Thread: 2 Phase Power

It's the Yanks who have 2-phase or "split-phase" power - most of the outlets are 110V but you can also have 220V outlets for dryers etc.

The other instance is rural properties that are supplied with a SWER line - the transformer supplies 2 x 240v phases.

There's a couple of other possibilities - the shed could have 2 circuits which the person is mixing up with phases. The property could have 3 phase power, but the shed circuits are supplied with circuits that use 2 of the 3 phases. However, if the shed has a range of gear in it, it should be fed with a 3 phases with at least 3 circuits in the shed so the total load can be balanced across the 3 phases.

Originally Posted by RustyArc

It's the Yanks who have 2-phase or "split-phase" power - most of the outlets are 110V but you can also have 220V outlets for dryers etc.

The other instance is rural properties that are supplied with a SWER line - the transformer supplies 2 x 240v phases.

There's a couple of other possibilities - the shed could have 2 circuits which the person is mixing up with phases. The property could have 3 phase power, but the shed circuits are supplied with circuits that use 2 of the 3 phases. However, if the shed has a range of gear in it, it should be fed with a 3 phases with at least 3 circuits in the shed so the total load can be balanced across the 3 phases.

The property is in Mt Evelyn, VIC.

I have a 3 Phase lathe so I'm guessing I will either need to have a sparky set up for 3phase then? or get one of those VFR?? things?

I am in a country town Ns have 2 phase. 2 x 240 or 480v

It cN be split apparently for extra circuits but useless for 3 phase.


Dave

The Turning Cowboy

Look at the power lines coming in from the street. If there are 2 then it is single phase, if there are 4 then it is three phase. Some older houses were supplied by 3 wires - 2 phases plus neutral. This was usually done to supply the kitchen appliances with one phase and the rest of the house on the other phase. The advantage of having 2 phases supplied is that you can run twice as many single phase circuits.

My house has 3 wires coming in. It is an old house. The meter box has been replaced at some time in thedistant past . Now i have one phase supplying all light and power circuits, the other is for the off peak hot water - pretty useless.

Originally Posted by DSEL74

The property is in Mt Evelyn, VIC.

I have a 3 Phase lathe so I'm guessing I will either need to have a sparky set up for 3phase then? or get one of those VFR?? things?

Originally Posted by Avery

Look at the power lines coming in from the street. If there are 2 then it is single phase, if there are 4 then it is three phase. Some older houses were supplied by 3 wires - 2 phases plus neutral. This was usually done to supply the kitchen appliances with one phase and the rest of the house on the other phase. The advantage of having 2 phases supplied is that you can run twice as many single phase circuits.

My house has 3 wires coming in. It is an old house. The meter box has been replaced at some time in the distant past . Now i have one phase supplying all light and power circuits, the other is for the off peak hot water - pretty useless.

Avery is pretty close

nearly every street has 3 phases running down it -- the 4 wires on the cross arms of each power pole

In the old days, if you had a gas oven / gas hot water, the house would be supplied with a single phase essentially for lighting. If your oven /hot water was electric the house would be supplied with 2 phases, one for the lights the other for the oven -- which was typically on a separate 25 or 30 amp circuit.

From memory, the current supply standard is 70 amps per phase, so 2 phases equal a 140 amp supply.

Even if, as in Avery's case, the 2nd phase is only connected to the hot water, a sparky can tap into it before the meter - route the new wire via the other meter and you can enjoy the extra amps.
(off peak hot water is turned on when the supply authority passes a special code down the wire)

What is the benefit of having 2x 240V circuits? Is there a limit to how many machines etc you can run per circuit or does it mean if you blow a fuse on one the other still runs?

So from what is being said there aren't special motors etc for 2phase it is just an additional circuit of 240V. Is it better to get a VFD or have proper 3phase?

I really have no knowledge when it come to electricity other than flip a switch and it makes things go, don't stick things in power points and don't mix electricity with water.

Again - not a professional but I do believe you can get 480 volt motors but I don't think there is any real advantage over 240


Dave

The Turning Cowboy

What DaveTTC says.

It is a rural area thing.

A single phase runs into an area & is then feed through a transformer with a centre tapped 480V secondary winding.

This gives 2 x 240V outputs that are 180° out of phase.

This is then run into the property switch board as 2 phases to give extra current carrying capability.

It is used like 2 separate 240V circuits, each is fed through its own power metre.

Appart from the SWR line stuff right up the country we do not have anything that could be considerd "two phase" in this country.

There are houses that have two phases connected.....but they are generally considered as two seperate single phases.

In those SWR installations, they generally function as two seperate 240v single phases....there may be a few pump motors and the odd grain elevator that run off the 480V pair of phases, but that is a ruraly specific thing.

As has been said in the past it was far from uncommon to have two phases run into a house...but as has been said they pretty well always run as two seperate single 240V phases.

These days, there are heavier single phase submains available or they run all 3 phases into the house.

They ( electrical authorities) will expect you to justify the need for 3 phase power, but that is as easy as saying the word "airconditioners".
Saying you want to run a workshop with 3 phase machines...may...um...not be wise.....tell em you want to install air conditioners and lots of em.

It is possible to run a 415 volt single phase motor across two of 3 phases......but its not a favoured thing to do these days.

The electricity authorities are concerned about balancing their loads across the phases....so they want any heavy demand split across all 3 phases.

cheers

Originally Posted by soundman

Saying you want to run a workshop with 3 phase machines...may...um...not be wise.

Why not soundman?

Because for some it brings up the concept of industrial processes in residential areas and puts it on record.

A friend of mine, was interested in getting 3 phase connected to his house, primarily to service his shed....that he was running a business from at the time.

Being a former public servant..he has a way of speking to people and asking the right questions.

He was informed that the electrical authority "may not look on his application with favour" if it stated the purpose was to run machinery...he was told in no uncertain terms....."tell em you are installing airconditioning"...and "don't mention the war"

Because the supply authority did not consider that the residential area was properly equipped to service industrial loadings.

Remember the supply authority is responsible for supplying a stable power supply.....some guy down the street kicking a 10 Hp motor in the guts at 6 pm may cause "issues" with the power supply and people may complain.

Remember when the network was put into some of these areas, a bloke went arround, counted the houses, pulled some typical ( mrs Jones) figures out of the air, applied a peak demand equasion ( black magic), adds a little safety margin ( white magic) and comes up with the size of transformer required....that may have been back in 1960, when most houses had a single light in each room 3 power points in the kitchen, one in the laundry and a hot water system.
Come 2014, and that system is looking a bit ..um...marginal.

I know this is the way it is because, in the house I grew up in we had the neibourhood transformer in the corner of our back yard.....It caught on fire in the 60's, they replaced in the 80's because it seemed a good idea at the time but in all those years, it has been the same size tranny and still serves the same number of houses.


If the supply authority thinks your installation will compromise the network..they don't have to connect you.

cheers

Airconditioner it is!…….looks a lot like a lathe but it is an Airconditioner I swear!

Chuck a fan. That'll fool 'em

Quite a few years ago it was pretty common to run 415V/single phase on country properties because the length of the line reduced losses at a higher voltage. Usually it was terminated at a transformer down to true 240V, but the SWER system was also pretty common.
I've never understood the concept of 415/single phase - it makes no logical sense to have it.

The old SECV then went to the idea of 'justifying' the phases, so if you needed, say, 25 amps, you could get 1 phase... if you needed 50 amp, you could get 2 phase... more than that and you could get the 3 phases. Again, there's no sense in it. (The actual current draw I don't recall, but there were certain amounts to the equation)
The only logic that I can see behind 415/single phase is for oven supply (and maybe HWS's). A lot of ovens have (or at least, used to have) links in the connection block that could configure for different voltages (240 or 415), so maybe that was the thinking behind it.

I think now, it's a lot easier to get 3 phase connected, but it probably costs a premium. When I built 15 years ago, I had 3 phase in the pit, so I ran all phases to the house and there were no questions asked. Then again, I ran 60Amp per phase, so they didn't quibble my requirements