- Data Brochure D 374 Universal Reset Control 374 03/09 The tekmar Universal Reset Control 374 is designed to maximize the comfort and efficiency provided by a hydronic heating system. The control automatically adjusts the boiler and mix water temperatures that are delivered to the heating system by using outdoor reset. The 374 can control two separate on / off stages (or one low / high fire) to provide outdoor reset while providing equal run time rotation of the boilers.
How To Use The Data Brochure This brochure is organized into four main sections. They are: 1) Sequence of Operation, 2) Installation, 3) Control Settings, and 4) Testing and Troubleshooting. The Sequence of Operation section has five sub-sections. We recommend reading Section A: General of the Sequence of Operation, as this contains important information on the overall operation of the control. Then read the sub sections that apply to your installation.
Display Number Field Displays the current value of the selected item Menu Field Displays the current menu Boiler Demand Mix 1 Demand Mix 2 Demand DHW Demand Setpoint Demand Item Field Displays an abbreviated name of the selected item Time & Date Field Displays days and AM or PM Status Field Displays the current status of the control's inputs, outputs and operation Buttons Selects Menus, Items and adjust settings Symbol Description Open / Close Displays when the actuator is opening or closing the mixi
Sequence of Operation Section A General Operation Page 4 - 6 Section B Boiler Reset Page 6 - 9 Section C DHW Operation Page 10 - 12 Section D Section E Setpoint Operation Page 12 Mixing Operation Page 13 - 15 Section A: General Operation POWERING UP THE CONTROL When the 374 control is powered up, all segments in the LCD are turned on for 2 seconds. Next, the control displays the control type number in the LCD for 2 seconds. Next, the software version is displayed for 2 seconds.
Low Mass Radiant (2) This type of radiant heating system is either attached to the bottom of a wood sub-floor, suspended in the joist space, or sandwiched between the sub-floor and the surface. This type of radiant system has a relatively low thermal mass and responds faster than a high mass system. Fancoil (3) A fancoil terminal unit or Air Handling Unit (AHU) consists of a hydronic heating coil and either a fan or blower.
EXERCISING The control has a built-in exercising feature, which ensures that each pump or valve is operated at least once every 3 days. If a pump has not been operated at least once every 3 days, the control turns on the output for 10 seconds. This minimizes the possibility of the pump seizing during a long period of inactivity. While the control is exercising, the Test LED flashes quickly. Note: The exercising function does not work if power to the control or pumps is disconnected.
BOILER CHARACTERIZED HEATING CURVE 210 (99) Boiler Characterized Heating Curve BOIL DSGN BOIL MAX 190 (88) Boiler Design Temperature 170 (77) The boiler design supply temperature is the supply water temperature required to heat the building when the outdoor air temperature is as cold as the outdoor design temperature.
STAGING The control operates up to two on / off boiler stages (or one low / high fire) in order to provide the required supply temperature. After a stage is turned on in the firing sequence, the control waits for a minimum time delay. The minimum time delay is adjustable using the Stage Delay setting. After the Stage Delay has expired, the control examines the control error to determine when the next stage is to fire. The control error is determined using Proportional, Integral and Derivative (PID) logic.
Desired temperature 160°F (71°C) Differential 10°F (6°C) Boiler Off ture era ture rise 165°F (74°C) era mp Te fall An on / off heat source must be operated with a differential in order to prevent short cycling. With the control, either a fixed or an auto differential may be selected. The boiler differential is divided around the boiler target temperature. The stage contact closes when the supply water temperature is ½ of the differential setting below the boiler target temperature.
Section C: DHW Operation Section C1 Domestic Hot Water (DHW) Section C2 DHW with Low Temperature Boilers Section C1: Domestic Hot Water (DHW) DHW DEMAND A DHW Demand is required in order for the control to provide heat to the DHW system. A DHW aquastat or setpoint control is used as a switch in the DHW demand circuit.
DHW MODE 4 - DHW in Primary / Secondary with External Priority When a DHW Demand is present, the DHW Pmp / Vlv contact is closed and the primary pump is operated. Priority can only be obtained using external wiring on boiler zones. The mix system pumps continue to operate but the variable speed pumps(s) is shut off or the mixing valve(s) is closed. This allows DHW priority over the mix zones.
Section C2: DHW with Low Temperature Boilers If DHW is to be incorporated into a low temperature system such as a radiant heating system, a mixing device is often installed to isolate the high DHW supply temperature from the lower system temperature. If a mixing device is not installed, high temperature water could be supplied to the low temperature system while trying to satisfy the DHW demand. This may result in damage to the low temperature heating system.
BOILER TARGET DURING SETPOINT The boiler target temperature during a setpoint demand is increased to at least the Setpoint setting. This temperature is maintained as long as the control has a setpoint demand. SETPOINT MODES Mode 1 - Setpoint in Parallel Whenever a setpoint demand is present, the boiler(s) is operated to maintain the setpoint target. The primary pump does not turn on, but may operate based on either a Boiler Demand or a DHW Demand. Refer to sections B and C.
MIX 2 DEMAND The mix 2 demand allows the operation of the mixing 2 device to provide outdoor reset to the mix 2 supply loop or a mix 2 setpoint temperature can be set. A conventional thermostat system can be used for zoning from the mix 2 supply loop. A mix 2 demand is generated by applying a voltage between 24 and 230 V (ac) across the Mix2 Dem and Com Dem terminals (27 and 26). Once voltage is applied, the Mix 2 Demand pointer is displayed in the LCD.
MIXING TERMINAL UNITS When a terminal unit is selected, the control automatically loads the mixing design temperature, mixing maximum supply temperature, and mixing minimum supply temperature. The factory defaults are listed below. The factory defaults can be changed to better match the installed system. If a factory default has been changed, refer to section A to reload the factory defaults.
Installation CAUTION Improper installation and operation of this control could result in damage to the equipment and possibly even personal injury. It is your responsibility to ensure that this control is safely installed according to all applicable codes and standards. This electronic control is not intended for uses as a primary limit control. Other controls that are intended and certified as safety limits must be placed into the control circuit. Do not open the control.
Boiler Demand 30 31 To generate a Boiler Demand, a voltage between 24 V (ac) and 230 V (ac) must be applied across the Boil Dem and the Com Dem terminals (30 and 31). Caution: The same power supply must be used to power the Boiler Demand, DHW Demand and the Setpoint Demand circuits since they share the Com Dem terminal. Boil Com Dem Dem 24 to 230 V (ac) DHW Demand To generate a DHW Demand, a voltage between 24 V (ac) and 230 V (ac) must be applied across the DHW Dem and Com Dem terminals (29 and 31).
13 14 15 Mix 1 System Pump (Mix1 P2) Power N L Mix1 P2 The Mix1 P2 output terminal (13) is a powered output. When the relay in the control closes, 115 V (ac) is provided to the Mix1 P2 terminal (13) from the Power L terminal (14). To operate the mix 1 pump, connect one side of the mix 1 pump circuit to terminal 13 and the second side of the pump circuit to the neutral (Power N) side of the 115 V (ac) power supply.
DHW Pmp / Vlv Contact The DHW Pmp / Vlv terminals (19 and 20) are an isolated output. There is no power available on these terminals from the control. These terminals are to be used as a switch to either make or break power to the DHW pump or the DHW valve. Since this is an isolated contact, it may switch a voltage between 24 V (ac) and 230 V (ac). 19 20 DHW Pmp/Vlv 24 to 230 V (ac) M or Stage 1 / Boil Enable Contact The Stage 1 / Boil Enbl. terminals (21 and 22) are isolated outputs in the control.
6 7 Unoccupied Switch UnO Com Sw If an external timer (tekmar Timer 032) or switch is used, connect the two wires from the external switch to the UnO Sw and Com terminals (6 and 7). When these two terminals are shorted together, the control registers an unoccupied (UNOCC) signal. STEP FIVE —————— TESTING THE WIRING General Each terminal block must be unplugged from its header on the control before power is applied for testing. To remove the terminal block, pull straight down from the control.
DHW Demand If a DHW demand is used, measure the voltage between the DHW Dem and the Com Dem terminals (29 and 31). When the DHW demand device calls for heat, between 20 and 260 V (ac) should be measured at the terminals. When the DHW demand device is off, less than 5 V (ac) should be measured. 29 30 31 20 to 260 V (ac) Com DHW Boil Dem Dem Dem Setpoint Demand If a setpoint demand is used, measure the voltage between the Setp Dem and the Com Dem terminals (28 and 31).
Stage 2 / Setp Enable Contact 23 24 If an on / off boiler is connected to the Stage 2 / Setp Enbl. terminals (23 and 24), make sure power to the boiler circuit is off, and install a jumper between the terminals. When the boiler circuit is powered up, the boiler should fire. If the boiler does not turn on, refer to any installation or troubleshooting information supplied with the boiler.
Mix 2 If a floating action actuating motor circuit is connected to the Pwr Mix, Opn and Cls Var2 terminals (3, 4 and 5), make sure power to the motor circuit is off and install a jumper between the Pwr Mix and Opn terminals (3 and 4). When the circuit is powered up, the actuator should move in the opening direction. If it does not, check the wiring between the terminals and the actuating motor. Refer to any installation or troubleshooting information supplied with the motor.
Rotate / Off The Rotate / Off DIP switch selects whether or not the control is to provide Equal Run Time Rotation of the boiler stages. If the switch is set to Rotate, the stages will be rotated accordingly. If the switch is set to Off, the firing sequence is fixed starting with Stage 1 then Stage 2. Floating / Variable The Floating / Variable DIP switch selects whether the control is to operate the mixing devices using floating action actuating motors or variable speed injection pumps.
Display Se In ctio st n Ad alle v r View Menu (1 of 1) Description Range Outdoor Current outdoor air temperature as measured by the outdoor sensor. This item is only available when Mix 1 Mode is set to 1, Mix 2 Mode is set to 1 or the Boiler sensor Return / Supply DIP switch is set to Supply. -67 to 149°F (-55 to 65°C) E1 Mix 1 Supply Current mix 1 supply water temperature as measured by the mix 1 supply sensor. This item is only available when Mix 1 Mode is set to 1.
Display © 2009 Se c In tio st n Ad alle v r Adjust Menu (1 of 4) Description Range E1 Mix 1 Mode Selects the mode of operation for mixing device 1. 0 (off) 1 (reset) Default = 1 E1 Mix 1 Room Occupied The desired room air temperature during the occupied period for mix 1 zones. This item is only available when Mix 1 Mode is set to 1. 35 to 100°F (2 to 38°C) Default = 70°F (21°C) E1 Mix 1 Room Unoccupied The desired room air temperature during the unoccupied period for mix 1 zones.
Display Se c In tio st n Ad alle v r Adjust Menu (2 of 4) Description Range E1 Mix 2 Room Unoccupied The desired room air temperature during the unoccupied period for mix 2 zones. This item is only available when the Setback / Off DIP switch is set to Setback and when Mix 2 Mode is set to 1. 35 to 100°F (2 to 38°C) Default = 65°F (18°C) E1 Mix 2 Target The mix 2 setpoint temperature. This item is only available when Mix 2 Mode is set to 2.
Display © 2009 Se c In tio st n Ad alle v r Adjust Menu (3 of 4) Description Range A Boiler Terminal Unit The type of terminal units that are being used in boiler zones. This item is only available when the Boiler Sensor Return / Supply DIP switch is set to Supply. 1 (HRF1), 2 (HRF2), 3 (COIL), 4 (CONV), 5 (RAD), 6 (BASE) Default = 4 B1 Boiler Indoor The design indoor air temperature used in the heat loss calculation for the boiler zones.
Display Se c In tio st n Ad alle v r Adjust Menu (4 of 4) Description Selects the mode of Actual Setting 1 (parallel, no priority), 2 (parallel, priority), 3 (primary pump) Default = 1 D1 Setpoint Mode operation. D1 Setpoint Occupied The minimum target supply temperature when a setpoint demand is present during the Occupied period. This item is only available when the Boiler Sensor Return / Supply DIP switch is set to Supply.
Time Menu (1 of 1) Note: The Setback / Off DIP switch must be in the Setback position in order to have access to the TIME menu. SETTING THE TIME Step One Press and release the Menu button until the TIME menu is reached. Step Two Press the Item button. While the minutes are flashing, use the ▲ or ▼ button to set the proper minutes. Step Three Press and release the Item button. While the hours are flashing, use the ▲ or ▼ button to set the proper hour. Step Four Press and release the Item button.
Schedule Menu (1 of 1) Note: The Setback / Off DIP switch must be in the setback position in order to have access to the SCHEDULE menu. SETTING THE SCHEDULE A schedule allows the timer to automatically change between two preset events based on the time of day. The schedule divides the day into Occupied and UnOccupied periods. To set the time of day at which each period is to begin, use the following procedure.
Testing the Control The control has a built-in test routine that is used to test the main control functions. The control continually monitors the sensors and displays an error message whenever a fault is found. See the following pages for a list of the control’s error messages and possible causes. When the Test button is pressed, the Test light is turned on. The individual outputs and relays are tested in the following test sequence. TEST SEQUENCE Each step in the test sequence lasts 10 seconds.
Troubleshooting When troubleshooting any heating system, it is always a good idea to establish a set routine to follow. By following a consistent routine, many hours of potential headaches can be avoided. Below is an example of a sequence that can be used when diagnosing or troubleshooting problems in a hydronic heating system. Establish the Problem Establish the problem. Get as much information from the customer as possible about the problem.
Error Messages (1 of 2) The control was unable to read a piece of information stored in its memory. Because of this, the control was required to reload the factory settings into all of the items in the ADJUST menu. The control will stop operation until all of the items in the ADJUST menu of the control have been checked by the user or installer. Note: The Installer / Advanced DIP switch must be set to Advanced in order to clear the error.
Error Messages (2 of 2) The control is no longer able to read the boiler sensor due to an open circuit. When there is a demand, the control will not control the boiler(s), but will provide a boiler enable to the boiler’s aquastat or boiler control until the sensor is repaired. The control will not operate the boiler contact if the Boil Minimum setting is less than 100°F (38°C). Locate and repair the problem as described in the Data Brochure D 070.
Technical Data Universal Reset Control 374 Two Mixing, Two Stage Boiler, DHW, & Setpoint Power supply Relays Var. Pump Demand Sensors included: – – – – – Optional Devices – D 374, A 374’s, D 070, D 001, E 021 Microprocessor PID control; This is not a safety (limit) control. 3.5 lb.
