WTF is going on with the 180-190V brownout though?
OK, my shelf rig uses a different approach to mackminer's, and he's pulling 8.7 GH/s against my 7.4 GH/s (according to arsbitcoin, oddly enough we're both using the same pool unless there are two mackminers...) but I have ONE cable running into my triple-board triple-PSU rig.
My PSUs are cheap, for all the usual reasons. Quality manufacturers, but anything over 1000W gets really expensive really quickly. So Shelf 1 runs two Cooler Master Silent Pros (1000W, 800W) and a Corsair 850W unit. None of the three PSUs individually pull more from the wall than their rated output, and since the inefficiency is on the conversion side, 10% inefficiency means the safe rated 1000W pull from the biggest PSU would pull 1,111W from the wall. That'd be OK. But none of the rigs do.
All three go into one power cable, which has the UK equivalent of a Kill-A-Watt stuck on the end. When ArsBitcoin isn't being DDoS'd, and the shelf rig can kick arse, that 'kill-a-watt-alike' shows between 2200 and 2300W.
Given the room has a single dual-socket outlet, each rated at max 13A at nominal 240V, I'm not 100% comfortable about the current draw on those cables. There's a 13A extension cord (20M) between the socket and the rig too!!! Yes, the cable gets mildly warm, but not as hot as when I tried to run the same sort of rig on a 10A home-made extension cable - the wire was too hot to touch and the female socket nearly caught fire. I'm using solid-conductor ring-main stuff now...
But even with the idiotic 10A extension, the smoking sockets and the floppy, melting wires... the voltage NEVER dropped lower than 220V. You'd expect a pretty hefty voltage drop from the resistance of the under-spec extension cable and the heating of the wire causing further resistance. But it wasn't much.
Mack... if your supply is showing 180-190V on a 240V main then either your 'kill-a-watt' is fucked or you need to get the circuit the miners are on looked at. Especially when you're investing in quality kit and 8 kW air conditioning units. Yes, the best quality PSUs are probably the only things that can cope with brownouts like that, but what happens when the input voltage drops? Well, the input current draw is increased to provide the same power. The PSU may be built to ramp up the amperage from your '240V' supply which has suddenly dropped to 180V... but that's the voltage dropped by a quarter. Hence to maintain the same power, the PSU will draw 4/3 more amps of current (sorry if maths is duff but I'm a bit wasted).
Going back to my situation, with around 10A steady on a 13A mains line, I'm in the safe zone. If my 240V supply dropped to 180V, then the PSUs would pull 10 * 4 / 3 = 13.333A. Hopefully the fuse in the extension cord would pop and 'boom' my miners would stop. Hopefully the PSUs would cope with a sudden loss of power and not fuck up all my GPUs.
But 13.3A on a domestic circuit is above spec. If you're really seeing 180V input and you're doing the same sort of thing as me, then you're either popping fuses every time it happens, or your kill-a-watt is fecked, or you're reading it wrong. That sort of voltage brownout would make your PSUs work like bastards to deliver the power your rigs are pulling. Fuck knows if the air-con could even cope with a voltage drop like that.
Where are you reading those figures from? I've got cheap (£10) Maplin own-brand 'kill-a-watt' devices and I've not had a duff one. I'm seriously taking the piss with the electrical setup in my 200 yr old UK house (the consumer unit still has Bakelite fuses with hand-coiled wire in them, for example) and I've built my own ring main for the office... I'm eating a LOT of power and *some* cables are getting warm. But I've *never* seen 180V at the outlet. The only time I have problems is when the knackered battery in my UPS decides to try to kill my Mac Pro and all the big screens - even a random spike like *that* doesn't affect the miner rigs - every one on a surge protector and kill-a-watt, either a power strip version or an individual socket.
OK, I've had enough booze, TL;DR - when your volts go down, a regulated PSU will pull more amps. If you're currently (hehehe) pulling 10A on a domestic main, and your voltage drops from 240 to 180, then you WILL either blow a fuse, trip a breaker, blow a PSU, blow an entire rig, or set fire to something. You've got me worried now - I'm checking the voltage on all my kill-a-watts.
I really find these power supplies confusing. I understand the basics of electricity and stuff, I don't really find psu's that interesting to go to the trouble of understanding them fully. I'm waiting for the electricity company to get back with their findings after measuring it for a week or so. I will read your post more carefully tomorrow when I have slept though because I am concerned about some of the things you have mentioned.
