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2 optional two- stage operation - heating only, 3 optional two- stage operation - makeup air – Reznor RPBL Unit Installation Manual User Manual

Page 45

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Form I-SSCBL/RPBL, P/N 149159 R7, Page 45

TABLE A - Recommended Settings for Staging Application - Options AG3, AG15

Option

No. of

Furnaces

Ductstat Settings - Set

each ductstat control (See FIGURE 47) in furnace "order"

1st

2nd

3rd

4th

Sequence of Staging with these settings

AG3

1

70°F

--

--

--

66°F High Stage ► 70°F Low Stage ► 74°F Shutdown

2

70°F

64°F

--

--

60°F High Stage Both Furnaces ► 64°F Low Stage 2nd Furnace ► 68°F

Shutdown 2nd furnace ► 70°F Low Stage 1st furnace ► 74°F Shutdown

1st furnace

3

70°F

66°F

62°F

--

58°F High Stage All Furnaces ► 62°F Low Stage 3rd Furnace ► 66°F

Shutdown 3rd Furnace; Low Stage 2nd Furnace ► 70°F Shutdown 2nd

furnace; Low Stage 1st Furnace ► 74°F Shutdown 1st Furnace

Option AG15 - Adjust the setpoint and the differential of the temperature selector (Johnson #A350). Adjust the offset

potentiometer on each of the stage adder modules (Johnson #S350). The settings listed below will provide the same sequence

of staging as shown above for Option AG3. Follow the manufacturer's instructions provided. IMPORTANT: Set the temperature

selector and each stage adder module to "HEAT". Follow the wiring diagram to obtain proper sequencing.

Option

No. of

Furnaces

Temperature Selector (A350)

Stage Adder (S350) Offset Settings (Refer to

FIGURE 48)

Setpoint

Differential

AG15

1

74°F

8°F

4°F

--

--

--

--

--

--

2

74°F

14°F

10°F

6°F

4°F

--

--

--

--

3

74°F

16°F

10°F

8°F

8°F

4°F

4°F

--

--

Operation: The differential setting and offset degrees allow the controls to adapt to any adjustment in temperature selection (50-

130°F).

All furnaces are standardly equipped with a 24-volt combination valve which includes

the automatic electric on-off valve controlled by the room thermostat, the pressure

regulator, the safety pilot valve, and the manual shutoff valve. The standard gas valve

allows for single-stage control from a single-stage, 24-volt thermostat.

8.8.2 Optional Two-

Stage Operation -

Heating Only

The standard combination control valve is replaced with a two-stage combination gas

control valve providing for low fire or high fire operation controlled by a two-stage

thermostat. First stage (low fire) is factory set (not field adjustable). Both high and low

stages are controlled by a Servo regulator, maintaining constant gas input under wide

variations in gas supply pressure. See instructions packed with the unit for specific gas

valve specifications, wiring, and operating instructions.

8.8.3 Optional Two-

Stage Operation -

Makeup Air

On systems with more than one furnace section, there are two methods of achieving

multiple-stage makeup air operation. In addition, for each of these methods, there are

two types of control mechanisms. Consult the wiring diagram on the furnace to identify

the optional control system (Option AG 3, 15, 4, 5, 17, 18, 19, or 20).
The first method, identified by Options AG3 or AG15, is comparable to the two-stage

heating units. Instead of control from a two-stage room thermostat, the discharge air

temperature is monitored and the two-stage gas valve is controlled by a two-stage

ductstat. When the discharge air temperature drops to the setpoint, low fire is ener-

gized. If low fire cannot satisfy the ductstat setting, high fire is energized. Since the

packaged systems may include two or three furnace sections, and each section is

equipped with a two-stage gas valve, the operation stages increase with the number of

furnace sections. Set the ductstats as indicated in

TABLE A, below.

The second method of multiple-stage makeup air operation is applicable only to

systems that include two or three furnace sections. On systems with two furnaces,

this optional control system is identified as

Option AG4, AG17, or AG18. On pack-

aged systems with three furnace sections, this optional control method is identified

as

Option AG5, AG19, or AG20. Each furnace in the package is equipped with a

single-stage gas valve. The single-stage gas valves are staged by two-stage ductstats.

The furnaces are staged in sequence. This concept will achieve two-stage control on

packaged systems with two furnaces and three-stage control on systems with three

furnaces. Set the ductstats as indicated in

TABLE B, page 46.

The two types of ductstat control mechanisms used in these multiple-stage systems

are

either --

(1) the complete ductstat (including the sensor and temperature selector; see FIGURE

47) is installed in the furnace discharge (Option AG3, AG4, and AG5) or

(2) a sensing probe only is installed in the heater discharge (See FIGURE 49.) with the

sensing probe electrically connected to a remote electronic temperature selector

(

FIGURE 48).

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