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Water Heater Monitoring

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lordedmond:
Can I butt in on this

Excuse the safety warning but be extremely careful with CT,s

They must always be 1 connected to the ammeter or 2 fitted with a short across the out put terminals

This is the case In circuit or out

The short is the same as the meter and no harm will come to the CT

Reason they are capable of producing a high voltage on the output terminals

It's the turns ratio one turn on the primary and many on the secondary eg it a step up transformer
please be careful this does not apply to VT or PT both are 110vac and a short on these will kill them

Stuart

awemawson:

--- Quote from: awemawson on January 06, 2015, 10:56:28 AM ---
Now if the original poster measures current using his device, and sources that current from 110 volts (as he did) and gets a correlation between wattages (VxA) and indication of 12.2 watts per milliamp, what I am saying is if he sources his power from 220 volts each milliamp no long represents 12.2 Watts, it now represents 4 x 12.2 = 48.8 Watts per milliamp.

His reading of 102.8 mA on the actual heater equates to 48.8 x 102.8 = 5kW which is rather high as the heater is rated at 3.8 kW but is probably within the (in)accuracy of the equipment being used to measure it.

--- End quote ---

 :lol: The above is of course on reflection a load of old balony  :lol:

He is measuring current, which he has previously related to power at 110 at 12.2 watts per  milliamp.

So measuring the heater running off 240 his 1 mA reading is now (240 / 110) * 12.2 or 26.62 watts per milliamp. So 102.8 mA represents 2.7 kW

Again probably within the measurement accuracy  :clap:

vtsteam:
Total agreement with you on that last, Andrew :thumbup:

Or a manufacturer rated an  2500 watt element as a 3700 watt.

Nah, impossible....... :)

vtsteam:
Seriously, though....

element ages, resistance wire thins, resistance increases, wire heats hotter
hotter wire increases resistance
element ages, scale builds up on shield
scale builds up on shield, element is insulated, temp builds up inside
temp builds up, resistance wire thins further
wire thins, resistance increases, wire heats hotter
hotter wire increases resistance
etc.

BillTodd:

--- Quote from: RussellT on January 06, 2015, 06:51:15 AM ---
--- Quote from: BillTodd on January 06, 2015, 04:58:33 AM ---There is no saving in letting the water cool then reheating, unless the water is left to cool to ambient for some while.

--- End quote ---

I'm not so sure about that - if the water cools, then the heat loss will be reduced and because less heat has been lost the energy required to bring it back up to temperature will be less than would have been required to maintain the temperature.


Russell

--- End quote ---

OK not absolutely 'no saving' , but the saving are vanishingly small if the quantity of water is large and the insulation is good.

Essentially the money is better spent on insulation than on trying to match the use to the household . Unless the water drops to ambient for sometime, there is no serious power saving (don't forget to include losses in the heating process as you're trying to get it hot again in a hurry).

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