System Design Guide; Designing Of Water Circuit System - Mitsubishi Electric CITY MULTI PQRY-P72-336ZLMU-A1 Data Book

8. SYSTEM DESIGN GUIDE

8-1. Designing of water circuit system

8. SYSTEM DESIGN GUIDE
1) Example of basic water circuit
The water circuit of the water heat source CITY MULTI connects the heat source unit with the cooling tower/auxiliary
heat source/heat storage tank/circulation pump with a single system water piping as shown in the figure below. The
selector valve automatically controls to circulate water toward the cooling tower in the cooling season, while toward
the heat storage tank in the heating season. If the inlet water temperature is kept in a range of 10~45°C [50~113°F]*
regardless of the building load, the water heat source CITY MULTI can be operated for either cooling or heating.
Therefore in the summer when only cooling load exists, the temperature rise of circulation water will be suppressed
by operating the cooling tower. While in the winter when heating load increases, the inlet temperature of circulation
water may be dropped below 10°C [50°F]. Under such situation, the circulation water will be heated with the
auxiliary heat source if it drops below a certain temperature.
When the thermal balance between cooling and heating operation is in a correct proportion, the operation of the
auxiliary heat source and cooling tower is not required.
In order to control the above thermal balance properly and use thermal energy effectively, utilizing of heat storage
tanks, and night-time discounted electric power as a auxiliary heat source will be economical.
Meantime as this system uses plural sets of heat source unit equipped with water heat exchangers, water quality
control is important. Therefore, a cooling tower should be a closed type that water is not exposed to the atmo-
sphere.
Example of basic water circuit for water heat source CITY MULTI
The indoor unit and refrigerant piping system are excluded in this figure.
MEES21K047
E.H
S.T
P T
3-way valve
C.T
C.T.P
T
S.T : Heating tank
(Heat storage tank)
C.T : Cooling tower
C.T.P : Cooling water pump
P : Circulation water pump
T : Thermostat for water
E.H : Electric heater
: Heat source unit for cooling
operation
: Heat source unit for heating
operation
WR2-Series-575V
65