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Need Help From Electrician


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Hi all!

I'm building a small garage and it is soon ready. Unfortunately I have problems finding a real electrician here south of Udon.

The guy building the house is asking me what cabels I want, and that scares me. :)

Anyhow I have a 15(45)A meter at the electrical pole outside the land. (Does the 45A denote some kind of maximum usage?)

I have a panel with a 65 A main circuit breaker. The electricity will be brought into the house underground. The distance is about 60 meters. What dimension do i need for the cabel underground?

Thanks for all help!

/MLK

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Are you wondering what cables to the house or the garage?

As for meters, I don't know if anybody really knows what the specs are for LOS, but what you say seems to be the accepted.

I too have 15a meter with 60a main breaker and the PEA said to use 25mm2 AL from the meter to my CU. So, that's what I did (and that should support 60a just fine). Underground shouldn't be much diff but you need to have it in solid conduit.

If you are just tailing off from your house to the garage - and it's not too far - you should be able to use the normal 2.5mm2 cable for 20a circuit (and should be with ground - I use the green 1mm2 for that).

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The underground cable should preferably be a copper cable of type NYY and run in the black PE cable run. Suppliers of NYY cables are Bangkok Cable and Thai Yasiki.

The indoor cables should be of type THW.

The cable sizes (cable areas) will depend on the load in addition to the 60 m lenght that you have mentioned. The recommended maximum voltage drop should not exceed 5%.

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I'm a bit confused.

First you say this, "I'm building a small garage and it is soon ready", & then you say this, "The guy building the house is asking me what cabels I want". You then go on to say, "The electricity will be brought into the house underground. The distance is about 60 meters. What dimension do i need for the cabel underground?"

Questions:

1] How many buildings are you talking about? From my understanding, there is a house (under construction) & you wish to add a garage.

2] Do you want to know the cable size for;

a] the cable from the street to the house? or,

b] the cable from the house to the garage?

BTW, the info in the above link is of little use at the moment.

Edited by elkangorito
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If 45A is the max demand and the route length of the consumers mains is 60 metres you will require 25sqmm min. Cu.

If the max demand is the setting of the MCB ( 60A/63A) the size will be 25sqmm.min.Cu.

Those figures are for a 3% voltage drop between the point of connection to the consumers mains and the main switchboard.

Allow up to 2% voltage drop within the installation.

Ref. AS3000.

 

 

Edited by electau
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The 15(45)A means 45 amps is the meter's max rating and the 15 means the meter's test amperage point for accuracy. Actually, when meters are tested for accuracy they are checked at various points but the test amperage is the primary test point. Usually the test amperage rating is "approx" 1/3 of the max rating like a 30(100)A meter which means 100 amps max with a test amperage of 30 amps. Meter manufacturers can pretty much pick the test amperage rating, but they seem to choose a number aroud 1/3 of the max rating, which some may say is the average 24/7 current a household will draw with a properly sized electrical system/meter.

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Lots of mentions of voltage drop in the above posts, certainly you mean to say amperage and not voltage as with A/C the voltage will be consistent no matter what the distance is but it's the amperage that fluctuates according to load and cable size.. I.E. 240 will still be 240 if tested regardless of line size or load..

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No, you will have a voltage drop due to cable resistance caused by construction of the cable, heating from amperage draw, etc. Also, as the line resistance goes up you also have a reduction in current/amps since the input voltage of 220V remains constant from a well supplied transformer feeding the area/home..

Regarding the voltage drop and to use an extreme example, a break in the line from the pole/meter to the house would be the same as super high/infinite resistance with no amperage flow. E=I*R. 0 amps times infinite resistance equals zero volts....or a total voltage drop and no current flow. Now you would still measure 220 volts at the pole/meter, but after the break in the line you would measure zero volts.

Edited by Pib
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Lots of mentions of voltage drop in the above posts, certainly you mean to say amperage and not voltage as with A/C the voltage will be consistent no matter what the distance is but it's the amperage that fluctuates according to load and cable size.. I.E. 240 will still be 240 if tested regardless of line size or load..

Huh???? My voltmeter shows very significant reductions when I increase the load!

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^

Then you got electrical issues you need to deal with..Your amperage will drop but not your voltage.. It remains at 240 and that also goes for the post above you..I can have every appliance on in my house and will still read 240 volts at the source..

Edited by WarpSpeed
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No, you will have a voltage drop due to cable resistance caused by construction of the cable, heating from amperage draw, etc. Also, as the line resistance goes up you also have a reduction in current/amps since the input voltage of 220V remains constant from a well supplied transformer feeding the area/home..

Regarding the voltage drop and to use an extreme example, a break in the line from the pole/meter to the house would be the same as super high/infinite resistance with no amperage flow. E=I*R. 0 amps times infinite resistance equals zero volts....or a total voltage drop and no current flow. Now you would still measure 220 volts at the pole/meter, but after the break in the line you would measure zero volts.

Poor example it goes without saying, if a line is in tact though you have no voltage drop nor would you have any voltage drop at the site of the break on the pole side but conversely you can have a break that still makes contact but can not carry load so you will read a voltage of 240 but it will not operate any appliances even a light bulb this is how you check a broken line if you still have voltage readings you put it under load and read the amperage or it will not run at any point..

I'd like to add the caveat that these are in proper cable and wire gauge application scenarios and if you have other then you are not properly spec'd for your load considerations..

Edited by WarpSpeed
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There is too much 'misinformation' here. Besides, the OP hasn't been back to clarify exactly what he is talking about.

In the meantime, cable length & voltage drop are proportional quanities...the longer the cable, the greater the voltage drop.

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^

Then you got electrical issues you need to deal with..Your amperage will drop but not your voltage.. It remains at 240 and that also goes for the post above you..I can have every appliance on in my house and will still read 240 volts at the source..

I know that I have problems: 1 mile of 50mm cables (as advised by the ever helpful PEA) between house and transformer. My point is voltage can drop – though I see you now cover this with your caveat in your next post.

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^

Then you got electrical issues you need to deal with..Your amperage will drop but not your voltage.. It remains at 240 and that also goes for the post above you..I can have every appliance on in my house and will still read 240 volts at the source..

I know that I have problems: 1 mile of 50mm cables (as advised by the ever helpful PEA) between house and transformer. My point is voltage can drop – though I see you now cover this with your caveat in your next post.

I mile ( 1.6km ) of 50mm copper conductor, yes one will have voltage drop depending on the demand, was this over one phase only or balanced over 3 phases and neutral?

One was surprised that the PEA did not extend the HV line and install a distribution transformer closer to your property line.

What is your max demand in amps per phase?

Voltage drop is measured from the point of connection of the consumers installation, voltage drop on the distribution network is calculated separately.

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