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RossW
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Joined: 25/02/2006
Location: Australia
Posts: 495

Posted: 11:24pm 31 Jul 2010

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KarlJ said standing heat loss for a 300L tank at 70deg is 2.9KW/day (not kw hr in this case Gordon as we're talking an energy loss over 24hrs) thus you'd be wasting at normal electricity rates 0.60c just is what is lost to the surrounding air.

I just don't "get" how many people seriously don't understand the differences between kW and kWh

Karl, if you are saying 60c/day, you're obviously meaning it's 2.9 kWh that is being used per day.

If it really takes 2.9 kilowatts just to maintain the tank temperature, it would be 2.9 kilowatts * 24 hours = 69.6 kWh per day.

2.9 kWh/day means it needs 120 watts to keep it warm - or that it would run a 4 kW element for about 40 minutes a day.

KarlJ

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Joined: 19/05/2008
Location: Australia
Posts: 1178

Posted: 03:00am 01 Aug 2010

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Perhaps the wording of the standard is not upto standard.
as i recall "standing heat loss for a 315L tank shall not exceed 2.9KW/day"
this is advice to us from SAI global.

if it should be KWhr/day I assume this could be confused with 2.9KW/hr x 24 hrs
and perhaps why they stated it as 2.9KW/day. as someone may build a tank that looses 2.9KW/hr instead of the intent 120W/hr.

It is not stated as 120W/hr as it is a standing loss which is not constant ie may loose 150W/hr in the first 5 hrs and 20W/hr for the last 5 hrs.

Watt I do know is its probably a moot point as this thread was about smart meters which
no one has had a dig at the lack of knowledge around this rather jump up and down about a side issue.

Luck favours the well prepared

VK4AYQ
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Joined: 02/12/2009
Location: Australia
Posts: 2539

Posted: 03:31am 01 Aug 2010

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Hi Ross

Karl made the point of saying 2.9 kw a day in other words 2900 watts a day, watt is your problem with that? That is the equivalent energy loss by terrestrial radiation not a power input figure, to maintain temperature status, the energy input must be more than that, whether by solar collection or by boost from the power source.
A 2400 watt booster element would require 1.2 hours to do so, or a twin solar collector panel would take 32 minutes.

All the best

Bob

Foolin Around

VK4AYQ
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Joined: 02/12/2009
Location: Australia
Posts: 2539

Posted: 03:43am 01 Aug 2010

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Hi Karl

I like your idea on a master switch on the power that turns all unnecessary things of when not at home, except the buglier alarm of course. I notice my meters run backwards all day so that would be counted as feed in at 50 cents per 1000 watts, that is the Energex feed in contract rate I am on, and at night when power is required they go forward at 19.7 cents per 1000 watts, that would be if I had a smart meter installed {still waiting after six months}.

When the dust settles I can feed in 32 kw per day according to the contract.

All the best

Bob

Foolin Around

KarlJ

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Joined: 19/05/2008
Location: Australia
Posts: 1178

Posted: 05:03am 01 Aug 2010

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Bob do you mean 32KW /hr couldnt help but laugh as someone else made the "mistake"
bring it ON..

Luck favours the well prepared

VK4AYQ
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Joined: 02/12/2009
Location: Australia
Posts: 2539

Posted: 01:08pm 01 Aug 2010

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Hi Karl

No, I meant what I said, with the GTI I have I can feed 32,000 watts a day into the grid under the terms of the initial contract.
To feed 30KWH into the grid I have to upgrade the contract with Energex.

All the best

Bob

Foolin Around

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