tekmar 371 House Control User Manual
Page 15
15
Boiler Minimum Supply
Most boilers require a minimum operating temperature to prevent corrosion from flue gas condensation. The
Min. Boiler Supply dial should be set to the lowest supply water temperature at which the boiler can operate
without causing the boiler flue gases to condense. Consult the boiler manufacturer for recommended boiler
minimum supply temperatures. Some typical settings are given below. If a condensing or electric boiler is
used, the
Min. Boiler Supply dial is normally set to Off.
Typical settings:
• Steel fire tube boilers . . . . . . 140 to 160
°
F (60 to 71
°
C)
• Cast iron boilers . . . . . . . . . . 135 to 160
°
F (57 to 71
°
C)
• Copper tube boilers . . . . . . . 135 to 150
°
F (57 to 66
°
C)
System Maximum Supply
The 371 seeks to prevent the mixed supply water temperature from rising above the
Max. Supply dial setting.
The
Max. Supply dial should be set to the maximum temperature allowed in the mixing loop. There are many
factors which may limit the allowable supply temperature in a radiant floor heating slab. A few of these are
provided below.
• Some tubing manufacturers recommend that their products not be maintained at temperatures exceeding
140
°
F (60
°
C). Consult the tubing manufacturer for specific details.
• Nowhere in the concrete should the temperature be maintained above 170
°
F (77
°
C).
• The surface temperature of a radiant floor heating slab should normally not exceed 85
°
F (29
°
C). The slab
surface temperature is affected by the supply water temperature to the slab as well as the slab thermal
resistance and heating load.
Setpoint Temperature
If the
Setpnt DIP switch is set to Mixing and a Setpoint Demand is provided, the 371 increases the mixed
supply water temperature to the
Setpnt dial setting. The Setpnt dial should be set to the required setpoint
temperature or to the maximum supply temperature allowed by the system.
Unoccupied Temperature
The
UnOccupied dial sets the desired indoor temperature during UnOccupied (Night Setback) mode. When
a Zone Control is used, the zones connected to the Zone Control are not affected by the
UnOccupied dial
on the 371. The Zone Control has its own UnOccupied mode which is explained in more detail in the Data
Brochure supplied with the Zone Control.
Heating Curves
The 371 House Control has two independent Heating Curve dials; one for the boiler loop
(
Boiler Heating Curve) and one for the mixing loop (Heating Curve). The Heating Curve
dial settings determine the number of degrees the supply water temperature is raised for
every one degree drop in outdoor temperature. The
Heating Curve dial positions can be
calculated from the following formula. Normally the two Heating Curves are different values.
design supply temperature – design room temperature
Heating Curve =
design room temperature – design outdoor temperature
Example: A system is designed to supply 120
°
F (49
°
C) mixed water and 180
°
F (82
°
C)
boiler water when the outdoor temperature is 10
°
F (-12
°
C) and the room
temperature is 70
°
F (21
°
C).
120 - 70
°
F (49 - 21
°
C)
50
°
F (28
°
C)
Heating Curve
=
=
= 0.8
70 - 10
°
F (21 - (-12)
°
C)
60
°
F (16
°
C)
180 - 70
°
F (82 - 21
°
C)
110
°
F (43
°
C)
Boiler Heating Curve
=
=
= 1.8
70 - 10
°
F (21 - (-12)
°
C)
60
°
F (16
°
C)
If the design supply water temperature is unknown, the
Heating Curve dial can be set to
a trial value calculated from the typical design supply water temperatures given below.
• Hydronic radiant floors …......100 to 130
°
F (38 to 54
°
C)
• Baseboard radiators …..........160 to 190
°
F (71 to 88
°
C)
• Fan coils …............................180 to 210
°
F (82 to 99
°
C)
70
°
F
(21
°
C)
40
(4)
100
(38)
UnOccupied
Max. Supply
/ Setpnt
120
170
°
F
220
Max. Supply
/ Setpnt
120
170
°
F
220
130
°
F
Off
165
Min. Boiler
Supply
100
Outdoor air temperature
50
(10)
30
(-1)
10
(-12)
-10
(-23)
70
(21)
3.6 3.0 2.4 2.0
1.6
1.2
0.8
0.4
1.0
0.6
90
(32)
WWSD
Point
°
F
(
°
C)
Supply water temperature
110
(43)
70
(21)
90
(32)
210
(99)
170
(77)
150
(65)
130
(54)
190
(88)
0.2
0.2
2
3.6
1
3
Boiler
Heating Curve
0.2
2
3.6
1
3
Heating Curve