Description Of Appliance - Potterton iHE 100 Installation & Servicing Instructions Manual

C L
OMBATTING EGIONELLA
Water systems in buildings have been associated with outbreaks of Legionnaires' Disease, particularly in health
care facilities where occupants are signifi cantly more susceptible to infection. In recognition of the risks in hos-
pitals, a Code of Practice for the Control of Legionella in Health Care premises has been issued by the Depart-
ment of Health.
Codes of Practice applicable to other premises have been published by other organisations, principally the
Health and Safety Executive (HS) (G70) and the Chartered Institute of Building Services Engineers (CIBSE,
TM13). All Codes of Practice draw attention to the design and operation of water systems with reference
to avoidance of factors that favour colonisation by Legionella bacteria. These factors include stagnation,
lukewarm conditions (20ºC to 45ºC) and the accumulation of debris, scale and corrosion in the base of tanks and
calorifi ers.
An independent evaluation of our products was commissioned to investigate their resistance to the build-up of
Legionella bacteria. Experiments were conducted to determine whether, following a substantial challenge by
Legionella Pneumophilia, after overnight and stagnation conditions, the system was rendered free from viable
recoverable Legionella. It was found that at 61ºC, following a challenge of approximately 107 organisms per
litre, within one hour, more than 99.999% of organisms had been killed. After a subsequent stagnation period,
sampling did not reveal any residual contamination. The design of the base of the integral water tank precludes
Legionella colonisation, even after build-up of debris. The heating process ensures that the water at the bottom
of the tank reaches the same temperature as in the rest. In addition the controls of the appliance provide anti-
legionella routines to provide additional protection.
Based on data obtained through experiment, this appliance can be described as Legionella resistant as it is
considered unlikely that, at the temperature tested, the organism would colonise the water heater and present
a possible health risk.

1.6 DESCRIPTION OF APPLIANCE

The Potterton iHE is a gas fi red, low No×, multi-heat engine cascading boiler system, with an integrated 5" Low
Loss Header for the supply of a low temperature hot water space heating system. The Sirius Advance range of
boilers also features an integrated stainless steel tank and plate heat exchanger for the supply of hot water.
Fully automatic electronic controls are integrated into the appliance, with a wide range of control and sensor
options available. The controls also provides voltage free outputs for Enable, Burner On, Fault and 0-10V input
for remote BMS use.
Each heat engine module consists of a stainless steel combustion chamber, premix burner, modulating fan, gas
valve, ignition and fl ame detection electrodes and a NTC fl ue sensor for safety supervision.
Each heat engine module is equipped with NTC sensors for precise temperature control on fl ow and return mani-
folds. Fully premixed, radiating, modulating burner, integrated with gas valve to deliver precise gas/air mixture
throughout the full modulation range.
Common combustion air intake manifold, takes air from boiler room (type B23 fl ue) or directly from outside via
a combined fl ue system (C13 & C33). An air control non-return fl ap is integrated into the air supply of each heat
engine, to ensure that fl ue products cannot contaminate the air supply, when the heat engine is not in use.
The safety and operation functions of each heat engine are managed by micro processor controlled circuit
boards, one for each heat engine. The upper controller also acts as the cascade controller, switching/modulat-
ing the heat engines according to the demand and data from the systems sensors. Control is performed using
comparison parameters between the requested temperature and the global fl ow temperature.
C L :
ONTROL OGIC
At full demand, each heat engine is ignited one at a time, until all heat engines are operating at full output. As
fl ow and return temperatures increase, all heat engines will begin to modulate down together, until all are oper-
ating at minimum input rate. As fl ow temperatures begin to approach the calculated set point, one of the heat
engines will stop, leaving the others operating at minimum input rate. This will continue until all heat engines
have stopped and temperature fl ow requirements have been fully satisfi ed.
iHE 5 GB/IE