MEGAFLO Eco Plus Solar User manual

Important
Please read & understand all these instructions before commencing installation.
Please leave this manual with the customer for future reference
MEGAFLO Eco Plus Solar Product Guide
MEGAFLO Eco Plus Solar
Unvented Hot Water Cylinders
800L -1000L

Contents
1. Introduction................................................................................................. 3
1.1 General .................................................................................................... 3
1.2 Symbols used............................................................................................ 3
1.3 Abbreviations ........................................................................................... 3
1.4 Liabilities................................................................................................... 3
2. Safety........................................................................................................... 4
2.1 General safety warnings ........................................................................... 4
2.2 Recommendations .................................................................................... 4
2.3 Specific safety instructions ........................................................................ 4
3. Technical specifications .............................................................................. 5
3.1 Technical data........................................................................................... 5
3.2 Dimensions and connections..................................................................... 8
3.3 Electrical diagram(s) .................................................................................. 7
4. Description of the product....................................................................... 11
4.1 General description................................................................................. 11
4.2 Operation principle ................................................................................. 11
4.3 Main components................................................................................... 11
4.4 Standard delivery .................................................................................... 11
5. Before installation .................................................................................... 13
5.1 Installation regulations............................................................................ 13
5.2 Installation requirements......................................................................... 13
5.3 Choice of location .................................................................................. 13
5.4 Transport ................................................................................................ 14
6. Installation ................................................................................................ 15
6.1 General .................................................................................................. 15
6.2 Water connections.................................................................................. 15
6.3 Electrical connections.............................................................................. 21
6.4 Filling the installation .............................................................................. 21
6.5 Solar Primary installation......................................................................... 22
7. Commissioning.......................................................................................... 23
7.1 General .................................................................................................. 23
7.2 Checklist before commissioning.............................................................. 23
7.3 Commissioning procedure ...................................................................... 23
8. Operation .................................................................................................. 24
8.1 General .................................................................................................. 24
9. Maintenance ............................................................................................. 25
9.1 General .................................................................................................. 25
9.2 Standard inspection & maintenance operations....................................... 25
10. Troubleshooting...................................................................................... 27
10.1 Fault finding ......................................................................................... 27
11. Decommissioning.................................................................................... 28
11.1 Decommissioning procedure................................................................. 28
12. Spare parts .............................................................................................. 28
12.1 Spare parts list ...................................................................................... 28
Benchmark checklist ..................................................................................... 30
Commissioning & service records ................................................................ 31
Guarantee...................................................................................................... 33
Unvented Hot Water Cylinder
2

1. Introduction
1.1 General
The following instructions are offered as a guide to the
user and installer.
The installation must be carried out by a competent
plumbing and electrical 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).
1.2 Symbols used
In these instructions, various risk levels are employed to
draw the user’s attention to particular information. In
doing so we wish to safeguard the user, avoid hazards
and guarantee the correct operation of the appliance.
DANGER
Risk of a dangerous situation causing serious
physical injury.
WARNING
Risk of dangerous situation causing slight
physical injury.
CAUTION
Risk of material damage.
 Signals important information.
1.3 Abbreviations
`T&P - Temperature & Pressure relief valve
`PRV - Pressure Reducing Valve
`Prv - Pressure relief valve
1.4 Liabilities
Manufacturers liability
Our products are manufactured in compliance with
the requirements of the various applicable European
Directives.
This appliance complies with the requirements of the CE
marking directive.
In the interest of UK customers, we are continuously
endeavouring to make improvements in product quality.
All the specifications stated in this document are therefore
subject to change without notice.
Our liability as the manufacturer may not be invoked in
the following cases:
`Failure to abide by the instructions on using the
appliance.
`Faulty or insufficient maintenance of the appliance.
`Failure to abide by the instructions on installing the
product.
Installer's liability
The installer is responsible for the installation and the
commissioning of the appliance. The installer must
respect the following instructions:
`Read and follow the instructions given in the manuals
provided with the appliance.
`Carry out installation in compliance with the
prevailing legislation and standards.
`Perform the initial start up and carry out any checks
necessary.
`Complete the commissioning checklist.
`Explain the installation to the user.
`If maintenance is necessary, warn the user of the
obligation to check the appliance and maintain it in
good working order.
`Give all the instruction manuals to the user.
Users liability
To guarantee optimum operation of the appliance, the
user must respect the following instructions:
`Read and follow the instructions given in the manuals
provided with the appliance.
`Call on qualified professionals to carry out installation
and initial start up.
`Get your fitter to explain your installation to you.
`Have your required checks and services done.
`Keep the instruction manuals in good condition and
close to the appliance.
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.
Children must be supervised to ensure they do
not play with the appliance.
Unvented Hot Water Cylinder
3

2. Safety
2.1 General safety warnings
2.2 Recommendations
2.3 Specific safety instructions
WARNING
`If water discharges from the
temperature/pressure relief valve on the
cylinder shut down the boiler. Do not
turn off any water supply. Contact a
competent installer for unvented water
heaters to check the system.
`Do not tamper with any of the safety
valves fitted to the system. If a fault is
suspected contact a competent installer.
`DO NOT bypass the thermal cut-out(s) in
any circumstances.
WARNING
`Only competent persons having received
adequate training are permitted to work
on the appliance and the installation.
`Do not tamper with any of the safety
valves or controls supplied with the
cylinder.
`Before any work, switch off the mains
supply to the appliance.
`Do not switch on if there is a possibility
that the water in the cylinder is frozen.
DANGER
This cylinder is unvented and as such becomes
pressurised when in operation. The combination
of pressurisation and hot water could lead to
serious physical injury if the safety instructions in
this manual are not adhered to.
CAUTION
Do not operate immersion heaters until the
cylinder has been filled with water.
WARNING
When handling the unit, take appropriate
precautions for the weight of the unit. Weights
can be found in section 3, table 1, page 5.
CAUTION
Annual maintenance is recommended by a
competent person.
Unvented Hot Water Cylinder
4

3. Technical specifications
3.1 Technical data
Solar:
800i Solar
1000i Solar
Max direct kW rating 6 6
Aux Coil surface area m² 1.5
Solar Coil surface area m² 3
Aux Coil rating (kW)
15l/min 25.1 26.6
30l/min 37.2 38.3
60l/min 47.5 45.8
Aux coil heat up time
(mins)
15l/min 64.2 74.5
30l/min 44.6 54.1
60l/min 34.2 42.8
Solar Coil Rating (kW) 30l/min 42.9 54.3
Solar coil heat up time
(mins) 30l/min 47.3 50.8
Pressure drop through
Aux coil (MPa)
15l/min 0.001
30l/min 0.002
60l/min 0.017
Pressure drop through
solar coil (MPa)
15l/min 0.002
30l/min 0.008
60/min 0.030
Heat loss (kWh in 24h) 2.74 3.33
Hot water capacity (volume of water drawn off >40°C) 681 850
Weight full (kg)
Weight empty (kg)
1017 1225
217 225
Max supply pressure 1.6MPa (16 bar)
Max design pressure 0.8 MPa (8 bar)
Max operating pressure (PRV) 0.35MPa (3.5 bar)
Max expansion vessel charge pressure 1.0MPa (10 bar)
Expansion relief valve setting 0.8MPa (8 bar)
T&P valve setting 1.0MPa (10 bar)/90°C
Expansion Prv set pressure 0.8MPa (8 bar)
Maximum primary pressure (Solar and Aux) (see Note 3) 1.0MPa (10 bar)
Notes:
1. Indirect cylinders tested in conformance with BS EN 12897:2006.
2. Heat up time from cold through 45°C, based on a flow temperature of 80°C +/- 2°C & normal volume.
3. The primary coil should not be exposed to more than 0.3MPa (3 bar) without the cylinder being full of water and
under the minimum working pressure.
Table 1: Technical data - Solar
Unvented Hot Water Cylinder
5

Table 3: General dimensions table - Solar 800l - 1000l
Item Connection 800l 1000l
ANA 1914 2327
BT&P/ 1/2" BSP 1503 1863
C1/2" & 1" BSP 1218 1538
D1 3/4" BSP 1138 1338
E1/2" BSP 1049 1249
F1 1/4" BSP 998 1198
G1 1/4" BSP 798 998
H1/2" BSP 710 710
I1 1/4" BSP 623 623
J1 1/4" BSP 448 448
K1" BSP 438 438
Figure 1: General dimensions - Solar 800l - 1000l
K
J
I
H
G
F
E
D
C
B
A
35°REF
40°REF 45°REF
30°REF
1111 REF
Ø1019 REF
OUTLET
2”BSP FEMALE
Unvented Hot Water Cylinder
6

NOTES: Control terminal numbering may differ from those shown.
Refer to instructions with controls selected.
A double pole isolating switch must be installed in the mains supply.
All earth connections must be connected back to the mains earth supply.
L
1
N
23
HTG
ON
DHW
ON LN
23
1
L
2
N
345 6 7 8 9 10
12 3 45 6 7 8 9 10
(Supply)
12 3
G
1
Br Bl
2
0GY
3
G
1
Br Bl
2
0
13 2
2
L
N
Programmer Boiler Pump
Zone valve (HTG)
Cylinder terminal block
Room stat
Zone valve (DHW)
(supplied)
Junction box
3
2
3
Schematic Wiring Diagram - Basic 2 x 2 Port Valve System
Figure 2: Schematic wiring diagram - basic 2 x 2 port valve system
L
1
N
23
HTG
ON
DHW
ON L
1
L
2
N
345 6 7 8 9 10
12 3 45 6 7 8 9 10
(Supply)
12 3
GWBl
2
0GY
3
G
1
Bl
2
0
L
N
Programmer Boiler Pump
Zone valve (HTG)
Cylinder terminal block
Room stat
Zone valve (DHW)
(supplied)
Junction box
NOTES: Control terminal numbering may differ from those shown.
Refer to instructions with controls selected.
A double pole isolating switch must be installed in the mains supply.
All earth connections must be connected back to the mains earth supply.
DHW
OFF
2
3
Schematic Wiring Diagram - 3 Port Mid Position Valve System. N.B. Must Be Used In Conjunction
With 2 Port Zone Valve Supplied
Br
13 2 N
23
3
2
Figure 3: Schematic wiring diagram - 3 port mid position system
Unvented Hot Water Cylinder
7

Figure 4: Immersion head assembly
Step 1:
- remove 4 retaining screws and lift lid o immersion heater
Step 2:
- remove 2 screws holding thermostatic controls and slide out
thermostat from stat pocket.
Step 3:
- Wire up immersion as per gures 6, page 11. If three phase
wiring chosen remove“Live” side buzz bar and t extra posts
(supplied) to L1, L2 & L3. (outer case and bracket removed for clarity)
Notes:
For single phase wiring use 4mm² H07RNF 3 Core
Use 2 x Two Pole 40A contactors for single phase
For 3 phase use Five core 1mm² Fused at max 10A
Use 2 x Three Pole 16A per pole contactors for 3 phase
For signal wire use 5 core 1mm² Fused at max 6A for thermostat
and thermal cut-out controls.
Disconnection time of the circuit protective device must be maintained
below the regulatory minimum (in the UK 5 seconds for xed equipment),
cable sizes may have to be higher depending on the characteristics of the
installation supply.
6kW immersion
Step 4:
Replace thermostatic controls taking care when inserting
the capillary bulbs into stat pocket and wire up as per
gure 6 or 7, page 9 .
Unvented Hot Water Cylinder
8

Neutral
Fuse
(not supplied)
Live
A
B
1
2
Fuse
(not supplied)
L1
L2
L3
Contactors
(not supplied)
Neutral
L1
Neutral
L2 L3
A
B
1
2
Single phase wiring schematic
3 phase wiring schematic
AB
1
2
Rotate spindle clockwise to increase
temperature and counter clockwise to
decrease the temperature
AB
1
2
AB
2
1
B-2 = Thermostat controls
A-1 = Thermal cut-out
Earth
Earth
L
A
B
S
T
1 2
3
Thermostat Controls
N
L
E
Neutral
Earth
Immersion Heater
Earth
Live
Immersion Heater
= Max temp
= Approx 65°
= Min temp
L
A
B
S
T
1 2
3
Thermostat Controls
Contactors
(not supplied)
Note:
The 2 external contactors must be approved
components certied 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.
L1
L2
L3 N
E
Figure 5: Single phase wiring schematic
Figure 6: Three phase wiring schematic
Unvented Hot Water Cylinder
9

Figure 7: Indirect wiring schematic
1 2 3C 2
High limit
thermostat
Control
thermostat
Common
(S/L)
Load (Demand Contact)
Satised
C
0
30
40
50
60
70
°C
Temperature
Adjustment
Thermal cut-out
reset under screw
head
Unvented Hot Water Cylinder
10

4. Description of the product
4.1 General description
This product is a purpose designed unvented water
heater. The unit has a stainless steel inner vessel, which
ensures an excellent standard of corrosion resistance. The
outer casing is a combination of resilient thermoplastic
mouldings and soft jacket. All products are insulated with
CFC free polyurethane foam (GWP 3.1) to give good heat
loss protection.
The unit is supplied complete with all the necessary safety
and control devices needed to allow connection to the
cold water mains. All these components are preset and
should not be tampered with.
4.2 Operation principle
The unvented cylinder is used to heat and store hot water
for use in commercial applications.
Depending on the model the water can be heated directly
using an element (supplied separately) or indirectly
through a coil in the unit using an external heat source
e.g. Gas, Oil or Electric.
To provide pressure to the tap or shower an unvented
unit uses the incoming mains water pressure. To do this
the cylinder is sealed and not vented. However, when the
volume of water is heated it expands and without any
room for expansion could cause the cylinder to rupture
and fail. To allow expansion of this heated water it is
important that an expansion vessel is used. This vessel is
pressurised and gives the heated water room to expand.
4.3 Main connections
See Figure 8: Main connections on page 12
4.4 Standard delivery
The delivery includes:
`Cylinder
`Literature pack
`Instructions (inc benchmark commissioning checklist
& service record)
`Cold water control pack
`Expansion vessel
`Combination valve (inc pressure reducing valve,
pressure relief valve and check valve)
`Tundish
`2 port zone valve (indirect only)
`Solar thermal cut-out
Unvented Hot Water Cylinder
11

T&P connection
Secondary return
Auxillary thermostat
Solar thermal cut-out
Cold inlet
Immersion heater
Hot outlet
Sensor pocket
Auxillary ow
Auxillary return
Primary ow
Primary return
Figure 8: Main Connections
Unvented Hot Water Cylinder
12

5. Before installation
5.1 Installation regulations
5.2 Installation requirements
Water supply
In an unvented system the pressure and flow-rate is
directly related to the incoming water supply. For this
reason it is recommended that the maximum water
demand is assessed and the water supply checked to
ensure this demand can be satisfactorily met.
`We suggest the minimum supply requirements
should be 0.15MPa (1.5 bar) pressure and 60 litres
per minute flow rate. However, at these values outlet
flow rates may be poor if several outlets are used
simultaneously.
`A 28mm cold water supply is recommended,
however, if a smaller supply exists, which provides
sufficient flow, this may be used (although more
flow noise may be experienced).
`The higher the available pressure and flow rate the
better the system performance.
`See table 1 on page 5 for cylinder operating
pressures. This is controlled by the cold water
combination valve assembly.
`The water supply must be of wholesome water
quality (Fluid Category 1 as defined by the Water
Supply Regulations 1999).
Outlet/terminal fittings (taps, etc.)
`The cylinder can be used with most types of terminal
fittings.
`Outlets situated higher than the cylinder will give
outlet pressures lower than that at the heater, a
10m height difference will result in a 1 bar pressure
reduction at the outlet.
`All fittings, pipework and connections must have
a rated pressure of at least 8 bar (dependant on
cylinder being fitted) at 80°C.
Limitations
The cylinder should not be used in association with any
of the following:
`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.
`Ascending spray type bidets or any other class 1 back
syphonage risk requiring that a type A air gap be
employed.
`Steam heating plants unless additional and
appropriate safety devices are installed.
`Situations where maintenance is likely to be neglected
or safety devices tampered with.
`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.
`In 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.
`In areas where the water supply contains chloride
levels that exceed 250mg/l.
5.3 Choice of location
The cylinder must be vertically floor mounted. Although
location is not critical, the following points should be
considered:
`The cylinder should be sited to ensure minimum
dead leg distances, particularly to the point of most
frequent use.
`Avoid siting where extreme cold temperatures will
be experienced. All exposed pipe work should be
insulated.
`The discharge pipework from the safety valves
must have minimum fall of 1:200 from the unit and
terminate in a safe and visible position.
`Access to associated controls and immersion heaters
must be available for the servicing and maintenance
of the system. Where these controls are installed
against a wall a minimum distance of 250mm must
be left.
`Ensure that the floor area for the cylinder is level and
capable of permanently supporting the weight when
full of water (see table 1, page 5 for weights).
WARNING
Installation of the appliance must be carried
out by a qualified engineer in accordance
with prevailing and national regulations as
listed below.
`Building Regulations G3
`The Building Standards (Scotland)
`The Building Regulations (Northern
Ireland)
`I.E.E Electrical Regs
`UK Water Regulations
Figure 9: Siting the unit if immersions not at the front
Min 600mm
Wall
Min 600mm
Unvented Hot Water Cylinder
13

Figure 10: Lifting the unit
Unvented Hot Water Cylinder
14

6. Installation
6.1 General
After reading the previous sections in this booklet and
choosing a good location for the unit please install,
paying attention to the following hydraulic, electrical and
commissioning sections.
Boiler selection
`The boiler should have a control thermostat and non
self-resetting thermal cut-out and be compatible
with unvented storage water heaters.
`Where use of a boiler without a thermal cut-out
is unavoidable a “low head” open vented primary
circuit should be used. The feed and expansion
cistern head above the cylinder should not exceed
2.5m.
`Can be a sealed system or open vented type -
maximum primary pressure 3 bar.
`The boiler cannot be vented through the cylinder.
6.2 Water connections
WARNING
`Under no circumstances should the
factory fitted temperature/pressure
relief valve be removed other than
by a competent person. To do so will
invalidate any guarantee or claim.
`The cold water combination valve
assembly must be fitted on the mains
water supply to the cylinder.
`No control or safety valves should be
tampered with or used for any other
purpose.
`The discharge pipe should not be blocked
or used for any other purpose.
`The tundish should not be located
adjacent to any electrical components.
Refer to the installation schematic (fig 11, below) for
details on the pipework layout. Specific details for the
discharge pipework layout is also provided in figure 14
on page 20.
`All pipe fittings are made via BSP female pipe
connections directly to the unit.
`A stopcock or servicing valve should be incorporated
into the cold water supply to enable the cylinder and
its associated controls to be isolated and serviced
T&P relief
valve
Solar
return
Solar
flow
Auxiliary
return
Auxiliary
flow
Mains water
supply
Expansion
vessel Balanced cold
water connection
Pressure reducing
valve
Pressure relief
valve
Inlet Drain cock Tundish Discharge pipe
Secondary
return
Figure 11: Typical installation schematic (not to scale)
Unvented Hot Water Cylinder
15

3.5 bar Pressure
reducing valve
Mains water in
8 bar Pressure
relief valve
28mm compression connections
To cylinder
Pressure relief
discharge
direction
direction
Pressure gauge
connections (one
each side)
(not supplied).
`The expansion vessel must be connected between
the cold water combination valve and the cylinder.
`The location of the expansion vessel should allow
access to recharge the pressure as and when
necessary.
`A suitable draining tap should be installed in the cold
water supply to the cylinder between the expansion
valve and the heater at as low a level as possible.
`It is recommended that the outlet point of the drain
pipework be at least 1 metre below the level of the
heater (this can be achieved by attaching a hose to
the drain tap outlet spigot).
Cold water control pack
CAUTION
`The expansion vessel pressure must be
set in accordance with the inlet pressure
set on the pressure reducing valve.
`Flush supply pipework 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 any warranty.
`The cold water control pack can be connected
anywhere on the cold water cylinder supply prior to
the expansion vessel.
`The control pack incorporates the strainer, check
valve, core unit and expansion relief valve.
`The valve can be fitted in any orientation to suit
the installation as long as the valve is installed with
the direction of flow arrows pointing in the correct
direction.
`The expansion relief valve should be installed with
the discharge pipework in either the horizontal
position or facing downwards.
`No other valves should be placed between the cold
water combination valve and the cylinder.
`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).
`Where discharge pipework is difficult to attain, the
local building control officer from the local council
should be sought for advice as this falls under G3
guidelines and is not down to the manufacturer for
unvented systems
`
Auxiliary circuit control
`The 2 port motorised valve supplied with the cylinder
MUST be fitted on the auxiliary flow to the cylinder
heat exchanger and wired such that in the event of
the cylinder overheating it will close the auxiliary
circuit.
`Auxiliary circulation to the cylinder heat exchanger
must be pumped; gravity circulation WILL NOT
WORK.
`It is recommended that an air bleed or automatic air
vent is fitted into the highest point of the system.
`Boiler flow temperature should be set to 82°
(maximum flow temperature to auxiliary heat
exchanger 89°C).
Figure 12: Cold water combination valve
Unvented Hot Water Cylinder
16

Secondary circulation
If secondary circulation is required it is recommended
that it be connected to the cylinder as shown (see fig.
13, below).
`The secondary return pipe should be in 28mm pipe
and incorporate a check valve to prevent backflow.
`A suitable WRAS approved bronze circulation pump
will be required.
`On large systems, due to the increase in system water
content, it may be necessary to fit an additional
expansion vessel to the secondary circuit. This should
be done if the capacity of the secondary circuit
exceeds 10 litres.
Pipe capacity (copper):
15mm O.D. = 0.13 l/m (10 litres = 77m)
22mm O.D. = 0.38 l/m (10 litres = 26m)
28mm O.D. = 0.55 l/m (10 litres = 18m)
Note: Plastic pipe capacities may be reduced due to
thicker wall sections.
In direct electric installations where a secondary circulation is required particular attention should be
paid by the installer to maintain the returning water
temperature (guidelines state that a minimum of 55°C
return temperature is advisable). Factors such as, but not
limited to, secondary circulation flow rates, minimising
heat loss of all secondary circuit pipework and timed
operation during periods of high demand are critical
to the correct operation and longevity of the heating
element(s) and thermostats.
Figure 13: Secondary circulation schematic
T&P relief
valve
Solar
return
Solar
flow
Auxiliary
return
Auxiliary
flow
Inlet Drain cock
Secondary
return
WRAS approved pump
(not supplied)
Unvented Hot Water Cylinder
17

Discharge
It is a requirement of Building Regulation G3 that any
discharge from an unvented system is conveyed to where
it is visible, but will not cause danger to persons in or about
the building. The tundish and discharge pipes should be
fitted in accordance with the requirements and guidance
notes of Building Regulation G3. The G3 Requirements
and Guidance section 3.50 - 3.63 are reproduced in the
following sections of this manual. For discharge pipe
arrangements not covered by G3 Guidance advice should
be sought from your local Building Control Officer. Any
discharge pipe connected to the pressure relief devices
(expansion valve and temperature/pressure relief valve)
must be installed in a continuously downward direction
and in a frost free environment.
Water may drip from the discharge pipe of the pressure
relief device. This pipe must be left open to the
atmosphere. The pressure relief device is to be operated
regularly to remove lime deposits and to verify that it is
not blocked.
G3 REQUIREMENT
“...there shall be precautions...to ensure that the
hot water discharged from safety devices is safely
conveyed to where it is visible but will not cause danger
to persons in or about the building.”
The following extract is taken from the latest G3
Regulations
Discharge pipes from safety devices
Discharge pipe D1
3.50 Each of the temperature relief valves or combined
temperature and pressure relief valves specied in
3.13 or 3.17 should discharge either directly or by way
of a manifold via a short length of metal pipe (D1) to a
tundish.
3.51 The diameter of discharge pipe (D1) should be
not less than the nominal outlet size of the temperature
relief valve.
3.52 Where a manifold is used it should be sized to
accept and discharge the total discharge from the
discharge pipes connected to it.
3.53 Where valves other than the temperature and
pressure relief valve from a single unvented hot water
system discharge by way of the same manifold that
is used by the safety devices, the manifold should be
factory tted as part of the hot water storage system
unit or package.
Tundish
3.54 The tundish should be vertical, located in the
same space as the unvented hot water storage system
and be tted as close as possible to, and lower than,
the valve, with no more than 600mm of pipe between
the valve outlet and the tundish (see g 13).
Note: To comply with the Water Supply (Water Fittings)
Regulations, the tundish should incorporate a suitable
air gap.
3.55 Any discharge should be visible at the tundish. In
addition, where discharges from safety devices may
not be apparent, e.g. in dwellings occupied by people
with impaired vision or mobility, consideration should
be given to the installation of a suitable safety device
to warn when discharge takes place, e.g. electronically
operated.
Discharge pipe D2
3.56 The discharge pipe (D2) from the tundish should:
(a) have a vertical section of pipe at least 300mm
long below the tundish before any elbows or bends in
the pipework (see g. 13); and
(b) be installed with a continuous fall thereafter of at
least 1 in 200.
3.57 The discharge pipe (D2) should be made of:
(a) metal; or
(b) other material that has been demonstrated to be
capable of safely withstanding temperatures of the water
discharged and is clearly and permanently marked to
identify the product and performance standard (e.g. as
specied in the relevant part of BS 7291).
3.58 The discharge pipe (D2) should be at least one
pipe size larger than the nominal outlet size of the safety
device unless its total equivalent hydraulic resistance
exceeds that of a straight pipe 9m long, i.e. for discharge
pipes between 9m and 18m the equivalent resistance
length should be at least two sizes larger than the
nominal outlet size of the safety device; between 18
and 27m at least 3 sizes larger, and so on; bends must
be taken into account in calculating the ow resistance.
See Fig 13, Table 3 and the worked example.
Note: An alternative approach for sizing discharge
pipes would be to follow Annex D, section D.2 of BS
6700:2006 Specication for design, installation, testing
and maintenance of services supplying water for
domestic use within buildings and their curtilages.
3.59 Where a single common discharge pipe serves
more than one system, it should be at least one pipe
size larger than the largest individual discharge pipe
(D2) to be connected.
3.60 The discharge pipe should not be connected to a
soil discharge stack unless it can be demonstrated that
the soil discharge stack is capable of safely withstanding
temperatures of the water discharged, in which case, it
should:
(a) contain a mechanical seal, not incorporating a
water trap, which allows water into the branch pipe
without allowing foul air from the drain to be ventilated
through the tundish;
(b) be a separate branch pipe with no sanitary
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Worked example of discharge pipe sizing
Fig. 13: shows a G1/2 temperature relief valve with a
discharge pipe (D2) having 4 No. elbows and length of
7m from the tundish to the point of discharge.
From Table 3:
Maximum resistance allowed for a straight length of
22mm copper discharge pipe (D2) from a G1/2
temperature relief valve is 9.0m.
Subtract the resistance for 4 No. 22mm elbows at 0.8m
each = 3.2m
Therefore the permitted length equates to: 5.8m
5.8m is less than the actual length of 7m therefore
calculate the next largest size.
Maximum resistance allowed for a straight length of
28mm pipe (D2) from a G1/2 temperature relief valves
equates to 18m.
Subtract the resistance of 4 No. 28mm elbows at 1.0m
each = 4.0m
Therefore the maximum permitted length equates to:
14m
As the actual length is 7m, a 28mm (D2) copper pipe will
be satisfactory.
appliances connected to it;
(c) if plastic pipes are used as branch pipes carrying
discharge from a safety device they should be either
polybutylene (PB) to Class S of BS 7291-2:2006 or
cross linked polyethylene (PE-X) to Class S of BS
7291-3:2006; and
(d) be continuously marked with a warning that no
sanitary appliances should be connected to the pipe.
Note:
1. Plastic pipes should be joined and assembled with
ttings appropriate to the circumstances in which they
are used as set out in BS EN ISO 1043-1.
2. Where pipes cannot be connected to the stack it
may be possible to route a dedicated pipe alongside or
in close proximity to the discharge stack.
Termination of discharge pipe
3.61 The discharge pipe (D2) from the tundish should
terminate in a safe place where there is no risk to
persons in the vicinity of the discharge.
3.62 Examples of acceptable discharge arrangements
are:
(a) to a trapped gully with the end of the pipe below a
xed grating and above the water seal;
(b) downward discharges at low level; i.e. up to
100mm above external surfaces such as car parks,
hard standings, grassed areas etc. are acceptable
providing that a wire cage or similar guard is positioned
to prevent contact, whilst maintaining visibility; and
(c) discharges at high level: e.g. into a metal hopper
and metal downpipe with the end of the discharge pipe
clearly visible or onto a roof capable of withstanding
high temperature discharges of water and 3m from
any plastic guttering system that would collect such
discharges.
3.63 The discharge would consist of high temperature
water and steam. Asphalt, roong felt and non-metallic
rainwater goods may be damaged by such discharges.
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Valve
Outlet Size
Minimum Size Of
Discharge Pipe D1
Minimum Size Of
Discharge Pipe D2
From Tundish
Maximum Resistance
Allowed, Expressed As A
Length Of Straight Pipe
(I.E. No Elbows Or Bends)
Resistance
Created By Each
Elbow Or Bend
G1/2 15mm
22mm
28mm
35mm
up to 9m
up to 18m
up to 27m
0.8m
1.0m
1.4m
G3/4 22mm
28mm
35mm
42mm
up to 9m
up to 18m
up to 27m
1.0m
1.4m
1.7m
G1 28mm
35mm
42mm
54mm
up to 9m
up to 18m
up to 27m
1.4m
1.7m
2.3m
Table 6: Sizing of copper discharge pipe (D2) for common temperature relief valve outlet sizes
Safety device
(e.g. Temperature
relief valve) Metal discharge pipe (D1) from
Temperature relief valve to tundish
Tundish
Discharge below
fixed grating
(Building Regulation
G3 section 3.61 gives
alternative points
of discharge)
Fixed grating
Trapped
gully
600mm maximum
300mm
minimum
Discharge pipe (D2) from tundish,
with continuous fall. See Building
Regulation G3 section 3.56,
Table 1 and worked example
Figure 14: Typical discharge pipe arrangement (extract from Building Regulation G3 Guidance Section 3.50)
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