Lochinvar 399, 999 - 750 Primary/Secondary Boiler Piping, Heat Exchanger Pressure Drop Chart

Installation and Service Manual

Example: The boiler inlet temperature is 160°F (71°C) and the boiler outlet temperature is 180°F (82°C), this means that there is a 20°F (11°C) temperature rise across the boiler.

Heat Exchanger Pressure Drop Chart

FIG. 34 Pressure Drop Chart 399,999 - 750,000

Pressure Drop Chart

990,000 - 2,070,000 Btu/hr Models

PRESSURE DROP IN FEET HEAD

FLOW IN GALLONS PER MINUTE

FIG. 35 Pressure Drop Chart 990,000 - 2,070,000

Circulator Pump Specifications

1.Maximum operating pressure for pump must exceed system operating pressure.

2.Maximum water temperature should not exceed nameplate rating.

3.Cast iron circulators may be used for closed loop systems.

4.A properly sized expansion tank must be installed near the boiler and on the suction side of the pump.

Circulator Pump Operation

(Heating Boilers Only)

The boiler pump should run continuously unless the boiler is provided with the pump delay control system. External wire leads are furnished with this option to allow the power supply for the pump to be switched across the normally open contacts of the relay, allowing the control relay to cycle the pump on each call for heat. The field installed boiler pump using the

factory supplied pump control system must not exceed 10 AMPS at 120VAC. As shipped from the factory, the control system is set to cycle the boiler pump on at each call for heat before the burners fire and run the pump for a 30 second period after the thermostat is satisfied. This will remove any residual heat from the combustion chamber before turning the pump off. See Wiring Diagram, page 64.

Pump Installation and Maintenance

For installation and maintenance information on the circulator pump, refer to pump manufacturers instructions included in the instruction package.

Primary/Secondary Boiler Piping

Boiler installations with a primary/secondary piping system as shown in FIG. 36 are recommended. This type of system uses a dedicated pump to supply flow to the boiler only. This secondary pump is sized based on desired boiler flow rate, boiler head loss and head loss in the secondary system piping only. A properly-sized primary (system) pump provides adequate flow to carry the heated boiler water to radiation, air over coils, etc. The points of connection to the primary (system) loop should be a maximum of 12" (or 4 pipe diameters) apart to ensure connection at a point of zero pressure drop in the primary system. Multiple boilers may also be installed with a primary/secondary manifold system as shown in FIG. 37. The multiple boilers are connected to the manifold in reverse return to assist in balancing flow to multiple boilers.

CAUTION: DO NOT allow the flow in the primary (system) loop to drop lower than the flow in the secondary loop at any time during boiler operation. Improper operation of the boiler(s) and possible tripping of the high limits and relief valves may occur.

The installer must ensure that the boiler has adequate flow without excessive temperature rise. Low system flow can result in overheating of the boiler water which can cause short burner on cycles, system noise and in extreme cases, a knocking flash to steam. These conditions indicate the need to increase boiler flow by installation of a larger circulator pump or the installation of a system bypass. System noise may also indicate an oversized boiler.

CAUTION: At no time should the system

pressure be less than 12 PSIG.

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