Sunday, 13 July 2014

Interlude: The Electric Kettle Conundrum

So I decided to start using an electric kettle to prepare myself some coffee from this semester onwards. I naively thought that this was a simple matter of unpacking the electric kettle that I had stored away in my cupboard for the last two years, boiling some water in it and getting delicious, steaming coffee. Life is rarely that simple.

I first plugged the kettle into a spike buster that I have in my room. In about five minutes I hear a electric whizzle and see a quick burst of electric white sparks coming from my spike buster. Oops. I blew a fuse. I checked the electrical rating of my kettle. It was rated for 13A and 250V. I checked the fuse of the spike buster. It was rated for 13A and 250V. I guess I was driving the poor instrument at it's limit! Brushing aside the problem of getting a new fuse for the spike buster, I decided to see if it was possible to run the kettle directly off the wall socket.

But just before I connected the kettle and turned it on, I paused for a second. The memory of the white sparks was still fresh in my mind. So I decided to figure out whether the wall socket that I had in my room was capable of delivering the 250V 13A that the kettle required before I plugged it in and possible caused a fire that burned the whole building down.

So I started researching on plugs. Boring? Absolutely not! It turns out that engineers are very systematic creatures that draw up standards for pretty much everything under the sun. So I started hunting for the standards for electrical plugs in India. After a bit of googling I found that there are three standard types of plugs used for wall sockets in India; Types C, D, and M.

Type C
Type M
Type D
Since I wasn't too interested in the Type C plug (I didn't have any in my room) I pulled up some specs on the plugs. I lifted all this stuff directly from this website.

[The Type D plug] has three round prongs that form a triangle. It is a 5A plug. The central earth pin is 20.6 mm long and has a diameter of 7.1 mm. The 5.1 mm line and neutral pins are 14.9 mm long, on centres spaced 19.1 mm apart. The centre-to-centre distance between the grounding pin and the middle of the imaginary line connecting the two power pins is 22.2 mm. Type M, which has larger pins and is rated at 15 amps, is used alongside type D for larger appliances in India, Sri Lanka, Nepal and Pakistan. Some sockets can take both type M and type D plugs.
Although type D is now almost exclusively used in India and Nepal, it can still occasionally be found in hotels in the UK. It should be noted that tourists should not attempt to connect anything to a BS 546 round-pin outlet found in the UK as it is likely to be on a circuit that has a special purpose: e.g. for providing direct current (DC) or for plugging in lamps that are controlled by a light switch or a dimmer.
Type D plugs are among the most dangerous ones in the world: the prongs are not insulated (i.e. the pin shanks do not have a black covering towards the plug body like type C, G, I, L or N plugs), which means that if a type D plug is pulled halfway out, its prongs are still connected to the socket! Little children run the risk of electrocuting themselves when pulling such a plug out and putting their fingers around it. Type D outlets are not recessed into the wall, so they do not provide any protection from touching the live pins either. 

[The Type M plug] the Indian type D plug, but its pins are much larger. Type M is a 15 amp plug, which has three round prongs that form a triangle. The central earth pin is 28.6 mm long and has a diameter of 8.7 mm. The 7.1 mm line and neutral pins are 18.6 mm long, on centres spaced 25.4 mm apart. The centre-to-centre distance between the grounding pin and the middle of the imaginary line connecting the two power pins is 28.6 mm. 

So I got out my ruler and decided to go ahead and measure my wall socket to see which plug type it was. First I measured the holes. My earth pin had a diameter of 8.7 mm and my live and neutral pins had a diameter of 7.1 mm. I thought that was it! I'd determined that my plug was of Type M! But there was a little unexpected twist! I then measured the spacing between the centres of the live and neutral pins just for fun and found that it was 19.1 mm! This thoroughly confused me. Here was a wall socket that had the pin diameters of a Type M socket but had the pin spacings of a Type D socket! I was unsure what to do! What I wanted to know was the current rating of the wall socket. If the socket had the current rating of Type M then it can supply up to 15A and I can safely run my kettle from it. However, if the socket had the current rating of Type D then it could only supply 5A and I would risk setting something on fire.

So I dived back into the internet and dug deeper. The Bureau of Indian Standards (BIS) is the organization that keeps track of the standards for all the stuff in India and I found that the code for the electrical plug standards is "IS1293". Weird.
So I dug up the pdf of that standard and started reading through it. After skimming through the material at high speed I found what I was looking for on page 83 of that document. The page had actual measurements of the wall sockets. They did not have a plug type with the weird combination of measurements that I measured. So I decided to think about it a bit. Obviously, Type M plugs which are 25.4 mm apart won't fit into this socket that I have even if the pin diameter matches. Since the socket pin spacing was 19.1 mm I assume/deduce that it was not meant to supply power to devices with Type M plugs. So from that page on the standards, this wall socket that I have must either supply 6A or 10A. Since both those values are below the rated 13A for my electric kettle, I think that I should not use it at the moment. I think I'll ask some people in the college about the actual current ratings of the plugs in my room but for now, no kettle.

TL;DR: Dammit! I can't use my kettle!

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