Lochinvar 402 - 2072 A, Minimum boiler water temperatures, Low Temperature Return Water Systems

4 Water connections

Pump Maintenance: Inspect the pump every six (6) months and oil as necessary. Use SAE 30 non-detergent oil or lubricant specified by the pump manufacturer.

The boiler is recommended for installation in a primary/ secondary piping system. This type of system uses a separate boiler circulating pump to supply flow to and from the boiler only. The secondary pump is sized based on the head loss of the boiler and related pipe and fittings in the secondary loop only.

A properly sized primary system pump provides adequate flow to carry the heated boiler water to radiation, air over coils, etc. The fittings that connect the boiler to the primary system should be installed a maximum of 12 inches (0.30m) (or 4 pipe diameters) apart to ensure connection at a point of zero pressure drop in the primary system. There should be a minimum of 10 pipe diameters of straight pipe before and after the boiler secondary loop connections to prevent turbulent flow at the secondary loop connections. The secondary loop piping to and from the boiler must have a fully ported ball valve installed in both the supply and return side piping. The ball valves must be fully ported having the same inside diameter as the installed piping. The ball valve in the piping supplying water to the boiler will only be used as a service valve. The ball valve installed in the discharge from the boiler back to the primary system will be used to adjust boiler flow and temperature rise to ensure proper performance.

The boiler primary piping system must have a circulator installed in the main system loop to carry the heated boiler water to the point of use in the main system.

Multiple boilers may also be installed with a primary/secondary manifold system. Multiple boilers should be connected to the common manifold in reverse return to assist in balancing flow to multiple boilers.

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 cycles, system noise, relief valve discharge and in extreme cases, a knocking flash to steam. These conditions indicate the need to increase boiler flow to and from the boiler. This is generally accomplished by either increasing the size of the boiler pump or by increasing the diameter of the piping that connects the boiler to the primary system. A larger diameter pipe reduces head loss and increases flow.

￿ CAUTION	At no time should the system pressure be less
	than 12 PSIG.

Minimum boiler water temperatures

Inlet water temperatures below the specified minimum of 140°F (60°C) can excessively cool the products of combustion resulting in condensation on the heat exchanger. Condensation on the heat exchanger can cause operational problems, bad combustion, sooting, flue gas spillage and reduced service life of the related components. See the Low Temperature Bypass Requirements section for boiler system applications below the minimum specified temperature.

Installation & Service Manual

Low Temperature Return Water Systems

Any non-condensing boiler will develop operational problems when exposed to inlet water temperatures below 140°F. Lochinvar offers a low temperature protection valve (LTV) that is factory preset to maintain 140°F inlet water to the boiler regardless of the system return water temperature. See Table 4A for available valve kits.

TABLE 4A

LTV VALVE KITS

MODEL	LTV VALVE KIT
402 - 752	VAL3048
992 - 2072	VAL3047

Low temperature bypass requirements

To prevent condensation problems, a boiler MUST NOT be operated (other than for brief periods during initial system startup) with an inlet water temperature of less than 140°F (60°C). If normal system return temperatures are less than the required 140°F (60°C) boiler inlet requirement, a method of low return water temperature protection MUST BE provided to protect the boiler.

For Example: Night Setback of the system loop water temperature, Night Shutdown and Weekend Shutdown of the entire boiler / heating system, and Indoor / Outdoor Air Reset of the system loop water temperature. If any of these control functions are being utilized, some type of low return water protection MUST BE provided.

If the boiler heating system will be used on a Water Source Heat Pump System, Radiant Floor Heating System, Snow Melting Heating System, etc., some type of low return water protection must be provided.

Condensation can cause operational problems, bad combustion, sooting, flue gas spillage and reduced service life of the vent system and related components.

To prevent system return water temperature below 140°F (60°C) from entering the boiler inlet, an electrically actuated 3-way mixing valve is available, consult manufacturer for kit availability (see FIG. 4-5 on page 41). By using this valve, the SMART SYSTEM control will bypass outlet water back into the inlet of the boiler to maintain the inlet temperature above 140°F (60°C).

A fast acting, self contained mixing valve, set to 140°F (60°C), may also be used. The installation of this valve must be done as shown in FIG. 4-5. This arrangement will maintain the required flow through the boiler.

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