My Utility Company Wants to Change my Supply from 230VAC

"Is there some piece of equipment (bearing in mind the size of the property) which I can instal which will convert a new 3 wire supply back to 230v 2 wires as it enters the property? I also live in UK so pointing me in the direction of a UK supplier would be helpful. Thank you."

You indicated you don't want to use transformers because of their burden power load doing nothing. but if you really want to leave everything the same, install a 1:1 isolation transformer of the required full load KW, feeding 220 on the primary, no power source neutral connection, then the secondary of this isolation xformer, ground one of the lines, this then will be a neutral, and the other line will be L keeping every thing the same, and connect this to your existing circuit breaker panel. Your backup gen set will stay connected on the secondary side of this isolation xformer as normal, with a power transfer switch to isolate back feeding of power,

You still will need your step downs for the 115 uses. Or you could have a separate circuit breaker panel from the new island power system. You do want to keep these two power systems separate. If you size this panel large enougn, you could add 230 double pole breakers as needed when you switch over to new water heaters.

I don't know what your wire color code is for this 230volt system. I'm going to assume neutral is white or gray as it does not matter if a 115 or 230 volt system. But the L1 and L2 must be a color black and red being the typical 14/3 or 12/3 wire (non metalic or UF) with ground and neutral.

I think I understand what you are wanting.

Lets go back to basics: The OP said The utility company has agreed to convert our neighborhood to the American 3 wire system ( which I understand is 110/120v L1, 110/120v L2 plus N) provided all the residents agree.

I'm not sure you understand the American system. There are really 4 wires. L1, L2, Ground and Neutral and we run at 60 Hz.

60 Hz equipment is likely to run on 50 Hz with some side effects, but systems designed for 50 Hz may not run on 60 Hz.

Simplifying.

What it looks like on the premise side is nothing more than a 240 V Center-tapped transformer. Ground and Neutral are connected at one point. The ground rod for the premise.

So, N and ground are at the same potential.

Between L1 and Neutral there is 120 V and between L2 and neutral there is 120 V.

Between L1 and L2, there is 240 V. Ground is protective and provides a reference and a place for fault currents to go.

The main breaker panel gets L1, L2, N and Ground. Neutral and Ground are connected together at this panel ONLY. Sub-panels keep the N and ground separated.

Breaker panels are known as "main Breaker" or "main lug". For this discussion a "main breaker" panel has a breaker that interrupts all the circuits in the panel. A "main lug" panel does not.

Since you mentioned generators, some panels can be purchased with an "a mechanical interlocked breaker". This allows "backfeeding" a panel through a breaker, but will not allow the main and the backfeed breaker to be on simultaneously.

The Neutral conductor carries the difference current between L1 and L2 and can change direction.

The panels are designed to accept 1 or 2 pole breakers. A 1 pole circuit is a 120 V circuit and a 2 Pole circuit is a 240 V circuit. The two pole breakers are mechanically interlocked. If one turns on, the other must. If one trips, the other must trip.

The 120 V Circuits consist of either (L1 or L2), Neutral and Ground. In the US they are wired with 14 AWG for a 15 A circuit and 12 AWG for a 20 Amp Circuit. The NEC requires stuff like 20 Amp circuits in Kitchens and GFCI's in certain locations. The wire is called things like 12/2 with ground. The ground conductor is uninsulated within the cable and is of a smaller gauge.

Our larger appliances and pumps are wired for 240 V. They can be 240 3-wire or 240 4-wire. Both schemes have L1, L2 and Ground. The Neutral is added in the 4-wire scheme.

That being said, an electric water heater or a large pump doesn't require a neutral.

Electric clothes dryers have problems all to themselves, but now 4-wire systems are required.

Now, many stoves etc are being made with electronic controls and to avoid using a 120 V controls transformer a Neutral is pulled.

Clothes washers and clothes dryers and window air conditioners typically use plugs. Water heaters, 240 V furnaces and central air conditioners use disconnects nearby.

The one thing we NEVER do is fuse the neutral. So watch British stuff.

120 VAC is common for controls in the home. 24 VAC for low voltage control wiring such as the central air conditioner.

Rewiring is bound to inconvienience somebody.

For the utility, it could just mean rewiring the transformers, a few locations at a time. At home, 4 homes are on one transformer. For the homeowner, he has to change the distribution main panel and who knows what else.

I'd suspect, that your set-up will mostly work as is except for the main panel and the transformer connections and neutral to the house. Your generator might cause a glitch in how that's wired. i.e. the output transformer there may have to be changed.

Once you have the 240 system in place, most stuff would likely work. Your 120 step-down stuff might likely work too. You would then remove your 120 step-down stuff as needed.

You would end up with a 240 system that was wired differently allowing the homeowners to run 120 V circuits as needed. They would likely have to be new because of the wire gauge problem.

Your "upgrade" becomes a stepping-stone, so to speak. I doubt that you would be able to convert the existing 2xx outlets to 120 V and to eliminate the 2xx/120 V transformers new wiring would have to be run, but it's not an IMMEDIATE problem.

Ignore option (B).

Silverthorn describes a three-phase wye-connected distribution system, common in industrial installations. My plant uses such a system to provide 120 VAC from any of the three phases to the neutral and 208 VAC between any two of the three phases. I seriously doubt your utility is going to replace a 220/240 VAC 2-wire distribution system with a 4-wire 3-phase distribution system, especially in a non-industrial setting.

Option (A) does NOT require a fourth wire.

A 3-wire (L1-N-L2) distribution uses only three wires, one neutral and two "hot". The distribution at the street normally will "ground" the neutral there, along with the transformer ("pole pig") case, and the center tap on the low-voltage 220 VAC secondary. The "pole pig" transformer typically accepts high voltage, single phase, 2-wire and transforms it down to single phase 220/240 VAC 3-wire through a center-tapped secondary winding. The center tap is the neutral or N and is connected to earth ground, typically with a heavy gauge uninsulated solid copper wire stapled to the pole and connecting between a driven copper-clad steel rod, the transformer case and the secondary center-tap.

At the service-entrance distribution panel, the neutral is bonded (permanent electrical connection) to the "safety ground" SG in the panel and to another earth ground, typically a buried metal cold water pipe or another driven rod. From this point on to the user load there are either three or four wires: L1 and L2, N, SG for 220/240 VAC loads; L1 or L2, N, SG for 110/120 VAC loads. Most 220/240 VAC appliances do not need the N wire, but most do require the safety ground (SG) to be attached to the appliance metal frame. This type of load (typically a water heater or a motor) only needs three wires: L1, L2, SG. Most 110/120 VAC loads also only need three wires: L1 or L2, N, SG.

The line drops from the utility pole to the service entrance are typically in air and the wire is oversized somewhat to be sustainable against ice loading (not in your location of course!), wind loading, and weight. Only the two "hot" lines are insulated and they are usually loosely wrapped around the uninsulated neutral which actually supports most of the weight. Because the wires are in open free air, they are capable of much higher current (and resistive heat dissipation) than the same gauge wires installed in a wall or conduit. This means you probably would only have to run ONE additional wire to the street, along side your existing 2-wire feed. Even though the two "hot" wires in a 3-wire service drop will carry twice the current as the same load in a 2-wire drop, the original outside 2-wire installation should easily accommodate this extra current so that you only need to add one wire to obtain your 3-wire drop.

Hop

You must be very confused by now, considering all the "advice" posted. In my not so humble opinion, ignator gave the best and only advice you should follow for now: install a 1:1 isolation transformer between the 3-wire (L1-N-L2) feed from the utility and your existing 2-wire (L1-N) feed to your property. The secondary of the isolation transformer replaces the existing 2-wire utility feed. For reasons I will explain later, the secondary should be center-tapped.

Size the isolation transformer to handle the full load expected, say, 16 KVA if your backup generator fully replaces the power normally delivered by the utility service, larger if it does not. Fuse the L1 and L2 feeds from the utility to the primary of the 1:1 isolation transformer accordingly. Do not fuse the N wire. Connect the N wire from the utility feed to the N wire of your existing 2-wire feed and to a local grounding rod at the service entrance.

You may be able to find a suitable convection air-cooled transformer on the used equipment market… try E-Bay or other on-line market places. The efficiency will not be as great as a complete re-wire of your property would provide, but the cost will be significantly lower. If you later desire to "improve" the property, the changes to a 3-wire distribution can be made gradually over a period of several years on an "as needed" basis. It is absolutely imperative that you hire a qualified electrician to oversee these changes.

If you do "bite the bullet" and decide to make a full changeover to 3-wire, the same 1:1 isolation transformer can be re-purposed to connect the backup generator to the property feed in place of the utility feed, provided the isolation transformer secondary winding has a center-tap for the neutral connection. Plan accordingly when you initally purchase the isolation transformer.

You will need to install a double-pole double-throw break-before-make changeover switch that will disconnect the 3-wire utility feed and then connect the 3-wire backup generator feed coming from the center-tapped secondary of the isolation transformer. You probably already have a single-pole double-throw switch in place now that disconnects the utility 2-wire feed and replaces it with the generator 2-wire feed. However. in this case (complete changeover to 3-wire property wiring), the generator connects only to the isolation transformer, through an appropriately sized fuse or circuit breaker, instead of directly to the property wiring. You need to install a double-pole double-throw changeover switch in the isolation transformer's center-tapped secondary because you are now switching two "hot" wires (L1 and L2).

All that is much further down the road. Just remember to buy a 1:1 isolation transformer with a center-tapped secondary. Quite often such a transformer will have two primary and two secondary windings, each winding rated for 120 VAC. That makes it easy. Just connect the two primary windings in series and connect the two secondary windings in series. The connection between the two secondary windings serves as the center-tap. The connection between the two primary windings serves as an unused center-tap of the primary.

Hop