Satchwell IAC 600, Manual

Page: 16 / 24

Fig.2
PRESET 2 – 2 Boiler Sequence Control (compensated) with a separate HWS System
Time re-synchronization
Pumps failed signal
Clear pumps failed
Pump 1
Pump 2
Boiler
1
High Limit Thermostat
(hand reset) and burner
controls.
*
Flow
Boiler
2
Pumps Failed
Pump 2
Pump 1
Boiler 2
HWS
Valve
Backend Valve 2
Supply
Backend Valve 1
HWS Sensor
Outside Sensor
Flow Sensor
Pump
Clear Pumps Failed
Connect to any IAC
isolated ground
terminal
Connect to any IAC 600
terminal
Note:–
The actual terminal block is a
double block running across
the bottom of the IAC. The
top (double height) block
contains terminals 1 to 33 and
the bottom (single height)
contains 34 to 41 and all of
the Ground and isolated
Ground terminals. Terminal
numbers run from left to right.
6
Ensure Terminal 2 is
earthed.
66
The 24Vac Supply must
be fused with a 2A fuse.
Terminal 5 is not used.
If an earth busbar is to be
used then it must be
connected to a single Ground
terminal on the IAC by a
single cable which should be
as short as possible and no
more than 150mm long. Earth
wire minimum 30/0.25
(1.5mm
2
) Stranded Cable.
Any IAC 600
terminal
HWS
Valve
Boiler 1
Time re-synchronization
TIME SCHEDULES
08:00 to 17:00
Connected to the compensator and HWS loops.
The time re-synchronization input will re-synchronize the IAC time to
midnight Monday.
COMPENSATOR
Schedule
OUTSIDE SUPPLY
0 80
10 50
20 20
The outside temperature value is fed into a look-up table. The result
is passed to the controller RPW input and is used to set the controller
set value.
Proportional Band
10
Integral Action 300
Derivative Action 0
Ramp Time 60
Sample Time 10
BOILER/BACKEND VALVE
The lead boiler backend valve is always held open with the other one
being enabled on demand. The lead boiler rotates every 100 hours.
The lead boiler is enabled when the control demand signal exceeds
33% with the second boiler and backend valve being enabled a 66%.
There is a 5% hysteresis on both steps. The call for heat signal from
the HWS is linked to the lead boiler to ensure that the boiler fires if
HWS is required under low load conditions.
PUMPS
Two pump outputs are supplied, Pump 1 normally runs when the
controller is requesting heat. In the event of pump 1 failing to run a
differential pressure switch signals the IAC which enables pump 2.
In the event of pump 2 failing the "pumps failed" outputs is enabled.
A "clear pumps failed" input is supplied to enable the failed pumps to
be used once they have been repaired or reset.
VALVE OPTIONS
Both the HWS and backend valve actuators may be 0 to 10Vdc or
24Vac driven, it should be noted however that valve operation in all
cases is purely on/off and not modulating.
DS 2.951A 16 - 24 05/98