Electric supply single vs three phase

[WWilts]

Applied to SSE for new electric supply, new build.

Single phase goes past the front of the property.

Three phase requires digging up the public footway for a distance of about 45 metres.

Is there any good reason to get three phase instead of single phase supply?

 

[A_L]

16 minutes ago, WWilts said:

Is there any good reason to get three phase instead of single phase supply?

 

Depends on your situation. Makes connecting 3.68-11.04kW of PV without complications. DNO's do not want heat pumps with an output typically more than 14kW to single phase supplies.

[WWilts]

No heat pumps, only reason for considering 3 phase was electric vehicle charger (in future)
Pumping chamber for foul drainage uses only 0.37kW

Edited May 6, 2021 by WWilts

[WWilts]

4 minutes ago, A_L said:

3.68-11.04kW of PV

Not familiar with abbreviation PV, my bad

[A_L]

1 minute ago, WWilts said:

Not familiar with abbreviation PV, my bad

 

PV = Photovoltaics = Solar panels (Electricity producing) ?

[Thorfun]

have you had quotes for both? might be a simple decision once you have those to compare.

 

for us, it was about £20 difference so 3-phase was an easy choice.

Edited May 6, 2021 by Thorfun

[Wagas]

44 minutes ago, Thorfun said:

have you had quotes for both? might be a simple decision once you have those to compare.

 

for us, it was about £20 difference so 3-phase was an easy choice.

 

So jealous! UKPower want an extra £8k for 3 phase as they have to upgrade a transformer

[WWilts]

1 hour ago, Wagas said:

UKPower want an extra £8k for 3 phase

What advantage do you gain from 3 phase please?

 

If I may ask, to understand the pros and cons better.

[Pocster]

3 hours ago, Wagas said:

 

So jealous! UKPower want an extra £8k for 3 phase as they have to upgrade a transformer

I briefly looked at 3 phase . Saw the ‘estimated’ cost and thought f that . So single phase with PV and EV - it’s all good ? 

[Wagas]

2 hours ago, WWilts said:

What advantage do you gain from 3 phase please?

 

If I may ask, to understand the pros and cons better.

I haven't really looked into it, my solar guy just said if you can get 3 phase you should. I guess you're possibly restricted with single phase if you want to consume a lot of power all at once eg car charger, heat pump etc. 

 

I don't think there are any cons other than cost.

[pdf27]

3 hours ago, WWilts said:

What advantage do you gain from 3 phase please?

 

If I may ask, to understand the pros and cons better.

Pros:

• 3x the electrical power in and out of a single phase system. That's handy for things like faster car chargers, big PV arrays, etc.
• Some things - basically big motors - need 3-phase to work. If you're planning a big workshop that may help as the bigger tools may need it.

 

Cons

• Installation cost may be bigger - depends on your circumstances.
• Smart meters are harder to get for it at present.

Not worth spending £££££ to get, but in most cases the difference in cost should basically be down to 4 cores rather than 2 in the cable they lay, which is pretty trivial.

[saveasteading]

For years I asked sparkies what was the principle of 3 phase, and they didn't know. 

This is what I think I now know.

 

3 phase is necessary for heavy industry. The 3 power supplies are out of phase with each other (peaks and troughs are 1/3 apart) (like pistons in a car, don't all push at once) ) so that the power is smoother as well as more powerful at 440V.

Machinery also lasts longer, because of the 'smoothness'.

But you can take power off each supply at 230V.

 

I have no idea if fast car battery charging needs 3 phase, but iIdoubt it.

 

So unless you need to operate heavy machinery, then it doesn't need to be 3 phase, and you can have a bigger, single phase supply instead.

 

All gurus:    If any of that is wrong, then please do tell.

[newhome]

10 minutes ago, saveasteading said:

So unless you need to operate heavy machinery, then it doesn't need to be 3 phase, and you can have a bigger, single phase supply instead.

My 24kw boiler requires three phase so it’s not just machinery. I think at least one supplier (Western Power) is moving to 3 phase for new connections where possible. 
 

 

[Bramco]

An M+E consultant can do an analysis of what you intend to connect to see if 3 phase is necessary. Can't remember for the life of me what they call these - someone will be along before long who does know - but our M+E chappie said we would be fine with a normal single phase supply - 7kW ASHP, 4kW solar PV and standard EV chargers with all the normal ovens, lights, small appliances etc.

 

As @newhome said though big ASHPs need 3 phase - you can see HP requirements if you look up their specs.

 

Simon

[shuff27]

As noted above - I've just had my connection quote from Western Power & it specifies 3-phase.  They know I'll be having an ASHP (but no detail as to size); they may also know that my local council mandates installing cabling for an EV charger in all planning permissions.

 

I'm going back to them to ask if single phase is still an option & if so what is the cost difference.

[saveasteading]

'3 phase boiler.' from a quick search it seems that for over 15kW, electric boilers need 3 phase.

Makes sense, as 220V x 100A is only 22kW.

 

[saveasteading]

Can you get 2 or more 100Amp  feeds and split the functions? 

[Bramco]

8 minutes ago, shuff27 said:

my local council mandates installing cabling for an EV charger in all planning permissions

 

Our permission stipulated 2!

 

Simon

[shuff27]

2 minutes ago, Bramco said:

 

Our permission stipulated 2!

 

Simon

You must live somewhere posh - in this area we can only afford one car ?

[Pocster]

1 hour ago, saveasteading said:

have no idea if fast car battery charging needs 3 phase, but iIdoubt it.

I *think* it does as max on single phase is 7kw . Someone May correct me ???

[Bramco]

31 minutes ago, shuff27 said:

You must live somewhere posh - in this area we can only afford one car ?

 

The borough might be but the village aint!

 

Simon

[andy]

12 minutes ago, pocster said:

I *think* it does as max on single phase is 7kw . Someone May correct me ???

 

For Tesla Model 3, look here:

https://ev-database.uk/car/1321/Tesla-Model-3-Long-Range-Dual-Motor#charge-table

You go from 7.4kW to 11kW, so 25 to 38mph.

 

For Tesla Model S Plaid:

https://ev-database.uk/car/1406/Tesla-Model-S-Plaidplus#charge-table

You go from 7.4kW to 22kW, so 22 to 50mph.

 

So for me, future proofing home charging and having PV and an ASHP plus no price uplift meant 3 phase the way to go.  I even have a smart meter but that was a battle and a half to get...

[Pocster]

3 minutes ago, andy said:

 

For Tesla Model 3, look here:

https://ev-database.uk/car/1321/Tesla-Model-3-Long-Range-Dual-Motor#charge-table

You go from 7.4kW to 11kW, so 25 to 38mph.

 

For Tesla Model S Plaid:

https://ev-database.uk/car/1406/Tesla-Model-S-Plaidplus#charge-table

You go from 7.4kW to 22kW, so 22 to 50mph.

 

So for me, future proofing home charging and having PV and an ASHP plus no price uplift meant 3 phase the way to go.  I even have a smart meter but that was a battle and a half to get...

Yep - 3 phase best for “ future proofing “ .

Though I can only charge at 7kw it’s not an issue . I “ top up “ frequently; especially when PV output is high . Indeed my EV battery has never been below 50% .

Sometimes I adjust so I only charge from PV - which of course may just be 1kw . But it’s free fuel ! 

[joth]

1 hour ago, pdf27 said:

Pros:

• 3x the electrical power in and out of a single phase system. That's handy for things like faster car chargers, big PV arrays, etc.
• Some things - basically big motors - need 3-phase to work. If you're planning a big workshop that may help as the bigger tools may need it.
• Future proofing / flexibility. energy is increasingly electrified, and it is hard to predict what your future needs maybe. [aircon? annex  / second house on plot? workshop? elevator? pool? etc etc]

 

Cons

• Installation cost may be bigger - depends on your circumstances.
• Smart meters are harder to get for it at present.

Not worth spending £££££ to get, but in most cases the difference in cost should basically be down to 4 cores rather than 2 in the cable they lay, which is pretty trivial.

 

Added a third pro of future proofing, as it's worth calling out a house will hopefully last several generations, it's hard to know what will be needed in future, but if it's only £20 to prepare for it, why the heck not

 

it's worth calling out: you can get a 3 phase supply and only connect up one phase of it to a single-phase meter, and just leave the other 2 there spare in case of future needs.

[Wagas]

27 minutes ago, andy said:

 

For Tesla Model 3, look here:

https://ev-database.uk/car/1321/Tesla-Model-3-Long-Range-Dual-Motor#charge-table

You go from 7.4kW to 11kW, so 25 to 38mph.

 

For Tesla Model S Plaid:

https://ev-database.uk/car/1406/Tesla-Model-S-Plaidplus#charge-table

You go from 7.4kW to 22kW, so 22 to 50mph.

 

So for me, future proofing home charging and having PV and an ASHP plus no price uplift meant 3 phase the way to go.  I even have a smart meter but that was a battle and a half to get...

 

I have the same view on future proofing but not sure it's worth paying £8k. I've already paid £5k to UK Power to get power to the plot. Estimated house value will be £750k so it's not a huge %. Still not sure