Taco PC702–1 Instruction Sheet Download Page 6

6 of 8 

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  ….............  125 to 150

°

F (52 to 66

°

C) 

Differential (DIFF)

 

The differential adjustment sets how far the actual boiler supply water temperature may deviate from the desired temperature before 
the boiler is turned on or off, and it is determined by the flow rate through the system pump relative to the heat output by the boiler. 
The differential can be adjusted to Ad (Auto differential) or from 2 to 42

°

F (1 to 23

°

C). The following formula can be used to calculate 

the desired differential: 

When the adjustment is set to 

Ad (Auto Differential

), the differential is continuously calculated by the control, and varies as the heating 

load changes. 

Interstage Delay

 

The interstage delay setting is used to set the minimum time delay between the first stage firing and the second stage firing, and is 
adjustable from 30 seconds to 4 minutes. 

Warm Weather Shut Down (WWSD)

 

The WWSD can be adjusted from 35 to 100

°

F (2 to 38

°

C). The boiler will be shut down when the outdoor temperature is warmer than 

this setting. If the WWSD is set to OFF, the control continues to provide a minimum boiler temperature even during warm outdoor 
temperatures. 

Control Adjustments

Boiler Start: ______________________________________ 

Boiler Minimum: _______________________________ 

Outdoor Start: ____________________________________ 

Differential: __________________________________ 

Boiler Design: ____________________________________ 

Interstage Delay: ______________________________ 

Outdoor Design: __________________________________ 

WWSD: ______________________________________ 

Differential

 

=

 

Example:

 

=

 

10

°

F (6

°

C)

 

Btu/hr input

 

100,000 Btu/hr

 

System US GPM x 500

 

20 US GPM x 500

 

ADJUST MENU

To enter the adjustment mode, 

Press

 and 

Hold

 simultaneously, the 

Item

,   and   Buttons. The 

ADJUST

 element will turn on.

Start

Interstage

Delay

DHW

Demand

Boiler

Demand

BOIL

°

F

ADJUST

Start

Interstage

Delay

DHW

Demand

Boiler

Demand

DSGN

OUTDR

°

F

ADJUST

Start

Interstage

Delay

DHW

Demand

Boiler

Demand

min

ADJUST

Start

Interstage

Delay

DHW

Demand

Boiler

Demand

OUTDR

°

F

ADJUST

Start

Interstage

Delay

DHW

Demand

Boiler

Demand

BOIL

°

F

MIN

ADJUST

Start

Interstage

Delay

DHW

Demand

Boiler

Demand

WWSD

°

F

ADJUST

Start

Interstage

Delay

DHW

Demand

Boiler

Demand

DSGN

BOIL

°

F

ADJUST

Start

Interstage

Delay

DHW

Demand

Boiler

Demand

DIFF

ADJUST

Start

Interstage

Delay

DHW

Demand

Boiler

Demand

°

F

ADJUST

BOIL Start

Use the   and 
buttons to set the
desired boiler starting
tempeature.

OUTDR Start

Press and release
the 

Item

 button. Use

the   and   buttons
to set the desired
outdoor starting
tempeature.

BOIL DSGN

Press and release
the 

Item

 button. Use

the   and   buttons
to set the boiler
design tempeature.

OUTDR DSGN

Press and release
the 

Item

 button. Use

the   and   buttons
to set the outdoor
design tempeature.

BOIL MIN

Press and release
the 

Item

 button. Use

the   and   buttons
to set the boiler
minimum
tempeature.

DIFF

Press and release
the 

Item

 button. Use

the   and   buttons
to set the boiler
differential
tempeature.

Interstage Delay

Press and release
the 

Item

 button. Use

the   and   buttons
to set the desired
interstage delay time.

WWSD

Press and release
the 

Item

 button. Use

the   and   buttons
to set the desired
WWSD tempeature.

Units

Press and release
the 

Item

 button. Use

the   and   buttons
to select between 

°

F

and 

°

C

The control automatically goes back to viewing when the buttons are left alone for 20 seconds

All settings will be saved even during power down of the control

Summary of Contents for PC702–1

Page 1: ...portional to the temperature of the supplywaterandthesurfaceareaoftheheatingelement Asmallsurface 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 InstructionSheet PC702...

Page 2: ...iler jacket losses Differential An on off boiler must be operated with a differential in order to prevent short cycling When the supply water temperature drops below the bottom rail of the differential the boiler is turned on The boiler is then kept on until the supply water temperature rises above the top rail of the differential If the differential is too wide there can be large supply watertemp...

Page 3: ...iler setting This pro grammed function has an OFF setting for condensing and electric boilers When operating at the minimum setting the control displays the MIN segment in the LCD when either that boiler supply or boiler target temperature are being viewed ROTATION The PC702 1 has an optional boiler rotation function that is selected using the DIP switch located next to terminal 1 in the wiring ch...

Page 4: ...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 The sensor should be mounted on a wall which best repr...

Page 5: ... be adjusted from 35 to 150 F 2 to 66 C This setting is typically set to the desired building temperature In applications where fan coils are used the BOIL Start may need to be set higher to prevent cold drafts during mild outdoor conditions If the building feels cool during mild outdoor conditions the BOIL Start setting should be increased Outdoor Starting Temperature OUTDR Start The OUTDR Start ...

Page 6: ...esign __________________________________ WWSD ______________________________________ Differential Example 10 F 6 C Btu hr input 100 000 Btu hr System US GPM x 500 20 US GPM x 500 ADJUST MENU To enter the adjustment mode Press and Hold simultaneously the Item and Buttons The ADJUST element will turn on Start Interstage Delay DHW Demand Boiler Demand BOIL F ADJUST Start Interstage Delay DHW Demand B...

Page 7: ... not be connected to the control while the test is performed Using the chart below estimate the temperature measured by the sensor The sensor and thermometer readings should be close If the test meter reads a very high resistance there may be a broken wire a poor wiring connection or a defective sensor If the resistance is very low the wiring may be shorted theremaybemoistureinthesensororthesensor...

Page 8: ...or Design 60 to 32 F 51 to 0 C 10 F 12 C Boiler Minimum Off 80 to 180 F Off 27 to 82 C 140 F 60 C Differential Auto 2 to 42 F Auto 1 to 24 C Auto Interstage Delay 0 30 to 4 00 minutes 2 00 min WWSD 35 to 100 F Off 2 to 38 C Off 70 F 21 C Units F C F Do It Once Do It Right TACO INC 1160 Cranston Street Cranston RI 02920 Telephone 401 942 8000 FAX 401 942 2360 TACO Canada Ltd 6180 Ordan Drive Missis...

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