Main electric wire gauges

[Sheryl]

Major lightning strike near the house did something that loosened the connection on the main power cable coming into the house (near the entrance to the house), was repaired but the local sparky who repaired it - -and who seemed to be pretty knowledgable compared to most I have dealt with here, though that bar is very low - said I should replace all the wiring from the meter to the house when I have a chance, apparently it is a bit frayed (?). It has been up for 20 years, in a rural environment with very frequent heavy storms and frequent power surges so I am inclined to believe him and we are about to start work but I just want to be sure on a few points:

 

1 - the list of materials he gave me in the budget shows cables size no.25 and size no.35, apparently based on what is currently there, seemingly it is one size running from the meter to the post in front of my house and another running from the post into the house. After some questioning by me he said he could use all no. 25 and assured me this is large enough, he says it is the same as the main electric cables along the road. Is this true? And can it handle up to 100 amp coming in (that's what the house is wired for though I doubt I draw that much). He seems to know his stuff but in past years I have had local "electricians" do wiring in which they installed wires way too thin to handle the load and came close to burning my house down, so once bitten, twice shy. I have tried to look online but only find references to in-house wiring gauges, can't find anything the explains what no. 25 and no. 35 cables are.

 

2- while he is at it he will install a Safe-T-Cut, long overdue. There is a main breaker located right outside my front door prior to the wires going up to the control panel (which has a second main breaker, but the downstairs a/cs aren't on it for some reason and I've been told very hard to correct that, hence the second outside breaker to be able to turn off all power easily). Plan is to change that to a Safe-T-Cut. I'm told it will replace the breaker altogether, is that correct? I was originally told it would be additional, so I'm a bit confused, though it looks to me like it also functions as a breaker?

 

3- I could not source a 100amp Safe-T-Cut, largest available was 63 amp. We tested with all a/cs on etc and looks like what I draw down is below that so I'm told it should be fine. Is this correct?  Any potential risk to having more juice in the line coming in than the breaker is rated for, other than it shutting off? And is it correct that a single Safe-T-Cut on the main power supply will do the trick or do I still need to do soemthing at the circuit board?

 

4-Is there something I can/should do to protect the Safe-T-Cut breaker from surge damage? How vulnerable are they to it? They aren't cheap so I don't want to be replacing them several times each rainy season.

 

Thanks!

 

 

[Crossy]

1. Is he proposing copper or aluminium cable? Aluminium is a lot cheaper but needs to be bigger than copper. I would suggest 25mm² copper or 35mm² aluminium (subject to the distance from the meter to your house).

 

2. You can do either, it makes no odds to the functionality.

 

3. The Safe-T-Cut will protect itself if you go much over 63A so no danger of cooking it. What size is your meter? It will be marked 5-15, 15-45 or 30-100.

 

4. It would certainly be wise to include a decent surge protection device (SPD) in front of the Safe-T-Cut. Safe-T-Cut units are pretty robust anyway, but if you have any technology and are in a high lightning area (all of Thailand really) then installing an SPD is a good idea.

 

[Sheryl]

The meter is marked 30 (100) Amp

 

I don't know if he plans aluminum or copper, I will ask. Is one more durable than the other or are they the same? The distance from meter to house is about 85 meters

 

What type of SPD would you suggest for a 63A Safe T Cut?

 

Thanks!

[canopy]

I am surprised no one has responded. 85 meters is an unusually long run. Thus, make sure make a proper cable size calculation is performed because conventional wisdom will not be good enough. Cable size will also depend on how big a main breaker you end up using. If 100A there is no way you could use 25mm², even copper, for this job.

 

[Crossy]

25mm² copper (or 35mm² aluminium) will be ok for up to 80A on a 85m run (5% volt drop) provided the supply isn't already low. You'd need 50mm² copper ($$$) if you wanted to use the full capacity of the 30/100 meter.

 

@Sheryl As to surge protection ask your electrical man what's availalble in your area, you may end up ordering on line. 

 

Something like this (2 pole 100kA unit) :-

https://www.aliexpress.com/store/product/CHNT-CHINT-Surge-Protective-Device-1P-2P-3P-4P-15kA-40KA-65KA-100KA-NU6-II-40/1984300_32854227833.html

It will need a box of course.

 

 

[Sheryl]

Thanks. Work already done using no.25 copper and installing a 63A Safe T Cut breaker. So far so good.

 

The old cables once taken down, I could see  they were worn down to almost the internal wiring, which showed through in many places. So good that I went ahead and did this.

 

I could nto find a surge protestor and workman had no clue what I meant, neither did local Home Pro. I think what I will do is when I next need to replace my whole house Leonic surge protector  (they seem to last just a couple of years before all the surges fry them) I will install it not at the main circuit board where it now is but outside before the Safe T Cut.

 

 

[sometimewoodworker]

14 minutes ago, Sheryl said:

I could nto find a surge protestor 

That is usually me complaining about how much is being sucked from my wallet with lighting damage. ⚡ ????

[kamalabob2]

Any Schneider Electric dealer can open the catalog about surge Protection Device (SPD) catalog number QOSPD20.  This product is in stock in Thailand. Other brands may carry similar products. Home Pro staff might be unaware of such safety devices in Thailand. This is shown on page 29 and again on page 39 and page 41 of the current Schneider Electric catalog I read in Buriram. Written installation guide on page 41.