Hello,

We had a power cut for three hours last night. I happened at the worst
possible time: just as we were getting cold, dark, and hungry.

We have oil fired central heating and it was frustrating that we had a
tank full of oil but could not use the CH because we had no power for
the boiler. This got me thinking that perhaps I could buy a cheap
inverter and run the boiler from a car battery.

The boiler instructions say it must be connected via a 5A FCU, but
240*5=1.2kW, so that's a bigger inverter than I had originally
thought.

Also connected to the FCU are the pump, valves, etc. IIRC the pump
uses about 40W. When I bought the valves, I didn't realise there were
different types, I just bought what was in the screwfix catalogue.
Unfortunately, they are spring operated so draw 6W all the time they
are on. I wish I had known about motorised on and off ones that only
draw current when switching. I will ask the boiler manufacturer, but
in the meantime, does anyone know how much current a modern oil-fired
condensing boiler draws? Surely it can't be a kilowatt? But then
motors have a surge when they are switched on, don't they, so I guess
the 5A fuse is to tolerate that?

It would be nice if I could use a (made-up number) 300W inverter with
momentary peak output of 1.2kW rather than have to pay for a
continuously rated 1.2kW inverter.

I read all the old posts on this group about inverters and generators
and see that a break before make changeover switch must be used to
protect people working on the line. But for just a boiler I wondered
whether I could connect a three pin socket after the FCU and plug the
CH electrics into that and have a second three pin socket next to it
connected to the inverter. When there's a power cut I could just move
the plug from the mains socket to the inverter socket and isolate that
way. What do you think?

But then my mind started running away with itself. Being dark was
almost as bad as being cold. I wondered whether I could also connect
the lights to something. Since lights are on a 5A radial circuit,
could you do a similar thing: take the cable from the 5A MCB to a 5A
round pin socket and plug the lights into that and have a second round
pin socket from the inverter and switch the plugs over in an
emergency?

I know one way would be to fit separate emergency lights to each room
but SWMBO wouldn't like the aesthetics of two lights per room!

If you had a house with a dozen 100W bulbs, this would be another
1.2kW but if they were CFLs, it might be just 120W, which means you
could run them for ten times longer from the same inverter. This is
where I get confused because there seems to be so much conflicting
advice. It seems there are two issues:
1. do the lights draw high currents when they switch on
2. can they run off less than perfect sine waves?

Does anyone have any definitive answers for the different types of
bulbs (filament and CFL mainly).

I was thinking for just CH and lighting an inverter might be
sufficient rather than the expense and noise of a generator. But it is
tempting to go further and say that it would be nice to run the
freezers in a power cut, the TV, the computer... where do you draw the
line?

I understand that freezer compressors have a start-up surge that
inverters don't like, so I guess that if I want to start powering
them, I would need to think about a small generator. I don't want to
spend hundreds since (hopefully) these power cuts won't be a regular
thing!

We live in a village so there's no mains gas, which means the cooker
is electric but I imagine I would need a huge generator for that, so I
guess a small camping stove is the only sensible way to make a cup of
tea, unless I could run a travel kettle from a small generator?

Thanks very much, and apologies for the long post!

Stephen.

HI Stephen

Stephen wrote:
Hello,

We had a power cut for three hours last night. I happened at the worst
possible time: just as we were getting cold, dark, and hungry.

We have oil fired central heating and it was frustrating that we had a
tank full of oil but could not use the CH because we had no power for
the boiler. This got me thinking that perhaps I could buy a cheap
inverter and run the boiler from a car battery.

The boiler instructions say it must be connected via a 5A FCU, but
240*5=1.2kW, so that's a bigger inverter than I had originally
thought.

Also connected to the FCU are the pump, valves, etc. IIRC the pump
uses about 40W. When I bought the valves, I didn't realise there were
different types, I just bought what was in the screwfix catalogue.
Unfortunately, they are spring operated so draw 6W all the time they
are on. I wish I had known about motorised on and off ones that only
draw current when switching. I will ask the boiler manufacturer, but
in the meantime, does anyone know how much current a modern oil-fired
condensing boiler draws? Surely it can't be a kilowatt? But then
motors have a surge when they are switched on, don't they, so I guess
the 5A fuse is to tolerate that?

It would be nice if I could use a (made-up number) 300W inverter with
momentary peak output of 1.2kW rather than have to pay for a
continuously rated 1.2kW inverter.

I read all the old posts on this group about inverters and generators
and see that a break before make changeover switch must be used to
protect people working on the line. But for just a boiler I wondered
whether I could connect a three pin socket after the FCU and plug the
CH electrics into that and have a second three pin socket next to it
connected to the inverter. When there's a power cut I could just move
the plug from the mains socket to the inverter socket and isolate that
way. What do you think?

But then my mind started running away with itself. Being dark was
almost as bad as being cold. I wondered whether I could also connect
the lights to something. Since lights are on a 5A radial circuit,
could you do a similar thing: take the cable from the 5A MCB to a 5A
round pin socket and plug the lights into that and have a second round
pin socket from the inverter and switch the plugs over in an
emergency?

I know one way would be to fit separate emergency lights to each room
but SWMBO wouldn't like the aesthetics of two lights per room!

If you had a house with a dozen 100W bulbs, this would be another
1.2kW but if they were CFLs, it might be just 120W, which means you
could run them for ten times longer from the same inverter. This is
where I get confused because there seems to be so much conflicting
advice. It seems there are two issues:
1. do the lights draw high currents when they switch on
2. can they run off less than perfect sine waves?

Does anyone have any definitive answers for the different types of
bulbs (filament and CFL mainly).

I was thinking for just CH and lighting an inverter might be
sufficient rather than the expense and noise of a generator. But it is
tempting to go further and say that it would be nice to run the
freezers in a power cut, the TV, the computer... where do you draw the
line?

I understand that freezer compressors have a start-up surge that
inverters don't like, so I guess that if I want to start powering
them, I would need to think about a small generator. I don't want to
spend hundreds since (hopefully) these power cuts won't be a regular
thing!

We live in a village so there's no mains gas, which means the cooker
is electric but I imagine I would need a huge generator for that, so I
guess a small camping stove is the only sensible way to make a cup of
tea, unless I could run a travel kettle from a small generator?

Thanks very much, and apologies for the long post!

Stephen.

It's all possible !

Rather than a car battery, look for a caravan 'leisure battery' - which
is designed to supply power over a longer period (car beattery is
optimised for a short, sharp discharge via the srater motor - and
doesn't perform well at lower currents over long periods..

The 5A rating sounds somewhat arbitrary to me - just a 'handy value' -
I'd imagine that the actual current is much less than that...

Back at the last house we did a similar thing with a 12v-to-mains
invertor run off the car and feeding the c/h system via a long mains
extension lead - simply left the car on tickover to keep the battery
topped up, and there were no close neighbours to be bothered by it....

Very un-green - but we knew that power was going to be restored later
that day......

I guess you have to create a couple of lists of 'must haves' and 'nice
to haves' - and measure the actual power requirement for each list (some
things may have their consumptions actually marked on them).

Then it's down to how much you want to spend - and how long you
anticipate being without power.....

Hope this helps
Adrian

On Thu, 29 Jan 2009 10:19:54 +0000, Adrian
wrote:

The 5A rating sounds somewhat arbitrary to me - just a 'handy value' -
I'd imagine that the actual current is much less than that...

Hello again,

Thanks for the reply. I'm, just wondering do these plug in energy
monitors tell you the peak current that something draws when it first
switches on or do they just show current in real time? That might be
one way to measure the peak requirements?

The old posts about generators talk about connecting neutral and earth
to an earth spike and using an RCD on the generator. Does the same
apply to inverters?

Thanks.

HI Stephen

Stephen wrote:
On Thu, 29 Jan 2009 10:19:54 +0000, Adrian
wrote:

The 5A rating sounds somewhat arbitrary to me - just a 'handy value' -
I'd imagine that the actual current is much less than that...

Hello again,

Thanks for the reply. I'm, just wondering do these plug in energy
monitors tell you the peak current that something draws when it first
switches on or do they just show current in real time? That might be
one way to measure the peak requirements?

Mine (efergy) shows power in real-time - presumably averaged over a few
seconds - so it's not going to show switch-on surges...


The old posts about generators talk about connecting neutral and earth
to an earth spike and using an RCD on the generator. Does the same
apply to inverters?

I never have done - but it was a bit 'spur of the moment' rather than a
'proper' installation...... I'm sure that somebody on here knows the
proper answer...

As to switch-on surges - probably the best test is empirical - buy one
and give it a try - they're cheap enough....

In our case the c/h system was via a multifuel (wood / coal etc) stove -
so all we were switching was the circulating pump and associated valvery
- but the little inverter (150W) was quite happy with it....

Adrian

"Stephen" wrote in message
...
Hello,

We had a power cut for three hours last night. I happened at the worst
possible time: just as we were getting cold, dark, and hungry.

We have oil fired central heating and it was frustrating that we had a
tank full of oil but could not use the CH because we had no power for
the boiler. This got me thinking that perhaps I could buy a cheap
inverter and run the boiler from a car battery.

The boiler instructions say it must be connected via a 5A FCU, but
240*5=1.2kW, so that's a bigger inverter than I had originally
thought.

Also connected to the FCU are the pump, valves, etc. IIRC the pump
uses about 40W. When I bought the valves, I didn't realise there were
different types, I just bought what was in the screwfix catalogue.
Unfortunately, they are spring operated so draw 6W all the time they
are on. I wish I had known about motorised on and off ones that only
draw current when switching. I will ask the boiler manufacturer, but
in the meantime, does anyone know how much current a modern oil-fired
condensing boiler draws? Surely it can't be a kilowatt? But then
motors have a surge when they are switched on, don't they, so I guess
the 5A fuse is to tolerate that?

It would be nice if I could use a (made-up number) 300W inverter with
momentary peak output of 1.2kW rather than have to pay for a
continuously rated 1.2kW inverter.

I read all the old posts on this group about inverters and generators
and see that a break before make changeover switch must be used to
protect people working on the line. But for just a boiler I wondered
whether I could connect a three pin socket after the FCU and plug the
CH electrics into that and have a second three pin socket next to it
connected to the inverter. When there's a power cut I could just move
the plug from the mains socket to the inverter socket and isolate that
way. What do you think?

But then my mind started running away with itself. Being dark was
almost as bad as being cold. I wondered whether I could also connect
the lights to something. Since lights are on a 5A radial circuit,
could you do a similar thing: take the cable from the 5A MCB to a 5A
round pin socket and plug the lights into that and have a second round
pin socket from the inverter and switch the plugs over in an
emergency?

I know one way would be to fit separate emergency lights to each room
but SWMBO wouldn't like the aesthetics of two lights per room!

If you had a house with a dozen 100W bulbs, this would be another
1.2kW but if they were CFLs, it might be just 120W, which means you
could run them for ten times longer from the same inverter. This is
where I get confused because there seems to be so much conflicting
advice. It seems there are two issues:
1. do the lights draw high currents when they switch on
2. can they run off less than perfect sine waves?

Does anyone have any definitive answers for the different types of
bulbs (filament and CFL mainly).

I was thinking for just CH and lighting an inverter might be
sufficient rather than the expense and noise of a generator. But it is
tempting to go further and say that it would be nice to run the
freezers in a power cut, the TV, the computer... where do you draw the
line?

I understand that freezer compressors have a start-up surge that
inverters don't like, so I guess that if I want to start powering
them, I would need to think about a small generator. I don't want to
spend hundreds since (hopefully) these power cuts won't be a regular
thing!

We live in a village so there's no mains gas, which means the cooker
is electric but I imagine I would need a huge generator for that, so I
guess a small camping stove is the only sensible way to make a cup of
tea, unless I could run a travel kettle from a small generator?

Thanks very much, and apologies for the long post!

Stephen.

We have exactly the same situation where we live, except we have a Stanley
oil fired range which supplies cooking and CH, the last powercut we had, I
had a Aldi 150W invertor in the car extension cable into the house and the
wireless router running off it, with laptop on batteries, well you can't do
without the world wide web and there is only so many games of 'I Spy' you
can play!
It did get me to thinking about the Stanley, it uses a single oil burner
motor and from what I have seen of other oil central heating systems they
they use the same principle and in some cases the same motor!. I checked the
spec of mine and when running it consumes max 90 watts which is well within
the capability of the cheap invertor. If I include the ch pump at 40W it's
only 130 watts combined.
If you are planning on using a 300 watt invertor that should work OK even my
cheap £14 aldi special should be OK,

Des

On Thu, 29 Jan 2009 13:13:10 +0000, Adrian wrote:

HI Stephen

Stephen wrote:
-------------------8
Thanks for the reply. I'm, just wondering do these plug in energy
monitors tell you the peak current that something draws when it first
switches on or do they just show current in real time? That might be
one way to measure the peak requirements?

Mine (efergy) shows power in real-time - presumably averaged over a few
seconds - so it's not going to show switch-on surges...

I'm pretty sure the Owl that we have does a spot read every six seconds.

On Thu, 29 Jan 2009 09:49:23 +0000, Stephen wrote:

We have oil fired central heating and it was frustrating that we had a
tank full of oil but could not use the CH because we had no power for
the boiler. This got me thinking that perhaps I could buy a cheap
inverter and run the boiler from a car battery.

Perfectly possible. It's already been pointed out that a leisure battery
would be better than a car battery as they are designed for deep
discharge, car batteries aren't and one deep discharge can kill 'em.

All the bits of kit will have a rating plate, add 'em all up. Our oil
bolier is 150W IIRC, 50W for the pump so say 250W all up for the heating.
This is probably getteing a bit close to the edge for a cheap 300W
invertor and doesn't leave any space for a light or two.

Now do some basic maths on the current at 12v and the size of battery
required. 300W output at 95% means 315W input P=VA so that is 26A @ 12v.
So to cover your 3 hour outage you need a battery with a capacity of
75A/Hr. I'd go for a 110A/hr battery this should keep you going for quite
a while and if you have the capacity on the invertor run the freezer as
well. Bearing in mind that the boiler won't be running all the time, I'd
also put a jumper and another pair of socks on and operate the boiler
manually when it started to feel cold. The freezer would also be OK for 6+
hrs, unplug your boiler plug in the frezzer untill it stops then plug back
to boiler.

Think about maintenance of the battery lead acids don't self discharge
very quickly but they do if left for a year or so. One of the small solar
panels connected across it when not is used should keep it nicely ready
for action. Keep an eye on electrolyte levels as well.

What ever you go for it has to work after being idle for possibly a number
of years. Routine proper testing under realistic load for several hours is
required to ensure that. Just trying a back up system off load for 10 mins
every 6 months is *not* a proper test.

But for just a boiler I wondered whether I could connect a three pin
socket after the FCU and plug the CH electrics into that and have a
second three pin socket next to it connected to the inverter.

That is effectively what I have done except that the 13A plug (with 3A
fuse) would be plugged into the extension lead from the small generator
outside which would be split to fridges/freezers and a few lights on
extensions as well.

Since lights are on a 5A radial circuit, could you do a similar thing:

I don't like that idea, be far too easy to turn on too many lights.
Especially if there are those in the family that only know how to trun
lights on and not off.

But it is tempting to go further and say that it would be nice to run
the freezers in a power cut, the TV, the computer... where do you draw
the line?

Up to you! Heating is probably first priority for us as we are exposed and
high in a old not particulary well insulated house. 2nd light so you can
play board games, cook, be able to move about in relative safety (we have
gas lanterns for that, loads of light long run times, bettery lights are
poor in comparision). Freezers so you don't have to chuck out and
repurchase food, though I expect household insurace may cover the cost of
that it is still agro. If you have kids the TV and it's associated set top
boxes (DSAT/DTTV, xBox, DVD etc) might be worth considering but that 42"
plasma screen is very power hungry. Monopoly doesn't take any power and is
a long game to play. B-)

so I guess a small camping stove is the only sensible way to make a cup
of tea, unless I could run a travel kettle from a small generator?

No mains gas here either, for power cut useage we have two ring and grill
camping hob and 17kg butance cylinder for it. Stock of cup a soups, bread,
pasta tins etc we can eat and drink well for several days, might be a bit
repetative after a few days but hey it's decent hot food and drink. Better
than cold baked beans on bread (not toast!).

--
Cheers
Dave.

We were somewhere around Barstow, on the edge of the desert, when the
drugs began to take hold. I remember Stephen
saying something like:

I was doing this for real, just a fortnight ago when storm-force winds
took out public power supplies around here for 7 hours or so, running my
house from a 1kW inverter connected to the vehicle's battery with the
engine at fast idle. Mindful of the possibility of overheating the
alternator I kept the loads as low as possible, to about 5~600W. I
didn't bother running the CH from it, but I've tested it in the past and
it ran fine from the inverter, drawing just a couple of hundred watts.

The inverter is a modified sine wave with two 13A sockets and overload
protection, quite cheap from ebay. Similar to this one...
http://cgi.ebay.co.uk/ws/eBayISAPI.d...m=200302299032

This one is pure sine wave; if I was buying another one, I think I'd go
with this...
http://cgi.ebay.co.uk/ws/eBayISAPI.d...m=220349977660

I understand that freezer compressors have a start-up surge that
inverters don't like, so I guess that if I want to start powering
them, I would need to think about a small generator. I don't want to
spend hundreds since (hopefully) these power cuts won't be a regular
thing!

What I found was, the fridge would start fine, but knocked the telly out
as it did so. The TV being a bit sensitive to the volt drop as the
start-up surge robbed it. A couple of times of that happening and the
fridge was unplugged.

Stephen wrote:
Hello,

We had a power cut for three hours last night. I happened at the worst
possible time: just as we were getting cold, dark, and hungry.

We have oil fired central heating and it was frustrating that we had a
tank full of oil but could not use the CH because we had no power for
the boiler. This got me thinking that perhaps I could buy a cheap
inverter and run the boiler from a car battery.

The boiler instructions say it must be connected via a 5A FCU, but
240*5=1.2kW, so that's a bigger inverter than I had originally
thought.

CH is very unlikely to consume 1.2kW. Fuse ratings arent chosen that
way.


Also connected to the FCU are the pump, valves, etc. IIRC the pump
uses about 40W. When I bought the valves, I didn't realise there were
different types, I just bought what was in the screwfix catalogue.
Unfortunately, they are spring operated so draw 6W all the time they
are on. I wish I had known about motorised on and off ones that only
draw current when switching. I will ask the boiler manufacturer, but
in the meantime, does anyone know how much current a modern oil-fired
condensing boiler draws? Surely it can't be a kilowatt?

look at the ratings plate

But then
motors have a surge when they are switched on, don't they, so I guess
the 5A fuse is to tolerate that?

It would be nice if I could use a (made-up number) 300W inverter with
momentary peak output of 1.2kW rather than have to pay for a
continuously rated 1.2kW inverter.

thats how its normally done

I read all the old posts on this group about inverters and generators
and see that a break before make changeover switch must be used to
protect people working on the line. But for just a boiler I wondered
whether I could connect a three pin socket after the FCU and plug the
CH electrics into that and have a second three pin socket next to it
connected to the inverter. When there's a power cut I could just move
the plug from the mains socket to the inverter socket and isolate that
way. What do you think?

lot easier just to use an extension lead. Nothing to install then

But then my mind started running away with itself. Being dark was
almost as bad as being cold. I wondered whether I could also connect
the lights to something. Since lights are on a 5A radial circuit,
could you do a similar thing: take the cable from the 5A MCB to a 5A
round pin socket and plug the lights into that and have a second round
pin socket from the inverter and switch the plugs over in an
emergency?

you could, but again a single cfl light on an extension lead is
easier.

I know one way would be to fit separate emergency lights to each room
but SWMBO wouldn't like the aesthetics of two lights per room!

there are ways to make them invisible, and even ways to make them look
funky.


If you had a house with a dozen 100W bulbs, this would be another
1.2kW but if they were CFLs, it might be just 120W, which means you
could run them for ten times longer from the same inverter.

and a single 23w cfl would run 5x longer again. Perhaps add a 3w one
fot eh bathroom, or a 1w LED on its own battery.

This is
where I get confused because there seems to be so much conflicting
advice. It seems there are two issues:
1. do the lights draw high currents when they switch on

not really. A bit of a surge, but the amount's trivial.

2. can they run off less than perfect sine waves?

any wave shape and frequency is fine, even dc.

Does anyone have any definitive answers for the different types of
bulbs (filament and CFL mainly).

Theres no way you want to run 1kW of filaments off a battery! Its cfl,
linear fl or led.


I was thinking for just CH and lighting an inverter might be
sufficient rather than the expense and noise of a generator.

yup

But it is
tempting to go further and say that it would be nice to run the
freezers in a power cut,

things stay frozen for many hours with no power

the TV, the computer... where do you draw the
line?

how often are these power cuts, how long do they last? I doubt its
worth doing most of the things you suggest here, but thats your
decision. Easier would be to get a few battery powered LED lights or a
portable gas lamp for lighting, and a candle driven food warmer for
tea, and leave it at that. Eating sandwiches and waiting for the tea
is hardly the most rigorous hardship once a year.


I understand that freezer compressors have a start-up surge that
inverters don't like, so I guess that if I want to start powering
them, I would need to think about a small generator. I don't want to
spend hundreds since (hopefully) these power cuts won't be a regular
thing!

forget it - unless you really live in the middle of nowhere and expect
power cuts to last for days.


We live in a village so there's no mains gas, which means the cooker
is electric but I imagine I would need a huge generator for that,

entirely impractical

so I
guess a small camping stove is the only sensible way to make a cup of
tea,

or use a candle or candle powered food warmer. Yes, its very slow.


unless I could run a travel kettle from a small generator?

no


Thanks very much, and apologies for the long post!

Stephen.


Perspective is the place to start. Have you nothing better to do with
the time and money? Can you not cope with minimal lighting levels for
a few hours per year? These systems have their uses, but most of us
dont need them.

http://www.wiki.diyfaq.org.uk/index....e=Backup_power


NT

"Owain" wrote in message
...
Stephen wrote:
I know one way would be to fit separate emergency lights to each room
but SWMBO wouldn't like the aesthetics of two lights per room!

http://www.tlc-direct.co.uk/Main_Ind...afe/index.html

Replaces existing ceiling rose; incorporates a smoke alarm and "An
Emergency Light - It activates automatically when mains power fails. To
illuminate a safe environment and ensure light is available when required
a day and night sensor is incorporated to conserve energy."

It says it illuminates a 3.6 sq meter room so it would be OK in a small
toilet but not much more.
I assume it means 3.6 meter sq.

Suitable for filament and low-energy lamps

Owain

On Thu, 29 Jan 2009 15:33:28 +0000 (GMT), "Dave Liquorice"
wrote:

I'd go for a 110A/hr battery this should keep you going for quite
a while and if you have the capacity on the invertor run the freezer as
well. Bearing in mind that the boiler won't be running all the time, I'd
also put a jumper and another pair of socks on and operate the boiler
manually when it started to feel cold. The freezer would also be OK for 6+
hrs, unplug your boiler plug in the frezzer untill it stops then plug back
to boiler.

I hadn't appreciated that the boiler has a duty cycle, that's a good
point; the battery will last longer than I had thought.

If I have done the maths right, you are rating the freezer at just
over 200W?

I had forgot these appliances had label on! I've just got on my hands
and knees and our freezer says something about being 140W, 13A fuse,
picture of a square wave, 240W. I'm not sure why it says both 140W and
240W, nor the significance of the wave picture? If it is only 240W,
why the 13A fuse? I guess that's because of the surge current; it must
be pretty big. I suppose that like the boiler, a freezer is not
running continuously, so it's all about diversity?

That is effectively what I have done except that the 13A plug (with 3A
fuse) would be plugged into the extension lead from the small generator
outside which would be split to fridges/freezers and a few lights on
extensions as well.

But does this mean you have to go outside and bring lights in? What
are they, site lights? Isn't that a hassle having trailing leads
everywhere?

Since lights are on a 5A radial circuit, could you do a similar thing:

I don't like that idea, be far too easy to turn on too many lights.
Especially if there are those in the family that only know how to trun
lights on and not off.

Would that depend on your choice of lights? I know some here hate
CFLs, but if you were completely CFL, it might work?

No mains gas here either, for power cut useage we have two ring and grill
camping hob and 17kg butance cylinder for it.

Can these be used indoors? I wondered about one of these but I'm sure
I read somewhere they were for outdoor use only.

we have gas lanterns for that, loads of light long run times, bettery lights are
poor in comparision

I know that gas heaters have been criticised here because they cause
condensation and need fresh air. I suppose a gas light using much less
gas these things become less of a concern? Do gas appliances set off
your battery-backed up smoke alarms though?

Thanks again.

On Thu, 29 Jan 2009 08:36:39 -0800 (PST), wrote:

Have you nothing better to do with
the time and money?

But it's a DIY group and we want to justify buying an inverter

On Thu, 29 Jan 2009 13:23:26 +0000, Owain
wrote:

http://www.tlc-direct.co.uk/Main_Ind...afe/index.html

Replaces existing ceiling rose; incorporates a smoke alarm and "An
Emergency Light - It activates automatically when mains power fails.

I had a look at the link but I couldn't see the emergency light. Does
it power the bulb at low power or does the pendant glow?

On Thu, 29 Jan 2009 08:36:39 -0800 (PST), wrote:

unless I could run a travel kettle from a small generator?

no

A travel kettle is 240v 850W, so why not?

We were somewhere around Barstow, on the edge of the desert, when the
drugs began to take hold. I remember Stephen
saying something like:

On Thu, 29 Jan 2009 08:36:39 -0800 (PST), wrote:

unless I could run a travel kettle from a small generator?

no

A travel kettle is 240v 850W, so why not?

No reason at all why not. Purely resistive load and just make sure you
don't use all the gen output up on the kettle.

On Thu, 29 Jan 2009 20:42:30 +0000, Stephen wrote:

unless I could run a travel kettle from a small generator?

no

A travel kettle is 240v 850W, so why not?

Define "small generator"...

The generators used at work "small" would be 50kW...

The little 2 stroke jobbies are about 600 to 750W. Probably survive for
the time taken by a couple of mugs of water, might be pushing it for a 3l
kettle full though. B-) Wouldn't be able to power anything else at the
same time though.

--
Cheers
Dave.

On Thu, 29 Jan 2009 20:16:30 +0000, Stephen wrote:

The freezer would also be OK for 6+ hrs, unplug your boiler plug in the
frezzer untill it stops then plug back to boiler.
snip
If I have done the maths right, you are rating the freezer at just
over 200W?

You might be misreading what I wrote. Almost any freezer will be OK
without any power at all for 6+hrs, provided you don't open it. It would
just need a boost of cold every so often.

I had forgot these appliances had label on! I've just got on my hands
and knees and our freezer says something about being 140W, 13A fuse,
picture of a square wave, 240W. I'm not sure why it says both 140W and
240W, nor the significance of the wave picture?

I'm not sure about the square wave, duty cycle? 140W mean 240W running?
That doesn't feel right though at 3.36kw/hr day.

why the 13A fuse? I guess that's because of the surge current; it must
be pretty big.

Probably the motor is starting underload so will pull quite a surge. When
thinking about the rating of gensets to power motors the rule of thumb is
2 to 3 times the running rating of a motor is required to start it.

That is effectively what I have done except that the 13A plug (with 3A
fuse) would be plugged into the extension lead from the small generator
outside which would be split to fridges/freezers and a few lights on
extensions as well.

But does this mean you have to go outside and bring lights in?

Electric lights would be way down the list as we use gas lanterns... They
would be normal table lamps from bedside cabinets or else where.

I'd have to go out and fire up the generator and run the lead from it into
the house.

Isn't that a hassle having trailing leads everywhere?

It's gets quite complicated if you want to use the house wiring when the
power has gone. You can't reley on the supply earth still being earth so
you need to provide your own, and tie the "neutral" side of the genset to
that. Not to mention ensuring fail safe isolation between your gen/house
wiring and the supply. And the possibilty of someone forgetting that you
are on a 2kW generator and clicking on the 3kW kettle...

Extensions are the "simple" way out and can be manged safely with a bit of
thought. Running temporay cables safely is a major part of my job, so it's
second nature. I must admit to being horrified at the way most people
handle and run cables.

Since lights are on a 5A radial circuit, could you do a similar thing:

I don't like that idea, be far too easy to turn on too many lights.

Would that depend on your choice of lights? I know some here hate
CFLs, but if you were completely CFL, it might work?

Probably I just don't like the idea of the house wiring being live when
the rest is dead. You also have the earthing implications to think about.

No mains gas here either, for power cut useage we have two ring and
grill camping hob and 17kg butance cylinder for it.

Can these be used indoors? I wondered about one of these but I'm sure
I read somewhere they were for outdoor use only.

What is the difference between it and a mains gas hob? Provided you have
some where stable and safe to put it. Ours sits over the rings of the
elctric hob quite nicely.

I know that gas heaters have been criticised here because they cause
condensation and need fresh air.

True enough every kg of gas burnt produces a litre of water. We also have
a portable gas fire as backup. I guess in a hermetically sealed, heavly
insulated modern box, the bit of extra moisture might be a problem (have
they banned having opening windows yet?) but it's not in a 17th C
farmhouse...

I suppose a gas light using much less gas these things become less of a
concern? Do gas appliances set off your battery-backed up smoke alarms
though?

Nope, only if you burn the toast like a normal gas grill. The combustion
products are mainly CO2 and water.

--
Cheers
Dave.

Stephen wrote:
On Thu, 29 Jan 2009 08:36:39 -0800 (PST), wrote:

unless I could run a travel kettle from a small generator?

no

A travel kettle is 240v 850W, so why not?

Literally speaking you can, its just not a solution I could imagine
recommending. All that kit, hassle, cost, time, trouble, storge
space... there are so much easier ways.


NT

"Dave Liquorice" wrote:
On Thu, 29 Jan 2009 20:42:30 +0000, Stephen wrote:

unless I could run a travel kettle from a small generator?

no

A travel kettle is 240v 850W, so why not?

Define "small generator"...

The generators used at work "small" would be 50kW...

The little 2 stroke jobbies are about 600 to 750W. Probably survive for
the time taken by a couple of mugs of water, might be pushing it for a 3l
kettle full though. B-) Wouldn't be able to power anything else at the
same time though.


I wonder how much fuel they would need to boil, say, a litre of water?

On Fri, 30 Jan 2009 01:30:16 +0000, Bruce wrote:

I wonder how much fuel they would need to boil, say, a litre of water?

Petrol has about 35MJ/l.
Water has a heat capacity of 4.184 J/gK.
1l water weighs 1kg.
Say a delta T of 85K
Energy required = 4.184 * 1000 * 85 = 356kJ
50% efficient energy from fuel = 712kJ.
Fuel required = 712/35,000 = 20ml = 4 teaspoons.

--
Cheers
Dave.

On Fri, 30 Jan 2009 07:57:34 +0000 (GMT), Dave Liquorice wrote:

On Fri, 30 Jan 2009 01:30:16 +0000, Bruce wrote:

I wonder how much fuel they would need to boil, say, a litre of water?

Petrol has about 35MJ/l.
Water has a heat capacity of 4.184 J/gK.
1l water weighs 1kg.
Say a delta T of 85K
Energy required = 4.184 * 1000 * 85 = 356kJ
50% efficient energy from fuel = 712kJ.
Fuel required = 712/35,000 = 20ml = 4 teaspoons.

If I'm understanding that correctly, petrol as a portable medium for stored
energy is hard to beat. (?)

On Thu, 29 Jan 2009 22:12:05 +0000 (GMT), "Dave Liquorice"
wrote:

If I have done the maths right, you are rating the freezer at just
over 200W?

You might be misreading what I wrote. Almost any freezer will be OK
without any power at all for 6+hrs, provided you don't open it. It would
just need a boost of cold every so often.

But if I plug it in for a boost, I still need to know the rating to
make sure it's within the capabilities of my inverter.

I was thinking of buying a 300W continuous, 1kW peak inverter to try
out. I thought this would be enough to power just the CH and I could
unplug the CH and plug in the freezer as required. I will probably get
a gas lantern and a small gas stove to boil water for hot drinks.

However, in your earlier post you said that 250W for the CH was too
close to comfort to the 300W limit of the inverter. If it is rated at
300W continuously, shouldn't it be able to supply 300W continuously?

Does it make any difference whether I buy a 300W inverter and run it
at high load or if I buy a 2kW inverter and run it at low load? I was
just wondering whether they have to be run hard to run efficient?

I see some web sites list efficiencies of 90-94%. Are they really this
good or is that marketing taking over?

Finally, I see that Black and Decker sell a 400W model with "ground
fault interrupter circuit". Is that RCD to you and me? The B&D web
site is pretty useless and does not say what the peak rating of the
model is. Nor does it show an RCD on the photo.

If I buy a different make, is it advisable to fit a plug-in RCD to the
output and earth the inverter to a spike? Is the neutral already
connecting to the ground or do I have to do that too? Sorry if these
questions are answered in the instruction booklet, but since I haven't
bought one yet, I wouldn't know that.

Thanks.

Appelation Controlee wrote:
On Fri, 30 Jan 2009 07:57:34 +0000 (GMT), Dave Liquorice wrote:

On Fri, 30 Jan 2009 01:30:16 +0000, Bruce wrote:

I wonder how much fuel they would need to boil, say, a litre of water?
Petrol has about 35MJ/l.
Water has a heat capacity of 4.184 J/gK.
1l water weighs 1kg.
Say a delta T of 85K
Energy required = 4.184 * 1000 * 85 = 356kJ
50% efficient energy from fuel = 712kJ.
Fuel required = 712/35,000 = 20ml = 4 teaspoons.

If I'm understanding that correctly, petrol as a portable medium for stored
energy is hard to beat. (?)

Hence petrol camping stoves. But the great advantage is that a petrol
burning stove (e.g. Coleman) is small and light enough to put in a
backpack and carry. I wouldn't want to carry a generator...

--
Rod

Hypothyroidism is a seriously debilitating condition with an insidious
onset.
Although common it frequently goes undiagnosed.
www.thyromind.info www.thyroiduk.org www.altsupportthyroid.org

"Dave Liquorice" wrote:
On Fri, 30 Jan 2009 01:30:16 +0000, Bruce wrote:

I wonder how much fuel they would need to boil, say, a litre of water?

Petrol has about 35MJ/l.
Water has a heat capacity of 4.184 J/gK.
1l water weighs 1kg.
Say a delta T of 85K
Energy required = 4.184 * 1000 * 85 = 356kJ
50% efficient energy from fuel = 712kJ.
Fuel required = 712/35,000 = 20ml = 4 teaspoons.


Wonderful! Thank you very much.

On Fri, 30 Jan 2009 09:55:50 +0000, Appelation Controlee wrote:

Petrol has about 35MJ/l.

If I'm understanding that correctly, petrol as a portable medium for
stored energy is hard to beat. (?)

It's pretty good but diesel is better around 38MJ/l. In fact 35MJ/l for
petrol might be a bit optomistic, seen 32MJ/l just now.

--
Cheers
Dave.

Owain wrote:
Stephen wrote:

http://www.tlc-direct.co.uk/Main_Ind...afe/index.html
Replaces existing ceiling rose; incorporates a smoke alarm and "An
Emergency Light - It activates automatically when mains power fails.
I had a look at the link but I couldn't see the emergency light. Does
it power the bulb at low power or does the pendant glow?

I thought it would power the bulb, but not sure

Owain

I cant see a battery big enough to power a 100w bulb fitting in there,
and theres no reason they would make it several times as expensive.
Its almost certainly LEDs. The dubious light output spec pretty much
confirms that.


NT

Dave Liquorice wrote:
On Thu, 29 Jan 2009 20:16:30 +0000, Stephen wrote:

The freezer would also be OK for 6+ hrs, unplug your boiler plug in the
frezzer untill it stops then plug back to boiler.
snip
If I have done the maths right, you are rating the freezer at just
over 200W?

You might be misreading what I wrote. Almost any freezer will be OK
without any power at all for 6+hrs, provided you don't open it. It would
just need a boost of cold every so often.

I had forgot these appliances had label on! I've just got on my hands
and knees and our freezer says something about being 140W, 13A fuse,
picture of a square wave, 240W. I'm not sure why it says both 140W and
240W, nor the significance of the wave picture?

I'm not sure about the square wave, duty cycle? 140W mean 240W running?
That doesn't feel right though at 3.36kw/hr day.

why the 13A fuse? I guess that's because of the surge current; it must
be pretty big.

Probably the motor is starting underload so will pull quite a surge. When
thinking about the rating of gensets to power motors the rule of thumb is
2 to 3 times the running rating of a motor is required to start it.


The thinner the fuse, the more often they die of natural causes. The
last thing you want with a freezer is for the fuse to die, so you go
as high as poss, ie 13A, regardless of load. 2A fuses are especially
issueful in this respect, which is probably why theyre not common.


NT

Stephen wrote:

Does it make any difference whether I buy a 300W inverter and run it
at high load or if I buy a 2kW inverter and run it at low load? I was
just wondering whether they have to be run hard to run efficient?

invertor losses are made up of
a) pass losses, which depend on load current
b) standing losses, which depend only on invertor design, and which
occur regardless of load.

To answer your q fully you'd need to compare the quiescent consumption
of each invertor.


I see some web sites list efficiencies of 90-94%. Are they really this
good or is that marketing taking over?

one particular load yes, the rest of the time no. Under no load
efficiency drops to 0%.


Finally, I see that Black and Decker sell a 400W model with "ground
fault interrupter circuit". Is that RCD to you and me? The B&D web
site is pretty useless and does not say what the peak rating of the
model is. Nor does it show an RCD on the photo.

gfci is the US term for rcd, so yes, same deal. The rcd circuitry
might be on the main invertor pcb, I dont know the model.


If I buy a different make, is it advisable to fit a plug-in RCD to the
output and earth the inverter to a spike? Is the neutral already
connecting to the ground or do I have to do that too? Sorry if these
questions are answered in the instruction booklet, but since I haven't
bought one yet, I wouldn't know that.

Thanks.

Small invertors and portable gens usually have close to nothing in the
way of safety features. Typically no earth at all and no rcd. Many
gens have a breaker (MCB), some dont even have that. Its up to you how
much safety you want to add. Earthing plus rcd would be a nice idea.


NT

Appelation Controlee wrote:

If I'm understanding that correctly, petrol as a portable medium for stored
energy is hard to beat. (?)


Why do you think it is used in billions of cars around the world?

On Fri, 30 Jan 2009 17:30:55 +0000, Bruce wrote:

Appelation Controlee wrote:

If I'm understanding that correctly, petrol as a portable medium for stored
energy is hard to beat. (?)


Why do you think it is used in billions of cars around the world?

No idea - if we still had a coal industry ...

On Fri, 30 Jan 2009 10:08:53 +0000, Stephen wrote:

I was thinking of buying a 300W continuous, 1kW peak inverter to try
out. I thought this would be enough to power just the CH and I could
unplug the CH and plug in the freezer as required. I will probably get
a gas lantern and a small gas stove to boil water for hot drinks.

That's sensible but be aware that the "camping gaz" high pressure stoves
can be a little unstable when they have a kettle or pan of water on top.
They are also surprisingly tall.

However, in your earlier post you said that 250W for the CH was too
close to comfort to the 300W limit of the inverter. If it is rated at
300W continuously, shouldn't it be able to supply 300W continuously?

A 300W cont should be able deliver 300W cont. I'm just a little sceptical
about the ratings of cheap kit. It may well be able to deliver 300W cont
but gets red hot in the process, excessive heat is a good way to kill
electronic components. Hot is OK up to 50 or 60C package temp on a decent
heat sink but IMHO much hotter is asking for a short life.

Does it make any difference whether I buy a 300W inverter and run it
at high load or if I buy a 2kW inverter and run it at low load? I was
just wondering whether they have to be run hard to run efficient?

Probably better loaded up, they take some current even without a load.

I see some web sites list efficiencies of 90-94%. Are they really this
good or is that marketing taking over?

Should be about that, they'd get seriously hot if they weren't.

Finally, I see that Black and Decker sell a 400W model with "ground
fault interrupter circuit". Is that RCD to you and me?

Yep, left pondisium for RCD. It could be built into the unit so not
obvious from the picture.

If I buy a different make, is it advisable to fit a plug-in RCD to the
output and earth the inverter to a spike?

It gets complicated... if the live and neutral of the invertor are both
truely floating with respect to real ground, then an RCD won't gain you
much protection as there is no other return circuit to the invertor.

If one of the outputs ("live" or "neutral") does have a path to ground at
the invertor then an RCD would be a good idea.

--
Cheers
Dave.

On Mon, 02 Feb 2009 09:43:38 +0000 (GMT), "Dave Liquorice"
wrote:

Probably better loaded up, they take some current even without a load.

I have had a read of the B&D manual for their 400W inverter. It says
that it takes 0.7A when do nothing. That seems a lot to me. What is it
doing? Surely it only needs to light the "on" LED?

Finally, I see that Black and Decker sell a 400W model with "ground
fault interrupter circuit". Is that RCD to you and me?

Yep, left pondisium for RCD. It could be built into the unit so not
obvious from the picture.

The manual mentions nothing about an RCD or GFI. That's strange
because it is used in the advertising literature as one of its plus
points. If there is an RCD wouldn't there be test and reset switches?
There are no mention of these.

If I buy a different make, is it advisable to fit a plug-in RCD to the
output and earth the inverter to a spike?

It gets complicated... if the live and neutral of the invertor are both
truely floating with respect to real ground, then an RCD won't gain you
much protection as there is no other return circuit to the invertor.

The manual says not to connect N&E. Whether that's because they are
already connected or whether it's because they will trip the RCD, I
don't know. I'm waiting for clarification from B&D.

On Fri, 06 Feb 2009 15:00:46 +0000, Stephen wrote:

Probably better loaded up, they take some current even without a load.

I have had a read of the B&D manual for their 400W inverter. It says
that it takes 0.7A when do nothing. That seems a lot to me. What is it
doing? Surely it only needs to light the "on" LED?

0.7A @ 12v is only 8W, the circuitry is still active, oscilator running
etc.

If there is an RCD wouldn't there be test and reset switches?

Yes.

--
Cheers
Dave.