Technical data

3
Specification
Purewell VariHeat
Natural Gas
Hamworthy have designed the Purewell
VariHeat to retain all the benefits
of traditional boilers, but with vastly
improved performance to more than
meet the performance requirements
for modern day boilers.
Purewell VariHeat boilers can be used as
single boilers, or as modules in a multiple
boiler installation. Each boiler is equipped
with a pre-mix down firing burner, cast iron
primary heat exchanger and a control panel,
all enclosed in a stylish factory fitted casing.
As a modular boiler, the Purewell VariHeat
can be installed with up to six boilers on
a single flue header, condensing outputs
reaching 1080kW, and centres are the
same as the Purewell and UR predecessors,
simplifying replacement. The boilers are
suitable for use in open vented or pressurised
systems and have a maximum working
pressure of 7 bar.
Construction
A down firing fully modulating gas burner
is fitted on top of the primary cast iron heat
exchanger and on the condensing models,
a secondary heat exchanger is positioned
in the base of the boiler to maximise heat
recovery from the flue gases.
The boilers are delivered fully assembled,
but for plant rooms with difficult access,
it is a simple task to separate the individual
sections for easier handling.
The boilers are finished externally using steel
side panels and stylish moulded plastic front
and top covers, which give excellent access
for servicing and maintenance.
Performance
Purewell VariHeat condensing boilers
achieve a full load efficiency up to
93.7% gross (104% nett), whilst at part
load the efficiency rises to 97.5% gross
(108% nett). This equates to seasonal
efficiencies up to 96% gross.
The high efficiency non condensing
models achieve seasonal efficiencies up
to 91% gross, exceeding the Building
Regulations minimum seasonal efficiency
requirements of 84% gross, for new
buildings and existing buildings.
All boilers achieve European Class 5
performance for NOx emissions.
Flue System
The Purewell VariHeat is a high efficiency boiler, and like all other high
efficiency appliances, requires a water tight flue system that will retain
condensate whilst working under positive pressure.
The boiler is fitted with a primary flue connection directly into the base
assembly. The connector is fitted as standard with a tri-lip full ring silicone
seal which is impervious to water and vapour, ensuring a water tight flue joint.
It is compatible with the Hamworthy Masterflue range of stainless steel
flue components which are available in single or twin wall formats,
and can be interchanged to provide a safe and effective flue system.
Refer to page 26 for more details.
A fixed draught diverter is not required in the flue system, however,
a draught stabiliser is recommended for some installations.
Flue Terminal Location
Purewell VariHeat condensing boilers will produce condensate due to their
high thermal efficiency. The effect of this condensate production is to produce
pluming from the flue terminal, and careful consideration must be given to
the location of the flue terminal. Should pluming be a concern, then the flue
system should be designed to discharge at high level so as not to cause
a visual intrusion to the building occupants.
Condensate Discharge
The condensate drains safely into the base assembly and a 32mm diameter
drain connection is provided, to run in standard plastic waste piping.
This condensate drain must be connected to a suitable drainage system,
typically as shown above. The material should be a suitable PVC plastic
system with sealed joints to prevent the escape of condensate.
Drain traps and an open tundish should be incorporated into the design,
and the pipework given appropriate protection from physical damage.
The pipework should be installed with at least a 3 degrees fall
(approximately 50mm per metre).