TUNDISH
300mm MIN.
DISCHARGE
ABOVE
FIXED
GRATING
FIXED
GRATING
TRAPPED GULLEY
METAL DISCHARGE
PIPE FROM TUNDISH
WITH CONTINUOUS
FALL
11
Sealed Primary Systems
Only ‘SS’ variants can be installed with a sealed primary
system. The ‘SS’ prefix is recorded on the Data Badge and
external packaging.
‘Sealed System’ models have an air separation fitting at the
back of the boiler. This also houses the water level safety switch
and connects the pressure relief valve and automatic air vent.
The installer must fit an external expansion vessel of adequate
expansion capacity. As a general guide systems of up to 7-9
radiators will need an 18 litre vessel; a 12 litre vessel may be
satisfactory for 5 radiator systems. The table below indicates
the size of vessel required for systems of different water
capacities.
For optimum performance after installation, Powermax and its
associated central heating system should be flushed in
accordance with the guidelines given in BS7593: 1992 –
Treatment of water in domestic hot water systems. Full
instructions are supplied with proprietary cleansers sold for this
purpose.
To help prevent both radiator corrosion and the possibility of
noise inside te boiler, it is recommended that Inhibitor is used.
To ensure that the correct amount of inhibitor is used add the
volume of the Powermax thermal store to your radiator and
pipework calculations as shown. It should be used in
accordance with the guidelines in the above standard and the
inhibitor manufacturer’s instructions.
Suitable inhibitors and flushing agents are available from
BetzDearbom and Fernox. Instructions for use are supplied with
these products.
Once the system has been fully flushed, complete the relevant
section in log book.
System Flushing
15mm SPUR
CH RETURN
FLEXIBLE HOSE
DOUBLE CHECK VALVE
18L EXPANSION VESSEL
CODE No. P105
STOP VALVE
MAINS WATER
540
380
190
135
DUCT
Fig. 11.2b
Fig. 11.3 Typical Discharge Pipe Arrangement
0
1
2
3
4
5
10 20 30 40 50 60
70
m
FLOW LITRES/MIN
PUMP PERFORMANCE AT 230V-50Hz
TEMPERATURE: 80 C
PUMP PERFORMANCE AT 230V-50Hz
TEMPERATURE: 80 C
10 20 30
120 240 360 480
20
40
60
80
100
8
16
24
32
40
PRESSURE LOSS (mbar)
PRESSURE LOSS (in. W.G.)
HYDRAULIC RESISTANCE OF THE PRIMARY STORE
FLOW (GALL/H)
HYDRAULIC RESISTANCE OF THE PRIMARY STORE
FLOW (GALL/H)
FLOW (LITRES/MIN)
Fig. 11.4
Volumes in litres
Expansion Powermax Radiators Total
Vessel 140 155
x Pipework System
140 155x Volume
12 80 100 117 97
max
197 max
16 80 100 182 162 max 262 max
18 80 100 215 195 max 295 max
An 18 litre expansion vessel part No P105 and wall bracket
P116 are normally supplied with sealed system boilers.
Connect the expansion vessel to the boiler central heating
return using a 15mm pipework spur, see Fig.11.2b. This spur
can also be used to connect a WRC approved filling loop.
Observe this sequence when installing loop: mains – stopvalve
– flexible hose – double check valve – boiler primary circuit.
NB: If the stopvalve is not in sight of the pressure gauge on the
Powermax, fit an additional gauge adjacent to the filling loop.
On ‘SS’ variants a pressure relief valve set at 3.0 bar is fitted at
the top of the thermal store. A 15mm pipe from the relief valve is
accessible at the front of the boiler. The tundish (supplied loose)
may be fitted within the casing or externally. The discharge pipe
from the tundish should be not less than 22mm diameter, and
must have a continuous fall to a visible and safe position.
See Fig 11.3.
Pipework from the tundish should fall vertically for 300mm and
then continue by continuous fall to a visible safe termination –
preferably below a fixed grating and above the water seal of a
trapped gulley. The tundish must be kept clear of electrical
devices.
Under normal working conditions no discharge will occur.
A multiple fault condition could cause a short discharge of
scalding water and steam. Adequate precautions should be
taken to prevent obstruction of the outlet and to minimise the
danger to persons (especially children) and property.
Section G3 of the Building Regulations Approved Document
should be consulted for full information.
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