How to plumb Two Water Heaters


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Old 03-27-07, 01:27 PM
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Question How to plumb Two Water Heaters

Have two water heaters, side by side, Can I plumb one water heater into the other, going from first heater's hot output to the second heater's cold input?
 
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Old 03-27-07, 02:27 PM
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Yes you can do that.
 
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Old 03-27-07, 07:06 PM
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Why not pipe them parallel reverse and also be sure to pipe it so that if either tanks leaks you can isolate it?
 
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Old 03-27-07, 08:31 PM
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You're not guarenteed to get a even flow doing the parallel reverse. However, like Who said, you should pipe it so if one heater dies, you can turn it off and run the other one solo.
 
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Old 03-28-07, 07:29 AM
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Unhappy Double Heaters

What is meant by parallel reverse?
 
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Old 03-28-07, 12:40 PM
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http://www.bradfordwhite.com/images/shared/pdfs/manuals/SSIWH.pdf

Check out the bottom of page 16 (says page 14 on the bottom of the page) of the above pdf.

As Adam says you are not guaranteed equal flow between the two doing it this way, but it does make the isolation piping easier.

If you understand electrical circuitry the terminology is more or less the same. With series, the water flows into tank 1 and then into tank 2. With parallel, (ideally) half the water goes into tank 1 and the other half goes into tank 2.

PR piping is typically preferred because wear and tear and also deposits of sediments are a bit more balanced between the 2 heaters. Also, you can get more GPMs using this method because it's a more restrictive path for the water having to pass through both water heaters.

The advantages to series is that it is simpler to pipe (but harder to pipe bypasses) and that the piping uses far less materials - copper isn't cheap! In addition, if you know that you'll have a low load situation for any period of time you can switch off the first tank an it will serve as a tempering tank for the second tank.

Aren't choices great... ;-)
 
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Old 03-29-07, 11:08 AM
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I guess that I am an idiot because I still don't understand the "reverse" part of the "parallel-reverse" connection of two electric water heaters.

The drawing that Who references shows two regular electric water heaters, each has the cold supply piped to its inlet and each has the hot outlet piped to the hot supply. This places each heater in parallel with the other. With individual valves on the inlet and outlet of each heater either heater (or both together) can supply hot water. In case of failure of one of the heaters it can be "valved off" from the system and the other heater used with minimal fussing about.

Where/what is the reverse?
 
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Old 03-29-07, 11:26 AM
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Furd, the terminology stems more from piping rads than water heater, but anyway...

The reverse part is the order of inlet outlets. Tank1 is inlet 1 and outlet 2...

If there are 4 tanks it would be:

tank/inlet/outlet

T1 I1 O4
T2 I2 O3
T3 I3 O2
T4 I4 O1

To keep the paths and flows balanced...
 
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Old 03-30-07, 06:58 AM
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Thank you, Who. If the two tanks are located immediately next to each other I can't see that the intervening length of the inlet/outlet piping would make a significant difference unless that piping was undersized to begin with.
 
 

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