I have a Vaillant EcoMax Pro condensing boiler and also a Superduty fast
recovery hot water cylinder. When the boiler was installed the installer set
the boiler temp to 65C. A year later, a different guy from the same firm
came round to do the 1 year warranty check and insisted it should be 70C.
What is the optimum value, if there is such a thing? Or would I be right in
thinking that it's the return temp that's more important, and that it should
be 55C or less?

If it's the return temp that's important, then I have a supplementary
question... I understand that hot water in a cylinder should be heated to
60C in order to prevent the growth of Legionella bacteria. Is this correct,
and if so, how do I reconcile the two requirements -- return at 55C or less,
but hot water = 60C?

Ta,

Steve S
--

"Steve S (another one)" wrote in message
...


If it's the return temp that's important, then I have a supplementary
question... I understand that hot water in a cylinder should be heated to
60C in order to prevent the growth of Legionella bacteria. Is this
correct, and if so, how do I reconcile the two requirements -- return at
55C or less, but hot water = 60C?

The 60C is only for the first use, to 'kill' any harmful bacilli in the
equipment.

Mary

"Mary Fisher" wrote :
"Steve S (another one)" wrote :

If it's the return temp that's important, then I have a supplementary
question... I understand that hot water in a cylinder should be heated to
60C in order to prevent the growth of Legionella bacteria. Is this
correct, and if so, how do I reconcile the two requirements -- return at
55C or less, but hot water = 60C?

The 60C is only for the first use, to 'kill' any harmful bacilli in the
equipment.


Hmm. Could the tank in the loft not be a potential further source of
contamination? It's not accessible to anything larger than an insect, but...
I'm just trying to anticipate my wife's arguments here, and she's somewhat
paranoid about germs.

On Fri, 14 Mar 2008 11:58:07 GMT someone who may be "Steve S
\(another one\)" wrote this:-

Hmm. Could the tank in the loft not be a potential further source of
contamination? It's not accessible to anything larger than an insect, but...

It shouldn't be accessible to an insect, as insect screens should be
fitted to it.

I'm just trying to anticipate my wife's arguments here, and she's somewhat
paranoid about germs.

Germs have always existed and always will. Your wife breathes them
in all the time.


--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54

"Steve S (another one)" wrote in message
...

"Mary Fisher" wrote :
"Steve S (another one)" wrote :

If it's the return temp that's important, then I have a supplementary
question... I understand that hot water in a cylinder should be heated
to 60C in order to prevent the growth of Legionella bacteria. Is this
correct, and if so, how do I reconcile the two requirements -- return at
55C or less, but hot water = 60C?

The 60C is only for the first use, to 'kill' any harmful bacilli in the
equipment.


Hmm. Could the tank in the loft not be a potential further source of
contamination? It's not accessible to anything larger than an insect,
but... I'm just trying to anticipate my wife's arguments here, and she's
somewhat paranoid about germs.

Does she breathe?

"David Hansen" wrote in message
news

I'm just trying to anticipate my wife's arguments here, and she's
somewhat
paranoid about germs.

Germs have always existed and always will. Your wife breathes them
in all the time.

Oh, sorry David, I sent a reply before reading yours.

Mary


--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54

Mary Fisher wrote:

"Steve S (another one)" wrote in message
...

"Mary Fisher" wrote :
"Steve S (another one)" wrote :

If it's the return temp that's important, then I have a supplementary
question... I understand that hot water in a cylinder should be heated
to 60C in order to prevent the growth of Legionella bacteria. Is this
correct, and if so, how do I reconcile the two requirements -- return at
55C or less, but hot water = 60C?

The 60C is only for the first use, to 'kill' any harmful bacilli in the
equipment.


Hmm. Could the tank in the loft not be a potential further source of
contamination? It's not accessible to anything larger than an insect,
but... I'm just trying to anticipate my wife's arguments here, and she's
somewhat paranoid about germs.

Does she breathe?

That's the least of her worries, but it's nice to see the technical
ignorami (Dynamo Hansen and the She-Devil) focusing on the wrong thing.

On Fri, 14 Mar 2008 15:31:03 +0000 someone who may be
(Steve Firth) wrote this:-

That's the least of her worries, but it's nice to see the technical
ignorami (Dynamo Hansen and the She-Devil) focusing on the wrong thing.

Nice try. However, those of us who were once responsible for water
quality monitoring in a variety of systems, including olympic sized
swimming pools and numerous air conditioning systems, know just how
to evaluate such assertions.

Should you wish to make some more wide of the mark assertions you
may have the last word.


--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54

On Fri, 14 Mar 2008 15:31:03 +0000, Steve Firth wrote:

Hmm. Could the tank in the loft not be a potential further source of
contamination? It's not accessible to anything larger than an insect,
but... I'm just trying to anticipate my wife's arguments here, and
she's somewhat paranoid about germs.

That's the real problem.

Does she breathe?

That's the least of her worries, but it's nice to see the technical
ignorami (Dynamo Hansen and the She-Devil) focusing on the wrong thing.

They are focusing on the right thing, a person "somewhat paranoid about
germs". We have very effective immune systems that'll deal with billions
of bacteria a day.

Assuming this is a modern installation and the roof tank is fitted with a
full By Law 30 kit. Contamination of the water in that tank is a minimal
risk. It's mains fed with chlorinated water it is highly unlikely anything
will grow in or get into the tank.

--
Cheers
Dave.

"Mary Fisher" wrote in message
t...

"Steve S (another one)" wrote in message
...


If it's the return temp that's important, then I have a supplementary
question... I understand that hot water in a cylinder should be heated to
60C in order to prevent the growth of Legionella bacteria. Is this
correct, and if so, how do I reconcile the two requirements -- return at
55C or less, but hot water = 60C?

The 60C is only for the first use, to 'kill' any harmful bacilli in the
equipment.

I wonder why you have to boil stuff for several minutes to kill bacteria if
an initial burst of heat will do the job?

David Hansen wrote:

Nice try. However, those of us who were once responsible for water
quality monitoring in a variety of systems, including olympic sized
swimming pools and numerous air conditioning systems, know just how
to evaluate such assertions.

snork

You were a pool boy and a janitor? That figures.

It's quite interesting, then, that some solar heating companies and many
public bodies say that the hot water should be heated to at least 60C at
least once per week, if a shower is to be fed. However, it would appear that
any temperature above 50 will kill them (Legionella bacteria, not the public
bodies!), if slowly, according to some sources. They apparently survive
quite well in cold water, by the way.

"dennis@home" wrote in message
...


"Mary Fisher" wrote in message
t...

"Steve S (another one)" wrote in message
...


If it's the return temp that's important, then I have a supplementary
question... I understand that hot water in a cylinder should be heated
to 60C in order to prevent the growth of Legionella bacteria. Is this
correct, and if so, how do I reconcile the two requirements -- return at
55C or less, but hot water = 60C?

The 60C is only for the first use, to 'kill' any harmful bacilli in the
equipment.

I wonder why you have to boil stuff for several minutes to kill bacteria
if an initial burst of heat will do the job?

The worry in water heting equipment is about specific bacilli.

What bacilli do you kill at several minutes of boiling? And how does any
central heating/domestic hot water system maintain boiling for several
minutes?

Mary

"AJH" wrote in message
...

....

I'm not sure of the recommended temperature to kill Legionella
bacteria but they fester in warm re circulating or stagnant systems,

er - they have to be there at the start ...

On Fri, 14 Mar 2008 09:39:22 +0000, Steve S \(another one\) wrote:

I have a Vaillant EcoMax Pro condensing boiler and also a Superduty fast
recovery hot water cylinder. When the boiler was installed the installer
set the boiler temp to 65C. A year later, a different guy from the same
firm came round to do the 1 year warranty check and insisted it should
be 70C. What is the optimum value, if there is such a thing? Or would I
be right in thinking that it's the return temp that's more important,
and that it should be 55C or less?

If it's the return temp that's important, then I have a supplementary
question... I understand that hot water in a cylinder should be heated
to 60C in order to prevent the growth of Legionella bacteria. Is this
correct, and if so, how do I reconcile the two requirements -- return at
55C or less, but hot water = 60C?

Ta,

Steve S

This is my take on the settings.

If the boiler knows the difference between doing the HW and CH then the
best settings (IMHO) is HW max and CH as low as possible but still
capable of heating the house. I think the Vaillant does know the
difference if it is wired up correctly, but that may including using
proprietary controls.

If the boiler does not know the difference between HW and CH (almost all)
then I suggest setting the flow at about 10C more than the thermostat on
the HW cylinder, if that's not enough to heat the house then consider
adding more radiators. Typcically HW temps are sett to 55-60C so the
primary flow temp should be 65-70C.

HTH

--
Ed Sirett - Property maintainer and registered gas fitter.
The FAQ for uk.diy is at http://www.diyfaq.org.uk
Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html
Choosing a Boiler FAQ http://www.makewrite.demon.co.uk/BoilerChoice.html

"Mary Fisher" wrote in message
t...

"dennis@home" wrote in message
...


"Mary Fisher" wrote in message
t...

"Steve S (another one)" wrote in message
...


If it's the return temp that's important, then I have a supplementary
question... I understand that hot water in a cylinder should be heated
to 60C in order to prevent the growth of Legionella bacteria. Is this
correct, and if so, how do I reconcile the two requirements -- return
at 55C or less, but hot water = 60C?

The 60C is only for the first use, to 'kill' any harmful bacilli in the
equipment.

I wonder why you have to boil stuff for several minutes to kill bacteria
if an initial burst of heat will do the job?

The worry in water heting equipment is about specific bacilli.

What bacilli do you kill at several minutes of boiling? And how does any
central heating/domestic hot water system maintain boiling for several
minutes?

The correct answer is not many, it takes longer for most.
However you kill a lot of each type.

"Ed Sirett" wrote :

This is my take on the settings.

If the boiler knows the difference between doing the HW and CH then the
best settings (IMHO) is HW max and CH as low as possible but still
capable of heating the house. I think the Vaillant does know the
difference if it is wired up correctly, but that may including using
proprietary controls.

If the boiler does not know the difference between HW and CH (almost all)
then I suggest setting the flow at about 10C more than the thermostat on
the HW cylinder, if that's not enough to heat the house then consider
adding more radiators. Typcically HW temps are sett to 55-60C so the
primary flow temp should be 65-70C.


Thanks Ed. Just what I was looking for.

In article et,
"Dave Liquorice" writes:
They are focusing on the right thing, a person "somewhat paranoid about
germs". We have very effective immune systems that'll deal with billions
of bacteria a day.

....but only if you keep exposing the immune system to germs.
It stops working if you stop exposing it to germs, and that
includes Legionella.

Assuming this is a modern installation and the roof tank is fitted with a
full By Law 30 kit. Contamination of the water in that tank is a minimal
risk. It's mains fed with chlorinated water it is highly unlikely anything
will grow in or get into the tank.


--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

"dennis@home" wrote in message
...


"Mary Fisher" wrote in message
t...

"dennis@home" wrote in message
...


"Mary Fisher" wrote in message
t...

"Steve S (another one)" wrote in message
...


If it's the return temp that's important, then I have a supplementary
question... I understand that hot water in a cylinder should be heated
to 60C in order to prevent the growth of Legionella bacteria. Is this
correct, and if so, how do I reconcile the two requirements -- return
at 55C or less, but hot water = 60C?

The 60C is only for the first use, to 'kill' any harmful bacilli in the
equipment.

I wonder why you have to boil stuff for several minutes to kill bacteria
if an initial burst of heat will do the job?

The worry in water heting equipment is about specific bacilli.

What bacilli do you kill at several minutes of boiling? And how does any
central heating/domestic hot water system maintain boiling for several
minutes?

The correct answer is not many, it takes longer for most.
However you kill a lot of each type.

Leaving the most powerful (therefore 'dangerous') to survive then!

On Fri, 14 Mar 2008 18:49:47 GMT someone who may be "Steve S
\(another one\)" wrote this:-

However, it would appear that
any temperature above 50 will kill them (Legionella bacteria, not the public
bodies!), if slowly, according to some sources. They apparently survive
quite well in cold water, by the way.

They survive, but don't do a lot. Raise the temperature and they
rapidly multiply and so are likely to reach dangerous
concentrations. Raise the temperature more and they die.


--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54