Domestic hot water

Big Ed

In series hook up is for hotter water , like you may need in a commerical applaction. Parallel is for volume, like you need in a home...

Paul Mitchell_2

Domestic hot water

Hello all
I am pricing a gas conversion. They now have a 50 gallon Bock hot water heater. Per the specs it has a recovery of 166 Gph. I was thinking of twining two 50 gallon gas units. Question is would it be better in series or parallel. Home hsa three and 1/2 baths. I think parallel because of peak demand in the am.
Any opinions...Thanks

Paul Mitchell_2

Thanks big ed

Mark Eatherton1

This question was asked of me once...

from a fellow instructor at RRCC. Kelly Wiebold for those that know him. He said there is no empirical data shwoing that self contained tank type water heaters are better in parallel than they are in series. And he had a valid argument. The appliances, if set for 1/2 the total anticipated "rise" will use the same amount of energy and produce the same hourly gallons of a given degree F rise.

I couldn't argue with him. The only draw backs I could see would be increased pressure drop on the DHW system, probably negligible in most cases. But my gut tells me that the appliances are more thermally efficient if they both see the coolest entering water temperature. NO?

So I generally recommend they be done in parallel. Besides, if one ever decides to crap the bed, which they are FAMOUS for, you can maintain decent hot water while changing the other one out.

We were going to make our students do 2 similar but different 3 tank water heater systems, and meter them and see what happened. Still might:-)

If you have a circ return, the first tank will have a substantially shorter life expectancy...unless you paralleled back though all three, in which case they all fail at the same time!:-)

ME

Larry Weingarten

I might add...

... that if you can find heaters with 1" ports, flow restriction won't be a problem plumbed in series. I like series as parallel cannot be plumbed for certain to have balanced flow into each tank. Even if flow were perfect at installation things change with rust buildup at dielectrics and tank connections. Install each tank in series with a three valve bypass so your client can get by on one heater when the other needs work. Another thought is that you'll get more hot water from tanks plumbed in series. It is a rule of thumb that you get about 75% of the volume of a heater as undiluted hot. So, from two fifty gallon heaters you would get 75 gallons if plumbed in parallel. Now, plumbed in series it seems you would get 75% of the first tank but 100% of the second as you follow the flow. That's 87.5 gallons of undiluted hot. If this thinking is flawed... well heck! ;~)

Yours, Larry

ps. this post actually follows Mark's!

Dave Yates (PAH)

agreed

Besides which, the series installation always stresses the first tank the most. Series can be set up for the inevitable replacement (see attached drawings) while maintaining use from the second tank.

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Big Ed

input

Don't for get the full input of the burners at the same time rather then staggered input of the series hook up. Faster recovery......