Power Cuts/Generators yet again

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Toby wrote:

What on earth motivates manufacturers to design in this particular unhelpful feature? I can't think of a good technical reason, can anyone else?
Bob
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Bob Minchin wrote:

Exactly. And it was the (not so) Smart-UPS about to cause trouble in a call centre with an almost expired call processor a couple of years back. Looks like the budget Back-UPS CS (Hmm wonder what those initials stand for) would work from cold.
Thanks Stefek for the cold start keyword, knew there was some featurette. Just what sort of power would be need to keep the CH going for a couple of hours? I would assume it's less than 100w flat out.
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In an earlier contribution to this discussion,
Just what sort of power would be need to keep the CH

Measurements on my system suggest about 120 watts - pump 70, boiler 40 and 3-port valve actuator 10. With a 100% efficient inverter, you'd need 10 amps at 12v to support this. A (say) 70 amp-hour leisure battery should keep you going for (maybe) 5 hours continuous. In reality, the boiler and pump will keep going on and off on their stats - so the battery will last longer than this.
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And you can always run a lead in from your car to top it up::::
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In an earlier contribution to this discussion,

Or go for a ride in the car with the heater on to keep warm. May be more efficient!
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On Sat, 10 Jan 2004 15:31:19 -0000, Toby wrote:

You can, I've done it with mine (SmartUPS 700i). However APC don't recomend this cold start for some reason.
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On Sat, 10 Jan 2004 22:13:09 +0000 (GMT), "Dave Liquorice"

Perhaps it's a matter of the application. According to their configurator, if you run this one at 300W (420VA), it will go for 10 minutes. In terms of a PC, this is probably not long enough to do much work if you've started from cold.
One of the common philosophies of UPSes is to give time to perform an orderly shutdown when the power fails. APC provide software to do all this across multiple machines for example.
Perhaps this is more of a customer expectation setting exercise on APC's part. .andy
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If I add a 'permanent' charger then effectively I've got an UPS. With a capacity of approx 0.5 kwh. I don't know what you'd expect to pay for one ready made, but my costs are *well* under 50 quid so far, given that most of the bits are either secondhand or new via Ebay.
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That Vellerman inverter is suspect though. I've never liked their kits.
I use Nikkai quasi-sine inverters with the drop-out set to 10.5V. This allows me to get good running time without worrying about being unable to charge the battery. The charger itself becomes very important if you want to alternate between rapid charging and maintenance. You can use the cheap Halfords iron-sensed units. But they are hopeless at rapid charging and I wouldn't be happy with leaving one on 24/7.
I use a Sterling switch-mode charger which can deliver 60A maximum but has microprocessor control of output in four stages, dropping off to a maintenance charge. I'm happy leaving that on 24/7 but it's a far more expensive solution (260) than you are thinking of.
A s/h car battery isn't going to last long under load, but a lot depends on what you are using it for and how frequently. I'm using battery backup as a replacement for mains with 400Ah of battery storage and I'm vaguely thinking of adding another 600Ah and a 1kW wind turbine. At present it is set up to let me make efficient use of a 2600 VA generator. When I run the generator I charge the battery bank. That lets me use silent power at night for lighting.
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Well, I do like them. They usually do what they say on the box. And in the case of this invertor - it's fine, and looks to me well designed. Of course it's perfectly built. ;-) I didn't use their own transformer (an 'extra') which is about double the cost of a new suitable toroid from Maplin. I actually found a suitable one on Ebay for half the Maplin price. And Maplin are quite competitive for some mains toroidal transformers.
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That's about what they cost ready made, UPSs have become incredibly cheap now.
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On 12 Jan 2004 09:06:24 GMT, snipped-for-privacy@isbd.co.uk wrote:

True but with an up time measured in minutes delivering the 150W or so that a CH system takes... I've thought about getting a couple of big SLA's for my APC UPS to extend the uptime but the 700VA rating isn't really enough for my current load so I really need a bigger or another UPS anyway...
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With that sort of capacity? I find that hard to believe - the battery alone would cost much more than that trade price.
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Batteries on a UPS are not up to the job. they give about 4 minutes operation at 150W on a 625VA UPS. They also die rahter quickly if they get run flat. An inverter with a traction battery is much more robust. I have an 800W inverter that runs a normal domestic lighting and CH load for over 10 hours from a traction battery.
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In an earlier contribution to this discussion,

Dave - I was very interested in your solution. Does your inverter produce a sine wave or a square wave output? If the latter, do your boiler electronics seem happy with it? Have you done anything to eliminate spikes? How is the CH supply earthed when powered by the inverter?
If you have read my earlier posts (I started this thread!) you will know that I am planning something similar with a generator - but not with any sort of automatic changeover.
Until a couple of days ago, my CH was fed by a FCU in the airing cupboard. There was a very short T&E cable going from the FCU into a 10-way junction box, into which the boiler, 3-port valve, room stat and cylinder stat are all connected. The pump (although also in the airing cupboard) is connected directly to the boiler - and controlled by its over-run stat. This means that the boiler needs a live connection in addition to neutral, earth and switched live.
It was thus relatively trivial to change the wiring in such a way that the whole thing is now powered from the boiler end rather than the the airing cupboard end of the cable which joins the two. I have now done this, and the whole thing is now powered from a 13A plug adjacent to the boiler. The utility room also houses a couple of freezers - which I wish to power in the event of a prolonged power cut.
The idea is that, when the power fails, I can put the generator in a suitable location (maybe in the conservatory - not sure yet) with a 4 or 6 way extension lead into which I can plug the heating, freezers plus some lighting. As stated earlier, I am looking at the Honda eu10i and eu20i generators as possible contenders. The smaller one (900 watts) appears adequate *unless* SWMBO decides she needs to use the microwave - in which case we shall need the 1600 watt model. Even so, forget electric kettles!
FWIW, I've just invested 20 in a plug-in volt/amp/watt meter from Machine Mart - which is proving useful in determining the consumption of various appliances. However, I suspect it doesn't show peak loads on switch-on. The 2 freezers take about 250watts each (only when their compressors are running, of course) and the heating takes a max of less than 150 watts - so with 900 watts I would still have some leaway for lighting. [Interestingly, the 3-port valve consumes about 7 watts even when nothing is running].
The things which I still need to bottom out are earthing and spike protection.
Clearly, when I unplug appliances from the mains, they are no longer earthed through the mains - even if the electricity board's earth remains intact during a power cut. The central heating pipes are sort-of earthed, by being bonded to a steel gas pipe which disappears underground. What else do I need to do? For example, do I need to connect the generator's earth to a spike in the ground? What about the generator's neutral (it's single phase, of course!) - does that need tying down, and if so, to what?
The generators in question both essentially generate DC and use inverter technology to produce AC. [I presume this is easier than generating AC since it doesn't require accurate speed control]. I have a concern - don't know whether it's real or not - that when, for example, a freezer turns on or off there could be spikes on the AC output and that these might be detrimental to the components on the boiler PCB [MkI Baxi Solo 70/4PF]. Does anyone have any comments about this, and any suggestions on what to do. For example, you can buy extension leads for computer use with built-in spike suppression. Would one of these help?
TIA.
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wrote:

I think the issue is more to do with matching power to load, a synchronous genset will be running at either 1500rpm or 3000rpm depending on the poles of the alternator, it is only optimally matched to the load at 75%ish of its max power. The inverter set can vary speed to match the load better. If this gains more in thermodynamic efficiency than the ~10% electrical losses of rectifier and inverter then fuel cost will be lower, also the engine life will be extended. From my experience of selecting a genset to match peak loads I found the average load was 1/5 of peak.
I suppose you could build much the same with an ex military battery charging genset, 24volt battery and a couple of inverters (1 near sine wave for sensitive equipment , 1 cheaper modified square wave for less fussy stuff) in parallel. The battery could be automotive as it would only handle peak loads or until the genset came up to speed. Float charge the battery and have the genset start using the same inputs either Dave P or yourself suggested. The Honda i series is neat though.
AJH
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On Sat, 10 Jan 2004 16:01:09 -0000, Set Square wrote:

Erm, exhaust fumes?

I'd look at the plate on the back of your uWave. It maight be a 600W or 800W on thefront but that is the RF power inside the box. Our 800W (category E) actually takes 1240W...
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which is about what he said isn't it ?
i.e. he'd need a bigger model
Nick
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On Sat, 10 Jan 2004 22:40:16 -0000, Nick Smith wrote:

Yes but probably not big enough. If 900W serves the demand without the uWave you only have 700W "surplus" with the bigger genny. As uWaves are only about 60% effcient from their RF rating even a 600W jobbie will draw 1000W...
More of a heads up than anything else, but an easy mistake to make. Not sure what sort of load a uWave presents either, I suspect very inductive.
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In an earlier contribution to this discussion,

Perhaps I should have made it clear that I wouldn't run the microwave at the *same time* as everything else. I would at least turn the freezers off for the relatively short time needed to operate the microwave.
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