Three phase power and machinery across south-east Melbourne
A machine arrives on a Tuesday and needs a supply that does not exist. Three phase work on a commercial site is rarely about the machine and almost always about what the building can deliver to it.
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Plant is arriving and the supply may not carry it
Three phase problems are nearly always supply or balance problems. Both are measurable, which means both can be answered before you commit.
- New plant or machinery specifying a three phase supply the site does not have.
- Motors that nuisance trip, run hot, or fail earlier than they should.
- Voltage imbalance between phases, or one phase carrying noticeably more load.
- A commercial kitchen being fitted into a tenancy provisioned for retail.
- Compressors, lifts or refrigeration that start hard enough to dim the lights.
- Available capacity that has never been measured, only assumed.
- Equipment being relocated within a site to a position with no suitable supply.
- A distributor upgrade that needs coordinating before plant arrives.
What three phase work actually covers
Maximum demand is calculated against your actual equipment, not a rule of thumb. That calculation decides the cable and the cost.
- Maximum demand assessed against the actual equipment schedule.
- Supply upgrades coordinated with your electricity distributor.
- Three phase sub-circuits and isolation to individual machines.
- Motor circuits with correct protection, starting arrangements and isolation.
- Load balanced across phases, and imbalance measured rather than estimated.
- Dedicated supplies for kitchen equipment, compressors and refrigeration.
- Machine relocations, including isolation, disconnection and reconnection.
- Testing, certification and a schedule of what feeds what.
About Three-phase power and machinery
The supply question comes first
A machine arrives on a Tuesday needing a three phase supply the site does not have. That is the sequence that causes most of the cost and nearly all of the delay in commercial three phase work.
The useful order is the other way around: establish what the building can deliver, then decide what can be installed. We assess maximum demand against the actual equipment schedule rather than a rule of thumb, because that calculation decides both the cable size and whether the existing supply is adequate at all.
Why motors trip, run hot and fail early
Three common causes, and all three are measurable rather than matters of opinion.
- Voltage imbalance between phases, which makes a motor run hot and shortens its life considerably.
- Protection that is incorrectly rated, so it either nuisance trips or fails to protect.
- A starting arrangement that does not suit the load, so every start drags the supply down.
Measuring imbalance and starting current takes an hour and tells you which of the three you have. Replacing a motor without doing that usually means replacing it again.
Load balance is not a detail
On a three phase supply the load should be spread reasonably evenly across the phases. Sites that have grown by addition, with each new circuit landing wherever there was a spare way, frequently end up with one phase carrying most of the building.
The symptoms are voltage drop, equipment running hot on one part of the site, and protection tripping under load that should be well within capacity. Rebalancing is usually a day’s work and it is often cheaper than the supply upgrade somebody has quoted instead.
The distributor sets the timeframe
Supply upgrades involve your electricity distributor, who owns everything to the point of attachment. Approval typically runs one to three weeks and is outside our control. If plant is arriving on a date, the application needs lodging well before it.
We quote the job in front of us
No rate card, because the honest number depends on things nobody can see from a website. Estimates are free.
03 9889 3341Not urgent? Send the details and we will come back to you within one business day.
Standards this work is held to
Installed and tested to AS/NZS 3000, with maximum demand assessed against the equipment schedule rather than a rule of thumb. On a commercial site that calculation is what decides whether the existing supply is adequate, and getting it wrong in either direction is expensive: undersized means a second upgrade, oversized means paying for capacity you never use.
Supply upgrades involve your electricity distributor, who owns everything to the point of attachment. Their timeframes are outside our control and they are usually the long pole in the programme. If plant is arriving on a date, tell us early, because the distributor application is the part that cannot be compressed.
How long it takes
- Assessment
- A site visit, usually within the week.
- Distributor application
- One to three weeks typically, and outside our control.
- Machine connection
- Often a single day once the supply exists.
- Supply upgrade
- One to two days on site, scheduled around the distributor.
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Three-phase power and machinery questions we get asked
How do we know if we have enough capacity?
It has to be measured and calculated, not assumed. We assess maximum demand against your equipment schedule and tell you the answer in writing.
How long does a supply upgrade take?
The work is usually one to two days. The distributor approval ahead of it is typically one to three weeks and it is the part nobody can speed up. Start early.
Why do our motors keep tripping?
Common causes are voltage imbalance, undersized protection, or a starting arrangement that does not suit the load. All three are measurable, which is where we start.
Can you connect machinery we have bought ourselves?
Yes. Send us the nameplate details and the manufacturer's electrical requirements before delivery, not after.
Do you handle the distributor paperwork?
Yes, we lodge and manage it. We cannot make them faster, but you are not chasing it.
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Talk to an electrician now
Fastest way to get an answer is the phone. It is answered 24 hours a day, seven days.
03 9889 3341Not urgent? Send the details and we will come back to you within one business day.