It all depends on priory, number affected etc, however for a standard domestic without any extra special circumstances, the assumption is that domestic fridges/freezers can keep temperature for 24 hours if not opened, so within this time I'd imagine.
Putting a 3-pin plug on my boiler.
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It all depends on priory, number affected etc, however for a standard domestic without any extra special circumstances, the assumption is that domestic fridges/freezers can keep temperature for 24 hours if not opened, so within this time I'd imagine.
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Same here - as I said, I think it must have been because Mr Murphy noticed that I invested in a small genny and associated wiring in the house around that time
Kind Regards, John
Freezers are presumably only a fairly small part of the equation. Complete loss of heating and, for a substantial proportion of consumers, complete loss of any means of cooking are factors which could impact on life and health, particularly when weather is very cold, and more particularly in relation to 'vulnerable' individuals.
Rules about compensation payments may also impact on the speed of restoring some sort of supply
Kind Regards, John
1) Don't ever lend it to anybody - that will trigger a power cut for you.
2) Do you find the voltage regulation and waveform OK?
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Yep, I've already worked out that one - Mr Murphy is very cunning! I also fire it up fairly regularly - since otherwise Mr M would probably ensure that it didn't work if/when it was needed 'in anger'!
Fine for the main purposes it's intended for (CH system and lighting) - but I've also run IT equipment off it (in tests) without any apparent problem. I did include an over-voltage breaker in the circuit, but that's probably being over-cautious!
Kind Regards, John
No need for the microwave (I have LPG cooking), so I wouldn't know. I have run a TV off it OK (again, only in tests - 'in anger' opportunities are so rare these days). I don't really see why there should be a problem with any load which was within its capabilities - voltage regulation seems pretty good (and most electronic equipment has SMTPs with wide input voltage range) and I don't see that waveform is likely to be an issue.
Kind Regards, John
You missed out hot water as well. Now combi boilers are the default choice (or infliction) for so many - no power also means no hot water either. For those with a hot water cylinder, you still get enough hot water to wash hands for a while - and even a few short showers.
For many, a UPS on the boiler would be sufficient to keep it running - the load isn't all that much.
But I too have a petrol genny (3kVA) if needed
I know from experience (used it at work a few times - keeps the petrol fresh(er)) it'll run 2kW of IT gear - though it struggles when the UPS tries to recharge it's batteries at the same time. So there can be an element of shutting down part of the load initially.Indeed. I suppose I was thinking of that as part of "complete loss of heating".
Do you mean to run a combi to the extent of being able to heat water? If so, you're probably right. As for pumped CH systems, uinless it were a pretty massive UPS, I wouldn't think it would run the pump(s) for very long at all, would it?
If the equipment itself is using most of the available power, I suppose that makes sense - but I wouldn't think that the charging of (modest sized) UPS batteries would, per se, represent much of a demand on the LV supply.But I too have a petrol genny (3kVA) if needed
Kind Regards, John
Well it depends on "a lot" I suppose. The manual for our boilers states 150W, a UPS we've sold a few of at work has a nominal runtime of 116 minutes at 150W load.
So you could run the system continuously for a while, then run the genny for a bit, rinse and repeat. Or, you could just run the heating for 5 minutes every 15 or so - warm the rads up and then turn the heating off. Better than no heating at all !
But it's not about how massive the UPS is, it's about how much battery capacity it has.
Part of the problem is that when you've 2kW of load, and the UPS dumps it onto the genny, then the genny output droops - that was the first problem we had and needed to change settings on the UPS to be less sensitive to mains voltage fluctuations. Then, if the load has been on battery for a while, the UPS can take a fair bit extra (I've seen as much as 50% of it's rating during testing on a couple of larger units) for charging batteries - 2kW + 50% is going to fully load a 3kVA genny. I haven't actually tested, but I think most of the models I've worked with fire up the charger immediately the mains comes back - so the genny has to instantly pick up as much as 150% of the supplied load.If the equipment itself is using most of the available power, I suppose that makes sense - but I wouldn't think that the charging of (modest sized) UPS batteries would, per se, represent much of a demand on the LV supply.But I too have a petrol genny (3kVA) if needed
So it can be worth shedding a bit of load (turn off a server or 2), transferring to genny, letting the batteries recharge for a few minutes (the charge current soon drops off), and then adding the loads back.
While we'll we're getting somewhat off topic, most of the UPS manufacturers recommend massively oversized gennys. Ie, if you have (say) a 3kVA UPS, they'll suggest anything up to 10kVA as a minimum genny rating to feed it ! Though to be fair, the genny manufacturers say the same - for the reasons I've described, it can be "tricky" getting an IT load started up/transferred to a genny that's not got a good bit larger than the load.
They also similarly overspec the minimum mains supply needed.
At work we have a supply with 63A fuse by the meter. As a result, that means we have to consider not just our normal load, but also the result of recovering from a power cut - it would be "a bit annoying" if we managed to survive a power cut, only to blow the supply fuse shortly after the power comes back on.
Discussions with manufacturers regarding the possibility of limiting charging current to keep within supply limits, or to take the charger supply from a separate input, gets the response "wrong supply" - usually adding "and we won't provide any support if you don't follow that recommendation". For the 16kVA unit we have, they state a minimum of 100A supply regardless of configuration or actual load - we currently have 7kW of load, on a unit with 12vKA of power modules installed.
Something there doesn't seem to add up. Assuming we're talking 12V batteries, then, forgetting inefficiencies, 1kW of additional power to charge them would imply a total charging current of about 83A - and I wouldn't have thought that a 'mere 2kW worth' of UPS would have battery(ies) which could tolerate charging currents remotely that high. What am I missing?
Kind Regards, John
Only the very smallest UPSs have 12V batteries.
And in any case, the same argument against high charge rates would apply to discharge rates.
The 3kVA unit at a customer I've mentioned above site uses 48V battery packs. That particular unit has additional packs* added, so it has a total of 6 sets of 4x12V batteries in parallel. Each individual battery is 12V 7Ah - so that's a total of 42Ah @ 48V.
So if you fed 1kW into them, that's around 3.5A per battery string - so not so unreasonable. Under discharge it's going to be in the region of 8A per string - so not too hard on the batteries.
At work the system is nominally 120V (so 138V float), with each battery pack having 10x12V7Ah batteries in series. At the moment there's only 5 packs connected (but I've got a stack of new cells for some empty packs). With 7kW load, that's around 12A/string - probably more for some since some of the batteries are "tired" and won't give their fair share.
The 1500VA unit I linked to earlier has 2off 12V 17Ah batteries.
* Going even further off-topic, battery capacity is highly influenced by discharge rate. For the 3kVA unit above, it's got 3x the batteries for about 5x the runtime. If you look at manufacturer's spec sheets they normally give discharge curves (time vs voltage) for different discharge rates.
For an example of spec sheets, see this
http://www.csb-battery.com/upfiles/dow01404182647.pdf
It's the size of battery the above mentioned units use. Notice how they give both constant current and constant power. In an application like this, as the terminal voltage drops, the current increases for constant power to the load.
EDIT: And discharge rates of up to 100A allowed
The aim since 1st April is to restore supplies within 12 hours, either by repair/reroute or generator. Though in some cases the generator may not allow full capacity.
And if you do put a genny in, you get the locals complaining about the noise.
Some friends were on a genny for a few days a few weeks back and half the village were moaning. I imagine they'd moan even more if the genny weren't there
Some friends were on a genny for a few days a few weeks back and half the village were moaning. I imagine they'd moan even more if the genny weren't there
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