Lochinvar 402 - 2072 operation manual B, Low system water volume, Three way valves in system

4 Water connections (continued)

When a mixing valve is used, an optional system return sensor should be installed into the system return piping. This will allow the display of the actual system return temperature, and will also allow control of the system return temperature when the SMART SYSTEM control is programmed for inlet temperature control. As always, installation of the system supply sensor is strongly recommended as well. This will reduce the potential for short cycling of the boiler, and provide more responsive temperature regulation, even when the SMART SYSTEM control is programmed for inlet temperature control.

Installation & Operation Manual

TABLE - 4B

MAXIMUM FLOW FOR HEATING BOILER

The maximum flow rate through the boiler with a copper

heat exchanger must not exceed the following:

Model	Maximum Flow
402, 502, 652, and 752	55 GPM
992, 1262, 1442, 1802, and 2072	90 GPM

￿CAUTION

A boiler allowed to operate at set point temperatures below the specified minimum settings may experience operational problems with the operating controls and safety switches, obstruction of the flue gas passages on the heat exchanger, incomplete combustion and possible flue gas spillage. Operation at lower than specified water temperatures may cause hazardous conditions that result in non-warrantable damage to the appliance.

If higher flow rates are required through the boiler, an optional Cupro-Nickel heat exchanger is available. Consult the factory for specific application requirements.

Low system water volume

System run time is very important to the overall operating efficiency of the boiler. Short cycling of the boiler creates problems with condensation in the vent stack, condensation on the heat exchanger, system temperature spikes, and mechanical component failures. To prevent short cycling of the boiler, it is important to limit the boiler cycles to six or fewer per hour.

Three way valves in system

The installation of a three way valve on this boiler is not generally recommended because most piping methods allow the three way valve to vary flow to the boiler. This boiler is a low mass, high efficiency appliance which requires a constant water flow rate for proper operation. Low flow rates can result in overheating of the boiler water which can cause short burner cycles, system noise, relief valve discharge and in extreme cases, a knocking flash to steam. These conditions can cause operational problems and non-warrantable failures of the boiler.

Radiant floor and snow melt heating systems

This type of heating boiler application operates in a low temperature range which requires a boiler bypass as described under the Low Temperature Bypass Requirements section. A non-metallic rubber or plastic tubing installed in a radiant (in floor) system must have an oxygen barrier to prevent oxygen from entering the system through the walls of the installed tubing. Excessive oxygen absorption into the system will result in an accelerated rate of corrosion causing a sludge buildup. This excessive corrosion will also damage the boiler and system components. Sludge formed as the result of excessive oxygen in the system can restrict water flow resulting in a premature boiler failure. Any boiler damage due to excessive oxygenation is non-warrantable.

A buffer tank is an effective way to enhance a small system load and increase heating system efficiency (see FIG. 4-6 on page 42 of this manual). Buffer tanks add water volume to the system and act as a flywheel to absorb the additional Btu’s provided by the boiler when only a single zone of a large system is calling for heat.

To calculate the proper buffer tank size for a multiple zone system:

(Run Cycle) (Output - Minimum System Load)

(Temp. Rise) (8.33) (60 Min.)

CFN2072

Min. Load = 100,000 Btu/Hr

Min. Boiler Output = 850,000 Btu/Hr

Cycle Time = 10 Min

Temp. Rise = 38

(10)(850,000 – 100,000) / (38)(8.33)(60) = 395 Gallons

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