Lochinvar MP2 Bedienungsanleitung PDF herunterladen (Seite 14)

NUMBER OF BOILERS USED FOR DHW GENERATION

The number of boilers used for DHW generation can be

selected from one to the maximum number of boilers using

the BOIL DHW setting. This applies when only a DHW

Demand is present. If there are other demands present, the

control does not limit the number of boilers operated.

SECTION E2: 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. The control is capable of providing DHW in

such a system while maximizing the chance that the tem-

perature in the heating system does not exceed its allowed

maximum setting.

To prevent high temperature water from being introduced

into the heating system, the primary pump (Prim P1) must

be turned off during a call for DHW. To do this, the control

must be set to DHW MODE 2 or DHW MODE 4 and Boil

MIN must be set to OFF, see Figure 22 below.

DHW MODE 2 OPERATION

On a call for DHW, the control provides DHW priority by

shutting off the primary pump (Prim P1) for a period of time.

This time is based on the DHW Priority Override setting.

However, if the DHW Demand is not satisfied within the

allotted time, the boiler(s) shuts off and the heat of the

boiler is purged into the DHW tank.

Once the boiler supply temperature is sufficiently reduced,

the Relay 9 / DHW contact shuts off. The heating system is

turned on for a period of time to prevent the building from

cooling off. After a period of heating, and if the DHW

Demand is still present, the control shuts off the heating sys-

tem and provides heat to the DHW tank once again.

For correct operation, close attention must be paid to the

mechanical layout of the system. When the control turns off

the primary pump (Prim P1), flow to the heating system

must stop. If flow is not stopped, the temperature in the

heating system can exceed the maximum desired tempera-

ture and can result in damage to the heating system.

DHW MODE 4 OPERATION

In DHW MODE 4, the space heating zones must be pre-

vented from coming on during DHW demands using exter-

nal wiring. This can be done using an external relay to

remove power from zone pumps or zone valves while a

DHW Demand is present. During a DHW Demand, the con-

trol closes the primary pump (Prim P1) contact and the

Relay 9 / DHW contact. Once the DHW Demand is

removed, or during a DHW Priority Override, the Relay 9 /

DHW contact is opened, and the external wiring should

allow the space heating zones to operate.

There is no mixing purge available in DHW MODE 4. After

DHW priority, the boiler supply water temperature may

exceed the design water temperature of the space heating

system and can result in damage to the heating system.

SECTION F: SET POINT OPERATION

SECTION F1: SET POINT

Set point operation is only available when DHW MODE is

set to OFF.

SET POINT

The control can operate to satisfy the requirements of a set

point load in addition to a space heating load. A set point

load overrides the current outdoor reset temperature and

WWSD setting in order to provide heat to the set point load.

SET POINT DEMAND

A set point demand is required for the control to provide

heat to the set point load. The control registers a set point

demand when a voltage between 24 and 230 V (ac) is

applied across the Setp / DHW and Com Dem terminals (8

and 7) (FIG. 23).

Once voltage is applied, the Set Point Demand pointer turns

on in the LCD. The control operates the boiler(s) to main-

tain at least the set point setting.

FIG. 22

FIG. 23

1 2 ... 9 10 11 12 13 14 15 16 17 18 19 ... 35 36

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