Dual Voltage (12v dc / 120v ac) Small Electric Water Heater

[E350]

GTDad: Could you post pictures of the unit and its label?

[reelchef67]

Hi E350 sorry for delay
This is gtdad , tapatalk issues..
Here is what is installed

[E350]

Interesting, when you have time, let us know how the Emerson EH-1 works and if you know if they are still being sold somewhere.

[boywonder]

Originally Posted by E350

Interesting, when you have time, let us know how the Emerson EH-1 works and if you know if they are still being sold somewhere.

I've just searched pretty hard for this unit and came up with nothing other than a recall notice and a used one that sold at a Goodwill store auction in toledo OH for $12

It appears that these were also marketed as In-sink-erator, ISE, Dayton, Kenmore and a few other brands.

[GTDad]

Yah i found same thing when I googled mine. according to recall my serial number falls outside recall notice.
I have used it fair last summer , it works really well for brewing instant beverages oatmeal etc. Also used it for warm dishwater. I just got my current van last july so not a ton of use yet.

[boywonder]

I just picked up a 2.5 gallon Rheem 110V water heater from Home depot tonight. The plan is to determine if it can be easily converted to 12V power.

Will pull it apart this weekend a take some pics.

stay tuned.....

[E350]

tuned...

[JWA]

Originally Posted by E350

tuned...

X 2

[prally]

X 3

[boywonder]

OK, good news......it appears that these units use std issue heating elements with 1" NPT threads, so a 12V element should screw right in.

These are pretty straightforward, basically a regular sized water heater shrunk down to pint-size. It uses a std TP relief valve and has a plastic drain valve and 1/2" NPT water inlet and outlet threads.

The thermostat looks quite simple as it just opens the circuit when the set temp is reached, so this should work fine on 12VDC.

I'm going to order a 12V heater element (probably tonight) and test this unit with a 12V supply.

DISCLAIMER: Modifying water heaters is potentially very dangerous and may result in severe injury or death to you or your loved ones ......if you don't understand what you are doing please don't try this at home.

My biggest issue is finding a space to put this; looks like I need to modify some cabinetry....

The little pint-sized unit......





Very simple wiring, mains power to thermostat and then heating element (everything series connected)





Setting the temp




....and (finally!) the heating element





12V heater elements are readily available in 300W and 600W

Here are the simplified thermodynamics calculations for how long and how much battery it will take to heat up 2.5 gallons of water:

(this is a simplified adiabatic calculation, which means there is no heat loss from the heater, ie perfect insulation....reality will be worse than this)

assumptions:

water weighs about 8lbs/gallon, so 2.5 gallons of water weighs about 20 lbs

specific heat capacity (Cp) of water is 1 btu/(lb degree F)

let's calculate the energy required to heat 2.5 gallons of water from 70 deg F to 110 deg F (from room temp to luke warm)....so delta T=40 deg F

20 lbs water*(1 btu/(lb degree F)*(40 degrees F)=800 btu

800 btu*(.29 watt-hours/btu)=232 watt-hours

232 watt-hrs/300W=.77 hrs, so about 45 minutes, assuming no heat loss through the jacket/insulation


...and 300W/12V=25 amps

25 amps used for .77 hrs is .25*.77=19.25 amp-hours of battery capacity