REMEHA Flexistor 400 User manual

7038477_issue _01
Installation Manual
Unvented Flexistor Water Heaters Installation & Servicing Instructions

Important
Please read & understand all these instructions before commencing installation.
This cylinder range does not incorporate an internal heat exchanger.
Please leave this manual with the customer for future reference.
page 1
Contents
Product Specification
Introduction
General requirements
THE BENCHMARK™ SCHEME
Checklist
Storage and handling
Technical data
ErP data information
Immersion allocation table
Thermostat control schematics
Wiring Schematics
Limitations
Water supply
Installation & Commissioning
General Installation
Cold Water Supply
Secondary circulation and De-Stratification
Discharge Pipe work
Direct Model
Commissioning
Maintenance & Servicing
Maintenance requirements
Clean the strainer

Fault finding
Servicing
Spares
Accessories
Spares drawings
Benchmark check list
Service Record
Warranty
Lifetime Warranty Terms and Conditions
THE BENCHMARK™ SCHEME
Benchmark™ places responsibilities on both manufacturers and installers. The purpose is to ensure that customers are provided with the
correct equipment for their needs, that it is installed, commissioned and serviced in accordance with the manufacturer's instructions by
competent persons and that it meets the requirements of the appropriate Building Regulations. The Benchmark™ Checklist can be used to
demonstrate compliance with Building Regulations and should be provided to the customer for future reference. Installers are required to carry
out installation, commissioning and servicing work in accordance with the Benchmark™ Code of Practice which is available from the Heating
and Hotwater Industry Council who manage and promote the Scheme. Visit www.centralheating.co.uk for more information.
IMPORTANT NOTE TO USER: PLEASE REFER TO THE USER GUIDE SECTION ON PAGES 34 FOR IMPORTANT
INFORMATION WITH RESPECT TO THE BENCHMARK SCHEME
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Product specification
Introduction

Congratulations on your purchase of a Remeha Flexistor unvented water heater. The Remeha Flexistor products are manufactured in the UK
from top quality materials and meets all the latest relevant safety and constructional standards. The high grade Duplex stainless steel cylinder
offers exceptional strength and corrosion resistance which is backed by a 30 year warranty* Its performance and insulation levels exceed the
latest requirements of Building Regulation Part L.
The Remeha Flexistor unvented water heater can be fed directly from the cold water mains supply to the property without the need for separate
feed cisterns or vent pipes. It is supplied complete with all its necessary inlet and safety controls.
The Remeha Flexistor cylinder range all require a separate expansion vessel to accommodate any expanded water.
General Requirements
IMPORTANT: Please read and understand this product guide before installing the Remeha Flexistor water heater. Incorrect installation may
invalidate the warranty*.
The Remeha Flexistor must be Installed, Commissioned and Maintained by a competent installer in accordance with Building Regulation
G3 (England and Wales), Technical Standard P3 (Scotland) or Building Regulation P5 (Northern Ireland) and the Water Fitting Regulations
(England and Wales) or Water Byelaws (Scotland).
* See Terms and Conditions of warranty
THIS APPLIANCE CAN BE USED BY CHILDREN AGED FROM 8 YEARS AND ABOVE AND PERSONS WITH REDUCED
PHYSICAL, SENSORY OR MENTAL CAPABILITIES OR LACK OF EXPERIENCE AND KNOWLEDGE IF THEY HAVE
BEEN GIVEN SUPERVISION OR INSTRUCTION CONCERNING USE OF THE APPLIANCE IN A SAFE WAY AND
UNDERSTAND THE HAZARDS INVOLVED. CHILDREN SHALL NOT PLAY WITH THE APPLIANCE. CLEANING AND USER
MAINTENANCE SHALL NOT BE MADE BY CHILDREN WITHOUT SUPERVISION
WARNING: Do not switch on if there is a possibility that the water in the heater is frozen.
Also:
#Water may drip from the discharge pipe of the pressure-relief device and this pipe must be left open to the atmosphere; (see here for more
details)
#The pressure-relief device is to be operated regularly to remove lime deposits and to verify that it is not blocked; (see here for more
details)
#How hot water can be drained. (see here for more details)
#A discharge pipe connected to the pressure-relief device is to be installed in a continuously downward direction and in frost free
environment; (see here for details)
#Details on how to set the temperature controls for immersion heaters can be found here.
Note: This Remeha Flexistor cylinder needs a minimum 100L/min water supply at open outlet.
Important Notice:
When installed with the KIWA approved unvented kit Remeha Flexistore cylinders are approved as meeting current water regulations.

To satisfy these regulations when the kit is not supplied it will be required that the installer ensures that all of the system components
meet the required standards.
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Checklist (if purchased through Heatrae Sadia)
Before commencing installation check that all the components for your Remeha Flexistor unit are contained in the package.
The following components are supplied as standard with your Remeha Flexistor unit:
Commercial
Cylinder
Volume (ltr)
Pressure
Reducing Valve Pressure Relief Valve Single Check Valve
400 - 500 1" Integrated inlet control valve
800 1.25" (1.5 - 6 bar) 1" x 1.25" (8 bar) 1.25"
1000 1.25" (1.5 - 6 bar 1" x 1.25" (8 bar 1.25"
1250 - 1450 1.5" (1.5 - 6 bar 1" x 1.25" (8 bar 1.5"
2000 - 2500 2" (1.5 - 6 bar 1.25" x 1.5" (8 bar 2"
Table 1: Cold Water Inlet Control Kit (depending on model)
Commercial
Cylinder
Volume (ltr)
Expansion Vessel
Size (ltr) Mounting Kit Weights
400 - 500 60 Floor Mounted 12kg
800 100 Floor Mounted 17kg
1000 - 1250 150 Floor Mounted 24kg
1450 200 Floor Mounted 38.5kg
2000 - 2500 300 Floor Mounted 41kg
Table 2: Expansion Vessel Sizing
#Factory fitted Temperature & Pressure Relief Valve, set at 90°C / 1 MPa (10bar). Connection size 1 1/4" BSP male to cylinder and 1 1/4"
BSP female outlet.
#Tundish 1 1/4" inlet, 1 1/2" outlet
#Isolating Valve (2")
#1" Drain Valve.

#All connections BSP female.
Notes:
1" Integrated inlet control valve is not assembled.
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Storage and Handling
Please take care when handling a packaged Remeha Flexistor. The unit is heavy and must only be moved manually within safe working
practices. If the unit is to be stored before installation, it must be placed on a secure, level surface and in a dry, frost free environment.
Precautions to be carried out prior to commencement of work:
1. Tidy area ensuring there is safe access and egress to installation place, free from trip hazards.
2. Be aware of other people who may be in the area
3. Operate any machinery in accordance with training and operating instructions
4. Visually inspect the equipment prior to use, do not use damaged equipment.
5. Safe working practices are adopted for manual handling of appliances/parts
6. Correct PPE to be worn.
The Remeha Flexistor unit must be vertically floor mounted. It can be placed anywhere convenient provided the discharge pipe(s) from its safety
valves can be correctly installed. Areas that are subject to freezing must be avoided. Ensure that the floor is level and of sufficient strength to
support the "full" weight of the unit when filled with water (refer to Table 5 for unit weights). Pipe runs should be kept as short as possible for
maximum economy. Access to associated controls, immersion heaters and indirect controls should be possible for servicing and maintenance of
the system.
To aid installation, the Remeha Flexistor is provided with lifting points located at the top of the unit. To access the lifting eyes please remove the
red outlet grommet and the top cover. The weights of the units are noted on Table 5.

FIGURE 1: Lifting
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Technical data (Indirect models in conformance with BS EN 12897:2016)
Maximum mains water supply pressure 2.5MPa (25 bar)
Operating pressure/PRV 0.60MPa (6. bar)
Expansion vessel pressure 1.0MPa (10 bar max)
Expansion relief valve setting 0.8MPa (8 bar)
Maximum design pressure 0.80MPa (8 bar)
T&P relief valve setting 1.0MPa/90 °C (10 bar)
Immersion heater rating (a.c. supply only) single phase 6kW & 9kW 50/60Hz ~
Immersion heater rating (a.c. supply only) 3 phase
(See Accessories for full range) 12kW - 54kW 50/60Hz ~
Storage weights (empty and full) See Table 4
See Table 6
ErP data
ErP Data
Model(s) 400 500 800 1000 1250 1450 2000
Energy efficiency class B C C C C C C
Standing loss W 72.0 89.0 114.0 139.0 150.0 163.0 179.0
Storage volume V in Litres 400 500 800 1000 1250 1450 2000
Table 3: ErP Data Information
Technical parameters in accordance with European Commission regulations 814/2013 and 812/2013
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FIGURE 2: Flexistor Dimensions
Connection 400 -
500L Connection 800 - 1000L Connection 1250 - 1450L Connection 2000 - 2500L
A 2" BSP 471 471 2" BSP 502 502 2" BSP 541 541 2" BSP 591 591
B ½" BSP 616 616 ½" BSP 744 744 ½" BSP 783 783 ½" BSP 833 833
C ½" BSP 1138 1416 ½" BSP 1502 1897 ½" BSP 1466 1721 ½" BSP 1493 1886
D ½" BSP 1001 1191 ½" BSP 1263 1687 ½" BSP 1326 1536 ½" BSP 1376 1626
E ¾" BSP 1138 1416 1¼" BSP 1502 1897 1 ¼" BSP 1466 1721 1 ¼" BSP 1493 1886
F N/A 872 872 N/A 1024 1024 N/A 1224 1224 N/A 1470 1470
G 2" BSP 754 754 2" BSP 880 880 2" BSP 1042 1042 2" BSP 1077 1077
H N/A 1535 1804 N/A 1906 2301 N/A 1936 2253 N/A 2014 2419
Table 4: Flexistor Dimensions
page 7

FIGURE 3: Flexistor Connections
NOTE: All connections BSP female threads
Unit Weight (kg)Nominal
Capacity
(Litres) Empty Full
400 99 499
500 100 600
800 160 960
1000 180 1180
1250 297 1547
1450 304 1754
2000 415 2415
2500 421 2921
Table 5: Cylinder Weights
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Nominal
Capacity
(Litres)
Per Day
(kWh/24h) Per Year (kWh/24h)
400 1.72 627
500 2.14 781
800 2.74 1000
1000 3.33 1215
1250 3.60 1314
1450 3.90 1423
2000 4.30 1569
2500 4.50 1642
Table 6: Standing heat-loss
Testing is carried out to BS EN12897:2016

Maximum kW ratingsNominal
Capacity
(Litres) Lower boss Upper boss Total kW
400 30 9 39
500 45 12 57
800 45 18 63
1000 45 36 81
1250 54 30 84
1450 54 36 90
2000 54 36 90
2500 54 36 90
Table 7: Maximum kW ratings for auxiliary heating supply
Heat-Up Times Heat-Up TimesNominal
Capacity
(Litres) Maximum kW Heat-up
Time (mins)
Nominal
Capacity
(Litres) Maximum kW Heat-up
Time (mins)
400 39 32 1250 84 47
500 57 28 1450 90 51
800 63 40 2000 90 70
1000 81 39 2500 90 87
Table 8: Auxiliary heat up times based on maximum immersion input per cylinder
Notes:
Times based on nominal volume
Times base on 45°C temperature rise
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Immersion allocation

Table 9: Immersion allocation
Note:
The Immersion (s) are not factory fitted .
Thermostat Cut-out
All immersion2000heaters are fitted with a thermostat which is fitted in the centre oft he heater plate and a cut-out which is fitted to the side
of the thermostat. These MUST be wired in series with the operating coil circuit of the contactor (not supplied). See figures 4 below and
figures 5 & 6.
Maximum working temperature is 80°C/176°F. In very hard water areas limit to 60/65°C (140/150°F)
For optimal working conditions the thermal cut-out should be set to 80°C (factory set, if the seal is broken it may invalidate your warranty) and
the thermostat should be set to 70°C max. If the thermostat is set above 70°C there could be instances nuisance tripping of the thermal cut-out.
Notes:
The 2 external contactors must be approved components certified for 10,000 cycles of operation for the contactor controlled by the thermostat
and at least 30 for the contactor controlled by the none self-resetting thermal cut-out.

FIGURE 4: Thermostat and thermal cut-out settings
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Wiring Schematic
Single phase wiring schematic

Note: The 2 external contactors must be approved components certified for 10,000 cycles of operation for the contactor controlled by the
thermostat and at least 30 for the contactor controlled by the non-self-resetting thermal cut-out.
FIGURE 5: Single phase wiring schematic
3 phase wiring schematic

FIGURE 6: 3 phase wiring schematic
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Limitations
#The Remeha Flexistor unvented water heater should not be used in any of the following instances:
#Solid fuel boilers or any other boiler in which the energy input is not under effective thermostatic control unless additional and
appropriate safety measures are installed.
#Gravity circulation primaries.
#Steam heating plant unless additional and appropriate safety devices are installed.
#Ascending spray type bidets or any other Class 5 back syphonage risk requiring that a Type AA, AB, AD or AG air gap be employed.
#Water supplies that have either inadequate pressure or where the supply may be intermittent.
#Situations where it is not possible to safely pipe away any discharge from the safety valves.
#Areas where the water consistently contains a high proportion of solids, e.g. suspended matter that could block the strainer, unless
adequate filtration can be ensured.
#The installation must be carried out in accordance with the relevant requirements of the appropriate Building Regulations: either The
Building Regulations (England), The Building Regulations (Scotland) or Building Regulations (Northern Ireland), The Water Fittings
Regulations (England and Wales) or Water Byelaws (Scotland).
Water supply
Bear in mind that the mains water supply to the property will be supplying both the hot and cold water requirements simultaneously. It is
recommended that the maximum water demand be assessed and the water supply checked to ensure this demand can be met. A minimum flow
rate of 100l/min is required for the Remeha Flexistor range of cylinders
NOTE: A high mains water pressure will not always guarantee high flow rates.
Wherever possible the main supply pipe should be in 2". The minimum mains water supply requirements should be 0.15 MPa (1.5 bar) working
pressure and minimum 100 litres per minute flow rate. At these values outlet flow rates may be poor if several outlets are used simultaneously,
the higher the available pressure and flow rate the better the system performance will be.
The water supply must be of wholesome water quality (Fluid Category 1 as defined by the Water Supply Regulations 1999). The Remeha
Flexistor is to be used for the storage of wholesome water (max. 250mg/l chloride).
Note: In hard water areas it is recommended that service intervals are reduced to monitor scale build up on the immersion heaters.
Water container:
Duplex stainless steel. 100% pressure tested to 2.25 MPa (22.5 bar).
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Installation & Commissioning
General installation

Pipe fittings
All pipe connections to the Remeha Flexistor are made via BSP female parallel threaded pipe connection directly to the unit.
Cold water supply
A 2" cold water supply is recommended, however, if a smaller supply exists which provides sufficient flow this may be used. More flow noise
may be experienced from small bore pipes due to the increased water velocity through them. A minimum flow rate of 100l/min is required for
the Remeha Flexistor range of cylinders
High flow cold water control pack (Low and high pressure)
The control pack consists of a pressure reducing valve with integral strainer, check valve, core unit and expansion relief valve. The pressure
settings are adjustable for the low or high pressure valve sets. For the "low" pressure valve set the pressure reducing valve can be set between 1.5
and 6 bar. For the "high" pressure valve set the pressure can be set between 5 and 10 bar. For optimum performance the following installation
instructions should be complied with.
Note: The expansion vessel pressure must be set in accordance with the inlet pressure set on the pressure reducing valve by the installer. Set the
Expansion Vessel pressure before pressurising the cylinder.
Installation
Flush supply pipe work before connection to remove all flux and debris prior to fitting the inlet controls. Failure to do this may result in
irreparable damage to the controls and will invalidate the warranty.
The pressure reducing valve can be fitted in any orientation to suit the installation as long as it is fitted in the correct flow direction. Check the
flow arrows on the side of the body.
The expansion relief valve should be installed with the discharge pipe work in either the horizontal position or facing downwards, if the
discharge pipe is facing upwards debris may be deposited on the seat of the valve when in operation.
The blank plastic plugs in the body of the pressure relief valve are pressure gauge connections to enable pressure monitoring to be carried
out, should the system develop a fault. It is recommended that these be accessible (the pressure reducing valve has two - only one need be
accessible).
Expansion relief discharge pipe work must be connected to a safe visible discharge point via a tundish and the pipe work must have a continuous
fall. If site conditions allow, the expansion relief discharge pipe work can be connected to the T&P valve discharge pipe work before the tundish.
Pressure reducing valve
The pressure reducing valve can be connected anywhere on the cold water mains supply prior to the Remeha Flexistor unit. There is no
requirement to site it close to the unit, it can be located at a point where the mains supply enters the premises if this is more convenient but
you must install a non-return valve just after the reducing valve for ease of maintenance. The pressure reducing valve incorporates a adjustable
pressure reducer / strainer. The valve can be fitted in any orientation to suit the installation, however, ensure that the valve is installed with the
direction of flow arrows (stamped on the side of the brass body) pointing towards the Remeha Flexistor cylinder
page 13