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HVAC - Air Conditioning / Heat Pumps - Lightning Claims

Bad Capacitor

Case History: This case exemplifies why insurance companies check for lightning damage. This four year old central air conditioning unit was replaced with a new one at cost of $1,600 to the insured. The air condition technician said that he believed that it was lightning damage because both the fan and the compressor went out at the same time. When the insurance adjuster asked the technician about the compressor, he said that it was shorted to ground, and when he attempted to start the unit, it just hummed. The adjuster also questioned the technician about the capacitor, and he stated, he check it. The insurance adjuster was smart enough to know that if the compressor had been shorted then when the technician attempted to start the unit, the circuit breaker should have tripped. The capacitor is actually two capacitors in one metallic can; one for the compressor and one for the fan. As depicted in the photographs, the capacitor was bulged, and it was the culprit. Furthermore, you cannot check the winding of the compressor to see if they are shorted to ground without first removing the bad capacitor. After replacing the capacitor, the unit ran flawlessly.

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Replaced AC Unit
This Unit Was Replaced at a Cost of $1600 to the Insured.
It took a $20 Capacitor to Fix the Unit (AC05-01).
Capacitor Can is Bulged at Top on Right Side
Capacitor Can is Bulged at Top on Right Side (AC05-01).
Capacitor Measurement
This Reading Should Have Been 35 uF - Instead, It Was 0.17 nF.
One (1) uF equals 1,000 nF (AC05-02)

Reciprocating Compressors

Reciprocating Compressor consist of a electric motor that drives a crankshaft piston.

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Central AirConditioner Recipicating Compressor-SM.jpg
Central Air Conditioner Compressor (AC05-02).
Bristol Compressor Tag
Bristol Compressor Tag (AC05-02).
Cut Bristol Recipocating Compressor
Cut Bristol Reciprocating Compressor (AC05-02).
Compressor Motor
Compressor Motor (AC05-02).
Major Compressor Components
Major Compressor Components (AC05-02).
Compressor Stator Winding
Compressor Stator Winding (AC05-02).
Compressor Thermal Protection
Compressor Thermal Protection - Texas Instruments (AC05-02).
Reciptrocating Compressor Pistons and Valves
Pistons and Valves (AC05-02).
Reciptrocating Compressor Motor Bearing
Reciprocating Compressor Motor Bearing (AC05-02)
Carrier - Single Phase Compressors
C=Common, R=Run, S=Start
Winding Resistance
C-R 0.6
C-S 5.2
S-R 5.8

Two-Speed Compressors

Two speed compressors change speed to match the load requirement. Doubling the speed of the motor nearly doubles the capacity (tonnage) of the system. The speed of the motor is changed by connecting the motor windings in series or parallel to form either a 4-pole (1750 rpm) or 2-pole (3500 rpm) motor.

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Schematic of Two-Speed Compressor Motor
The Main Winding in Copland's Two-Speed Compressor is Split.
Terminal Connections for Two Speed Compressor
To Accommodate the Additional Terminals,
there are Two Hermetic Fusite Plugs.
Two Two-Speed Terminal Blocks
Two Hermetic Terminal Blocks for the Motor and a Third
Terminal Block for a Temperature Sensor (F13-042)
Carrier - Two-Speed Compressor
Winding Resistance at 70°F
Winding 3 TON 4 TON 5 TON
T1-T2 Ext. Main 0.80 0.70 0.60
T1-T3 2-Pole Start 3.20 2.20 1.80
T1-T7 Main 1.30 1.00 1.00
T1-T8 4-Pole Start 3.10 2.20 2.00

Two-Speed Compressors - Case History

According to homeowners, this air conditioner failed when the air condition technician shorted something out which caused a voltage surge. In addition, the causing the two-speed compressor to fail, it caused the fan of a different condenser unit to fail and the auto-play box on their piano. I was hired as an expert electrical engineer by the insurance company of technician. The oil in the compressor was burned. This cannot occur in one or two seconds. To break down oil, it has to be overheated for a long period of time usually repeatedly. Ditto for the motor winding, all of one the windings is burned. This is not a localized (spot) failure. It took heat over a long period of time to blister and crack the enamel insulation. As for the other items, the circuit breaker panel box for the two-speed compressor had built in surge protection.
Carrier Two-Speed Condenser Unit
Carrier - Two-Speed Condenser Unit (F13-042).
Two Sets of Contactors for Two-Speed Motors
Two-Speed Condenser Units have Two Contactors
with a Mechanical Interlock (F13-042).
Carrier Two-Speed Condeser Tag
Carrier- Two-Speed Condenser Tag.
Manufactured in the 18th week of 2000 (F13-042).
Copeland Two-Speed Compressor Tag
Copland - Two-Speed Compressor Tag.
Manufactured in January 2000 (F13-042)
Winding Resistances
Winding Ideal Actual
T1-T2 Ext. Main 0.80 0.80
T1-T3 2-Pole Start 3.20 0.50
T1-T7 Main 1.30 1.40
T1-T8 4-Pole Start 3.10 3.50

Resistance Measurements indicate the 2-Pole Start Winding
(High Speed) is Bad i.e. Turn-to-Turn Shorts (F13-042).

Collected Dark Oil from Two-Speed Compressor
The Collected Oil was Dark Brown (F13-042).
Comparison of Burned and New Compressor Oil.
Comparison of Burned and New Compressor Oil (F13-042).
Motor Manufactured Date on Stator Block
The Motor was manufactured on the
340th Day of 1999. (F13-042).
Melted Mylar Insulation
Melted Mylar Insulation (F13-042).
Damaged Motor Wire Insulation
Blistered and Cracked Enamel Wire Insulation (F13-042).
Damaged Motor Slot Insulation
Melted Insulation (Dacron-Mylar-Dacron)
in the Winding Slots (F13-042).
Motor Rotor and Crankshaft
Motor Rotor and Crankshaft (F13-042).
Pistons and Valves (F13-042).
Pistons and Valves (F13-042).

Scroll Compressor

Scroll compressors pump refrigerant by the interaction of a stationary and orbiting scroll. There are no suction or discharge valves. Scroll compressors have less moving parts, and they are more tolerant of liquid slugging and flooded starts. To view the all of the internal parts, the containment vessel has to be cut three times.
This scroll compressor failed due to moisture getting into to the system. Most refrigerant contain chlorine, which will slowly mix with water to from hydrochloric acids. The hydrochloric acids dissolve or leach copper from the refrigeration lines and coils, and the copper is deposited or plated onto non-copper components. In this case, the failure was due to hydrochloric acids dissolving the enamel insulation on the motor wire. It is not known when or how moister entered the refrigeration system, but the compressor was manufactured in 1997, and it did not fail until 2007.

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Scroll Compressor
Scroll Technologies Compressor (F07-19).
Scroll Technologies Tag
The 2nd and 3th Digits of the Serial Number are the Week
and the 4th and 5th Digits the Year - Week 34, 1997 (F07-19).
Cut Scroll Compressor
Cut Three Times to Expose all Interior Components (F07-19).
Top of Scroll Motor Winding
Top of the Motor Stator Winding (F07-19).
Bottom of Scroll Motor Winding
Bottom of the Motor Stator Winding (F07-19).
Scroll Induction Rotor
Motor Induction Rotor (F07-19).
Copper Plating on Scrolls
Copper Plating on Scrolls (F07-19).