Posted by: @transparent

↑

Two further points:

1: Legionella  is a Notifiable Disease to UK Health Security Agency. Any infection is subject to an investigation which must identify the source.

I've posed the question as to why a potential risk isn't notifiable.
Prevention would seem to be the better option!

 

2: The DESNZ Public Consultation on Delivering a smart and secure electricity system (closing date is tomorrow 21st June) contains a number of questions in Section-1 on their proposals to include Heat-Pumps within the corpus of devices subject to DSR controls (Demand Side Response).

In short that means they intend to legislate to allow Service Providers to switch off your heat-pump during times of high grid demand. This would work in similar fashion to smart EV chargers being controlled by your electricity supplier.

That comes with the risk that your heat-pump might've been switched off during a period when the anti-legionella cycle would normally have run. It also means that the DHW tank temperature is more likely to have dropped to a temperature where growth of legionella bacteria would be increased.

If that were so, how would a homeowner know that the anti-legionella cycle hadn't occurred?
Is it reported somewhere?
Can a heat-pump be requested to report the last time the cycle had run?

Given the dearth of site-specific information and instruction given to homeowners, how many are likely to know how to start an anti-legionella cycle manually, even if they realised that it hadn't occurred to a programmed schedule?

If my understanding is correct, for most, if not all, heat pump controllers to respond to a stop and start signal from a Smart meter then this functionality would have to be enabled within the heat pump controller. How many consumers do you think would allow this function to be enabled?

@derek-m  DESNZ isn't proposing to route DSR controls via Smart Meters.
They intending using the internet.
It's another 'blunt instrument' which will take no account of local/regional conditions or tariff schedules.

There are two different DSR payment methods being trialed by NGED/SSEN which reward homeowners for participating in their heat-pump (and other Energy Smart Appliances) being switched on/off remotely. There are also two different control methods.

See an overview of the Equinox Project trials here, and the details in this presentation from autumn'23 in particular.

I've written to the Innovation Team a few hours ago to ask if they're aware of the risks of Legionnaires Disease when Heat-pumps are turned off remotely.

@transparent Just read through the Equinox presentation, which does mention that any impact must not affect end-user safety, which concerns you've raised obviously could. I'm hoping they don't draw too much from the "high level of compliance and adherence" seen in the trials, as I'd expect anyone participating in such a trial to be an atypical user (as I guess any HP owner would be of the general population, by and large). As an EDF customer, they have run several "lower your consumption during these times" cashback schemes to encourage lower usage during peak times, and I wonder if the results of that are being similarly examined to enable trends to be seen? Of course, there's a massive difference between trials/short-term schemes, and enforced remote-control of consumer energy consumption.

Let's note that the Equinox Trial is being run by competent engineers from DNOs.
They're not heat pump experts.

What we can do here is to provide them with background knowledge of what happens when power to heat-pump is cut.

If a Power-outage extends over a time period when an anti-legionella cycle would've occurred, are HP controllers 'aware' of that?
When power is restored, does it provide any indication that the cycle has been omitted?
Does any HP run an anti-legionella cycle as a precaution when power is applied?

Does any HP take action if it's sensors detect that the temperature in the DHW cylinder has fallen within the danger zone for legionella?

DESNZ's Public Consultation is asking if there should be a Directive to Manufacturers to make HP models such that they have particular features to better suit them for DSR operation. [Q.26]

The Consultation asks specifically about whether HPs should be able to modulate their output in response to Explicit-DSR commands? [Q.11]

And they want us to comment on whether DESNZ should set a max limit on how long a heat-pump should be switched off due to Explicity-DSR commands. [Q.17]

Hi, does anybody know what the legal position is concerning Legionella in connection with a ASHP, in other words is there a legal requirement to have a Legionella kit installed on a ASHP. My pump does not have a Legionella kit installed.

Good question @potatoman

My County Councillor has taken up this matter with the regional office for Public Health England, and I've received a response.

Posted by: @potatoman

↑

Hi, does anybody know what the legal position is concerning Legionella in connection with a ASHP, in other words is there a legal requirement to have a Legionella kit installed on a ASHP. My pump does not have a Legionella kit installed.

This was a topic we talked about in one of our podcasts, where a panelist mentioned that homeowners aren’t legally required to run legionella cycles. However, there is a legal requirement for businesses to do so. That said, it’s always best to verify this information to ensure accuracy.

Regarding legionella control, there isn’t a specific “kit” for this. Most of the time, the heat pump’s control panel will include legionella settings. When the parameters are met, legionella cycles are usually handled by the immersion heater in the hot water cylinder. Some heat pumps also have an immersion heater within the unit itself, which can be used for defrosting and running legionella cycles.

Could you remind me which heat pump brand you’re using? 

The legal position on prevention of Legionnaires Disease doesn't appear to be clear @potatoman

The Exeter-based office of Public Health England didn't appear to see prevention as part of their remit, although they would expect to be involved if someone suffered from the infection. They stated that this could be an issue to be handled by the Environmental Health Officers at the district/borough level of local government.

To some extent that makes sense because it is District Councils who administer planning permission and building control issues. However, in the case of heat-pumps, we already know that the vast majority of installations do not comply with Part-L of Building Regulations, and Councils take no action.

When there have been accounts of legionella infections in the press, they invariably concern members of the public picking up the bacteria in water droplets from heating/ventilation units owned by companies or organisations. The Health & Safety Executive therefore pursue a prosecution. The same laws apply to all property, which leaves open the possibility of a householder being prosecuted if their heat-pump installation gives rise to Legionnaires Disease. Many home insurance policies already have clauses which cover legal costs, but I wouldn't like to risk such a prosecution, and any fines are unlikely to be covered.

That leaves us with the question of whether a professional installer or a heat-pump manufacturer could be held liable for equipment which didn't offer an anti-legionella provision.
That's less likely.

If a roof tile falls off and hits someone at your front door, then the householder is liable and would usually make a claim under the house insurance policy.

That responsibility is true even if the tiles had been recently fixed by a roofer.

Posted by: @transparent

↑

That leaves us with the question of whether a professional installer or a heat-pump manufacturer could be held liable for equipment which didn't offer an anti-legionella provision.

I can only share what the installers have told me: they enable legionella cycles on installed systems to avoid any long-term liability. However, as a homeowner, if you choose to turn off the legionella cycles (as we have) I don’t believe there’s any liability on the homeowner. Interestingly, every installer I’ve spoken to who owns a heat pump has their legionella cycles turned off. That’s not to say it’s the right or wrong approach, but it’s worth noting as a common practice among professionals and the associated risk.

I think that legionella is a much bigger risk if the DHW system has an open tank in the loft (as used to be the common practice in British homes) where there is the possibility of debris entering the tank. Such systems included one cold water tap directly fed from the mains which, strictly speaking, was the only safe supply of drinking water. Where the DHW cylinder is directly fed by a chlorinated mains supply then the risk of legionella should be extremely low.

Sadly @johnr the chlorination of our water supplies isn't adequate to eradicate legionella.

Read also what I wrote in another topic about the Cryptosporidium outbreak which affected mains water supplies in the Brixham area of South Devon.

There will be circumstances in which legionella bacteria are present in the water supply. The point of the anti-legionella schedule in heat pumps is to prevent the DHW tank sitting at the temperature range where they can rapidly multiply.

It's the speed of bacterial culture growth which presents the problem.

Do you know the classic biology question which reads:

"A jar of culture medium is injected with a bacterial sample which exhibits cell division every minute.
After an hour, the jar is 'full' in that it is 100% saturated with bacteria.
When did it reach 50% saturation?"

@transparent I haven’t done “Biology’ at any time at school or since but, this question looks as if it would require an answer of 59 minutes to me. Toodles.