Benchmark 750-3000 Installation & Startup Manual
SECTION 2
– INSTALLATION
OMM-115_D
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5/9/2019
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Figure 2-4b: BMK 1500/2000 and BMK 2500/3000 Supply and Return Locations
2.6.3 Dual Inlet Return Piping
The standard dual inlet connections
allow these units to be configured with a separate cooler
return temperature zone, rather than blending high and low return temperature zones. Utilizing
the dual return capability, these boilers can take further advantage of the condensing
capabilities. When configured with a lower return temperature zone or AERCO SmartPlate,
thermal efficiency can improve by up to 6% (Based on an 80 °F (26.7 °C) minimum return water
temperature at full fire. Lower return temperatures are possible which would yield even greater
efficiency gains. The maximum temperature differential across the boiler heat exchanger is 100
°F (37.8 °C).
To use the secondary inlet, pipe the
warmer
return water to the
secondary
(upper) inlet and
the
cooler
return water to the
primary
(lower) inlet. If the flow through both the primary and the
secondary return is constant, then the combined minimum flows must equal the specified
minimum flow of the boiler. If the flow through either of the inlet returns is intermittent, then the
minimum flow through one of the return connections must always equal the specified minimum
flow of the boiler. Contact your AERCO representative for additional information.
CONDENSATE DRAIN
HOT WATER
OUTLET
(SUPPLY)
SECONDARY
WATER INLET
(
WARMER
WATER RETURN)
AIR INLET
PRIMARY
WATER INLET
(
COOLER
WATER
RETURN)
EXHAUST MANIFOLD
BMK 1500/2000
BMK 2500/3000
2” NATURAL GAS OR
1” PROPANE INLET
