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, W
arm 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
1
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
2
3
®
Signal wiring
must be rated
at least 300V
Made in
Canada
PC702-1
4
5
67
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
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