Re: Dangers With Electrical Appliances In Thailand

[elkangorito]

The purpose of an MCB or an HRC fuse or even a rewirable fuse in the distribution board is to protect the cables. That is all. Even electrical engineers often loose site of this little known fact.

An MCB does not and is not intended to protect life.

An MCB gives what is called close protection, it is better than an HRC fuse which has different tripping characteristics and discrimination under fault conditions.

If an MCB trips suddenly as the OP describes then there could be a L to N fault. If there was a problem with the cable extension reel or plug pins heating this is a different tripping mechanism within the MCB and will often take many hours to trip under such overload conditions.

If your appliance tripped out the breaker within a few minutes of turning it on best to get it checked out. Modern MCBs do not trip quickly for no reason at all.

A point to remember;

1] An HRC fuse will operate quicker than a non-current limiting type MCB under high fault current conditions. The two types used in domestic electrical applications are BS88 (10kA) & BS1361 (4kA). Both of these fuses are used to provide "current limiting" (something that a standard MCB cannot do) & not overload protection, so that the downstream switching devices can be reduced in size & more importantly, to reduce the Prospective Fault Current so that damage will not result in all downstream apparatus.

There are, of course, many different "classes/types" of these HRC fuses & as such, have many different uses.

As for the OPs' situation, there are some points that I feel need to be checked;

1] The circuit breaker that tripped is rated at 30 Amps. If this breaker is supplying power outlets, the minimum type & size of this cable should be copper, 6mm squared double insulated 70 degrees C, 300 volt. If the cable is smaller than this, the risk of fire is increased.

2] The maximum size circuit breaker for supplying power outlets in a domestic residence should be 20 Amps. This is to reduce the risk of a fault/fire when the cord conductors of "plug in" items are no less than 0.75mm squared.

3] A 10 Amp extension cord should have a minimum copper conductor size of 1.5mm squared. It should also be double insulated & NOT the "speaker wire" (single insulated) that is commonly used in Thailand.

4] All metal clad appliances must be appropriately connected to earth, unless the appliance is a Class 2 type (double insulated).

5] The only way to find out why the circuit breaker tripped is to inspect;

a. the stove temperature controller,

b. inspect & check the circuit breaker (it could be faulty).

c. inspect & check the connections to the circuit breaker. If the connection(s) are poor, heat can be created, which is then conducted back into the circuit breaker. This heat can cause nuisance tripping.

d. inspect & check the extension cord (it needs to have an insulation resistance test done before it can be safely used again).

6] all power outlets in Thai domestic residences should be protected by an appropriate Earth Leakage detection device. "Appropriate" means;

a. no greater than a 30mA (30 milliamp) detection current.

b. not be adjustable.

c. have a switching time of no greater than 20mS.

[Rimmer]

The purpose of an MCB or an HRC fuse or even a rewirable fuse in the distribution board is to protect the cables. That is all. Even electrical engineers often loose site of this little known fact.

An MCB does not and is not intended to protect life.

An MCB gives what is called close protection, it is better than an HRC fuse which has different tripping characteristics and discrimination under fault conditions.

If an MCB trips suddenly as the OP describes then there could be a L to N fault. If there was a problem with the cable extension reel or plug pins heating this is a different tripping mechanism within the MCB and will often take many hours to trip under such overload conditions.

If your appliance tripped out the breaker within a few minutes of turning it on best to get it checked out. Modern MCBs do not trip quickly for no reason at all.

A point to remember;

1] An HRC fuse will operate quicker than a non-current limiting type MCB under high fault current conditions. The two types used in domestic electrical applications are BS88 (10kA) & BS1361 (4kA). Both of these fuses are used to provide "current limiting" (something that a standard MCB cannot do) & not overload protection, so that the downstream switching devices can be reduced in size & more importantly, to reduce the Prospective Fault Current so that damage will not result in all downstream apparatus.

There are, of course, many different "classes/types" of these HRC fuses & as such, have many different uses.

As for the OPs' situation, there are some points that I feel need to be checked;

1] The circuit breaker that tripped is rated at 30 Amps. If this breaker is supplying power outlets, the minimum type & size of this cable should be copper, 6mm squared double insulated 70 degrees C, 300 volt. If the cable is smaller than this, the risk of fire is increased.

2] The maximum size circuit breaker for supplying power outlets in a domestic residence should be 20 Amps. This is to reduce the risk of a fault/fire when the cord conductors of "plug in" items are no less than 0.75mm squared.

3] A 10 Amp extension cord should have a minimum copper conductor size of 1.5mm squared. It should also be double insulated & NOT the "speaker wire" (single insulated) that is commonly used in Thailand.

4] All metal clad appliances must be appropriately connected to earth, unless the appliance is a Class 2 type (double insulated).

5] The only way to find out why the circuit breaker tripped is to inspect;

a. the stove temperature controller,

b. inspect & check the circuit breaker (it could be faulty).

c. inspect & check the connections to the circuit breaker. If the connection(s) are poor, heat can be created, which is then conducted back into the circuit breaker. This heat can cause nuisance tripping.

d. inspect & check the extension cord (it needs to have an insulation resistance test done before it can be safely used again).

6] all power outlets in Thai domestic residences should be protected by an appropriate Earth Leakage detection device. "Appropriate" means;

a. no greater than a 30mA (30 milliamp) detection current.

b. not be adjustable.

c. have a switching time of no greater than 20mS.

Yep! You've said it all, and I salute your superior knowledge

You obviously stayed awake during that part of the class

[lopburi3]

But I would strongly caution the above "inspections" are not DIY functions for most people - do not take apart anything electrical unless you know what you are doing.

[elkangorito]

Yep! You've said it all, and I salute your superior knowledge

You obviously stayed awake during that part of the class

I'm glad that you salute superior knowledge.

The "class" hasn't ended...it's an on-going thing.

But I would strongly caution the above "inspections" are not DIY functions for most people - do not take apart anything electrical unless you know what you are doing.

Thanks Lop...forgot to put that in.

[JAS21]

1. That plug is designed for export to Europe and does not work in Thai outlets without an adapter. The only place I have seen the adapter is HomePro stores in the packaged electrical items. It is a white plastic slip on that allows the two round pins through it and adds the additional ground pin and mates with the ground on side of plug. If you can't find have a shop install a three pin plug.

2. Check the plug - if three pin and outlets are three pin it is most likely grounded - they often sell three pin outlets with a two pin plug and you know that is not grounded. Check the rating.

3. Lotus would be my last choice (have not seen for ages). Best place are computer stores as they require the grounded outlets and sell good quality cords. HomePro or electrical supply houses should also have. Look for heavy round cord and not too long. It is really best to try and locate units closer to outlet rather than use extension cords.

4. Hopefully the outlet is really grounded - newer places should be but I would always check with a multi-meter to be sure (same voltage from hot to neutral and ground). But that is best done by an electrician with you just watching.

Heres a photo of the Schuko plug and adapter,,,,,,,,,,,maybe it will help the poster

Thanks! Will look for that!

So now, on my HomePro list:

1) Schuko Adapter

2) Longer appliance cord similar to the one which comes with the appliance (actually detachable), of similar or greater thickness of 3X1 sq.mm. If this new cord already has a 3 pin, then no more need to buy the Schuko adapter mentioned above.

3) Anything else I might need for added safety?

One 'good' thing about the dangerous extension cord is that it has it's own 10-15A fuse which acts as a mini circuit breaker and first defense. If I simply replace the cord to a longer one, I will lose this advantage. Anything I can do to still have a mini circuit breaker despite losing the extension cord?

I bought an adapter in Home Pro today...69 Baht...Made in China....Pt No WA-GF(R5B) if thats any help. The package had a CE on it..however my shoes say 'Made in France' but they came from my wifes cousins factory!

[junkofdavid2]

Surprise, surprise!

The same thing happened to me again one year afterward... with exactly the same action (ELB tripped while I was turning down the same electric stove after about 30 min of use).

After it happened to me the first time (more than a year ago), I had the stove checked/repaired at the official Hanabishi service center, bought a schucko ground plug adapter to make it a 3-pin plug (the plug's end has provision to adapt to a schucko, yet the part which plugs into the appliance is only 2 pin???), and bought a heavy-duty very thick but short extension cord (3x 1.5mm) with a built in fuse (5x25 16A 250V).

I have had NO problems for more than a year.

And then today, there was again a small "pop" near the appliance knob/switch as I was turning the heat LOWER (not higher), and my apartment's ELB apparently tripped and shut off my TV as well (does a TV have a heavy load, enough to overload a circuit?)

I reset the ELB and no problems and no tripping (although I didn't dare switch the appliance back on).

Would it help prevent this phenomena if I switched to a higher-end western brand electric stove (i.e. Verasu) with a proper 3-pin plug?

Any other thoughts?

.

Edited May 3, 2009 by junkofdavid2

[lopburi3]

ELB normally trips because of a ground fault rather than load. I expect the problem with cooker is a short to ground (case) as you turn the control. This may well be due to an insect or lizard making his home in the units and just require a good cleaning. Likely the short was enough to remove the problem. I would turn on and run through full range, touching only the insulated plastic. If trips again I would have serviced but it not the service will likely be 'no problem found'. Although they might take the time to clean any accumodated dirt out.

[junkofdavid2]

Thanks Lop.

1) With regard to the lizard or whatever which may have caused the short... it could also be because my stove's knob is kinda oily now after a year of use?

2) It is not insulated by plastic... it's metal inside out. That's another concern why I'm thinking of changing to a western brand (in addition to the ambiguity of whether the appliance has a ground or not).

To Lop and others:

By the way, I'm a bit worried about "what if" the ELB fails next time and doesn't trip... that can cause a fire right?

Is there a way I can install an additional ELB or Safety-Cut just on the power-outlet where I plug the stove? That way I'd have 2 layers of protection? How?

.

Edited May 3, 2009 by junkofdavid2

[lopburi3]

I was talking about the adjustment knob being plastic - just turn that without touching unit should be safe (although you might want to remove and clean the oil off it) - a rubber dish glove should be good protection when making a test - for more protection wear shoes or stand on a rubber mat.

You have several layers of protection already. The ELB will trip fast on a short. The breaker of the ELB (or any others) will break if there is a major draw of current (and likely before any major chance of fire). Is your home wood? Most cement homes have few areas that an overload would be a serious fire hazard. You also have attached the ground I believe so that helps protect you and should trip breakers faster.

Although you could add another ELB don't believe it is needed and have not seen any outlet type units for sale here. You would probably be better off buying a new cooking unit than adding more ELB's.

Edited May 3, 2009 by lopburi3

[junkofdavid2]

Thanks for the input.

Yeah, I think it's time for a new cooking unit. I bought that cheap local Hanabishi more than a year ago when I was kinda hard up on money. Now I'm much more financially flexible so I think I'll go for a German brand... Severin. (Any comments on Severin folks?)

Checked it out in Paragon today and it's on sale about 30% off. And, although it has a 2-pin, there's a provision for a 3rd ground pin via a schuko plug. (Unlike the Hanabishi which has provision for a 3rd pin with schuko for the wall-outlet end, but only 2 pins on the other end which attaches to the main unit... weird.)

[lopburi3]

Only two pins - missed that - in that case it is not grounded even if you installed an adapter for the outlet plug. Go ahead and get that new unit.