Metal vs plastic electric wall boxes

[OneMoreFarang]

 

In my condominium renovation I need lots of electric wall boxes.

From Europe I am used to plastic boxes. They seem to work just fine.

Yesterday an experienced Thai electrician, who is used to customers who want quality and not cheap, told me they always use metal boxes but he couldn't tell me the advantage of them.

If cost is not an issue would you use plastic or metal boxes. They are in the wall like in the sample pictures below.

 

Until now I think plastic is the better choice because even if a cable is damaged plastic is no electric conductor.

And because they are fixed in the wall they don't get damaged or eaten by rodents or something like this.

What do you think?

 

 

 

 

 

 

[FriendlyFarang]

In Germany I only know metal ones from really old buildings.

I think today nobody uses metal anymore, it's always plastic.

I just tried looking it up on Google, if searching in German I can't even find any metal ones, maybe they are not allowed anymore due to safety concerns or similar.

[lopburi3]

In the very old days in USA (and perhaps still) metal was used along with conductive metal conduit which acted as the ground wire.  Not great as any bad connection to box and ground was gone.  Expect many of those asking for metal are from that era/land.  Original plastics were not much for longevity.   

[unheard]

An interesting question (plastic vs metal box).

I wasn't even aware of the plastic boxes being used in Thailand.

Right now I'm observing two houses being build by a very high-end (many expensive farang houses) and low-end building companies.

Both are using metal boxes.

[sometimewoodworker]

1 hour ago, unheard said:

An interesting question (plastic vs metal box).

I wasn't even aware of the plastic boxes being used in Thailand.

Right now I'm observing two houses being build by a very high-end (many expensive farang houses) and low-end building companies.

Both are using metal boxes.

Go into any of the big stores and you will discover many things that you are not aware of.
 

Or go a website devoted to building cool Thai houses, and you will see that plastic boxes are not uncommon 

 

[Photoguy21]

Metal ones are ok but they have to be earthed properly

[phetphet]

You say they don't get damaged. I have a plastic one set the cement in a tiled floor. About fourteen years old. The plastic has deteriorated and broken away where the screws hold the socket.

 

Now I have to try and get the old box out from the cement to replace without damaging the ceramic floor tiles. I wish they had installed a metal one.

[unheard]

7 hours ago, Photoguy21 said:

Metal ones are ok but they have to be earthed properly

Why?

[lopburi3]

1 minute ago, unheard said:

Why?

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.

[unheard]

8 hours ago, sometimewoodworker said:

Go into any of the big stores and you will discover many things that you are not aware of.
 

Or go a website devoted to building cool Thai houses, and you will see that plastic boxes are not uncommon 

 

That's all fine, but can you comment on why do Thai builders are still commonly using metal boxes instead of switching to plastic as observed in the west?

[unheard]

4 minutes ago, 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.

What is the possibility of wires becoming live?

What can possibly happen to insulation?

[peterfranks]

8 minutes ago, 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.

Faceplates don't have screws, they are hidden under the faceplate

[digbeth]

10 minutes ago, unheard said:

That's all fine, but can you comment on why do Thai builders are still commonly using metal boxes instead of switching to plastic as observed in the west?

It's more malleable? many botched install job means bending or smashing the corners in, I know many screw holes don't line up properly from the cavity being not to size and the box was bent to fit in

[lopburi3]

11 minutes ago, peterfranks said:

Faceplates don't have screws, they are hidden under the faceplate

They do/did in the USA as ground wire is/was attached to them for ground in adaptor plugs.  Guess my years showing.  

[peterfranks]

1 minute ago, lopburi3 said:

They do/did in the USA as ground wire is/was attached to them for ground in adaptor plugs.  Guess my years showing.  

Yes we are 2022 already ????????

[lopburi3]

6 minutes ago, peterfranks said:

Yes we are 2022 already ????????

Where did the century go?  

[OneMoreFarang]

2 hours ago, unheard said:

What is the possibility of wires becoming live?

What can possibly happen to insulation?

Pulling them over sharp edges can happen.

And having cut the wire isolation while removing the outer cable isolation (sorry, I don't know the exact term) can happen.

[unheard]

13 hours ago, OneMoreFarang said:

Pulling them over sharp edges can happen.

And having cut the wire isolation while removing the outer cable isolation (sorry, I don't know the exact term) can happen.

yes, lots of things can happen mechanically during improper installation.

But really what's the probability for any of such events if done by even a half-competent electrician?

If the electrician is that incompetent to badly screw up wiring of the simple box then I think the difference in safety of materials of the box itself would not really matter and be the least of the house owner's concerns.

[Photoguy21]

18 hours ago, unheard said:

Why?

Because if you get a fault, which you shouldnt but you have to work on safety, an earthed box will trip the CB and not go through you.

[unheard]

1 hour ago, Photoguy21 said:

Because if you get a fault, which you shouldnt but you have to work on safety, an earthed box will trip the CB and not go through you.

Now you're getting me real confused.

My "why" question was related to your statement on the metal boxes needed to be earthed properly.

Do they ever get earthed in such installs, here in Thailand?

It's an honest question. Is there such a requirement?

And if there is, then why would the builders over here favor metal boxes over plastic?

The plastic ones would require much less work...

We're talking electrical installations with earth/ground wires utilizing either metal or plastic boxes connected to standard plastic conduits,  not the old school all metal box-to-conduit earthed systems.

So far I've seen just metal boxes being used in two different house designs, all connected to plastic conduits.

 

[peterfranks]

20 hours ago, lopburi3 said:

They do/did in the USA as ground wire is/was attached to them for ground in adaptor plugs.  Guess my years showing.  

Maybe I'm confused, but looks more like a pre-historic adapter, than a faceplate to me.

[lopburi3]

22 minutes ago, peterfranks said:

Maybe I'm confused, but looks more like a pre-historic adapter, than a faceplate to me.

Actually currently being sold and attaches to faceplate screw.  Another type has a wire/spade terminal to put under screw.  You must consider our NE home was built in 1775 so had a few old electrics - but in USA suspect there are still many homes with the old two prong outlets, even if not up to code.

[Photoguy21]

1 hour ago, unheard said:

Now you're getting me real confused.

My "why" question was related to your statement on the metal boxes needed to be earthed properly.

Do they ever get earthed in such installs, here in Thailand?

It's an honest question. Is there such a requirement?

And if there is, then why would the builders over here favor metal boxes over plastic?

The plastic ones would require much less work...

We're talking electrical installations with earth/ground wires utilizing either metal or plastic boxes connected to standard plastic conduits,  not the old school all metal box-to-conduit earthed systems.

So far I've seen just metal boxes being used in two different house designs, all connected to plastic conduits.

 

I did at our house but I made sure they did provide a proper earth.

[sometimewoodworker]

23 hours ago, unheard said:

That's all fine, but can you comment on why do Thai builders are still commonly using metal boxes instead of switching to plastic as observed in the west?

You are drawing incorrect conclusions from inadequate information.
 

Along with Thai installers who do not have the correct information. 
 

Metal boxes are designed for use with armoured cable or metal conduit. Surface mounted cable is often and in some countries virtually exclusively in metal conduit. 

 

Using metal boxes with plastic conduit adds a requirement to earth each box, a step that is often overlooked in Thai installs. Pattress boxes or plastic recessed boxes are correct for the majority of Thai installs 
 

[unheard]

14 hours ago, sometimewoodworker said:

You are drawing incorrect conclusions from inadequate information.
 

Along with Thai installers who do not have the correct information. 
 

Metal boxes are designed for use with armoured cable or metal conduit. Surface mounted cable is often and in some countries virtually exclusively in metal conduit. 

 

Using metal boxes with plastic conduit adds a requirement to earth each box, a step that is often overlooked in Thai installs. Pattress boxes or plastic recessed boxes are correct for the majority of Thai installs 
 

I'm drawing my conclusions from real life examples on two different construction sites.

Both sites use licensed electricians.

Are you saying both of them are out of compliance?

Your assumptions sound quite reasonable but at the same time I find it  difficult to believe that both electricians in my example have broken the code since there's no any incentive for them to do that, not even a financial one.

btw, is there a specific code?

I'd really like to get a confirmation from someone closely familiar with the Thai electrical codes.

 

[unheard]

15 hours ago, sometimewoodworker said:

Pattress boxes or plastic recessed boxes are correct for the majority of Thai installs

Pattress boxes may be made of metal or plastic.

[sometimewoodworker]

3 hours ago, unheard said:

Pattress boxes may be made of metal or plastic.

They may but in the U.K. they are not usually.

[sometimewoodworker]

3 hours ago, unheard said:

I'm drawing my conclusions from real life examples on two different construction sites.

Both sites use licensed electricians.

Unless you have actually seen the qualifications that situation is as rare a hen’s teeth here. There are vanishing few actual electricians working in house building.

 

3 hours ago, unheard said:

Are you saying both of them are out of compliance?

No, as I haven’t read the Thai electrical code, however it’s extremely likely that they are going from the codes that it is based on.

 

3 hours ago, unheard said:

I find it  difficult to believe that both electricians in my example have broken the code since there's no any incentive for them to do that, not even a financial one.

The incentive is that it’s vastly easier and faster to use plastic conduit, so if they are charging on a piece rate as every electrician I’ve employed, both licensed and unlicensed, does that seems like a rather large financial incentive.  

 

these are correctly mounted metal conduits, I can be sure that they took more than 4 times longer to install than plastic would have done

4 hours ago, unheard said:

btw, is there a specific code?

yes @Crossy has the links to buy it

[unheard]

36 minutes ago, sometimewoodworker said:

these are correctly mounted metal conduits, I can be sure that they took more than 4 times longer to install than plastic would have done

But those are installed on the outside.

From what I've seen it's only common to use plastic conduits in the walls and attics.

As per OP question what would be an incentive for a Thai electrician to use metal pattress boxes when working with plastic conduits instead of going all parts plastic?

So far in this thread I came acrross two reasonable conclusions:

 

1. digbeth: metal is mallable - easier to align the screws if installed misaligned.

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

[Crossy]

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.