Switching between elements

[Modernity]

does anyone know of a controller that's lets you run two or three elements while switching a single phase supply between them on a continual bases.
This idea was offered to me sometime ago as a way of increasing the available heating surface area in a pot still.
So that each element may receive 1/3 of a second on 2/3's of a second off, one is on while the other two elements are powered. x_x x_x x_x

[1 2many]

Mate I think you maybe starting to over complicate things, I don't see the need. :-B

Keep it simple then there is less to go wrong. :handgestures-thumbupleft:

[Andy]

:text-+1:
with the amount of current and turbulence in the boiler i dont think and increase in surface area would generate any change in the run

[scythe]

Interesting idea.
Must be a large pot where 3 elements are needed to evenly heat the boiler.

It would be possible, although the principle is similar the execution will undoubtedly be different, I remember building an LED roulette wheel when i was doing school electronics, the kit was from Jaycar IIRC.
no doubt a google search will sort you out.

[1 2many]

Interesting idea.
Must be a large pot where 3 elements are needed to evenly heat the boiler.

It would be possible, although the principle is similar the execution will undoubtedly be different, I remember building an LED roulette wheel when i was doing school electronics, the kit was from Jaycar IIRC.
no doubt a google search will sort you out.

Two completely different things shifting 3v dc at 20 mA is a little different to trying to switch 3 elements 240v ac 10 amps
on a single phase line. All you need is a PWM controller that switches a lot faster than Op wanted and does the job. ;-)

[MacStill]

For a large boiler commercial operation running electric I recommend each element run through it's own breaker, with a voltage controller on one element.

Once up to temp you simply switch off the element/s that aren't required and adjust things on the controlled element.... too easy.

If you run all your elements through the same breaker and one blows it turns into a bad day, with large wash volumes you want to be able to keep running instead of having to drain to replace an element to get going again.

Hope that makes sense, maybe a sparky could chime in and explain it better.

Cheers,

Mac.

[OzKev]

does anyone know of a controller that's lets you run two or three elements while switching a single phase supply between them on a continual bases.
This idea was offered to me sometime ago as a way of increasing the available heating surface area in a pot still.
So that each element may receive 1/3 of a second on 2/3's of a second off, one is on while the other two elements are powered. x_x x_x x_x

I assume you are trying to achieve a lower watt density? If so, run 4 elements in parallel series, and you will have 4 elements running at the total power of 1. Your sparky can probably explain it better.

But realistically, if you need to do that, then you have the wrong elements to start with.

[res]

I like the idea of running my two elements at reduced power rather then one at full and the other low or off. I have just one controller and use separate circuits for each element. Eventually I'd like to build a second controller to achieve this end. Maybe you could do the same. :think:

[Andy]

I assume you are trying to achieve a lower watt density? If so, run 4 elements in parallel series, and you will have 4 elements running at the total power of 1. Your sparky can probably explain it better.

But realistically, if you need to do that, then you have the wrong elements to start with.

it been a while but i thought if they are parallel they will be drawing the max voltage across all of them, where as a series circuit the voltage would be divided evenly between them all.

[OzKev]

2400w / 2 * 2 = 2400w

[Modernity]

Issue #1
My 150+ ltr pot is a converted jacketed steam kettle. See
https://www.google.com.au/search?q=stea ... 24&bih=668

Issue #2
My current power supply is domestic single phase

So given the jacket on the pot, it's a bridge to far to direct heat. I have been thinking to circulate oil heated in a rims style heat exchanger setup.

I'm tiring to keep gas out the equation if possible due to the confined space.

[Triangle]

I assume you are trying to achieve a lower watt density? If so, run 4 elements in parallel series, and you will have 4 elements running at the total power of 1. Your sparky can probably explain it better.

But realistically, if you need to do that, then you have the wrong elements to start with.

it been a while but i thought if they are parallel they will be drawing the max voltage across all of them, where as a series circuit the voltage would be divided evenly between them all.

Hi mate,

OzKev means a series parallel circuit that looks like this;


There's 2 resistors in parallel at the top and the same at the bottom and then both in series with eachother. The resistors in parallel are 1/2 the resistance (R1XR2/R1+R2), then add the 2 halves together to end up with the original resistance as 1 element.

You could also wire them in a square if you could imagine the layout, which would be 3 in series with the 1 parallel. Total R will be 75% of the 1 element and current draw will be a little more.

[Andy]

cheers TGS!

[1 2many]

Issue #1
My 150+ ltr pot is a converted jacketed steam kettle. See
https://www.google.com.au/search?q=stea ... 24&bih=668

Issue #2
My current power supply is domestic single phase

So given the jacket on the pot, it's a bridge to far to direct heat. I have been thinking to circulate oil heated in a rims style heat exchanger setup.

I'm tiring to keep gas out the equation if possible due to the confined space.

Sounds like you are in a bit of a pickle with power, :think:

So do you have element ports on the boiler?

Or are you planning to just use heated oil to heat the boiler? :scared-eek:

[Modernity]

The boiler I have For the heat exchanger is a ex commercial espresso machine boiler holding about 10ltrs. I can set it up to hold 3-4 elements if need be. It has an internal water level sensor and numerous ports.
I want it to heat oil and then pump the hot oil to the jacketed pot still and back to a recirculating header tank so there would be no pressure in the system.

Someone and I can't remember who told me that it is possible to switch a single phase between a number of elements without increasing the current draw, but increasing the heating efficiency due to the increased surface area available.

[1 2many]

Someone and I can't remember who told me that it is possible to switch a single phase between a number of elements without increasing the current draw,

Yes it is possible, with a purpose built controller.

but increasing the heating efficiency due to the increased surface area available.

I feel you are chasing efficiency way too far, it will depend on the whole setup.

Basically you can't get out more than you put in.

[Triangle]

I did a bit of sketching of various circuit diagrams to try and do this with contactors and timers but it works out reasonably expensive, something like an Omron Zen V2 would do the trick but still need output contactors.

What wattage elements are you running/planning on running?

[1 2many]

Ok so have one standard 240 volt 10 amp power outlet .

You want to heat oil so you can heat your 150ltr boiler , pump heated oil, then you will need a pump for your condensers maybe some lighting.

Good luck :))

[Triangle]

I'm with 1 2many, heat exchanger is a massive power loss not to mention plumbing, hot oil etc.

Your 'get out of jail free' answer, while not ideal would be a power board with 3 digital timers mounted on it. Set all 3 times to the exact second. Set timer on and off periods on each timer for each heater, with the aim that you don't have an overlap. Even a quality timer rated at 10A contacts is only going to last a finite amount of time.

[phonetic]

3 phase power, 150 litre pot 3 x 3,6kW elements :scared-eek: :shock: :o