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News: Legionella safety proposal to MIcrogeneration Certification Scheme.

Filed under: Latest News

Legionella in solar water heating and heat pumps. Consumer protection and Legionellosis.

Microgeneration Certification Scheme now formally asked to upgrade documents and standards such as MIS 3001 on solar thermal installations. Amendements needed in MCS regulatory documents MIS 3005 on heat pump installations and MCS 002 on building regulations and directives to deliver Legionella compliance.

A decision document on Legionella, hot water storage and MCS has been submitted to the Microgeneration Certification Scheme. This is a UK based regulatory gateway designed to promote best practice in renewable energy and to protect the consumer of microgeneration systems such as solar water heating systems. Below is the main part of the document.

Proposal for MCS document amendments / upgrades on Legionella.

Date: 25 November 2010.

Contents:

Proposed changes to MCS installer documentation.

Appendix 1: Legionella, MCS and the wider context.

Appendix 2: Does HSE ACOP&G (L8) actually apply to MIS 3001?

Appendix 3: What is today’s MCS position on Legionella compliance?

Appendix 4: Please supply a quantitative Legionella risk assessment.

Appendix 5: References.

Proposed changes to MCS installer documentation.

On its website, the Microgeneration Certification Scheme (MCS) claims to be an independent scheme that certifies microgeneration products and installers in accordance with consistent standards. MCS is designed to evaluate microgeneration products and installers against robust criteria providing greater protection for consumers. This paper aims to clarify and then a close some gaps between these laudable claims and what is actually happening.

Despite asserting it independence, MCS is dominated by industry interests and so greater protection for consumers may need to be prioritised. This paper aims to assist the delivery of this greater protection.

At a broad level, it might help if MCS chose to converge more closely with BSI modes of operation and production. At a more specific legionella safety level, which is the subject of this paper, its standards are not consistent but in fact very inconsistent, one against another. Nor, on examination, are the MCS legionella criteria particularly robust and that assessment is where any criteria exist at all because there are no Legionella safety criteria whatever in place for MCS heat pump installations. This omission might mean an unacceptably low level of consumer protection for heat pump users, given the context that Legionellosis kills more people than scalding and that legionellosis, as an infection, is significantly under-reported and under-diagnosed.

In the solar thermal arena, where at least some Legionella safety criteria do exist, they are seriously flawed. Compounding the problem is the fact that most solar thermal installations are also being incorrectly (ie optimistically) evaluated against these flawed criteria. The worrying consequence of this is that the vast majority of MCS solar thermal installations are being inappropriately registered being as MCS compliant – when in fact they are not compliant even with MCS requirements at all. Also there seems to be no reference in any MCS document to HSE’s legionellosis document L8, even though the science and principles contained in L8 underpin good practice on legionella, whether inside or outside the context of workplaces.

If MCS is to be employed as a legal gateway to funding under the Renewable Heat Incentive, for example, then these multiple and extensive noncompliances needs to be addressed rather urgently.

In practical terms, ten times (or more) greater protection for consumers from legionella risks can be provided by adopting the suggestions and principles offered below.

At least three MCS documents are identified as being in need of revision. Ahead of the introduction of the Renewable Heat Incentive is an appropriate time to make that revision. These documents are:

  • MCS 002 Information on Building Regulations and European Directives Issue 1.5 makes two references to Legionella contamination, one direct and one indirect. The indirect reference is under the heading of the Water Regulations (WRAS), which states that “avoidance of water contamination is mandatory”. The direct reference to Legionella is under the heading of the Control of Substances Hazardous to Health (COSHH) which requires precautions to reduce legionella poisoning. Setting aside the fact that a better verb should perhaps be proliferation or infection, rather than poisoning, there is, conspicuously, no mention of HSE Legionellosis document L8. Perhaps there should be a mention.
  • Heat pumps installation standard MIS 3005 omits to mention stored water and Legionella safety at all, even though stored tepid or hot water is a feature of many heat pump installations. MCS have long been already aware that this omission is anomalous. This matter is in need of prompt action, not least in the context of the parallel solar thermal standard mentioning such issues.
  • Solar thermal installation standard MIS 3001 Issue 2, at least refers to stored hot water and to Legionella. Here, however, the wording needs to be changed. In response to MCS SG Chairman Gideon Richards invitation on 5 Nov 2010 to suggest wording for MCS3001, amendments will be proposed for this standard only, even though the Legionella safety is in fact generic to all hot water storage.

Legionella bacteria do not discriminate between where heat and any other conditions affecting growth and infection originate. They just grow and unfortunately sometimes infect people in response to suitable conditions, conditions which are widely described, for example in HSE and WHO documents.

Not being heat pump installation experts, and not being invited to work in this area by Gideon Richards, we do not propose any new wording to the Heat Pump Installer Standard, but we do again suggest, that by some suitable documented means, perhaps via MCS 002, that MCS installers of heat pumps and of any other relevant microgeneration thermal technology can to refer to appropriate MCS documentation on hot water storage and Legionella safety an overarching generic standard covering all MCS installation standards. However it is hoped that any such repositioning, if it were to happen, will not allow further delays to occur, given that this important matter has been unresolved in the accreditation scene for many years.

So here follows the current and the proposed wording for MIS 3001. Justifications for the changes are presented in the appendices.

Right now, MCS Solar Installation Standard MIS 3001 Issue 2.0 of 26/06 2010 says:

Section 4.3 Safety and durability. [Solar Heating Microgeneration] Systems shall:

4.3.4 Incorporate a means to prevent bacterial growth (legionella) at all foreseeable flow rates. Note: one way of meeting this requirement would be through the use of a secondary means of heating the water to 60C.

(On a technical note, this installation criterion is not being complied with. Secondary heating is normally only turned on for a few hours a day, and even when it is turned on, its heat output is often not powerful enough to match or outpace the high flow rates imposed by the use of even individual showers and taps, let alone their use in combination. More details are in the appendices.)

A proposed new wording to MIS 3001 is:

4.3.4 Minimise bacterial risk (legionella) to acceptable levels using accepted control parameters, in compliance with any codes of practice and guidance which may be applicable or relevant, such as HSE L8.

Note: in small scale domestic owner-occupied installations, where L8 does not apply, acceptable ways of meeting this requirement may include:


a) the use of thermal stores, where stored domestic hot water volume in the heat exchanger is low and its daily turnover is high.

b) or the use of calorifiers which heat the water to 60C to the base of the calorifier daily for one hour, in installations where the stored domestic hot water volume is similar to or greater than what this volume would be in non-solar domestic hot water systems

c ) or through the use of a secondary or downstream means of heating the water to 60C which is verifiably powerful enough and reliable enough to generate temperatures that bring about adequate thermal inactivation of legionella bacteria at all foreseeable flow rates.

d) or where combi-boilers receive water from sources (excluding thermal stores) that are not able to satisfy c) above, the system is programmed to automatically activate the combi-boiler to heat the water to 60C and recirculate this through the pre-heat cylinder, at a pre-set time daily.

e) plus, where relevant, to keep potential dead legs as short as possible, for example when pipes to cold feeds to thermostatic mixing valves which are connected at the hot side to outlet from the hot water cylinder, these cold feeds should be as short as possible and not face upwards towards the hotter area.

Comments on the proposed wording, and its alignment with other documentation now follows:

in the first sentence, HSE refer to “established control parameters

a) reflects wording of L8 para 20,

b) reflects wording of L8 para 158, also Dr Makin’s statement that Solar pre-heat cylinders that maintain a temperature of 60C throughout the storage vessel for a period of one hour daily should achieve satisfactory control of legionella bacteria.

c) reflects Dr Makin’s statement. In systems where combi-boilers receive water from solar pre-heat cylinders that are not able to raise the water temperature to 60C or above, then consideration should be given to programming the system to automatically activate the combi-boiler to heat the water to 60C and recirculate this through the pre-heat cylinder, at a pre- set time daily, while

d) reflects Dr Makin’s thermal control specification for combi boilers and

e) reflects L8 para 74c on dead legs. No further comment on e) is given in this paper.

To sum up:

1/ This is a proposal for amending MIS 3001 (solar thermal) only.

2/ The huge gap in MIS 3005 (heat pumps) has not been addressed at all.

3/ Longer term there probably needs to be an overarching generic section on hot water storage (to include all technologies including solar thermal, heat pumps and biomass heating, and to encompass future technologies such as wind thermal) since hot water storage presents a generic safety issue regarding legionella.

Appendix 1: Legionella, MCS and the wider context.

Here are three important contexts: HSE, WRAS and industry dominance.

Context 1: Health and Safety Executive (HSE).

HSE believes that the drive for renewable energy sources should be balanced with due consideration given to the potential risks to the users’ health and safety.

In solar heated water systems, these risks are likely to include risks from exposure to Legionella bacteria.

Solar systems comprise a range of design and operational configurations, some of which appear to pay little heed to established parameters to control Legionella growth.

With the anticipated growth of the renewable energy market it is essential that proper consideration is given to the safe design of such systems.”

(Underlining has been added for emphasis.)

This position was posted on 2010 on a Department of Energy and Climate Change (DECC) discussion website by the HSE’s Rob Wellens, reflecting expert input from Dr Paul Logan and Dr Paul McDermott of HSE’s Biological Agents Division. According to Dr Anna Bliss of HSE’s Hazardous Installations Directorate Specialised Industries, Biological Agents Policy, this comment should be read in the context of a particular discussion: that of Legionella being a potential showstopper for microgeneration.

Although Dr Bliss of HSE has said that she would rather not see Mr Wellens quoted, a preference which seems to align with DECC denying the existence of his comment under a freedom of information request (despite this comment being offered as part of a DECC consultation) she also states that introducing new water pre-heating configurations does not change the principles of control required to protect people from Legionella.

In the interests of public safety and also the legality and credibility of the Microgeneration Certification Scheme (MCS), HSE’s comments have been reproduced here, despite the reticence of both HSE and DECC (who own MCS) to be cited.

Context 2: Water Regulations (WRAS).

In a report to WRAS, Dr Tom Makin, Directorate Manager in Medical Microbiology of the Medical School at Royal Liverpool University Hospitals, in a six page paper, wrote that:

Solar heated vessels that do not reach 60C and notably those maintaining temperatures below 45C would be particularly prone to contamination with high levels of legionella bacteria.

Quoting empirical evidence of contamination with high levels of legionella bacteria producing unacceptable risks which massively exceed HSE safety thresholds, Dr Makin refers to his experience of 100,000 or more detectable legionella bacteria per litre (cfu/l) being not uncommon at the base of hot water vessels where temperatures of 20-45C are maintained. He observes that this figure is 1000 times higher than the HSE L8 lower limit of 100 cfu/l and 100 times higher than its upper limit of 1000 cfu/l. (The upper figure is the level at which level remedial action is required, including disinfection of the water system.)

On the subject of twin coil solar cylinders, Dr Makin writes that they:

may permit temperature stratification that supports the growth of legionella bacteria at the base of the vessel. If the solar coil does not generate temperatures that bring about thermal inactivation of legionella bacteria, and if the residence time for water in contact with the boiler coil at 60C is less than that required to effect thermal inactivation, then it would be necessary to provide a further level of control e.g. consideration should be given to programming the boiler coil to heat the entire contents of the solar hot water cylinder once daily, preferably during a period when there is little demand for hot water.

Dr Makin concludes that:

It is therefore highly likely that those solar pre-heating water systems which support the growth of legionella bacteria and do not achieve thermal inactivation or control of legionella bacteria in some other equally effective way, are creating a health risk with regards to legionella infection. In the UK, manufacturers, suppliers, installers, and owners of such water systems as solar pre-heating systems, have a statutory obligation to assess such risks and implement measures that will effectively control those risks.

Dr Makin’s report was supplied to WRAS and to a small group of solar thermal and water industry representatives in January 2008. They apparently buried it and Dr Makin’s report remained an unpublished document, unavailable to the general public, including to the author of this paper (who had originally been promised by the Solar Trade Association an invitation to join this small group, an invitation which did not materialise), until it was released later that year following a freedom of information request. It is recommended that Dr Makin’s full report be read. Other papers are available on the subject of Legionella and solar thermal. For example:

  • A large study reports that solar thermal systems (with German type plumbing) in Germany having no increased legionella risk. In effect this paper could be used to support a take no action position.
  • A small study finds Legionella in the hot water of 50% of solar homes but 8% of non-solar homes in Denmark. In effect this paper may support the take action position. However, it is only a small study and it does not pinpoint the source of the legionella (eg base of store, pipework, mixing valves, etc).
  • Legionella Consultants, Legionella Control International, refer to twin coil cylinders as having a serious flaw in design. This is a report commissioned by Solar Twin Ltd, so it has been dismissed as inadmissible (not peer reviewed by the industry) by members of the MCS solar thermal WG.
  • A position paper from the European Standards Body, CEN Technical Committee 312 on solar thermal, co-authored by Dr Chris Laughton. Dr Laughton is a widely trusted expert authority in both the UK and the European solar thermal industry. Dr Laughton has been reported to be an MCS Steering Group and solar thermal WG member, independent solar consultant, professional regulations consultant and lobbyist who studied Physics at University, and lecturer at the Centre of Alternative Technology. Dr Laughton chairs the British Standards Institution’s solar thermal committee RHE 25 and chairs the Institute of Domestic Heating and Environmental Engineers Renewable Energy Group. Past editor of GA magazine, and technical author to most of UK’s leading solar thermal documents such as those branded by The British Plumbing Education Council, The Chartered Institute of Building Services Engineers and The Energy Saving Trust, some older documents are now under revision following third party technical review. The CEN position paper which he co-authors almost seems to go out on a limb in liability terms, something which as a solar supplier we would not want to support. CEN TC 312 has sought to set aside the precautionary principle of control required to protect people from Legionella. It asserts on behalf of the European solar thermal TC at CEN that one should in fact wait until people actually get ill from Legionella before doing anything at all. This position paper makes interesting reading because it appears to reflect a mainstream European and UK solar thermal industry position on Legionella, in that it:

1. seeks no change regarding the acceptance of twin coil cylinders until a long, extensive, expensive and unfunded field research project is carried out which is a Europe wide investigation about the growth of Legionella using a wide range of different hot water systems.

2. asserts an exaggerated 50% fall in solar heating system performance if safer approaches were to be used (in fact the performance fall would be about 11% and would in costs benefits terms it would be offset by lower cost installations, as already presented to MCS SG and accepted as part of the basis for earlier changes to MIS 3001)

3. on the basis of this invalid exaggeration requests special renewable energy technology exemption from the precautionary principle of disease management National and European levels (begging questions such as: why exempt anything, let alone renewable energy only?)

4. contains a graph showing that in Denmark (latitude similar to northern UK) the temperature at the base of a twin coil solar cylinder remains under 45C for many weeks in winter while describing this tepid place as very bad conditions for bacteria to grow (when in fact this offers ideal temperatures for rapid legionella growth according to most, probably all other legionella experts).

5. takes an irresponsible position (both morally and legally) that people must become ill first before the CEN TC 312 European solar thermal standards committee would accept change only on the basis of proven medical cases associated with pre-heating/back-up water heaters where it has been proven that Legionella was the cause of human poising [sic]

In the context of this CEN TC 312 position paper, one might be tempted to try to quantify the extent of the destructive impact that even one single proven case of solar-linked Legionella might actually have on the credibility of Europe’s solar thermal industry – and on the patient.

Context 3: Industry dominance.

Any public interest in Legionella safety exists in the context of an apparently overwhelming need for the solar thermal and heat pump industry not to change at all, or at best, slowly. Factors contributing to this need to resist change include:

  1. Severe market disruption and the potential predominance of disruptive newer technologies if a change were to be supported.
  2. Changeover costs, potential liability and possible free upgrade requests being supported by trading standards or the REAL Code of a scale which causes widespread business closure.
  3. Credibility and reputational challenges for leading individuals and organisations which have taken a position on the matter.
  4. Knock-on effects of any change taking place in UK into European and world regulatory arenas.

So it is requested that vested interests remove themselves from any decision at MCS.

The debate on legionella risk and hot water storage in solar thermal and heat pumps is commercially and politically highly sensitive. Widespread personal denigration of those seeking change has been backed up with coercion and constraints on public debate. For example, following lobbying, apparently from the Solar Trade Association, Which? Magazine pulled a short planned article on legionella safety and solar thermal from publication in spring 2009.

Interestingly, at a UK level, until a year ago, MCS had actually excluded all safer approach of installations delivering heating to the base of a solar hot water cylinder from MCS eligibility in MIS 3001. The Building Research Establishment, BRE (when in the position of MCS’s sole monopoly solar thermal accreditation body) had refused to consider the performance of one such installation type in the context of legionella safety, even though MIS 3001 contained a clause which theoretically allowed this consideration to happen and even though a BRE staff member had chaired the particular MCS solar thermal WG which had actually introduced this particular clause. One solar thermal supplier has been told at least three times by MCS member David Matthews of the Solar Trade Association that they will remain excluded from membership while we continue to raise sensitive questions such as Legionella. Some of the STA position has been put in writing: Any mention of potentially negative perceptions that are unjustified such as… legionella that is just not happening and I will take action. and Any mention of legionella will reduce total sales.

Extending to the European level, CEN TC 312 members involved with Legionella have a long standing written boycott in place against communications with the author, citing sensitivities with the European Solar Thermal Industries Federation (ESTIF): we should not react directly to Johnston’s email, but stick to our previous position that we do not enter in dialog…’ and ‘Does ESTIF know what could happen on this sensitive issue if Johnston’s proposal [to increase safety standards regarding twin coil solar cylinders which do not heat to the base] would be agreed to.

So, realistically there is the conservative context of low consumer representation and industry dominance of many of UK’s key regulatory bodies, such as MCS and the fact that MCS choose not to implement to standards of product and governance such as BS 0 and the civil service management code para 4.1.3.c. which would increase transparency and enhance controls on vested interest influence.

From the public interest perspective, there appears to be a need for prompt change via a decision making process which operates free from vested interests.

To sum up. Dr Makin, writing for WRAS, reports legionella numbers from the base of hot water cylinders which may be 100-1000 times higher than HSE accepted levels. HSE effectively back him up by referring to solar heating systems paying little heed to established parameters to control legionella. European standards makers are prepared to delay change until someone gets infected. The wider industry context seems to be one of coercion, denial and cover-up. Balanced decision making may be difficult.

Appendix 2: Does HSE Control of Legionellosis Approved Code of Practice and Guidance (L8) ever actually apply to MIS 3001?

Do the scopes of MIS 3001 and L8 overlap substantially? The answer is yes.

The background to this section is that Gideon Richards, MCS SG chair wrote on 25 October 2010 that he has no clear factual evidence that MCS is in breach of any statutory requirements. And on 5 November 2010: I have talked to the Chair of the Building Regulation Part G working group on this matter before when you raised it and had no reason to think MCS was contravening any legal requirements.

Gideon Richards and the MCS WG on Solar Thermal have been informed that HSE issued a residential L8 guidance document in 2003 saying that L8 applied to a

wide range of organisations, groups or self-employed individuals providing residential accommodation who are responsible for the water system(s) in their premises, including: local authorities,universities; housing associations, including housing companies; charities; hostels; landlords in the private renting sector; managing agents; hoteliers, B&B, guest house and holiday camp owners; and caravan and camping site owners, including fixed caravan sites.

So rented homes and social homes, for example, are included under L8.

As for the benefits of at complying with at least the principles of L8 in domestic owner occupied homes, MCS have also been given a report by Legionella Control International which says:

It is recognised that in general L8 does not apply to domestic owner occupied dwellings, however, solar heating systems are increasingly being installed in semi commercial enterprises and also in tenanted dwellings, under such circumstances L8 does apply for the protection of such tenants and landlords have a legal obligation under the Health &Safety at Work Act 1974 and also to the Control of Substances Hazardous to Health Regulations 2002 to protect the health and well being of their tenants. It must also be considered that owner occupied homes of today could be the tenanted homes of tomorrow and as such all properties should be considered as relevant.

This pre-emptive compliance approach may be important given the 20 plus years expected life of a solar thermal installation.

MIS 3001 is clearly intended and used today for a far wider scope of installations than just owner occupied homes (these being exempt from L8 as an HSE document). For example in MIS 3001:

  • Section 1 defines the document’s scope as solar heating systems to supply domestic hot water, space heating and swimming pools for permanent buildings.
  • Section 3.3 refers to work for private customers and other situations (for example new build, or for commercial customers.
  • Section 3.4 requires membership of to an OFT approved code for all installers and requires actual compliance with this code when dealing with domestic customers (as if other types of non-domestic customers also exist).
  • Section 4.4 refers directly to non-domestic installations in the context of annual energy performance prediction methodologies.

From the above extracts, it is evident that MIS 3001 is not just about domestic owner occupied installations but that it is scoped wider than this.

In MIS 3001 under 4. DESIGN AND INSTALLATION REQUIREMENTS 4.1 Regulations, the first sentence of MIS 3001 reads:

All applicable regulations and directives must be met in full.

Clearly L8 affects installers and so L8 must apply where relevant, and at the very least where the scope of MIS 3001 extends, as it does, well beyond just owner occupied homes. L8 applies in most, perhaps all, of these circumstances.

MCS (and earlier subsidy certification gateways such as Clear Skies), by certifying as suitable for state incentives solar water heating installations in social housing and non-domestic applications with twin coil cylinders which do not heat to the base daily may be in breach of statutory requirements to comply with L8.

So it would be wise to refer to L8, either in MIS 3001 or in an overarching MCS document such as MCS 002.

Appendix 3: What is the MCS position on Legionella compliance?

This can be broken down into two questions:

Do MCS solar thermal installations comply with MCS requirements?

And

Do MCS solar thermal installations comply with HSE L8 requirements?

Do most of today’s MCS solar thermal installations comply with MCS Legionella requirements?

No. Most do not. An explanation follows in the answer to the next question.

Do today’ MCS solar thermal requirements on Legionella comply with HSE L8 Legionella requirements?

No. Often not. Here is an explanation.

Most MCS twin coil solar cylinder solar thermal installations not only don’t operate to established parameters to control Legionella growth used in the hot water industry which is to heat to the base of a hot water cylinder daily (as in para 158 HSE L8).

Interestingly most installations also don’t comply with MCS requirements ether. This is a double noncompliance.

MCS solar thermal installation spec MIS 3001 says:

“Incorporate a means to prevent bacterial growth (legionella) at all foreseeable flow rates. Note: one way of meeting this requirement would be through the use of a secondary means of heating the water to 60 C.”

First let us look at this in the context of para 158 of HSE L8 on Legionella…

MCS MIS 3001

  1. does not specify heating to the base to 60C and holding it at that temperature for one hour and doing so every day (as this paragraph requires and is suggested by Dr Makin.).
  2. does not even specify heating to the base to 60C and holding it at that temperature for one hour (whether daily or less often, such as weekly)
  3. does not even specify heating to the base to 60C (Let alone specify holding it at 60C for an hour)
  4. does not even specify heating to the base at all (let alone specify heating it to 60C).

So MIS 3001 does not specify heating to the base, (whether by shunt pumps or other means) nor to 60C, nor holding it at that temperature for one hour, not doing so every day even though this is approach appears to be an established parameter of legionella control in hot water calorifiers without which high levels of legionella can grow.

Next, and setting aside this noncompliance, but only for a moment, the MCS “All foreseeable flow rates” specification begs some conveniently testable questions. So let’s test them in the context that this MCS requirement can only be met in conventional twin coil solar cylinders by:

1/ leaving the backup heating on all day long (the heat losses from, which sometimes knocks back the sustainability of such a system to such an extent that it may not even be worth installing solar at all according to solar simulator work as shown to MCS SG in 2009 and summarised in the video of that date referred to in the appendix.

2/ and at the same time installing a backup heating capability of a very high power (ie probably tens of kilowatts) that can keep up with the heat removal rate of people using high flow hot water outlets such as showers. Since MCS MIS 3001 refers to the flow rates being “foreseeable” then should solar thermal installers be reasonably expected to anticipate occasions when more than one hot water tap or shower is turned on at a time? Presumably so. In this case solar installers should allow backup heater some extra power for taps being turned on as well as showers especially since it is via inhalation from sprays such as showers which are the main route of legionella infection.

Do most MCS solar thermal installations meet this specification? No, of course not. Referring to the numbering above let’s now do a hypothetical “post-commissioning check list”, one which could be carried out by an installer or by an MCS certifying body…

A – Is the the twin coil solar cylinder’s backup heating left on all day? (Of course it is usually not kept on all day long: it is usually only kept on for a few hours in the evening.)

NO = THIS INSTALLATION FAILS MCS.

YES = GO TO QUESTION B

B – Is the 24 hour backup heater powerful enough anyway to cope with fast water removal from, say, one shower and to heat it to 60C while coping? (If a 3kW immersion heater is used, answer no.)

NO = THIS INSTALLATION FAILS MCS.

YES = GO TO QUESTION C

C – And (now the “all foreseeable” test) even if you do have a backup heater on 24 hours a day which is powerful enough to heat water to 60C at least as fast as a shower draws the hot water energy off the cylinder, will it also cope if you turn other taps on as well?

NO = THIS INSTALLATION FAILS MCS.

YES = YOU HAVE AN MCS COMPLIANT INSTALLATION (at least when it comes to the MCS way of dealing with Legionella).

To sum up…

Do most of UK’s supposedly MCS solar thermal installations meet the MCS’s own Legionella specification?

No, of course they do not. Only a proportion will, perhaps fewer than half of all installations. This is a shocking internal noncompliance / oversight.

I have presented the Chair of the MCS SG with extensive evidence that MCS as a body is in substantial breach of its own “voluntary” requirements as well as of statutory requirements by knowingly permitting the issuing of MCS compliance certificates to numerous noncompliant solar thermal installations.

Clearly most MCS installations comply neither with MCS, nor with HSE L8 requirements, where L8 applies.

Besides speaking with independent expert third parties such as The Legionella Control Association, The Water Management Society, WRAS, Health Protection Agency and HSE, MCS may also want to resolve this apparently significant double noncompliance (ie against 1/ its own flawed requirements and 2/ against L8) with UKAS (along with its wider relevance to heat pumps) since MCS is a UKAS regulated body.

Appendix 4: Please supply a quantitative risk assessement.

Here is one which is based on high risk water quality conditions (hard water conditions), here is a simple risk index where: Risk = area x volume x time.

This risk assessment shows:

  • That twin coil conventional solar cylinders are ten times more risky than non-solar plumbing, which is generally regarded as an acceptable legionella risk.
  • That solar plumbing using two cylinders in series is the most unsafe of all installations, being 14 times more risky.
  • That the risks of solar installations can be reduced by a factor of ten, back to those of non-solar plumbing by simply heating daily to the base.
  • That installing solar using thermal stores is extremely safe: twenty times safer than non-solar plumbing.

Based on the above and on the evidence in this paper, it is proposed that both conventional twin coil solar cylinders and solar plumbing using twin cylinders in series are no longer supported by MCS, unless they heat daily to the base. Also, because they are so safe, that MCS should name thermal stores as being acceptable solar plumbing solutions, something which is not happening at present in MIS 3001.

Appendix 5: References:

1. Video, 9 mins, legionella and risk reduction potential in renewable heating hot water storage 2010. Asks: is a renewable energy exemption from normal safety practice acceptable / containable to renewable energy only? http://www.youtube.com/watch?v=ZnKh9mdjImA

2. Video, 9 mins, legionella and heating to the base of cylinders, summary of presentation to MCS SG in 2009. Useful plumbing diagrams. Solar simulation data rebuts exaggerated IDHEE / CEN TC 312 50% energy drop claims. http://www.youtube.com/watch?v=J9v68zr213A

3. Legionella bacteria and solar pre-heating of water for domestic purposes Report by Dr T Makin for the Water Regulations Advisory Scheme, January 2008, download here: http://www.wras.co.uk/PDF_Files/Preheated_Water_Report.pdf

4. Legionella Control International Report describing twin coil cylinders as a serious flaw in design, download here: http://www.solartwin.com/PDF/LCI%20Legionella%20Report%20Nov%202008%20Solartwin.pdf

5. HSE LEGIONNAIRES DISEASE, Essential information for providers of residential accommodation INDG376 C1000 Printed and published by the Health and Safety Executive HSE Books, ISBN 0 7176 2207 X

6. Legionnaires disease. The control of legionella bacteria in water systems Approved Code of Practice and guidance L8 Third edition, published 2000. ISBN 978 0 7176 1772 2 HSE Books.

7. CEN Solar Thermal Technical Committee TC312 comments to the document: TC164 WI 164353 Technical Report Recommendations for prevention of Legionella growth for installations inside buildings conveying water for human consumption. Comments prepared 2007-06-06 by: Jan Erik Nielsen, Jean-Marc Suter, Harald Dr, Chris Laughton, FIDHE, GA, UK delegate to TC312. Obtainable from CEN TC 312 secretariat or from ESTIF.

8. MCS document: MCS 002 Building regs and directives.

9. MCS document: MIS 3005 Heat pump installation spec.

10. MCS document: MIS 3001 Solar thermal installation spec.

Legionella, hot water storage and MCS. Proposal for MCS document amendments / upgrades. Author Barry Johnston. Date: 25 November 2010.


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