Solar and Legionella

sydthebeat

Can some solar expert educate me on the precautions inherent in solar systems against the risk of legionella bacterium??

Say i go away for a weeks holidays in october.... (no recession jokes! )
Say the solar system maintains an average range of 20 - 40 deg in my cylinder for this week.... thus creating ripe breeding ground for legionella.
I come home from my hols, on a nice day, to see a perfect 35deg in my cylinder and i think.. .great, ill grab a quick shower now before i unpack..... a deadly situation.....

What should be done to minimise any possible risk??
Should the cylinder be completely flushed before use??
Should the cylinder be set to heat to at least 60deg for a period of time before use??

sydthebeat

sydthebeat wrote: »

Can some solar expert educate me on the precautions inherent in solar systems against the risk of legionella bacterium??

Say i go away for a weeks holidays in october.... (no recession jokes! )
Say the solar system maintains an average range of 20 - 40 deg in my cylinder for this week.... thus creating ripe breeding ground for legionella.
I come home from my hols, on a nice day, to see a perfect 35deg in my cylinder and i think.. .great, ill grab a quick shower now before i unpack..... a deadly situation.....

What should be done to minimise any possible risk??
Should the cylinder be completely flushed before use??
Should the cylinder be set to heat to at least 60deg for a period of time before use??

Quick answer is to fire up the immersion/oil/gas or whatever to raise it to 60C for a few minutes.

Energysaver

Hi Syd
I'm not a solar expert but I have solar for hot water and a pellet boiler for heating and hot water when solar isn't able to provide full temperature (late autumn thru to early spring). I'd say that 35 degrees is a bit cool for taking a shower - would be for me anyway. You should check with your solar installer, but I think SEI recommend that the temperature of your hot water cylinder is set to about 60 degrees in order to kill legionaires bacteria. What secondary heat source do you use for your hot water in the winter? You should probably use this back up source to bring the water up to 60 degrees before having your shower - better save than sorry.
Dave

sinnerboy

Any ( simple ) way to automate this DB ?

sydthebeat

Deleted User wrote: »

Quick answer is to fire up the immersion/oil/gas or whatever to raise it to 60C for a few minutes.

does the lay person know this however?? i think not.

are systems easily drained??
should they be drained quite frequently??

Edit:
Cranagh... this really is a hypotetical question... to investigate the risk management of solar systems.

copper12

70 to 80 °C (158 to 176 °F): Disinfection range
At 66 °C (151 °F): Legionellae die within 2 minutes
At 60 °C (140 °F): Legionellae die within 32 minutes
At 55 °C (131 °F): Legionellae die within 5 to 6 hours
Above 50 °C (122 °F): They can survive but do not multiply
35 to 46 °C (95 to 115 °F): Ideal growth range
20 to 50 °C (68 to 122 °F): Legionellae growth range
Below 20 °C (68 °F): Legionellae can survive but are dormant
Get a timer for you emersion time it for one hour
Set it for a time when you have maximum solar gain but before you would usually use the showers

Energysaver

That's very useful to know copper12.

Set it for a time when you have maximum solar gain but before you would usually use the showers

Wouldn't it be more energy efficient to set the immersion to come on for an hour after maximum solar gain so that the sun provides most of the energy to raise the water to 60 °C? In the summer I set my boiler to come on early evening (say 6p.m.) to boost the temperature to 60 °C if the sun hasn't managed to get the water to that temperature during the day. In autumn/winter/spring the boiler will be on anyway for the central heating.
What do you think?

copper12

This depends on the concern of the end user
People have different life styles
I don’t think there is any real danger of legionaries disease; becoming an issue’ if the hot water is used every day
It’s when its left stagnant i.e. two or three day without use;
timing your emersion to come on lets say 7 to 8 o’clock; summer evening, again depends on lifestyle, will eliminate the treat of legionaries decease.
The cost would be minimal.