Application manual
KNX room temperature controller EK-EQ2-TP
Release 3.00 - Updating: 27/06/2017
Application Manual
© SBS S.p.A. - All rights reserved
Page 83
Cooling type
=
floor radiant panels
or
ceiling radiant panels
it is possible to select the position of the
hysteresis according to the second method described, i.e. with
upper
hysteresis for heating and
lower
hysteresis for cooling.
The desired temperature (T
set
) is usually different for each of the four operating modes and for the two
seasonal modes of the device. Values are defined for the first time during the configuration with ETS and can
be changed later. To maximize energy savings (for every extra degree of temperature, heat loss to the
outside and energy consumption increase of about 6%), you can easily take advantage of the multi-
functionality of the home automation system, for example with:
•
hourly programming with automatic switching of the operating mode by a KNX device with supervisor
function;
•
automatic switching of the operating mode depending on the presence of people in the room;
•
automatic switching of the operating mode at the opening of windows for air circulation;
•
stop of the circulating pump when thermostats are satisfied;
•
reduction of the flow temperature in partial load conditions.
9.1.1.2
Continuous Proportional-Integral control
The Proportional-Integral control (PI) is described by the following relation:
𝑐𝑜𝑛𝑡𝑟𝑜𝑙 𝑣𝑎𝑟𝑖𝑎𝑏𝑙𝑒(𝑡) = 𝐾𝑝 × 𝑒𝑟𝑟𝑜𝑟(𝑡) + 𝐾𝑖 × ∫ 𝑒𝑟𝑟𝑜𝑟(𝜏)𝑑𝜏
𝑡
0
where:
𝑒𝑟𝑟𝑜𝑟(𝑡) = (𝑆𝑒𝑡𝑝𝑜𝑖𝑛𝑡 − 𝑀𝑒𝑎𝑠𝑢𝑟𝑒𝑑 𝑡𝑒𝑚𝑝𝑒𝑟𝑎𝑡𝑢𝑟𝑒) 𝑖𝑛 ℎ𝑒𝑎𝑡𝑖𝑛𝑔
𝑒𝑟𝑟𝑜𝑟(𝑡) = (𝑀𝑒𝑎𝑠𝑢𝑟𝑒𝑑 𝑡𝑒𝑚𝑝𝑒𝑟𝑎𝑡𝑢𝑟𝑒 − 𝑆𝑒𝑡𝑝𝑜𝑖𝑛𝑡) 𝑖𝑛 𝑐𝑜𝑜𝑙𝑖𝑛𝑔
𝐾𝑝 = 𝑝𝑟𝑜𝑝𝑜𝑟𝑡𝑖𝑜𝑛𝑎𝑙 𝑐𝑜𝑛𝑠𝑡𝑎𝑛𝑡
𝐾𝑖 = 𝑖𝑛𝑡𝑒𝑔𝑟𝑎𝑙 𝑐𝑜𝑛𝑠𝑡𝑎𝑛𝑡
The control variable is composed of a part that depends proportionally from the error and a part that depends
on the integral of the error.
In practice derived values with a more intuitive meaning are used.
𝑃𝑟𝑜𝑝𝑜𝑟𝑡𝑖𝑜𝑛𝑎𝑙 𝑏𝑎𝑛𝑑 𝐵𝑃 [𝐾] =
100
𝐾𝑝
𝐼𝑛𝑡𝑒𝑔𝑟𝑎𝑙 𝑡𝑖𝑚𝑒 𝑇𝑖 [𝑚𝑖𝑛] =
𝐾𝑝
𝐾𝑖
The proportional band is the error value which determines the maximum excursion output at 100%.
For example, a regulator with proportional band of 5 K provides a 100% control output when the Setpoint = 20°C and the measured
temperature is ≤ 15°C in heating; in the cooling conduction mode, it provides a 100% control output when the Setpoint = 24°C and
the measured temperature is ≥ 29°C. As shown in the figure, a regulator with a small proportional band tends to provide higher
values of the control variable for small errors than a regulator with a higher proportional band.