10-15v drop in power from house to studio!

[Nowak]

Hi,

I've been checking my power recently due to issues with my console and yesterday measured points around my site. My house points are reading 244v yet the studio was down to 231v!.

My sparking installed the power to my studio years ago from the mains box to a sub box in the studio but I'm wondering if I need to install a heavier/thicker cable as it's a run of about 20 odd metres from the mains box to the sub box.

Any ideas?

Stef

[DarkSky]

Hi Stef. A 13 volt drop is way more than you should expect over a 20 metre run, regardless of the cable. It might pay to get Mr Sparks back on site to take a closer look.

[Nowak]

It got hot again yesterday afternoon, so I started taking readings, that's why I questioned the cable, perhaps there's too much resistance building up on the hot days which is also causing inconsistency and fluctuations.

I checked levels this morning, it's a lot cooler here, studio points are reading 248v, same as the house.

Fascinating!!

Stef

[Ben M]

Fascinating indeed Stef. Hmmm.......

[stosostu]

Wire resistance should reduce with increased temperature, so I doubt that the heat is the cause. More likely a bad connection somewhere. I had a similar problem with the house wiring which we discovered when the sparky was wiring the studio. On the ETSA side of the meter the screws had not been tightened and the wire had become corroded and the insulation hard and brittle due to sparking over the years. Fortunately there was enough spare wire to fix it properly.

[DarkSky]

I checked levels this morning, it's a lot cooler here, studio points are reading 248v, same as the house.

My guess is that it's varying depending on the load on the studio circuit.

Do you have anything (eg HVAC) that is kicking in when it's warm that could be drawing enough load to lower the mains supply, but that uses less power when it's cooler (like this morning)... ?!

[Nowak]

The A/C is always on in the studio when the console is up, obviously will work harder when the heat's on.

My sparky came in today, seems that one of the phases (that the board was powering off) was a little weak, so he switched the phases around and put the consoles point on the strongest phase.

We'll see how things go next hot day, it's been brought to my attention a few times that it could indeed be the PSU that's toublesome and its smoothing caps.

I'll check voltages on Monday when the world is working again, there was always a drop in the afternoon so I'll check again.

Stef

[Futureman]

Wire resistance should reduce with increased temperature, .

I'm not so sure about that.

Coppers resistance/temp Coeffecient is +0.393 percent per degree C.

But I'd doubt that would explain the voltage drop.

[rob]

indeed resistance of wire increases with increasing temperature, but the difference in resistance on a 20 deg over a 40deg day is bugger all.
voltage drop on a cable is totally dependent on load, so nothing on in the studio will cause no drop. Never the less any load within reason should only cause a small drop.
As you have now discovered the studio is running on a different phase to the house and the voltages on any of the three available phases can vary from each other.
Interestingly our house and the workshop run off one phase and the aircon and stove run off another. We have had three power failures over the last year, one lasting 30 hours. In every case we have lost the phase that the house / workshop runs off but the phase with aircon / stove has held up.
So we can't work, watch TV, read books but we can keep cool and bake pies.

[mylesgm]

So we can't work, watch TV, read books but we can keep cool and bake pies.

When this is what happens when you lose power...bring on the black outs I say!