12
RESET RATIO
Set Point Operation:
r
e
S
e
t
ratio
(
rSt
) has no effect.
Reset Operation:
The
r
e
S
e
t
ratio
(
rSt
) determines how the Secondary loop
water temperature will vary with outside temperature. With
any ratio, the colder it is outside, the hotter the tempera-
ture of the Secondary loop. At a 1:1 reset ratio (Curve 7) a
1 degree drop in outdoor temperature will increase the
Secondary loop temperature by 1 degree; at the 3:1 ratio
(Curve 3) an outdoor temperature drop of 3 degrees will
increase the Secondary loop temperature by 1 degree.
The ratios are adjustable from 8:1 (Curve 1) for the least
amount of heat to 1:4 (Curve 12) for the most amount of
heat (see side chart). With most baseboard heating
applications, a 1:1 (Curve 7) setting is a good place to start.
Radiant heat applications usually require a lower curve.
Adjust the
r
e
S
e
t
ratio
in cold weather. If the ambient
space temperatures are too cold in cold weather, increase
the curve number by one. If the space temperatures are
too warm in cold weather, decrease the curve number by
one. After making a change to the ratio, wait 24 hours to
evaluate the impact of the change. See chart pg. 10 to
adjust the
r
e
S
e
t
ratio
OFFSET
Set Point Operation:
OFF
set
(
OFF
) has no effect.
Reset Operation:
The
OFF
set
(
OFF
) allows you to adjust the starting points
of the Reset Ratio curves (see side charts). When the
OFF
set
is changed, that change is always directly added
or subtracted to the calculated water temperature. For
instance, if the calculated Secondary loop water tempera-
ture were 130°F and the
OFF
set
were changed from 0° to
10° (an increase of 10°), then the calculated water tempera-
ture would immediately change to 140°F.
Adjust the
OFF
set
in mild weather. If the ambient space
temperatures are warm in mild weather, decrease the
OFF
set
. If the space temperatures are cold in the mild
weather, increase the
OFF
set
. The rule of thumb for
baseboard radiation is to change the
OFF
set
by 4° for
every degree you wish to change the space temperatures.
For radiant heat applications, change the
OFF
set
by 1° or
2° for every degree you wish to change the space tempera-
ture. See chart on 10 to adjust the
OFF
set.
Outdoor T emperature
W
a
te
r
T
e
m
p
e
ra
tu
re
70
40
50
60
130
120
110
100
11
2
7
Outdoor T emperature
W
a
te
r
T
e
m
p
e
ra
tu
re
70
40
50
60
110
100
90
80
11
2
7
Outdoor T emperature
W
a
te
r
T
e
m
p
e
ra
tu
re
70
40
50
60
150
140
130
120
11
2
7
0° Offset
The ratios begin
at 100° Water
Temperature.
-20° Offset
The ratios begin
at 80° Water
Temperature.
+20° Offset
The ratios begin
at 120° Water
Temperature.
Offset Examples
Outdoor Temperature (in °F)
70
60
50
40
20
30
0
-10
10
-20
W
a
te
r
T
e
m
p
e
ra
tu
re
(
in
°
F
)
100
120
110
130
140
150
160
180
170
190
200
210
220
12 11
10
9
8
7
6
4
3
2
5
1
1:4 1:3
1:2
1:1.5
1:1.25
1:1
1.25:1
1.5:1
2:1
3:1
4:1
8:1
Reset Ratio Curves
Ratios represent Outdoor:Water