Mira Zest 7.5 Technical Document

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Maintenance Guide
Operation &B
Installation
ELECTRIC SHOWERS
THESE INSTRUCTIONS ARE TO BE LEFT WITH THE USER
7.5 and 8.5 kW

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Contents
Page
Introduction ................................................................... 3
Important Safety Information .................................................... 4
Pack Contents Checklist .......................................................... 6
Dimensions ................................................................... 7
iring Diagram ................................................................... 8
Specifications ............................................................................ 8
Installation Requirements......................................................... 9
Installation ................................................................. 13
Commissioning ....................................................................... 15
Operation ................................................................................. 17
Maintenance ............................................................................ 21
Fault Diagnosis ....................................................................... 26
Spare Parts .............................................................................. 28
Accessories ............................................................................. 30
Notes ................................................................................. 31
Guarantee, Customer Care Policy, and How to contact us
.............................................................................. Back cover

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Introduction
Ifyouexperienceanydifficultywiththeinstallationoroperationofyournewshower
control,thenpleaserefertothe Maintenance and Fault diagnosis section,before
contactingCaradon Plu bing Solutions.Ourtelephoneandfaxnumberscanbe
found on the back cover of this guide.
Thank you for purchasing a quality Mira product. To enjoy the full potential of your new
product,pleasetaketimetoreadthisguidethoroughly,havingdoneso,keepithandyfor
futurereference.
TheMiraZestelectricshowershaveseparatecontrolsforpowerselectionandtemperature/
flowadjustment.Auniqueflowregulatorstabilisestemperaturechangescausedbywater
pressure fluctuations. These can result from taps being turned on or off or toilets being
flushed.
Appliances covered by this guide:
Mira Zest 7.5 -A7.5kW240VAC(6.9kW230VAC)heaterwithaMiraReactadjustable
sprayhandset.Suppliedcompletewithflexiblehose,adjustableclampbracketassembly,
slide bar and supports and hose retaining ring. Available in white finish.
Mira Zest 8.5 -A8.5kW240VAC(7.8kW230VAC)heaterwithaMiraReactadjustable
sprayhandset.Suppliedcompletewithflexiblehose,adjustableclampbracketassembly,
slide bar and supports and hose retaining ring. Available in white finish.

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Section Important Safety Information
ARNING!
1.1. Productsmanufacturedbyus aresafe andwithout riskprovided theyare installed,
usedandmaintained in goodworkingorder in accordancewithour instructionsand
recommendations.
1.2. THIS APPLIANCE MUST BE EARTHED.
In accordance with the current edition of ‘The Plugs and Sockets etc. (Safety)
Regulations' in force at the time of installation. This appliance is intended to be
permanently connected to the fixed electrical wiring of the mains system.
1.3. DO NOT twist the individual cable cores of the live and neutral conductors, as this
will prevent them from entering the terminal block.
1.4. Theshower unitmust notbe fittedwhere itmay beexposed tofreezing conditions.
Make sure that any pipework that could become frozen is properly insulated.
1.5. DO NOT operate this appliance if it is frozen. Allow the appliance to thaw before
usingagain.
1.6. DO NOT operate this appliance if water leaks from the pressure relief valve,
maintenancewill berequired beforethe appliancecan besafely used.
1.7. DO NOT fit any form of outlet flow control as the outlet acts as a vent for the tank
body.Only Mira recommended outlet fittings should be used.
1.8. There are no user serviceable components beneath the cover of the appliance.
Only a competent tradesperson should remove the cover.
1.9. If any of the following conditions occur, isolate the electricity and water supplies
and refer to “To contact us”, on the back page of this guide.
1.9.1. If the cover is not correctly fitted and water has entered the appliance
case.
1.9.2. If the case is damaged.
1.9.3. If the appliance begins to make an odd noise, smell or smoke.
1.9.4. If the appliance shows signs of a distinct change in performance, indicating
aneed for maintenance.
1.9.5. If the appliance is frozen.
1.10. Isolate the electrical and water supply before removing the cover.
1.11. Mains connections are exposed when the cover is removed.
1.12. Refer to the wiring diagram before making anyelectrical connections.
1.13. Ensure all electrical connections are tight, to prevent overheating.

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Caution!
2.1. Read all of these instructions and retain this guide for later use.
2.2. Pass on this guide in the event of change of ownership of the installation site.
2.3. Follow all warnings, cautions and instructions contained in this guide, and on or
insidethe appliance.
2.4. The electrical installation must comply with the “Requirements for Electrical
Installations”commonly referredtoas theIEEWiringRegulations,oranyparticular
regulationsand practices, specifiedby thelocal electricity supplycompany inforce
at the time of installation.The installation should be carried out by an electrician or
contractor who is registered, or is a member of, an association such as:
2.4.1. NationalInspectionCouncilforElectricalInstallationandContracting(NICEIC),
throughouttheUK.
2.4.2. TheElectricalContractorsAssociation (ECA),England andWales.
2.4.3. The Electrical Contractors Association of Scotland (ECAS).
2.5. This is a high power unit; it is essential to contact your electricity supply company
to ensure that the electricity supply is adequate for the purpose.
2.6. The plumbing installation must comply with the requirements of UK Water
Regulations/Bye-laws(Scotland),BuildingRegulationsoranyparticularregulations
and practices, specified by the local water company or water undertakers. The
installationshould becarried out by a plumberor contractorwho isregistered, oris
a member of, an association such as:
2.6.1. Institute of Plumbing (IOP), throughout the UK.
2.6.2. National Association of Plumbing, Heating and Mechanical Services
Contractors(NAPH & MSC), England andWales.
2.6.3. Scottish and Northern Ireland Plumbing Employers’Federation (SNIPEF),
ScotlandandNorthernIreland.
2.7. Anyone who may have difficulty understanding or operating the controls of any
shower should be attended whilst showering. Particular consideration should be
given to the young, the elderly, the infirm, or anyone inexperienced in the correct
operationof thecontrols.
2.8. Whenthisappliancehasreachedtheendofitsserviceablelife,itshouldbedisposed
of in a safe manner, in accordance with current local authority recycling, or waste
disposal policy.

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Tick the appropriate boxes to familiarize yourself with the part names and to confirm that the
parts are included.
2. Documentation
1 x Installation, Operation and Maintenance Guide 
1 x Customer Support Brochure 

Section Pack Contents Checklist
1. Mira Zest 7.5 or 8.5 kW
3 x Wall Plugs 
3 x Fixing Screws 
1 x Mira Zest 7.5 or 8.5

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Section Dimensions
202 mm
297 mm
81 mm

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Specifications
Plumbing
1. Minimummaintained inletpressure 0.7bar forsatisfactory operation.
2. Maximum static inlet pressure 10 bar.
3. Minimum static pressure 0.2 bar to keep the flow valve closed.
Electrical
1. The appliance requires a 40 Amp fuse.
2. The terminal block will not accept cable larger than 10 mm2.
Standards and Approvals
1. This Mira Zest complies with all the relevant directives for CE marking.
Wiring Diagram
Thermal Cutout
Dual Disc
Tank Connection
Load
Pressure/ON/OFF/Power
/Selector Switch
P
E
N
97 Brown
96 Red
88 Red 86 Brown
91 Green
90 Blue
89 Brown

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Installation Re uirements
Plumbing
1. The appliance is designed to operate with a minimum aintained inlet pressure
of 0.7 bar up to a axi u static inlet pressure of 10 bar.
2. The appliance is normally connected to the cold water mains-fed supply.However,
thewatersupply canbetaken fromacold waterstoragecistern, providedthereis a
minimummaintainedinlet headof waterof 7 metres (the vertical distancefrom the
base of the cold water storage cistern to the shower fitting handset). To reduce
pressurelossesandfluctuations, the cistern-fedwatersupply must beindependent
from other supply draw-offs, and should avoid long horizontal pipe runs and use
sweptbends rather than90° elbows.
3. The appliance is suitable for installation within the shower area. It is fitted with a
pressurereliefdevice and mustbepositioned overawater catchment areawiththe
controls at a convenient height for the user.
4. Theappliance is fittedwith a plasticinlet connectorintendedto connectto a 15mm
compression fitting supplied from the top, bottom or back.
5. Do not fit the appliance to the wall and tile up to the case.The appliance must be
fitted onto a finished flat and even wall surface.This is important as difficulty may
beencounteredwhenfittingthecoverandsubsequentoperationoftheunitcouldbe
impaired (small pillars moulded on to the back of the case allow air circulation).
6. Refrainfromapplyingexcessiveforcewhenmakinganyconnections.Alwaysprovide
mechanicalsupportwhenmaking the plumbing connections.
7. Do not install the appliance in a position where it ay beco e frozen. The
shower unit must not be fitted where it may be exposed to freezing conditions.The
shower unit must not be used if suspected of being frozen.
8. We recommend that a non-restrictive (free flowing) isolating valve is fitted in the
coldwater supply pipeto allow thecomplete maintenanceof the appliance. Do not
useavalvewith aloosewasherplate (jumper)asthiscan leadtoabuild up ofstatic
pressure.
9. Toavoiddamagetothecasewhensolderedfittingsareused,pre-solderthepipework
and fittings before connecting them to the inlet stub.
10. The appliance is fitted with a ½ " BSP male outlet thread, to accept a Mira shower
hose.
11. SupplypipeworkMUST be flushedto clear debrisbeforeconnecting the appliance.

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12. Wheninstalledinvery hardwaterareas(above 200 ppmtemporaryhardness) your
installer may advise the installation of a water treatment device, to reduce the
effects of limescale formation. Appliance malfunction due to excessive limescale
formationisnotcoveredbythemanufacturer’s guarantee.Yourlocalwatercompany
will be able to advise the hardness of water in your area.
13. A hose retaining ring is supplied to prevent the handset from dropping below the
spillover level of the bath or shower, which could lead to contamination from back-
siphonage(referto Figure 1).Thesuppliedhoseretainingringshouldmeetthegreat
majority of user requirements for shower installations with flexible outlet fittings.
However, there will be occasions when the hose retaining ring will not provide a
suitable solution. In these instances an outlet double checkvalve, e.g. the Mira
DCV-H, ust be fitted.The inclusion of the Mira DCV-H will increase the required
supply pressure typically by 0.1 bar.
Double checkvalves, fitted in the inlet supply to the appliance, cause a pressure
build-up, which could exceed the maximum static inlet pressure for the appliance.
14. Waterflowcanbeobtainedwithout theelectricalpowerbeingconnected.Thisallows
the plumbing connections to be tested prior to final connection of the electrical
supply.
15. Avoid layouts where the shower hose will be sharply kinked.This may reduce the
life of the hose.
Hose Retaining
Ring
25mmMinimum
Spill-over
Level
Figure 1

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3. The minimum cable size (cross-sectional area) required is 6 mm2under normal
conditions of installation.
I portant! The shower circuit should be separated from other circuits by at least
twicethediameter of thecableor conduit anditshould notberun through thermally
insulatingmaterialor in locationswherethe ambient temperatureislikely to exceed
30 °C. If any of these conditions are unavoidable it is necessary to determine the
cable size which will prevent damage to the cable caused by overheating.
4. To obtain full advantage of the power provided by this unit the shortest possible
cable route from the consumer unit to the shower should be used.The maximum
permissiblecircuit lengthis dependenton currentdemand, voltagedrop andcable
size, refer to the IEEWiring Regulations for further information.
As a guide only, the following maximum permissible lengths are given for 6 mm2
cable protected by a 40A MCB type B and allowing for a 5 volt drop:
Mira Zest 7.5 kW (240V AC) at 240 V - 22 Metres
Mira Zest 8.5 kW (240V AC) at 240 V - 18 Metres
5. A 30 mA residual current device (RCD) should be fitted. This may be part of the
consumer unit or a separate unit.
6. A separate, permanently connected supply must be taken from the consumer unit
to the appliance through a double-pole switch, which has at least
3mm contact separation.Theswitchcan be aceiling mountedpull-cordtype within
the shower room or a wall mounted switch in an adjacent room.
7. DO NOT twist the individual cable cores of the live and neutral conductors, as this
will prevent them from entering the terminal block.
8. DO NOT exert strain on the terminal block.
9. DO NOT turn-on the electrical supplyuntil theplumbing hasbeen completed.
Electrical
1. In a domestic installation, the rating of the electricity supply company fuse and the
consumer unit must be adequate for the additional demand. As these appliances
are high power units, it is essential to contact your electricity supply company to
ensure that the supply is adequate for the appliance. Voltage drop due to local
heavydemandwill reducetheshower's performance.
2. Theappliance ust be earthed byconnecting the supply-cableearthconductor to
theearthterminal.
Supple entary bonding: Within the bathroom or shower room, all accessible
conductive parts of electrical equipment and extraneous conductive parts that are
likely to introduce earth potential, must be electrically bonded to earth using a
minimumcable sizeof 4.0 mm2 if the cable is not mechanicallyprotected (2.5mm2
ifmechanically protected).

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Plu bing and Electrical Sche atic Diagra

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Installation
Mira Zest 7.5 and 8.5
WARNING! Isolatetheelectricalandwatersuppliesbeforeproceedingwiththeinstallation
ofthe appliance.
1. Decideon asuitable positionfor theappliance (minimumdistance of200 mmfrom
the ceiling to allow for cover fit and removal).The position of the appliance and the
showerfittings must provide aminimum gap of 25 mm between the spill-over level
ofthe showertray/bath and the handset.Thisis topreventbacksiphonage(referto
Figure1).
2. Removethe three coverretaining screws.
3. Removethe cover.
4. Removethe service tunnel.
5. Determine the direction of the inlet water supply: top (falling), bottom (rising), or
back inlet .
Note! Make sure that the back inlet does not go directly back into the wall and that
you use a suitable compression fitting.
6. Remove as appropriate, the thinned sections of the appliance case, to allow the
supplies to enter the product.
7. Thoroughly flush the ains-fed cold water supply pipe. The supply ust be
clean and free fro debris BEFORE connecting the appliance.
8. Offer the appliance up to the wall and make sure that sufficient electrical supply
cableis availableforterminalblockconnection.Temporarilyconnect themains-fed
cold water supply pipe. Mark through the casing the position of the three fixing
holes.Remove theappliance fromthe wall.
9. Drillandplugthethree fixing holes.Securetheappliancetothe wall withthescrews
provided.Alternativefixings(notsupplied)maybenecessaryforsomewallstructures.
10. Install the mains-fed cold water supply pipe.
11. Make the connection to the mains-fed cold water supply pipe.
12. Bringtheelectrical supplycableinto thecasethrough oneofthe cableentrypoints.
13. Stripbacksufficient oftheouter cableinsulationto enableroutingto terminalblock.
14. Fit an earth sleeve to the earth conductor. Connect the conductors firmly into the
terminalblock. Makesurethatthebarecoresofeachconductoraresecurelytrapped
withineach conductorclamp.
L = Redwire
N = Black wire
E = Yellow/Greensleevedwire.

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15. Re-tightenthe terminal blockscrews.
16. If necessary, fit an earth bonding clamp to the copper supply pipe and ensure
bonding complies with relevant regulations in force at the time of installation.
17. Refit the cover.Fit the three cover retaining screws and tighten.
Inlet Connector
(The inlet
connector can be
swivelled to suit the
supply)
Cold Water
Supply Pipe
Service Tunnel
Installation of the Mira Zest
Outlet Connector
Fixing Screw
Cover Retaining
Screw
Terminal Block
Electrical Supply
Cable
Splash Guard
(Make sure that it
is secured before
operating the
shower)
Do not fit the Mira
Zest to the wall and
tile up to the case.
The Mira Zest must
be fitted onto a
finished flat and even
wall surface (small
pillars moulded onto
the back of the case
to allow for air
circulation)

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Commissioning
Ifyouareunsurehowelectricshowerswork,pleasereadthroughthe Operation section
beforecontinuing.
1. Makesurethat the TOP controlknob is inthe'STOP' positionandthat theelectrical
supply has been isolated.
2. Turn the BOTTOM control knob fully anticlockwise to the full cold position.
3. Turn the water supply fully on at the isolating valve, check that water is not leaking
from the bottom of the case.
4. Switch on the electrical supply at the double pole switch.
5. Turn theTOP controlknob tothe 'LOW' position.Checkthat waterflowsfreelyfrom
the shower within a few seconds. If not, refer to the Maintenance section. The
water from the handset will be at full force and at a cool temperature.
Note! 'LOW' selectioncan beachieved withoutelectricalpower.
6. Turn the BOTTOM knob slowly clockwise. As the knob is rotated the flow will be
reduced and the temperature will remain cool - this shows that the flow regulator
assembly is operating correctly.Return the knob anticlockwise to full cold position.
7. Turn the TOP knob to the 'MEDIUM' position.The temperature of thewatershould
rise slightly. Allow a few seconds for the warm water to reach the handset - this
shows that the 'MEDIUM' power setting is operating correctly.
8. Turn the TOP knob to the 'HIGH' position.The temperature of the water will rise
further - this shows that the full power setting is operating correctly.
9. Set the shower temperature by rotating the BOTTOM knob as necessary.Turn the
knob clockwise for hotter water and anticlockwise for cooler water.
Note! Whenthe temperatureis changed the flowratewill change.
10. Whenthe requiredtemperatureis reached,push theSTOP buttontostop the flow.
Water willcontinueto flow fromther handset fora fewseconds,as waterispurged
from the tank. Isolate the power at the double pole switch.
11. A small amount of water may be retained in the shower fitting after the shower
control has been turned off.This may drain over a few minutes.
Note! A slight hissing sound may be heard from the appliance during operation.
Highmains waterpressure and high showertemperatureswill effectthetone.This
is quite normal when the shower is in use.
Commissioning

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High Position
Medium Position
Low Position
Stop Position
Full Cold Position
Select Shower Temperature
By Rotating Clockwise As
Necessary

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Advice to Users
1. Electricshowersworkbytakingincoldwaterandpassingitovertheheatingelements
contained in the tank body of the shower.
2. The showering temperature is adjusted by turning the temperature control knob,
which varies the flow of cold water across the elements. The slower the rate of
flow, the warmer the water and vice versa. The holes in the spray plate of the
shower handset should always be kept clean to maintain a consistent flow and
stable shower temperatures.
3. The appliance is designed to stabilise temperature changes caused by water
pressure fluctuations.These can result from taps being turned on or off or toilets
being flushed. Under such conditions average shower temperatures will be held
withina 6°Cband, provided thatthe minimumrequired pressureis maintained.
4. Seasonal changes in the temperature of the incoming cold water supply and/or
fluctuations in mains electrical voltage, will require the 'TEMPERATURE' knob to
beadjusted asnecessary.
5. Theappliancerequiresaminimummaintained/running pressureof0.7bartooperate.
Atpressuresabove0.7 bar theappliancewillminimise the temperaturefluctuations
causedwhenotherdraw-offpointsareused.Iftheflowratedropsbelowanacceptable
value, the appliance will turn the heater elements off, resulting in a cold shower.
6. If the water temperature reaches an unsafe level, the thermal switch assembly
turns off the heating elements. As the water temperature falls the elements will be
turned on.The switch will cycle on/off/on if the flow rate is not increased and the
temperatureofthe shower reduced.
7. Checkthe showertemperaturebefore entering the shower.Theprevioususer may
have selected a different temperature setting.
8. Whenthe showerisfirst turned on, or a differenttemperatureis selected,there will
be a slight delay before the water temperature changes.
Operation

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Temperature rise versus flow rate for the Mira Zest range
Flow rate (litres per inute)
Te perature rise °C
8.5kW
7.5kW
01 3 267 109854
10
15
20
25
30
35
40
45
50
55
Exa ple: For theMira Zest 8.5kW onfull power settingwith anincoming water supply
at 10°C and a showering temperature at 42°C, the temperature rise is 32°C. The flow
rate is therefore, 4 l/min.
(a) These curves are for the specified outputs at 240V.
(b) Allapplianceheatingelementshaveamanufacturingtolerance.Thusflow
rates can be above or below those indicated.
(c) The left-hand scale is temperature rise. (Temperature rise = Showering
temperatureminustheincomingcoldwatertemperature.)

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Mira Zest 7.5 and 8.5
Readthe section 'I portant Safety Infor ation' first.
THE SPRAY PLATE HOLES MUST BE KEPT CLEAR. The spray plate should be
regularly removed and cleaned in descalent. Lack of regular spray plate cleaning will
lead to poor performance and cause early failure of the appliance.
1. Switch on pullcord or wall mounted switch.
2. Rotate the TOP control knob to position 'HIGH' (Full Power).
3. Wait 15-20 seconds for warm water to reach the handset.
4. If necessary turn the BOTTOM control knob slowly to adjust temperature. Allow
10-15 seconds for the adjusted temperature to reach the handset. The control
knoboperatesthroughapproximately¾ of a turn from cold to hot.Clockwiserotation
will give warmer water with less flow. Anticlockwise rotation will give cooler water
with more flow.
Note! Should the product alternate (Hot - Cold). Adjust the bottom control knob
anti clockwise to reduce the temperature. This is normal operation if too high a
watertemperature isselected.
5. TO TURN OFF turn the TOP control knob anticlockwise to the 'STOP' position.
6. A small amount of water may be retained in the shower fitting after the shower
control has been turned off.This may drain over a few minutes.
(For summer economy showering use the 'MEDIUM' (Half Power) position on the
control.For a cold shower select 'LOW'.
Note! 'LOW' selection canbe achieved withoutelectrical power.
7. Switch off at the pull-cord or wall mounted switch.

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