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Hydronic Heating Boilers and
Domestic Water Heaters
36
INSTALLATION
Continued
FIG. 36 Primary/Secondary Piping of a Single Boiler
FIG. 37 Primary/Secondary Piping of Multiple Boilers
Low Temperature Return Water
Systems
Any non-condensing boiler and venting system will develop
operational problems when exposed to inlet water
temperatures below 140°F. Lochinvar offers a low
temperature protection valve (LTV) that is factory preset to
maintain 140°F inlet water to the boiler regardless of the
system return water temperature. See Table O for available
valve kits.
Be sure to install the LTV valve per the piping diagrams
included with the kits. Alternatively, a bypass as shown in
FIG. 38 may be piped into the system. This piping is like a
primary/secondary boiler installation with a bypass in the
secondary boiler piping. Inlet water temperatures below 140°F
(60°C) can excessively cool the products of combustion
resulting in condensation on the heat exchanger and in the flue.
Condensation can cause operational problems, bad
combustion, sooting, flue gas spillage and reduced service life
of the vent system and related components. The bypass allows
part of the boiler discharge water to be mixed with the cooler
boiler return water to increase the boiler inlet temperature
above 140°F (60°C). This should prevent the products of
combustion from condensing in most installations. The bypass
should be fully sized with a balancing valve to allow for proper
adjustment. A valve must also be provided on the boiler
discharge, after the bypass. Closing this discharge valve forces
water through the bypass. Start boiler adjustment with the
bypass valve in the full open position and the boiler discharge
valve half open. A small amount of the higher temperature
boiler discharge water is mixed with the system water to
maintain the desired lower system temperature. A remote low
temperature range operator is recommended to control the
boiler operation based on the lower system temperature. (See
Terminal Strip Connection Options starting on
page 40).
FIG. 38 Boiler with Low Temperature Bypass Piping
Table - O
LTV Valve Kits
Input
Btu/hr
LTV Valve Kit
399,999 - 750,000 VAL3048
990,000 - 2,070,000 VAL3047