Health Care DHW Usage

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I think 20-25 gallons/day per bed seems generous for a new cardiac facility (supposedly incorporating E-Star fixtures) without a laundry and with a kitchen. But the plumbing designer is sure this is low.

Does anyone have a clear simple reference for average long term domestic hot water consumption (preferably measured/metered) in hospitals?
ASHRAE Applications lists 18 gpd/bed for "nursing homes," including their kitchens, but without "heavy laundry" and with the caveat that "data predate modern low-flow fixtures."
A Massachusetts study of total domestic (so both hot and cold) water consumption in hospitals in the early 90's found 40 - 340 gpd/bed, which could even include lawn care.
The 90.1-2004 Users Manual (pg G-32) includes some inputs for long-term DHW energy use for "Health/Institutional" (1100 Btuh/occupant x hourly schedule fractions) that imply about 15 gallons/day per "occupant" if that energy is for actually heating the water and does not include pipe losses. But the default occupancy density listed there is about 5x the bed density in this proposed hospital, so using it would lead to 65 gpd/bed.
The Green Guide for Health Care has about 60 separate occupancy categories with varying DHW rates, occupant densities and schedules; all the DHW rates are also in Btuh/person and vary from 0-1000 Btuh/person, typically 600 Btuh. These are supposedly taken from "90.1-2001 ECB Supplement Tables 7.1A & 7.1B" which are not in the body of 90.1-2001.
And I'm trying to separate energy use due to consumption and energy use due to pipe heat losses. I think I searched Transactions recently and did not find anything new regarding healthcare DHW. At this point I don't care about peak hours, or instant demand, just long term average.

Thanks if you can help;

Fred Porter

Fred Porter's picture
Joined: 2011-09-30
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The data that you're seeking would be very useful, but I'm afraid that you
are unlikely to find them. ASHRAE Technical Committee 6.6 - Service Water
Systems is has been trying for several years to get ASHRAE approval to
sponsor a research project to gather these sorts of data. The draft work
statement's current title is "Establishing Benchmark Levels of Commercial
and Institutional Hot Water Use by End Use".

Accurate and current end-use data are required for accurate energy
simulation and for comparison of systems. For example, comparing energy
consumption of tankless versus tank-type water heaters depends largely on
the draw patterns for a given total quantity of heated water. Also, the
pipe losses that you mention are highly dependent upon draw pattern.

Since the members of TC 6.6 are unaware of current data for domestic hot
water consumption in commercial and institutional buildings, it seems likely
that these data won't exist until we can get that research project accepted
and completed.


David P. Yuill

David Yuill's picture
Joined: 2011-10-02
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