tekmar 374 Universal Reset Control User Manual

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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.

It is assumed that the Setpoint pump will provide adequate flow through the heat exchanger and the boiler.

Mode 2 - Setpoint in Parallel with Priority

Whenever a setpoint demand is present, the boiler(s) is operated to
maintain the setpoint target and the primary pump (

Prim P1) contact

is opened.

It is assumed that the Setpoint pump will provide adequate flow
through the heat exchanger and the boiler.

Mode 3 – Primary Pump during Setpoint

Whenever a setpoint demand is present, the primary pump (

Prim P1) is

turned on and the boiler(s) is operated to maintain the setpoint target.

SETPOINT PRIORITY OVERRIDE

The setpoint has a

Priority Override while in SETP MODE 2. In order to prevent the building from cooling off too much or the

possibility of a potential freeze up during setpoint priority, the control limits the amount of time for setpoint priority. As the outdoor air
temperature becomes colder, the length of time the control provides setpoint priority is reduced. Once the allowed time for priority
has elapsed, the control overrides the setpoint priority and operates setpoint and heating simultaneously by turning on the primary
pump (

Prim P1).

CONDITIONAL SETPOINT PRIORITY

If the boiler(s) supply temperature is maintained at or above the required temperature during setpoint generation, this indicates that
the boiler(s) has enough capacity for setpoint and possibly heating as well. As long as the boiler target temperature is maintained,
setpoint and heating occur at the same time.

GENERAL

The control is capable of providing either two reset supply temperatures or one reset supply temperature and one mix setpoint
temperature using two mixing devices. Each mixing device reduces the supply water temperature from the primary boiler loop to
a secondary mixed loop. Each mixed secondary loop has its own supply water target temperature, which is determined by its own
Mixing Characterized Heating Curve or Mix Target setpoint temperature.

MIX 1 DEMAND

The mix 1 demand allows the operation of the mixing 1 device to provide outdoor reset to
the mix 1 supply loop. A conventional thermostat system can be used for zoning from the
mix 1 supply loop. A mix 1 demand is generated by applying a voltage between 24 and
230 V (ac) across the

Mix1 Dem and Com Dem terminals (25 and 26). Once voltage is

applied, the

Mix 1 Demand pointer is displayed in the LCD. If the control is not in WWSD, it

will operate the mix 1 device and the mix 1 system pump (

Mix1 P2) to maintain the mixing 1

target temperature.

Setpoint Pump

Primary

Pump

Primary

Pump

Setpoint Valve

25 26

Mix1

Dem

Com

Dem

24 to 230 V (ac)

Section E1

Mixing

Section E: Mixing Operation

Section E1: Mixing