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GAS-FIRED WATER BOILER SERIES 2 — Boiler Manual
Part number 550-100-026/0404
17
Figure 9 Typical radiant heating system
piping plus optional DHW
Radiant heating applications
1. The Ultra boiler is ideal for use in radiant heating. The Ultra boiler’s
unique heat exchanger design allows it to work well even in condensing
mode. So there is no need to regulate boiler return water temperature in
radiant heating applications.
2. Connect boiler to system as shown in Figure 9 for typical radiant heating
applications. The primary/secondary piping shown ensures the boiler
loop will have sufficient flow. Size the system piping and circulator to
provide the flow and pressure drop needed for the radiant system.
3. Add the high limit control (Figure 9, item 22) to ensure supply water
temperature will not exceed the maximum allowable for the radiant
system. Wire this limit control between low voltage terminal strip terminals
6 and 7.
4. When using a closed-type expansion tank, connect the expansion tank
and make-up water piping as shown in Figure 4, page 13.
5. Connect DHW (domestic hot water) piping to indirect storage water
heater as shown.
The PhD Control Module turns off space heating during
DHW heating. The boiler circulator will turn off, preventing
hot water from circulating to the system. The flow/check valve
shown on the boiler outlet piping prevents gravity circulation
in the boiler loop during DHW heating.
6. Controlling the system circulator
a. To cycle the system circulator from the Ultra PhD control module, add a
circulator relay wired to the boiler circulator terminals as shown in the Ultra
Control Supplement
7. Setting boiler outlet water target temperature.
a. Follow procedure in Ultra Control Supplement to set space heating target
temperature to the desired supply temperature for the system. For outdoor
reset operation, install and connect the outdoor temperature sensor supplied
with the boiler.
Legend Figure 9
Install water piping
(continued)
3
1 Ultra boiler
2 Indirect water heater (DHW), if used
3 Boiler relief valve (see page 12 for piping details)
4 Relief valve discharge piping (see page 12 for details)
5 DHW circulator (see page 14 for suggested sizing)
6 Isolation valves
7 System circulator
8 Diaphragm (or bladder) type expansion tank (see page 12 for piping of closed-
type expansion tank, if used)
9 Air separator [with automatic air vent only on systems using diaphragm (or
bladder) type expansion tank]
10 Flow/check valves (with weighted seats to prevent gravity
circulation)
11 Purge/drain valves
12 Boiler circulator
13 Zone valves, when used (zoning may also be done using
manifold-mounted valve actuators)
20 Make-up water supply
21 Primary/secondary connection
22 High limit temperature control, set to protect radiant tubing
NOTE 1: To ensure adequate flow rate through the boiler, use the following
pipe size on all boiler loop piping (connecting boiler to and from
the primary/secondary connection, item 21):
Ultra-80 or Ultra-105 – 1" or larger.
Ultra-155 or -230 – 1¼" or larger.
Ultra-310 – 1½" or larger.
Use at least the minimum piping size at left
and pipe the boiler using only primary/
secondary piping as shown. Failure to
follow these guidelines could result in
system problems.