The Leading News & Information Service For The Facilities, Workplace & Built Environment Community

Smart Design Boxes Ward Off The Legionella Threat

A Rinnai continuous flow unit.
09 May 2018
 

Chris Goggin of Rinnai looks at how smart design and control options can design out Legionella proliferation.

Legionella control and risk avoidance are top of the list when designing heating and hot water systems. The whole supply chain – manufacturers and distributors through contractors to end-users – need to plan and design systems to eliminate the risk of Legionella. It is one area where avoidance and prevention are the only sensible action to take to avoid problems further down the road.

Our modern lifestyle demands that hot water is available on tap at any time, day or night. So how can installers and designers reduce the fear of Legionella breaking out – and give peace of mind to customers and end-users?

Quite simple – limit the volume of storage on your hot water system.

 

Time consuming

A glance through the Health & Safety Executive ‘Approved Code of Practice’ highlights the vast amount of detailed maintenance needed to keep a stored hot water system Legionella free; the level of work involved is time consuming, expensive and must be adhered to religiously.

According to the HSE, stored hot water systems present an enhanced risk for the proliferation of Legionella, especially at the base of calorifiers where the incoming water merges with the existing hot water.

Legionella bacteria multiply where temperatures are between 20-45°C. Water at the base of the calorifier is liable to collect sedimented organic and mineral deposits, which support bacterial growth, including Legionella, which is then distributed throughout the system.

To ensure total safety, therefore, the whole water contents of the calorifier, including at the base, must be heated to a temperature of 60˚C for one hour each day.

 

Continuous flow

A lot of these problems are solved by choosing to install a continuous flow hot water heating system. With a gas-fired continuous flow system there is no cylinder to cause problems because the cold water enters the water heater directly from the mains and is immediately heated to advisory levels.

With Rinnai continuous flow units water temperature for distribution is accurate to ±1˚C. The fact that there is no stratification as there is no storage ensures permanent even temperature. There is no requirement to heat a volume of water just to ensure the elimination of Legionella bacteria as the minimum temperature that a continuous flow unit achieves exceeds advisory levels.

 

Secondary return

However, when considering design parameters that incorporate secondary return systems pipework and dead legs can act as water storage. ACOP L8 (Legionella Guidance) highlights that (continuous forms of instantaneous) systems installed close to the point of use have a greatly reduced risk of Legionella proliferation.  Despite this in many instances commercial applications are designed around a secondary hot water return.

So, when the taps or shower heads stop running, after use, the pipework will be full of cooling water capable of breeding Legionella bacteria; therefore you do have stored water and appropriate safeguards must be put in place.

 

So, what is a smart design consideration to eliminate any risk of Legionella bacteria multiplying in a hot water system without keeping water circulating constantly at 60 degrees?

The technology is available in the form of smart controls linked to the water heating system, inside which is a timer channel programme and a temperature controller. The timer will over-ride the temperature control for a short period and then revert back to safe levels. This combination allows for safe running of water at 42°C core temperature during the day and thermal shock the system at 60°C intermittently at times when the building is not in use. By the time the building opens again, core temperature is back down to 42°C for safe use.

Some parts of the hot water system, such as rarely used shower heads or terminal fittings, will require regular maintenance and frequent checks to ensure the hot water system is operating correctly.

It is a very simple technology that takes advantage of innate high-tech controls within the water heater, it eliminates risk from Legionella bacteria and is ideal for use in care homes, hospitals and sports clubs - any large or small scale site.

Picture: A Rinnai continuous flow unit.

 

 

Article written by Cathryn Ellis | Published 09 May 2018

Share



Related Articles

Reliable Hot Water Supply For Cleaning And Hygiene Industry

Rinnai is offering a range of units that give an instant and constant flow of hot water available to any site that needs it within 24 hours. The units are ideal...

 Read Full Article
A Continuous Flow Of Hot Water Training

Rinnai UK, a registered provider of CPD courses, has implemented a series of training modules which are specifically designed to engage with heating engineers &...

 Read Full Article
Online And In Touch – The Digital Way Ahead

Chris Goggin of Rinnai looks at the way to the future for installers, specifiers and end-users, with an online and fully digitalised approach to trading in...

 Read Full Article
King Of The Castle For Dirty Rascals

Rinnai continuous flow and solar panels have replaced a stored hot water system at Peckforton Castle - an historic home repurposed as a popular luxury hotel and...

 Read Full Article
Infinity Hot Water Heating Range Ideal For LPG

Rinnai offers a range of LPG compatible, A-rated, eco-labelled, continuous flow hot water heating products which includes the 16i (36.8kW output giving 16 litres of...

 Read Full Article
Rinnai Report Shows Eco-Propane Potential

Leading manufacturer Rinnai has completed a detailed report into the possible savings of 81 per cent on carbon emissions if off-grid sites convert to using BioLPG as...

 Read Full Article
Connected In Passion For The Next 100 Years – Rinnai Celebrates Centenary

Rinnai, best known in the UK for its comprehensive range of hot water and heating home units, is globally celebrating its first 100 years of manufacture in serving its...

 Read Full Article
Madagwa Signs for Premier Hotshots

Rinnai, the premier manufacturers and suppliers of continuous flow hot water heating units and delivery systems, has added to their technical service department with the...

 Read Full Article
Rinnai - ‘E’ Before ‘I’ Or Vice Versa?

Rinnai offers big performance, heavy duty, diminutive appliances that offer virtually limitless volumes of hot water at useable temperatures. Both ‘E’...

 Read Full Article
Top Tips For Hot Water Heating Units

Pete Seddon lists the most important points of ensuring that continuous flow hot water heating units are well serviced and maintained to ensure the longest possible and...

 Read Full Article