Weil-McLain Ultra Manual page 20

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gas fired water boiler
Install water piping
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
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. Adding the recommended high limit control (
can help ensure supply water temperature will not exceed the
maximum allowable for the radiant system. Wire this limit control
in either the manual reset or automatic reset external limit circuit
of the U-Control.
4. When using a closed-type expansion tank, connect the expansion
tank and make-up water piping as shown in Figure 14, page 16.
5. Connect DHW (domestic hot water) piping to indirect storage
water heater as shown.
By default, the U-Control Module turns off space heating
during DHW heating (if DHW input is priority 1). The
boiler circulator will turn off, preventing hot water from
circulating to the system (optional timeout setting can
be used to override). The flow/check valve shown on the
boiler outlet piping prevents gravity circulation in the
boiler loop during DHW heating.
6. Controlling the circulators
a. The U-Control can control up to three circulators (boiler cir-
culator and two others). Refer to Field wiring, beginning on
page 54, for instructions on wiring to circulators.
b. The factory default settings are: DHW circulator as Circula-
tor 1, boiler circulator as Circulator 2. See Field wiring instruc-
tions, beginning on page 54, for details.
1 Ultra boiler
2 Indirect water heater (DHW), if used (see page 22)
3 Boiler relief valve (see page 14 for piping details)
4 Relief valve discharge piping (see page 14 for details)
5 DHW circulator (see page 22 for suggested sizing)
6 Isolation valves
7 System circulator (see information above for wiring)
8 Diaphragm (or bladder) type expansion tank (see page 22 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
11 Purge/drain valves
12 Boiler circulator
13 Zone valves, when used (zoning may also be done using manifold-
mounted valve actuators)
20
— Boiler Manual
(continued)
Figure 18 for typical radiant
Figure 18, item 22)
Legend — Figure 18
20 Make-up water supply
21 Primary/secondary connection (tees no more than 12 inches apart)
22 Optional high limit temperature control, set to protect radiant tubing
24 Strap system supply and return sensors to lines as shown, at least 6 pipe
25 Systems using high-head pumps may require a bypass pressure regulator
NOTE 1:
primary/secondary connection, item 21). Use only primary/secondary piping
as shown. Failure to follow these guidelines could result in system problems.
Figure 18
Typical radiant heating system piping plus
optional DHW
diameters (but no more than 3 feet) from boiler connection tees.
to prevent damage to control valves.
Items supplied with boiler
Items supplied by others
Use at least the following pipe sizes on all boiler
loop piping (connecting boiler to and from the
• Ultra-80 or Ultra-105 – 1" or larger.
• Ultra-155 or -230 – 1¼" or larger.
• Ultra-310 – 1½" or larger.
Part number 550-100-066/0608