Single Phase to Three Phase Supply (Domestic)

We have decided to move to three phase supply mainly to reduce our EB bill.

Usual design of motors(if i am not mistaken) is 13KW above- 3 phase. Now, how do you manage to wire less than 13KW in 3 phase? That's is absurd.

"Usual design of motors(if i am not mistaken) is 13KW above- 3 phase. Now, how do you manage to wire less than 13KW in 3 phase? That's is absurd."

Actually the above is no less absurd to me !

The two 0.3 kW, one 2 kW and one 4kW 3 phase motors sitting right now in machinery in my workshop would disagree with you.

I am not talking DIY'er stuff the 4kW is on a metal spinning lathe that weighs over an imperial ton, that motor is over 50 years old, runs like a dream and has seen hard industrial use over its lifetime.

There are many good reasons for wanting a 3 phase motor under 13kW and many machinists have strong views on the subject.

I have just gone to considerable expense to buy a 7.5kW rotary convertor because I have just relocated to a country where they did not have the forsight to install 3 phase as a matter of course ( its one thing to go to the trouble of retrofit - quite another to build it in on building construction as a matter of course - domestic 3 phase is common in quite a few countries .

My choices were to replace a beautifully engineered motor with over engineereed windings or have serious hassle getting a modern motor to physically "fit" as well as giving the desirable twin speed which the old motor has ( it has two sets of windings ) not to mention issues with physical dimension, easing off cast alloy pulley wheels that have not been pulled off for decades and so on - not a plug and play swap by any means.

There are many reasons for wanting 3 phase under 13kW you are mistaken in saying its absurd - whether or not the OP has reasons that others think may make sense is another matter.

Find me a tv, radio, fridge or stove in your house that operates in 3 phase supply.

Don't you think appliance manufacturing experts, NEC or any electrical standards institution would have mandated to change already all residential supply to 3 phase long before this post was created? Nope? Then it's absurd. The guy (OP) plans to change his household supply to 3 phase.

Now, where do you think these machineries are found usually? --In industrial application, agree?

My statement in the first place is not exclusive "usual design of motor".

1 phase and 3 phase motors are like the analogy of 2 stroke and 4 stroke engine.

If you want more Power at an instant then go 2 stroke engine and 3 phase motor.

Lathe, milling and other machines in your workshop is designed to give you more power at instant, so motors are 3 phase.

The same as with heavy equipment/prime movers where 2 stroke engines are still used, even though environmental agencies banned the type of engine for public transport.

Fair enough but it was not clear to me what scope you were applying there If it was me I would have said "most domestic motors" for clarity but I suppose your original wording does stand up on the assumption that domestic washers outnumber lathes.

"Find me a tv, radio, fridge or stove in your house that operates in 3 phase supply."

Well I have a old commercial toaster that can be wired for 120/240 three wire single phase or 120/208 four wire three phase power.

Where's that leave me?

I think the key phrase there is COMMERCIAL toaster, which is different from a RESIDENTIAL toaster. Commercial sites are more likely to have 3P available as they may be doing work up to (very) light industrial.

You're going to spend thousands of dollars to convert to 3 phase and you will now have to either replace all of your appliances and lighting or install step down transformers inline with everything.

WHO put this idea in your head?????

What you're trying to accomplish is a fools game!

Spend thousands of $$$ to save hundreds of $$$ ????

Obama.... Is this you??

Sure sounds like a politician!

Agreed except for the step down transformer bit.

Assuming that the 3 phase voltage ( per phase ) is the same as the single phase voltage then the usual step is simply to take one of L1 L2 L3 and use that as a single phase supply.

Perhaps we are talking of different phase voltages as well as different phases?

By way of illustration you can create three phase 415V from single phase 230V in a static convertor by splitting L1 into L1 L2 L3 and applying a successive 120 degree phase lag between the phases by means of capacitors - not the best method of course but illustrative - then if you want single phase you simply select one of L1 L2 or L3.

Unless its different where you live then where i live (Illinois) You cannot have 3 phase power connected to a residential home only commercial property is allowed.

oilcan13

"Unless its different where you live then where i live (Illinois) You cannot have 3 phase power"

It is different in many parts of the world - judging electricity supplies globally by what happens in Ilinois (USA) is not safe - fact in Europe some countries install 3 phase and single phase outlets in domestic houses as a matter of course.

Personally I like it that way as I do have lathes and other machinery and I prefer to use induction motors - they are more reliable and run smoother - its not just a question of power and efficiency my smallest induction is 1/3 Hp.

I also have a mill and lathe that use 3 phase. the solution is a phase converter to power up these tools. Works for Me!

oilcan13

I know of only one saving there and that would be anything that contains a motor - three phase motors are more efficient than regular single phase ones but unless you are running some serious equipment you probably will not notice the diffference.

Regards energy saving - here in Europe we have a store called Ikea which has cut down the cost of replacing light bulbs with good looking LEDs ( not the ugly first generation stuff ).

Because of the low price we calculated a one year payback on our most heavily used bulbs and so replaced all when we moved into our new house which had at least 30 halogen downlighters ( 50 Watts a piece ). We have found that a 3W LED downlighter provides the same subjective lighting - you can believe the figures but we simply perferred to compare directly by replacing some and seeing how it actually looked.

If you havent already converted to LED then do take a look at what is now available and if you like what you see then perhaps you can find an outlet that gives prices as good as we have found.

Its worth calculating the payback period vs your prediction of how long you are likely to stay?

See we will be having the 1Φ meter already existing and in addition we are planning to get a 3Φ meter.

The motor rating is going to be only 1HP which is used to raise water to our water tank. Its supply is going to be single phase only.

The main idea is to get power supply continuity and to split the meter reading between the 1Φ & 3Φ meter.

Sounds like a wrong idea. If one phase fails what makes you think the others will still be there and work for you? How do you switch the phases over to your one phase loads?

It sounds like you are fallen for a scam that wants you to upgrade to a service that you do not need.

Power supply continuity isn't going to be achieved because the three phases come out of the same transformer as the individual single phases, and that transformer is powered by a single three phase line. If you want continuity you want a ring main system with two separate three phase feeds feeding from two independent transformers powered by two different lines along with a source transfer switch. As you are not a hospital or other critical load and don't have hundreds of thousands of dollars to spend however this is not practical.

I don't know who gave you this idea but as others have said it is wrong on so many levels, the most important of which is you are going to make a net monetary loss not gain.

If you want continuity, buy individual UPSs for your single phase appliances.

You realize that this will expose your family members to the risk of mixie death by ridicule?

I beg to differ. 3 phase suppliers have added fees for power factor excursions, above or below the nominal 1.0 for pure resistive loads.

They also have added fees for motor startup loads, for which they use a meter called a "Demand Meter'

Both of these deal with the power companies obligation to maintain a power factor of more or less 1.0 and to maintain the line voltage within certain range. Thus anyone who adds a huge load or changes the power factor.

For this reason many places stage their motor startups in a staggered manner and some also buy power factor correctors - both to save $$$

The reason you gave for the change from single phase to three phase connection is not convincing. If the load is more the Electrical supply agency ask to go to three phase connection sine your large load on a single phase upsets the load balancing as the domestic distribution area most of the consumers are single phase connections and to avoid unbalance on distribution the electrical supply agency directs the residents using large load to get three phase connection and distribute the single phase loads almost equally. Unless there are large 3 phase pumps for water supply ( for house and agriculture in Farm houses )most of the load is single phase in domestic use. Consult a qualified Electrical Engineer or get the job carried out by experienced electrician .

The only valid reason for having 3Ø in a home is that you need more power or have exceptionally high loads. None of the usual domestic loads requires a 3Ø supply and at small loads 3Ø is unnecessary, difficult/impossible to get appliances and much more costly.

To the power company, putting in another phase (or two) may be a practical way if other phases at 230V exist already but your existing phase does not have the amps spare.

You are doubling or trebling capacity which I expect will double or treble standing charges, on top of cable/metering installation charge.

A 3Ø transfo may be fed by 3 wires and loss of one phase makes it 1 phase, with unusably low volts to consumers.

Do you have any solid evidence that the other phases in your area stay on when yours is off?? Will they stay on when they get loaded up in the future?

It may be that your regulations require a room's sockets to be fed by only one phase or kept e.g. 2.5 metres apart if they are on different phases. 400V is dangerous and in dwelling or mixed premises it would be usual to keep phases apart in different wings or buildings, except where 3Ø was essential.

What is the total capacity of you present 8 MCB's combined?

Around here larger homes and farms can get single phase feeds as large as 1000 amps put in on a single main meter unit. A buddy of mine has a 600 amp service at his place.

Also do you have any actual three phase devices that you need to power?

If not you wont save any money on your electric bills let alone enough to offset the cost of doing a major service install plus all the other wiring as well.

you wont save money, you'll actually be shelling out more for loads designed to run on 3PH stop your project and rethink it, keep the single PH

Ummmm..... You don't know what you're doing, do you?

Step away from the electrical panel and hire a competent electrician!!!!!

Around here, the power company won't supply 3ph to a house unless you have a large machine shop on the property. They will also charge more for the service. So if this is the case where you are, your bills will be higher.

The plethora of replies above are right, this is not a good project to pursue.

Whoever put the idea in your head that 3 phase power would save money over single phase was not helping you. I'd recommend not listening to that person anymore, or at least getting a qualified second opinion before moving forward with his ideas.

And, just for the record, this forum is NOT a 'qualified second opinion.' We can offer general advice, and scream "DON'T DO IT!" when we see something obviously dangerous/stupid in a plan, but we cannot 'approve' anything. You need a licensed professional with 'boots on site' to give an approval.

Let's go for a simple example, if someone came here saying that they wanted to build a new deck on their house, made of 1/4" thick Balsa wood, with supports every 50 feet, we can all see that that will not support any real load, even without seeing the plans. If that same person showed up with what looks like a reasonable deck plan, do be build out of Pine, Oak and Engineered Wood Struts. We can say that it looks like a nice deck, that we don't see any obvious problems with it, but we cannot say 'that's great, go do it,' because we do not know where the deck is being built, or which set of building codes need to be followed in construction, or which permits need to be filed.

If you need backup power install backup power (generator). If you need continuous power for some loads install multiple UPS's until the generator comes on-line.

If you can't afford a back-up generator for the entire house, consider "load-shedding" or a "critical load" and non-critical load breaker boxes. One would be suppled by the generator. Load shedding is where you keep certain loads off when your on generator power.

How often does power go out anyway and for how long?