114
• Control systems
• intelligent Touch Manager • ED721208
Explanations of Power Proportional Distribution
What is the Power Proportional Distribution (PPD)
(System Ex. : Normal VRV)
iTM
• Previously the general way for requesting the electricity charge at tenant buildings was that a management staff read a watthour
meter and billed the tenants by manual-account based on the operation time which were counted through time-counters.
However, this method takes a lot of time for the management staff. In addition, as air-conditioning consumes much different electricity
for either the operation of air-conditioning (thermostat-ON) or the operation of fan only (thermostat-OFF), it might cause to give unfair
sense to the tenants inhabited in the spaces with different heat load, though “operation-time” itself is the same.
For instance, even if a certain higher set temperature is applied in summer for energy saving, fee for air-conditioning may equal to
the fee without set temperature so far as it is counted based on the operation time.
• Electric energy distributing function of iTM carries out the proportional division computation in consideration of those thermostat-ON
and thermostat-OFF operations and saves time for building management staffs to read watthour meters, and also supplies tenants
printed data useful for making the bills.
Namely, iTM is the product created by the concept to help the assignment of bill-issuing and offers users the reasonable price of the
products.
• Yet, since the iTM is constantly assuming each indoor unit’s power consumption based on the data which is transferred from indoor
units, it should be noticed that the iTM is not which complies with the Weight and Measure Act as shown in the catalogue.
The details of the cause to count error is described at chapter 1.3.2.
(1) Count method (for a conventional VRV system)
1) The following proportional division calculation is carried out every one hour and assigns the power consumption of air-conditioning
system to each indoor unit.
Heat load depending on the operation conditions of air-conditioner = power consumption of indoor unit’s fan
+ power consumption of optional heater
+ the rated power consumption in cooling (*1) ×a
+ the rated power consumption in heating (*1) ×b
Watthour meter
with output
Power supply
single phase
Outdoor unit
Indoor units: a maximum of 64 units
Since this system detects power consumption as the base of billing, specified
watthour meters should be used by all means
Power supply
3 phase
10
10
a = (a1+a2ðT) ð
b = (b1-b2ðT) ð
Thermo.-step (*2)
Thermo.-step (*2)
Power consumption (kWh)
(Ttconstant)
a1, a2: correction factor for cooling
b1, b2: correction factor for heating
T: indoor unit’s suction air temperature
Indoor units N’s power consumption (kWh) = total pulse input from wattmeters x
Thermo-step
Heat load by one hour calculated through the
operating of air-conditioner N
*1: The value which is registered at the test
operation, adapting the indoor unit’s capacity
*2: “Thermo.-step” signifies that an air-conditioning
capacity is expressed in a range of the values
0-5 mainly based on the opening grade of an
electronic expansion valve in an indoor unit.
As shown in the left, heat load is calculated
from an equation of the first degree which
approximates the correlation, among thermostep,
indoor unit’s suction air temperature and power
consumption, into the lineair line under the
standard conditions of the unit.
total heat load by one hour calculated
through the operating conditions of all the
air-conditioners
Summary of Contents for brp069a42
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