CALEFFI 2521 Series Installation, Commissioning And Servicing Instructions

Function

The thermostatic mixer is used in solar thermal systems
producing domestic hot water. Its function is to maintain the
temperature of the mixed water supplied to the user constant at
the set value when there are variations in the supply conditions
of the incoming hot and cold water. This particular series of
mixing valves can function continuously at the high
temperatures of incoming hot water from the solar storage tank.
The valve has been specifically certified to ASSE 1017.

Product range

Series 2521 thermostatic mixing valve. Union thread NPT male
connections, sizes 1/2”, 3/4”,1”; union solder connection, size
1/2”, 3/4”, 1”.

Technical Characteristics

· Materials: - Body: Low‐lead brass

(<0.25% Lead content), chrome plated

- Shutter: PSU

- Springs: Stainless steel

- Seals: EPDM

· Setting range: 85–150°F (30–65°C)

· Accuracy: ±3°F (±2°C)

· Max working pressure (static): 200 psi (14 Bar)

· Max working pressure (dynamic): 75 psi (5 bar)

· Min working pressure (dynamic): 3 psi (0.2 bar)

· Max hot water inlet temperature: 212°F (100°C)

· Maximum inlet pressure ratio (H/C or C/H): 2:1

· Minimum temperature difference between hot water inlet and
mixed water outlet for optimum performance: 30°F (15°C)

· Min. flow rate to ensure stable temperature: 1.3 gpm (5 lpm)

· Certified to: ASSE 1017

· Lead Plumbing Law Compliance: (0.25% Max. weighted

average lead content)

· Lead Plumbing Law Certified by IAPMO R&T

Adjustable Thermostatic Mixing Valve for Solar Systems

2521 Series

28114.01

Installation, commissioning and servicing instructions

ASSE 1017

© C opyright 2010 C a l ef f i

www.caleffi.com

CALEFFI

CAUTION: If the thermostatic mixer is not installed, commissioned and
maintained properly, according to the instructions contained in this
manual, it may not operate correctly and may endanger the user.

CAUTION: Make sure that all the connecting pipework is water tight.

CAUTION: If installing in an ASSE 1017 application, check valves shall

be used.

CAUTION: When making the water connections, make sure that the mixer
connecting pipework is not mechanically over-stressed. Over time this
could cause breakages, with consequent water losses which, in turn,
could cause harm to property and/or people.

CAUTION: Water temperatures higher than 100°F can be dangerous.
During the installation, commissioning and maintenance of the
thermostatic mixer, take the necessary precautions to ensure that such
temperatures do not endanger people.

CAUTION: In the case of highly aggressive water, arrangements must be
made to treat the water before it enters the thermostatic mixer, in
accordance with current legislation. Otherwise the mixer may be damaged
and will not operate correctly.

Leave this manual for the user.

SAFETY INSTRUCTION

This safety alert symbol will be used in this manual to draw attention to safety related
instructions. When used, the safety alert symbol means ATTENTION! BECOME ALERT!

YOUR SAFETY IS INVOLVED! FAILURE TO FOLLOW THESE INSTRUCTIONS MAY
RESULT IN A SAFETY HAZARD.

CAUTION: All work must be performed by qualified personnel trained in the

proper application, installation, and maintenance of systems in accordance
with all applicable codes and ordinances.

Operating Principle

The controlling element of the solar thermostatic
mixing valve is a temperature sensor that is fully
immersed in the mixed water outlet passage. As
it expands or contracts, the sensor continuously
establishes the correct proportion of hot and
cold water entering the valve. The flow is
regulated by a piston sliding in a cylinder
between the hot and
cold water passages.
Even when there are
pressure drops due to
the drawing off of hot or
cold water for other uses
or variations in the
incoming temperature,
the mixer automatically
regulates the water flow
to obtain the required
temperature.

Flow curves

Kv = 2.6

10

0.01

0

.

1

0

.

02

0

.

03

2

5

0.05

1

0.2

0

.

3

0.

5

20

50

∆p (psi)

G (l/min) (

gpm

)

10

2

3

5

2

0

0

.

01

0

.

1

0

.

02

0

.

03

0.05

1

0

.

2

0

.

3

0.

5

(psi) (bar)

10

2

3

5

2

0

1

0.5

10

2

5

2

0

0.001

0

.

01

0

.

002

0

.

003

0.005

0.1

0

.

02

0

.

03

0

.

05

1

.

0

0

.2

0.3

0

.

5

Cv = 3.0

4

0

.04

0.4

0

.04

0.4

4

0.0

04

0.0

4

0

.4

COLD

HOT

MIX

16

14

13

12

11

9

10

8

4

6

7

5

2

3

15

15

16

MIX

COLD HOT

17

1

Exploded diagram

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17

Regulating knob
Head fixing screw
Regulating spindle
“O” Ring seal
Upper shutter seat
Thermostatic element
Inner shutter
“O” Ring
Outer shutter
“O” Ring
“O” Ring
Spring cover
Spring
Valve body
Union nut
Gasket
Tail piece body

Installation

Before installing a Caleffi 2521 series mixing valve, the system
must be inspected to ensure that its operating conditions are
within the range of the mixer, checking, for example, the supply
temperature, supply pressure, etc.

Systems where the Caleffi 2521 series mixing valve is to be

fitted must be drained and cleaned out to remove any dirt or

debris which may have accumulated during installation.
Failure to remove dirt or debris may affect performance
and the manufacturer's product guarantee.
The installation of filters of appropriate capacity at the inlet
of the water from main supply is always advisable.
In areas which are subject to highly aggressive water,
arrangements must be made to treat the water before it

enters the valve.
Caleffi 2521 series mixing valve must be installed in accordance
with the diagrams in this manual, taking into account all current
applicable standards.
Caleffi 2521 series mixing valve can be installed in any position,
either vertical or horizontal.
The following are shown on the valve body:

- Hot water inlet, color red and marked “HOT”.

- Cold water inlet, color blue and marked “COLD”.

- Mixed water outlet, marked “MIX”.
It is essential that access to the valve is totally unobstructed for
any maintenance which may be required to the valve or
connections. The pipework from/to the valve must not be used to
support the weight of the valve itself.

Use

Thermostatic mixing valves are typically installed at the

outlet of hot water storage tanks in solar systems to ensure
constant temperature of the mixed water supplied to the end user.
Because of their flow characteristics, the valves can be installed
to control the temperature for both single point of use and for point
of distribution. In order to guarantee the delivery of mixed water at
the set temperature, the 2521 series thermostatic mixing valves
must have a minimum flow rate of 1.3 gpm.

Application Diagrams

COLD/BLUEHOT/RED

MIX

Key to symbols

Safety relief valve

Isolation and check valve

Isolation valve

Expansion vessel

Filter

HOT

COLD

MIX

MINMAX7

1

2

HOT

COLD

CALEFFI

MIN

M
A
X
7

1

2

T

Normally closed

valve

T

Commissioning

After installation, the valve must be tested and commissioned in
accordance with the instructions given below, taking into account
current applicable standards.

1) Ensure that the system is clean and free from any dirt or debris

before commissioning the thermostatic mixer.

2) It is recommended that the temperature is set using a suitable

calibrated digital thermometer. The valve must be
commissioned by measuring the temperature of the mixed
water emerging at the point of use.

3) The maximum outlet temperature from the valve must be set

taking account of the fluctuations due to simultaneous use.
It is essential for these conditions to be stabilised before
commissioning.

4) Adjust the temperature using the adjusting knob on the valve.

For safety reasons, it is advisable to limit the maximum mixed
water temperature to 120°F in domestic hot water systems.

Setting the temperature

The temperature is set to the required value by means of the
adjusting knob with the graduated scale on the top of the valve.

Preset locking

Position the handle to the number required. Unscrew the head
screw, pull off the handle and reposition it so that the handle fits
into the internal slot of the knob. Tighten the head screw.

Maintenance

In service tests should be carried out regularly to monitor the
mixer performance, as deterioration of performance could
indicate that the valve and/or the system require maintenance. If,
during these tests, the temperature of the mixed water has
changed significantly in comparison with the previous test, the
details given in the installation and commissioning sections
should be checked and maintenance carried out.
The following aspects should be checked regularly to ensure that
the optimum performance levels of the valve are maintained.
Every 12 months at least, or more often if necessary.

1) Check and clean the system filters.

2) Verify that any check valves positioned upstream of the Caleffi

valve are operating correctly, without problems caused by
impurities.

3) The Caleffi valve should not be dismantled. Limescale can be

removed from internal components by immersion in a suitable
de-scaling fluid.

4) When the components which can be maintained have been

checked, commissioning should be carried out again.

Min 1 2 3 4 5 6 7 Max

81 90 100 111 120 127 136 145 152

Pos.

27 32 38 44 49 53 58 63 67

M

I

N

M

A

X

7

1

2

3

Troubleshooting

Under normal operating conditions the Caleffi 2521 series mixing valve will provide a very
high level of performance. However, in some circumstances, where our maintenance plan is
not followed, the following problems may arise.

Symptom

Fluctuating mixed water
temperature

Erratic flow of water from
the valve

No flow of water from the
valve

Cause

a) Erratic supply temperatures

at the inlets of the valve.

b) Starvation of the water

supplies at the inlets
of the valve.

c) Incorrect commissioning

of the valve.

a) Insufficient water supplies.
b) Fluctuations in supply

pressures/temperatures.

c) Adverse effect created

by other draw off points
on the system.

a) In-line filters blocked.
b)

Insufficient supply pressures.

c) Debris obstructing valve

operation.

Corrective action

· Restore inlet conditions

within the limits of the
valve.

· Stabilize inlet supply
conditions.

· Clean filters.

· Restore inlet supplies.

· Clean debris or scale

from valve.

Caleffi North America, Inc.
3883 West Milwaukee Road
Milwaukee, WI 53208
T: 414.238.2360 F: 414.238.2366

CALEFFI

Safety

The thermostatic mixer must be installed by a licensed plumber in accordance

with national regulations and/or relevant local requirements.
If the thermostatic mixer is not installed, commissioned and maintained properly, according to the
instructions contained in this manual, it may not operate correctly and may endanger the user.
Make sure that all the connecting pipework is water tight.
When making the water connections, make sure that the mixer connecting
pipework is not mechanically over-stressed. Over time this could cause breakages, with
consequent water losses which, in turn, could cause harm to property and/or people.
Water temperatures higher than 100°F can cause serious burns.
During the installation, commissioning and maintenance of the thermostatic mixer, take the
necessary precautions to ensure that such temperatures do not endanger people.
In the case of highly aggressive water, arrangements must be made to treat the water before
it enters the thermostatic mixer, in accordance with current legislation. Otherwise the mixer
may be damaged and will not operate correctly.

Leave this manual for the user.