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SECTION E: HYDRONIC HEATING PIPING
PUMP SELECTION
In order to insure proper performance of your boiler system, you must install a properly sized pump. Raypak recommends
using a 20°F Delta T as design Delta T. (Delta T is the temperature difference between the inlet and outlet water when the
boiler is firing at full rate). If a Delta T larger than 20°F is necessary, see Table D-1 for minimum flow rate requirements.
PRESSURE DROP IN FEET OF HEAD
FEEDWATER REGULATOR
Raypak recommends that a feedwater regulator be installed and set at 12 PSIG minimum pressure at the highest point of
system. Install a check valve or back flow device upstream of the regulator, with a manual shut off valve as required by local
codes.
PIPING - HEATING BOILERS
All high points should be vented. Purge valves and a bypass valve should be installed. A boiler installed above radiation
level must be provided with a low water cutoff device. The boiler, when used in connection with a refrigeration system, must
be installed so the chilled medium is piped in parallel with the boiler with appropriate valves to prevent the chilled medium
from entering the boiler.
The boiler piping system of a hot water heating boiler connected to heating coils located in air handling units where they may
be exposed to circulating refrigerated air, must be equipped with flow control valves or other automatic means to prevent
gravity circulation of the boiler water during the cooling cycle. It is highly recommended that the piping be insulated.
AIR-SEPARATION/EXPANSION TANK
All boilers should be equipped with a properly sized expansion tank and air separator fitting as shown in the following
diagrams.
THREE-WAY VALVES
Valves designed to blend water temperatures or reduce water circulation through the boiler should not be used. Raypak
heaters are high recovery low mass heaters not subject to thermal shock. Raypak offers a full line of electric sequencers that
produce direct reset of boiler water temperature. Refer to the Controls Section in our Complete Catalog.
Table E-1
NOTE: Basis for Minimum flow -20 gpm or 40° DT
Maximum flow -90 gpm.
Flow switch will not operate if flow is less than 20 gpm.
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