On 27 Jul, 00:21, Mike Holmes wrote:
I am about to convert my standard open vented DHW system with indirect
tank to a HeatBank system following the wiki @

http://wiki.diyfaq.org.uk/index.php?...DIY_Heat_Bank- many thanks
to John Stumbles for that.

While trying to figure out what specification I require for the plate
heat exchanger, I happened upon this article, which suggests hot water
should be *distributed* as well as stored at 60degC.

http://www.bsee.co.uk/news/fullstory...ding_safe_hot_...

BSEE; A free building services trade magazine that's full of adverts
and articles by chubby, middle-aged, managers in ties, who are
usually eager to bring to their readers' attention a major problem and
a SAFETY HAZARD which can only be prevented by the ACME Problem
Preventer; they usually work for, or own, ACME Inc.. It's not helped
by the editorial staff who don't work in the industry and the most
relevant text and illustrations can wind up in the editors' bin. The
articles are just filling around the paid adverts and are trimmed to
suit the available space.

American publishers can usually afford to pay an expert for an
informative article.

It's really just presenting the information in the HSE publication L8,
about preventing legionella in water systems, which is the definitive
Code of Practice on preventing legionella in the UK. L8 is legally
binding on building owners and managers who have a "duty of care"; if
there's an outbreak traced to a commercial building's water systems
and the maintenance regimes have not followed the L8 guidelines, the
managers can get charged with criminal offences.

It doesn't apply to houses, because the houseowners don't have a legal
"duty of care", BUT it is sensible to follow the same guidelines
because legionella will kill you in your own house.

Legionella is in the water supply. Given favourable conditions (nice
temperature and nutrients) it will proliferate. An ideal temperature
is about blood heat, 37 degC.
If you inhale an atomised spray of legionella infested water, you
will get infected . If you're elderly or ill, you'll probably die.

You have to keep the cold water COLD (below 20 degC). If you have a
tank you have to ensure there is at least one water turn-over per day.
Insulate tanks and pipes.

You have to keep the hot water HOT (50 degC or above). Store at 60
degC, 50degC at any hot tap within 60 seconds. If there's a risk of
scalding you need a TMV at the point(s) of use. A TMV on the store
outlet is no good.

Your system will be a combi in effect. There's little hazard if the
water is not allowed to stagnate. I'd distribute at 60 degC since this
will sterilize any bugs in the distribution pipes. Then again I
wouldn't fit a combi.

I know of someone, a very expert plumber, who managed to get an
infection from his own domestic system. He had a second house and used
the shower after the house had been vacant for some weeks. The frost
protection system had been keeping the house and the legionella warm.











DHW storage is not an issue with the Heat Bank idea. However, is it
really neccessary to distribute water at this temperature? The same
article suggests that water 45degC can cause serious scalding; I have
been figuring on using a TMV just after the output from the PHE
secondary to mix the hot down to a max of 50degC lets say, rather than
60degC.

As I get about 30l/min flow from th rising main, to be able to
guarantee my DHW is at 60degC, would mean either a very high Heat Bank/
PHE primary temperature ie probably 80degC, or a really high ouput
PHE ie 100kW.

At the end of the day the environment and costs are an issue; the
environment because I don't want to heat the store any hotter than
necc (have read in another thread that heatbanks work well with the
store as low as 70degC); costs because a the higher output PHEs
obviously cost more

Thanks

Mike