Cable And Mcb Selection For Air-con

[petercsea]

? Dodgy electrical installation of an air-con that I want to make safe.

Supply 230V {with new batteries in multimeter }. The cable length is 15.5 meters, say 16 meters and free. The current draw nominally is 11 amps. Could someone run the numbers through and advise me of the appropriate cable size and Square-D MCB that I should use. The temperature maximally is 60 Centigrade in the roof space.

and..........

How do you prevent ants from fizzing a new replaced good Irish made electro-magnetic relay in the compressor of the air-con? Any personal experience or tips please?

Thanks for this folks.

[Crossy]

As a quick and dirty I would suggest 4mm2 cable protected by a 25A 'C' (motor rated) MCB.

EDIT

You could probably use a regular 'B' rated 25A MCB in this particular case.

For the ants you'll need some form of screen, how about ladies stockings? 'spose it depends how big the ants are

[petercsea]

As a quick and dirty I would suggest 4mm2 cable protected by a 25A 'C' (motor rated) MCB.

EDIT

You could probably use a regular 'B' rated 25A MCB in this particular case.

For the ants you'll need some form of screen, how about ladies stockings? 'spose it depends how big the ants are

Thanks Crossy,

Have the specific info on your MCB recomend being sent from the supplier and will order it from local distributor. The cable is fine.

Ladies stockings will try. The ants are tiny little brutes btw service engineer said it is really a common problem.

[Crossy]

Have the specific info on your MCB recomend being sent from the supplier and will order it from local distributor. The cable is fine.

I don't see a 25A in a C curve, this one should do the trick, Square D Qwikline II 20A C Type MCB http://www.brewtime.co.uk/product-detail.asp?d=1391

[Crossy]

This post http://www.thaivisa.com/forum/index.php?s=...t&p=1965087 has useful information on how to find your way around the Scneider Electric online catalog.

This beaker should be readily available in Thailand DOMA41C25 CB BT Domae 1P 25 A Curve C 4500 A http://ecatalog.schneider-electric.com/dsm...0658AM677598339

[petercsea]

This post http://www.thaivisa.com/forum/index.php?s=...t&p=1965087 has useful information on how to find your way around the Scneider Electric online catalog.

This beaker should be readily available in Thailand DOMA41C25 CB BT Domae 1P 25 A Curve C 4500 A http://ecatalog.schneider-electric.com/dsm...0658AM677598339

Thank you again Crossy,

I wasn't able to work my way around the Schneider e-cat it seemed to have dead links throughout following the instructions. Maybe me.

I found one that may be OK. SquareD "QO 125VSC 6T". ?

[Crossy]

I found one that may be OK. SquareD "QO 125VSC 6T". ?

Buggered if I can find that one, you got a link to a datasheet.

If it's 'C' curve and 20-25A should be OK.

[david96]

If the FLC is 11 amps 2 core and earth 2.5sqmm with a protective device (MCB) rated at 20 amps will be ample.

Ref AS/NZ 3000/2007. C frame for general light and power, D frame may have to be used in some circumstances, these are specifically for inductive loads.

[david96]

With ref to my previous post those figures are based on 40 deg C max temp rise, cables not enclosed and in free air. If the operating temp in the ceiling space is 60 deg C you should find an alterative route for the cable.

[Crossy]

David, agree ^^^.

The high temperature on the cable route is why I suggested a 4mm cable, at 60C derated 2.5mm would be marginal.

Always best to over rather than under rate your cable bearing in mind the likely compressor start surge of 40A+

[petercsea]

I found one that may be OK. SquareD "QO 125VSC 6T". ?

Buggered if I can find that one, you got a link to a datasheet.

If it's 'C' curve and 20-25A should be OK.

Thanks Crossy & David/

wrt data sheet the only bits I have are the catalogue 2007 (Thai) and this flyer.

QOvs.pdf

[Crossy]

I found one that may be OK. SquareD "QO 125VSC 6T". ?

Buggered if I can find that one, you got a link to a datasheet.

If it's 'C' curve and 20-25A should be OK.

Thanks Crossy & David/

wrt data sheet the only bits I have are the catalogue 2007 (Thai) and this flyer.

Looks OK rating wise.

Do make sure it will fit in your Load Center / Consumer unit.

[david96]

David, agree ^^^.

The high temperature on the cable route is why I suggested a 4mm cable, at 60C derated 2.5mm would be marginal.

Always best to over rather than under rate your cable bearing in mind the likely compressor start surge of 40A+

I think he should find out why there is a continuous 60 deg C rise in the ceiling space. Even on a hot day in Australia one would be rare to get a ceiling (air) temperature above 45deg C in a residential situation. You could not work in that temperature. The highest temperature I have had to work in and for very short periods was 55 deg C in an industrial situation. Consider a good airflow though the ceiing space to drop the temperature.

[petercsea]

David, agree ^^^.

The high temperature on the cable route is why I suggested a 4mm cable, at 60C derated 2.5mm would be marginal.

Always best to over rather than under rate your cable bearing in mind the likely compressor start surge of 40A+

I think he should find out why there is a continuous 60 deg C rise in the ceiling space. Even on a hot day in Australia one would be rare to get a ceiling (air) temperature above 45deg C in a residential situation. You could not work in that temperature. The highest temperature I have had to work in and for very short periods was 55 deg C in an industrial situation. Consider a good airflow though the ceiing space to drop the temperature.

You're right David. Crossy picked up on the temp sometime ago in another thread. That's another project! Thanks for the interest.

[Crossy]

I think he should find out why there is a continuous 60 deg C rise in the ceiling space. Even on a hot day in Australia one would be rare to get a ceiling (air) temperature above 45deg C in a residential situation.

I'll bow to your greater experience here David. In the UK the only way you'll get any space near 60C is by using a blast furnace, natural heat will get you to 60F