APR 2018
8
Hot Water Energy Storage
Unvented Cylinders
GB & NI
Installation & Maintenance Instructions for an unvented
hot water cylinder with external thermal expansion
INSTALLATION INSTRUCTIONS (CONTINUED)
SECONDARY CIRCULATION CONNECTION
This can be used with secondary circulation. An appropriate
WRAS approved bronze or stainless steel circulator should
be used in conjunction with a non-return valve to prevent
backflow.
On large secondary circulation systems it may be necessary
to incorporate an extra expansion vessel into the circuit
to accommodate the increased system water volume.
Secondary circulation should be minimised or avoided on
Direct electrically heated units, especially if the unit is being
used on an off-peak electricity tariff.
A secondary return boss is fitted as standard on 210, 250 &
300 ltr units. On smaller sizes, use a swept tee to connect
into the cold feed pipe above the drain.
IMMERSION HEATERS
Only immersion heaters with a thermal cut-out that comply
with BS EN 60335-2-73 may be used. To help ensure this, the
immersion heaters have a special 13/4” thread. They are rated
at 3kW at 240V and are of a low noise Incoloy construction.
They have both a thermostat and a high limit cut-out.
Please order the correct replacement via ourselves; fitting
non-approved immersions may affect your guarantee. When
fitting, ensure the ‘O’ ring is positioned correctly on the head
of the immersion heater and lubricate before fitting. Fit it by
hand until almost home then tighten gently, as the ‘O’ rings
will seal easily. Electrical supply refer to page 4.
Do not operate the immersion heater/s until the cylinder is
full of water.
Do not operate the immersion heater/s if any sterilisation
liquid is in the cylinder as this will cause premature failure.
If the water quality is aggressive or the cylinder is to be used
on a system with a heat pump that struggles to achieve the
set temperature, we recommend exchanging the immersion
heater for a titanium element.
Note:
Immersion heaters should never be used as the
primary heat source except for the lower immersion on a
direct cylinder.
Selected cylinder models feature a smart control, fitted to
the lower immersion heater. See insert sheet for details.
ELECTRICAL CONNECTIONS
Complete the wiring – use the appropriate wiring diagrams
on pages 18-21.
DISCHARGE ARRANGEMENT
For pre-plumbed models, you simply need to connect 22mm
discharge pipe to the tundish and then route the discharge
pipe as explained below. For non pre-plumbed cylinders
you will need to position the inlet control group so that the
discharge from both safety valves can be joined together via
a 15mm tee (see diagram below). Connect the tundish and
then connect and route the discharge pipe.
Ensure all pipes to and from the tundish are cut square, are
free from burrs or damage, and that the tundish if fitted
vertically.
The discharge pipework must be routed in accordance
with Part G3 of schedule 1 of the Building Regulations. The
information that follows is not exhaustive and if you are in
doubt you should seek advice.
Note:
The discharge will consist of scalding water and steam. Asphalt,
roofing felt and non-metallic rainwater goods may be damaged by such
discharges.
Note:
Although building regulations now permit the D2 pipe from the
tundish to be installed in soil stacks within premises, we do not recommend
this, as discharge from the temperature and pressure valve may continue for
long periods of time. It is the installer’s responsibility to ensure the discharge
pipework can support the discharge for prolonged periods. If used, follow
the guidance given in the G3 Building Regulations (mechanical seal without
water trap). As discharge can be in excess of 90°C, discharge into plastic
pipework is also not recommended.
Safety device
(e.g. Temperature
relief valve)
Metal discharge pipe (D1)
from Temperature relief
valve to tundish
Discharge pipe (D2) from tundish,
with continuous fall. See Building
Regulations G3 section 3.56,
Table 4 and worked example
Discharge below
fixed grating
(Building Regulation
G3 section 3.61 gives
alternative points of
discharge)
Fixed grating
Trapped
gully
600mm Maximum
300mm
Minimum
Tundish
