Dunkirk ARTESIAN 220 Installation And Operating Instructions Manual page 21

3-Way Zone Valve System
This system offers a simple method of prioritizing the tank (Diverting all boiler output to the tank when
the tank thermostat calls for heat). In this system, a 3-way zone valve is used which has a common
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port a "normally open" port, and a "normally closed" port The zone valve motor is wired to be
energized by the water heater thermostat (see Part VII for wiring information). The common side of the
zone valve is connected to the boiler. The heating system is connected to the normally open side of the
zone valve, and the water heater tank is connected to the normally closed side of the zone valve. As
long as the water heater is not calling for heat, the boiler water can flow from the heating system zone,
through the normally open side of the 3-way valve, to the boiler. As soon as the water heater calls for
heat, the zone valve is energized, and boiler water can only flow through the water heater zone. Figure 6
illustrates typical piping using a 3-way zone valve.
Radiant Panel Or Other "Low Temperature System"
The first hour ratings published in this manual are based on an aquastat setting of 180°F in the tank. If,
for whatever reason, the boiler water temperature going to the heating system is designed to be much
under 180°F, special piping is needed to provide water to both the tank (high temperature) and the
system (low temperature) at the proper temperatures. Two ways of doing this are with a heat exchanger
or a 4 -way valve.
In either system, the water heater must be connected to the boiler before any means used to control the
temperature of the water going to the system. The temperature of the water going through the water
heater is thus limited only by the boiler high limit setting. The high limit setting on the boiler aquastat
should be set 15-20°F higher than the tank aquastat on the Artesian.
Figure 7 illustrates the use of a heat exchanger to control the temperature of the water going to the "low
temperature" system. This heat exchanger may be shell and tube, plate type, or a second Artesian. The
low temperature system water is completely isolated from the water passing through the boiler and
Artesian. For this reason, the low temperature system must be equipped with its own expansion tank,
fill, and air removal apparatus. The temperature in this system may be controlled with an aquastat in the
low temperature side.
Figure 8 illustrates the use of a 4-way valve to control maximum heating zone (low) temperature while
allowing high temperature boiler water to enter the tank zone. The way valve may be manually set to
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provide the maximum allowable temperature to the heating zone or it may be provided with a motor to
control the valve in response to some parameter (outdoor temperature for example).
Artesian Manifold Piping (Boiler Side)
Multiple tank installations must be done in the "reverse return" manner illustrated on figure 9. The reason
for this is to create the same pressure drop (and therefore the same flow) through each tank. The boiler
manifold piping must be sized so that each tank has the flow rate called for in Table 1. For example, if
two model 220's (90 MBH) are to be manifolded together, the circulator and zone piping common to both
tanks must be capable of moving 5.4 GPM (2 x 2.7 GPM). The boiler must be capable of producing 180
MBH to supply the Water heater.
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