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3

Heating Curve

To calculate the correct setting for the

design supply temperature –WWSD temperature

Heating Curve, use the following formula:

WWSD temperature – design outdoor temperature

For example: •  design outdoor temperature = 5

°

F (-15

°

C)

•  WWSD temperature = 70

°

F (21

°

C)

Heating Curve  =

  =

=   1.4

•  design supply temperature = 160

°

F (71

°

C)

If the system design supply water temperature is unknown, a trial setting can be calculated using these typical supply temperatures:
• Fan coils or convectors  …180 to 210

°

F (82 to 99

°

C)    • Hydronic radiant floors …100 to 130

°

F (38

°

to 54

°

C).

Warm Weather Shut Down (WWSD)

The WWSD  can be adjusted from 35 to 105

°

F (2 to 41

°

C) and its function is covered under the Outdoor Reset Strategy section on page 2.

If the DIP switch is selected for one boiler operation, the pump output will cycle on for 20 seconds every three days during WWSD

.

Minimum Boiler Operating Temperature

This adjustment should be set according to the requirements specified by the boiler
manufacturer.  Many boilers require a minimum operating temperature to prevent
corrosion from flue gas condensation.  The control raises the supply temperature to the
Minimum when the outdoor temperature drops below the WWSD setting, and holds it
there until the outdoor temperature becomes cold enough to require operation on the
heating curve.
Typical Minimum Boiler Operating Temperatures:  • Steel Tube Boilers …140

°

 to 180

°

F (60

°

to 82

°

C) • Cast Iron Boilers …130 to 150

°

F (54 to 66

°

C) • Copper Tube Boilers …105 to 150

°

F

(41 to 66

°

C) • Condensing or Electric Boilers …off

Settings

Desired temperature
this example
160

°

F(71

°

C)

T

emperature

W

armer

Cooler

Time

Differential

this example 

10

°

F(5

°

C)

165

°

F(74

°

C)

155

°

F(68

°

C)

Te

m

p

e

ra

tu

re

 fa

ll

BOILER

OFF             ON

Te

m

p

e

ra

tu

re

 r

is

e

Heating Curve  =

Outdoor air  temperature

Supply water temperature

50

(10)

30

(-1)

10

(-12)

-10

°

F

(-23)

°

C

110
(43)

70

(21)

70

(21)

90

(32)

210
(99)

170 
(77)

150 
(65)

130 
(54)

190
(88)

3.6 3.0 2.4 2.0

0.8

0.4

1.0

0.6

90

(32)

50

°

F

(10)

°

C

Heating

Curve

1.2

Minimum Supply

Setting 130

°

F

WWSD

Point

70

°

F

1.6

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

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

When the control is 
powered-up, all display 
elements are turned on. 
After approximately 3 
seconds, the control 
automatically goes into 
operating mode.

POWER ON

PROGRAMMING

Push     or     to change 

minumum boiler staging 

delay

Push     or     to

change Heating Curve

(underscore is decimal point)

When in operating mode, 
the Outdoor temperature 
will be displayed. Boiler(s) 
output is on when number 
segment is on. When 
number is flashing, delay 
on is occuring. 

Item

VIEWING 

Press and Release  the 
"Item" button.  The 
programmed Differential 
setting will be displayed.

Item

Press and Release  the 
"Item" button.  The 
programmed Warm 
Weather Shut Down 
setting will be displayed.

Item

Item

Press and Release  the 
"Item" button.  The Target  
Supply temperature will be 
displayed.

Press and  Release  the 
"Item" button.  The 
programmed Minimum 
supply temperature setting 
will be displayed. A fast 
flashing pointer indicates 
programming is active.

Item

Press and  Release  the 
"Item" button.  The 
programmed Heating 
Curve setting will be 
displayed. 

Push     or     to select between

Fahrenheit or Celsius scales

Press and  Release  the 
"Item" button.  The 
Fahrenheit or Celsius 
scale may be selected.

Item

Press and  Release  the 
"Item" button.  Only with two 
boiler option will the minimum 
boiler staging delay be 
displayed. 

Push     or     to

change Differential 

Push     or     to

change WWSD setting

Min.

Outdoor

Supply
Target Supply

Curve

WWSD

Differential

Min.

Outdoor
Supply

Target Supply

Curve

WWSD

Differential

Min.

Outdoor
Supply
Target Supply

Curve

WWSD

Differential

Min.

Outdoor
Supply
Target Supply

Curve

WWSD

Differential

Min.

Supply
Outdoor
Target Supply

Curve

WWSD

Differential

Min.

Outdoor
Supply
Target Supply

Curve

WWSD

Differential

Min.

Supply
Outdoor
Target Supply

Curve

WWSD

Differential

Min.

Supply
Outdoor
Target Supply

Curve

WWSD

Differential

Min.

Outdoor
Supply
Target Supply

Curve

WWSD

Differential

Item

F

1

PRGM

F

PRGM

F

Min.

Outdoor

Supply

Target Supply

Curve

WWSD

Differential

When only one boiler is 
selected, the Pump output 
contact will be on 
continuously until WWSD 
occurs. A slow flashing 
pointer indicates control 
action.

F

1

Press and  Release  the 
"Item" button.  The Supply 
temperature will be 
displayed.

Item

Push     or     to

change Minimum supply 

temperature 

PRGM

PRGM

PRGM

F

PRGM

The display defaults to 
outdoor temperature after 
power up, or if the control 
has been left alone in 
programming longer than 
20 seconds. 

Item

Min.

Outdoor

Supply
Target Supply

F

1

Curve

WWSD

Differential

Min.

F

1

Curve

WWSD

Differential

Outdoor

Supply
Target Supply

F

1
2

PRGM

F C

1
2

F

=    10

°

F (6

°

C)

Differential and Time Delay

The differential adjustment sets how far the actual supply water temperature may deviate
from the desired temperature before a boiler is turned on or off, and is determined by the
flow rate through the system pump relative to the amount of heat produced.  When using
two boilers, boiler # 2 will be staged on when the actual supply temperature drops below
the control's calculated target supply minus the differential setting.  Note:  Boiler # 2 delay
time must have expired before boiler # 2 is fired.  To prevent short boiler cycles, the
control has a minimum time delay of 30 seconds between firing cycles for the first boiler.
When two boiler operation is selected, the minimum delay between stages is adjustable
from 30 seconds to 4 minutes.
In the following example, boiler # 1 will turn on when the actual temperature falls 5

°

F

(3

°

C) below the desired temperature and will turn off when the actual temperature rises

5

°

F (3

°

C) above the desired temperature

.

100,000 Btu/hr

20 US GPM x 500

=

Differential =

Btu/hr of each stage

System US GPM x 500

90

°

F

65

°

F

160

°

F - 70

°

F

70

°

F - 5

°

F

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