Fault Detection and Diagnostics for Rooftop Air Conditioners

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1.2.5 Summary of Decoupling Schemes for Rooftop Unit System Faults
So far, couplings among component-level faults, among system-level faults, and
from system-level to component-level faults have been broken fully or unilaterally.
Figure 1-17 summarizes the decoupling scheme for component and system level faults.
Equation (1-23) formulates the decoupling scheme and results of all the rooftop faults. It
can be seen that the matrix L of equation (1-23) is sparse and lower triangular. The
algorithm described in section 3.1.2.3 can solve this unilateral decoupled problem.
Component-Level Faults
NonCond
CondFoul
CompLeak
EvapFoul
LL-Restr
COMP-OFF
CONDENSER
COMP-ON
COMPRESSOR
EVAPORATOR
LIQUID-LINE
∆ T cond
∆ m&
ca
∆ T dis
∆ m&
ea
2
∆ P ll
System-Level Faults
RefUnder
RefLeak
RefOver
OR Low
Charge
XOR
Wrong
Charge
RTU
SYSTEM
System State
Residuals (SSR)
Or
∆T
= T −T
sh − sc
sh
sc
Figure 1-17 The Decoupling Scheme of All Rooftop System Faults
⎡ ∆T
⎢
⎢
∆T
2
⎢ ∆ P
⎢
⎢ ∆m&
⎢ ∆m&
⎢
⎢⎣
SSR / T
sat
dis
ll
ca
ea
sh−sc
⎤
⎥
⎥
⎥
⎥
⎥
⎥
⎥
⎥⎦
= Z
= LX
⎡l
⎢
⎢
⎢
= ⎢
⎢
⎢
⎢
⎢⎣
l
11
61
l
l
l
l
l
22
32
42
52
62
l
l
33
63
l
l
44
64
l
l
55
65
l
66
⎤⎡
NonCond ⎤
⎥⎢
⎥
⎥⎢
CompLeak
⎥
⎥⎢
LLRestr ⎥
⎥⎢
⎥
⎥⎢
CondFoul ⎥
⎥⎢
EvapFoul ⎥
⎥⎢
⎥
⎥⎦
⎢⎣
RefCharge⎥⎦
(1-23).
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