On Thu, 30 Oct 2008 01:21:30 -0700, Bruce L. Bergman
wrote:

On Thu, 30 Oct 2008 00:43:14 -0400, wrote:

I picked up a 4500 watt 208 water heater element today cheap. I need
to make a steem generator for wood bending and was thinking of using
this element in a tank.
My calcs say it would draw 21.6 amps at 208 volts, for an effective
resistance of 9.63 ohms.
At 115 volts it should draw 12 amps and produce 1380 watts? and at 230
volts it should draw 23.8 amps and produce 5500 watts?
It takes about 3700 watts to boil 1KG of water in 10 minutes so it
should take 26 minutes to boil off 1kg of water at 1380 watts, and 1
kg of water is one liter and will produce 1700 liters if steam at
atmospheric pressure and 100C.

This should be adequate I think - steam bending 3/8" thick X 14" elm
in a 2 foot by 5 foot plastic "barrel".

Did I calculate this correctly guys?

Sounds about right - but you probably need to feed it 240V to get
enough steam to work a bender box.

Make DARNED sure it doesn't run dry, I'd have a float safety to make
sure the water level doesn't drop too far. And a float valve fill of
some sort, you want to dump the cold water right in front of the
heater inlet.

I would suggest putting the element in a 1-1/2" pipe stub (to allow
clearance around the element) with a 1' x 1-1/2" x 1-1/2" tee on the
feed end (the 1" for the element mount threads), then run a pump to
force rapid water circulation around the element - they are designed
to be under pressure in a water heater and not have active steam
boiling off the element.

It's going to have a shorter life from the cavitation bubbles, but
if you keep the water moving swiftly as it goes over the heater
element it should minimize this. One of the "Rough Service" or "Low
Watt Density" (double-folded) elements will help too. And get a
blade-style flow switch to keep the element off till the water is
moving.

Let the hot water get carried along by the velocity out into the
main tank and /then/ go "Oh, I'm supposed to boil now..."

-- Bruce --
Element is 60 inches long, double folded.