Power Cuts/Generators yet again

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On Wed, 14 Jan 2004 21:05:38 +0000 (GMT), "Dave Liquorice"

Neither are trivial.

Many small gensets can be converted ~GBP100. Propane has a number of advantages, the bottles need to be kept warm as you will be using a vapour take off.
AJH
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On Thu, 15 Jan 2004 00:05:13 +0000, Andrew Heggie wrote:

Bang (or not..) goes that idea then.

Butane (blue) has a problem in the cold. Propane (orange) doesn't suffer the same, at least not at normal UK winter temperatures. I can't imagine that people with propane CH or cooking have no heating or cooking when it gets cold. The tanks/cylinders are frequently outside, unprotected. I've seen propane bottles with an inch or more of frost around them, handy for indicating how much gas is left. B-)
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On Thu, 15 Jan 2004 22:18:38 +0000 (GMT), "Dave Liquorice"

It does if the required rate of vapourisation exceeds the heat transfer from the air through the bottle (including insulating ice layer), the latent heat of vapourisation simply cools the remaining propane below its boiling point. This is of course highly dependant on the size of the engine, if you are running at 2kW(e) then the heat draw will be around 10kW(t), nearly 2ltres/hour and comparable to a couple of biggish hobs. Increase this to 20kW(e) and I am fairly confident you will need a liquid feed and a heated vapouriser.
AJH
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On Fri, 16 Jan 2004 10:18:04 +0000, Andrew Heggie wrote:

-44C blooming cold... Even on a very cold night for the UK say -10C you still have 30+C of temperature gradient to push heat into the cylinder.

Very much so but I think for the sizes we are talking, max of 5kVA genset, running at an average of 20% capacity I doubt it is of practical concern.
I choose 1kVA as an average with care, that is pretty much what our daily average load is. Though that includes when we are all asleep, so I guess the "active" average load might be as much as 2kVA.
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On Fri, 16 Jan 2004 16:47:55 +0000 (GMT), "Dave Liquorice"

My daughter tells me it is -22C at the moment :-)

I agree, which is why I posted it is about the same as a couple of hobs full on, bear in mine it becomes more of a problem as the bottles empty.
Slightly related is that it is, allegedly, known for lpg equipped vehicles with no antifreeze in the coolant to freeze their vapourisers before the thermostat opens, bringing the vehicle to a halt.

This accords with what I found with our genset, though this is not domestic use.
I think you are mixing the terminology a bit here, OK the genset needs to know the kVA, because if either current or Volts exceed the rating of the machine something gives (after allowing a safety margin) but it is the kW draw that determines the heat load of the engine ( and indeed whether it stalls). So you may have a 10kVA genset capable of supplying 7.5kW(e) continuously but working on average at 2kW(e). In point of fact this is what makes permanent magnet alternators and inverters so interesting to me for home use (once demand shifts from 90%heat:10%electricty to something nearer 70%heat:30% electricity)
AJH
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On Fri, 16 Jan 2004 20:03:56 +0000, Andrew Heggie wrote:

But not in the UK, Canada?

Not quite sure how the automatic change over valves function, I'd assume on cylinder pressure when it gets "too low" the valve switches to the other cylinder. I doubt they switch back though, which would allow you to toggle between cylinders. As one became too cold to vapourise the valve would switch to the other, allowing the cold one to warm up. When the second got too cold the valve would switch back to, the now warm, orginal cylinder. B-)

Just a bit... B-)
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On Fri, 16 Jan 2004 21:04:51 +0000 (GMT), "Dave Liquorice"

Boston Mass.

OK I had not considered this as a possibility, in fact I did not know such things existed.
AJH
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On Fri, 16 Jan 2004 21:04:51 +0000 (GMT), "Dave Liquorice"

AFAIK they don't switch back.
One method (I've seen it both in books, and on a building site feeding big heaters) is to run several tanks parallel. This reduces the amount of vapor each tank has to produce, while the surface increases.
Thomas Prufer
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We've been cooking on bottle propane for 11 years without problems, and the bottles live outside, unprotected.
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The last time we were off for 96 hours.
24/7 kept telling us they were very busy and they'd get to us, but when we got really pissed off and started calling every few hours and the engineers finally came, they said they'd only just heard about us. Next time, I shall call every 60 minutes until the power is reconnected.
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"Huge" wrote | The last time we were off for 96 hours. | 24/7 kept telling us ...
Does their company name constitute false advertising?
Owain
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Nah. Just tells you how long you can expect to ring them for without getting a useful response...
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IMNHO, yes.
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Huge wrote:

Just had a 30 min outage here (Spalding), UPS barely troubled running Tivo, DTT decoder, PC, router and 1 CFL lightbulb. Gas hob carried on through with no disturbance, unlike my parents' which cuts the flame back when the leccy goes off. Heating went off but that's no biggie, there's always a few more layers of clothing that can go on before I start feeling cold.
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The last time I saw these at Screwfix, they were priced at 299. If you want I'll sell you the same model (850W) for 200. I'll pocket the 150 profit if you don't mind.
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