What are your thoughts on this 3ph domestic.

[charlie76]

The installation on the attached pic is a property with a 3-phase supply and a range of fuse boards. I am currently in training but this is a family friend and I have discussed carrying out a rewire for them once I get my papers. I intend notifying the works to BC and then getting NAPIT in to use it as an inspection site to get my competent persons sign of.

My query with this is, I was of the understanding with a 3ph supply, the consumer was obliged to balance their load amongst the 3 phases. This has recently had new fuses fitted by the DNO and as can be seen they have quite happily only connected one of the phases. If I carry out a rewire, should I design the system to utilise all three phases and leave 3 tails for connection by the DNO when complete or is this unnecessary in a domestic system due to the minimal load?

 

[sajeel]

Davesparks I don't know why your cage is rattled there is nothing wrong with my comment based on the fact a 3 phase solution is required but a load calc will show that as stated in my post.

 

[davesparks]

Davesparks I don't know why your cage is rattled there is nothing wrong with my comment based on the fact a 3 phase solution is required but a load calc will show that as stated in my post so I suggest before opening your mouth THINK

A single phase supply has been provided by the DNO at the point of connection to the consumers equipment.
It is a domestic installation so normal load is going to be around 20A.
It'll cost a fair whack to have a three phase supply made available which will be completely unnecessary.

And as for fitting a ryefield board? What would that achieve unless there are a lot if submains to be run?

 

[charlie76]

Guys, lets not argue. I believe my question has been answered. It is a 3 phase head, this is confirmed by the DNO. It is a single phase supply as Dave says the supply is the side of the meter available to the consumer, so in my case I ignore the fact it is a 3ph head, the relevance is the single phase at the meter tails.

For future reference for me Dave, my question would have been relevant I guess if a 3 phase meter had been installed and all phases made available to the consumer? Then, would I need to consider load balancing. If for instance this was still only a domestic supply loading approx 100A would you be expected by the DNO to utilise all 3 phases and split the loads evenly amongst them?

 

[charlie76]

That's ok, it's only been said a half dozen times already in this thread.

Now, more importantly, did they say you could connect to the earth terminal in that cutout?

Dave, this is the existing earthing arrangement:

 

[davesparks]

For future reference for me Dave, my question would have been relevant I guess if a 3 phase meter had been installed and all phases made available to the consumer? Then, would I need to consider load balancing. If for instance this was still only a domestic supply loading approx 100A would you be expected by the DNO to utilise all 3 phases and split the loads evenly amongst them?

If you had a three phase supply, and actually needed it, then he's you should look at balancing the loads across the phases. But very few loads in domestic are constant so in effect it will be almost impossible to actually balance it.
Up until a few years ago the regulations required points on different phases to be kept seperate from each other or clearly labelled as 415V being present. This is why a lot of houses fed with 3 phases are wired with each phase feeding a different floor. So ground floor L1. First floor L2, second floor L3.
This doesn't balance the phases very well but does achieve reasonable separation of the points.

If look at the effect on the customers bill of getting the meter changed to single phase first off if They had a 3 phase supply that was unnecessary, it may reduce their bill to have the smaller supply.
If a domestic install really has a normal/average load of around 100A then it will likely be an enormous house and already be utilising a three phase supply

 

[sajeel]

Very true unless extension, basements and lofts have been added with electric showers or electric hob and ovens then load can exceed 100a easily I had one property that was tripping due to overload when I explained he required three phase head he was like I don't wanna spend that kind of money. I just won't switch on that many appliance s. I told him I will wait to hear from should you wish to upgrade as one phase has reached its load limit.

 

[davesparks]

Very true unless extension, basements and lofts have been added with electric showers or electric hob and ovens then load can exceed 100a easily I had one property that was tripping due to overload when I explained he required three phase head he was like I don't wanna spend that kind of money. I just won't switch on that many appliance s. I told him I will wait to hear from should you wish to upgrade as one phase has reached its load limit.

What was tripping?
Did you carry out a load study to ascertain exactly what was going on, or how did you assess the magnitude and cause of the overload?

 

[sajeel]

What was tripping?
Did you carry out a load study to ascertain exactly what was going on, or how did you assess the magnitude and cause of the overload?

Yes I did go found issue to be extra electric shower added to extension they already had one electric shower. All appliances were fine and tested.

 

[Andy78]

Yes I did go found issue to be extra electric shower added to extension they already had one electric shower. All appliances were fine and tested.

Which device was operating as a result of this overload that you identified ?

 

[davesparks]

Yes I did go found issue to be extra electric shower added to extension they already had one electric shower. All appliances were fine and tested.

I didn't ask if you went there, I asked if you actually carried out some sort of load study. Ie did you connect current recording equipment to the installation to record the actual load?

 

[GMES]

Please keep the thread civil or it will be closed.
@ Charlie if you have an issue with any comments aimed at you then feel free to use the report button that's why it's there, but to be fair you have said you are still in training which is why some members are cautious with their advice.
@sajeel by all means participate in the thread but leave the moderating to the moderators.

 

[sajeel]

I didn't ask if you went there, I asked if you actually carried out some sort of load study. Ie did you connect current recording equipment to the installation to record the actual load?

No because I wasn't being paid to carry out a test I was there with my plumber when he asked me if he could convert single phase to 3 phase.

 

[davesparks]

So you don't know any details of the overload, or even if it was actually an overload or another fault in the shower?

What was tripping on overload? You don't normally see a main circuit breaker on domestic

 

[sajeel]

As I said I spoke to potential customer who had a very large house with 2 showers 2 ovens and 2 hobs he was complaining of tripping on occasions when a lot of equipment is used simultaneously a quick walk around and rough calculation gave me the conclusion that even with diversity included if many appliances are used he will exceed the 100a rating of incoming supply head and that a further survey would need to be carried out and a upgrade to dno for 3 phase would be required if you are exceeding the 100a load

 

[7029 dave]

My first thought was single phase supply conversion, to three phase, but looking at that photo TNS lead supply no just replaced the 3 phase cut out. (me thinks, how do you know all phases are live)?