Raypak 751 manual Hydronic Heating

Table D-1

40°F

ΔP Should include typical piping To/From a single tank as well as bypass piping.

Table E: Rate of Flow and Pressure Drop

NOTE: gpm flow rates limited by maximum acceptable velocity through heat exchanger tubes. May be increased by 10% for closed heating systems. Pressure drop would increase by 21%.

HYDRONIC HEATING

Pump Selection

In order to ensure proper performance of your boiler system, you must install a properly sized pump. Raypak recommends using a 20°F ΔT as design ΔT. (ΔT is the temperature difference between the inlet and outlet water when the boiler is firing at full rate). If a ΔT larger than 20°F is necessary, the bypass must be installed and adjusted to ensure proper hydraulics through the boiler while still allowing minimum flow to satisfy the safety flow switch. See Table E for flow rate requirements.

Pressure Drop in Feet of Head Feedwater Regulator

Raypak recommends that a feedwater regulator be in- stalled and set at 12 psi minimum pressure at the highest point of the 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 connec- tion 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 recom- mended that the piping be insulated.

Air-Separation/Expansion Tank

All boilers should be equipped with a properly sized expansion tank with an air separation 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.

13