Elson 150zd - Maintenance Procedures; General Maintenance Requirements; Safety Valve Operation Check; Direct Unit Maintenance Tasks

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MAINTENANCEREQUIREMENTS
Unvented hot water systems have a continuing
maintenancerequirementinordertoensuresafe
workingandoptimumperformance.Itisessential
thatthereliefvalve(s)areperiodicallyinspected
andmanuallyopenedtoensurenoblockagehas
occurredinthevalvesordischargepipework.
Similarlycleaningofthestrainerelementand
replacementoftheairintheexpansionvesselwill
helptopreventpossibleoperationalfaults.
Themaintenancechecksdescribedbelowshould
beperformedbyacompetentpersonona
regularbasis,e.g.annuallytocoincidewithboiler
maintenance.
Afteranymaintenance,pleasecompletetherelevant
ServiceIntervalRecordsectionoftheBenchmark
ChecklistonPage22ofthisdocument.
INSPECTION
Theimmersionheaterbosscanbeusedasan
accessforinspectingthecylinderinternally.
SAFETYVALVEOPERATION
Manuallyoperatethetemperature/pressurerelief
valveforafewseconds.Checkwaterisdischarged
andthatitowsfreelythroughthetundishand
dischargepipework.Checkvalvereseatscorrectly
whenreleased.NOTE:Waterdischargedmaybe
very hot!
RepeattheaboveprocedurefortheExpansion
ReliefValve.
STRAINER
Turnoffthecoldwatersupply,boilerandimmersion
heaters.Thelowesthotwatertapshouldthenbe
openedtode-pressurisethesystem.Removethe
pressure reducing cartridge to access the strainer
mesh.Washanyparticulatematterfromthestrainer
undercleanwater.Re-assembleensuringtheseal
iscorrectlytted.DONOTuseanyothertypeof
sealant.
DESCALINGIMMERSIONHEATER(S)
Beforeremovingtheimmersionheater(s)theunit
mustbedrained.Ensurethewater,electricalsupply
andboilerareOFFbeforedraining.Attacha
hosepipetothedraincockhavingsufcientlength
totakewatertoasuitabledischargepointbelowthe
leveloftheunit.Openahottapclosetotheunitand
opendraincocktodrainunit.
DIRECTUNITS
Switchonelectricalsupplytotheimmersion
heater(s)andallowtoheatuptonormalworking
temperature(60ºCrecommended,approximately
graduation4onthethermostat).Ifnecessarythe
temperaturecanbeadjustedbyinsertingaat
bladedscrewdriverintheadjustmentknobontopof
theimmersionheaterthermostatandrotating.
Theadjustmentrange1to5representsa
temperaturerangeof12°Cto68°C.Checkthe
operationofthermostat(s)andthatnowater
hasissuedfromtheexpansionreliefvalveor
temperature/pressurereliefvalveduringtheheating
cycle.
INDIRECTUNITS
Open the cover(s) to the immersion heater
housing(s)anddisconnectwiringfromimmersion
heater(s)thermostat(s).Removethermostatby
carefullypullingoutwards.Removethermostat
capillarysensorsfromthepocketsontheimmersion
heater.Unscrewimmersionheaterbacknut(s)and
removeimmersionheaterfromtheunit.Akey
spannerissuppliedwiththecylinderunitforeasy
removal/tighteningoftheimmersionheater(s).Over
timetheimmersionheatergasketmaybecomestuck
tothematingsurface.Tobreakthesealinserta
roundbladedscrewdriverintooneofthepocketson
theimmersionheaterandgentlyleverupanddown.
Carefullyremoveanyscalefromthesurfaceofthe
element(s).DONOTuseasharpimplementas
damagetotheelementsurfacecouldbecaused.
Ensuresealingsurfacesarecleanandsealsare
undamaged,ifindoubttanewgasket
(partnumber95611822).
Replace immersion heater(s) ensuring the lower
(right angled) element hangs vertically downwards
towardsthebaseoftheunit.Itmaybehelpfulto
supporttheimmersionheaterusingaroundbladed
screwdriverinsertedintooneofthethermostat
pocketswhilstthebacknutistightened.Replace
thermostatcapillariesintopocket.Replacethe
immersionheaterthermostatbycarefullyplugging
the two male spade terminations on the underside
ofthethermostatheadintothecorresponding
terminationsontheelement.Rewire,check,close
andsecureimmersionheaterhousingcover(s).
EXPANSIONVESSELCHARGEPRESSURE
Removethedustcapontopofthevessel.Check
the charge pressure using a tyre pressuregauge.
Thepressure(withsystemde-pressurised)should
be0.35MPa(3.5bar).Ifitislowerthantherequired
settingitshouldbere-chargedusingatyrepump
(Schradervalvetype).DONOTOVER-CHARGE.
Re-checkthepressureandwhencorrectreplacethe
dustcap.
RE-COMMISSIONING
Checkallelectricalandplumbingconnectionsare
secure.Closethedraincock.Withahottapopen,
turn on the cold water supply and allow unit to
rell.DONOTswitchontheimmersionheater(s)
orboileruntiltheunitisfull.Whenwaterows
fromthehottapallowtoowforashortwhileto
purgeairandushthroughanydisturbedparticles.
Closehottapandthenopensuccessivehottapsin
systemtopurgeanyair.Whencompletelyfulland
purgedchecksystemforleaks.Theheatingsource
(immersionheater(s)orboiler)canthenbeswitched
on.
MAINTENANCE