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Panel Radiator
Design Manual
Panel Radiator Design Manual | 12.2009
Technical specifications are subject to change without prior notice
7.
Piping Arrangements
The design of a panel radiator based heating system
involves selection of a piping system, pipe sizes, overall
design temperature drop, required flow rates and desired
type of system control. For trouble-free system operation,
do not exceed the flow rates in Table 10.
Maximum flow rates & heat carrying capacities Table 10
Pipe size*
Max
flow
(gpm)
Q
(∆T=20ºF)
Q
(∆T=30ºF)
Q
(∆T=40ºF)
½" copper
or PEX
1.5
15,000
22,500
30,000
⅝" PEX
2.0
20,000
30,000
40,000
¾" copper
4.0
40,000
60,000
80,000
1" copper
8.0
80,000
120,000
160,000
1¼" copper
14.0
140,000
210,000
280,000
Diverter
valve
2.0
20,000
30,000
40,000
Radiator
Flow
2.5
25,000
37,500
50,000
Note:
Q (∆T = 20°F (11°C)) denotes the maximum heat
load carrying capacity based on a 20°F (11°C)
temperature drop.
*Pipe size used for main supply/return piping in multiple
one-pipe diverter valve based systems or for one-pipe
systems using monoflow tees. This information is useful
for pipe sizing in two-pipe distribution systems.
This chapter discusses several piping arrangements,
guidelines for system design, pipe size, pump selection
and fine-tuning of individual components. Heat loss (Q),
water flow rate (GPM) and temperature drop (∆T) through
a hydronic heating system are related to each other as:
Q = 500 x GPM x ∆T
This equation is used extensively for accurate sizing of
radiators.
One-Pipe System Options
Figure 11 presents three different one-pipe
arrangements. In any one-pipe system, a single pipe
connects all radiators together. Fewer materials are
needed in a one-pipe system where a perimeter loop
supplies water to all radiators. Since water may flow
through all radiators and cools off along the way, it is
necessary to oversize the last radiator(s) in the loop. A
sizing procedure is outlined.
Table 10 shows maximum Btu load on a one-pipe system
based on pipe size and overall temperature drop.
Series loop system
All water flows through all radiators.
A thermostatic head cannot be used on any radiator as it
will shut off all flow. A central thermostat is required for
temperature control. Do not exceed heat loads as listed
in Table 10.
Option 1: one-pipe system with monoflow tees
(Fig 11).
Monoflow tees are used to divert some water from the
main loop into each radiator. Use one monoflow tee on
the return if the radiator(s) are located above the main
loop; use two monoflow tees if the radiators are installed
below the main loop. Place the tees in the main loop to
each radiator at least 12” apart. Thermostatic heads on
each radiator provide very easy means for individual
temperature control. The system can be operated off a
central thermostat or with constant circulation using an
outdoor reset system. Size the main loop based on the
selected temperature drop (20°F, 30°F, or 40°F (11°C,
17°C, 22°C)) and heat load. Make sure to oversize the
last radiators properly, especially when using an overall
temperature drop of 30°F (17°C) or 40°F (22°C). It is
important to size the main supply and return pipes for the
total heat load and volume to avoid flow restriction or
noise.
Option 2: one-pipe system with diverter valves
(Fig 12).
This arrangement is similar to using monoflow tees
except that now each radiator is equipped with a diverter
valve. Secondly, the total loop flow can NOT exceed 2
GPM because of possible noise at greater flow rates. The
bypass adjustment in the diverter valve can be used to
throttle down the flow through the first radiators and
increase flow through the last radiators in the loop to
make up for the drop in loop temperature. Thermostatic
heads on each radiator provide an easy means for
individual temperature control. The system
can operate off a central thermostat or with constant
circulation using an outdoor reset system. Follow Table
10 for pipe sizing. It is important to size the main supply
and return pipes for the total heat load and volume to
avoid flow restriction or noise.
