A shocking surprise after my UPS failed

So in my cellar I have a Linux server… and a NAS running FreeNAS… and a managed gigabit swich… and a router running pfSense… and maybe some PoE gear feeding power to an ADSL modem and a wifi access point elsewhere in the house. Yeah, I like complicated, complicated is cool.

Losing data because the power goes out isn’t cool. But having a UPS and the NUT UPS tools on my network is really cool – power goes out, the UPS starts screaming at me and all the hardware gets told and shuts down in a tidy manner. Very nice.

What isn’t nice is when the UPS appears to be faulty – randomly deciding the mains has gone off, even when it hasn’t, which is what it did at 1:55am this morning

Aug 4 01:51:57 cex upsmon[1996]: UPS ups@chi on battery
Aug 4 01:55:22 cex upsmon[1996]: UPS ups@chi battery is low
Aug 4 01:55:27 cex upsmon[1996]: UPS ups@chi: forced shutdown in progress

Nice to know the system works, but would have been nicer if it only shut down when the actual mains had actually gone off, for real (like it did the other day at about 3pm). Seems I also need a better UPS, 4 minutes of power is a bit … short.

So anyway, I woke up this morning and realised I had No Internet and after entering my underground data centre I was greeted with that eerie silence computers-that-are-supposed-to-be-on-but-aren’t make. Muttering at my crappy UPS I stuck my arm across the first machine to turn it on and received a bit of a zap.

It was like this, only not as bad.

Nothing too bad, kind of like licking a 9v battery, but on my bare arm (which is neither a tongue nor damp). And this is where things got weird. I got my multimeter, stuck it on AC voltage and put one of the probes onto the metal casing, the other probe wasn’t touching anything. The meter read 8VAC… Bit weird, so I took hold of the free probe and tapped it with my finger… the meter then read 115VAC.

Yes America, the voltage between my PC case and my finger read the same as your wall voltage. And here I was, stood barefoot on a slightly damp stone floor going “hmm this is indeed strange, seems there’s 115V going down my finger”. OK so the actual current must have been tiny since I wasn’t lying on the stone floor gently convulsing, but still, clearly we had a bit of a ground fault.

And yes, the sockets in this house are protected by an RCD. It didn’t trip, so I guess the current must have been really small and it was only the relatively high voltage that made me notice it. I have an 88 amp-hour 12V DC battery and can hold its terminals all day without feeling anything. Volts thrill, amps kill, but you need both together to grill.

After some probing with the continuity tester I realised there was no continuity between the wall socket’s earth pin and that PC I had been touching. Nor was there any continuity between the casing of the PC under it and this PC. A bit more probing with a multimeter showed me there was no continuity between the earth pins on each end of that PC’s power cable.

So yeah, I’d been drawing about 60W of 240V quite happily without an earth connection, gradually letting the casing charge up. No wonder the UPS had been going strange – the ground pin of the USB connector was probably sending this unwanted current into the UPS’s monitor and control electronics.

I’ve removed the offending power cable and cut it in half. The bit with the IEC plug has proper continuity, the bit with the plug on doesn’t. Later I’ll cut the plug open and see if there’s anything interesting in it.

This would also explain a few strange things I’ve noticed in the past. The UPS would only seem to go crazy if its USB management cable was attached. My old server would freak out whenever I plugged the UPS in – telling me there was ESD on the USB port. At one time I had a USB SATA enclosure that uses an IEC mains cable for its PSU. This SATA enclosure always seemed a bit odd, in that its metal casing always felt “strange” (if you’re one of those people who can touch an aluminium Macbook and feel a weird ‘bumpiness’, you’ll understand). I guess the common thing between them all was this mains cable.

Why did I keep using a clearly faulty mains cable? Well it was a convenient short length – it was only 75cm long, ideal for keeping wiring tidy. And it was a cable with moulded plugs that contain all the required UK safety logos and numbers.

Broken shower pull switch

After using the shower last week I tried to turn the power off using the ceiling mounted pull cord switch but found the switch didn’t click like usual and seemed stuck. For a few days the switch had been quite stiff to pull, but still seemed to work OK. However, as you can see from the image above, something went very wrong with it. The last time I pulled the cord the power turned off, but the switch got stuck and was quite hot to the touch. I also noticed the crack on the casing and the slight brown mark too.

Today the electrician came to replace the switch and after he’d left I took some photos. Click on the links below to see them

Burnt out shower pull switch showing a crack in the plastic casing and a small brown mark.
Internal shot of the burnt out shower pull switch, showing extensive burning of the plastic.
Closeup of the terminals inside the burnt shower pull switch.

After taking the switch apart it became more clear why the switch had failed. The switch contacts hadn’t shorted together and most of the burnt plastic was localised around the screw terminal for the live wire coming from the fusebox. The electrician also told me that because the shower wires are quite thick it’s difficult to make them all fit into the terminal holes and tighten the retaining screw enough. So rather than the switch failing, which would have welded the contacts together, tripping the circuit breaker, the terminal must have been loose making the electricity arc inside the switch.

According to the British Gas energy meter I own, the shower draws around 10KW of energy when in use (it’s winter, we have the heat setting turned up quite high). While the switches are made from very thick thermosetting plastic and large pieces of copper I feel there is a design fault because this is the second switch I’ve known to fail in this way, and the electrician said it was fairly common for this to happen also.

Next time the electrician visits, I’ll have to ask him what the strange switch at the top of the stairs is for.

CFL bulbs behaving oddly

Like most people, my house is full of energy saving compact flourescent light bulbs. Like most people I bought the cheapest I could find – 50p each cheap from Tesco. Those long 21w CFL bulbs that are about six inches long.

I’ve just been sat in the dark staring at the one in my bedroom ceiling light fitting. Why? Well it was flashing at me. Only the switch is off and the bulb has been off for at least an hour.

It randomly, but every five seconds or so gives off a brief flash that either lights the whole bulb or just the end – with the power off.

So, apart from potential demons in the loft chewing on the wiring I am left with an explanation equally strange. Earlier this evening there was a huge rain storm and some lightning. It is still raining but the lightning has stopped. All I can think is that the hous wirin is acting like an antenna and picking up enough stray energy to briefly energise the bulb. CFL bulbs are odd like that, you can light them using static electricity, microwave ovens or those cool plasma domes.

It’s cool, but also a bit freaky when your bedroom light starts flashing, it’s a bit X-Files.

Weird things in my house

Moving into new houses is fun, they usually have all sorts of odd quirks and this one is no exception. It features crazy heating controller which has no manual and an alarm box that lacks any explanation of what the lights on it mean. Next to the electric box a bright yellow sticker warns people that both versions of BS7671 are in use and to be very careful when wiring things up.

Those are normal things and to be expected, but we have this odd thing screwed to the wall at the top of the stairs…

What is it?

January was very cold, and very dark

My gas usage

I have one of those British Gas EnergySmart tariffs – the one where you do the meter reading in return for more accurate bills, the idea being instead of them guessing your usage for six months then suddenly going “oh! it’s all wrong, give us an extra 20 quid a month please” you put the meter readers out of business and type the numbers into their website for them.

As an added incentive you get a little energy meter which after five minutes I duly took apart to see what was in it. They also have a section on their website to see your energy usage during the year, and a comparison to last year. It seems from my graphs I’m using less gas than last year, probably because I don’t use the timer any more and just switch it on manually, but I use more electricity. I probably use more electricity because I have a few electric heaters in my bedroom to keep the mould away.

My electricity usage

So, from these graphs you can see several things – Compared to summer, it’s bloody cold since all I use gas for is heating and cooking, and I certainly don’t eat more food in winter. And compared to last year I have used double the electricity somehow, probably also due to it being so damn cold I had to buy electric heaters. Really, it was -4.5c outside when I woke up this morning and a crisp 13c in my bedroom. It’s a good job I was underneath four duvets with a pair of thermals and thick socks on, curled around a hot water bottle.

Not to worry, come summer I’ll be sweating to death with all the windows open.

Motor bicycle

So Amy’s got a new job, and due to various health reasons she’s getting an electric bike so she can get to work. The bike has a 15 mile range from one charge, work is two miles away.

Since the bike is electric, it’s just a bike – no road tax or MOT etc needed.

But what’d happen if we strapped a petrol generator to it to charge the battery while it’s moving? Would it still be an electric vehicle, or would it be a petrol powered one?

Since if it remains an electric vehicle, I’m going to remove the engine from my car, replace it with electric motors, fill my boot with batteries and use the petrol engine to charge the batteries while the car is running.

… it’s how a lot of trains work, so it’s not as daft as it sounds.

British Gas EnergySmart Energy Meter teardown

The British Gas EnergySmart energy meter
The British Gas EnergySmart energy meter

This box is known as the “British Gas EnergySmart” energy meter, and is available free to British Gas customers who sign up to their EnergySmart pricing plan. It’s called EnergySmart because instead of paying someone to come and read my meter, it’s now my job to crawl behind the telly every month. If I forget I get an estimated bill, which is bad.

See, that’s smart that is.

What’s even smarter is taking one of these things apart 🙂 Like the nice man on the EEV Blog says – “Don’t turn it on, take it apart!”. Continue reading British Gas EnergySmart Energy Meter teardown

A week with no laptop

Having returned from an overnight stay at Amy’s I took out my laptop and noticed the charger wasn’t in my bag, and then realised with some irritation that I’ve left it plugged in at her house. This wouldn’t normally be a problem since I could just collect it next weekend, but I’m going away to America for two weeks, and was planning on taking my laptop with me.

Fortunately my cousin, who is also going has a Macbook and I can share his charger. His Mac’s battery is dead, so won’t work without being plugged in, but mine lasts a few hours on battery so will be fine. My laptop currently has 40 minutes of charge left, which should be enough to sync it with my network before I leave and update my iPod.

This week will now turn into an experiment to see how well my iPod Touch and T-Mobile G1 cope as laptop replacements. Sure, I have my real PC upstairs in my office, but I can’t sit at that and watch TV. I’ve just installed a few games and apps onto my iPod to keep me amused on the flight too.