Water heater ratings

16 year old 50 gal a o smith ECjf electric water heater first hour rating is 53 gallons.
new rheem 47 gallon is rated at 55 gal first hour,
both 4500 watt elements

how is that possible?
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and who makes whirlpool heaters? Ao smith? rheem? someone else?

Scroll down about 5 or 6 posts. You will find your answer.

Thanks but

it helped on who made what
but
not in explaining how the smaller heater has better first hour capacity????
IS someone fibbing??

rating

The insulation requirement has been upgraded a couple of times since you got the A O Smith, so that would be a factor, and what difference does it make anyway?

There have to be some baseline assumptions made in calcultating first hour delivery.
1) It will be spec'd at delivering a certain miminum temp water...maybe 105º maybe 110º
2) You have to spec temp for the incoming water, since first hour is the sum of the tank capacity at the 70% rule ( another whole discussion) + recovery, based on BTU, or KWH, efficiency, and incoming temp.


You could pretty much make "first hour delivery" any number you want it to be! If the biggesg issue you have to worry about is a 2 gallon difference in this figure, just pay the money, and have a Jack Daniels !

Its a heigth issue

Not money-
my heater is under the house and I have a 16 year old 50 gal a o smith heater that just fit thru the entry door in the cement and then just stood upright by 1 or 2 inches under the floor joists in the crawl space, right under the bathrooms.
the replacement a o smith model now made is 2 inches higher. the competing models of short heaters (Rheem GE home depot has 3 gallons less capacity, the lowes whirlpool "american water heater company" I think) model has 3 1/2 gallons less capacity.
So thats the reason for my questions. my garage is a good distance away and would mean more pipes , electric wires and less garage space and more waiting for hot water if I move the heater to put in a tall one.
I do not like "under the house" but it has worked trouble free for 16 years. Previous heater lasted about the same based on home build date of 1984, heater replacement in 92