Onix Tubing Installation Manual
Watts Radiant: Onix Installation Manual page 65
reading the flow rate on the right side
of the chart.
In the above example, the flow rate for
each circuit is approximately 0.43 gpm
at a
∆T of 20¡F. The total flow rate to
deliver 16,000 BTU/h is 4 (circuits)
×
0.43 = 1.72 gpm.
Note that if the flow rates are to be
manually calculated, the required sup-
ply temperature can make a significant
difference in the resulting calculations.
All three of the following charts are
for fluids at a temperature of 120¡F.
Systems with anti-freeze solutions will
experience a greater change in fluid
properties as temperature conditions
change. Do not use the following
charts if the required fluid temperature
is expected to change by more than
20¡F.
Because of the lower heat carrying
capability of glycol, a good rule of
thumb is to add an extra 10% to the
flow rate.
WARNING: NEVER USE AUTOMO-
TIVE ANTIFREEZE IN ANY
HYDRONIC SYSTEM
.
0.0001
0.001 0.01 0.10.03 1.0
3/8" Tubing
1/2" Tubing
5/8" Tubing
3/4" Tubing
40,000
30,000
20,000
10,000
9,000
8,000
7,000
6,000
5,000
4,000
3,000
2,000
1,000
900
800
700
600
500
5
4
3
2
1
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.09
0.08
0.07
0.06
0.05
PRESSURE DROP (Feet of Head Pressure Drop per Lineal Foot of Tubing)
1 ft/sec
2 ft/sec
3 ft/sec
7 ft/sec
1.5 ft/sec
5 ft/sec
Watts Radiant PRESSURE DROP CHART FOR Onix
Pure Water
TM
TM
1.25 ft/sec
4 ft/sec
6 ft/sec
FLOW RATE (GPM) AT 20 F T
Q
s
HEAT REQUIRED (BTU/h) FOR AREA SERVED BY ONE CIRCUIT
10
9
8
7
6
50,000
60,000
70,000
80,000
90,000
100,000
1" Tubing
Notes: 1. The heat required is the energy the boiler must deliver for the calculated heat output of a circuit. If only the net heat output of
the circuit is known, multiply by 1.1 to get Q
s
, assuming the back and edges are insulated or space below is heated.
2. If the
∆T is different from 20°F, the value of Q
s
must be multiplied by 20/∆T.
3. Numbers from 1–7 in graph show the average water velocity in the hose (ft./sec).
4. This chart is for pure water only. It cannot be used for other liquid mixes.
Typical pressure drop chart for water systems.
Appendix