A.O. Smith DURA-Power DRE-52 Guide

HOT WATER STORAGE DEVICES
United Kingdom / Ireland
MODELS DRE 52
DRE 80
DRE 120
INSTALLATION AND USER INSTRUCTIONS

2
Read this manual carefully
Warning
Read this manual carefully before using the device. Not reading this manual and not
following the instructions in this manual may lead to personal injuries and damage to the
device.
Copyright © 2009 A.O. Smith Water Products Company
All rights reserved.
Nothing from this edition may be copied, reproduced and/or made public by means of
press, photocopying or in any other way without the prior written permission of A.O. Smith
Water Products Company.
A.O. Smith Water Products Company reserves the right to change the specications as
mentioned in this manual.
Trademarks
All brand names mentioned in this manual are registered trademarks of the respective
suppliers.
Liability
A.O. Smith Water Products Company does not accept any liability for claims of third parties
as a result of incompetent use other than mentioned in this manual and in conformity with the
General Terms and Conditions as led with the Chamber of Commerce.
For further information see the General Terms and Conditions. These can be obtained
from us free of charge.
Although utmost care has been taken in ensuring a correct and, where necessary,
complete description of the relevant parts, the manual may contain errors and some things
may be unclear.
Should you still discover faults or things which are unclear, please inform us about this. It
helps us to further improve the documentation.
Additional information
If you have any remarks or questions concerning specic subjects related to the device,
please do not hesitate to contact:
A.O. Smith Water Products Company
P.O. Box 70
5500 AB Veldhoven
The Netherlands
Telephone: (free) 0870 - AOSMITH
0870 - 267 64 84
General: [phone]
Fax: [phone]
E-Mail: [email protected]
Website: www.aosmithinternational.com
For problems with respect to connections to electricity and water supplies, please contact
the supplier/installation engineer of your installation.
Note: “A.O.Smith Water Heaters” is tradingname of Advance Services (Sales) Ltd.Reg.

3
TABLE OF CONTENTS
1. GENERAL........................................................................................... 4
1.1 Device Description............................................................................................ 4
1.2 Regulation and Safety ..................................................................................... 5
1.2.1 Boil Dry Protection ............................................................................................ 7
1.2.2 Checking the Float Switch ................................................................................ 8
1.3 Technical description ........................................................................................ 9
1.4 Technical Data ................................................................................................ 10
2. FOR THE INSTALLER .....................................................................12
2.1 Installation procedures.................................................................................... 12
2.1.1 General Installation......................................................................................... 12
2.1.2 Water Connections ......................................................................................... 12
2.1.3 Electrical Connection ..................................................................................... 12
2.1.4 Electrical Diagrams......................................................................................... 13
2.2 Putting into operation...................................................................................... 17
2.2.1 Filling the Device ............................................................................................ 17
2.2.2 Putting Into Operation..................................................................................... 17
2.2.3 Putting out of Operation.................................................................................. 17
2.2.4 Temperature Regulation ................................................................................. 18
2.3 Maintenance ................................................................................................... 18
2.3.1 Sacricial anode ............................................................................................. 18
2.3.2 Descaling ........................................................................................................ 18
2.4 Steps When There is a Fault .......................................................................... 18
2.4.1 Water Temperature Not Good......................................................................... 19
2.4.2 Presumed Water Leakage .............................................................................. 19
2.4.3 Fault Table ...................................................................................................... 20
2.5 Spare Parts..................................................................................................... 20
3. FOR THE USER ...............................................................................21
3.1 Instructions for Use......................................................................................... 21
3.1.1 Filling the Device ............................................................................................ 21
3.1.2 Putting into operation...................................................................................... 21
3.1.3 Use ................................................................................................................. 21
3.1.4 Putting out of operation................................................................................... 22
3.2 Maintenance ................................................................................................... 22
3.3 Faults .............................................................................................................. 22
4. WARRANTY ..................................................................................... 23
4.1 General Warranty............................................................................................ 23
4.2 Tank Warranty................................................................................................. 23
4.3 Conditions of installation and use ................................................................... 23
4.4 Exclusions....................................................................................................... 24
4.5 Extent of the warranty..................................................................................... 24
4.6 Claims............................................................................................................. 24
4.7 No obligations for A.O. Smith other than those specied here. ...................... 24

4
1. GENERAL
1.1 Device Description
The structure and equipment for this
electrical heating device are in accordance
with the European standard for electrical
household devices (EN 60335-1:2002
+ A11:2004 + A1:2004 + A12:2006
+ A2:2006 en EN 60335-2-21:2003
+ A1:2005) The device thus meets
the European Directive for Electrical
Household Devices and has the right to
bear a CE mark.
The device is suitable to be used with
an operating pressure of up to 8 bar
(= 800 kPa). The tank is made of steel
plate, which has a glass lined coating
on the inside. The tank is also provided
with two sacricial anodes to give extra
protection against corrosion. A thick CFC
free polyurethane insulation layer, covered
with a steel casing, prevents unnecessary
heat loss. The device is fully lled with
water and continually starts under water
pipe pressure. When hot water is drawn off
from the device, it is immediately topped
up with cold. Incoloy heating elements are
used for good transfer of heat.
To create extra comfort in case of long
pipelines, circulating piping with a
circulating pump may be connected to
the piping. The circulating pipeline can be
connected to the cold-water supply.

5
Fig. 1 - regulation and safety
1.2 Regulation and Safety
For clarication see the diagram below:
(the image is an extract from the electrical
diagram further on)

6
3 relays (3) and a control current
transformer (5) are fed from the main
connection block (1). The main circuit
is protected by 30 Amp T fuses.
The transformer (400V to 24V) is
primarily secured with T0,2 A (4). A boil
dry protection mechanism (in the form of
a oat switch) (7) is included in the 24V
current control circuit. (The oat switch
is indicated diagrammatically. See boil
dry protection further on for more precise
explanation) The control current circuit is
closed if there is water in the device (oat
switch). In this case an auxiliary relay (6)
is used which in turn switches the relay
(3). The relays determine whether the
electrical elements are fed.
The elements are fed via the relay (3).
The wire goes to the maximum thermostat
(8) via the relays (2). The maximum
thermostat has a reset button. The output
from the maximum thermostat goes to the
regulating thermostat (9). The element
(10) is fed from the regulating thermostat.
During normal operation the regulating
thermostat (9) switches the element (10)
on and off. If a temperature of above
93°C occurs on an element the maximum
thermostat (8) locks the element. In order
to put the element back into operation the
reset button of the maximum thermostat
must be pressed in. The temperature
must have dropped by approximately
20°C before the maximum thermostat can
be reset.
If the temperature of the water above in
the tank exceeds 98°C for any reason,
the combined temperature and pressure
safety device (T&P valve) will open.
The safety control circuit will be interrupted
if the water level drops to below the oat
switch (7) or if the device is switched on
while empty.
The device is then switched off completely.
This is to prevent the elements coming
into operation while there is insufcient
water present in the device (boil dry
protection).
The safety fuses, 30 Amp T for 600 V can
be ordered retrospectively from A.O. Smith.

7
1.2.1 Boil Dry Protection
Fig. 2 - oat switch
The boil dry protection mechanism
consists of a oat switch which monitors
the water level approximately halfway
up the tank above the elements. If there
is insufcient water present in the tank,
then the oat (1) hangs down. If the tank
is lled with water then the oat is moved
upwards by the water. In the electrical
diagram the oat switch is reproduced
diagrammatically. The actual process
is as follows: the oat arm moves a
magnet with respect to the reed-contact
(2) which is located in the black plastic
tube at the end of the oat switch. The
movement of the magnet changes the
magnetic eld and the reed-contact is
closed.
The exposure height (3) of the reed
contact is very important.
This is 14 mm. This setting may not
be changed!
Explanation:
With an exposure height of 14 mm the
switch point is approximately halfway
along the stroke of the oat.
If the exposure height is set lower, then
the switch point shifts upwards. If the
exposure height is too small the contact
will no longer connect even if the oat
is completely above it. In this case the
device will not come into operation.
If the exposure height is set lower than
14 mm , then the switch point shifts
downwards. This means that the contact
will already connect upon a small
upwards movement of the oat. If the
exposure height is set too high then the
contact is permanently closed and the
safety mechanism does not work. This
means that the elements can come into
operation without there being sufcient
water present in the device. This will lead
to the elements burning out in a very
short time and short circuit and leakage.
So never change the exposure height.
The reed contact and the oat must
always be vertical. The arrow on the
clamping plate on the front must point
upwards. The oat switch is secured in
the tank with nut (5). By loosening nut
(4) the oat switch can be set vertically.
Nut (4)
is sealed with an o-ring with respect to
nut (5). The oat switch must be taken
out of the device as a complete unit
for checking or replacement. (The oat
cannot be passed through the opening in
nut (5).) For this purpose the device thus
has to be drained.

8
1.2.2 Checking the Float Switch
Switch off the feed voltage and remove
the fuses from the elements. In this
way the control circuit can be tested
without the elements being put into
operation. Drain the device until the
water is denitely below the oat switch.
If desired the oat switch can now be
removed for visual inspection. Check
the resistance of the contacts with a
multimeter and check whether the switch
point is situated approximately halfway
along the stroke of the oat. (For new
contacts this resistance is between 1
and 1.5 Ohms). Screw the oat switch
back into the tank and place it vertically.
Check the exposure height. Close the
door and connect the feed voltage. The
safety relays must not come in. (The
tautening and release of the safety
relays is clearly audible.) Now allow
water to ow into the device. If the water
presses the oat upwards, the oat
switch closes the control circuit and the
safety relays will tauten. Then drain the
device once again. The lowering of the
water level will lead to the oat switch
blocking the control circuit once again
and the safety relays will release. Repeat
this operation at least one time.
Switch off the feed voltage and t the
fuses of the elements again. Close the
door and reconnect the feed voltage.

9
1.3 Technical description
Fig. 3 - Measurements
Measurement Description 52 80 120
AHeight hot water connection 1460 1580 1600
BHeight of upper side of device 1420 1540 1570
DDiameter of boiler 560 640 750
EDepth 690 790 910
MHeight of drain valve 125 125 125
RHeight cold water supply 125 125 125
SHeight T&P connection 1230 1335 1380
1Cold water connection 1¼”-14NPT 1¼”-14NPT 1¼”-14NPT
2Hot water connection 1¼”-14NPT 1¼”-14NPT 1¼”-14NPT
3T&P connection ¾”-14NPT ¾”-14NPT ¾”-14NPT
4Drain plug connection ¾”-14NPT ¾”-14NPT ¾”-14NPT
All measurements are in mm (rounded up to 5mm).

10
1.4 Technical Data
Type DRE 52-9 DRE 52-18 DRE 52-36
Tank capacity litres 200 200 200
Number of elements - 3 3 6
Power 380V-3F kW 7.6 15.2 30.3
Power 400V-3F kW 8.4 16.8 33.6
Power 414V-3F kW 9.0 18.0 36.0
Heating time up to 60C*
(400/414V) min 83/78 42/39 21/19
Heating time up to 40C*
(400/414V) min 50/47 25/23 12/12
Tap capacity 1st hour 60°C**
(400/414V) litres 329/339 467/486 741/781
Tap capacity continuous 60°C**
(400/414V) litres/hour 145/155 289/310 578/619
Tap capacity 1st hour 40°C**
litres 549/565 778/810 1235/1300
Tap capacity continuous 40°C
litres/hour 241/258 482/516 963/1032
Weight kg 73 73 73
Type DRE 80-9 DRE 80-18 DRE 80-36 DRE 80-54
Tank capacity litres 300 300 300 300
Number of elements - 3 3 6 9
Power 380V-3F kW 7.6 15.2 30.3 45.5
Power 400V-3F kW 8.4 16.8 33.6 50.4
Power 414V-3F kW 9.0 18.0 36.0 54.0
Heating time up to 60C*
(400/414V) min 125/116 62/58 31/29 21/19
Heating time up to 40C*
(400/414V) min 75/70 37/35 19/17 12/12
Tap capacity 1st hour 60°C**
(400/414V) litres 425/435 563/582 837/876 1112/1170
Tap capacity continuous 60°C**
(400/414V) litres/hour 145/155 289/310 578/619 867/929
Tap capacity 1st hour 40°C**
litres 709/725 938/970 1395/1460 1853/1951
Tap capacity continuous 40°C
litres/hour 241/258 482/516 963/1032 1445/1548
Weight kg 110 110 110 110

11
Type DRE 120-9 DRE 120-18 DRE 120-36 DRE 120-54
Tank capacity litres 450 450 450 450
Number of elements - 3 3 6 9
Power 380V-3F kW 7.6 15.2 30.3 45.5
Power 400V-3F kW 8.4 16.8 33.6 50.4
Power 414V-3F kW 9.0 18.0 36.0 54.0
Heating time up to 60C*
(400/414V) min 187/174 93/87 47/44 31/29
Heating time up to 40C*
(400/414V) min 112/105 56/52 28/26 19/17
Tap capacity 1st hour
60°C** (400/414V) litres 569/579 707/726 981/1020 1256/1314
Tap capacity continuous
60°C** (400/414V) litres/
hour 145/155 289/310 578/619 867/929
Tap capacity 1st hour
40°C** litres 949/965 1178/1210 1635/1700 2093/2191
Tap capacity continuous
40°C litres/hour 241/258 482/516 963/1032 1445/1548
Weight kg 160 160 160 160
* From 10°C cold water
** After heating time up to 60°C from 10°C and assuming a tap efciency of 80%.

12
2. FOR THE INSTALLER
2.1 Installation procedures
The device may only be placed in a space
if this meets the valid national and local
regulations. This space must be frost free
or protected against frost.
The device may not be installed in damp
or wet areas. The insulation classication
of the device is: IP X1
2.1.1 General Installation
The installation shall be carried out by
a recognised installation engineer in
accordance with the generally and locally
applicable regulations for electrical and
water companies.
2.1.2 Water Connections
The maximum permissible operating
pressure of the device is 8 bar (= 800 kPa).
On the cold water side the device must
have a shut off valve and approved inlet
combination. The inlet combination must
be tted as closely as possible on the
device in accordance with the regulations.
The inlet combination must be allowed
to work regularly with the aim of avoiding
a blockage as a consequence of scale.
The drainage pipe of the inlet combination
must be tted in such a way that it
constantly slopes upwards. A stop valve
or non-return valve must never be tted
between the inlet combination and the
device.
During heating of the device, expansion
water (as a result of the temperature
increase) will drip into the drainage via the
overow of the inlet combination. This is
a normal occurrence. The dripping must
never be obstructed and/or blocked. The
drain must remain free at all times with
regard to the surroundings.
The device must be provided with a
temperature and pressure protection
mechanism (T&P valve). This is supplied
with the device. The overow of the T&P
valve must be connected onto the drain.
When there is a water pipe pressure
greater than 8 bar (= 800 kPa) an
approved reduction device must also be
tted.. When replacing an old device with
a new one the inlet combination must also
be renewed.
2.1.3 Electrical Connection
The electrical connection may only be
made by a recognised installation engineer
in accordance with the valid regulations of
the energy company. This device must be
provided with an all pole mains switch with
a contact separation of at least 3 mm if a
xed connection is used.
This appliance has been subjected in
the factory to a complete earthing-, high
voltage- and funtional test.
As a result of transport and/or use of the
appliance, screwed wire connections
may loosen from vibration.
For this reason, before the appliance
is put into operation, all screwed wire
connections must be checked to see if
they are secure.
Also during inspection and maintenance
activities, all wire connections must be
checked.
Warning: The device must be earthed.

13
2.1.4 Electrical Diagrams
The electrical circuit diagrams of the
various versions are given on the
next pages. The regulating and safety
sections are the same for all versions.
In principle the only difference is the
number of elements. An overview is
given in the table below.
Diagram A Diagram B Diagram C
Electrical diagram for 3
phase
Electrical diagram for 3
phase
Electrical diagram for 3
phase connection
connection with 3 elements connection with 6 elements with nine elements
Area of application:
DRE 52-9, DRE 52-18 DRE
52-36 DRE 80-54
Area of application:
DRE 80-9, DRE 80-18 DRE
80-36 DRE 120-54
Area of application:
DRE 120-9 DRE 120-18
DRE 120-36
Feed:
380-415 V AC 3F 50-60 Hz
Feed:
380-415 V AC 3F 50-60 Hz
Feed:
380-415 V AC 3F 50-60 Hz

14
Diagram A: Electrical diagram – 3 elements
Electrical diagram –
3 phases – 3 elements
A = Network connection
B = Fuses
C = Relay
D = Fuse
E = Transformer
F = Safety relay
G = Float switch
H = Maximum thermostat
K = Regulation thermostat
L = Electrical heating
element
X1 = Terminal block
1 = Black / Zwart / Schartz / Noir
2 = Red / Rood / Rot / Rouge
3 = Blue / Blauw / Blau / Bleu
4 = Brown / Bruin / Braun / Brun
5 = Yellow / Geel / Gelb / Jaune

15
Electrical diagram –
3 phases – 6 elements
A = Network connection
B = Fuses
C = Relay
D = Fuse
E = Transformer
F = Safety relay
G = Float switch
H = Maximum thermostat
K = Regulation thermostat
L = Electrical heating
element
X1 = Terminal block
1 = Black / Zwart / Schartz / Noir
2 = Red / Rood / Rot / Rouge
3 = Blue / Blauw / Blau / Bleu
4 = Brown / Bruin / Braun / Brun
5 = Yellow / Geel / Gelb / Jaune
Diagram B Electrical diagram – 6 elements

16
DIAGRAM C: Electrical diagram – 9 elements
Electrical diagram –
3 phases – 9 elements
A = Network connection
B = Fuses
C = Relay
D = Fuse
E = Transformer
F = Safety relay
G = Float switch
H = Maximum thermostat
K = Regulation thermostat
L = Electrical heating
element
X1 = Terminal block
1 = Black / Zwart / Schartz / Noir
2 = Red / Rood / Rot / Rouge
3 = Blue / Blauw / Blau / Bleu
4 = Brown / Bruin / Braun / Brun
5 = Yellow / Geel / Gelb / Jaune

17
2.2 Putting into operation
2.2.1 Filling the Device
1. Fit the drain valve and check
whether it is closed.
2. Open cold water valve to the boiler
and open all valves at hot water
drainage points for bleeding. The
device is lled as soon as cold water
ows at all drainage points.
3. Reclose all valves at hot water
drainage points.
2.2.2 Putting Into Operation
The device must NEVER be put into
operation with a closed cold water feed.
1. Check whether the device is lled
with water and whether all electrical
connections to the device are also
actually properly connected.
2. Check whether the cold water inlet is
open.
3. Check whether the device is free of
voltage. Open the door and remove
styrofoam cover located beneath
it. Now the regulating thermostats
are accessible. The regulating
thermostats can now be set to the
desired temperature by turning the
selection knob with a screwdriver.
4. Set the desired temperature on
the regulating thermostat (see
table). When leaving the factory the
temperature is set at 60°C.
Temperature in °F Temperature in °C
120 49
130 54
140 60
150 66
160 71
170 77
180 82
5. Ret the insulation and close the
door.
6. In the case of a xed connection
turn on the mains switch or in other
cases place the connector in the
stop contact. The device is now
switched on and it will continue to
work automatically.
2.2.3 Putting out of Operation
1. For short periods: take the connector
out of the stop contact or where
there is a xed connection switch off
the mains switch.
2. In addition to the operations in
point 1, for longer periods it is
recommended to shut off the water
feed pipe in connection with the
danger of frost and once the device
has cooled down, to drain off the
water by connecting a drainage hose
to the drainage valve and opening
it. Also open the closest hot water
drainage point for ventilating the
tank. Take care that the feed pipe
and inlet combination cannot freeze.
Drain the feed pipe as necessary
and check whether all other pipes
are empty.

18
2.2.4 Temperature Regulation
The device is continuously under
water pipe pressure (maximum 8 bar
(=800 kPa)). Cold water may be fed
if hot water is being consumed. The
regulating thermostat switches the feed
automatically. That means that if the
thermostat measures a temperature
lower than the set temperature, then it
closes the electrical circuit so that an
electrical current is conducted through
the heating element. As soon as the
desired temperature is reached the
thermostat breaks the contact once
again. When there are high water
temperatures, scaling in the device
occurs. Therefore it is recommended
to allow the temperature setting to stay
at 60°C so that less scale is formed.
A maximum thermostat is installed
above each regulating thermostat
which shuts off the current feed to the
element permanently (locking) at a
water temperature of 93°C. In order to
put the element back into operation the
reset button of the maximum thermostat
must be pressed in. If the temperature
climbs above 98°C the temperature and
pressure valve tted open for safety
reasons.
2.3 Maintenance
The boiler must be tested and cleaned
by a recognised installation engineer
at least once per year so that good
operation can be guaranteed. During
maintenance the device must never be
under voltage.
2.3.1 Sacricialanode
The life of the anodes is determined
by the quality and the quantity of water
owing through the device. It is thus
recommended that the anodes are
checked every year.
1. Close the stop valve in the cold
water feed pipe.
2. Open up the nearest hot-water tap
so that the water pressure in the
boiler and pipeline drops.
3. Loosen the anode using a correct
spanner.
4. Check the anode and replace if this
is tarnished above 60%.
5. Replace the anode in a water-tight
way.
If it is necessary to replace the anode,
it must be replaced with one of the
same type. The type of anode can be
established via the device type and the
complete serial number.
2.3.2 Descaling
Scaling depends on the water condition
and the water demand. Besides, more
scale deposit will be formed in the device
at high temperatures than at lower
temperatures. A temperature setting of 60
ºC is recommended to ensure low scale
deposit. Descale using the appropriate
agents. A descaling instruction is available
for detailed information.
2.4 Steps When There is a
Fault
Warning:
Always ensure that the device is
completely free of voltage before the
door is opened!

19
In normal operation the safety relays
are in a taut condition. When the feed
voltage is switched off these drop. This
is clearly audible. If the switching on
and off of the relay is not audible, then
check whether feed voltage is present
and the fuses of the feed are in order. If
this is in order then check (with a voltage
free device!) the following (see also 1.2
Regulation and Protection):
1. Check the fuse of the transformer in
the current circuit
2. Check whether the water level in the
device is sufciently high (boil dry
protection).
4. Check whether the fuses of the
heating elements are in order.
5. Check whether the maximum
thermostats of the elements have
connected by pressing in the reset
buttons of all thermostats.
6. Close the door and reconnect the
feed voltage. If the safety relays do
not connect or if the device does
not function properly then engage a
repair service.
Explanation
All devices are made with a number
of maximum thermostats which break
the circuit when the water temperature
is too high (93°C). These maximum
thermostats can only be reset again
once the temperature has dropped
20°C. Then the regulating thermostat
must be examined: if this is set at too
high a temperature, the thermostat must
be set lower. If it is not set to a high
temperature it is probably defective and
in this case it must be replaced. Check
the fuses as well and replace them if
necessary. The fuses can be ordered
through A.O. Smith.
2.4.1 Water Temperature Not
Good
1. Check the settings of the regulating
thermostat.
2. Check for leaks or open valves.
3. Check the hot water temperature
right by the pipe leading out from the
device in order to be sure that a too
low water temperature is not caused
by the mixing of cold water into the
pipe system.
4. Check if the wiring has been properly
connected.
5. Check whether the voltage between
the three phases is 380-415 V.
6. Check whether the need for hot
water is greater than initially
calculated.
2.4.2 Presumed Water Leakage
1. Check whether the drain valve is
fully closed.
2. Check whether all water connections
are water tight.

20
2.5 Spare Parts
Prior to ordering spare parts it is
important to note the device type and
the full serial number of the device. This
information is given on the plate which
is afxed to the outside of the door. Data
for spare parts can be established by
using this information.
2.4.3 Fault Table
Fault Cause Solution
Insufcient or
no hot water
Temperature set too low Set regulating thermostats
higher.
Maximum thermostats break the
circuit.
Press in reset button.
Connector is not seated in stop
contact, mains switch is off or
fuses are broken.
Check the relevant parts.
Cause cannot be ascertained. Switch off device and ask for
help from technical support
Leakage Insufcient sealing of the
water connections.
Tighten the screw thread
connections.
Leakages from other water
devices or pipes nearby.
Trace the cause