Sparky expert

[Brenda Irwin]

I have two circuits on my old power box to service all powerpoints in the house.
Any idea how much power you can draw off them before the safety trips?
Is it 2400 watts each or much more?

 

[AlmostBob]

It depends on the breaker, and the load
most old household power circuits are 15 amps
in a purely resistive circuit (Like fishtank heaters)that is 15*240 =3600watts
in any inductive or capacitive circuit (fridges, motors, airconditioners, washing machine, television, computer, just about everything except an incandescant light bulb) there is a non-linear relationship between current and power, the 'power factor' is the cosine value of phase shifts added or lost to capacitance and inductance, can total zero power at the load, and many amps in the circuit......
too much detail
suffice that 15 amps can trip the breaker when the circuit is delivering much less than 3600 watts, 2400watts is a good planning value,
a sparky and more circuits

 

[evand]

Wow Bob..impressive...even i don't remember that much power factor theory LOL.

Brenda,

On the circuit breaker (or fuse) should be a little number. It should say '20' for a power circuit and '10' for a light circuit.

This means it is a 20 amp circuit breaker. The cable going to the power points would be 2.5 mm sq which is rated at 20 amps as well.

So, in sparky talk, its a 20 amp circuit. Meaning 20 amp x 240 volts = around 4800 watts max. The circuit breaker could trip with less tho for reasons outlined above by Bob but you usually just do rough calculations ignoring power factor.

For your purpose, you don't need to worry about it.

 

[Brenda Irwin]

So I guess a total of 2350 watts for 27 fish tanks with heaters during next winter means I am going to have to see a sparkie?

 

[evand]

The load should be ok on one 20 amp circuit. You might have trouble with all the power boards tho. Or get new GPOs installed.

If the all have plug packs you might need lots of single GPOs rather then doubles.

So I guess a total of 2350 watts for 27 fish tanks with heaters during next winter means I am going to have to see a sparkie?

 

[units4me]

Picky, i know, but be careful with fuse/breaker ratings for power circuits. Some of the older 2.5mm wiring is slightly smaller in size and is in fact only rated at 16 amps (not 20A).

To be safe, and legal, make sure all older (including bare earth TPS and older) power cables have a maximum CB rating of 16 amps.

More recent TPS power cables with insulated earth are rated at 20 A.

 

[Aaron Sice]

i love how sine, cosine and tangent have applications far and wide beyond geometry.

 

[craigb]

me too1 i just cant remember the three corners??

 

[evand]

Yeah that's true. In that case it wouldn't be 2.5mm sq cable, it would be the old 7/0.67 inch sq. Meaning 7 strands of 0.67 sq coppper.

It should have a 16 amp circuit breaker or fuse.

Picky, i know, but be careful with fuse/breaker ratings for power circuits. Some of the older 2.5mm wiring is slightly smaller in size and is in fact only rated at 16 amps (not 20A).

To be safe, and legal, make sure all older (including bare earth TPS and older) power cables have a maximum CB rating of 16 amps.

More recent TPS power cables with insulated earth are rated at 20 A.

 

[nomadic]

me too1 i just cant remember the three corners??

S=sin
C=cos
T=tan
O=opp (opposite)
A=adj (adjacent)
H=hyp (hypotenuse)

Silly Old Hags Can’t Always Hide Their Old Age

S=O/H C=A/H T=O/A

this mnemonic has always helped me

 

[Rixter]

Yeah that's true. In that case it wouldn't be 2.5mm sq cable, it would be the old 7/0.67 inch sq. Meaning 7 strands of 0.67 sq coppper.

You can also get one solid strand 2.5mm sq - 1/1.78 ...usually contained in 2 core & earth TPS for domestic purposes.