uksparks
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Hi,
I have just started a new build today, its a large U shaped bungalow with vaulted ceilings etc.
I have split the property down into a lot of circuits to help with things due to cable runs etc.
I have just wired a section of it today, I was going to do it all in 4mm radials, but by the time I had got to the end of the section (bedroom, Wardrobe, Study & Entrance Hall) I had used 96 meters, this does not include the leg back to the board which is a further 13 meters....
I had given it though on paper, but then when I started cable routes were not quite so straight forward etc.
Anyway, my problem I have now is that the R1+R2 for that circuit at say 110 meters, will be 1.83 Ohms, which is way too much as was going to put it on a 32A, jees I would have to drop it to a 16A to comply.
So then thought, its ok, illt turn it into a ring, total length will then be 125 meters give or take a meter.
But then thats introduced another issue...
So I am thinking about VD,
Assuming 20A at the furthest point plus an additional 12A evenly distributed, the Ib of 32A then becomes (32 + 20)/2 = 26A, which I would think its fine.
4 x 11.5 x 1000 / 26 / 16 = 110 meters....
So i have got 125 meters, and to stay inside 11.5v I need it to be 110 meters.
However, the predicted readings are:
r1 = 0.57
rn = 0.57
r2 = 1.51
R1+R2 = 0.59
Should I be concerned or even bothered about the 110 meters issue or do I drop it to a 25A or 20A RCBO? but thats not going to overcome the VD.
The Zs will be well within the 1.1 Ohms for 32A
The problem is, there's no way I am going to run 6mm radials, thats just silly.
The other half of the house is even further away from the board, I have intentionally split the circuits down to minimize on length but the further circuit the other side, will be over 100m for a ring and about 80m as a radial...
I have just started a new build today, its a large U shaped bungalow with vaulted ceilings etc.
I have split the property down into a lot of circuits to help with things due to cable runs etc.
I have just wired a section of it today, I was going to do it all in 4mm radials, but by the time I had got to the end of the section (bedroom, Wardrobe, Study & Entrance Hall) I had used 96 meters, this does not include the leg back to the board which is a further 13 meters....
I had given it though on paper, but then when I started cable routes were not quite so straight forward etc.
Anyway, my problem I have now is that the R1+R2 for that circuit at say 110 meters, will be 1.83 Ohms, which is way too much as was going to put it on a 32A, jees I would have to drop it to a 16A to comply.
So then thought, its ok, illt turn it into a ring, total length will then be 125 meters give or take a meter.
But then thats introduced another issue...
So I am thinking about VD,
Assuming 20A at the furthest point plus an additional 12A evenly distributed, the Ib of 32A then becomes (32 + 20)/2 = 26A, which I would think its fine.
4 x 11.5 x 1000 / 26 / 16 = 110 meters....
So i have got 125 meters, and to stay inside 11.5v I need it to be 110 meters.
However, the predicted readings are:
r1 = 0.57
rn = 0.57
r2 = 1.51
R1+R2 = 0.59
Should I be concerned or even bothered about the 110 meters issue or do I drop it to a 25A or 20A RCBO? but thats not going to overcome the VD.
The Zs will be well within the 1.1 Ohms for 32A
The problem is, there's no way I am going to run 6mm radials, thats just silly.
The other half of the house is even further away from the board, I have intentionally split the circuits down to minimize on length but the further circuit the other side, will be over 100m for a ring and about 80m as a radial...
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