correct imersion heater temp

[Andy & Kim]

hi, what is the correct temp setting to a immersion heater for DHW. I have just measured mine and it is 66C. Is this too hot? Andy

[Andy Hall]

On Mon, 15 May 2006 07:22:46 +0100, Andy & Kim wrote (in article ):

A little.

60 degrees is more typical.

[John McLean]

"Andy & Kim" wrote in message news:e496nm$2t7$1$ [e-mail]...

Here is an article which recommends 48C: - Thermostatic Valve Safety HW Systems A LAW to help prevent children and the elderly from being scalded by hot water comes into force tomorrow. All new and refurbished properties in Scotland must have a thermostatic valve fitted to part of their hot water systems to ensure water from a bath or bidet does not exceed 48°C. The move is expected to save hundreds of people from scalding each year. The law is being introduced after The Sunday Post highlighted cases of youngsters being seriously injured by hot water. Last September, Communities Minister Johann Lamont launched a consultation on new building regulations. At that time, the proposal was to limit water temperature to 43°C. However, following representations from interested parties, that has been increased to 48°C. Until now, advice has been issued on water temperature control, but there has been no mandatory regulation. Last year a petition from the Scottish Burned Children's Club was presented to the Scottish Parliament's Public Petitions Committee. It pointed out that 2500 children are treated at accident and emergency departments each year after scalding incidents. Of these, around 500 are admitted to hospital, most aged five or under. On average, one old person a year dies from being immersed in hot bath water and there have been several instances of children dying of toxic shock syndrome due to scalding. Skin temperature Each thermostatic mixing valve will cost around £80. Normal body temperature is 37°C, but skin temperature is lower, just under

34°C. A "hot bath" has a temperature of around 40°C, the maximum recommended for children. At 60°C, it takes just one second for hot water to cause third degree burns. The petition was brought to Holyrood in 2004 by SNP MSP Michael Matheson, on behalf of Darren Ferguson, one of his constituents, who was badly burned as a child. "I'm delighted this law is finally being introduced," Mr Matheson said. "These new regulations will help prevent hundreds of children from being burned each year." Johann Lamont added that scalding happened every day, with very young and older people particularly at risk. "It can happen in a matter of seconds," she said. "Fitting a thermostatic valve can help prevent this. We've listened to people's concerns and have also consulted with plumbing, gas, manufacturing and safety organisations. "All new and refurbished bathrooms should have these valves fitted to make homes safer and help stop unnecessary injuries."

[Christian McArdle]

It says no such thing. Setting a DHW thermostat to 48C would be quite dangerous, as it would encourage the growth of leggionaire's.

What this article is proposing is the addition of a thermostatic mixing valve, which reduces the output temperature, whilst ensuring that the cylinder itself is still safely above 55C.

If you have no thermostatic mixing valve, then the cylinder stat should be kept between 55C and 60C as the best compromise between two conflicting safety issues.

Christian.

[John]

The article is irrelevant to the OPs question which was relating to the temperature to set the immersion heater to and hence the hot water cylinder temperature.

I can't see where storing a cylinder full of tepid water at a temperature low enough to permit the growth of Legionella is an improvement. The use of thermostatic mixing valves does not require this and moreover would permit the store to be mainatained at a higher and hence more sanitary temperature.

[<me9]

That applies to the delivery temperature. It should be stored at at least 50C otherwise it can lead to build up of dangerous bugs such as legionella. I store mine at between 60C and 82C and deliver it via a thermostatic valve set to 50C. I would set it lower if it didn't deliver to the kitchen sink as well.

60C is the lowest I'd allow stored water to sit at, but it _is_ advisable to deliver it at lower temperatures.

[John McLean]

Lordie lordie: - legionnaires disease, emanates from stagnant pools of water such as cooling towers for air conditioning, where the air is drawn across the surface of the water, this is not relevant here! How many recorded incidents of legionairres disease have been attributed to such a source? I would set the thermostat for a maximum of 55C and no more!

[Christian McArdle]

Wrong. Leggionaires' will flourish whereever the temperature is under about

45C. It becomes dangerous where atomisation of water occurs. This might be a domestic shower, or a commercial air conditioning system. The main reason that there have been few cases in domestic systems is that it is very rare for the thermostat to be under 55C.

Obviously, the risk in air conditioning systems is often much greater, due to the temperature and aerosol conditions. However, domestic hot water systems set to 40C or so can also be quite dangerous. Even hotter systems are at risk, particularly due to the reservoir of cooler water underneath the heating element.

Christian.

[David Hansen]

On Mon, 15 May 2006 12:29:15 +0100 someone who may be "John McLean" wrote this:-

Incorrect.

The little nasties exist all over the place, in low concentrations. In low concentrations they are not a great problem.

As the temperature of the water they are in is raised so they reach ideal breeding conditions and rapidly multiply. In high concentrations they are a real problem, especially for those who are susceptible to them, especially when they are in aerosol form as in a shower, or spray tap and so can be breathed in easily.

Raise the temperature even higher and they die off, reducing the concentration of the little nasties.

[John McLean]

find statistics on known health issues arising from this source?

[Chris Bacon]

That's complete rubbish. First degree, possibly.

Aha.... that explains it.

[Aidan]

Try a Google for "LEGIONNAIRES' DISEASE HSE".

Legionella is found in mains water supplies and it is very common in the environment. Given favourable conditions (nutrients and a suitable temperature; blood heat is about ideal) it will proliferate. If you inhale it in a contaminated aerosol, there is a good chance that it will kill you. there are documented cases of infection from hot water supplies, showers, especially.

The recommendations are to store hot water at 60 degC, distribute it so that the temperature exceeds 50 degC at the tap within 1 minute. If you need safe hot water supplies (less than 46 degC), then you fit TMVs at the point of use. Store cold water at less than 20 degC.

The definitive UK source is the HSE's L8 document 'Legionnaires' disease; The Control of Legionella Bacteria in Water Systems'. Required reading for anyone in facilities management or building services. The

60 odd pages can get a bit tedious for a DIY plumber.

Legionella has been known about for 30 years. It's a scary little bugger and it loves carp plumbing; uninsulated pipes, uninsulated tanks, dead-legs, poor HWS secondary circulation, limescale deposits in HWS cylinders, tepid water, rubber & leather washers, tallow, hemp pipe joints, etc..

[Aidan]

UK law only covers 'Providers of Residential Accomodation' and employers, who have a duty of care under the H&S at Work Acts. A house owner doesn't have such a duty of care, but legionella doesn't distinguish & could kill you in your own house if you give it a suitable opportunities.

[David Hansen]

On Mon, 15 May 2006 13:22:15 +0100 someone who may be "John McLean" wrote this:-

As someone who used to be responsible for a large number of hot water systems, air conditioning systems and a few swimming pools, I used to get reports on the concentrations of the little nasties regularly. These were nothing to do with laboratory conditions, but those experienced in "real life".

It is not something to go mad about, but it is something to manage properly. Those who stick their fingers in their ears and pretend it is not something to manage have been responsible for a number of deaths.

The Health & Safety Executive would be a good starting place.

[andyv]

I carry out risk assessments for legionella in a number of large factories. The main targets are evaporative cooling towers, but the HSE includes all the other hot and cold water services. Showers are obviously a risk since if the water is not raised to a sufficient temperature the bugs will proliferate and can be inhaled. It needs to get to over 60=BA at the cylinder and 50=BA at the outlet, to satisfy HSE.

Also included are regular hot and cold water out of taps since water stored between 20 and 45=BA will encourage legionella if not chemically treated.

I do not believe water from a hot tap at below the critical 50=BA is a serious risk since even if the bacteria are present, you need to inhale infected water droplets. Just splashing it on your face when having a wash is probably not going to cause the disease. I say probably not, but I don't believe there is any information one way or the other. I asked HSE who referred me to the Health Protection Agency, and neither could answer the question.

Accordingly I follow HSE's guidelines when assessing the risk, and make my clients aware of them, and get them to measure temperatures and periodically disinfect the tanks and pipes. However if hot (or cold) water from a tap was a legionella problem it would almost certainly show up in domestic premises which practically never consider such issues.