Trane RTHD Troubleshooting Manual page 21

T e m p e ra tu re
( F )
0
1 5 0
1 4 0
P anic Fa n A dd Line : If C ond enser P re ssu re /T e m pe rature rises above th is line ,
o ne add ition al fan w ill be a dd ed e ach 5 secon ds ittera tion .
1 3 0
1 2 0
1 1 0
4.5 F D ea db an d
1 0 0
9 0
8 0
7 0
A r
6 0
5 0
4 0
3 0
2 0
1 0
0
0 5 1 0
Figure 11. Condenser Fan Control
RLC-SVD05A-EN
Variable Speed Fan Control - RTAC Only
R T A C C o n d e n s e r F a n C o n tro l
m
A D T
1
G D T
1
D elta P
S etp oin t
6 0 P sid
A D T = A nticip ated D elta T
(A sym ptote of C on de nser T em p
rela tive to O utdoor A ir Tem p)
1 5 2 0
The fan state is a function of the ambient temperature as sensed by the ambient
temperature sensor at startup, times an additional scaling factor that is a function
of the lower of either the leaving water temperature or the outdoor air
temperature at startup, divided by how many compressors there are per circuit.
The maximum number of fixed speed fans that are started are just equal to or
less than the Initial Fan Capacity Function per
available it will be started along with the necessary number of fixed speed fans to
exactly match the requirement.
In normal fan control, a new % fan capacity will be calculated at each iteration per
the fan control algorithm. The algorithm attempts to control the fans so that the
condenser pressure is held to within a 4.5 F deadband above the condenser goal
pressure which is set relative to the current Evaporator Pressure (i.e. 60 PSID
above it).
If variable speed fans are present, then the air flow is modulated directly on the
Desired New % Air Flow calculated every 5 seconds.
When only fixed speed fans are present, additional fans will not be staged on
until the new % Air Flow exceeds the next available fan step.
P red icte d A sym ptote o f C ond ense r T em perature/P ressure
A D T
3
A D T
2
G D T
G D T
3
2
A s G D T ap pro ach es zero an d go es ne ga tive,
ne w % a irflow w ill be clam ped a t 1 0x prese nt a irflow
G D T = G o al D elta T
(G oa l to O u tdo or Air Tem p)
2 5 3 0 3 5
Figure
4 0
11. If a variable speed fan is
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