Hydronic Heating Boilers and Domestic Water Heaters Installation and Service Manual

The installer must ensure that the boiler has adequate flow
without excessive temperature rise. Low system flow can
result in overheating of the boiler water which can cause short
burner ON cycles, system noise and in extreme cases, a
knocking flash to steam. These conditions indicate the need to
increase boiler flow by installation of a larger circulator pump
or the installation of a system bypass. System noise may also
indicate an oversized boiler.
 CAUTION: At no time should the system
pressure be less than 12 PSIG.
Figure 26 - Primary/Secondary Piping of a Single Boiler
Figure 27 - 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 K 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. 28 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 22).
Radiant Floor and Snow Melt
Heating Systems
This type of heating boiler application operates in a low
temperature range which requires a boiler bypass as described
under Low Temperature Bypass Requirements. A non-metallic
rubber or plastic tubing installed in a radiant (in floor) system
must have an oxygen barrier to prevent oxygen from entering
the system through the walls of the installed tubing. Excessive
oxygen absorption into the system will result in an accelerated
rate of corrosion causing a sludge buildup. This excessive
corrosion will also damage the boiler and system components.
Installation and
Service Manual
25
MAKE-UP
WATER
PRV
EXPANSION TANK
LWCO
(OPTIONAL)
TO SYSTEM
SYSTEM PUMP
AIR SEPARATOR
FROM SYSTEM
SECONDARY
BOILER PUMP
12" OR 4 PIPE
DIAMETERS
Table - K
LTV Valve Kits
Input
Btu/hr
LTV Valve Kit
495,000 - 745,000 VAL3048
985,000 - 2,065,000 VAL3047