tekmar 352 User Manual
- Data Brochure
Constant
Room Temperature
Outdoor
Temperature
Drop
Heat
Loss
Increase
House Control 352
UnOcc.
Heat
Demand
WWSD
Min. Boiler /
Max. Supply
Pump
Heat
House Control 352
One Zone, Boiler /
Injection
Power
The House Control 352 is a microprocessor-based outdoor reset control designed to control the
temperature of a single zone hydronic heating system. The 352 regulates the supply water
temperature based on the outdoor air temperature and optionally the indoor air temperature. The
352 can either operate a boiler and a system pump, or an injection valve and a system pump. To
avoid boiler short cycling and large temperature swings, the 352 has a built in function which continuously adjusts the boiler differential.
The 352 includes features such as Warm Weather Shut Down (WWSD), system pump exercising,
Night Setback (UnOccupied period), minimum boiler supply temperature setting (Boiler mode) and
maximum supply water temperature setting (Injection mode). A Room Temperature Unit (RTU) 054 or
an Indoor Sensor 076 can be connected to the 352 to provide indoor temperature feedback.
Control Strategy . . . . . . . . . . . . pg. 1 Testing the Control . . . . . . . pg. 7
Sequence of Operation . . . . . . . pg. 3 Error Messages. . . . . . . . . . . pg. 7
Installation . . . . . . . . . . . . . . . . . pg. 4 Technical Data . . . . . . . . . . . pg. 8
Settings . . . . . . . . . . . . . . . . . . . pg. 6 Limited Warranty . . . . . . . . . pg. 8
Output
System Pump
(through back of control)
H11191
105 Off
Min. Boiler /
Max. Supply
House Control 352
One Zone, Boiler /
Injection
Power
140°F
Made in Canada by
tekmar Control
Systems Ltd.
170
Heat
Demand
0.2
Heating Curve
Pump
1
UnOcc.
WWSD
Min. Boiler /
Max. Supply
Heat
D 352
06/00
2
3
3.6
Aug 95
31000265
NRTL/C
Heat4Heat
LR 58223
UnOccupied
Signal wiring
must be rated
at least 300V
Input
24 V (ac)
Power Supply
M
or
Output
Boiler or Valve
Input
tekmar
Timer
Power:
24 V 50/60 Hz 3 VA
Relays:
120 V (ac) 10 A 1/3 hp
pilot duty 240 VA
1C2R3
Boiler / Injection
Power Relay
TIME
1
PRGM
AMPM
2
UNOCC
OVR
S
SMWTFT
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
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 the outdoor temperature drops, the building heat loss increases.
1 of 8
R
70°F (21°C)
40 (4) 100 (38)
Do not apply power
5
RTU
UnO
Sen
Sw
Test
Input
Outdoor Sensor
6
7
8
9
Com
Sup
Out
Sen
Sen
Sen
Included
Input
Supply Sensor
Included
70
Input
tekmar RTU or
Indoor Sensor
Copyright © D 352 - 06/00
Heating Curve
Supply Water Temperature
Time
Differential = 10°F (5°C
)
165°F(74°C)
B
o
i
l
e
r
o
f
f
B
o
i
l
e
r
o
n
155°F (68°C)
160°F (71°C)
B
o
i
l
e
r
o
f
f
B
o
i
l
e
r
o
n
Mixing
Device
Boiler
Loop
System
Loop
A hot water heating system can be accurately controlled by modulating the supply water
temperature as the outdoor temperature changes. Using this approach the heat lost from
the building is exactly matched by the heat input to the building. A tekmar reset control
utilizes a heating curve to set the relationship between outdoor temperature and supply
water temperature. The heating curve determines the amount the supply water temperature is raised for every 1° drop in outdoor air temperature. The heating curve is sometimes
called an outdoor reset ratio.
Heating Curve Parallel Shift
All heating curves begin at the heating curve starting point. If the heating curve starting
point is adjusted, the heating curve will be parallel shifted. The heating curve starting point
is either set manually through a dial, or it is determined automatically by the control
through indoor temperature feedback.
Indoor Temperature Feedback
Most buildings have internal heat gains due to people, passive solar heating and
mechanical or electrical equipment. If only the outdoor temperature is measured, the
control cannot compensate for these internal heat gains and the building may overheat.
In order to prevent overheating, indoor temperature feedback should be combined with
the outdoor reset strategy. From this indoor temperature feedback, the control can
change the heating curve starting point in order to match the supply water temperature
to the heat loss of the building. If the indoor temperature is too warm, the control
automatically shifts the starting point and the heating curve down. If the indoor temperature is too cold, the control shifts the starting point and heating curve up.
Warm Weather Shut Down (WWSD)
When the outdoor temperature is equal to the heating curve starting point, no additional
heat is required in the building and therefore the heating system can be shut down. The
WWSD point is normally the same as the heating curve starting point.
BOILER OPERATION
The supply water temperature from a boiler can be controlled by cycling the boiler on and
off. Modulation of the boiler’s operating temperature in hot water heating systems not only
provides more comfort but also offers significant energy savings. The cooler the boiler runs,
the more efficient it is due to less heat losses up the flue and reduced boiler jacket losses.
Minimum Boiler Supply
Most boilers require a minimum supply water temperature in order to prevent corrosion
from flue gas condensation. The control should therefore only modulate the boiler supply
water temperature down to the boiler manufacturer’s minimum recommended operating
temperature. Some boilers are designed to condense and should be operated
water temperatures as much as possible for maximum efficiency.
at low
Heating
Curve
Starting
Point
70
90
(21)
(32)
70
90
(21)
(32)
Minimum Boiler
Supply Setting
WWSD
Point
70°F
70
90
(21)
(32)
3.0
3.6
2.4 2.0
50
(10)30(-1)10(-12)
Outdoor air temperature
3.0
3.6
2.4
Parallel Shift of Heating Curve
UP
DOWN
50
(10)30(-1)10(-12)
Outdoor air temperature
3.0
3.6
2.4
130°F
50
(10)30(-1)10(-12)
Outdoor air temperature
210
(99)
1.6
190
(88)
170
1.2
(77)
150
1.0
(65)
0.8
130
(54)
0.6
11 0
(43)
0.4
0.2
-10
(-23)
2.0
1.6
1.2
1.0
0.8
0.6
0.4
0.2
-10
(-23)
2.0
1.6
1.2
1.0
0.8
0.6
0.4
0.2
-10
(-23)
Supply water temperature
90
(32)
70
(21)
°F
(°C)
210
(99)
190
(88)
170
(77)
150
(65)
130
(54)
11 0
(43)
Supply water temperature
90
(32)
70
(21)
°
F
°C)
(
210
(99)
190
(88)
170
(77)
150
(65)
130
(54)
11 0
(43)
Supply water temperature
90
(32)
70
(21)
°F
(°C)
Boiler 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
water temperature swings; however, if the differential is too narrow, the
boiler short cycles and operates inefficiently. Some controls automatically calculate the boiler differential in order to achieve an appropriate
balance between temperature swings and boiler efficiency. This also
permits the control to adapt to changing loads and conditions.
MIXING OPERATION
The full range of water temperatures required through a heating season
can be provided with a standard (non-condensing) boiler by incorporating a mixing device into the system. An On / Off Injection Valve or Pump
can be used to modulate the system supply water temperature to
improve comfort in the building and provide a maximum target supply
water temperature limit. For more detailed information on mixing methods consult Essay E 021.
Copyright © D 352 - 06/00
2 of 8
Maximum System Supply
Jumper
6
Sen
RTU
7
Sen
Com
8
Sen
Sup
9
Sen
Out
Do not apply power
Some systems, such as hydronic radiant floor heating, usually operate at water temperatures that are below
the minimum boiler supply temperature. This is due to the large surface area of the floors which radiate a
significant amount of heat at low water temperatures. Floor heating systems and flat panel convectors also
have a maximum surface temperature limit for occupant health reasons. In such systems a mixing device
is normally required to limit the supply water temperature.
UNOCCUPIED (NIGHT SETBACK)
During the night, or at times when people are not within the building, energy can be saved by lowering the
building temperature for an UnOccupied (Night Setback) period.
Sequence of Operation
Mix
POWERING UP THE CONTROL
WARM WEATHER SHUT DOWN (WWSD)
BOILER OPERATION
MIXING OPERATION
After the 352 is powered up a certain combination of red LEDs are turned on for 2 seconds
indicating the software version. All red LEDs are then held on for 4 seconds. When the
control is powered up, the green
Power
light remains on continuously.
When the outdoor temperature rises above the heating curve starting point, the 352 turns
WWSD
the
If the control is in
light on and shuts down the system pump and the
Boiler
mode and the jumper is cut, the control ignores the WWSD feature
Heat
relay.
and keeps the boiler warm.
If the DIP switch is set to
the boiler on and off. The 352 calculates the target supply water temperature based on the
outdoor temperature and optionally the indoor air temperature. In order to prevent boiler
short cycling, the 352 has a minimum time delay of 30 seconds before turning the boiler on
or off. The 352 calculates the boiler differential automatically. The
whenever the boiler is on.
Maximum Boiler Supply
The 352 does not allow the target boiler supply water temperature to exceed 212°F
(100°C). If the supply water temperature approaches 212°F (100°C), the 352 turns off
the boiler.
Minimum Boiler Supply
The 352 has a
order to prevent corrosion from flue gas condensation. This dial has an
condensing and electric boilers. If an RTU or Indoor Sensor is connected to the 352 and
the required system supply temperature needs to be lower than the
setting, the 352 turns on the boiler until the minimum boiler temperature is reached. It then
keeps the boiler off for a calculated off time in order to prevent overheating of the zone.
The
Heat Demand
Boiler
, the system supply water temperature is controlled by turning
Min. Boiler
dial which sets a minimum target boiler supply temperature in
light turns on when operation of the boiler is required.
Heat
light turns on
Off
position for
Min. Boiler
dial
If the DIP switch is set to
is controlled by turning an injection device, such as a zone valve, on and
off. The 352 calculates the target supply water temperature based on the
outdoor temperature and optionally the indoor air temperature. To
prevent short cycling of the valve, the 352 uses a minimum time delay of
30 seconds. The
If the jumper beside the outdoor sensor terminal is cut, the control will
ensure the injection device and system pump are turned on for at least
17 minutes every 7 days. This flushing function prevents bacteria growth
in applications where a water heater is used for DHW and heating.
Boiler Control
During mixing operation the boiler can be enabled using the end switch of the zone valve.
The boiler aquastat should be set at least 20°F (11°C) above the system design water
temperature.
Maximum System Supply
The 352 has a
water temperature. If the system supply temperature approaches the
setting, the 352 turns on the
Max. Supply
Injection
Heat Demand
dial that can be used to set an upper limit to the system supply
, the system supply water temperature
light turns on when heat is required.
Max. Supply
light and closes the injection valve.
3 of 8
Max. Supply
dial
Minimum Boiler
Supply Setting
WWSD
Point
70°F
90
(32)
WWSD
Point
70°F
90
(21)
(32)
24 V (ac)
Temperature 212°F
130°F
50
70
(10)30(-1)10(-12)
(21)
Outdoor air temperature
M
3.6
Maximum
Temperature
(set on dial)
50
70
(10)30(-1)10(-12)
Outdoor air temperature
Copyright © D 352 - 06/00
Maximum Boiler
3.0
3.6
2.4
3.0
2.4
Supply
UnOcc.
WWSD
House Control 352
One Zone, Boiler /
Min. Boiler /
Injection
Max. Supply
Heat
Demand
Power
Pump
Heat
WWSD
230
(110)
210
2.0
(-23)
2.0
-10
(-23)
(99)
1.6
190
(88)
170
1.2
(77)
150
1.0
(65)
0.8
130
(54)
0.6
11 0
(43)
0.4
0.2
-10
1.6
1.2
1.0
0.8
0.6
0.4
0.2
90
(32)
70
(21)
°
F
°C)
(
210
(99)
190
(88)
170
(77)
150
(65)
130
(54)
11 0
(43)
Supply water temperature
90
(32)
70
(21)
°F
(°C)
Supply water temperature
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