Will single phase altered to 3 phase improve voltage drop

[SPECIAL LOCATION]

I doubt if I would be just using visual inspection to establish cable lengths...

:C

Surely it would be more appropriate to do a continuity measure such as R1+R2, or even R1+RN, (or both!) then use table 9A (pg 166 OSG) to calculate the circuit lengths...

Also I would NOT be relying on just measuring a voltage, (that can fluctuate anyway), to confirm any volt drops to base my costings on for any potential upgrade alterations work!

If you do a R1+R2 and an RN+R2 they should be within a gnats testicle of each other..

and R1+RN would be proportional to the 'R2' readings depending if different sized CPC used.

It could be that there is a concealed junction box somewhere with a high resistance joint causing some loss of voltage...

say a bad joint on Live or Neutral somewhere down the long run....

Don't forget that where the circuits exceed 100m the permissible voltdrop can be increased by 0.005% per meter up to a max 0.5%

(pg 358 Big Red).

And that the suppliers voltage can be anywhere between 216.2v - 253.0v

(pg 242 Big Red)

so just measuring it is of limited value?

Consider a scenario that you do a load of upgrade work then the customers moans that the lights a still dim!

and wants you to do more remedial work to rectify the problem at no extra cost.!

If I were doing this I would be have a fair few accurate calculations of the existing arrangement to base my recommendations on.

:coffee

 

[jus306]

Thanks Special Location for that I've taken that on board, just a thought Tower 2 are fairly new [4x1000w] installed by someone else, I am guessing they replaced 4 x 400w would that make any difference?

 

[ADS]

But Specs,

Surely if you treat each cable and tower as a 'radial' lighting circuit with the load on the end, then you can measure the voltage at the supply (cutout) and then measure the resulting voltage at the tower (lamps on, of course), to give you the voltdrop for that 'circuit'.

Now my argument is that if you switch the other towers on whilst taking the measurement at , say tower 1, then the volt drop will increase. This is why I proposed that if they were fed by different 'Lines' (or phases), then you would only have voltdrop attributable to that one particular tower and cable, as it's on its own 'phase', with nothing else contributing to the voltdrop - is this not correct?

 

[SPECIAL LOCATION]

Thanks Special Location for that I've taken that on board, just a thought Tower 2 are fairly new [4x1000w] installed by someone else, I am guessing they replaced 4 x 400w would that make any difference?

Do you have copies of the certificates for these "other contractors" recent work?

with their calculations & tests?

If their calculations & tests for that circuit confirm it is within all the permissible tolerance as per BS7671..

It don't matter how many lamps or what ratings they have put on there???

Remember You don't go upgrading all the wiring in a house just because you fit a cooker or a shower..

BUT:-

I think this sounds like a job that has been evolving and growing without checking all circuit characteristics when previous alterations have been made..

As said previously I would go back to a few basics and get some test readings on the individual tower circuits..

consider how many lights the customer would like to have fitted...

see if existing cables and distribution circuits are of sufficient capacity to supply the max demand..

4 x 400watt (1.6kw) is a bit of jump to stick 4 x 1000watt..

2.4kw increase (on 1 tower)

250% increase in load!

If do your calculations and they imply the supply is OK but just need larger circuit cables then OK..

But what else is running from the supply as well as the floodlights?

Any changing rooms, water heaters, showers..

space heaters..

etc..

etc..

Need the calcs before making any other decisions.

:|

 

[jus306]

No not alot more, db is adj the pitch, feeds socket & light in brick shed that houses the db, a couple of 500w floods that don't work, a socket in the groundsmans container, which I would say is very rare for tower lights to be on and groundsman to be there at the same time and a tennis hut, all they have is a kettle & a fridge, yet again not normally there when its dark. Next thing I will do is calculate the cable lengths & see where that takes me.

---------- Post Auto-Merged at 16:21 ---------- Previous post was made at 16:19 ----------

I'll check if there's any paperwork too

 

[SPECIAL LOCATION]

But Specs,Surely if you treat each cable and tower as a 'radial' lighting circuit with the load on the end, then you can measure the voltage at the supply (cutout) and then measure the resulting voltage at the tower (lamps on, of course), to give you the voltdrop for that 'circuit'.

Now my argument is that if you switch the other towers on whilst taking the measurement at , say tower 1, then the volt drop will increase. This is why I proposed that if they were fed by different 'Lines' (or phases), then you would only have voltdrop attributable to that one particular tower and cable, as it's on its own 'phase', with nothing else contributing to the voltdrop - is this not correct?

What if your meter is inaccurate to a tolerance of 1v

and the neighbors switch on something big while you are walking to the other end of the circuit to do your second reading?

a 2v error could easily put you over your voltdrop?

AFAIK the recognised method to establish volt drop is by calculation,

not measurement?

Also...

You are only looking at the volt drop along that particular length of cable...

No matter how many other circuits you switch on the actual voltage dropped down the single radial circuit is still only governed by the current going down that individual circuit...

i.e.

If 4.5volts is dropped down a cable is still only 4.5volts dropped down that cable if it starts at 240 and ends at 235.5 or starts at 230 and end at 225.5...

We have to ensure our individual final circuits do not drop more than the permitted percentage in relation to the voltage @ the origin?

Otherwise you will end up taking into account what you neighbors are switching off and on as well!

 

[Sidewinder]

The OP has said the voltage at the supply is 231 volts - then he gives the volt drops at each tower.Volt drop is dependant on load - so a four tower load will give the volt drop he has described - they are parallel loads - so that's four towers on one phase.

Volt drop from cut-out to each tower is about 14 volts.

If you split the towers off on to seperate phases, then obviosly you only have one tower(load) per phase - so the volt drop will definitely be lower - about 5 volts per phase.

Yes and no!

IMHO you are confirming in your post that the incoming supply is inadequate which is what I said. I think!

If the volt drop causing the issue is within the installation and is caused by the final radial circuit cables being inadequate then no matter what you have as the incoming mains you will still get excessive volt drop.

---------- Post Auto-Merged at 17:50 ---------- Previous post was made at 17:39 ----------

I have just read the rest of the posts.

Maybe the supply is inadequate, maybe it is not?

However as has been said you could have the volt drop within the final circuits which no matter what the incoming supply is at the install volt drop in the final circuits could be excessive.

As Specs says perhaps it is time to assess the complete installation and see what loads you have cable lengths, perhaps a TDR would be better for that job as measuring R1+R2 and R1+RN could be an issue because as has been suggested there could be joints which could be "poor"?

If you are going to have a 3ph supply provided, what size are you going to go for?

Would a summation supply be more appropriate?

This is not a 5 minute job really.

 

[james KEI]

so they've wired a circuit with a potential load of 32 amps (mcb / commando) up to a 160m in 4mm!!!!!!!!!!! keep the pitch warm

a quick V.D, not sure what lamps are fitted as to wether there's a factor to apply for startup

mV/A/m = 37 pg 280 table 4d4a colum 6 reference method D

tower 4 4x400W Ib = 7A length of run 160m 37x160x7/1000 = 41.4v VD

length of run 100m 37x100x7/1000 = 25.9v VD

tower 3 4x400W Ib = 7A 70 37x70x7/1000 = 18.1

125 37x125x7/1000 = 32.3

all calculations are known to be over the top compared to real life but it's were basic design should start and these above don't add up for 4mm to be sufficient

 

[Sidewinder]

They are probably discharge lighting so factor of 1.8 required, obviously depends on the spec.

 

[Manator]

The only cause for any unacceptable volt drop is cable size. The lighting towers were probably installed when 240v was the norm, now all calculations are based on 230v, just as Special Location says, the volt drop should be by calculation, simply reading any measured result is almost useless, due to fluctuations and the like. The percentage of volt drop calculated for 230v, will still be acceptable if the supply voltage variates between its allowable +/- % values.

Changing to 3ph, will only help with maximum loadings, and have very little effect on any volt drop issues.

 

[jus306]

Another question on these floods, the furthest flood light wired in 4 core swa is wired using 2 cores for live so live 2 X 4mm neutral 1 x 4mm , what are the issues with this??? I assume this was done to help voltage drop..

 

[Doc Hudson]

Are you saying the live conductor is 8mm (2x4mm) and the neutral conductor is still 4mm (1x4mm). As the current has to flow along both the live and the neutral I doubt this will achieve very much toward helping the volt drop. Parallel conductors can be used in circuits, there is a section in the regs on it, but both the live and neutral need to be the same CSA for single phase circuits.

Doc H.

 

[Zeespark]

Doc, would there be an issue with harmonics if doubled up as suggested?

AndyGuinness

 

[Manator]

I have seen two cores used for earth in order to lower the Zs, but never for any live core.

 

[Andy™]

I have seen two cores used for earth in order to lower the Zs, but never for any live core.

cant see a problem with it myself. it will half the VD in the line conductor for the distance its doubled up, and given the distance involved here, that could be a good few volt

it will also half the line conductor resistance, and lower Zs

thinking about it, by doubling earth you get a lower Zs. but by doubling line, your getting the same reduction in Zs, but also a lower volt drop. so even better result?

 

[Manator]

Good points Andy, but I do not like to imbalance the return through the neutral, I am a firm favourite of the what goes up must come down brigade.

 

[Andy™]

Good points Andy, but I do not like to imbalance the return through the neutral, I am a firm favourite of the what goes up must come down brigade.

yes, providing protection is adequate for smaller CSA of neutral. but i can see this method having some advantages in both VD & Zs, rather than larger earth giving only benefit in Zs

not something ive really though about much until now though

 

[Manator]

I often use a greater CPC to allow for low touch voltages on tender equipment, often piggy backing 16mm earth along with the armour and a central core, for longer runs. Now thats some seriously low resistance measurements, but thats what they ask for, and thats what they get. I have never used multiple cores for volt drop reasons though, I would be worried about parallel conductor issues.

 

[steptoe]

there must be something that prohibits you from having a larger line conductor than Neutral on single phase surely?

current is current, it doesnt care if its on a line or a neutral,

 

[SPECIAL LOCATION]

Another question on these floods, the furthest flood light wired in 4 core swa is wired using 2 cores for live so live 2 X 4mm neutral 1 x 4mm , what are the issues with this??? I assume this was done to help voltage drop..

headbangheadbang

I assume Bodgit & Scarper have been at it again........

Anyone read 524 Cross Sectional Areas Of Conductors in Cables?

Page 105 (for those who's index pages have fell out!!!!)

Especially 524.2:-

The neutral conductor, if any,shall have a cross sectional area not LESS THAN that of the line conductor;(i) in single phase, two-wire circuits, whatever the cross-sectional area.

(ii)....... blah blah blah

(iii)....... more blah blahs!!

Anyway..The bottom line as far as I have always understood it is....

Single phase circuits line CSA must equal neutral CSA

and vice versa!!!!!

After reading this additional gem I am more convinced of my earlier points...

Forget whats there at the moment..

Discuss the customers requirements

and redesigned and calculate what is needed...

we already know bigger CSA's are needed so why waste more time..

get the spec & do the calcs..

then find if you also need a bigger supply.

:| :Salute

---------- Post Auto-Merged at 01:36 ---------- Previous post was made at 01:33 ----------

there must be something that prohibits you from having a larger line conductor than Neutral on single phase surely?current is current, it doesnt care if its on a line or a neutral,

In the words of the churchill car insurance ad...

Oh YesYesYes!