UFC 3-420-01
25 October 2004
Standard Plumbing Code, Chapter 45 of the ASHRAE Handbook -
Applications 1995 and Chapter 33 of the ASHRAE Handbook -
Fundamentals 1997 provide an ample set of resources on this topic.
Therefore, this appendix will not discuss this process.
(5) Domestic Hot Water Circulation Pump: After the domestic hot water
distribution piping has been sized, the domestic hot water circulation pump
can be sized. This pump is used to circulate the domestic hot water
through the distribution piping system. Size the pump using equation (3)
below:
q
Q
=
(3)
cρ c p ∆T
p
where:
Qp = pump capacity, Lps (gpm)
q = heat loss in the piping system, kW (BTUH)
kW ⋅ sec
min
c = constant, 1
(60
)
kJ
hr
kg
lb
ρ = density of water, 0.9971
(8.33
)
L
gal
kJ
BTU
cp = specific heat of water, 4.18
(1
)
kg ⋅ K
lb ⋅ F
∆T = allowable temperature drop through the system, K (F)
Equation (3) can be simplified to:
q
Q
(4-SI)
=
kW ⋅ sec
p
∆T
4.1679
L⋅K
q
Q
=
(4-IP)
BTUH
p
500
∆T
gpm ⋅ F
E-4
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