The scope of this investigation covers the water hygiene / Legionella performance of the Mitsubishi Heavy Industries (MHI) Q-Ton Heat Pump.
The purpose of this report is to consider whether the Q-Ton Heat Pump represents a water hygiene risk equivalent to ALARP (As Low As Reasonably Practicable) for the three susceptibility groups general public, healthcare/elderly/health compromised and immunocompromised.
The investigation methods were interview, inspection of a unit on a trial site, inspection of documents and literature search.
This report is focussed on the re-heating of circulation loop configuration, because the majority of the market would fall into this category and because recirculating systems have a higher potential inherent risk compared to single pipe systems.
The water hygiene risk factor of relevance to the Q-Ton relative to other competitor technologies is amplification i.e. multiplication of micro-organisms, which this report considers.
The Q-Ton could represent ALARP in water systems serving populations of any susceptibility, subject to appropriate design, installation, commissioning, monitoring and maintenance.
One feature of the Q-Ton system which could be considered superior to other systems, is the option to store water at 90oC or 75oC, which provides an environment which is very adverse for micro-organisms.
It is important for MHIAE not only to control the inherent risk associated with its Q-Ton unit, but also to control and influence the risks associated with its installation, commissioning, monitoring and maintenance.
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