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Bit OT: Off Peak Hot Water

S

Sylvia Else

Jan 1, 1970
0
A boost element is placed at the top to provide usable hot water as
quickly as possible, not to avoid a paradoxical cooling effect.
What is your view on the mechanism that brings about mixing of hot &
colder water?

A combination of different pressures resulting from the reduction in
density of heated water and Rayleigh–Taylor instability. Where the
heating element is not an isothermal flat plate extending the width of
the tank, the latter is probably a minor effect.

Sylvia.
 
S

Sylvia Else

Jan 1, 1970
0
Why do you expect thermal convection to mix the cold and hot water?
What could cause the hot water to move down and mix with the cold water?
as the element heeat the cold water gets warm and rises it soon mixes
with the cold water above the element and produces a slower less
heated current, this continues, you won't ge whole tank circulation
currents until the whole tank is essentially at the same temperature.

It's far from obvious that the mixing is that fast. Anyway, even the
mixed water is warmer than its surroundings, and will ascend. Eventually
it's at the same temperature as its surroundings, but it has an upward
velocity, so it will rise above its proper level, in the process
displacing some of the warmer water around it downwards. Throw in some
more mixing, and the next parcel of warmed water will climb higher,
causing yet more mixing. So even if the initial parcel of heated water
cannot reach the top, these processes will ensure that it will in due
course.

The tank may then indeed be essentially all at the same temperature, but
that temperature will be lower than the temperature of the water that
was initially at the top of the tank. Cut off the power then and you
have a tank full of lukewarm water rather than a tank containing hot
water at the top and cold water at the bottom.

Sylvia.
 
K

keithr

Jan 1, 1970
0
"Sylvia Else"


** That ( oft heard) comment always grates heavily with me - cos water sure
ain't no thermal insulator !!

Nothing cools something down faster that dumping it into cold water or
pouring cold water all over it - fire brigades have relied on this fact
for quite a while now ....

Possibly more to do with the latent heat of evaporation than conduction
don't you think?
 
P

Phil Allison

Jan 1, 1970
0
"Jordan"
Phil said:
There is a option to change to Off Peak 2 which also heats between
approximately 11pm to 7am plus you receive a 5 Hour boost during the day.


** 5 hours is long enough to heat an entire tank from cold - not some "
brief period " or " top up" as you falsely alluded to. Plus it is not
"occasional".

Quote from you on the 24th:

" ... you'd miss on the occasional top up through the day (during brief
periods when demand is also low). "

Piss off, fool.


...... Phil
 
S

Sylvia Else

Jan 1, 1970
0
We've had a couple of problems with our off-peak hot water recently, and
last night, at 2:45 am (don't ask!), I noticed that the switch was still
off. So I called Ausgrid's emergency number, and they organised for
someone to come out this morning, which they did, at about 6:15 am.

Anyway, the guy simply bridged the switch, and attached a note saying
that it needed to be replaced by a time clock because of "ongoing signal
issues".

"Ongoing?"

Can they tell that there's a signal issue when the switching signal
isn't being sent? Is there a constant pilot signal?

Or did Ausgrid already know that a problem was likely, and just waited
for me to complain?

Sylvia.

Ausgrid fitted the timeswitch today.

At 11am it's letting the water heater run, which it shouldn't. So it's
been programmed wrongly. How hard can it be?

Sylvia.
 
S

Sylvia Else

Jan 1, 1970
0
Ausgrid fitted the timeswitch today.

At 11am it's letting the water heater run, which it shouldn't. So it's
been programmed wrongly. How hard can it be?

Sylvia.

I decided to do the right thing, and informed Energy Australia, via
their web contact page. I got a response today.


-------------
Thank you for your enquiry.

The information you have provided is not sufficient for us to process
your enquiry.

Please provide:

Your account number and/or address of property
Your full name
Date of birth
Home phone number
Mobile phone number:"
-------------

I did give them the address. Oh well, they've been informed. It's not my
problem anymore.

Sylvia.
 
F

F Murtz

Jan 1, 1970
0
Sylvia said:
I decided to do the right thing, and informed Energy Australia, via
their web contact page. I got a response today.


-------------
Thank you for your enquiry.

The information you have provided is not sufficient for us to process
your enquiry.

Please provide:

Your account number and/or address of property
Your full name
Date of birth
Home phone number
Mobile phone number:"
-------------

I did give them the address. Oh well, they've been informed. It's not my
problem anymore.

Sylvia.
As long as you have hot water at op rates don't worry about their stupidity
 
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