rada 425-t3 User manual

1
IMPORTANT
Installer: This Manual is the property of the customer
and must be retained with the product for
maintenance and operational purposes.
PRODUCT MANUAL

2
INDEX
Page
SAFETY WARNINGS 3
ADVICE 3
INTRODUCTION 4
DESCRIPTION 4
PACK CONTENTS 5
DIMENSIONS 6
SPECIFICATION 7
INSTALLATION 10
COMMISSIONING 13
OPERATION 16
FAULT DIAGNOSIS 17
MAINTENANCE 19
SPARE PARTS 37
CUSTOMER CARE Back Cover
If you experience any difficulty with the installation or operation of your new
mixing valve, then please refer to the Fault Diagnosis section, before
contacting Kohler Mira Limited. Our telephone and fax numbers can be found
on the back cover of this guide.

3
SAFETY : WARNINGS
1. It is installed, commissioned, operated and maintained in accordance with the
recommendations given in this Manual.
2. Type 3 valves are only used for applications covered by their approved
designations.
3. Periodic attention is given, as necessary, to maintain the product in good functional
order. Recommended guidelines are given in the MAINTENANCE section.
4. Continued use of this product in conditions outside the specification limits given
in this Manual can present potential risk to users.
The function of this thermostatic mixing valve is to deliver water consistently at a
safe temperature. This requires that:
The use of the word ‘failsafe’ to describe the function of a thermostatic mixing
valve is both incorrect and misleading. In keeping with every other mechanism it
cannot be considered as being functionally infallible.
Provided that the thermostatic mixing valve is installed, commissioned, operated
within the specification limits and maintained according to this Manual, the risk of
malfunction, if not eliminated, is considerably reduced.
Malfunction of thermostatic mixing valves is almost always progressive in nature
and will be detected by the use of proper temperature checking and maintenance
routines.
Certain types of system can result in the thermostatic mixing valve having excessive
‘dead-legs’ of pipework. Others allow an auxiliary cold water supply to be added to the
mixed water from the mixing valve. Such systems can disguise the onset of
thermostatic mixing valve malfunction.
Ultimately, the user or attendant must exercise due diligence to ensure that the delivery
of warm water is at a stable, safe temperature. This is particularly important in such
healthcare procedures as supervised bathing of patients unable to respond immediately
to unsafe temperatures.
ADVICE

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INTRODUCTION
The Rada 425-t3 Thermostatic mixing valve is specified to meet the highest standards
of safety, comfort and economy as demanded by todays users. The Rada 425-t3 is
designed, manufactured and supported in accordance with accredited BS EN ISO
9001:1994 Quality Systems.
This Manual covers all Rada 425-t3 Thermostatic mixing valves manufactured from
May 2001.
The suffix t3 indicates that the valve has been certified for use in UK healthcare
premises as a Type 3 mixing valve under the TMV3 scheme. Where this product is to
be used in such an installation, particular Application, Installation, Commissioning
and Maintenance requirements apply. These are given in the section ‘TYPE 3 VALVES’.
DESCRIPTION
Rada 425-t3 c - Exposed model, surface mounted. Angle inlet checkvalve
elbows rotate to accept rising, falling or rear-fed supplies.
A 1" inlet/outlet thermostatic mixing valve employing the unique 'thermoscopic'
temperature sensor to provide water at safe, accurate temperatures for ablutionary
or process requirements.

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PACK CONTENTS
Tick the appropriate boxes to familiarize yourself with the part names and to confirm
that the parts are included.
9
Documentation
1 x Product Manual 
4 x Fixing Screws 
3 x Compression Fittings
4 x Wall Plugs 
1 x 425-t3 Mixing Valve 
1 x Hexagonal Wrench 

3 x Olives 
3 x Compression Nuts 

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All dimensions are nominal and in mm
DIMENSIONS
200 mm
300 mm
56 mm 144 mm
150 mm
73.5 mm
246 mm

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SPECIFICATION
Normal Operating Conditions are considered as:
- inlet dynamic pressures nominally balanced to within 10% of each other during
flow.
- a differential of approximately 50oC between the hot and cold inlet temperatures,
and with differentials of 15-35oC between the blend setting and either supply.
- daily usage of 1-6 hours.
- installation and usage environment not subject to extremes of temperature,
unauthorised tampering or wilful abuse.
Other Applications
For information on other specific applications or suitability, refer to Kohler Mira Ltd, or
Local Agent.
Disinfection
In applications where system chemical disinfection is practised, chlorine can be used
(calculated chlorine concentration of 50 mg/l (ppm) maximum in water, per one hour
dwell time, at service interval frequency). Such procedures must be conducted strictly
in accordance with the information supplied with the disinfectant and with all relevant
Guidelines/Approved Codes of Practice.
If in any doubt as to the suitability of chemical solutions, refer to Kohler Mira Ltd, or
Local Agent.
Pressures and Flow Rates
Recommended Minimum Dynamic Supply Pressure: 0.15 bar (0.2 bar
healthcare).
Recommended Minimum Flow Rate: 8 l/min at mid-blend with equal dynamic
supply pressures.
Recommended Maximum Flow Rate: 200 l/min at mid-blend (which equates
to maximum pressure loss of 3.5 bar).
Maximum Pressure Loss Ratio*: should not exceed 10:1, in favour of either
supply, during flow.
Maximum Static Pressure is 10 bar.
Recommended maximum flow velocity in pipelines is 2 metres/second.
Operating Parameters
For Type 3 valves the supply conditions specified in Type 3 Valves - Application take
precedence over the operating parameters which follow.
For optimum performance, dynamic supply pressures should be nominally
equal.

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Temperatures
Optimum Thermostatic Control Range: 35 - 46oC.
Recommended Minimum Cold Water Temperature: 1oC.
Recommended Maximum Hot Water Temperature: 85oC.
0 1 2345
0
200
150
100
50
250
Pressure Loss - bar
Flow Rate - Litres/Min
Hydraulic Restriction: Flow Rate Pressure Loss Graph
(mixing valve only, equal dynamic supply pressures and mid-blend temperature
setting, rising or falling pressure loss).
Optimum performance is obtained when temperature differentials of 20oC or more
exist between blend and either supply. Blend control accuracy will begin to diminish at
temperature differentials below 12oC.
Blend Temperature Range: between ambient cold and approximately 60oC,
according to hot water supply temperatures.
Thermostatic Control Range: approximately 25-60oC.
Note! If the hot water supply system does not incorporate safety devices (e.g. non self
resetting thermal cut out) to prevent this temperature being exceeded then the use of
a tempering valve may be considered to limit the temperature of the water supplied to
the mixing valve. The output temperature of this tempering valve must be set to a value
not less than 60oC and it must not exceed 85oC if the hot water supplied to it reaches
the maximum possible value which may occur under fault conditions in the hot water
apparatus.
* Pressure Loss Ratio is determined by subtracting the resistance of the outlet
pipework and outlet fittings from the dynamic pressures of the hot and cold
water at the inlets of the mixing valve. This is at its extreme when the mixing
valve is used at its lowest flow-rate and when the maximum inequality occurs in
the pressure of the hot and cold water supplies.

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The Rada 425-t3 mixing valve does not have integral flow control, appropriate provision
must be made for this in the outlet pipework.
This can be in the form of basin/bath tap, stop-cock, mechanical timed-flow controller
or solenoid.
The device chosen must be non-concussive in operation.
Flow Control
Connections
Rada 425-t3 c - inlets and Outlet: 1" BSP female/28 mm compression. Angle inlet
checkvalve elbows rotate to accept rising, falling or rear-fed
supplies.
Standard connections are: hot - left (marked red)
cold - right (marked blue)
outlet - top (can be altered to bottom outlet
if required by repositioning the drain
plug)
This model can operate in any plane, provided hot and cold pipework is connected to
the appropriate inlets (hot - red, cold - blue).

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INSTALLATION
General
Installation must be carried out in accordance with these instructions, and must be
conducted by designated, qualified and competent personnel.
1. Before commencing, ensure that the installation conditions comply with the
information given in SPECIFICATION. For Type 3 valves see also Installation
conditions in TYPE 3 VALVES.
2. Care must be taken during installation to prevent any risk of injury or damage.
3. The mixing valve should be positioned for easy access during use and
maintenance. All routine maintenance procedures can be conducted with the
mixing valve body in place (except for strainer and checkvalve access). For all
models, allow a minimum 80 mm clearance in front of the temperature control to
enable removal of the servicable parts during maintenance.
4. The use of supply-line or zone strainers will reduce the need to remove debris at
each mixing valve point. The recommended maximum mesh aperture dimension
for such strainers is 0.5 mm.
5. Pipework must be rigidly supported.
6. Pipework dead-legs should be kept to a minimum. The mixed water outlet piping
should not exceed 2 m and the overall length from the hot water circuit to the
discharge point should not exceed 5 m.
7. Supply pipework layout should be arranged to minimise the effect of other outlet
usage upon the dynamic pressures at the mixing valve inlets.
8. Inlet and outlet threaded joint connections should be made with PTFE tape or
liquid sealant. Do not use oil-based, non-setting jointing compounds.
9. To eliminate pipe debris it is essential that supply pipes are thoroughly
flushed through before connection to the mixing valve.
Outlet Position/Reversed Inlets
The Rada 425-t3 c mixing valve is supplied with the inlet connections configured
hot - left, cold - right, and top outlet as standard.
Should the existing hot and cold pipework make this configuration inconvenient
then turn the whole valve through 180o (The internal components are not
reversible).
If a bottom outlet position is required, remove the blanking cap from the bottom of
the valve and replace it with the fitting from the top of the valve. Then fit the
blanking cap to the top of the valve.

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Installation
The Rada 425-t3 c has easily adjustable inlet elbows to accommodate rising or
falling supplies.
1. When unpacked, the inlet elbows are positioned to accept falling supplies. Should
the installation require rising supplies then the inlet elbows will need adjusting.
- Loosen each inlet elbow grub screw using the 3 mm hexagonal wrench (supplied).
Note! Each inlet elbow has four grub screws, two for removal of the isolator
assembly and two for removal of the inlet elbow.
- Pull the inlet elbow away from the valve body and refit in the desired position.
- Loosen isolator assembly grub screws and position so that the isolator is
accessible.
- Tighten the grub screws.
2. Loosen the backplate grub screws (2 off) using the 3 mm hexagonal wrench
(supplied) and remove the backplate.
3. Position the backplate on the wall and mark the position of the fixing holes (4 off).
Remove the backplate and drill the fixing holes.
4. Fix the backplate securely to the wall surface using the fixing screws and wall
plugs provided.
5. Important! Flush through the hot and cold supplies thoroughly before connection
to the valve.
6. Fit the valve onto the backplate and tighten the grub screws (2 off).
7. Connect the hot, cold and outlet supplies using the fittings, olives and compression
nuts supplied and check for any leaks.
8. The maximum temperature may now need resetting. Refer to COMMISSIONING.

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Backplate
Isolation
Screw
Isolator
Assembly
Compression
Nut
Olive
Wall Plugs
Fixing Screws
Grub Screw
Fitting
Inlet
Pipework
Inlet
Pipework
Outlet
Pipework
2 x Grub Screws
(for removal of
inlet elbow)
2 x Isolator Assembly
Grub Screws
Installation
Figure 1

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COMMISSIONING
Commissioning must be carried out in accordance with these instructions, and
must be conducted by designated, qualified and competent personnel.
Maximum Temperature
Exercising the Thermostat
The maximum blend temperature obtainable by the user should be limited, to
prevent accidental selection of a temperature which is too hot.
All Rada Thermostatic mixing valves are fully performance tested individually and
the maximum temperature is pre-set to approximately 45 oC under ideal installation
conditions at the factory.
Site conditions and personal preference may dictate that the maximum temperature
has to be re-set following installation (For Type 3 valves in healthcare installations
the maximum blend temperature is determined by the application - see Table under
Application in Type 3 Valves).
Maximum Temperature Setting
Check that an adequate supply of hot water is available at the hot inlet of the
mixing valve.
The minimum temperature of the hot water must be at least 12 oC above the
desired blend, however, during resetting this should be close to the typical storage
maximum to offset the possibility of any blend shift due to fluctuating supply
temperatures.
Check that both inlet isolating valves are fully open.
Temperatures should always be recorded using a thermometer with proven
accuracy.
Thermostatic mixing valves with wax thermostats are inclined to lose their
responsiveness if not used. Valves which have been in storage, installed but not
commissioned, or simply not used for some time should be exercised before
setting the maximum temperature or carrying out any tests.
A simple way to provide this exercise is:
(a) ensure that the hot and cold water are available at the valve inlets, and the
outlet is open.
(b) move the temperature control rapidly from cold to hot and hot back to cold
several times, pausing at each extreme.

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2. Pull off the hub.
Note! Leave the pressure washer in place on spindle.
3. Invert the hub and use to rotate the spindle until required maximum blend
temperature is obtained at discharge point; turn clockwise to decrease, anti-
clockwise to increase temperature. Each graduation on the cover shroud equals
an approximate change of temperature of 2oC.
When resistance is felt do not use force to turn any further, as this can
damage the internal parts.
4. Once the desired maximum blend temperature is achieved, gently remove the
hub and, without disturbing the spindle, reposition it so that the stop lug is against
the brass stop on the valve cover, so preventing further anti-clockwise rotation.
Ensure that the pressure washer is in place on spindle behind hub and that the
circlip is secure. Check that blend temperature has not altered.
5. Important! rotate hub slowly clockwise until the minimum required cool (but not
fully cold) water temperature is obtained, then fit temperature knob onto hub so
that the indicator on the temperature knob aligns with the stop lugs on the hub
(refer to Figure 2).
6. Replace the temperature knob and the screw.
For Adjustable Temperature
1. Remove the temperature knob concealing cap and then the screw using the 3
mm hexagonal wrench.(refer to Figure 2).
For Locked Temperature
1. Remove the temperature knob concealing cap and then the screw using the 3
mm hexagonal wrench.(refer to Figure 2).
2. Pull off the hub.
3. Rotate the spindle until required maximum blend temperature is obtained at
discharge point (clockwise = decrease temperature, anticlockwise = increase
temperature).
When resistance is felt do not use force to turn any further, as this will
damage the internal parts.
4. Once the desired maximum blend temperature is achieved, refit the hub without
disturbing the spindle, positioning it so that the stop lugs in the hub fit over the
top of the cartridge stop (refer to Figure 3), preventing further rotation. Check
that blend temperature has not altered.
5. Re-fit the temperature knob.

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3. All connections and the mixer body are water tight.
4. Exercise the thermostat.
5. Adjust the temperature of the mixed water in accordance with the instructions
(refer to Maximum Temperature Setting). For type 3 valves refer to the table
under Application in TYPE 3 VALVES.
Commissioning Checks
(Temperatures should always be recorded with a thermometer with proven accuracy).
1. Check inlet pipework temperatures for correct function of checkvalves i.e. that
hot water does not cross flow into the cold supply and vice versa.
2. Check that the supply pressures are within the range of operating pressures for
the valve.
(a) ensure that the hot and cold water are available at the valve inlets, and the
outlet is open.
(b) move the temperature control rapidly from cold to hot and hot back to cold
several times, pausing at each extreme.
Commissioning - Adjustable Temperature Setting
Figure 2
Note position of brass stop
Stop Lugs
Hub
Screw
Temperature
Knob
Commissioning - Locked Temperature Setting
Figure 3
Screw
Hub
Temperature
Knob
Stop Lugs
Concealing Cap
Concealing Cap

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OPERATION
For models with a standard temperature knob fitted, adjustment of the blend temperature
from preset maximum to cold is achieved by clockwise rotation of the knob. Each
graduation on the cover shroud equals an approximate change of temperature of 2oC.
6. Operate the outlet flow control and check:
(a) Flow rate is sufficient for the purpose
(b) Temperature(s) obtainable are acceptable.
It is advisable to establish a performance check at this time, which should be noted
for future reference as part of a Planned Maintenance Programme. The procedure
should be chosen to imitate both typical and difficult operating conditions, such as
any supply pressure fluctuations that may be likely. An ideal method is to locate
another outlet on the common cold water supply close to the mixing valve (operating
this outlet should cause a drop in supply pressure), and note the subsequent effect
on blend temperature (should be no more than 2oC change).
Locked
No Movement
(preset max)
Anticlockwise
Hotter to Pre-set
Max.
Clockwise
Cooler

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FAULT DIAGNOSIS
Symptom Cause/Rectification
1. Only hot or cold
water from outlet.
a. Inlet supplies reversed (i.e. hot supply to cold inlet).
Check.
b. No hot water reaching mixing valve. Check
c. Check filters and inlet fittings for blockage.
d. Refer symptom 5below.
e. Installation conditions continuously outside operating
parameters: refer to SPECIFICATION and 2e below.
2. Fluctuating or
reduced flow
rate.
3. No flow from
mixing valve
outlet.
a. Check filters and inlet/outlet fittings for blockage.
b. Hot or cold supply failure; thermostat holding correct
shutdown function: rectify, and return to 2e above.
4. Blend
temperature drift.
Check inlet isolators are fully open.
5. Hot water in cold
supply or vice
versa.
Indicates check valves require maintenance, refer to
MAINTENANCE.
Normal function of mixing valve when operating
conditions are unsatisfactory.
Indicates operating conditions changed.
a. Refer to symptom 2 above.
b. Hot supply temperature fluctuation (rectify and refer to
COMMISSIONING).
c. Supply pressure fluctuation (refer to INSTALLATION;
General).
d. Valve requires servicing. Fit ‘O’ Seal pack.
e. Fit new thermostat pack.
a. Check filters and inlet/outlet fittings for flow restriction
(check isolators are fully open).
b. Ensure that minimum flow rate is sufficient for supply
conditions.
c. Ensure that dynamic inlet pressures are nominally
balanced.
d. Ensure that inlet temperature differentials are sufficient.
e. (subsequent to rectification of supply conditions) Check
thermostatic performance; renew thermostat assembly
if necessary.
(Continued)

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Symptom Cause/Rectification
7. Waterleaking from
valve body.
Seal(s) worn or damaged.
a. Obtain Seal Pack, and renew all seals.
b. (If leak persists from around temperature spindle).
Renew sleeve and shuttle assembly.
(Continued)
6. Maximum blend
temperature
setting too hot or
too cool.
a. Indicates incorrect temperature setting; refer to
COMMISSIONING.
b. As symptom 4 above.
c. As symptom 5 above.

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MAINTENANCE
General
1. The maintenance of this product must be carried out in accordance with instructions
given in this Manual, and must be conducted by designated, qualified and
competent personnel.
2. Rada products are precision-engineered and should give continued superior and
safe performance, provided:
- They are installed, commissioned, operated and maintained in accordance with
the recommendations stated in this Product Manual.
- Periodic attention is given as necessary to maintain the product and its associated
installation components in good functional order. Guidelines are given below.
3. The use of main supply-line or zone strainers (recommended maximum mesh
aperture dimension is 0.5 mm) will reduce the need to remove debris at each
mixing valve point.
Planned Maintenance Programmes
(Preventative/Precautionary Maintenance)
The frequency and extent of attention required will vary according to prevailing site
and operational conditions. In applications (such as non-healthcare) where the
risks to the user are too slight to justify the full in-service test procedure and
maintenance logging process, the procedure under Performance check is
suggested to cover average duty and site conditions.
1. In all other cases it is recommended that a routine of preventative maintenance
be employed which is based upon assessment of the risks to the user. The
following practices are intended to support such a routine:
- In-service tests
- Regular temperature checking in between In-service tests
- Maintenance of a log of In-service tests and temperature checks together with
details of critical parts replacements and any other service work.
2. Thermostatic mixing valves only operate correctly when all components have
been serviced and have been tested for correct performance. If any component
is faulty, including the thermostat the valve will not operate correctly and could
allow full hot water to pass through the valve.
3. As with all other thermostatic mixing valves, the critical sensing element in the
Rada 425-t3 c together with other “critical components” (table 1) will exhibit wear
over a period of time and usage.

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The designed minimum service life of all these “critical components” is 5 years
providing the Rada 425-t3 c is operated with the recommended operating conditions
and within the recommended operating parameters. However, when supply
conditions and/or usage patterns do not conform to the recommended operating
parameters and/or the recommended operating conditions, the thermostatic unit
and other critical parts may need to be replaced more frequently (‘recommended
operating conditions’ and ‘recommended parameters’ are defined on page 7 of
this Product Manual under the headings of ‘Normal Operating Conditions’ and
‘Operating Parameters’).
Important! In healthcare applications such as hospitals, aged person facilities,
residential care homes, etc. and in any other applications where the user is similarly
at risk, irrespective of supply and usage conditions or the evidence of in-service
tests, the critical components should be replaced at intervals of no more than 3
years.
Pack Number Description
523. 06
523. 12
523. 12
523. 09
523. 09
523. 09
523. 09
Thermoscopic Unit
Seal - Shuttle Separator
Seal - Retaining Cap
Overload Spring
Return Spring
Shuttle
Shuttle Seat
Critical Components
Table 1
Identified
A
G
G
D
D
D
D
During the fitting of critical components listed in the table above it may be
necessary to replace other non-critical components.