Estimating Commercial Building Hot Water Use

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Permalink Reply by David Meiland on May 12, 2011 at 5:36pm

This is a building that's currently in use and those usage patterns are expected to be unchanged?

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Permalink Reply by Richard Caldwell on May 16, 2011 at 9:04am

See the American Society of Plumbing Engineers design handbooks.

aspe.org

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Permalink Reply by Tom Barrett on May 19, 2011 at 8:16am

Before you suggest to a client to spend real money a really expensive measure that you have to guessimate actual water use or use expert information (ASHRAE or ASPE manuals) you might want to put a flow meter on the hot water side and measure actual use. I was hired to verify the calculations on a $1.5 solar water heating project on a building in Hawai'i before they committed to installing it. The system designers used all the right estimates for office water consumption (with a employee restaurant) to come up with their how water consumption estimate. Except they didn't check one important thing - actual hot water usage. Besides getting paid to go to Hawai'i for a few days I saved the client $1.5 million - there was no actual hot water usage except for the kitchen that used a 100 gallon water heater (and as I found the only one in a 1.2 million square foot building). A check of a few bathrooms uncovered an interesting discovery - no hot water was piped to any of the bathrooms as the ground water temperature was almost 80 degrees (another factor the system designer didn't take into account as they apparently never measured water supply temperatures). My recommendation was to install a much smaller solar water heating system and saved $1.48 million for my client.

 

Design assumptions are fine when doing an initial determination; however, don't rely on WAGs, E-WAGs, or CAS-WAGs always measure. Spending a little up front may save a lot in the end. 

 

 

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