CP and Wattage

I was reading with some interest the other day that a petromax has a 400 Watt output. Whereas a typical Vapalux would be circa 60W. Is there that much difference? is the Petro max that much brighter? or are different measurements and ways of describing power being used?

I notice both have a 1 Litre Fount, and both burn for similar times so thats some leap in efficiency!

Thoughts and musings welcome

 

@Manlee

Where did you see the 400Watt figure?

Tony

 

Power output: 400 watts Its from their website, but do they mean something different here rather than light output? I am not an expert on these things. How bright is the 500CP Petromax to a Vapalux for example?

 

@Manlee

What website?

A 500cp will be brighter than a Vapalux 250-300cp.

I'm curious about the "website". 400Watt of light is brighter than anything in my electricity system...

Cheers

Tony

 

Well here is a nice explanation about light !
Lichtmeten / Lightmeter

 

A 500 HK Petromax will give approx 1200...1300 Watts of heat output, you can calculate this from the fuel consumption and energy content of kero.
In German ads you can read "400 Watts of light" in context with Petromax lanterns and clones. This is nonsense, as Watts never give any clue to light output.

Heinze once made a statemant in a leaflet "A 500 HK Petromax will give approx. the light as a 400 Watt light bulb." (This was in the late 1970s or early 80s I think.) Someone must have read it and took advertising speech for real and left out the other half of the original statement.

Erik

 

I think you are also forgetting the equally popular but physically smaller 150/200CP Petromax/ lamps. The 500HK is just one model.
From my own experience of having owned several of both, yes of course a 500CP big lamp is going to be brighter than a more compact lamp rated at 250CP, I'm honestly not convinced they are twice as bright but they are brighter that's a fact.
The larger jet and nozzle do use more fuel, it's all relative. I found my 500HK lamps too bright and much prefer the less intense light from a bialaddin/vapalux.
If we are 'guestimating' light output compared to an old domestic tungsten light bulb then I would give a big Petromax a 60-75 watt equivalent rating compared to the 40-50 watt of a vapalux.

 

Same here.

Plain or pearl (i.e. translucent)? My guess would be that 500 HK/cp would be equivalent to about a 150 watt clear glass bulb, which is far too bright to sit close to...

 

I did some measurements a while back and included some Tungsten fillament light bulbs. Measurements are averages because the filaments are linear. As these are actual measurements they will not be the same for all light bulbs but all the bulbs were previously unused so the readings will be about right for each bulb size.

60W=87cp, 100W=144.5cp, 150W=264.5cp. ::Neil::

 

The Website was the Petromax Website itself. Petromax Paraffin Lamp HK500 - Petromax

Height (ca.): 16.5 in (42 cm)
Bottom diameter (ca.): 6.5 in (16.5 cm)
Tank capacity: 1 litre
Burning time: 8 hours
Power output: 400 watts
Fuel: kerosene or paraffin
Weight: 5.3 lbs (2.4 kg)
Material: brass
Colours: brass polished or brass nickel- and chrome-plated

 

I just find those figures hard to believe, a 150 watt tungsten bulb is a seriously powerful bulb capable of lighting a large room on its own to an uncomfortably bright level, I just can't see a HK500 Petromax lamp held high in the same space as coming anywhere close.
Mackburner's calculations suggest we are seeing closer to 280 watts equivalent! really? I accept that a domestic bulb would normally have the benefit of a sizable diffused reflector which spreads and softens where as pressure lamps just have a pinpoint light source, neither reflected or diffused.

Martin

 

The light meter readings are accurate to about +or- 1%. The readings are repeatable and the meter does not lie. You must remember that all lanterns have light restrictors such as the tank under and hood above so unless fitted with a reflector you only get horizontal light output. You also have to understand that very few pressure lamps do anywhere near their rated power. I have measured many Tilleys at between 80 and 150cp and several 500cp rated Petromax types at about 250cp. Another consideration is that in a domestic situation a light bulb gains much from reflections off a white ceiling and light coloured walls so you get what appears to be more light when in fact because of the reflected effect a light bulb does not need to be near as powerful as a pressure lamp.

I did a series of measurements at Newark in 2008 and only one lamp managed its rated power which was a Hipolito H502 which made 463cp and 2 bar and 550cp at 3 bar. That beast was unreal because even in full daylight it was way too bright to look at.
Here is the list of lamps measured which gives the Make and model, Owner, Rated Power and Peak CP

Hipolito H502 Malcolm 500 463 (550 at 3 bar)
Bialaddin T10 Neil 300 200
Optimus 200 Arjan 200 120
Solar 250 Malcolm 250 125
Bialaddin 320 Neil 300 167
Optimus 200G Bart 200 160
Phoebus 615 Paul 100 109
Lilor Table lamp Henry 150 94
Vapalux E41 Neil 300 99
Petromax 883 Henry 300 151
Phoebus 665 Paul 500 282
Petromax 829 Neil 500 255
Geniol 150 Henry 150 123
Vapalux E41 Malcolm 300 126
Tilley X246 Ian 300 115
Vapalux E41 Kenny 300 167
Coleman 237 Malcolm 500 260
Coleman 237 (1) Neil 500 189
Coleman 237 (2) Neil 500 130
Nitehawk 720 Neil 1000 360
Coleman 252A Henry 200 106
Optimus 550 Neil 500 205
Optimus 1200 Paul 200 175
Petromax 350 Arjan 350 210
Tilley SDR Bart 400 179
Gloria 100 Henry 250 ? 107
Aschwanden 551LD Henry 300 246
Imber Research 310 Neil 300 131
Hipolito H502 Ross 500 290

Neil.

 

To my experience it depends largely on which mantles are used. The non-radioactive ones that can be bought nowadays are usually less bright than the radioactive ones that were sold in the 1950's and 1960's.
Even the brightest ones of today (e.g. Gold-Top 1111) are not achieving the light output to what the lanterns were initially rated.
I've seen 500CP lanterns running incredibly bright with those old mantles, and they can light a large area when hanging high enough. However, I've no idea what this light output would have meant in comparison to a Tungsten light bulb. And with the naked eye it's dfficult to judge because the Tungsten wire appears much smaller than the larger emitting area of a mantle, thus increasing the light intensity (radiation density in a given area) at the same given overall luminous flux.

 

With all the discussions above, i think perhaps Lumens is the key measurement we should all go by? I think lumens measures the area the light actually lands on or within a set area, whereas watts is not actually a measure of light, just power used, but we all used it as a handy yardstick to gauge an electric bulbs light. With LED lights these days the whole wattage thing is totally redundant

 

Lumens would be perhaps correct and the modern way but since the vast majority of the lamps we play with were rated in old fashioned candle power when they were sold staying with cp or HK as a light power does make some sense. My photometer actually has a Lux meter as the measurement instrument. 1 Lux is one candela at 1 meter and since a candela is almost the same as 1 candle power and I measure at 1 meter distance from the source I get direct cp readings within about 1%. The game is complicated because different counties used different standards. In Germany they used Hefnerkerze or Hefner Candles and you will see on older lamps this marked on Petromax typically as 500HK. 1 hk is 0.91 cp and in fact 500hk is therefore about 450cp. The French Bougie Decemale is 0.938HK. The Candela is 0.917HK and the international standard candle 0.91HK. ::Neil::

 

Hummm, no one is singing off the same sheet of music.....

 

Well no they weren't but for practical purposes it makes little difference since they are all within 10%. It helps perhaps when reading old catalogues to realise that HK is about 10% less in cp and bougie is about 5% less in cp. All these were kinda vague anyway because in the 1920s and earlier most manufacturers lied about their product's performance. A pretty safe bet since most customers would have had no idea what these terms actually meant and certainly had no means of checking the measurement. Oh yes and I meant to say earlier that as far as I can tell the Swedish term "Normalljus" translates directly as candlePower. You will see this in Swedish catalogues sometimes abreviated to nljus or nlj. ::Neil::

 

We did probaly have pretty good candles back then, because one candle is said to put out appr. two "Normalljus".

"Normalljus" translate as "normal light".
Some would like to translate it as "normal candle", but that is hard to accept when they claimed that one lit candle produce about two "Normalljus".

(Ljus means light but could also be used in short for candle. Full word would be "Stearinljus".)

 

Yes I read that and I also thought you must have pretty good candles. I found several references to suggest it was 1cp. Interesting that Sweden seems to have adopted a Britsh standard when I might have expected them to adopt the German HK. Probably to do with Condrup being a major customer and exporting Primus to the Empire. ::Neil::

 

I measured my Petromax 500CP at 50cm with a new Petromax mantle and I got 800-850 lumens which is the same as a 60 Watt incandescent light bulb. I was measuring horizontal light at the globe level.

Distance plays a big role, I could get over 1100 lumen next to the globe (which is 100 Watt equivalent) and under 200 lumen further away.

 

What instrument are you using? Distance is critical because measured light power varies by the square of distance. To get cp you need to measure at exactly 1 meter. Also you have to eliminate all ambient and reflected light. This is not easy and you need a non reflective dark room or a photometer which eliminates reflections. In a normal room reflections can affect the reading by as much as 20% or more. ::Neil::

 

Couldn't the power output of 400W include both heat and light?

 

No, definitely not.
The "400 Watts" tale is just advertising language, incorrectly cited, then thought to be reality by people who do not know better.

A Petromax 500 HK has a power output of 1200...1300 Watts. And that is all.
All the power is put out as heat as incandescent mantles give light by being heated.

Erik

 

Quite right and in fact I would have thought a 500cp lamp would be more and perhaps as much as 2000 watts. Tilley at 300cp make about 1250w. ::Neil::

 

I did some figures along similar lines to Neil, and got similar (though not so repeatable) results as my light metering setup was much more crude. One thing though, working on the basis that a 300CP Tilley lamp burns for 10 hours on 1.25 pints of paraffin (the figure quoted in Jim Dick's book) makes the thermal input 731 watts, assuming the standard calorific value of paraffin at 10.23kWh/l.

This poses another conundrum. The Tilley R1 radiator uses the same vapouriser and, again, is quoted at burning paraffin at the same rate as the lamps, i.e. around 0.125 pints per hour giving 731 Watts. Yet Tilley claim a heat output of 1.25kW! How?

There must be a fixed relationship between fuel throughput, orifice diameter, heat output and candlepower rating. The only figure I've ever seen quoted (I think by Neil) is that the orifice diameter of a "300CP" lamp is 0.007".

I've never managed to measure more than 125CP from any of my Tilley lamps. This tends to confirm that the old thoriated mantles gave more light output than modern mantles, for the same heat input.

Phil

 

Well I guess we have to understand that like a lot of lamp companies Tiley lied about their lamp and heater preformances. I suspect the quoted figures are the design ideal and with production variations plenty escaped the factory that were below par. Tilley before about 2000 rated the lamps at 300cp and I have measured several 1950s and earlier lamps at near that figure. Very few X246Bs will achieve half that but I did find one in 1999 that I was fettling for a friend at work that measured 243cp and I have a NIB early 1950s X246 that reached 264cp. Both those lamps would have made the 300 with a little more pressure. So they would do it with a new burner set up in the 1950s and just now and then a much later lamp has a "faulty" burner which will also do the rated power.

As for the heaters I can't comment because I have no way of measuring heat output. I have always assuumed a 9 hour burn for the lamps which would mean an output more like 1KW perhaps. Maybe Tilley were assuming a better fuel but I rather doubt it would have been that much better. ::Neil::

 

Maybe the reflector turns the heat to a 180 degree angle therefore doubling the wattage in that zone and cutting it to almost zero in the other zone, so they simply doubled the power output?

 

Well if they did that then that is perverted science for the gullible because you can't get more power out of the fuel than the calorific value. ::Neil::

 

Absolutely correct, Neil. Having said that, Tilley did manage a claimed 5000 reflected candle power from a 200cp burner in the FL6!

Assuming complete combustion, to all intents and purposes, all the chemical energy in the fuel will be converted to heat, light and sound. In the real world i.e. here and now, energy can neither be created nor destroyed...

 

@David Shouksmith,
...but that should be correct!
If they had used lumens (lm) it would have meant the overall light output or the total "luminous power", or the total "luminous flux" of that light source, which is obviously limited to the power of combustion (or wattage) of the light source.

But they used the units CP, HK (or today's candela (cd)), which is "luminous power per unit solid angle emitted by a point light source in a particular direction", which of course can be greatly amplified by just adding a reflector. So the equation is:
1 lm = 1 cd ⋅ sr (sr = steradians, solid angle)
and a full sphere covers 4pi steradians. That means, if you reduce the solid angle at a given luminous flux (by e.g. a reflector) you will reciprocally increase the luminous power to that same reduced solid angle.

Similarly, the unit Lux (lx) means one lumen per square metre, which also corresponds to a luminous power to that area, which at a point shaped light source (like a mantle) then of course depends on the distance at which you measure.

You can get a bit of the background from Wikipedia here:
Lumen (unit) - Wikipedia
Candela - Wikipedia