Talking copper tubning. When I was a kid dad taught me to "sand", flux and tin the fittings and wipe with a wet rag. Insert and solder.

The tinning step wasn't necessary and I didn't know any better. Take say 12 YO (tin step) and 20 YO (no tin step).

You still need the tin step for old work occasionally.

 

That’s to get a good clean joint. Tin based flux is available and helps create a good clean joint

 

Talking copper tubning. .

OK this was all lead, pipe and joint, it stood me in good stead when I had to do lead H.V. Armoured cable gland.
Max.

 

MrChips. Could you kindly explain RMS as you said you could? I have had a brief reading of the subject but I’m sure you or any of these other knowledgeable guys could explain it properly.
Thanks

 

Here is the lowdown on what RMS means.

Your power utility is supplying you AC power as a 325V amplitude sine wave.

(The bottom graph is the output of your isolation transformer).
(The top graph is the output when one of the terminals of the secondary winding is grounded.)

Since the electric utility is providing you with power, it needs to know how much power you are consuming, not voltage, and that will depend on your load.

For simplicity, let us assume that your load is 1 ohm. We use 1Ω as this will keep the math simple.
Power is calculated as P = V x V / R.

Since the voltage supplied is continuously changing, sometimes the voltage is 325V, sometimes -325V, and sometimes 0V, and every value in between +325V and -325V.

When the voltage is at the maximum 325V, the power delivered is 325V x 325V / 1Ω = 105,625 watts = 106kW
Notice that when the voltage is -325V, the power delivered is -325V x -325V / 1Ω = 106kW.
There is no negative power.

In reality, since the voltage is AC, sometimes you are drawing 106kW, other times it is 0kW. Hence your average power consumed must be less the 106kW.

What is the correct average power?

Here we have to do some fancy mathematics to work out the average power delivered in the AC sine wave. It turns out that the average power in the sine wave in our example is 106kW divided by 2 = 53kW. (This is for sine waves. Other shapes have different conversion factors.) So you are really only consuming half as much power than if you were being supplied with a constant 325VDC voltage.

How much DC voltage would give you equivalent power of 105,625 / 2 = 52,813W ?
For the answer, we take the square root of this power.
√52813 = 230

Hence the power delivered with 325V amplitude AC sine wave is equivalent to the power delivered with 230VDC.

We arrived at this answer by the following mathematical process described above in the following 3 steps:

1) We calculated the square of the sine wave amplitude to determine power.
2) We calculated the average or mean power.
3) We calculated the square root of the mean power to convert back to voltage.

In other words, we calculated the root mean square of the sine wave voltage, i.e. the RMS voltage (or rms).

That is, 325V amplitude sine wave provides the same power as 230VDC.

AC voltage is specified using the RMS value, i.e. 230VAC is the RMS voltage of a 325V amplitude sine wave.

√2 = 1.414

1 / 1.414 = 0.707

Thus

RMS Voltage = Amplitude x 0.707
Amplitude = RMS Voltage x 1.414

where Amplitude = VPK

 

Wow MrChips that’s incredibly descriptive and explains it in great detail. Thank you.
VRMS stands for Volts RMS, VPK stands for Volts Peak I assume but what does VPP translate to?

 

Wow MrChips that’s incredibly descriptive and explains it in great detail. Thank you.
VRMS stands for Volts RMS, VPK stands for Volts Peak I assume but what does VPP translate to?

You are most welcome.

VPP stands for Volts Peak-to-Peak.

VPP = VPK x 2

 

Thanks MrChips.
So out of curiosity would I use the same equation to calculate amplitude in North America?
Ie Amplitude = RMS Volts x 1.414
So their amplitude would equate to 110 x 1.414 = 156 VPK?

 

Thanks MrChips.
So out of curiosity would I use the same equation to calculate amplitude in North America?
Ie Amplitude = RMS Volts x 1.414
So their amplitude would equate to 110 x 1.414 = 156 VPK?

Correct.

In North America, 120VAC is standard.
120V x 1.414 = 170V.

Note that when building DC power supplies, the DC rectified voltage into a storage capacitor will reach the peak of the AC voltage. Hence the 1.4 factor must be taken into account.

 

Thanks MrChips. That’s something to learn on another day