PART 5: BOILER PIPING (CONTINUED)
B. GENERAL PIPING INFORMATION
C. BACKFLOW PREVENTER
Use a backflow preventer specifically designed
for hydronic boiler installations. This valve
should be installed on the cold water fill supply
line per local codes. (See Boiler Piping Details)
D. SYSTEM WATER PIPING METHODS
Expansion tank and make-up water
1. Ensure that the expansion tank size will
handle boiler and system water volume and
temperature. Allow for boiler and its piping:
2. The expansion tank must be located as
shown in Boiler Piping Part 5 or following
recognized design methods. See tank
manufacturer’s instructions for details.
3. Connect the expansion tank to the air
separator only if the separator is on the
suction side of the circulator. Always install
the system fill connection at the same point
as the expansion tank connection to the
system.
4. Most chilled water systems are piped using a
closed type expansion tank.
Diaphragm (or bladder) expansion tank
1. Always install an automatic air vent on top of
the air separator to remove residual air from
the system.
E. CIRCULATORS
Sizing space heat system piping
1. See Piping Details in this manual Part 5. In all
diagrams, the space heating system is
isolated from the boiler loop by the
primary/secondary connection.
2. Size the piping and components in the space
heating system using recognized design
methods.
F. HYDRONIC PIPING WITH CIRCULATORS,
ZONE VALVES AND MULTIPLE BOILERS
The Mod Con Boiler is designed to function in a
closed loop Hydronic System. We have also in-
cluded a Temperature and Pressure gauge that al-
n
CAUTION
DO NOT install automatic air vents on closed-
type expansion tank systems. Air must remain
in the system and return to the tank to provide
its air cushion. An automatic air vent would
cause air to leave system, resulting in water-
logging the expansion tank.
n
CAUTION
DO NOT use the boiler circulator in any location
other than the ones shown in this manual. The
boiler circulator is selected to ensure adequate
flow through the Mod Con Boiler. Failure to
comply could result in unreliable performance
and nuisance shut downs from insufficient flow.
CAUTION
Undersized expansion tanks cause system
water to be lost from relief valve and makeup
water to be added through a fill valve. Eventual
boiler failure can result due to excessive make-
up water addition. This type of failure is NOT
covered by warranty.
GAS-FIRED BOILER Boiler Manual
14
NOTICE
The Mod Con Boiler control module uses
temperature sensors to provide both high limit
protection and modulating temperature control.
The control module also provides low water
protection by sensing the water level in the heat
exchanger. Some codes/jurisdictions may
require additional external controls.
CAUTION
All piping methods shown in this manual use
primary/secondary connection to the boiler loop.
This is to avoid the possibility of inadequate flow
through the boiler. For other piping methods,
consult your local Heat Transfer Products
representative or refer to separate Mod Con
Boiler piping details in this manual (Part 5).
Mod Con 300 2.9 Gallons
Mod Con 500 4.2 Gallons
Mod Con 850 5.8 Gallons
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