Legionella safety in twin coil solar cylinders. Does your solar water heating system solar plumbing require a legionnella safety upgrade? Solar thermal technology surely needs to be safe regarding legionellosis, but this kind of solar cylinder is apparently NOT capable of being approved by the UK Water Regulations Advisory Scheme and has even been condemned by several technical studies. But the solar industry loves it!
Legionnellosis (Legionnaire's disease) is a potentially lethal bacterial infection of the lungs which causes pmeumonia. It is generally contracted by inhaling contaminated water spray, not by person to person contact. People with weakened immune systems are the most susceptible to legionellosis. Legionellae infections kill approximately 10% of infected people. They also disable many survivors: some require extra oxygen for life. Most Legionella cases are not detected: medics think that about 90% of cases are "missed", in that they are simply categorised more broadly as pneumonia.
Legionella bacteria are very common in water. They mostly inhabit warm water, where they can grow fast. Fortunately they are killed by heat: slowly by heat at 50C and more quickly at 60C. This is why in UK, all stored water is normally heated to 60C: to stop them from growing to high numbers.
One noticeable exception is solar twin coil cylinders, which probably comprise about 80% of UK's domestic solar heating installations. The lower half of these hot water stores is usually not heated beyond 50C for about 3 months in winter. Fortunately these are safer upgrade solutions available right now: heating to the base with the help of a "shunt pump on a timer" or a new "basal backup heater solar cylinder" or a "solar thermal store".
You may like to call your solar installer and ask them for a free lagionella safety upgrade. Don't take no for an answer. Maybe Trading Standards will help. But what about getting help from the solar industry itself? UK's Solar Trade Association (STA) opposes a legionella safety upgrade for domestic solar heating users. The European Solar Thermal Industries Federation (ESTIF) is reported to take the same "business as usual" approach.
It is funny that that the UK's main accreditation route to state subsidy, the Microgeneration Certification Scheme (MCS) had, until 15 months ago, refused to allow installers of solar water heating systems to heat to the base. Hundreds of Solartwin customers were actually refused a grant from the UK Government because they had a safer system! Also funny that the green energy watchdog, the REAL Code (a supposed consumer code) refuses to tell us at Solar Twin Ltd whether or not any solar heating customers with existing twin coil cylinders are entitled to a free safety upgrade. We have gone ahead and offered this anyway. Less funny if you look at the potential consequences for public safety or at the power-politics-reality that MCS and REAL are both funded by industry, not by consumers.
Legionella safety is not just a solar thermal issue: some heat pump hot water stores such as those for ground store heat pumps (GSHP's) and air source heat pumps (ASHP's) are also affected.
What are the impacts for the renewable heat incentive? RHI.
Loading...
1:07
Solar Heater #27 temp updateby bear42229271 views
If you want more information there are two, rather more detailed, videos about legionella and solar as solaryes videos. I'm coming at this matter from the perspective of a biologist who is also involved in solar water heating systems design.
Regards, Barry.
solaryes 1 year ago
Is your twin coil solar cylinder like this?
Maybe ask your solar water heating installer for an plumbing upgrade, so it heats to the base regularly to 60C. This small change pasterurises bacteria, reducing the risk of legionellosis (legionnaire's disease).
Legionella consultants, Legionella Control International condemn twin coil solar cylinders as "a serious flaw in design". Some plumbers can not insure them but corner-cutting solar installers love them.
You heard it first from Solartwin!
solaryes 1 year ago