Domestic hot water (dhw) & setpoint – tekmar 363 Universal Reset Control Installation User Manual

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Section C1 —Domestic Hot Water (DHW)

DHW DEMAND

DHW demand is generated on the 363 by one of two methods: either an external DHW demand from an aquastat or an internal demand

from a tekmar sensor.

External Demand (10K 2 = NONE)

The 363 registers an external demand for DHW when a voltage between 24 and 240 V (ac)
is applied across the

Setp/DHW and the Com Dem terminals (5 and 3). Either a DHW

aquastat or setpoint control is used as a switch in the DHW demand circuit. Once the 363
detects a DHW demand, the

DHW Demand pointer turns on in the LCD and the control

operates as described below.

Internal Demand Sensor (10K 2 = DHW)

If the 10K 2 setting is selected as DHW, the 363 looks for a DHW sensor connected to the
10K 2 and the Com Sen terminals (18 and 17). The DHW TANK setting is used to set the
desired indirect DHW tank temperature.
When the temperature at the DHW sensor drops 3˚F (1.5˚C) below the DHW TANK setting,
the

DHW Demand pointer turns on in the LCD and the control operates as described below.

An advantage to using the DHW sensor is that the control can display the current DHW TANK
temperature and record the highest and lowest DHW TANK temperatures. Also, the 363 can
control the DHW temperature with more accuracy than when using an aquastat.

DHW DEVICE (DHW THRU)

Once the 363 has received a

DHW demand, the sequence of operation depends on the type

of DHW device selected. The DHW device is selected using the DHW THRU item in the

Adjust

menu.

DHW Valve (VALV)

If VALV is selected as the DHW device and there is a

DHW demand, the 363 closes the DHW

Pmp / Vlv contact (9 and 10) and the Boil P1 contact (7 and 8). The boiler pump provides
flow through the DHW tank’s heat exchanger once the DHW valve is opened. The 363
operates the boiler to provide a sufficient boiler supply temperature to the DHW tank.

DHW Pump (PUMP)

If PUMP is selected as the DHW device, the 363 assumes that the DHW pump provides
adequate flow through both the DHW tank heat exchanger and the boiler. To provide heat
to the DHW tank, the 363 closes the

DHW Pmp / Vlv contact (9 and 10) and operates the

boiler to provide a sufficient Boil SUP temperature to the DHW tank. If using a primary loop
with the DHW tank piped in primary / secondary, select DHW VALV.

BOILER TARGET DURING DHW GENERATION (Boil 0TRG)

The Boil TRG temperature during DHW operation depends on whether an external or internal demand is occurring. The DHW demand
overrides the reset water temperature.

External Demand (10K 2 = NONE)

If the control receives a

DHW demand through an external device such as an aquastat, the Boil TRG temperature is at least as hot

as the DHW Heat Exchanger setting (DHW XCHG).

Internal Demand (10K 2 = DHW)

If the control receives a

DHW demand from a DHW sensor attached to the 10K 2 and the Com Sen terminals (18 and 17), the Boil

TRG

temperature is at least as hot as the DHW TANK setting plus 40˚F (22˚C).

DHW DURING UNOCCUPIED

The DHW operation during an

UnOccupied period depends on the type of DHW demand that the 363 is receiving and the type of setback

that is being used. For this function to operate, the control must have the

Setback / None DIP switch set to Setback.

Section C1

Domestic Hot
Water (DHW)

Section C2

DHW Priority

Section C3

DHW with Low

Temperature

Boilers

Section C4

Setpoint

Section C —Domestic Hot Water (DHW) and Setpoint

24 to 240 V (ac)

Com

Dem

Boil

Dem

Setp/

DHW

Aquastat

Com 10K

DHW

Storage Tank

Pump

Valve