Re: [A/S] Reply to What kind of Hot Shot?

["Jim Dunmyer" <jdunmyer@xxxxxxxxxxx>]

Steve,
 Most manufacturers will supply you with a "flow rate vs. temperature rise"
chart, so it's fairly easy to compare one gadget to another.

You're going to need a 70-degree temperature rise (incoming 50 degree water,
heated to 120 for your shower) and at least 2 GPM flow rate.

If you want to get real technical, here's the numbers: 1 BTU of heat is
required to heat 1 pound of water 1 degree Farenheit, a 1000 watt heating
element will give you 3413 BTUs of heat, 1 gallon of water weighs 8.34
pounds.

Do the math and you'll find the reason that conventional water heaters, with
a storage tank, have been in use for so very long and are likely to remain
so. It takes a LOT of heat to supply that temperature rise at any kind of
decent flow rate. Bring in water that's close to freezing, and it's even
worse. You'll also see why household electric water heaters tend to hold 60
gallons or more, while gas-fired units can be only 40 gallons capacity.

                                                                   <<Jim>>