UFC 3-420-01
25 October 2004
Table 606.5.11-2 HYDRO-PNEUMATIC TANK HIGH WATER LEVELS AND
WITHDRAWALS
(Based on bottom outlet tanks and a 10 percent residual)
Pressure Range
High Water Level
Withdrawal
Psi (kPa)
(% of total tank capacity)
(96% of total tank capacity)
20-40 (140-275)
43
33
30-50 (205-345)
38
28
40-60 (275-415)
34
24
50-70 (345-480)
32
22
60-80 (415-550)
28
18
20-45 (140-310)
48
38
30-55 (205-380)
42
32
40-65 (275-450)
37
27
50-75 (345-520)
35
25
60-85 (415-590)
32
22
J.
Add "SECTION 607.1.1 Legionella Pneumophila (Legionnaire's Disease).
The bacteria that causes Legionnaire's disease when inhaled has been discovered in
the service water systems of various buildings in the United States and abroad. It has
been determined that Legionella pneumophila can colonize in hot water systems
maintained at temperatures of 115F (46C) or lower. Service water segments subject
to stagnation (e.g., faucet aerators, shower heads and certain portions of storagetype
water heaters) could provide an ideal location for bacteria to breed. Service water
temperatures in the range of 140F (60C) are recommended in order to limit the growth
potential of the bacteria. However, care must be taken to avoid scalding. Anti-scald
devices shall be incorporated in designs in which the service water temperature is in the
range described above. For hospital and health care facilities, periodic supervised
flushing of fixture heads with water at or above 170F (77C) are recommended.
K.
SECTION 607.2 Hot water supply temperature maintenance. Replace the
existing text with the following: "Criteria determining the need for circulating pumps in
ASHRAE HANDBOOK HVAC Systems and Equipment will be followed. Pump sizing
will be in accordance with the simplified method in ASHRAE unless specific conditions
warrant the need for more detailed calculations. Circulation should be at a rate that
limits the water temperature drop to 20F (11.1C) (maximum temperature difference
between supply and return). A method that has proved satisfactory and is generally
accepted for determining rate of circulation is to allow 1 gallon (3.8 L) per minute for
each 20 fixtures using hot water. Valves for balancing the circulation should be
provided in each return branch."
L.
SECTION 607.2.2 Pump operation. Add after the last sentence: "In
A-20
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