HAMWORTHY HEATING LTD
Page
DORCHESTER DR-SE
500001062/D
1.0 INTRODUCTION AND DELIVERY
1.1 This heater must be installed by a competent
person holding ‘CORGI’ registration or equivalent.
All installations must conform to the relevant Gas
Safety and Building Regulations. H.S.E. requirements
must also be taken into account when installing,
operating and maintaining any equipment.
1.2 This heater can be adjusted to fire either Natural
Gas (2nd Family) or LPG (3rd Family). This manual
refers to models suitable for Natural Gas. For details
of LPG models, refer to Appendix 1 at rear of manual.
Consult the heater data plate to ascertain which gas
group the heater has been manufactured to use.
Heaters MUST NOT use gas other than that for which
the heater has been adjusted.
1.3 All heaters are factory assembled and delivered
individually packed and shrouded in polythene on a
wooden pallet. Within the packaging, wrapped
separately are the draught diverter and the two piece
burner/controls cover. A separate package contains
the installers kit comprising a manual gas shut off
valve with integral union, a drain valve, reducing bush,
lighting up instructions and users instructions.
The exterior casing of the heater is coated with a
protective plastic coating which should be peeled off
following installation.
To check the size of the heater, refer to the rating
label which is attached to the heater casing and
mounted above the burner controls.
2.0 DESCRIPTION
2.1 Heater
The Hamworthy DR-SE series of automatic gas fired
hot water storage heaters comprises two models
designated DR-SE 18 P/P and DR-SE 20 P/P. Each
unit is fired by an atmospheric gas burner
incorporating a permanent pilot and controlled by a
multi-functional gas valve of the self energising type
(no electrical supply required). This valve is fitted with
an integral control thermostat for automatic
temperature control and Piezo unit for ignition of the
permanent pilot. A manual reset overheat safety
device (high limit thermostat) is fitted on the
thermocouple circuit to extinguish the pilot flame in the
event of an overheat trip occurring.
Flue gases from the combustion chamber pass
through the heater via three central fire tubes which
are fitted with stainless steel retarders to ensure
maximum heat transfer to water. The draught diverter
supplied must be fitted in an unmodified condition to
the spigot around the top of the fire tubes where it
provides a connection to a vertical flue.
The internal surfaces of the vessel, coated with a high
quality glass lining together with a removable
sacrificial magnesium anode, provides the best
possible protection against waterside corrosion. The
vessel is fully insulated and covered in a pre-coated
sheet steel casing.
The connections provided on each heater are:-
Cold water inlet, hot water outlet, secondary
recirculation and drain. Additionally, both models
include an inspection/clean out door.
The heaters are floor mounted units designed to
provide hot water for domestic, commercial and
industrial premises. They can be installed in single or
multiple units and can be used in conjunction with
suitably sized additional storage tanks (not HHL
supply).
All screw threads used on the heaters conform to the
following:-
ISO 7/1 or ISO 228/1 for pipe threads where
applicable.
ISO 262 for all general screw threads.
2.2 Options
The heaters can be supplied with the following
additional variations, either ready fitted or for site
fitting.
2.2.1 LPG - The heaters can be supplied adjusted for
use on propane or butane - see Appendix 1 at rear of
manual. It is important that the heater is correctly
adjusted for the gas to be fired.
2.2.2 Unvented supply - The heaters can be supplied
with a purpose designed and sized unvented kit
comprising pressure reducing valve, non-return valve,
expansion vessel, expansion relief valve and
pressure/temperature relief valve, to enable the heater
to be coupled directly to the mains water. For details
see Appendix 2 (publication No. 500001005)
2.2.3 Time Clock Control - A conversion kit can be
supplied which provides a 230 volt single phase
solenoid valve between the gas control valve and the
burner enabling the heater to be controlled from a
time clock or interlock (i.e. fan dilution flow switch).
For details see Section 15.1 of this manual. Note: If
any form of time clock control is fitted due regard
should be given to the HSE and DHSS guidance on
the maintenance of water temperatures to avoid
Legionella.
2.2.4 Flame Failure Alarm - A pressure switch can be
supplied fitting on the gas pilot supply tube between
the gas control valve and the pilot burner which will
detect the absence of a pilot flame either due to pilot
failure or an overheat condition. The pressure switch
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