17
LP- 428 REV. 9.2.14
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 HTP representative, or refer to Boiler Piping Details in
this manual.
D. SYSTEM WATER PIPING METHODS
EXPANSION TANK AND MAKE-UP WATER
1. Ensure that the expansion tank is sized to correctly handle boiler and system water volume and temperature.
Table 2
Undersized expansion tanks cause system water to be lost from the relief valve, causing make-up water to be added. Eventual boiler
failure can result due to excessive make-up water addition. SUCH FAILURE IS NOT COVERED BY WARRANTY.
2. The expansion tank must be located as shown in Boiler Piping Details, or following recognized design methods. See expansion 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
Always install an automatic air vent on top of the air separator to remove residual air from the system.
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 an air cushion. An automatic air vent would cause air to leave the system, resulting in improper operation of the expansion tank.
E. CIRCULATORS
DO NOT use the boiler circulator in any location other than the ones shown in this manual. The boiler circulator location is selected to
ensure adequate flow through the boiler. Failure to comply with this caution could result in unreliable performance and nuisance
shutdowns from insufficient flow.
SIZING SPACE HEAT SYSTEM PIPING
1. 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 boiler is designed to function in a closed loop hydronic system. The included temperature and pressure gauge allows the user to
monitor system pressure and outlet temperature from the boiler. It is important to note that the boiler has a minimal amount of pressure
drop that must be calculated when sizing the circulators. Each boiler installation must have an air elimination device that will remove air
from the system.
Install the boiler so the gas ignition system components are protected from water (dripping, spraying, etc.). Allow clearance for basic
service of the boiler circulator, valves, and other components. Observe minimum 1” clearance around all uninsulated hot water pipes
when openings around pipes are not protected by non-combustible materials.
On a boiler installed above radiation level, some states and local codes require a low water cut off device. This is provided standard on
the Mod Con boiler. Check with local codes for additional requirements. If the boiler supplies hot water to heating coils in air handler
units, flow control valves or other devices must be installed to prevent gravity circulation of boiler water in the coils during the cooling
cycle. Chilled water medium must be piped in parallel with the boiler.
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