Armstrong 425 Instruction Manual

Model No. q Model 425
q Model 425D
Serial No. :
Ship Date :
Model 425
Installation and Maintenance
Water Temperature Controls
Groups of Fixtures - Thermostatic
Keep this manual with installation for
future reference.
Armstrong International
221 Armstrong Blvd., Three Rivers, Michigan, 49093 - USA
armstronginternational.com/brain

2
Introduction.............................................................. 3
Specications .......................................................... 5
General Advisory ..................................................... 5
Safety ...................................................................... 6
Pack Contents ......................................................... 7
Schematic Piping..................................................... 8
Installation ............................................................... 9
General................................................................ 9
Installation Requirements.................................... 9
Tools Required .................................................... 9
Installation Procedure........................................ 10
Commissioning...................................................... 12
Operation............................................................... 13
Servicing & Maintenance....................................... 14
Spare Parts............................................................ 17
Troubleshooting..................................................... 20
Notes ..................................................................... 22
Limited Warranty and Remedy .............................. 24
Contents

3
Thermostatic Mixing Valves (LPM and BAR)
Model
425
Pressure Drop (BAR) Min.
Flow C
V
0.30.7 1.01.4 1.72.1 2.42.8 3.13.4
LPM 56.8 83.3 102.2 117.3 132.5 143.8155.2166.6174.1185.57.6 6.9
Thermostatic Mixing Valves (GPM and PSI)
Model
425
Pressure Drop (PSI) Min.
Flow C
V
5101520253035404550
GPM152227313538414446492.0 6.9
Thermostatic
Model 425
The model 425 Thermostatic Mixing Valve is for institutional
group fixture water temperature control. Compact design with
top and/or bottom blended water outlet makes Model 425 ideal
for recessed enclosure, plumbing chase and utility/mechanical
room installation.
Powerful internal mechanism and stainless steel operating
mechanism resist mineral deposition.
Capable of close temperature control at diverse flow rates
between 2 gpm (7.5 lpm) and 49 gpm (185 lpm). Able to blend
to within 5°F (2°C) of either inlet supply due to “low seepage”
across internal proportioning mechanism.
Operational Specifications
• Dual thermostatic elements provide redundancy in the
event of individual thermostat failure.
• Typical outlet temperature control +/-2°F
• Adjustable maximum temperature limit stop
• Adjustable single temperature lockout
• Thermal shutdown mode upon inlet supply failure
Technical Specifications
• 1-1/4” NPT inlets and 1-1/4” outlet
• Chrome plated brass/stainless steel
• Lead Free compliant
• Operating pressures
Maximum: 150 psi (10 bar)
Minimum: 10 psi (.7 bar)
• Integral inlet check valves and strainers
• ASSE 1017 and CSA B125 certified
• Shipping weight 18 lbs (8.1 kg)
For a submittal drawing, refer to D73767.
Designs, materials, weights and performance ratings
are
approximate and subject to change without notice.Visit
armstronginternational.com for up-to-date information.
Armstrong
Hot Water Group, 221 Armstrong Blvd., Three Rivers, MI 49093 – USA
Phone: [phone], Fax: [phone]
Water Temperature Control - Groups of Fixtures
6.61
(168.0)
3.92
(99.5)
7.63
(193.7)
2.45
(62.2)
7.83
(199.0)

4
Thermostatic
Model 425D
A derivative of the standard Model 425 Thermostatic Mixing
Valve for institutional group fixture control. Compact design with
top and/or bottom blended water outlet makes Model 425 ideal
for recessed enclosure, plumbing chase and utility/mechanical
room installation.
Factory supplied pre-plumbed and pressure-tested Model
425D is supplied as standard with inlet check valves, strainers,
unions, isolations valves and outlet thermometer and stop
valve*.
*Model 425D is supplied with top outlet and can be site
reconfigured for bottom outlet applications.
Operational Specifications
• Dual thermostatic elements provide redundancy in the
event of individual thermostat failure.
• Typical outlet temperature control +/-2°F
• Adjustable maximum temperature limit stop
• Adjustable single temperature lockout
• Thermal shutdown mode upon inlet supply failure
Technical Specifications
• 1” NPT inlets and 1” NPT outlet
• Chrome plated brass/polymer construction with self finish
brass and bronze lead free components
• Lead Free compliant
• Operating pressures
Maximum: 150 psi (10 bar)
Minimum: 10 psi (.7 bar)
• Inlet check valves, strainers, unions and isolation valves
• Fitted with outlet thermometer and isolation valve
• ASSE 1017 and CSA B125 certified
• Shipping weight 35 lbs (15.9 kg)
For a submittal drawing, refer to D76002.
Thermostatic Mixing Valves (GPM and PSI)
Model
425D
Pressure Drop (PSI) Min.
Flow C
V
5101520253035404550
GPM152227313538414446492.0 6.9
Designs, materials, weights and performance ratings
are
approximate and subject to change without notice.Visit
armstronginternational.com for up-to-date information.
Armstrong
Hot Water Group, 221 Armstrong Blvd., Three Rivers, MI 49093 – USA
Phone: [phone], Fax: [phone]
Water Temperature Control - Groups of Fixtures
Thermostatic Mixing Valves (LPM and BAR)
Model
425D
Pressure Drop (BAR) Min.
Flow C
V
0.30.7 1.01.4 1.72.1 2.42.8 3.13.4
LPM 56.8 83.3 102.2 117.3 132.5 143.8155.2166.6174.1185.57.6 6.9
9.9
(252)
5.0
(126)
TYP
11.0
(279)
TYP
13.6
(345)

5
Specications
*Model 425 can accept temporary excursions above 185°F (85°C) and maintain control without sustaining
internal damage. (ASSE 1017 certification requires exposure to 200°F (93°C) for a period of 30 minutes).
Prolonged operation of the Mixing Valve at such elevated temperatures is not recommended.
** Normal operating conditions are considered as a differential of approximately 122°F (50°C) between
the hot and cold inlet temperatures, and with differentials of 59°F (15°C) - 95°C (35°C) between the
blend setting and either supply. 59°F (15°C) is the optimum published minimum differential required to
achieve full thermal performance.
Maximum Hot Water Supply Temperature 158°F (70°C) *
Minimum Cold Water Supply Temperature 33°F (1°C) - 77°F (25°C)
Optimum Minimum Inlet to Outlet Temperature Differential 59°F (15°C) **
Optimum Thermostatic Control Range 86°F (30°C) - 122°F (50°C)
Flow Rate at 45 psi 46 gpm (174 lpm)
Minimum Flow Rate 2 gpm (7.5 lpm)
Maximum Inlet Supply Pressure 150 psi (10 bar)
Minimum Inlet Supply Pressure 10 psi (0.7 bar)
General Advisory
This Model 425 Valve has been supplied for this application based upon information provided to Armstrong at the
time the order was placed.
This Model 425 Valve is configured for use in a “dead-leg” piping configuration.
This Model 425 Valve has not been congured for use in a central pumped re-circulation system.
This Model 425 Valve is not designed to deliver tepid water to emergency fixtures.
For further information, please call our technical department 1-269-279-3602 between 08:00 a.m. to
05:00 p.m. EST.

6
Safety
Applicable codes must be followed and supersede any other instructions.
Generally applicable codes in the US include:
• IPC (International Plumbing Code)
Read this manual
Improper installation or operation may cause a ood resulting in property
damage, personal injury, or death. Armstrong strongly recommends that
a qualied installer be used.
Service must be performed by a qualied person.
Improper installation, start-up, operation, maintenance, or service may
void the warranty.
Hot water or metal may cause scald burns. Skin exposure to 140°F water
or metal for only ve seconds may cause a second degree burn.
Icon Legend
If instructions are not followed:
- injury or death and property damage are imminent
- injury or death and property damage are possible
- potential property damage, expensive repairs, and/or voiding
the warranty may result
The function of a Thermostatic Mixing Valve is to deliver water consistently at a pre-designated temperature.
Model 425 Thermostatic Mixing Valves are precision engineered to give continued superior and safe
performance provided:
1. They are installed, commissioned, operated and maintained in accordance with the recommendations
provided and accepted plumbing practices.
2. Periodic attention is given, as necessary, to maintain the product, the accessory fittings and the plumbing
system in good functional order.
In keeping with every other mechanical product, Model Mixing Valves should not be considered as
functionally infallible and, as such will never totally replace the vigilance and attention of facility nursing/
bathing or other institutional supervisory or industrial safety staff.
Provided that they are installed, commissioned, operated and maintained, the risk of product failure and
its associated consequences, if not eliminated, are reduced to the minimum achievable.

7
Pack Contents
X 1 q
X 1 q
X 1 q
X 3 q
X 1 q

8
Hot Water Supply
Water Heater
Rada 425
Mixed Flow
Cold Water Supply
System Layout
Thermometer
Sink
Shower
Check Valve
Isolation Valve
Stop Valve
Flow Direction
Pipeline
Schematic Piping

9
Installation
General
Installation must be carried out in accordance with these instructions, and must be conducted by designated,
qualied and competent personnel.
The installation must comply with all relevant local and state water plumbing codes.
All plumbing components are to be supplied by the installer. Failure to include these components will compromise
the product, system performance and will void the warranty.
Notes:
1. Model 425 is supplied fully performance and pressure tested.
2. Suitable connections for ease of maintenance should be used on the inlet and outlet ports. (Isolation valves
and unions.)
3. The hot and cold water inlet supply pressures must be nominally equal.
4. The inlet supply pipework must be thoroughly ushed before tting the Model 425 valve.
5. The Model 425 can be installed in both rising supplies and falling supplies.
Installation Requirements
1
2
3
4
5
The use of supply strainers will reduce debris entering the Model 425. The recommended gauge for such
strainers is 35 mesh (mesh aperture dimension = 0.5mm).
Inlet pressure tappings which allow measurement of the inlet pressures to the Model 425 under operating
conditions are particularly recommended for in-service testing.
Pipework must be rigidly supported to avoid any strain on the connections.
Inlet and outlet threaded joint connections should be made with PTFE thread sealing tape or liquid sealant.
Do not use oil-based, non-setting joint compounds.
Run water for 1 minute from both hot and cold supplies to eliminate pipe debris. It is essential that supply
pipes are thoroughly ushed through before connection to the Model 425.
3.0 mm
Tools Required
Driling Drill Bit Screw Driver Pencil Adjustable Allen Key Safety
Machine size 6 mm Plus & Minus Spanner size 3mm Glasses

10
Ø 6mm
a. Unscrew the set screw.
b. Remove the Backplate.
a. Use the Backplate to mark the two mounting holes at
the desired height.
b. Drill the holes (6 mm) and t the wall anchors. Screw
the Backplate to the wall.
Caution! Avoid area where underground wirings
or pipelines pass through.
a. Mount the Valve assembly on the Backplate xed on
the wall. Make sure the Valve assembly locks in the
groove.
b. Tighten the set screw.
a. Important! Prior to assembly of the hot and cold
adapters, look inside each one and ensure that there is
a strainer and a white plastic checkvalve. The adapter
with nothing inside is for the outlet.
Thread the coupling nuts onto the Valve assembly
then tighten using an adjustable spanner.
Caution! Use a soft cloth to protect the plating
from damage while tightening the spanner.
Step 1
Step 3
Step 2
Step 4

11
Step 5
Step 7Step 6
a. Hand-tighten all the nuts as shown above.
a. Fully tighten all of the couplings using an adjustable
spanner.
Caution! Use a soft cloth to cover the plating
from damage while tigtening with spanner.
a. Turn on the water supply and ensure that there are
no leaks.

12
Model 425 is designed for two types of congurations:
1. Locked Temperature (Temperature control is locked and cannot be adjusted)
2. Adjustable Temperature (Temperature can be adjusted through a desired range)
The following steps show the procedure for both type of installations:
Step 1 Step 2
a. Remove the concealing cap.
b. Unscrew the knob using a 3mm Allen Key.
c. Remove the Knob and Hub.
Step 3
Obtain the desired maximum blend temperature then
re-t the Hub in the 6 o’clock position so that the Center
Stop Slot ts over the Cartridge Stop, locking rotation
in either direction.
Factory pre-set outlet temperature = 110°F (43°C)
Open the hot and cold water supplies and open outlets
prior to adjusting the temperature.
Rotate the spindle to adjust the temperature to a desired
level.
Clockwise = Decrease temperature.
Anti-clockwise = Increase temperature.
Keep the spindle undisturbed.
Obtain the desired maximum blend temperature then
re-t the Hub in the 9 o’clock position so the Hub Stop
hits the Cartridge Stop, preventing further anti-clockwise
rotation.
This sets the desired temperature as maximum
achievable temperature.
Commissioning
For Locked temperature For Adjustable temperature

13
Step 4
Operation
Re-t the Knob, tighten the screw and replace the
concealing cap.
Make sure the indicator is in either the 9 o’ clock
position (adjustable temperature conguration) or 6
o’ clock position (locked temperature conguration).
*Maximum temperature stop or single temperature locking feature is established during the on-site commissioning
protocol .
For models with a standard temperature knob tted, adjustment of the blend temperature from preset maximum to
cold is achieved by clockwise rotation of the knob.
2. Constant Temperature
1. Adjustable Temperature
Counterclockwise
Hotter
(to Maximium
Temperature Stop*)
Clockwise
Cooler
Single Temperature
Locked*
(No Movement)
Exercising the Thermostat
Thermostatic mixing valves with 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:
1. Ensure that the hot and cold water are available at
the valve inlets, and the outlet is open.
2. Move the temperature control rapidly from cold to hot
and hot back to cold several times, pausing at each
extreme.

14
Warning! Isolate water supply to Model 425 before proceeding.
Model 425 Thermostatic Mixing Valves and its components should be inspected annually, or more frequently where
acknowledged site conditions such as high mineral content water dictate.
Model 425 can be completely serviced from the front/top and all of the internal components are replaceable. To
access the valves internal components for inspection, cleaning or replacement proceed as follows.
Maintenance must be carried out in accordance with these instructions, and must be conducted by designated,
qualied and competent personnel. This mixing valve is designed for minimal maintenance under conditions of
normal use. External surfaces may be wiped clean with a soft cloth, and if necessary, a mild detergent or soap
solution can be used.
Warning! Many household and industrial cleaning products contain mild abrasives and chemical concentrates,
and should not be used on polished, chromed or plastic surfaces.
Components are precision-made, so care must be taken while servicing to avoid damage.
Lubricant
Important! All seals are pre-lubricated. If you need to further lubricate the seals, use only a small amount of
silicone-only based lubricants on this product. Do not use oil-based or other lubricant types as these may cause
rapid deterioration of seals.
Servicing & Maintenance
Maintenance Procedure - Thermostat Assembly
Isolate the water supplies to the mixing valve . Open an outlet tting to release pressure and to assist the
draining of residual water.
Step 1 Step 2

15
Step 3
Port Sleeve
Assembly
Thermostat
Assembly
Drive Nut
Temperature
Spindle
Maintenance Procedure - Port Sleeve/Shuttle
Assembly
Disassembly
1. Remove both port sleeve screens by releasing the folded tabs.
2. To dismantle the shuttle and sleeve assembly, again insert the bar through the holes at the front of the port
sleeve to hold the assembly whilst the retaining cap is loosened only using a spanner (50 mm) across the
ats.
There is spring tension behind the retaining cap, so complete the unscrewing and removal by hand.
3. Lift out the overload spring and return spring and carefully push out the shuttle seat and shuttle.
Retaining Cap
Return Spring
Overload Spring
Shuttle
Shuttle Seat
Port Sleeve
Assembly
Port Sleeve
Screens
Push out shuttle
from this end

16
Cleaning/Renewal of Parts
1. Internal parts (with the exception of the Thermostat Assembly) can be cleaned using a mild proprietary
inhibited scale solvent e.g. domestic kettle descalent. After descaling, always rinse parts thoroughly in clean
water before retting.
Note! The body interior must be cleaned carefully and not damaged in any way. Do not use any abrasive
material.
2. Examine all accessible seals for signs of deformation or damage, and renew as necessary, taking care not to
damage the seal grooves.
3. Lightly smear all seals and threads with a silicone-only based lubricant to assist re-assembling.
4. Inspect the thermostat assembly for signs of damage.
Note! This component cannot be tested individually, its service condition should be assessed as part of the
performance check; refer to Commissioning Checks.
5. Examine the shuttle seat, the shuttle and the port sleeve for signs of damage or corrosion; renew as necessary.
Re-assembly
1. Insert the shuttle fully into the port sleeve (wider open end) with radius centre face inwards, ensuring that the
separator seal remains in place and is not damaged.
2. Insert shuttle seat into the port sleeve, ensuring that the cut-outs locate into the webs in the shuttle.
3. Insert the return spring through the centre of the overload spring. Insert both springs into the shuttle seat rear
face.
4. Locate the retaining cap over the springs, compress and screw the cap fully into the port sleeve, ensuring that
the threads are correctly engaged.
5. Replace the port sleeve screens, positioning the joint against one of the two solid sections. This will prevent
debris entering through the slot in the screen.
6. Insert the shuttle and sleeve assembly into the valve body and secure in position with the four screws.
7. Install the actuator sleeve and the thermostat assembly into the shuttle assembly.
8. Install the drive nut and the temperature spindle into the cover.
Note! The drive nut will need to be aligned with the grooves inside the cover
9. Fit the cover, ensuring the end of the thermostat locates correctly into the drive nut. Rotate the cover so that it
is positioned in the same position as it was when you removed it. Secure the cover in position with the eight
screws
10. Fit the pressure washer and secure the spindle in position with the circlip. Make sure that the circlip locates
correctly in the groove in the temperature spindle.
11. Before tting the hub, the temperature will need resetting; refer to COMMISSIONING.
12. Fit the cover shroud and secure in position with the two screws.
13. Re-t the temperature knob.

17
Model 425 Spare Parts

18
Model 425 Spare Parts
D58164
D77279
D58161
D58161
D77282
D33385
D33390
D58163
D58163
X 4
X 4
D77283
D79758
A
A
A
A
A
A
D77276
D77276
D77280
D58161
D77276

19
Part No: Description
D33385 Hub Pack
D33390 Knob Pack
D58161 Thermostat Pack
D58163 Port Sleeve Pack
D58164 Shuttle Assembly Pack
D77276 1 - 1/4" NPT Connector Pack (two inlets, one outlet and one blanking plug)
D77279 Drive Mechanism Pack
D77280 Backplate
D77281 Seal Pack - Not illustrated
D77282 Screw Pack - Components Identied 'A'
D77283 Indicator Trim
D79758 1 - 1/4” Check Valve Service Pack - (1) Pair
D79759 Critical Components Pack - Consists of:
(1) D58151 Thermostat Pack
(1) D58164 Shuttle Assembly Pack
(1) D77281 Seal Pack

20
Troubleshooting
Fault Diagnosis
Read the section “Important Safety Information” rst.
If any maintenance is required then it must be carried out by a competent tradesperson. Before replacing any parts
make sure that the underlying cause of the malfunction has been resolved.
Warning! There are no user serviceable components beneath the casing of the appliance. Only a competent
tradesperson should remove the cover.
Symptoms Probable Cause Possible Remedy
1. Only hot or cold water from
outlet.
a. Inlet supplies reversed (i.e.: hot to cold
or vice-versa)
Check-Rectify. Tip: Check rear of valve
under polymer mounting plate for
raised “H” (hot) on appropriate inlet. If
sight evaluation is not possible consult
factory Technical Support for additional
diagnositc tips.
b. No hot water available from hot water
source.
Check-Rectify
c. Screen/lters occluded or inlet supply
ttings plugged.
Refer to Servicing/Maintenance - Rectify.
d. Refer to Symptom 4 below. Refer to Symptom 4 below.
e. Proportioning mechanism (shuttle)
trapped against hot/cold seat.
Refer to Servicing/Maintenance. Place
thumb into port sleeve and depress.
Shuttle should move and spring back
when pressure is relieved.
2. No ow from Mixing Valve
outlet.
a. Hot or Cold inlet supply failure;
Thermostat holding correct shutdown
function.
Check-Rectify.
b. Screens/lters blocked or inlet supply
ttings plugged.
Refer to Servicing/Maintenance - Rectify.
3. Mixed water temperature
at TMV outlet uctuates
and does not respond to
adjustment.
a. Thermostat not operating correctly. Refer to Servicing/Maintenance - Rectify.
b. Mixing Valve operating below minimum
required ow rate.
Check that at least 2 GPM is owing
through valve.
c. Static inlet supply pressures beyond
valves capability to correct.
Check-Rectify
d. Inlet supply pressures fluctuating
beyond valves capability to correct.
Check-Rectify
e. Hot water supply temperature
uctuating beyond valves capability
to correct.
Check by carefully sensing inlet hot
supply pipe work- rectify.
f. Partially occluded screens/lters or
partially blocked inlet ttings.
Refer to Servicing/Maintenance - Rectify.
(contd...)