water heaters

[Chad Fabry]

I'm inspecting a house w/ a large whirlpool bath tomorrow and my client has informed me that there are two water heaters hooked together to accomodate the volume necessary to fill the tub.

What's the correct method .. should the heaters be in parellel or in series? Since they're hooked together, is one tprv adequate or must there be two? Any other hints?

[Jim Katen]

Originally posted by Chad Fabry

I'm inspecting a house w/ a large whirlpool bath tomorrow and my client has informed me that there are two water heaters hooked together to accomodate the volume necessary to fill the tub.

What's the correct method .. should the heaters be in parellel or in series? Since they're hooked together, is one tprv adequate or must there be two? Any other hints?

Either series or parallel is fine.

If parallel, the piping from the manifold to each tank should be very similar in length & number of elbows in order to ensure equal flow from both tanks. Otherwise, the difference in friction will cause one tank to be favored over the other and you'll get less hot water than a perfectly balanced set up would yield.

If in series, the first tank will do most of the work and will wear out faster.

There should be a TPR valve on each tank.

- Jim Katen, Oregon

[Les]

Jim is right. However, I tend to favor series and a bypass arrangement so one can be serviced/changed/shut down etc. Also, in series have one temper the water and one finish the water; #1 set at "low" and #2 at desired temp of delivery. Saves money and will extend the life of both. Around here water enters at 58deg, so the tempering is normally done to abt 80deg. This is for natural gas heaters.

[kurt]

I've heard adament arguments in both directions. I see them both ways, & am still not convinced that the "1st" heater wears out quicker. In fact, in my own most recent water heater failure, the "2nd" heater in my series installation failed prematurely before the "1st" heater. Go figure.....

[Jim Morrison]

My vote is for parallel. The true test, though, is: Will the arrangement fill the tub with hot water?

[Terence McCann]

Chad:

Go here -> http://www.hotwater.com/frame.html?topa ... sthelp.com

Type in Parallel vs. Series Piping in the search box for a PDF file.

This is A.O. Smiths stance on the issue.

[Chad Fabry]

Thanks very much for the help, guys.