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?

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?

Yep.

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.

Close. 1 BTU is about a kilowatt-second. Heating water from 77 deg F to 212
deg F is a difference of 135 deg F, times 2.2 lbs is 297 BTUs. Boiling to
steam is 965 BTUs/lb or 2123 BTUs for 2.2 lbs. So 2420 BTUs total or 2550
kilowatt-seconds. So with 1.380 kilowatts of heat you need 1850 seconds or
about 31 minutes to make a kilo of schteam from room-temp water.

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 --

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.

none of the comments so far address what seems to be a critical error
in your calculation. Heat losses. You are going to loose heat to
ambient, and it will get worse as the temp increases. Also don't let
the element get above the water level. Getting your steam box to
drain back into your pot would also be a good idea.


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?

jk

On Thu, 30 Oct 2008 20:09:28 -0400, wrote:
On Thu, 30 Oct 2008 01:21:30 -0700, Bruce L. Bergman wrote:

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..."

Element is 60 inches long, double folded.

The double-folded is /usually/ the low watt density style, but you
need to cross the part number in the book to know for certain. And
read the footnotes, make sure that the sheath material is compatible
with any additives you will put in the water.

And if it isn't the 1" pipe thread screw in style, get another
heater element - you'll play hell duplicating that four bolt flange.
And the elements are easier to get.

They sell adapters for going the other way - a four bolt flange
with the 1" threaded bung in the center.

-- Bruce --

On Oct 31, 2:17*am, Bruce L. Bergman
wrote:
...
* And if it isn't the 1" pipe thread screw in style, get another
heater element - you'll play hell duplicating that four bolt flange.
And the elements are easier to get.

* *They sell adapters for going the other way - a four bolt flange
with the 1" threaded bung in the center.

* -- Bruce --

I found out the hard way that heater element threads are straight o-
ring (STOR) rather than tapered pipe (NPT). They may not even be
exactly STOR because they use a squared ring. At least the straight
thread was easier to cut on a lathe.

On Oct 30, 12:43*am, wrote:
...
This should *be adequate I think - steam bending 3/8" thick X 14" elm
in a 2 foot by 5 foot plastic "barrel".

I helped a cabinet-maker friend who lives off-grid build his steamer
out of 2" galvanized pipe, with steam from a pressure cooker on a
propane barbecue burner, which made plenty of steam once we had
insulated every bit of the plumbing thoroughly.

The trickiest part was knowing when the wood was ready and removing it
quickly. We slanted the pipe so condensate drained out the bottom
until the pipe was up to temperature, then we could see it become
steam and start timing. He had oven gloves to unscrew the HOT end
fitting and pull out the wood. Any pressure would have scalded him,
condensate would have soaked through the glove.

On Fri, 31 Oct 2008 04:28:47 -0700 (PDT), Jim Wilkins
wrote:

On Oct 31, 2:17*am, Bruce L. Bergman
wrote:
...
* And if it isn't the 1" pipe thread screw in style, get another
heater element - you'll play hell duplicating that four bolt flange.
And the elements are easier to get.

* *They sell adapters for going the other way - a four bolt flange
with the 1" threaded bung in the center.

* -- Bruce --

I found out the hard way that heater element threads are straight o-
ring (STOR) rather than tapered pipe (NPT). They may not even be
exactly STOR because they use a squared ring. At least the straight
thread was easier to cut on a lathe.

Yes, but I didn't mention that because it isn't critical to the use.
If you are going to build a production machine around it, then you
machine the straight threads with the gasket pocket.

For a low-pressure one-off like this it should work fine into NPT.

-- Bruce --

On Thu, 30 Oct 2008 21:24:02 -0700, jk wrote:


none of the comments so far address what seems to be a critical error
in your calculation. Heat losses. You are going to loose heat to
ambient, and it will get worse as the temp increases. Also don't let
the element get above the water level. Getting your steam box to
drain back into your pot would also be a good idea.



Fully aware of both points. The energy requirements were only for the
boiling off - not the pre-heating and basically I was looking mostly
at the power requirements of the element at various voltages - and my
numbers were a few percent on the conservative side.
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?

jk

On Thu, 30 Oct 2008 23:17:49 -0700, Bruce L. Bergman
wrote:

On Thu, 30 Oct 2008 20:09:28 -0400, wrote:
On Thu, 30 Oct 2008 01:21:30 -0700, Bruce L. Bergman wrote:

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..."

Element is 60 inches long, double folded.

The double-folded is /usually/ the low watt density style, but you
need to cross the part number in the book to know for certain. And
read the footnotes, make sure that the sheath material is compatible
with any additives you will put in the water.

And if it isn't the 1" pipe thread screw in style, get another
heater element - you'll play hell duplicating that four bolt flange.
And the elements are easier to get.

They sell adapters for going the other way - a four bolt flange
with the 1" threaded bung in the center.

-- Bruce --
4 bolt flange mounting (I can easily make the flange) and there will
be no additives in the water. Elements are copper or copper coated
(Chromalox 20200 860 d80) Cost me $5 brand new - and there are 3 more
in stock at the same price that I will buy if it works out (for spares
down the road).

Watch any additives in the water, anything alkaline will eat through the
elements. We got 3 weeks before failure on a wash tank.
-- Bruce --
4 bolt flange mounting (I can easily make the flange) and there will
be no additives in the water. Elements are copper or copper coated
(Chromalox 20200 860 d80) Cost me $5 brand new - and there are 3 more
in stock at the same price that I will buy if it works out (for spares
down the road).