Install Instructions

ManualsBrandsTaco ManualsHeating SuppliesBoiler Reset Control 2-Stage

The PC702-1 is a microprocessor-based control designed to regulate the supply water temperature

from a two stage boiler system based on the outdoor temperature or DHW requirements. A wiring

harness is provided to be easily connected to the Taco Expandable (-EXP) Controls.

The PC702-1 includes functions such as automatic reset ratio calculation, Warm Weather Shut Down

(WWSD), Minimum Boiler setting, adjustable interstage delay setting, optional boiler rotation, and an

optional automatic boiler differential. The control has a digital, liquid crystal display (LCD) that nor-

mally displays the Boiler Supply temperature, but can display other temperatures and settings.

Control Strategy . . . . . . . . . . . . pg. 1 Control Adjustments . . . . pg. 6

Sequence of Operation . . . . . . . pg. 2 Troubleshooting . . . . . . . pg. 7

Installation . . . . . . . . . . . . . . . . . pg. 4 Error Messages. . . . . . . . . . . pg. 8

Settings . . . . . . . . . . . . . . . . . . . pg. 5 Technical Data . . . . . . . . . . . pg. 8

Control Strategy

OUTDOOR RESET

In order to properly control a hot water heating system, the heat supplied

to the building must equal the heat lost by the building.

• The heat supplied to a building is proportional to the temperature of the

supply water and the surface area of the heating element. A small surface

area such as baseboard radiators requires a higher water temperature

than a larger surface area such as radiant floors.

• The heat lost from a building is dependent on the outdoor temperature,

as well as other factors. As the outdoor temperature drops, the building

heat loss increases.

Instruction Sheet

PC702–1 Two Stage Boiler

Reset & DHW Control

SUPERSEDES : 102-106, dated June 1, 2000

EFFECTIVE: March 1, 2004

Plant ID# 9300-1059

102-106

Constant

Room Temperature

Outdoor

Temperature

Drop

Heat

Loss

Increase

To T aco

Zone

Control

Item

H1192A

Power : 24 V ±10% 50/60 Hz 3 VA

Relays: 120 V (ac) 5 A 1/6 hp pilot 240 VA

Demand: 20 to 260 V (ac) 2 VA

Jul 00

31000265

Press & Hold:

Item,

to view settings

, to test

Press & Release:

Item +

+ to adjust menu

Signal wiring

must be rated

at least 300V

Made in

Canada

PC702-1

Com

Sup

Out

Do not apply power

Rotation On / Off

Boiler

Demand

DHW

Demand

Interstage

Delay

Start

Stage

1 1

Stage

2 2

Input

OutdoorSensor

Included

Input

Boiler Sensor

Included

DHW

Demand

CUS

158033

Output

Boiler

Output

Boiler

OUTDR

°F

1 2

VIEW

PC702

Item

CUS

158033

OUTDR

°F

VIEW

1 2

Boiler

Demand

DHW

Demand

Interstage

Delay

Start

Summary of content (8 pages)

PAGE 1
Instruction Sheet PC702–1 Two Stage Boiler Reset & DHW Control 102-106 EFFECTIVE: March 1, 2004 SUPERSEDES : 102-106, dated June 1, 2000 Plant ID# 9300-1059 The PC702-1 is a microprocessor-based control designed to regulate the supply water temperature from a two stage boiler system based on the outdoor temperature or DHW requirements. A wiring harness is provided to be easily connected to the Taco Expandable (-EXP) Controls.
PAGE 2
Reset Ratio • Boiler starting temperature • Outdoor starting temperature • Boiler design supply water temperature • Outdoor Design Temperature 210 (99) Design Conditions 190 (88) 170 (77) 150 (65) 130 (54) Reset Ratio Starting Point 110 (43) 90 (32) Supply water temperature Operation of a hot water heating system can generally be improved by modulating the supply water temperature as the outdoor temperature changes.
PAGE 3
BOILER DEMAND The PC702-1 obtains a boiler demand through the Taco Zone Control when a zone calls for heat. When the PC702-1 receives a boiler demand, the Boiler Demand pointer is displayed in the LCD. Zone 1 Zone 2 Zone 3 Zone 4 OUTDR VIEW °F 12 Start DHW DEMAND Interstage Delay DHW Demand Boiler Demand Item ® The PC702-1 obtains a DHW demand when a voltage between 24 and 240 V(ac) is applied across the two DHW demand wires (black wires) that come out of the back of the control.
PAGE 4
INTERSTAGE DELAY The PC702-1 has an adjustable interstage delay setting. This setting sets the minimum time delay between the firing of the first stage and the firing of the second stage. Each stage has a minimum on time, and a minimum off time of 30 seconds. Installation Caution Improper installation and operation of this control could result in damage to the equipment and possibly even personal injury.
PAGE 5
STEP THREE Wiring to the Zone Control Connect the PC702-1 cable to the Add-On interface on the Taco Zone Control. Ensure the Mode switch on the Zone Control is set to Reset. Wiring the Sensors Do not apply power to these terminals as this will damage the control. 5 6 7 Com Sup Out Outdoor Sensor Connect the two wires from the Outdoor Sensor to the terminals Com — Out (5 and 7). The Outdoor Sensor measures the outdoor air temperature.
PAGE 6
to condense. Consult the boiler manufacturer for recommended minimum boiler supply temperatures. Some typical settings are as follows: • Steel fire tube boiler ….......... 140 to 160°F (60 to 71°C) • Condensing boiler ................. Off • Cast iron boiler ….................. 135 to 160°F (57 to 71°C) • Electric boiler ........................ Off • Copper tube boiler ….............
PAGE 7
POWER UP On power up, the control displays all segments for 2 seconds and the control version number. The control then automatically goes to operating mode, and displays the outdoor temperature. VIEW MENU OUTDR DSGN DIFF BOIL TARGET MIN MAX WWSD Start Interstage Delay VIEW ADJUST °F °C 12 DHW Boiler Demand Demand OUTDR VIEW °F 12 Start Interstage Delay DHW Boiler Demand Demand Outdoor Temperature OUTDR VIEW °F The OUTDR element is turned on.
PAGE 8
STEP SIX • Install the wiring cover over the wiring chamber and secure it with the screw provided. • Place the front cover on the control and snap it into place. • It is important to explain the operation of this control within the system to the end user, and to anyone else who may be operating the system. Error Messages Whenever a fault is detected, an error message will be displayed to indicate the location of the problem.