How to wire a house using 3 phase

[shaemus]

On 8/24/2017 at 11:52 AM, Crossy said:

Number one task = Planning.

 

• What loads do you expect in each building? (big man-cave with machine tools - see what sometimewoodworker has installed)
• Does a building need 3-phase? (like big water pumps).
• Do need voltage stabilisers? (how far out in the sticks are you)
• Will you be installing a genset? (how far out in the sticks are you)
• Any plans for solar?

 

These things are easier to build in at the start rather than hack the system about later (I have this t-shirt).

 

Then design your system (we can help here, just ask).

 

Then tell your sparks what to do.

 

 

Good Advice here from Mr Crossy.

 

Plan for now, and plan for the future. 

• Do you need 3 phase in each building? or will single phase suffice
• Do you want to run all your sub mains UG to each building?
• What is your budget?
• are you out houses complex installs?
• Do a serious voltage drop calculation, very important if you want any future solar install to work properly (voltage rise)
• Ideally your sub main cable is suitable for UG. install. XLPE single core maybe 25mm or bigger, do the calcs or pay someone to complete this 

Fundamentally 3 phase into a Distribution panel, then either 3 phase or single  to each building and run an earth to each building, Small Consumer unit with a MCB as the main switch (submain protection) in each dwelling, Consider split load Consumer units, protected and unprotected circuits. or just use a combination of MCB's and RCBO' in each consumer unit. Id try any see if you can get the PEA to some some service fuses inline before their metering equipment and add some surge arrestors/lightning protection into the design

 

Have your fancy kit, at the distribution point. You can put solar on the outbuildings, but id be putting all your generators, changeover switches, voltage regulators,  in your switch room. Some of the more fancy solar hybrid sytems use contactors and relays to supply your emergency circuits from the battery set up. But thats expensive.

 

 

 

Use the Kiss philosophy. Keep it Simple 

[oldwelshman]

On ‎28‎/‎08‎/‎2017 at 1:48 PM, DGS1244 said:

Are you talking about a Thai 3 phase or a European 3 Phase. I have a Thai 3 phase which is three separate 220v supplies coming from the street to the distribution panel. A European system is 360 volt total and would very careful wiring. I have seen fires started by someone connecting two floors of a building, which were on separate phases, resulting in serious risk to persons from electric shock apart from the fire situation.

I am pretty sure many houses in UK have 3ph supply and different phases around the house. Why would this increase the risk of electric shock if installed correctly? What caused the firs as I assumed the consumer board would have each phase protected?

[Crossy]

5 hours ago, oldwelshman said:

I am pretty sure many houses in UK have 3ph supply and different phases around the house. Why would this increase the risk of electric shock if installed correctly? What caused the firs as I assumed the consumer board would have each phase protected?

3-phase does not increase the risk of shock (it's still 220V to ground), UK regs no longer need "Danger 400V" notifications on 3-phase boards.

 

For domestic with no actual 3-phase appliances it's best to wire as if it's 3 separate single-phase installations and spread your stuff across the phases, gives reasonable balance and ensures that you have at least some lights, A/C etc when one phase goes out.

 

[oldwelshman]

17 hours ago, Crossy said:

3-phase does not increase the risk of shock (it's still 220V to ground), UK regs no longer need "Danger 400V" notifications on 3-phase boards.

 

For domestic with no actual 3-phase appliances it's best to wire as if it's 3 separate single-phase installations and spread your stuff across the phases, gives reasonable balance and ensures that you have at least some lights, A/C etc when one phase goes out.

 

I was trying to work out what caused the fire and why its higher risk?

the house I live in currently I added a second CU and earthed everything. Building house in a year or so and also doing a bore hole so I guess that will have a 3ph pump, not sure abput swimming pool etc but will read up on those, also using a pump to irrigate land so I will go for 3ph supply then wont have issue if pumps 3ph and as you say will split circuits between phases.

 

[Crossy]

7 hours ago, oldwelshman said:

I was trying to work out what caused the fire and why its higher risk?

Three-phase supplies tend to be larger in capacity and phase-phase events are more energetic than phase-neutral (1.7 times the voltage = about 3 times the energy). But, generally, anything that will start a fire on a 3-phase supply has an equally good chance of starting one on single-phase.

 

There is a general conception that 3-phase is somehow more dangerous. It isn't when done correctly, but it doesn't hurt to give all electricity the respect it deserves, something which seems sadly lacking in Thailand.

 

I would minimise the number of 3-phase appliances you use. Motors over a couple of horses probably (but will need phase-loss protection) and big water heaters (>10kW) ok, everything else stick to single-phase.

 

[mogandave]

“...phase-phase event...”

I love that...

[oldwelshman]

16 hours ago, Crossy said:

Three-phase supplies tend to be larger in capacity and phase-phase events are more energetic than phase-neutral (1.7 times the voltage = about 3 times the energy). But, generally, anything that will start a fire on a 3-phase supply has an equally good chance of starting one on single-phase.

 

There is a general conception that 3-phase is somehow more dangerous. It isn't when done correctly, but it doesn't hurt to give all electricity the respect it deserves, something which seems sadly lacking in Thailand.

 

I would minimise the number of 3-phase appliances you use. Motors over a couple of horses probably (but will need phase-loss protection) and big water heaters (>10kW) ok, everything else stick to single-phase.

 

No intention of large water heaters, only water pump that's it. Only shock hazard is if someone has extremely long arms and somehow reaches bare conductors between floors to get to 415v lol. I once saw engineer stick his hand inside an electronics cabinet (x-ray generator) and got his hands between phases on a 3ph contactor, burnt his hands, horrid smell, and to get away from it he put other had on cabinet to pull away, no idea how he survived that one but he looked rough as hell and lots of little burns on his hands and they smelled like burning pork lol