Part number 550-100-305/0118
37
AquaBalance
TM
W
ALL
M
OUNT
GAS
-
FIRED
WATER
BOILER
—
Boiler Manual
Figure 45
Maximum and minimum flow rates
through boiler heat exchanger
17
Primary/Secondary System Piping
System water piping methods
Near boiler piping
1. Connect boiler to system only as shown in Fig-
ure 47, page 38. The primary/secondary piping shown
ensures the boiler loop will have sufficient flow.
2. 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 drop required. 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 143,000 Btuh. The desired temperature
drop through the system piping is 20°F. Then the re-
quired flow rate is:
FLOW
=
143,000
—–—–—–—–
20 x 500
=
14 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.
Expansion Tank Location
Figure 47, page 38 show typical installation of the system expansion tank.
It is highly recommended that you locate the air separator and expan-
sion tank as shown in the suggested piping drawings on pages 37 - 39.
Ensure that the expansion tank size will handle boiler and system
water volume and temperature. See tank manufacturer’s instructions
and ratings for details. Additional tanks may be added to the system
if needed to handle the expansion. These tanks may be installed by
connecting to tees in the system piping.
Undersized expansion tanks
cause system water to be
lost from the relief valve and makeup water to be added
through the fill valve. Eventual boiler failure can result
due to excessive make-up water addition. Always locate
the
cold-water fill connection
at the expansion tank.
Never locate this elsewhere.
Diaphragm- or bladder-type tank:
Refer to Figure 47, page 38 for suggested piping when using a dia-
phragm- or bladder-type expansion tank.
Diaphragm- or bladder-type expansion tank—Always
check pressure and charge tank with tank removed from
system to be sure reading is accurate. Boiler relief valve
is set for 30 PSIG.
Operating pressure of system, after
temperature expansion above cold fill pressure, should
not exceed 24 PSIG to avoid weeping of relief valve.
Install an automatic air vent on top of the air separator, per separator
manufacturer’s instructions.
Automatic air vents
(if used — automatic air vents
must be used with diaghragm-type expansion tanks only)
1. See Figure 46.
2. Remove the cap from any automatic air vent in the system and
check operation by depressing valve “B” slightly with the tip of a
screwdriver.
Scald hazard
— Water from air vent may be very hot.
Avoid contact to prevent possible severe personal injury.
3. If the air vent valve appears to be working freely and not leaking,
replace cap “A”, twisting all the way on.
4. Loosen cap “A” one turn to allow vent to operate.
5. Have vent replaced if it does not operate correctly.
Figure 46
Automatic air vent
85036
A
B
Boiler
Model
MAX
Flow Rate
20° F
temperature
rise
GPM
MIN
Flow Rate
50° F
temperature
rise
GPM
Flow Rate
Delta T1
protection
67° F
temperature
rise
GPM
WMB-80
7.9
2.9
2.3
WMB-120
12.0
4.3
3.4
WMB-155
15.2
6.1
4.5