High Flow Systems
When the flow rate of the system exceeds the
maximum allowable flow rate through the boiler
(Table I), boiler bypass piping should be
installed.
The bypass will divert the required portion of the
system flow to the boiler and bypass excess
system flow. This will effectively reduce boiler
flow to an acceptable rate and increase system
flow. The bypass piping should be sized equal
to the system piping. Figure 16 depicts the
proper piping arrangement for the Boiler
Bypass.
Low Water Temperature System
Any boiler system operating at a temperature of
less than 140°F is considered a “low water
temperature system” and must be piped with a
low temperature bypass. There are a number of
hydronic boiler applications that call for system
water temperatures in the range of 60°F to
100°F. Typical applications are: Radiant
heating systems; Water source heat pump
systems; Greenhouse soil heating and irrigation
systems; Process and manufacturing operations.
These installations often incur problems resulting
from boiler condensation, thermal stresses and
poor overall system efficiency.
Copper tube boilers are particularly adaptable
to these applications for several reasons:
A copper tube boiler is an instantaneous
boiler, requiring virtually no heat-up time,
and having no temperature “overshoot”.
Result - High system efficiency.
The boiler’s unique construction prevents the
transfer of heat exchanger thermal stresses to
other boiler components, reducing wear and
tear while increasing equipment life.
Its compact, simple design and low
boiler mass permits a simple bypass
arrangement which will allow the system to
be operated at any temperature above
60°F (16°C).
A boiler operated with an inlet temperature of
less than 140°F (60°C)
must
have a bypass to
prevent problems with condensation.
A Low Temperature Bypass as shown in Figure
15 should be piped into the system at the time
of installation. 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. The bypass allows part of the
boiler discharge water to be mixed with the
cooler boiler return water to increase the boiler
inlet temperature to at least 140°F (60°C). This
will prevent the products of combustion from
condensing in most installations. Size low
temperature bypass piping equal to system
piping, and use fully ported control valves.
1.
2.
3.
L o c h i n v a r
D E S I G N E R
’
S
G U I D E
E F F I C I E N C Y
+
B O I L E R
6 1 5 - 8 8 9 - 8 9 0 0
17
(FIG. 16) LOW TEMPERATURE BYPASS SYSTEM PIPING
HEATING SUPPLY
LOOP
TO FLOOR
DRAIN
BYPASS
MAKE-UP WATER
HEATING RETURN LOOP
LIT0473
