4000w light dimmer amps on macstills 2400w element

[Furynfear]

Question guys

I can't think at the moment with my electrical knowledge but when reducing the voltage on the element has anyone seen a drop in amperage. Reason I'm asking is cause I want the 3600w but power wise I would need to put in another circuit but cause its not my house I can't. So if I used the dimmer at lower voltage to compensate.

Also the reason not rated enough is I'm gonna have 2 going at the same time.

[Yummyrum]

Phase controllers don't reduce the voltage as such , they just vary how much of each half mains cycle reaches the element . So yes the average current will drop...BUT ...the peak current will still be the same

[APR]

Yes the average current will drop...BUT ...the peak current will still be the same

Yummyrum, this issue of current versus voltage is something I would like some advice on. I have produce a couple of columns of wattage from voltage, however, I now realise my calcs are wrong, however, the more I think of this issue the more I see it as being not straight forward.

Initially I looked at the voltage reduction with an analogue meter and assumed the amps would also reduce proportionally. As an example, I assumed a halving of voltage would result in a halving of current, and the resulting wattage to the element would be equal to 1/2 x 1/2 = 1/4 but now realise this is incorrect.

I have purchased an LCD display that gives current and voltage....

http://www.ebay.com.au/itm/130993449621

... however, I don't believe the values this meter displays can be multiplied out to calculate wattage through the element.

Am I correct in saying the LCD meter will not allow me to calculate wattage, and if I am, is there a simple solution to have a reasonably accurate indication of wattage through the element? Am I being too pedantic (you really don't have to answer that)!

[pulsetech]

Amps x Volts = Watts

so say 10 amps x 240 volts = 2400 watts
or 10 amps x 100 volts = 1000 watts

this is output amps from your controller not Input

if that helps

[MacStill]

you can remove the bridge on these 3600w elements and run it as 2 x 1800w from separate 10 amp circuits ;-)

dont ask me how tho :naughty:

[pulsetech]

If you have a Multi meter it will take you 3 seconds to work that out. If not have someone qualified do it.

Mac are the 2400 watt welded elements the same because that gives me some options :handgestures-thumbupleft:

[MacStill]

Mac are the 2400 watt welded elements the same because that gives me some options :handgestures-thumbupleft:

Yes they are :handgestures-thumbupleft:

[pulsetech]

Awesome so I will actually have 4 x 1200w elements in my Boiler
That's another level again of control

[APR]

Amps x Volts = Watts

so say 10 amps x 240 volts = 2400 watts
or 10 amps x 100 volts = 1000 watts
this is output amps from your controller not Input
if that helps

I am trying to get my head around the fact that the current flow will be zero at the AC voltage zero crossing point, and will peak at the peak of voltage. This means the current at any point of adjustment of the power controller will be dependent upon what part of the sinusoidal waveform is chopped out.

Would a Watt Meter be accurate when downstream of these SCR power controllers?

[Furynfear]

The only reason I haven't tested yet is cause I'm still waiting for my dimmer to get here.

May just get another 2400w of ya mac.

P. S received your element mate. Quick delivery. Thanks a million.

[punchy21]

Question guys

I can't think at the moment with my electrical knowledge but when reducing the voltage on the element has anyone seen a drop in amperage. Reason I'm asking is cause I want the 3600w but power wise I would need to put in another circuit but cause its not my house I can't. So if I used the dimmer at lower voltage to compensate.

Also the reason not rated enough is I'm gonna have 2 going at the same time.

Im not quite sure what you are asking here Furynfear? So do you have a 3600W element or a 2400W element?

[pulsetech]

Amps x Volts = Watts

so say 10 amps x 240 volts = 2400 watts
or 10 amps x 100 volts = 1000 watts
this is output amps from your controller not Input
if that helps

I am trying to get my head around the fact that the current flow will be zero at the AC voltage zero crossing point, and will peak at the peak of voltage. This means the current at any point of adjustment of the power controller will be dependent upon what part of the sinusoidal waveform is chopped out.

Would a Watt Meter be accurate when downstream of these SCR power controllers?

Your overthinking it but I understand what you mean. If you want to know your watt input
you need to take your reading with your amp meter ( CT Coil ) before your voltage controller. then times that reading x your input voltage (240v) and you have your total watts in.

Its just a resistive load after all. Like I giant light bulb

[APR]

If you want to know your watt input you need to take your reading with your amp meter ( CT Coil ) before your voltage controller. then times that reading x your input voltage (240v) and you have your total watts in.

Its just a resistive load after all. Like I giant light bulb

Thank you pulsetech. That makes a lot of sense.

[pulsetech]

No Problems :handgestures-thumbupleft:

[Furynfear]

Spoke to the the seller and he said that the amperage won't change. But I'll still test it when I get it

[pulsetech]

It will. In direct relation to the output. Turn it to half and the amp draw will be half Give or take a few losses to the controller itself

[Yummyrum]

Amps x Volts = Watts

so say 10 amps x 240 volts = 2400 watts
or 10 amps x 100 volts = 1000 watts
this is output amps from your controller not Input
if that helps

I am trying to get my head around the fact that the current flow will be zero at the AC voltage zero crossing point, and will peak at the peak of voltage. This means the current at any point of adjustment of the power controller will be dependent upon what part of the sinusoidal waveform is chopped out.

Would a Watt Meter be accurate when downstream of these SCR power controllers?

APR ,AC voltage ( and current) are RMS which means root mean square....you are absolutely right ,the instantaneous value of a mains cycle is varying.So RMS is the equivalent DC voltage that would cause the same heating effect on an element .

RMS is obtained by taking many samples throughout the cycle and averaging them .The more samples ,the greater the accuracy .You are also correct that with a pure resistive load, the current at any sample point will be proportional to the voltage


In a simple circuit where the load is a resistance and it is not fucked up by a phase controller , the RMS voltage is 0.707 x Peak voltage .
So the peak voltage is around 340V for a 240vAC

Simple meters rectify the AC voltage and scale it .............Great if its a sine wave ....but when its chopped up by a phase controller , you need a true reading RMS meter which samples and averages to get the "TRUE RMS"


Here's a Friday night crayola special. First pic is how RMS is determined on a pure sinewave and second pic is in a sinewave chopped up by a phase controller
RMS ....all negitive cycles are flipped as positive ...energy is energy :handgestures-thumbupleft:
So all the "bits" above the RMS line fill in all the gaps in the cycle below the RMS line :think:

RMS.jpg

[APR]

APR ,AC voltage ( and current) are RMS which means root mean square....you are absolutely right ,the instantaneous value of a mains cycle is varying.So RMS is the equivalent DC voltage that would cause the same heating effect on an element .

RMS is obtained by taking many samples throughout the cycle and averaging them .The more samples ,the greater the accuracy .You are also correct that with a pure resistive load, the current at any sample point will be proportional to the voltage


In a simple curcuit where the load is a resistance and it is not fucked up by a phase controller , the RMS voltage is 0.707 x Peak voltage .

Simple meters rectify the AC voltage and scale it .............Great if its a sine wave ....but when its chopped up by a phase controller , you need a true reading RMS meter which samples and averages to get the "TRUE RMS"


Heres a Friday night crayola special. Firsyt pic is how RMS is determined on a pure sinewave and second pic is in a sinewave chopped up by a phase controller

RMS.jpg

G'Day Yummyrum, Thanks for that explanation. The reason I am so interested in this issue is I have the power controller and I also have a 2000 watt T500 type boiler as well as a 3,000w 220 volt element in a keg.

My 2,000 watt boiler has 2 elements wired in parallel, and I have placed a switch in line with one element so I can run this boiler at around 1,000 watt. When trying to calculate the wattage to 1000 watt when using the power controller on 2 elements I seem to be getting more power than the 1,000w I was calculating I should be getting. The same was happening with the 3,000 watt boiler when adjusting the power controller setting with it to what I calculated should be around 1,000 watt. I do have an old Fluke 25 DMM, but it is not true RMS and is not much use to me in trying to come up with settings to give me specific wattages between different boilers and controller power settings. If a bloke just used only one boiler with the same still all the time instead of swapping gear around a bloke would not have these issues.

[Yummyrum]

APR , I think you are experiencing the inaccuracies that occur when trying to measure these things on a complex waveform.

And as the power equals the voltage X the current ,then inaccuracies in each can compound the problem.

Measuring Power is a tricky thing when phase controllers are used .

To compound things ,the typical Mains sine wave in an average Aussie home is no longer a true sine wave ...due to everything in the last 10-15 years having a switch-mode power supply , The typical sinewave is now a flat topped sinewave due to the peak current supplied to most devices connected to the mains .

Pedantic you may be ....And me :greetings-waveyellow: ....but thats OK ..sorting this shit out is good :handgestures-thumbupleft:

Brain is bashing out a Pedantic controller ATM ....Probs not going to matter a rats arse to most . :laughing-rolling: .....but it does to me :whistle: