Murphy A900 Series Portable Generator User Manual

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3-6.1.2 Lamp Test Pushbutton: Tests the lights on the A903

module.

3-6.1.3 Alarm Silence Pushbutton: Turns off any audible alarm

that is connected to the Local or Remote Audible Alarm Relays.

The indicating light will remain on as long as the condition

exists. If the Alarm Silence pushbutton is not operated, the

audible alarm will turn off when the alarm contact clears.

3-6.1.4 The A903 SELECTRONIC

Control Module includes

the following engine control features:

(a) Cycle crank circuit; will crank the engine for 15 seconds

then rest for 15 seconds until the engine starts. The

crank/rest time is selectable for either 10, 15, 20, 25 or 30

seconds. If the engine false starts, goes above crank

disconnect speed then drops below that speed, the control

will rest for a fixed 10 second period before cranking

again.

(b) Crank Disconnect Speed Switch; this circuit detects

engine speed and terminates cranking when engine speed

rises above the speed switch setting. The speed switch is

adjustable, 25 Hz to 2000 Hz, and is factory set at 1180

Hz. This would be 600 RPM on an engine with 118 teeth

on the flywheel ring gear.

by NFPA-110, is provided as a back up for the Crank

Disconnect Speed Switch. It is operated by an external

switch sensing either speed, generator voltage or some

other variable that could be used to terminate cranking.

Either circuit will disconnect the starter when the engine

starts.

(d) Overcrank circuit; will stop automatic cranking and

indicate overcrank if engine fails to start after 3 attempts.

The number of cranks are selectable for 1, 2, 3, 4 or 5

cycles before shutdown. The overcrank circuit may also

be turned off so no overcrank shutdown occurs.

(e) Shutdown Time Delay Bypass; this delay prevents the oil

pressure, water temperature and loss of speed signal

shutdown circuits from operating for 15 seconds after the

engine starts as detected by the crank disconnect circuit.

This same delay also locks out alarm circuit #7 and #8

when the engine is not running.

(f) Overspeed Speed Switch;

1. Provides a signal to the overspeed shutdown circuit if

the engine exceeds the preset speed. The factory

setting is approximately 3894 Hz, or 1980 RPM on an

engine with 118 teeth on the flywheel ring gear. The

adjustment range is 300 Hz to 10,000 Hz.

2. A push to test switch is provided to allow testing of

the overspeed circuit without overspeeding the

engine. When switch is depressed, the set point of the

speed switch is lowered approximately 10%.

3. The push to test switch can also be used to set the

overspeed switch at approximately 110% of running

speed. Hold the switch depressed while adjusting the

setting until the overspeed trips. When switch is

released, the set point will be 10% above normal

running speed. This is the method used to make the

factory setting. With engine speed at 1800 RPM or

3540 Hz.

(g) Cooldown circuit; this circuit keeps the engine running

for five minutes after the transfer switch has removed

the load from the generator and signaled the A903 to

stop the engine. This feature may be selected (turned

On, standard setting is Off) with a switch on the back of

the Control / Display Module.

3-6.1.5 Seven (7) First-out Shutdown Circuits; provide first-

out indication of cause of shutdown. These circuits deactivate

the fuel relay and lockout the A903 until reset. Shutdown

circuits are activated by the crank disconnect circuit and are not

active when the engine is stopped. Six (6) Red Shutdown

Indicating Lights are provided. The Remote Shutdown circuit

does not have an indicator light.

(a) Overcrank; tripped by the overcrank sensing circuit

which counts the number of cranking attempts.

(b) Overspeed; tripped by overspeed switch when engine

exceeds a preset speed.

if pressure drops below preset point while the engine is

running.

(d) Water Temperature; tripped by the water temperature

SWICHGAGE

if engine coolant temperature exceeds

the switch setting.

(e) Spare Shutdown; tripped by an external switch. This

circuit is provided for an additional shutdown that may

be recommended by the engine supplier.

(f) Loss of Speed Signal; tripped by an internal sensing

circuit that detects the loss of the Magnetic Pickup

frequency signal for the speed switches while the engine

is still running. Since the Overspeed shutdown circuit is

activated by the frequency input, it prevents the engine

from running without overspeed protection.

(g) Remote Shutdown; this circuit is provided to shutdown

the engine generator from a remote location. No

indicating light is provided.

3-6.1.6 Nine (9) Alarm Indicating Circuits; provide indication

of cause of alarm. These circuits activate the alarm relays.

Alarm circuits are active as long as power is applied to the

A903. All are active when the engine is running, shutdown or

on standby except alarm circuit #7 and #8 which are locked out

until the engine is running. Nine (9) Amber Alarm Indicating

Lights are provided however only two circuits are labeled. The

other 7 are for customer specified alarms.

(a) Low Water Temperature; operated by low water

temperature SWICHGAGE

(b) #2 Spare Alarm; operated by an external switch. This