Burnham K2WT Residential Installation, Operating And Service Instructions page 79

IX. System Piping
Method 2: Direct Connection to Heating System (Generally NOT Recommended)
In some relatively rare cases it may be possible to connect this boiler directly to the heating system as is done
with conventional boilers (Figure 9.7). If this is done, the flow rate through the boiler will equal the flow rate
through the system. The flow rate through the system must therefore always remain within the limits shown in
Table 9.1. For this reason, the pressure drop through the entire system must be known.
This method is generally not recommended because it is often very difficult to accurately calculate the pressure
drop through the system. In replacement installations, it may be impossible to get an accurate measurement of
the amount of piping and number of fittings in the system. In addition, if the system is zoned, the system flow
may drop well below the minimum required when only one zone is calling for heat.
The one advantage to this method is its installation simplicity. It may make sense to use this method when the
boiler is to be installed with a new single zone system having a low-pressure drop.
Figure 9.8 shows the performance curve for the pump in each boiler model, taking into account the pressure
drop through the boiler's heat exchanger and internal piping. These curves therefore show the flow that can be
achieved through the boiler as a function of the pressure drop through the connected piping. Calculation of the
system pressure drop must be performed by someone having familiarity with pressure drop calculations, such
as an HVAC engineer.
NOTICE Where it is not possible to install a separate boiler loop, the system circulator must be sized to
ensure that the flow through the boiler stays within the defined parameters to prevent overheating when
the boiler is fired at it's full rated input. Install a flow meter to measure the flow, or fire the boiler at full
rate and ensure the boiler delta T does not exceed 35°F (19°C).
Backflow
Preventer
Water
Notes:
1. Boiler Pump Located Inside Boiler Jacket.
2. Manual Air Vent Located On Top Of Heat Exchanger.
See Figure 11.1.
It is the installers responsibility to select boiler
piping configurations that provide the proper
flow rates and performance for the boiler.
Figure 9.7: Piping Method #2 - Direct Connection of Boiler to Heating System
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(continued)
Radiation
To
Radiation
Air Separator
& Air Vent
Fill
Valve
Cold
Line
Expansion
Tank
CAUTION
Balancing
Valve
Flow
Check
Y-Strainer
(Recommended)
Boiler
Pump
Drain
Valve
Full Port
Isolation
Valves
Relief
Valve
Unions
79