Part number 550-142-190/1218
50
Primary/Secondary System piping
(continued)
System circulators and zone circulators
1. Install a system circulator or zone circulators as shown in the
piping diagrams in the Primary/Secondary System Piping
section in this manual. These circulators must be supplied
by the installer.
System or zone circulators flow rates
1. Size circulators based on the flow rate required to achieve
the temperature change you needed. You can closely estimate
temperature rise (or drop) through a circuit by using the
following formula, where TD is temperature rise (or drop),
FLOW is flow rate (in gpm), and BTUH is the heat load for
the circuit:
FLOW
=
BTUH
—–—–—–—–
TD x 500
Examples
:
1. Consider a system loop for a system with total heating load
equal to 210,000 Btuh. The desired temperature drop through
the system piping is 20°F. Then the required flow rate is:
FLOW
=
210,000
—–—–—–—–
20 x 500
=
21 gpm
SIMPLIFIED:
For 20° temperature drop, FLOW = MBH / 10.
System or zone circulator head requirement
1. The circulator must be capable of delivering the required flow
against the head loss that will occur in the piping.
2. Determine the pipe size needed and the resultant head loss
using accepted engineering methods.
Install relief valve
1. Install relief valve in 1 " x 1 " x ¾" (for 70/110) or 1 ¼" x 1 ¼"
x ¾" (for 155) reducing tee piped from boiler supply piping
tee (Figure 8, page 14).
2. Pipe the relief valve only as shown, in the location shown.
3. Connect discharge piping to safe disposal location, following
guidelines in the
WARNING
below.
To avoid water damage or scalding due
to relief valve operation, as per local or
state codes
:
Install relief valve ONLY with the spindle
vertical, as shown in illustrations in this
manual.
Discharge line must be connected to relief
valve outlet and run to a safe place of disposal.
Terminate the discharge line in a manner that
will prevent possibility of severe burns or
property damage should the valve discharge.
Locate away from the top of the boiler.
Discharge line must be as short as possible
and be the same size as the valve discharge
connection throughout its entire length.
Discharge line must pitch downward from
the valve and terminate at least 6" above the
floor drain where any discharge will be clearly
visible.
The discharge line shall terminate plain, not
threaded, with a material serviceable for
temperatures of 375°F or greater.
Do not pipe the discharge to any place where
freezing could occur.
No shutoff valve shall be installed between the
relief valve and boiler, or in the discharge line.
Do not plug or place any obstruction in the
discharge line.
Test the operation of the valve after filling and
pressurizing system by lifting the lever. Make
sure the valve discharges freely. If the valve fails to
operate correctly, replace it with a new relief valve.
Failure to comply with the above guidelines
could result in failure of the relief valve to
operate, resulting in possibility of severe
personal injury, death or substantial property
damage.
®
S
ERIES
2
G
AS
-
FIRED
WATER
BOILER
—
Boiler Manual
