Install Instructions

ManualsBrandsTaco ManualsHeating SuppliesBoiler Reset Control

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

PC700-2 Boiler Reset Control

SUPERSEDES : 102-097 March 1, 2003

The PC700-2 is a microprocessor-based control designed to regulate the supply water temperature

of a single boiler, based on the outdoor temperature. A wiring harness is provided to be easily con-

nected to the Taco Expandable (-EXP) Controls.

The PC700-2 includes functions such as automatic reset ratio calculation, Warm Weather Shut Down

(WWSD), Minimum Boiler setting, and an optional automatic boiler differential. The control has a

digital, liquid crystal display (LCD) that normally displays the boiler supply temperature, but can dis-

play other temperatures and settings.

Control Strategy . . . . . . . . . . . . pg. 1 Control Adjustments . . . . . . pg. 5

Sequence of Operation . . . . . . . pg. 2 Troubleshooting . . . . . . . pg. 6

Installation . . . . . . . . . . . . . . . . . pg. 3 Error Messages. . . . . . . . . . . pg. 7

Settings . . . . . . . . . . . . . . . . . . . pg. 4 Technical Data . . . . . . . . . . . pg. 8

EFFECTIVE: March 1, 2004

Plant ID# 9300-1055

102-097

Input

Outdoor Sensor

Included

To Taco

Zone

Control

Input

Boiler Sensor

Included

Item

H11471

Power: 24 V ±10% 50/60 Hz 3 VA

Relay: 120 V (ac) 5 A 1/6 hp

pilot duty 240 VA

May 00

31000265

Press & Release:

Item

+ + , to adjust menu

Press & Hold:

Item

, to view settings

, to test

Com

Boil

Out

Boiler Demand

Signal wiring

must be rated

at least 300V

Made in Canada

PC700-2

Start

C US

158033

No power

VIEW

OUTDR

°F

Boiler Demand

Use

(hours)

PC700-2

Start

Item

C US

158033

OUTDR

°F

VIEW

Constant

Room Temperature

Outdoor

Temperature

Drop

Heat

Loss

Increase

Summary of content (8 pages)

PAGE 1
Instruction Sheet PC700-2 Boiler Reset Control 102-097 EFFECTIVE: March 1, 2004 SUPERSEDES : 102-097 March 1, 2003 Plant ID# 9300-1055 The PC700-2 is a microprocessor-based control designed to regulate the supply water temperature of a single boiler, based on the outdoor temperature. 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
WARM WEATHER SHUT DOWN (WWSD) When the outdoor temperature rises above the WWSD setting, the PC700-2 displays the WWSD segment and turns off the boiler. If a boiler demand from the Taco Zone Control is received, the boiler remains off. For applications where DHW is required, the DHW (priority) zone on the Taco Zone Control turns on the boiler. BOILER OPERATION While the PC700-2 has a boiler demand, the system supply water temperature is controlled by turning the boiler on and off.
PAGE 4
Installing the Outdoor Sensor  Note The temperature sensor (thermistor) is built into the enclosure. • Take the sensor cover off by sliding it upward relative to the sensor base. • Use one round or pan head screw to attach the base of the sensor to the wall. • The sensor is wall mounted and the wiring enters through the bottom of the enclosure. The hole for the cable entry must face downward in order to prevent water from entering and filling the enclosure.
PAGE 5
Boiler Design Temperature (BOIL DSGN)  The BOIL DSGN setting is the water temperature required to satisfy the building heat loss during the coldest outdoor temperature. This adjustment is typically dependent on the type of heating terminal used. The following are suggested settings for different terminal units: • Inslab Radiant ..................... 100 to 140°F (38 to 60°C) • Staple-up Radiant .......... 130 to 160°F (54 to 71°C) • Radiators ............................
PAGE 6
POWER UP On power up, the control displays all segments for 2 seconds, followed by the control version number. VIEW MENU OUTDR DSGN DIFF BOIL TARGET MIN MAX WWSD Start The control then automatically goes to operating mode, and displays the outdoor temperature. VIEW ADJUST °F °C Boiler Demand OUTDR VIEW °F Start Boiler Demand Outdoor Temperature OUTDR VIEW °F The outdoor temperature is displayed when the OUTDR element is turned on.
PAGE 7
Testing the Sensors A good quality test meter capable of measuring up to 5,000 kΩ (1 kΩ = 1000 Ω) is required to measure the sensor resistance. In addition to this, the actual temperature must be measured with either a good quality digital thermometer, or, if a thermometer is not available, a second sensor can be placed alongside the one to be tested and the readings compared. Ω First measure the temperature using the thermometer and then measure the resistance of the sensor at the control.
PAGE 8
Technical Data PC700-2 Boiler Reset Control — — — — — Power supply — Relays Sensors included: — — Boiler Start Outdoor Start Boiler Design Outdoor Design Boiler Minimum Differential WWSD Units — — — — — — — — Microprocessor PI control; This is not a safety (limit) control. 1.3 lb. (580 g) 4-3/4” H x 2-7/8” W x 7/8” D (120 x 74 x 22 mm) CSA NRTL /C; Meets ICES & FCC regulations for EMI/RFI. Indoor use only, 32 to 105°F (0 to 40°C), < 90% RH noncondensing.