Emerson Fluid Chiller Guía para resolver problemas descargar pdf (Pagina 67)

Troubleshooting Solenoid Valves

ProblemCausesCorrective Action

Normally Closed Valve Will Not Open

-or-

Normally Open Valve Will Not Close

Movement of plunger or diaphragm restricted

a) Corroded parts

b) Foreign material lodged in valve

c) Dented or bent enclosing tube

d) Warped or distorted body due to improper

brazing or crushing in vice

Clean affected parts and replace parts as

required. Correct the cause of corrosion or source

of foreign materials in the system.

Improper wiring

Check electrical circuit for loose or broken

connections. Attach voltmeter to coil leads and

check voltage, inrush and holding currents

Faulty contacts on relays or thermostats

Check contacts in relays and thermostats. clean or

replace as required.

Voltage and frequency rating or solenoid coil not

matched to electrical supply:

a) low voltage

b) high voltage

c) incorrect frequency

Check volt

age and frequency stamped on coil

assembly to make certain it matches electrical

source. If it does not, obtain new coil assembly

with proper voltage and frequency rating:

a) Locate cause of voltage drop and correct.

Install proper transformer, wire size as needed. Be

sure all connections are tight and that relays

function properly.

b) Excessively high voltage will cause coil burnout.

Obtain new coil assembly with proper voltage

rating.

c) Obtain new coil assembly with proper frequency

rating.

Oversized Valve

Install correct sized valve. Consult extended

capacities tables.

Valve improperly assembled.

Assemble parts in proper position making certain

none are missing from valve assembly.

Coil Burnout

a) Supply voltage at coil too low (below 85% of

rated coil voltage)

b) Supply voltage at valve too high (more than

10% above coil voltage

rating)

c) Valve located at high ambient

d) Plunger restricted due to: corroded parts,

foreign materials lodged in valve, dented or bent

enclosing tube or warped or distorted body due to

improper brazing or curshing in vise

e) With valve closed, pressure difference across

valve is too high preventing valve from opening

f) Improper wiring. Inrush voltage drop causing

plunger to fail to pull magnetic field due to:

- Wiring the valve to the load side of the motor

starter

- Wiring the valve in parallel with another

appliance with high inrush current draw

- Poor connetions, especially on low voltage,

where connections should be soldered

- Wire size of electrical supply too small

g) Electrical supply (voltage and frequency) not

matched to solenoid coil rating

a) Locate cause of low voltage and correct (check

tran

sformer, wire size, and control rating)

b) Locate cause of high voltage and correct

(install proper transformer or service)

c) Ventilate the area from high ambient. Remove

covering from coil housing

d) Clean affected parts and replace as required.

Connect cause of corrosion or source of foreign

material in the system

e) Reduce pressure differential to less than

300psi

f) Correct wiring according to valve manufacturers'

instructions. Solder all low voltage connections.

Use correct wire size.

g) Check coil voltage and frequency to ensure

match to electrical service rating. Install new coil

with proper voltage and frequency rating.

ProblemCausesCorrective Action

Normally Closed Valve Will Not Close

-or-

Normally Open Valve Will Not Open

Diaphragm or plunger restricted due to: corroded

parts, foreign material lodged in valve, dented or

bent closing tube, or warped body due to

improper brazing or crushing in vise

Clean affected parts and replace parts as

required. Correct the cause of corrosion or source

of foreign materials in the system. Install a filter-

drier upstream of solenoid valve

Manual opening stem holding valve open

With coil de-energized, turn manual stem in

counter clockwise direction until valve closes

Closing spring missing or inoperativeRe-assemble with spring in proper position

Electrical feedback keeping coil energized, or

switch contacts not breaking circui t to coil

Attach voltmeter at coil leads and check for

feedack or closed circuit. Correct faulty

contacts

or wiring

Reverse pressures (outlet pressure greater than

inlet pressure), or valve installed backwards

Install check valve at valve outlet, or install with

flow arrow in proper direction

ProblemCausesCorrective Action

Valve Closes, But Flow Continues

(Seat Leakage)

Foreign material lodged under seat Clean internal parts and remove foreign material

Valve seat damaged Replace valve or affected parts

Synthetic seat materials chippedReplace valve or affected parts

Valve improperly applied or assembledReplace valve with proper valve or re-assemble

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