MEES22K030
QAHV-N-TAU-HPB, YAU-HPB
37
4. System Design
4-2. QAHV Secondary side control
4-2-1. General description and purpose of secondary side control
Secondary side control is a control method to raise the hot water temperature in the tank by using another heat exchanger
added between the tank and the existing heat exchanger.
By incorporating the secondary side control to the QAHV, the need to assemble a pump control on-site is eliminated, and
the system construction in cases where water exceeding the QAHV water quality standard is used is now easier.
(1) System diagram
System overview
The system using the secondary side control is roughly split into the following three elements: [1] Unit heating circuit, [2]
Secondary side circuit, and [3] Hot water supply circuit. The hot water heated in the unit heating circuit [1] and the cold
water from the lower section of the tank are heat-exchanged in the secondary side circuit [2], and then the high-tempera-
ture water flows into the hot water storage tank. The heated hot water in the hot water storage tank is supplied to the
customer via the hot water supply circuit [3].
Control target
Based on the data of the flow rate sensor and temperature thermistor installed on the secondary side, the output of
secondary side pump is adjusted by QAHV (adjusts by 0-10 V output).
Purpose
Adjusting the pump output on the secondary side maintains the target outlet hot water temp. and prevents acute rising
of water inlet temp. to QAHV.
Overview on pump operation in different operation modes (○: operated, ×: stopped)
(2) Difference between systems with and without secondary side control
T
Temperature sensor
[2] Secondary side circuit [3] Hot water supply circuit[1] Unit heating circuit
Secondary side control system
Flow sensor
Operation modes Primary side Secondary side
Hot water storage mode
○ ○
Defrost operation mode
× ×
Anti freezing operation
○ ○
At the end of hot water storage mode, before and after defrost operation (*)
○ ○
Without secondary side control
Diagram
Unit Tank Unit
Secondary side
heat exchanger
Tank
Water quality standard
&DOFLXPKDUGQHVVPJ&D&2Ɛ
S+RUOHVV
S+RUOHVV
8QLW&)
6HFRQGDU\VLGH&)
8QLWVHFRQGDU\VLGHSXPSDQG
secondary side flow adjusting device
&)
Unit
RUOHVV
+RWZDWHUVXSSO\WHPSHUDWXUHUDQJH
Control target
With secondary side control
0000006864.BOOK 37 ページ ２０２２年８月２５日 木曜日 午後３時５８分
To Next Page
Loading...
Need help?
General
