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S
UPERSEDES : 102-106, dated
Plant ID# 9300-1059
OUTDR
VIEW
°F
1 2
Start
Interstage
DHW
Boiler
Delay
Demand
Demand
Item
®
C
US
PC702
158033
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
June 1, 2000
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 . . . . . . . . . . . .
Sequence of Operation . . . . . . .
Installation . . . . . . . . . . . . . . . . .
Settings . . . . . . . . . . . . . . . . . . .
Press & Hold:
Item, to view settings
, to test
Press & Release:
Item +
+
OUTDR
Start
DHW
Item
Demand
1
2
Stage
1
1
Output
Boiler
Output
Boiler
pg. 1
pg. 2
pg. 4
pg. 5
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
to adjust menu
VIEW
°F
1 2
DHW
Boiler
Delay
Demand
Demand
Interstage
®
C
US
PC702-1
158033
Do not apply power
Signal wiring
3
4
5
6
7
must be rated
Made in
Stage
Com Sup Out
at least 300V
Canada
2
2
Outdoor
Temperature
Drop
102-106
EFFECTIVE: March 1, 2004
Control Adjustments
Troubleshooting
. . . . . . . pg. 7
Error Messages. . . . . . . . . . . pg. 8
Technical Data . . . . . . . . . . . pg. 8
To Taco
Zone
Control
Input
OutdoorSensor
Included
Input
Boiler Sensor
Included
Constant
Room Temperature
. . . . pg. 6
Heat
Loss
Increase
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Table of Contents
Related Manuals for Taco PC702–1
Summary of Contents for Taco PC702–1
- Page 1 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...
-
Page 2: Boiler Operation
Reset Ratio Operation of a hot water heating system can generally be improved by modulating the (99) Design supply water temperature as the outdoor temperature changes. Using this approach, the Conditions (88) heat lost from the building is matched by the heat input to the building. The PC702-1 Boiler Reset Control utilizes a reset ratio to set the relationship between outdoor temperature (77) and supply water temperature. - Page 3 When the outdoor temperature rises above the WWSD setting, the PC702-1 displays the WWSD segment in the LCD and turns off the boiler(s). If the PC702-1 receives a boiler demand from the Taco Zone Control while in a WWSD, the boiler(s) remain off. If the PC702-1 receives a DHW demand while in a WWSD, the boiler(s) are fired to satisfy the DHW demand.
-
Page 4: Installation
• Grasp the front cover by the fingertip grips on the top and bottom of the enclosure and pull the front cover off. Remove the wiring cover screw. • The enclosure is mounted onto a 2” x 4” electrical box near the Taco Zone Control. - Page 5 DHW demand wires (black wires) coming from the back of the control. This can To DHW Pump be achieved by wiring these two wires in parallel to the DHW (priority) zone on the Taco Zone Control. Settings Before adjusting the settings, read through the sequence of operation to ensure that you understand how the control operates. The following page describes how to program these settings into the control once it has been powered up.
-
Page 6: Control Adjustments
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) •... -
Page 7: View Menu
POWER UP VIEW MENU On power up, the Outdoor OUTDR DSGN DIFF VIEW ADJUST OUTDR VIEW control displays all Temperature BOIL TARGET °F °F Boiler Target segments for 2 °C VIEW The OUTDR element Temperature BOIL TARGET seconds and the °F WWSD is turned on. -
Page 8: Error Messages
, to test Demand: 20 to 260 V (ac) 2 VA condensing. Press & Release: Jul 00 Power supply — Class 2, 24 V ±10% 50/60 Hz 3 VA (Powered by Taco -Exp 31000265 Item + to adjust menu Control) OUTDR VIEW Relays —...