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
S
UPERSEDES : 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
Taco
Zone
Control
Item
1
H1
192A
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
6
7
Com Sup Out
Do not apply power
Rotation On / Of
f
Boiler
Demand
DHW
Demand
Interstage
Delay
Start
Stage
1 1
Stage
2 2
Input
OutdoorSensor
Included
Input
Boiler Sensor
Included
DHW
Demand
C
US
158033
Output
Boiler
Output
Boiler
OUTDR
°
F
1 2
VIEW
PC702
Item
®
C
US
158033
OUTDR
°
F
VIEW
1 2
Boiler
Demand
DHW
Demand
Interstage
Delay
Start
