Bryant LEGACY 213R Service Manual download pdf (Page 12)

Capacitor

ELECTRICAL SHOCK HAZARD

Failure to follow this warning could result in personal

injury or equipment damage.

Capacitors can store electrical energy when power is off.

Electrical shock can result if you touch the capacitor

terminals and discharge the stored energy. Exercise extreme

caution when working near capacitors. With power off,

discharge stored energy by shorting across the capacitor

terminals with a 15,000--ohm, 2-- watt resistor.

WARNING

NOTE: If bleed resistor is wired across start capacitor, it must be

disconnected to avoid erroneous readings when ohmmeter is

applied across capacitor. (S)

ELECTRICAL SHOCK HAZARD

Failure to follow this warning could result in personal

injury or equipment damage.

Always check capacitors with power off. Attempting to

troubleshoot a capacitor with power on can be dangerous.

Defective capacitors may explode when power is applied.

Insulating fluid inside is combustible and may ignite,

causing burns.

WARNING

Capacitors are used as a phase--shifting device to aid in starting

certain single--phase motors. Check capacitors as follows:

1. With power off, discharge capacitors as outlined above.

Disconnect capacitor from circuit. Put ohmmeter on R X

10k scale. Using an analog ohmmeter, check each terminal

to ground (use capacitor case). Discard any capacitor which

measures 1/2 scale deflection or less. Place ohmmeter leads

across capacitor and place on R X 10k scale. Meter should

jump to a low resistance value and slowly climb to higher

value. Failure of meter to do this indicates an open

capacitor. If resistance stays at 0 or a low value, capacitor is

internally shorted.

2. Capacitance testers are available which will read value of

capacitor. If value is not within ±10 percent value stated on

capacitor, it should be replaced. If capacitor is not open or

shorted, the capacitance value is calculated by measuring

voltage across capacitor and current it draws.

ELECTRICAL SHOCK HAZARD

Failure to follow this warning could result in personal

injury or death.

Exercise extreme caution when taking readings while power

is on.

WARNING

Use following formula to calculate capacitance:

Capacitance (mfd)= (2650 X amps)/volts

3. Remove any capacitor that shows signs of bulging, dents, or

leaking. Do not apply power to a defective capacitor as it

may explode.

Sometimes under adverse conditions, a standard run capacitor in a

system is inadequate to start compressor. In these instances, a start

assist device is used to provide an extra starting boost to

compressor motor. This device is called a positive temperature

coefficient (PTC) or start thermistor. It is a resistor wired in parallel

with the run capacitor. As current flows through the PTC at

start--up, it heats up. As PTC heats up, its resistance increases

greatly until it effectively lowers the current through itself to an

extremely low value. This, in effect, removes the PTC from the

circuit.

After system shutdown, resistor cools and resistance value returns

to normal until next time system starts. Thermistor device is

adequate for most conditions, however, in systems where off cycle

is short, device cannot fully cool and becomes less effective as a

start device. It is an easy device to troubleshoot. Shut off all power

to system.

Check thermistor with ohmmeter as described below. Shut off all

power to unit. Remove PTC from unit. Wait at least 10 minutes for

PTC to cool to ambient temperature.

Measure resistance of PTC with ohmmeter.

The cold resistance (RT) of any PTC device should be

approximately 100--180 percent of device ohm rating.

12.5--ohm PTC = 12.5--22.5 ohm resistance (beige color)

If PTC resistance is appreciably less than rating or more than 200

percent higher than rating, device is defective.

A94006

Fig. 6 – Capacitors

Cycle Protector

Bryant thermostats have anti--cycle protection built in to protect the

compressor. Should a non --Bryant stat be utilized, it is

recommended to add a cycle protector to the system. Solid-- state

cycle protector protects unit compressor by preventing short

cycling. After a system shutdown, cycle protector provides for a 5

± 2-- minute delay before compressor restarts. On normal start-- up, a

5--minute delay occurs before thermostat closes. After thermostat

closes, cycle protector device provides a 3 -- sec delay.

Cycle protector is simple to troubleshoot. Only a voltmeter capable

of reading 24v is needed. Device is in control circuit, therefore,

troubleshooting is safe with control power (24v) on and

high--voltage power off.

With high -- voltage power off, attach voltmeter leads across T1 and

T3, and set thermostat so that Y terminal is energized. Make sure

all protective devices in series with Y terminal are closed.

Voltmeter should read 24v across T1 and T3. With 24v still

applied, move voltmeter leads to T2 and T3. After 5 ± 2 minutes,

voltmeter should read 24v, indicating control is functioning

normally. If no time delay is encountered or device never times out,

change control.

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Bryant LEGACY 213R Service Manual Page 12

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