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Measuring power consumption of immersion heater?
I recently bought Aldi's power meter, which I have found quite instructive - I was surprised that my Sky box and TV took 20 watts each in standby. This led me to wonder how I could measure the power consumption of our 2 immersion heaters. I assume it is dangerous, probably illegal, to fit a power socket in the bathroom. Is there any simple way of getting round this? |
Measuring power consumption of immersion heater?
Timothy Murphy wrote:
Is there any simple way of getting round this? A few: 1) Look at the ratings plate 2) Clamp meter 3) Using the lekky meter -- Cheers, John. /================================================== ===============\ | Internode Ltd - http://www.internode.co.uk | |-----------------------------------------------------------------| | John Rumm - john(at)internode(dot)co(dot)uk | \================================================= ================/ |
Measuring power consumption of immersion heater?
In article ,
Timothy Murphy writes: I recently bought Aldi's power meter, which I have found quite instructive - I was surprised that my Sky box and TV took 20 watts each in standby. Set top boxes are imfamous for not reducing power consumption in standby mode, and are probably largely resposible for the current standby hysteria. Most modern TV's reduce their standby power to negligable levels in standby mode or they can't be sold in a number of countries. How old is your TV? -- Andrew Gabriel [email address is not usable -- followup in the newsgroup] |
Measuring power consumption of immersion heater?
Andrew Gabriel wrote:
In article , Timothy Murphy writes: I recently bought Aldi's power meter, which I have found quite instructive - I was surprised that my Sky box and TV took 20 watts each in standby. Set top boxes are imfamous for not reducing power consumption in standby mode, and are probably largely resposible for the current standby hysteria. Most modern TV's reduce their standby power to negligable levels in standby mode or they can't be sold in a number of countries. How old is your TV? Also, as commented at the time, the Aldi power meter does not look like it understand power factors. So lightly loaded switched mode supplies (which often exhibit very poor power factors) could over-read significantly. -- Cheers, John. /================================================== ===============\ | Internode Ltd - http://www.internode.co.uk | |-----------------------------------------------------------------| | John Rumm - john(at)internode(dot)co(dot)uk | \================================================= ================/ |
Measuring power consumption of immersion heater?
On 4 Oct, 09:04, John Rumm wrote:
Also, as commented at the time, the Aldi power meter does not look like it understand power factors. So lightly loaded switched mode supplies (which often exhibit very poor power factors) could over-read significantly. Are you suggesting that the Aldi power meter is not a power meter? T. |
Measuring power consumption of immersion heater?
wrote:
On 4 Oct, 09:04, John Rumm wrote: Also, as commented at the time, the Aldi power meter does not look like it understand power factors. So lightly loaded switched mode supplies (which often exhibit very poor power factors) could over-read significantly. Are you suggesting that the Aldi power meter is not a power meter? No, what I was highlighting is that the write up for it offers no clues as whether it is able to distinguish between real and apparent power consumption[1] - so take readings taken on this sort of kit with a good degree of scepticism. [1] Unlike the Maplin equivalent device for example which measures the power factor of the load and makes allowances for it. Note however that even this one does not work well on small capacitive loads. -- Cheers, John. /================================================== ===============\ | Internode Ltd - http://www.internode.co.uk | |-----------------------------------------------------------------| | John Rumm - john(at)internode(dot)co(dot)uk | \================================================= ================/ |
Measuring power consumption of immersion heater?
On 4 Oct, 11:08, John Rumm wrote:
wrote: On 4 Oct, 09:04, John Rumm wrote: Also, as commented at the time, the Aldi power meter does not look like it understand power factors. So lightly loaded switched mode supplies (which often exhibit very poor power factors) could over-read significantly. Are you suggesting that the Aldi power meter is not a power meter? No, what I was highlighting is that the write up for it offers no clues as whether it is able to distinguish between real and apparent power consumption[1] - so take readings taken on this sort of kit with a good degree of scepticism. [1] Unlike the Maplin equivalent device for example which measures the power factor of the load and makes allowances for it. Note however that even this one does not work well on small capacitive loads. I'm afraid I don't fully understand. A device consuming 20W will do so irrespective of the power factor. A power meter should measure this power, just as my electricity meter does. What does making allowances for pf mean? T |
Measuring power consumption of immersion heater?
John Rumm wrote:
Also, as commented at the time, the Aldi power meter does not look like it understand power factors. So lightly loaded switched mode supplies (which often exhibit very poor power factors) could over-read significantly. Have you seen the Aldi power meter? It actually seems quite sophisticated, certainly more so than the Maplin meter (which I have also used). Eg the manual is difficult to follow ... |
Measuring power consumption of immersion heater?
Andrew Gabriel wrote:
I recently bought Aldi's power meter, which I have found quite instructive - I was surprised that my Sky box and TV took 20 watts each in standby. Set top boxes are imfamous for not reducing power consumption in standby mode, and are probably largely resposible for the current standby hysteria. Most modern TV's reduce their standby power to negligable levels in standby mode or they can't be sold in a number of countries. How old is your TV? It's a Sony 26in TV (not flat screen), about 8 years old I think. On re-checking I see that it only takes 12 watts in standby, while the Grundig Sky box takes 30 watts. Actually, I don't see any way of putting the Sky box on standy - this is the consumption with the TV off. |
Measuring power consumption of immersion heater?
John Rumm wrote:
Are you suggesting that the Aldi power meter is not a power meter? No, what I was highlighting is that the write up for it offers no clues as whether it is able to distinguish between real and apparent power consumption[1] - so take readings taken on this sort of kit with a good degree of scepticism. [1] Unlike the Maplin equivalent device for example which measures the power factor of the load and makes allowances for it. Note however that even this one does not work well on small capacitive loads. Actually, I see that the Aldi meter does show the power factor - 0.99 in this case. |
Measuring power consumption of immersion heater?
John Rumm wrote:
Is there any simple way of getting round this? A few: 1) Look at the ratings plate 2) Clamp meter 3) Using the lekky meter I want to calculate power consumption during over a period, so I'm not sure if these will work. Incidentally, how does a Lecky (I assume that is what is meant) meter work? Is it reasonably accurate? |
Measuring power consumption of immersion heater?
Timothy Murphy wrote:
[1] Unlike the Maplin equivalent device for example which measures the power factor of the load and makes allowances for it. Note however that even this one does not work well on small capacitive loads. Actually, I see that the Aldi meter does show the power factor - 0.99 in this case. OK, the one that someone linked to a week or so ago did not have any mention of it in the write up - and there was nothing obvious on the display of the unit pictured. If it does adjust for the PF then it should give you more accurate readings. -- Cheers, John. /================================================== ===============\ | Internode Ltd - http://www.internode.co.uk | |-----------------------------------------------------------------| | John Rumm - john(at)internode(dot)co(dot)uk | \================================================= ================/ |
Measuring power consumption of immersion heater?
wrote:
Are you suggesting that the Aldi power meter is not a power meter? No, what I was highlighting is that the write up for it offers no clues as whether it is able to distinguish between real and apparent power consumption[1] - so take readings taken on this sort of kit with a good degree of scepticism. I'm afraid I don't fully understand. A device consuming 20W will do so irrespective of the power factor. A power meter should measure this power, just as my electricity meter does. What does making allowances for pf mean? The simplest ones measure the line voltage and the current flow and from that deduce the power consumption. On kit with non unity power factors this will end up reporting the VA rating rather than the real power consumption. -- Cheers, John. /================================================== ===============\ | Internode Ltd - http://www.internode.co.uk | |-----------------------------------------------------------------| | John Rumm - john(at)internode(dot)co(dot)uk | \================================================= ================/ |
Measuring power consumption of immersion heater?
Timothy Murphy wrote:
John Rumm wrote: Also, as commented at the time, the Aldi power meter does not look like it understand power factors. So lightly loaded switched mode supplies (which often exhibit very poor power factors) could over-read significantly. Have you seen the Aldi power meter? It actually seems quite sophisticated, certainly more so than the Maplin meter (which I have also used). Eg the manual is difficult to follow ... I saw the one that someone linked to a little while back (can't follow the link now since they seem to have removed the special offer) - that one looked fairly basic and did not mention an ability to measure the power factor. Yours may be better - or the advert may have left out a bunch of features. -- Cheers, John. /================================================== ===============\ | Internode Ltd - http://www.internode.co.uk | |-----------------------------------------------------------------| | John Rumm - john(at)internode(dot)co(dot)uk | \================================================= ================/ |
Measuring power consumption of immersion heater?
On 4 Oct, 18:53, John Rumm wrote:
wrote: Are you suggesting that the Aldi power meter is not a power meter? No, what I was highlighting is that the write up for it offers no clues as whether it is able to distinguish between real and apparent power consumption[1] - so take readings taken on this sort of kit with a good degree of scepticism. I'm afraid I don't fully understand. A device consuming 20W will do so irrespective of the power factor. A power meter should measure this power, just as my electricity meter does. What does making allowances for pf mean? The simplest ones measure the line voltage and the current flow and from that deduce the power consumption. On kit with non unity power factors this will end up reporting the VA rating rather than the real power consumption. If that's the case it isn't a power meter, shouldn't be called one, and you were saying it wasn't. T |
Measuring power consumption of immersion heater?
On 4 Oct, 18:21, Timothy Murphy wrote:
John Rumm wrote: Are you suggesting that the Aldi power meter is not a power meter? No, what I was highlighting is that the write up for it offers no clues as whether it is able to distinguish between real and apparent power consumption[1] - so take readings taken on this sort of kit with a good degree of scepticism. [1] Unlike the Maplin equivalent device for example which measures the power factor of the load and makes allowances for it. Note however that even this one does not work well on small capacitive loads. Actually, I see that the Aldi meter does show the power factor - 0.99 in this case. When you measure the power factor, are you measuring it for the device in question, or are you measuring the average for the neighbourhood? T |
Measuring power consumption of immersion heater?
In message , Timothy Murphy
writes Actually, I don't see any way of putting the Sky box on standy what happens when you press the button at the top right of the remote control? -- Si |
Measuring power consumption of immersion heater?
In article ,
John Rumm writes: wrote: I'm afraid I don't fully understand. A device consuming 20W will do so irrespective of the power factor. A power meter should measure this power, just as my electricity meter does. What does making allowances for pf mean? The simplest ones measure the line voltage and the current flow and from that deduce the power consumption. On kit with non unity power factors this will end up reporting the VA rating rather than the real power consumption. There's an even simpler one available which measures only current (using a clamp-on current transformer), and assumes the mains voltage. -- Andrew Gabriel [email address is not usable -- followup in the newsgroup] |
Measuring power consumption of immersion heater?
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Measuring power consumption of immersion heater?
On 4 Oct, 21:23, (Andrew Gabriel) wrote:
In article om, writes: When you measure the power factor, are you measuring it for the device in question, or are you measuring the average for the neighbourhood? A plug-in device can only measure it for the load running through it. Are you suggesting it somehow compensates for the power factor of the supply automatically? T |
Measuring power consumption of immersion heater?
Si wrote:
Actually, I don't see any way of putting the Sky box on standby what happens when you press the button at the top right of the remote control? This doesn't seem to affect power consumption in the slightest - it remains just under 30 watts (with the TV off), though the light on the Sky box turns from green to red. |
Measuring power consumption of immersion heater?
In article ,
Timothy Murphy writes: Andrew Gabriel wrote: I recently bought Aldi's power meter, which I have found quite instructive - I was surprised that my Sky box and TV took 20 watts each in standby. Set top boxes are imfamous for not reducing power consumption in standby mode, and are probably largely resposible for the current standby hysteria. Most modern TV's reduce their standby power to negligable levels in standby mode or they can't be sold in a number of countries. How old is your TV? It's a Sony 26in TV (not flat screen), about 8 years old I think. On re-checking I see that it only takes 12 watts in standby, Just checked a 2 year old Panasonic LCD, and it's 0.5W standby. It doesn't have a TCO'03 sticker on it, but this brings it within the TCO'03 requirements (1W max standby) and thus able to be sold in some countries where that's a requirement. while the Grundig Sky box takes 30 watts. That seems an awful lot, or the power meter is not handling loads with power factor 1 correctly. -- Andrew Gabriel [email address is not usable -- followup in the newsgroup] |
Measuring power consumption of immersion heater?
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Measuring power consumption of immersion heater?
On 5 Oct, 23:51, Rumble wrote:
wrote: snip When you measure the power factor, are you measuring it for the device in question, or are you measuring the average for the neighbourhood? A plug-in device can only measure it for the load running through it. Are you suggesting it somehow compensates for the power factor of the supply automatically? T Is this a trick question? The supply doesn't have a power factor; only the load has a power factor. It wasn't supposed to be a trick question. The supply has a power factor by definition. The question is whether it equals unity or not. Are you implying that a domestic supply is guaranteed to have a power factor of 1? T |
Measuring power consumption of immersion heater?
Rumble wrote:
wrote: snip When you measure the power factor, are you measuring it for the device in question, or are you measuring the average for the neighbourhood? A plug-in device can only measure it for the load running through it. Are you suggesting it somehow compensates for the power factor of the supply automatically? T Is this a trick question? The supply doesn't have a power factor; only the load has a power factor. Its an odd question granted, although you could argue that the supply may have a distorted voltage waveform as a result of local high current non-power factor corrected loads. This (and other things) will introduce harmonic noise to the supply. The result would be lowering of the effective power factor seen at the load. -- Cheers, John. /================================================== ===============\ | Internode Ltd - http://www.internode.co.uk | |-----------------------------------------------------------------| | John Rumm - john(at)internode(dot)co(dot)uk | \================================================= ================/ |
Measuring power consumption of immersion heater?
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Measuring power consumption of immersion heater?
On 6 Oct, 09:23, (Andrew Gabriel) wrote:
In article . com, writes: On 5 Oct, 23:51, Rumble wrote: wrote: snip When you measure the power factor, are you measuring it for the device in question, or are you measuring the average for the neighbourhood? A plug-in device can only measure it for the load running through it. Are you suggesting it somehow compensates for the power factor of the supply automatically? Is this a trick question? The supply doesn't have a power factor; only the load has a power factor. It wasn't supposed to be a trick question. The supply has a power factor by definition. In which case you'll have to give your definition, because it is meaningless with the standard definition of power factor. -- Well, it's not _my_ definition it's _the_ definition. Perhaps you could Google for one? T |
Measuring power consumption of immersion heater?
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Measuring power consumption of immersion heater?
wrote in message ups.com... On 5 Oct, 23:51, Rumble wrote: wrote: snip When you measure the power factor, are you measuring it for the device in question, or are you measuring the average for the neighbourhood? A plug-in device can only measure it for the load running through it. Are you suggesting it somehow compensates for the power factor of the supply automatically? T Is this a trick question? The supply doesn't have a power factor; only the load has a power factor. It wasn't supposed to be a trick question. The supply has a power factor by definition. The question is whether it equals unity or not. Are you implying that a domestic supply is guaranteed to have a power factor of 1? They are charging me per kwHr so they had better have the correct power factor. |
Measuring power consumption of immersion heater?
On 6 Oct, 18:04, "dennis@home" wrote:
wrote in message ups.com... On 5 Oct, 23:51, Rumble wrote: wrote: snip When you measure the power factor, are you measuring it for the device in question, or are you measuring the average for the neighbourhood? A plug-in device can only measure it for the load running through it. Are you suggesting it somehow compensates for the power factor of the supply automatically? T Is this a trick question? The supply doesn't have a power factor; only the load has a power factor. It wasn't supposed to be a trick question. The supply has a power factor by definition. The question is whether it equals unity or not. Are you implying that a domestic supply is guaranteed to have a power factor of 1? They are charging me per kwHr so they had better have the correct power factor. If they are charging per kWh, power factor is irrelevant. T |
Measuring power consumption of immersion heater?
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Measuring power consumption of immersion heater?
On Fri, 05 Oct 2007 17:17:00 -0700, wrote:
On 5 Oct, 23:51, Rumble wrote: wrote: snip When you measure the power factor, are you measuring it for the device in question, or are you measuring the average for the neighbourhood? A plug-in device can only measure it for the load running through it. Are you suggesting it somehow compensates for the power factor of the supply automatically? T Is this a trick question? The supply doesn't have a power factor; only the load has a power factor. It wasn't supposed to be a trick question. The supply has a power factor by definition. The question is whether it equals unity or not. Are you implying that a domestic supply is guaranteed to have a power factor of 1? T ????? Not so! The numerical power factor eg 1, 0.9 etc - is a measure of the phase angle between the LOAD current and the applied voltage. It is also the measurement of the ratio of real power and apparent power or the ratio of watts (W) to voltamperes (VA). Look at Google: http://www.google.co.uk/search?hl=en...ition&ct=title The power companies worry about the overall power factor of the supply for obvious reasons. |
Measuring power consumption of immersion heater?
On 6 Oct, 16:23, (Andrew Gabriel) wrote:
In article .com, writes: On 6 Oct, 09:23, (Andrew Gabriel) wrote: In article . com, writes: On 5 Oct, 23:51, Rumble wrote: wrote: snip When you measure the power factor, are you measuring it for the device in question, or are you measuring the average for the neighbourhood? A plug-in device can only measure it for the load running through it. Are you suggesting it somehow compensates for the power factor of the supply automatically? Is this a trick question? The supply doesn't have a power factor; only the load has a power factor. It wasn't supposed to be a trick question. The supply has a power factor by definition. In which case you'll have to give your definition, because it is meaningless with the standard definition of power factor. Well, it's not _my_ definition it's _the_ definition. Perhaps you could Google for one? I am very familiar with the standard definition which applies to loads, having designed and built a true power meter myself some 25 years ago, and having explained power factor many times here over the years. You'll have to point out a definition of power factor of a supply, as that's not covered by the standard definition. Google draws a blank too. The only related thing I could think of would be a measure of the worse power factor load a particular supply can drive, but even that's meaningless as supplies are rated in [k]VA and in many cases can handle worst case loads with a PF of zero. -- Andrew Gabriel [email address is not usable -- followup in the newsgroup] I'm clearly trying to discover whether the power factor I measure is affected in any way by the electricity network. If you put a purely resistive load across the supply coming into your house, are you guaranteed to measure no phase difference between the voltage and the current? If the phase difference is zero, then the power factor of your supply is 1. There's a whole load of stuff on the web about the lengths the National Grid go to power factor correct their supply. Perhaps you should ring them to tell them they are wasting their time? T |
Measuring power consumption of immersion heater?
wrote in message ups.com... I'm clearly trying to discover whether the power factor I measure is affected in any way by the electricity network. If you put a purely resistive load across the supply coming into your house, are you guaranteed to measure no phase difference between the voltage and the current? If the phase difference is zero, then the power factor of your supply is 1. If the load is resistive there is never any phase difference between current and voltage it is governed by ohms law.. |
Measuring power consumption of immersion heater?
On 6 Oct, 19:52, Adrian C wrote:
Power factor of the supply? What's that then? It's something the National Grid are obliged to keep within certain limits: 0.85 lagging - 0.95 leading. T |
Measuring power consumption of immersion heater?
On 6 Oct, 20:00, John Evans wrote:
On Fri, 05 Oct 2007 17:17:00 -0700, wrote: On 5 Oct, 23:51, Rumble wrote: wrote: It wasn't supposed to be a trick question. The supply has a power factor by definition. The question is whether it equals unity or not. Are you implying that a domestic supply is guaranteed to have a power factor of 1? T ????? Not so! The numerical power factor eg 1, 0.9 etc - is a measure of the phase angle between the LOAD current and the applied voltage. It is also the measurement of the ratio of real power and apparent power or the ratio of watts (W) to voltamperes (VA). .... The power companies worry about the overall power factor of the supply for obvious reasons. You have just contradicted yourself. T |
Measuring power consumption of immersion heater?
wrote:
I'm clearly trying to discover whether the power factor I measure is affected in any way by the electricity network. If you put a purely IIUC, it is not effected by the network as such, although it may be affected by other users of it. resistive load across the supply coming into your house, are you guaranteed to measure no phase difference between the voltage and the current? If the phase difference is zero, then the power factor of your supply is 1. With purely resistive loads then it is not an issue. For loads with a reactive component then the reactive component will typically be the major influence on the power factor. However the quality of the waveform that you are supplied with can further influence it. There's a whole load of stuff on the web about the lengths the National Grid go to power factor correct their supply. Perhaps you should ring them to tell them they are wasting their time? They go to some effort to mitigate the effects their users have on the supply. A big industrial user (or the cumulative effect of many smaller ones) pulling large currents from the supply that are not phase aligned with the voltage, can end up distorting the supply waveform. This leaves the waveform non sinusoidal and hence introduces other frequency components into it. These will interact with the reactive elements of any load differently than would a plain 50Hz supply. -- Cheers, John. /================================================== ===============\ | Internode Ltd - http://www.internode.co.uk | |-----------------------------------------------------------------| | John Rumm - john(at)internode(dot)co(dot)uk | \================================================= ================/ |
Measuring power consumption of immersion heater?
wrote:
On 6 Oct, 19:52, Adrian C wrote: Power factor of the supply? What's that then? It's something the National Grid are obliged to keep within certain limits: 0.85 lagging - 0.95 leading. Well sort of... The concept of power factor only really has any meaning when you know the characteristics of the load. With a resistive one, the power factor is 1 regardless of the supply. What the grid are obliged to do is provide a stable supply, and ensure that the required true power output of the generating plant is available to the grid. Obviously this would not be the case if capacity on the network is going to be absorbed by large reactive currents flowing around it. They also need to ensure local voltage stabilisation. The limits you specify above are limits for the *load*. i.e. they must meet certain performance criteria when the connected load lies within those limits. With applied loads outside of these limits they are not required to achieve the same standards. A distribution system itself will also have a number of reactive components within it, like the cables (transmission line effects), and transformers. The effects of these will also need to be compensated for. -- Cheers, John. /================================================== ===============\ | Internode Ltd - http://www.internode.co.uk | |-----------------------------------------------------------------| | John Rumm - john(at)internode(dot)co(dot)uk | \================================================= ================/ |
Measuring power consumption of immersion heater?
wrote:
Not so! The numerical power factor eg 1, 0.9 etc - is a measure of the phase angle between the LOAD current and the applied voltage. It is also the measurement of the ratio of real power and apparent power or the ratio of watts (W) to voltamperes (VA). .... The power companies worry about the overall power factor of the supply for obvious reasons. You have just contradicted yourself. I think he was just being a bit sloppy with terminology. However it is worth remembering that the distribution grid is also part of the load. -- Cheers, John. /================================================== ===============\ | Internode Ltd - http://www.internode.co.uk | |-----------------------------------------------------------------| | John Rumm - john(at)internode(dot)co(dot)uk | \================================================= ================/ |
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