8
A 511 - DTC 628 Eng.
06.12.05 LB
We reserve the right to make changes without notice
▼
▼
Ta = 20
°
C
Tm
p
Tm
min
Te
p
90
Tm
max
80
70
60
50
40
30
20
15
10
5
0
-5
-10
-15
-20
te
Tm
▼
20
÷
40
°
C
▼
C
Ta –
Ta +
M6.
1
T y p e o f c o n t r o l
C O M P E N S - F I X E D P
M6.
1
T y p e o f c o n t r o l
C O M P E N S - F I X E D P
M6.
1
T y p e o f c o n t r o l
C O M P E N S - F I X E D P
13. OPERATION
DTC 628 is a microprocessor-based digital controller especially suitable for controlling the tempe-
rature of a boiler with modulating burner.
When the plant comprises several modulating boilers in parallel, each DTC 628 controls its own boiler
and related shut-off valve with autonomous timed event programmes and desired temperatures; this
permits flexible management of the boilers to meet plant requirements.
14. CONTROL OF BOILER TEMPERAURE
The control of the boiler temperature, monitored by detector B4, can be :
– COMPENSATED - FIXED POINT : Compensated or Fixed Point: the different control modes
are set by the desired temperatures used in setting the timed programs
(
M2.
) and in the choice of the program in use (
M0.
2
).
– Compensated : boiler temp. in relation to outside temperature;
use : – Room temp.: NORMAL 1...5,
SETBACK 1-2, FROSTPROT.
– Fixed Point
: boiler temp. at fixed value;
use : Boiler temp. : FIXED POINT 1-2.
– ZONES : boiler temp. in relation to temp. requested by zone controllers connected in C-Ring.
14.
1
Compensated
Compensated control can be used when:
– the boiler feeds a single heating circuit without it own control valve (see Example Plants
12.
1
).
– the boiler feeds one or more heating circuits with its own compensated controllers and has
to maintain a “basic” compensated temp. that will satisfy the demand of the controllers (see
Example Plants 12.
2
and 12.
3
).
For Compensated temperature control use:
– Room temp. NORMAL 1…5 set in
M1.
1…5
;
– Room temp. SETBACK 1-2 set in
M1.
6-7
;
– Room temp. FROSTPROT set in
M1.
8
;
The control calculates the desired flow temperature (
Tf
) in relation to the outside temperature (
to
)
measured by detector B2 (or coming via C-Ring) and from the
heating curve
, referred to a desired
room temperature of 20°C, set by means of:
• Type of heat emitters: - RADIATORS; - FAN COILS; - PANELS.
Establishes the slope of the heating curve in relation to the output curve of the heat emitters.
• Outside design temperature (
Tod
), used for calculating winter heat losses from building.
This depends on the climatic zone in which building situated.
• Design flow temperature (
Tfd
) , used for sizing the plant.
(eg: radiators = 70°C, fan coils = 80°C, panels = 40 °C)
• The origin of the heating curve (
C
) (flow temp. =
20 °C with outside temp.= + 20 °C) can be with
adjusted by an increase in the flow temperature
(0…40°C). This may be necessary to avoid
problems due to the reduced heating period
used in the intermediate seasons (mild outside
temperatures).
The value of the desired flow temperature (
Tf
) depends
on the value of the room temperature (
Tr
) desired by
the operating mode in use (parallel /- of the
curve), Room temp. set in
M1.
1…8
.
14.
2
Fixed Point
To have temperature control at Fixed Point use:
– Temp. boiler FIXED POINT 1-2 set in
M1.
9-10
;
The controller keeps the temperature constant at the desired value FIXED P 1 or FIXED P 2.
M4.
1
H e a t e m i t t e r s
R A D I A T O R S
M4.
2
D e s i g n o u t s i d e
t e m p : ± x x . x c
M4.
3
D e s i g n f l o w
t e m p : ± x x . x c
M4.
4
C u r v e O r i g i n T O 2 0
F l o w T : x x . x c