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Sizing Hot water heaters?
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I posted this in the other thread http://www.statewaterheatersizing.com/
Did it not provide a number you could use?0 
Not much help
0 
I have 12 bathrooms w/showers & lav sinks, 9 kitchen sinks, 10 laundry0

My thought is 2 120gal. tanks but I WOULD LIKE SOME TYPE OF FORMULA TO FIGURE THIS.0

In order to properly size a system, you need to know (or assume) flow rates for the showerheads, sinks, etc. and then apply diversity factors based on the number of units and use patterns. http://www.statewaterheatersizing.com/ApplicationData/Apartment.aspx takes all of these into account so you know how much burner and how much storage you will need based on ASHRAE accepted numbers.0

Thanks SWEI0

If you really want to cover your butt, get the client engaged in the process and have them sign off on the assumptions. If they do, you'll probably be selling them 12 new showerheads and a bunch of sink aerators.0

I should mention that getting the assumptions right is truly critical. We sized a system for a hotel a couple years back and I used the standard hotel math. All went well for 21/2 years. Then the hotel had a 100% occupancy conference event during February. Groundwater temps were at or near their annual low, and everyone staying there has to be at the same 8:30 AM meeting. Boom. No hot water. Went back to the ASHRAE Fundamentals as we tried to figure out what happened, and found that while the peak period assumption for a standard hotel is two hours, a convention hotel is assumed to be one hour. Makes perfect sense in retrospect.1
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