'm not sure I see much benefit to doing so, though, at least in the majority of cases.

^^^This^^^

[Old-Biscuit]

If you only have two (2) 20A circuit breakers then it is a 120V water heater.


Typically lower t-stat is primary......upper is secondary.

Cold water inlet goes thru dip tube which extends down from top of water heater to bottom where cold water inlet is.......pushing hotter water up and out top.
Cold water inlet at bottom triggers lower t-stat/element and then as water temp drops upper t-stat/element triggers.

240V elements require two(2) HOT leads........dual 240V elements require four (4) circuit breakers

[time2roll]

30 gal is an unusually large water heater for an RV.

[DrewE]

Sounds typical. Both elements are 3800 watts, but the thermostats are wired such that only one can be active at a time. I don't remember whether the upper or the lower typically has priority--I believe it's the one closest to the water outlet. This setup allows for more even hot water temperature/better recovery as the tank starts to get depleted (and refilled with cold water) than having a single 3800W element would or than having a pair of 1900W elements would.

A 20A 240V circuit, per the NEC, should only be used for a continuous load of 80% of that, or about 16A. That works out to 3800W. Of course, for a 240V circuit, you need a pair of ganged breakers.

If you have two separate 240V 20A circuits, it should be possible to hook them up to the two elements independently and bypass the sequencing circuitry. I'm not sure whether this would be permissible per electric codes, or rather how one would go about wiring it up in a way that meets all the code requirements. It may be necessary to have a single 40A circuit going to the heater so as to have a single shut-off, and use a sub panel for the two 20A circuits, or something like that. I'm not sure I see much benefit to doing so, though, at least in the majority of cases.

[red31]

http://www.homedepot.com/p/Rheem-Performance-30-Gal-Tall-6-Year-3800-3800-Watt-Elements-Electric-Wat...

is it not wired

L1---20a---(3800)---(3800)---20a---L2

[time2roll]

So there are four 20 amp breakers? Two for each element?
Otherwise you can't get there from here.

[red31]

smkettner wrote:


Calculated load is 1900 watts per circuit or 15.83 amps.

That is what I don't understand, 3800/240 = 15.82 amps

Why is it not double that? is not each element 3800 watts x 240v ?

[time2roll]

Because 16 amp continuous load requires a 20 amp circuit.

Calculated load is 1900 watts per circuit or 15.83 amps.

[MrWizard]

No info no # no link
Can't say
But what you say doesn't match up
3800w is about 32 amps at 120v or about 16 amps at 240v
Dual 20 amp 240 breaker would indicates this is 3800w max,
dual 1900w elements not two 3800w elements