Barry Johnston

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since Apr 13, 2010
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As a biologist turned solar product developer I was honoured in September 2010 to be invited to speak to a national conference called "Combating Legionella" about the 80,000 or so renewable energy installations in UK (mainly solar water heating with twin coil solar cylinders) which currently enjoy a European "exemption" from UK health and safety guidance (HSE document L8) - without their users being told. I was given 30 minutes to discuss this and to come up with a calculation of the increased risks which they faced. Up to 10 times higher is my conclusion. Here is a brief video summary.

http://www.solartwin.com/solar-news-solartwin-invited-to-speak-at-legionella-seminar

Please do discuss / dispute my conclusion. We need debate because the green energy industry needs to grow up - in the right direction.

I hope this helps in the Legionella safety debate. Best wishes from Barry.
14 years ago
Paul, many thanks for your response.

On your interesting questions about Legionella nutrition and growth rates, plenty of useful work been published. In summary, they most like dirt and warmth. Being bacteria, rather than algae, they do not grow directly in response do light as plants such as algae do. Instead they feed on carbon-based biological material. That is why we only use silicone (ie non-carbon) rubbers in the Solartwin solar panels, in order to starve them. The following (free) guidance documents look at the above issues in detail, plus others such as ecology, biolfilm, and risk assessments.

- UK Legionella guidance (see para 158)  is here: http://www.hse.gov.uk/pubns/priced/l8.pdf
- European Legionella guidance is here: http://www.ewgli.org/data/european_guidelines/european_guidelines_jan05.pdf
- World guidance is here: http://www.who.int/water_sanitation_health/emerging/legionella.pdf

There is also a youtube video on solar thermal and heating water stores to the base here: http://www.youtube.com/watch?v=J9v68zr213A

To simplify the solar plumbing appproaches into three:

1/ Dedicated solar preheat volume which may never reach 140F in winter. This is a major historical solar plumbing approach which is described in Europe as "industry accepted", "proven", "successful", "established" and "not a problem in low risk cases". However it may fail to protect people even in normal circumstances such as when:

- The backup heater is not running at the time when people take a shower. (Legionella is an inhaled pathogen.)
- The backup heater is running but high flow rate, or high water volume use mean that the water spends less than 1 hr passing through the backup heating zone. This could easily happen when people take showers consuming a volume which is greater than the hot top of the cylinder.
- The sun comes out nice and bright in the morning. A solar heat exchanger at the base of a cylinder may start at 20C, but soon heat small volume of water around it to say 70C. If the hot top is at 60C, the heat exchanger hot water at 70C will rise and destratify the whole cylinder.  On a sunny morning you may end up with water at a temperature which is below 50C coming out of your shower.

The Dr Makin paper on solar thermal and hot water conditions for legionella appears to rate L8 noncompliant installations such as these as being "highly likely" to be creating a risk. References:

Dr Makin report: http://www.wras.co.uk/PDF_Files/Preheated_Water_Report.pdf
Some comments on it: http://www.solartwin.com/censorship-news-massive-solar-legionella-cover-up-revealed-today-by-freedom-of-information-inquiry

2/ Dedicated solar volume in time. This heats to the base, daily to 60C and holds it there for an hour in the evening. This complies with L8 and is safer than 1/.

3/ Thermal stores. Here the volumes and residence times are reduced dramatically with a corresponding dramatic improvement in risk assessment and is again safer than 1/.

Parts of the UK's and Europe's solar industry has adopted a seemingly unbalanced position in that 1 is promoted, while 2 is downplayed and 3 is completely omitted. The current approach incurs avoidable risks. Its prescriptive approach risks marginalising other potentially better approaches. A preferable, low risk, position might be that 2 and 3 are promoted as preferable to 1/, which would be phased out, over an agreed timescale.

So, what is happening elsewhere? Readers, do please let me know if this is useful.

Regards from Barry Johnston.
14 years ago
Hi,

I have been running a solar water heating innovation company in UK for a decade. Having started my career as an aquatic biologist, I have been looking at Legionella in depth. One issue is solar hot water storage, and I hope this post is interesting to an international audience.

In UK, the solar water heating industry is not actually complying with government safety guidance on Legionella and a major shakeup of the solar heating industry is happening right now.

Technically, this guidance (UK HSE Legionella code and guidance L8 para 158), contains  a "pack of four", which is:

1 Heat stored water to 60C (140F)
2 Heat it daily
3 Hold it at 60C for 1 hr
4 Heat the whole calorifier contents, including to the base.

Looking at point 4: the "whole contents to the base" requirement, it seems that many in the UK solar thermal industry may be noncompliant because of today's practice of heating part-way down the cylinder only.

From an insurance perspective, the majority of non-domestic solar thermal installations (plus certain domestic ones, such as those in rented and social homes - where L8 applies) may be regarded as noncompliant, and therefore as defective. The fact is that clients are normally within their rights to require all defects (ie faults) to be fixed - free of charge. But this could cost installers £200-£600 ($300-$900) per job. This potential liability (on top of the health and safety one to the user) worries of some major players in the industry and has caused some of them to be overtly hostile to a minority who seek to discuss this issue openly.

My having queried the para 158 noncompliance, and as part of a UK industry group meeting on the subject, the author of L8, Dr Tom Makin (full contact details and references are also available), wrote a report (you will find it on the UK Water Regulations and Advisory Service (WRAS) website) describing conventional solar thermal installations as being "highly likely" to be "creating a risk".

We were not included in this meeting, despite having been given assurances that we would be - and the report was kept secret. However we eventually obtained a copy of this report (under Freedom of Information law). Following our disclosure of this report on our website (as one is permitted to do) some months later it was published on the WRAS website.

I understand that outside Europe there have been cases of Legionella linked to solar thermal. As a company director I am obliged by law to comply with guidance - unless I can explain clearly why I should not. L8 is not a forgotten document: it is regularly used in prosecutions.

Recent evidence of successful L8 proescutions or censure of UK government agencies:

£24,000 ($36,000) fine plus costs: Welsh care home for inadequate legionella assessments http://www.hse.gov.uk/press/2009/coiw37209.htm
£25,000 ($37,000) fine plus costs: butchers / meat packers. http://www.hse.gov.uk/PRESS/2009/coinw01109.htm
£300,000 fine ($450,000) plus costs: Cider maker HP Bulmer Limited http://www.hse.gov.uk/PRESS/2008/wm421708.htm
£48,000 fine ($72,000) plus costs: Liverpool hospital. Unsafe levels of legionella in water for showers, etc. http://www.hse.gov.uk/PRESS/2009/coinw036trust09.htm
Even the prison service has infected prisoners http://www.hse.gov.uk/Prosecutions/documents/crowncensures.htm

There is more detail on the solartwin.com website.

I hope this is interesting. I can send readers papers if they want.

Regards, Barry.

14 years ago