apparently in Canada, at one point, freezers had a solenoid lock (which could be overriden manually) to stop you opening the lid/door if there was a power cut.
Assume that the power cut may be more than an hour or so and I would really like to eat.....
I have worked out that in a prolonged power cut I can stay warm with the log burner and even cook on it.
Light from candles or torches.
The freezer is the one thing which has a major time limit. Three days is usually quoted for a modern freezer if you don't open the door. So that is the risk that I am addressing.
"small generator" How big is small? The small 750 W two stroke jobbies can struggle with freezers/fridges as they don't have enough welly to start the compressor motor.
Define "short". The DNO's are pretty good at bringing people back on supply by altering the distribution switching. The chances are a power cut will only be an hour or two. If you just happen to be in the section with the fault it might take a while longer but probably less than 12 hours. Strangely 12 hours off supply is when most compensation kicks in...
A modern freezer, even opened once or twice to quickly grab something, won't be particulary bothered for 12 hours, maybe longer.
Are they heat/fire proof? How do the exhaust gases get out? Good flow of cooling air in? They all look nice covers for a plain rectangular box. But when running you'll have the CEE output connector sticking out somwhere...
Trying to remember what I did, if anything, the last time I needed the genset and it was raining. I suspect it wasn't much more than a bit of weighted down poly sheet covering the top and down the exposed side over the connector/control panel and down the exposed end. Oh look there's the rountuit to build a generator cover/shelter. B-)
As folk seem to be being silly in parts of this thread. I am going back a way here, but I distinctly recall the up and down vents in a generator cover to stop the water getting in while air still did. It did deaden some of the sound, but maybe that is going to be the issue with such devices, what lets air in, lets sound out and you can pad the innards as much as you like, but there is always a trade off. These generators were running lights in a factory after it had partly burned down, so nothing very fussy on cps etc. Brian
If you want to reduce noise, fitting a baffle box to the exhaust, and surrounding the genny with panels similar to those used by acoustic fencing, should help somewhat.
For a short powercut you really just need to keep the freezer door closed and then put it on superfreeze for a bit when power is restored.
After the first day it is worth rigging up local power. Most power cuts are usually shorter than that unless something goes very badly wrong.
I keep mine under a cardboard box when not in use and operating just inside the garage door to keep the rain off (door open). If I didn't have a convenient garage then it would be up against the house wall under a piece of rigid PVC foam plastic sheet to keep the rain off.
I think mine claims to be weatherproof but we get a lot of bad weather around here usually at about the same time as the power fails.
about 6 years ago there was a cable fault in out road. An emergency generator was brought in and coupled up to our house at about 1am. had it for 4 days.
I think someone (on Youtube) just positioned sheets of wood sloping towards the generator (I can't remember if it had a top to it) and that both allowed it to breath but drastically reduced the sound levels.
I think people tend to makes drop-over lids with baffles out of dense material (ply / chipboard) and with a mains powered input fan at the inlet (powered by the genny), ensuring the air is kept moving in the right direction.
I've always hankered after one of the Honda suitcase genny's but can't justify it's cost for it's use (I have a Honda powered 3KVA 'open frame' genny I've only used a couple of times).
When the electricity company were doing some work on high voltage feeds to various substations in the area, they brought in loads of huge generators (they moved them from one village to another as the work progressed) and fed groups of houses from the genny. The constant throbbing of the diesel engines, day and night, was a real problem. I think our power was on local feed for about a week.
I've wondered about getting a UPS for electronic equipment that reboots at the slightest interruption. We went through a phase last year of getting brief (< 1 second) power breaks every few days - or maybe a sequence of them every 30 seconds or so. The electricity company had not been going round pruning overhanging trees near HV lines, and when one touched a wire (eg in stronger than normal wind) a circuit breaker would trip and reconnect.
How good are UPSs at providing mains that is sufficiently glitch-free, when switching to and from battery, that computers don't notice? The only UPS I've tried to use was one that my wife bought at the same time as her big PC, but we never got round to trying for a couple of years - and when we did, the battery would not provide mains, even with negligible load, for more than about a second. The battery was either dead on arrival or else had failed through lack of use (maybe through being stored with no charge). So I've never seen how seamless the changeover is from mains to battery. I presume they are more sophisticated than a relay, where contact bounce, even if mains cycles match, may cause problems. Do most UPSs run the inverter all the time (without taking power from it) so it is ready at a moment's notice, locked to mains frequency and phase for instant switchover. I presume the big problem with a UPS is when the supply is switched back to mains, because the inverter will have been running off a free-running oscillator that will be a different frequency so there will be a discontinuity at the point of switchover. Or do UPSs stay on battery after the mains has returned, tweaking the local frequency and phase gradually until they are locked to mains and then switch without a discontinuity.
This was a cheap consumer 700 VA APC UPS, so probably one that switched over, rather than one that was always running off battery and inverter, with the battery kept charged by the mains but with no direct connection from input to output.
That is a good point even a 1.5kW unit slows briefly when the freezer motor comes on due to the very high surge current. A smaller unit might well cutout to protect itself from a perceived overload conditions.
The load presented by the compressor motor from a standing start looks very much like a dead short until it spins up.
As you say, most consumer UPSs only switch on the inverter when power is lost. In practice most PC power supplies seem to cope without catastrophic glitches on their output when switching on and off. I suspect there are enough capacitors on the DC outputs to maintain the voltage for the tens of milliseconds the mains supply is disrupted. There are actually standards for this which good quality PSUs will meet.
Also as you say, an SLA UPS battery will die if left to self-discharge for a year or two, so you never had a fair test.
I'd want a waterproof lid, to prevent rain dripping down off the fuel tank/cover plates into the alternator or wiring, some of which is enclosed but not by anything I'd consider water proof. As part of guaranteeing a mild, storm free winter I ought to make something... I've off cuts of onduline that would do for the top. Yes I know not exactly fire proof but it'd be well away from the hot bit's like exhuast.
Yeah, I'd really like a 2 kVA one. I've used then for work on ocassion, they are wonderfully quiet, light (one arm carry) and produce "proper" mains. But I'll have to live with my fing noisey, heavy (as in glued to the ground), diesel set. Being diesel I can at least run it on red, instead of paying nearly 60p/l of road fuel duty.
Here's a low-cost alternative to keeping your freezer cold for short periods. without running a genny.
The science bit:
Water ice has a comparatively massive Latent Heat of Melting, at 334kJ/kg, which can be used to hold the freezer contents at its melting temperature until all the ice has melted.
Use this Latent Heat of Melting by employing a liquid that is frozen at the normal freezer internal temperature, say -18degC, but which melts at perhaps -15 degC, using that Latent Heat of Melting to keep the freezer contents at that temperature.
The technology bit:
A NaCl salt solution of 220g/litre freezes at -15degC, and a mixture of propylene glycol and water in a ratio of 30/70 glycol/water freezes at
-16.6 degC. Both of these would use that lovely ice-to-water transition to keep the freezer at their respective temperatures until it has all liquefied.
In practice:
4 x 500ml bottles of NaCl solution as described will demand 668kJ to fully melt. There are 3600 kJ in a kWh, so if one's freezer uses a typical
1kWh/day, the 668kJ would be equivalent to running it for 5.4 hours. Use more bottles for a large freezer.
Some points to note:
- Don't use ethylene glycol for this application - Allow for expansion as the solution initially freezes. - Water in ice form has a specific heat capacity of only 2.1 kJ/kgK.
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