Threshold for 3-phase supply

[JohnW2]

.... But if the DNO have a single phase supply, that's what will be offered, if they have a three-phase supply that will be offered.

Is not "what the DNO have" virtually always 3-phase (very occasionally 'split phase')? To provide single phase supplies for customers,they just use one of the 3-phases for each customer.

It may be just down to lack of experience, but I've never heard of a DNO transformer which transforms distributed 3-phase 11kV (or whatever) to single-phase 230V, have you?

 

[ericmark]

It may be just down to lack of experience, but I've never heard of a DNO transformer which transforms distributed 3-phase 11kV (or whatever) to single-phase 230V, have you?

No, all the single phase supplies I have seen have been 460 volts centre tapped. But not been to that many farms etc, which could have run with a single 230 volts supply.

 

[plugwash]

It may be just down to lack of experience, but I've never heard of a DNO transformer which transforms distributed 3-phase 11kV (or whatever) to single-phase 230V, have you?

In rural areas it's not uncommon to see 11kV overhead lines with only two wires, so they can't feed a 3-phase transformer.

Whether the transformer outputs are split-phase or single ended I don't know, I suspect it varies with the power capacity.

 

[JohnW2]

In rural areas it's not uncommon to see 11kV overhead lines with only two wires, so they can't feed a 3-phase transformer.

Interesting. In the rural area where I live, the 11kV (if that's what it is) overhead supply to my village seems to have three 'wires' (which makes sense, given that I have a 3-phase supply ). However, it's not something I generally pay much attention to, so it's quite possible that a lot of other rural ones are as you describe.

 

[SUNRAY]

Is not "what the DNO have" virtually always 3-phase (very occasionally 'split phase')? To provide single phase supplies for customers,they just use one of the 3-phases for each customer.

It may be just down to lack of experience, but I've never heard of a DNO transformer which transforms distributed 3-phase 11kV (or whatever) to single-phase 230V, have you?

Well a lot depends on developement, it may be that a new developement is planned so it may seem a new 11KV 3ph line is put in to supply one property, and then the developement may not go ahead

In rural areas it's not uncommon to see 11kV overhead lines with only two wires, so they can't feed a 3-phase transformer.

Whether the transformer outputs are split-phase or single ended I don't know, I suspect it varies with the power capacity.

11KV single phase is very common, I can think of 3 such situations within a few minutes drive and each feed a few properties. Whether its 1 or 2ph I know not.
.

 

[flameport]

upgrading the electrics to suit multiple electric showers,

Don't even bother looking at that option.

upgrading the gas hot water to supply 6 (or more) mixer showers.

If gas already exists then use that. Multiple hot water cylinders from one or more gas boilers.
You can also fit electric immersion heaters to them as a backup, or to use with solar panels.

 

[SUNRAY]

Well a lot depends on developement, it may be that a new developement is planned so it may seem a new 11KV 3ph line is put in to supply one property, and then the developement may not go ahead

The other position is a long feed across the fields to a small cluster of properties and a development happens requiring a much larger supply may be fed from the opposite direction, significantly reducing the usage on the original supply

11KV single phase is very common, I can think of 3 such situations within a few minutes drive and each feed a few properties. Whether the LV is 1 or 2ph I know not.
.

 

[Jurassicspark]

Probably, yes, particularly in a single-family residential property. Other situations are probably different - e.g. in a hotel, or even HMOs etc, multiple people showering simultaneously would not be uncommon.

Why would there be a higher chance of multiple people showering when a HMO is concerned, but for a 12 bed guesthouse this isn't the case?

Not sure if this is the crux of your point but, while it’s often argued that HMO tenants follow similar routines, this doesn’t automatically mean simultaneous usage is more predictable. Or even if it is then, doesn’t a 12 bed guesthouse still risk concentrated peak usage, such as the mornings when most guests shower before leaving?

 

[securespark]

Can't you use those mega flow unvented cylinders?

 

[JohnW2]

Why would there be a higher chance of multiple people showering when a HMO is concerned, but for a 12 bed guesthouse this isn't the case?

I wasn't suggesting that there was. In both cases there are 'multiple people'involved, and I was contrasting that situation with a "single-family residential property' (which would usually amount to a lot less than 12 people )

Not sure if this is the crux of your point ...

It wasn't - see above and below!

Looking back, I think I can see why I confused you, with my "Probably yes..." start to the sentence - which probably wasn't clear enough. What I was trying/intending to say is that the application of some degree of diversity would probably be possible, particularly in a 'single-family residential property' but that "it" (the extent/degree of allowable diversity) might be different in a hotel or HMO (or guest house). Sorry if I confused you (and maybe others)!

 

[ericmark]

You can also fit electric immersion heaters to them as a backup, or to use with solar panels.

I would say and rather than or, as North Wales I know direct water heating solar panels are useless, works well in Turkey, but not in the North of the UK, using PV solar and a unit to redirect excess solar to water works, I will not say works well, as at least I get 15p/kWh for exported solar and pay 8.5p/kWh for off-peak power, so a simple time switch gives cheaper DHW to the units which detect export like the iboost+.

The direct unit my father-in-law had fitted never worked other than to remove the chill, and give him a better energy rating, as it seems they don't need to work to give one a better energy rating.

Why they are includes as a separate item on the energy rating, I do not know? As there is no point having water and PV panels, as the latter will do both.