# NWS Heating Element

Registered Users Posts: 26 ✭✭
I have some extra panels and was looking at our host's dc heating element which are significantly expensive than other ones I can find.
I don't mind paying extra if I know why it costs more.
It will be just for pre-heating purpose before going into main water heater.
I would like to stay 24 or 48v setup.
Thanks

Sincerely
Michael

You can get a high wattage element from a hardware store and use it at lower voltages/currents:

http://www.homedepot.com/p/4500-Watt-240-Volt-Low-Watt-Density-Watt-Fold-Back-Screw-In-Stainless-Steel-Alloy-Water-Heater-Element-15011/204834493
• P=I^R=V^2/R=V*I
• R = V^2/P = 240v^2 / 4,500 watts = 12.8 Ohms
• P = V^2/R = 24^2 / 12.8 Ohms = 45 Watts
• P = V^2/R = 48^2 / 12.8 Ohms = 180 Watts
If you can find higher rated power elements, you can figure out the actual heating at lower voltage.

http://www.homedepot.com/s/water%20heater%20elements?NCNI-5

Also, lower rated voltage / wattage (AC input) does not mean lower power at lower DC voltages:

http://www.homedepot.com/p/1500-Watt-120-Volt-High-Watt-Density-Screw-In-Water-Heater-Element-15024/204834407
• P at voltage = element rating at AC power * DC volts ^ 2 / AC volts ^2 = 1,500 Watts * 48v^2 / 120v^2 = 240 Watts
One thing to watch for--The AC thermostats are not rated for full power at DC volts... It is very possible for a non-DC rated thermostat to burn out the contacts or even spot weld them together (short).

-Bill
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
• Registered Users Posts: 26 ✭✭
Thanks Bill. I've done search function and have read other folks trying to do the same.
I was just curious if our host's listing was much different than Hurricane solar guy's items.
I am assuming that SSR is necessary when using "waste-not" auxillary function on my Midnite Classic.

Thanks
Sincerely

Michael
I don't work for NAWS, and I rarely talk with them (just details about the forum).

I would guess that elements are Similar between vendors (and there are good and bad).

Low volume stuff (solar only stuff) is going to be more expensive.

-Bill
Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
• Solar Expert Posts: 1,386 ✭✭✭✭
edited March 2017 #5
Maybe wire the thermostat (or any thermal switch) and the aux output in series and then to the input of a DC SSR.

I am available for custom hardware/firmware development

• Registered Users Posts: 26 ✭✭
Bill, I certainly didn't think you had any affiliation with NWS.
You have been a great moderator for a short time I have been on. Thank you.
Sincerely
Michael