Installation and Operation Manual

26
entering boiler. See Figure 20. Also, consult I=B=R
Installation and Piping Guide No. 250.
2. If boiler is connected to heating coils located in
air handling units where they may be exposed to
refrigerated air, boiler piping must be equipped with
ow control valves to prevent gravity circulation of
boiler water during cooling system operation.
3. The piping diagrams shown (Figure 21, Detail “A”
and Detail “B”) are recommended for optimum
operation and long term reliability.
Burnham Commercial recommends maintaining
temperature differential (drop) across the system
at 40°F or less, and return water temperature at
minimum of 135°F.
Continued boiler operation for prolonged periods of
time under conditions when temperature differential
across the system exceeds 40°F and/or return water
temperature stays below 135°F, may result in
premature boiler failure due to ue gas condensation
and/or thermal shock.
Pump ow rates and minimum boiler supply and
return pipe sizes are shown in Table 4.
Figure 21: Recommended Boiler Piping for Circulator Zoned Heating Systems
Detail “A”: Blend Pump Piping
Detail “B”: Primary/Secondary Piping
with By-Pass