Metal vs plastic electric wall boxes

[HauptmannUK]

In the UK it is usual to use galvanised metal back boxes let into brickwork or blockwork. The back box has an earthing terminal, however this is not normally used because the box will earth via the fitting's 3.5mm mounting screws.

Boxes mounted into stud/hollow walling are normally plastic and come with anchor 'wings' to lock them into the wall.

Metal boxes are more durable than plastic. I recently did some work on a property that was built in 1960 and the metal boxes were in perfect shape. In contrast some plastic junction boxes that were fitted about 25 years ago had gone brittle and had cracked.

[carlyai]

Been watching this thread (not all) and just from my experience initially helping the electrician with some house building wiring and then myself wiring a 3 room garage, I used the plastic boxes.  That's what the house wiring electrician used.

I think which ever boxes you get used to are the ones you use.

Important to have good quality boxes so  they don't distort too much and screw threads that are solid in construction.

By the time you grind out the blockwork spaces for the conduit and boxes and position them to allow for the plaster, then insert the conduit into the boxes and terminate the cables you need a good quality lot of boxes.

So it's good quality plastic boxes for me and I've got power points everywhere.

[sometimewoodworker]

1 hour ago, unheard said:

2.1 phetphet: over time plastic deteriorates and brakes away where the screws hold the socket

2.2 HauptmannUK: metal boxes are more durable, plastic gets brittle and cracks

These 2 only apply to poor quality plastics 

[OneMoreFarang]

26 minutes ago, carlyai said:

good quality plastic boxes

Do you or anybody else have an example for good quality plastic boxes in Thailand.

I bought these as samples and on my first impression I like them. But I have limited experience with any of those boxes.

 

 

FLUSH MOUNTED BOXE BTICINO 2"X4" 503 E YELLOW (homepro.co.th)

 

[sometimewoodworker]

1 hour ago, unheard said:

But those are installed on the outside.

Mounted inside or outside is immaterial it’s the correct method of mounting that is relevant, the point is that done correctly it takes time.

 

[carlyai]

22 minutes ago, OneMoreFarang said:

Do you or anybody else have an example for good quality plastic boxes in Thailand.

I bought these as samples and on my first impression I like them. But I have limited experience with any of those boxes.

 

 

FLUSH MOUNTED BOXE BTICINO 2"X4" 503 E YELLOW (homepro.co.th)

 

Global House (GH) wasn't around my area when I wired up my shed. I think Global House boxes should be OK. I tend to look for the most expensive brand in GH. Most expensive is not always equal to best quality.

[bluejets]

Metal wallbox might stay stuck to the mortar better than plastic.

 

Downside is the metal wall box needs to be earthed as the wall box will contain single insulated cabling.

[HauptmannUK]

48 minutes ago, sometimewoodworker said:

These 2 only apply to poor quality plastics 

Can you advise on how to identify 'good quality' plastic?  As I posted earlier, we have galvanised metal wall boxes in our workshop in the UK that were installed in the early 1960's that basically look good as new. We also have plastic junction boxes installed about 30 years ago that have gone brittle. The plastic items are MK brand (a reputable UK brand). 

[carlyai]

13 hours ago, carlyai said:

Global House (GH) wasn't around my area when I wired up my shed. I think Global House boxes should be OK. I tend to look for the most expensive brand in GH. Most expensive is not always equal to best quality.

I can only find 2 larger boxes, no small red ones left.

As I said I put power points everywhere.

One pic. of one in the store room I offset too much and didn't have time to correct before the plaster came. 

Also a few walls cracked as blocks not properly layed.

I specially went to a QCon place and arranged to hire their team, but as it was QCon block early days the QCon forman for my area was moonlighting and getting anyone to lay blocks. Eventually got rid of them but damage done.

Pics of power points and switches everywhere. Better to have too many than not enough.

 

[Photoguy21]

On 7/19/2022 at 7:42 PM, lopburi3 said:

They could become live?  Even if the faceplate is plastic the screws holding it are metal and if live wire touched box it would be live.  If box grounded breaker would hopefully trip before someone touched it.

The first bit I agree with but relying on the trip circuit when the current is passing through your body I disagree with. If the box is earthed the CB will trip without using yourself as the ground.

If you touch something live and you have been sweating a current of as low as 20mA can be fatal.

[tjo o tjim]

Looking at the OP's two sample pictures is exactly why I would not use metal boxes in Thailand.  First off, stamped galvinized boxes are not that good embedded in a concrete wall.  Second, and arguably more importantly, is that if you aren't using the right fittings you are just making a mess that is hard to work with down the road.  I find it amusing that US-style conduit work is becoming so much more common in Thailand.  Unfortunately they generally are doing it wrong and a UK-styled trunking system would provide so much more of a practical solution.

 

Now, there are cases where you might have exposed boxes that a metal box would provide a better end product... but it likely should be a cast box and not a stamped box, and I can guarantee you that they won't have all the proper connections.

[tjo o tjim]

20 hours ago, HauptmannUK said:

Can you advise on how to identify 'good quality' plastic?  As I posted earlier, we have galvanised metal wall boxes in our workshop in the UK that were installed in the early 1960's that basically look good as new. We also have plastic junction boxes installed about 30 years ago that have gone brittle. The plastic items are MK brand (a reputable UK brand). 

They have only really had proper UV-cured plastic boxes for the last ~15 years.  Look for a label saying that they are suitable for outdoor installation.

[OneMoreFarang]

3 minutes ago, tjo o tjim said:

I find it amusing that US-style conduit work is becoming so much more common in Thailand.  Unfortunately they generally are doing it wrong and a UK-styled trunking system would provide so much more of a practical solution.

What is the difference?

[tjo o tjim]

Just now, OneMoreFarang said:

What is the difference?

I think of a typical UK system using trunking-- a 3x3 to 5x5cm wireway that they put a bunch of wires into for the main runs, and then they might branch off with conduit going to a device.  A typical US system will have multiple conduit sizes instead of the trunking/wireway, and junction boxes as needed to split things up.

 

Most of the Thai metal conduit work I see is a bunch of conduits, often doubled up because they did not have a bigger size, and with more LB fittings than you can imagine in order to go around beams.  Essentially it is planned the exact same way that they would plan surface-mounted wiring.

 

The art of doing a nice conduit installation is planning everything out in advance so that it is no more complex than required for the job.  Looping around a beam every 3.5m when advanced planning would yield a sleeve through the beam is one example... but there are also other ways to route things where you don't need the complexity.  

 

The connectors are where things go wrong with conduit work here.  The more you have, the more wrong it goes.

[Encid]

23 hours ago, Crossy said:

You need "Standard Electrical Installation for Thailand, 2013" https://eitstandard.com/มาตรฐานการติดตั้งทางไฟ-2/#

 

Obviously it's in Thai.

 

Unfortunately there's nothing aimed specifically at domestic but at least the document is cheap.

 

If you want a western standard that comes pretty close then AS3000 is your best bet.

 

You can read that or obtain a pdf copy here.

 

[Crossy]

1 minute ago, Encid said:

You can read that or obtain a pdf copy here.

 

Nice one ???? 

 

AS3000 is rather more strict than the Thai regs so following it should be fine. Otherwise this PEA document is also worth looking at.

Groundwire Mk2 book-Manual.pdf

 

The most important difference is the local implementation of MEN by routing the incoming  neutral via the ground bar. You must do it this way to pass your MEA/PEA inspection for a permanent supply. The relevant diagram from the PEA guide with my translations.

 

[OneMoreFarang]

3 hours ago, Crossy said:

 

Nice one ???? 

 

AS3000 is rather more strict than the Thai regs so following it should be fine. Otherwise this PEA document is also worth looking at.

Groundwire Mk2 book-Manual.pdf 803.56 kB · 0 downloads

 

The most important difference is the local implementation of MEN by routing the incoming  neutral via the ground bar. You must do it this way to pass your MEA/PEA inspection for a permanent supply. The relevant diagram from the PEA guide with my translations.

 

Thanks

Looking at that drawing and black, grey and green wires, are there any regulations which colors have to be used? I am used to brown, blue and green/yellow. Can I use cables with those colors? Thanks.

[Crossy]

6 minutes ago, OneMoreFarang said:

Thanks

Looking at that drawing and black, grey and green wires, are there any regulations which colors have to be used? I am used to brown, blue and green/yellow. Can I use cables with those colors? Thanks.

 

I understand that the blue, brown, green/yellow colours are "the new normal" for Thailand, but, TiT ...

[sometimewoodworker]

2 hours ago, OneMoreFarang said:

I am used to brown, blue and green/yellow. Can I use cables with those colors? Thanks.

No no no, Thailand electricity will get confused and not understand which colour it should go down ????

 

[OneMoreFarang]

2 hours ago, sometimewoodworker said:

No no no, Thailand electricity will get confused and not understand which colour it should go down ????

 

That's ok. I don't plan to let any Thai electrician near my installation.

[Boyn]

Metal boxes are the most common ones in the UK,If the box is for a light switch it would be earthed, if it is for a socket the earth can come from the fixing screw which is earthed through the socket ,as long as the box has 1 fixed lug and 1 adjustable lug.Many years ago an earth was taken from the socket earth terminal and connected to the box ,this was known as a fly earth. I still like this but thats cos im an old sparky.

[sometimewoodworker]

12 hours ago, OneMoreFarang said:

That's ok. I don't plan to let any Thai electrician near my installation.

On a slightly more serious note as long as (where needed) the colours are consistent it’s perfectly OK.

 

I have a lighting setup were there are 3 different circuits running side by side (fake dimming) so to make troubleshooting easy neutral is common and white and the circuits lines are red yellow and blue. With 1mm square wire and being 3.8 metres up it’s no problem