On Mar 14, 4:10*pm, Aaron FIsher wrote:
I bought a home a few months ago and didn't even think to look at the hot
water heaters.

A friend suggested today that I set the temperatures differentially; and
when I asked why, I realized I had no idea why or to what advantage two
hot water heaters would be set up in serial connections. (I'd have used
one for the teen's bathroom, and another, in parallel, for the rest of
the house.)

Anyway, what's the THEORY and RATIONALE for having two hot water heaters
in parallel?

Specifically:
- What's the main advantage (is is simply gallonage?)
- What is the main benefit?
- What is the key drawbacks?
And, most importantly:
- Would you set the temperatures differently on them or the same?

There are different options. In series if you set them the same you
will have lots of hot water. Downside is that the 2nd one won't
actually run a lot and you will have the maximum costs to maintain the
water at the set temp. Set the first one a little lower than the
second. This gives you really rapid recovery if you use the entire
first tank. Also evens out the running time and reduces the maintain
temp costs. But this will redcue the amount of hw you can draw in a
single go. Parallel doesn't really work well as you can not even the
draw. Parallel works better if you dedicate each tank to specific
fixtures and appliances. The most common is to have a second tank
dedicated to a master bath that has a large tub or spa. Also insures
that you (the master) have hw when the kids use all theirs up.