Carrier WEATHERMAKER 48J Started Manual page 43

Single package large rooftop units with comfortlink ti version 5.x controls sizes (020-060)
Table of Contents

Advertisement

5.
then Lo Cool Mode mechanical
stages = 2 and Hi Cool
Mode mechanical
stages = 2.
If the economizer
position is greater than (bnfiguration
-+ECON-+ECMX-
5% for more than 8 minutes
but
less than 11.5 minutes and mechanical
cooling has started
then:
Lo Cool Mode mechanical
stages = 2
Hi Cool Mode mechanical
stages = 3
6. If the economizer
position is greater than (bnfiguration
-sECON-sEC.MX-
5% for more than 11.5 minutes and
mechanical
cooling has started then:
Lo Cool Mode mechanical
stages = 2
Hi Cool Mode mechanical
stages = 3 (for 020 to 027
units only)
Hi Cool Mode mechanical
stages = 4 (for 030 to 060
units only)
NOTE:
If some compressors
are not available
due to being
faulted, the Hi Cool Mode number of compressors
are affected
before the Lo Cool Mode number of compressors.
For exam-
STAGE
ple, if a 4 compressor
unit has one compressor
faulted, and the
economizer
is not active,
then
an HVAC
mode
Hi Cool
requested
number
of compressors
is changed from 4 to 3. If
Y1
another
compressor
faults, then both Lo Cool and Hi Cool
Y2
requested
number
of compressors
are set to 2. In addition,
COMP
compressors
cannot
be brought
on faster
than one
every
A1
30 seconds. If the control needs to bring on 2 compressors
at
A2
once, the first compressor
will come on followed by the second
B1
compressor
30 seconds later.
UNIT
Staging of compressors
is shown in Tables 49-60.
020
EDT Low Override -- There is an override if EDT drops too
025
low based on an alert lhnit that will lock out cooling. If the
027
supply air/evaporator
discharge temperature
(EDT) falls below
the alert limit ((bnfiguration---)ALLM--+SA.L.O)
cooling will
be inhibited.
There is a 20-minute
hold off on starting cooling
again once the following
statement is true: EDT minus (Run
Status _COOL--sSUMZ--sADD.R)
has risen above SA.L.O.
The variable ADD.R
is one of the SumZ cooling algofithin
STAGE
control variables dedicated mainly for multi-stage
control.
2-Stage (_ntlvl
and the Economizer
-- The 2-stage logic will
first check for the availability of the economizer.
If free cooling
Y1
can be used, then the control will first attempt to use the free
Y2
cooling.
COMP
If no mechanical
cooling is active, and the economizer
is
A1
active, the economizer
will first attempt to control to a cooling
A2
control point of either the supply air set point high (SA.H1) or
B1
supply
air set point
low (SA.LO)
plus
any reset
applied,
B2
depending
on whether High Cool or Low Cool mode is in ef-
UNIT
fect, respectively.
030
If one stage of mechanical
cooling is on, and the economiz-
035,036
er is active, then the economizer
will attempt to control to 53 E
040,041
Also If HVAC mode = LOW
COOL,
the second
stage of
050
mechanical
cooling will be locked out.
051,060
If the set point cannot be satisfied or the economizer
is not
active, then cooling will be brought
on one stage at a time
when the evaporator
discharge
temperature
(EDT)
is greater
the 1.5 ° F above the current cooling control point. A start-up
time delay of 10 minutes
and steady state delay after a com-
pressor is energized of 5 minutes is enforced.
If both circuits of mechanical
cooling are running, then the
economizer
will attempt to control to 48 E If the economizer
is
active and the outside-air
temperature
(OAT) is less than the
cooling control point + 0.5 F, the compressors
will be locked
off. When mechanical
cooling is on, the control may also use
the economizer
to trim the leaving-air
temperature
to prevent
unnecessary
cycles of the compressor
stages.
See the Economizer
Integration
with Mechanical
Cooling
section for more information
on the holding off of mechanical
cooling as well as the economizer
control point.
Table 49 -- 2-Stage Sequence --
48/50AJ,AW020-027
SEQUENCE 1
o l
i
I 2
Thermostat Inputs
OPEN CLOSED I CLOSED
I
OPEN
OPEN
CLOSED
Compressor Status
OFF
ON
ON
OFF
OFF
ON
OFF
OFF
ON
Unit Capacity
0%
67%
100%
0%
65%
100%
0%
67%
100%
SEQUENCE 2
01
1 I
2
Thermostat Inputs
OPEN CLOSED CLOSED
OPEN
OPEN
CLOSED
Compressor Status
OFF
OFF
ON
OFF
ON
ON
OFF
OFF
ON
Unit Capacity
0%
67%
100%
0%
65%
100%
0%
67%
100%
Table 50 -- 2-Stage Sequence --
48/50AJ,AW030-060
SEQUENCE 1
o l
i
I 2
Thermostat Inputs
OPEN CLOSED I CLOSED
I
OPEN
OPEN
CLOSED
Compressor Status
OFF
ON
ON
OFF
ON
ON
OFF
OFF
ON
OFF
OFF
ON
Unit Capacity
0%
45%
100%
0%
48%
100%
0%
43%
100%
0%
45%
100%
0%
50%
100%
SEQUENCE 2
01
1 I
2
Thermostat Inputs
OPEN l CLOSED CLOSED
OPEN[ OPEN
CLOSED
Compressor Status
OFF
ON
ON
OFF
ON
ON
OFF
OFF
ON
OFF
OFF
ON
Unit Capacity
0%
45%
100%
0%
48%
100%
0%
43%
100%
0%
45%
100%
0%
50%
100%
Table 51 -- Staging Sequence Without Hot Gas Bypass --
48/50AK,AY020-027
and Multi-Stage 48/50AJ,AW020-027
SEQUENCE
1
SEQUENCE
2
STAGE
0
1
2
3
4
0
1
2
3
4
COMP
Compressor
Status
Compressor
Status
A1
OFF
ON
ON
OFF
ON
OFF
OFF
ON
ON
ON
A2
OFF
OFF
ON
ON
ON
OFF
ON
ON
OFF
ON
B1
OFF
OFF
OFF
ON
ON
OFF
OFF
OFF
ON
ON
UNIT
Unit Capacity
48/50A
Unit Capacity
48/50A
020
0%
33%
67%
67%
100%
0%
33%
67%
67%
100%
025
0%
30%
65%
70%
100%
0%
35%
65%
65%
100%
027
0%
33%
67%
67%
100%
0%
33%
67%
67%
100%
43

Hide quick links:

Advertisement

Table of Contents
loading

Table of Contents