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6
Water Piping and Trim
Table 6-2: Flow Switch Paddle Application
Boiler
APX425C
APX525C
APX625C
APX725C
APX825C
B. Piping System To Be Employed
Apex boilers are designed to operate in a closed
loop pressurized system. Minimum pressure in
the boiler must be 14.5 psi (100 kPa). Proper
operation of the Apex boiler requires that the
water flow through the boiler remain within the
limits shown in Table 6-3 any time the boiler is
firing.
NOTICE: Failure to maintain the flow through
boiler within specified limits could result in erratic
operation or premature boiler failure.
1. Near boiler piping must isolate Apex boiler
from system piping via closely spaced tees to
ensure specified flow range through boiler any
time the boiler is firing.
a. The flow rate through the isolated near-
boiler loop is maintained by installer
supplied boiler circulator. See Tables 6-4
and 6-5 for recommended circulators.
b. The flow rate through the isolated near-
boiler loop is completely independent of
the flow rate through the heating system
loop(s).
c. The flow rate through the heating system
loop(s) is controlled by installer sized/
provided system loop circulator(s).
d. This piping arrangement can be used either
for space heating-only applications or
space heating with indirect water heater(s)
applications.
i.
Space heating only - refer to Tables 6-4
and 6-5 and Figure 6-9 "Near Boiler
Piping - Heating Only" as applicable.
42
(continued)
Flow Switch
Paddle Marking
1
E
3
1
1
APEX
Installation, Operating, & Service Instructions
ii.
Space heating plus indirect water
heater(s) – refer to Tables 6-4 and 6-5
and Figure 6-10 "Near Boiler Piping -
Heating Plus Indirect Water Heater" as
applicable.
iii. If piping indirect water heater off boiler
(see Figure 6-12), be sure that indirect
water heater and domestic hot water
circulator are sized to maintain flow
through boiler within limits shown in
Table 6-3.
NOTICE: Where it is not possible to install a
separate boiler loop, the system circulator must
be sized to ensure that the flow through boiler
stays within the defined parameters to prevent
overheating when the boiler is fired at it's full rated
input. Install a flow meter to measure the flow, or
fire the boiler at full rate and ensure the boiler DT
does not exceed 35°F (19°C).
2. Direct connection of Apex boiler to heating
system, similar to a conventional boiler, is NOT
RECOMMENDED because:
a. The flow rate through system must be the
same as through boiler and fall within limits
specified in Table 6-3.
b. Pressure drop through entire system must
be known, added to pressure drop through
boiler, and a circulator selected to provide
required flow at total calculated pressure
drop.
c. It is often very difficult to accurately
calculate the pressure drop through the
system.
d. In replacement installations, it may be
nearly impossible to get an accurate
measurement of piping amount and number
of fittings in the system. If system is zoned,
the system flow rate may drop well below
recommended minimum flow when only a
single zone is calling for heat.
106308-05 - 3/23
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