Lochinvar SDT/SET065 - 119 3Boiler Side Piping SDT models, Zone with Circulator to Aquastat

SDT/SET Installation & Operation Manual

3Boiler Side Piping (SDT models)

Figures 3-1 thru 3-4 show typical boiler side piping for several common situations. Regardless of which system is used it is imperative that the flow rates called for in Table 3C are developed through the coil. This requires properly sized piping and a properly sized pump.

The system shown in FIG’s 3-1 thru 3-4 are described below:

Zone with Circulator to Aquastat

This system is like the circulator zone system on a straight heat job except that one of the zones goes to the tank instead of radiation. As on any circulator zone system check valves should be installed in each zone to prevent unwanted circulation through zones which are not calling for heat. Figure 3-1 on page 8 illustrates typical circulator zone piping.

Multiple Tank Connections (Boiler Side)

Multiple tank installations must be done in the “reverse-return” manner. The reason for this is to create the same pressure drop (and therefore, the same flow) through the coil of each tank. The boiler manifold piping must be sized so that each coil has the flow rate called for in Table 3B.

Because the pressure drop through tank coils varies from size to size, it is hard to predict the flow rate that will be developed through each coil when two tanks of different sizes are placed in the same manifold. For this reason it is best not to mix tanks of different sizes in the same zone if their recovery is critical.

Zone with Valve to Aquastat

As with the circulator zone system, this system is just like a standard heating zone system except that one of the zones is connected to the tank coil as shown in FIG. 3-2 on page

9.The system circulator must be large enough to move boiler water through the coil regardless of the flow rate required through the heating zones.

DHW Prioritization

This piping system is designed to provide direct hot water priority over the other zones in the heating system. When there is a Domestic Hot Water (DHW) call for heat, the Knight control will shut off the boiler circulator and activate the domestic hot water circulator. Once the DHW demand is satisfied, the boiler circulator will be readjusted as demand requires. The circulator must be large enough to move the boiler water through the coil in the tank, and it must meet the minimum boiler flow requirments. The recommended piping for a DHW priority system is depicted in FIG. 3-3 on page 10.

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