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#1
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Can I put a coffee warmer on a dimmer switch?
Most coffee mug warmers are under-powered. One reviewer on Amazon said
that they were restricted to about 24 watts by law. This one http://www.amazon.com/Bunn-BCW-Warme...1796737&sr=8-3 is made for warming the whole coffee pot. It says it's 120V/15amp. Several of the reviews say that they use it for a single cup, but it keeps it too hot. It only has on/off -- no temperature control. Can I put it on a 300 watt dimmer switch like this? http://www.amazon.com/Lutron-Electro...1799800&sr=8-2 If not, is there a way to ramp the the power down as an external thermostat? |
#2
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Can I put a coffee warmer on a dimmer switch?
Square Peg wrote:
Most coffee mug warmers are under-powered. One reviewer on Amazon said that they were restricted to about 24 watts by law. This one http://www.amazon.com/Bunn-BCW-Warme...1796737&sr=8-3 is made for warming the whole coffee pot. It says it's 120V/15amp. Several of the reviews say that they use it for a single cup, but it keeps it too hot. It only has on/off -- no temperature control. Can I put it on a 300 watt dimmer switch like this? http://www.amazon.com/Lutron-Electro...1799800&sr=8-2 If not, is there a way to ramp the the power down as an external thermostat? Yes. It's a resistive load, just like a light bulb. I find it difficult to believe that 15 amps is correct, that would be 1800 watts which will do far more than warm a coffee pot. If you use the Lutron dimmer, make sure that the warmer is under 300 watts, or get one a bit more robust. |
#3
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Can I put a coffee warmer on a dimmer switch?
"Square Peg" wrote in message ... Most coffee mug warmers are under-powered. One reviewer on Amazon said that they were restricted to about 24 watts by law. This one http://www.amazon.com/Bunn-BCW-Warme...1796737&sr=8-3 is made for warming the whole coffee pot. It says it's 120V/15amp. Several of the reviews say that they use it for a single cup, but it keeps it too hot. It only has on/off -- no temperature control. Can I put it on a 300 watt dimmer switch like this? http://www.amazon.com/Lutron-Electro...1799800&sr=8-2 If not, is there a way to ramp the the power down as an external thermostat? You will probably be disappointed in the results and waste electricity at the same time. The heating elements are designed to perform at a certain voltage. As that decreases so will the heat level, but it will not be on a straight line but rather a drastic curve due to the resistive nature of the elements. Take a look at what happens when a light bulb is dimmed. Not only is the light output diminished, but the color of the light changes as well because they were designed for certain voltage. |
#4
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Can I put a coffee warmer on a dimmer switch?
Boden wrote:
Yes. It's a resistive load, just like a light bulb. I find it difficult to believe that 15 amps is correct, that would be 1800 watts which will do far more than warm a coffee pot. If you use the Lutron dimmer, make sure that the warmer is under 300 watts, or get one a bit more robust. If it's controlled by a thermostat wouldn't lowering the voltage just make it take longer to reach the same temp? |
#5
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Can I put a coffee warmer on a dimmer switch?
"John Grabowski" wrote in message
... "Square Peg" wrote in message ... Most coffee mug warmers are under-powered. One reviewer on Amazon said that they were restricted to about 24 watts by law. This one http://www.amazon.com/Bunn-BCW-Warme...1796737&sr=8-3 is made for warming the whole coffee pot. It says it's 120V/15amp. Several of the reviews say that they use it for a single cup, but it keeps it too hot. It only has on/off -- no temperature control. Can I put it on a 300 watt dimmer switch like this? http://www.amazon.com/Lutron-Electro...1799800&sr=8-2 If not, is there a way to ramp the the power down as an external thermostat? You will probably be disappointed in the results and waste electricity at the same time. The heating elements are designed to perform at a certain voltage. As that decreases so will the heat level, but it will not be on a straight line but rather a drastic curve due to the resistive nature of the elements. Take a look at what happens when a light bulb is dimmed. Not only is the light output diminished, but the color of the light changes as well because they were designed for certain voltage. An incandescent light bulb is inefficient at producing light and it gets much worse as the voltage is reduced, however, it is great at producing heat. If you reduce the voltage on a heating element, it will produce less heat but is still nearly 100% efficient at producing the heat. It does not become less efficient if that is what you were trying to say. |
#6
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Can I put a coffee warmer on a dimmer switch?
"Square Peg" wrote in message
... Most coffee mug warmers are under-powered. One reviewer on Amazon said that they were restricted to about 24 watts by law. This one http://www.amazon.com/Bunn-BCW-Warme...1796737&sr=8-3 is made for warming the whole coffee pot. It says it's 120V/15amp. Several of the reviews say that they use it for a single cup, but it keeps it too hot. It only has on/off -- no temperature control. Can I put it on a 300 watt dimmer switch like this? http://www.amazon.com/Lutron-Electro...1799800&sr=8-2 If not, is there a way to ramp the power down as an external thermostat? OK, I'll bite-- why would you want to?? |
#7
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Can I put a coffee warmer on a dimmer switch?
On Fri, 19 Sep 2008 06:34:10 -0500, "Rick Brandt"
wrote: Boden wrote: Yes. It's a resistive load, just like a light bulb. I find it difficult to believe that 15 amps is correct, that would be 1800 watts which will do far more than warm a coffee pot. If you use the Lutron dimmer, make sure that the warmer is under 300 watts, or get one a bit more robust. If it's controlled by a thermostat wouldn't lowering the voltage just make it take longer to reach the same temp? I don't think it is controlled by a thermostat. I think it is just on. At least, it doesn't appear to have any kind of temperature control. |
#8
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Can I put a coffee warmer on a dimmer switch?
On Fri, 19 Sep 2008 06:11:22 -0400, "John Grabowski"
wrote: "Square Peg" wrote in message .. . Most coffee mug warmers are under-powered. One reviewer on Amazon said that they were restricted to about 24 watts by law. This one http://www.amazon.com/Bunn-BCW-Warme...1796737&sr=8-3 is made for warming the whole coffee pot. It says it's 120V/15amp. Several of the reviews say that they use it for a single cup, but it keeps it too hot. It only has on/off -- no temperature control. Can I put it on a 300 watt dimmer switch like this? http://www.amazon.com/Lutron-Electro...1799800&sr=8-2 If not, is there a way to ramp the the power down as an external thermostat? You will probably be disappointed in the results and waste electricity at the same time. The heating elements are designed to perform at a certain voltage. As that decreases so will the heat level, but it will not be on a straight line but rather a drastic curve due to the resistive nature of the elements. It's been a long time since college physics, so I did a little research. I'm sure the real world is more complicated than this, but I think the theory is that power = voltage x current P = IV Since voltage = current x resistance, V = IR power is P = (V**2)/R Heat is just power over time H = Pt or H = (V**2)t/R It looks like you are partially correct. (Right conclusion, wrong reason?) If heat varies with the square of the voltage, then one half the voltage will produce one quarter the heat. I already have one of those Lutron cord dimmers. In fact I have one sitting right here on my desk attached to the desk lamp. The little slider has about one inch of travel, so I would be able to just nudge it a bit from full on. If I can cut the voltage by 10% (x .9), the heat should be cut by 19% (x .81). If the warmer, which is designed to heat a 10-cup coffee pot, is heating my 10 oz cup of tea too much, I ought to be able to find a good reduction. Take a look at what happens when a light bulb is dimmed. Not only is the light output diminished, but the color of the light changes as well because they were designed for certain voltage. I don't notice the color of my desk lamp changing that much, if at all. Color is just frequency, right? Don't those little photons come off a particular material as some frequency that depends on the material? It seems to me that with less voltage, fewer photons will come off, but at the same frequency. I could be wrong. |
#9
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Can I put a coffee warmer on a dimmer switch?
On Fri, 19 Sep 2008 12:16:32 GMT, "JohnR66" wrote:
"John Grabowski" wrote in message ... "Square Peg" wrote in message ... Most coffee mug warmers are under-powered. One reviewer on Amazon said that they were restricted to about 24 watts by law. This one http://www.amazon.com/Bunn-BCW-Warme...1796737&sr=8-3 is made for warming the whole coffee pot. It says it's 120V/15amp. Several of the reviews say that they use it for a single cup, but it keeps it too hot. It only has on/off -- no temperature control. Can I put it on a 300 watt dimmer switch like this? http://www.amazon.com/Lutron-Electro...1799800&sr=8-2 If not, is there a way to ramp the the power down as an external thermostat? You will probably be disappointed in the results and waste electricity at the same time. The heating elements are designed to perform at a certain voltage. As that decreases so will the heat level, but it will not be on a straight line but rather a drastic curve due to the resistive nature of the elements. Take a look at what happens when a light bulb is dimmed. Not only is the light output diminished, but the color of the light changes as well because they were designed for certain voltage. An incandescent light bulb is inefficient at producing light and it gets much worse as the voltage is reduced, however, it is great at producing heat. If you reduce the voltage on a heating element, it will produce less heat but is still nearly 100% efficient at producing the heat. It does not become less efficient if that is what you were trying to say. That would be my guess as well. I'm not too worried about the efficiency curve or achieving 10 decimal places of accuracy on the temperature. I'm mainly curious about (a) if it will work at all and (b) it if will damage the unit. |
#10
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Can I put a coffee warmer on a dimmer switch?
On Sep 19, 12:23*am, Square Peg wrote:
Most coffee mug warmers are under-powered. One reviewer on Amazon said that they were restricted to about 24 watts by law. This one http://www.amazon.com/Bunn-BCW-Warme.../B00023WAS0/re... is made for warming the whole coffee pot. It says it's 120V/15amp. Several of the reviews say that they use it for a single cup, but it keeps it too hot. It only has on/off -- no temperature control. Can I put it on a 300 watt dimmer switch like this? http://www.amazon.com/Lutron-Electro...-300H-WH/dp/B0... If not, is there a way to ramp the the power down as an external thermostat? It will work but if the warmer pulls more than the dimmer spec it will burn out the dimmer, 15a is an expensive dimmer,Ive never seen more than 1000w for 50$ |
#11
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Can I put a coffee warmer on a dimmer switch?
Square Peg wrote:
On Fri, 19 Sep 2008 06:11:22 -0400, "John Grabowski" wrote: "Square Peg" wrote in message . .. Most coffee mug warmers are under-powered. One reviewer on Amazon said that they were restricted to about 24 watts by law. This one http://www.amazon.com/Bunn-BCW-Warme...1796737&sr=8-3 is made for warming the whole coffee pot. It says it's 120V/15amp. Several of the reviews say that they use it for a single cup, but it keeps it too hot. It only has on/off -- no temperature control. Can I put it on a 300 watt dimmer switch like this? http://www.amazon.com/Lutron-Electro...1799800&sr=8-2 If not, is there a way to ramp the the power down as an external thermostat? You will probably be disappointed in the results and waste electricity at the same time. The heating elements are designed to perform at a certain voltage. As that decreases so will the heat level, but it will not be on a straight line but rather a drastic curve due to the resistive nature of the elements. It's been a long time since college physics, so I did a little research. I'm sure the real world is more complicated than this, but I think the theory is that power = voltage x current P = IV Since voltage = current x resistance, V = IR power is P = (V**2)/R Heat is just power over time H = Pt or H = (V**2)t/R It looks like you are partially correct. (Right conclusion, wrong reason?) If heat varies with the square of the voltage, then one half the voltage will produce one quarter the heat. I already have one of those Lutron cord dimmers. In fact I have one sitting right here on my desk attached to the desk lamp. The little slider has about one inch of travel, so I would be able to just nudge it a bit from full on. If I can cut the voltage by 10% (x .9), the heat should be cut by 19% (x .81). If the warmer, which is designed to heat a 10-cup coffee pot, is heating my 10 oz cup of tea too much, I ought to be able to find a good reduction. Take a look at what happens when a light bulb is dimmed. Not only is the light output diminished, but the color of the light changes as well because they were designed for certain voltage. I don't notice the color of my desk lamp changing that much, if at all. Color is just frequency, right? Don't those little photons come off a particular material as some frequency that depends on the material? It seems to me that with less voltage, fewer photons will come off, but at the same frequency. I could be wrong. Your analysis is correct as far as it goes, but you need to recognize that the resistance is not a constant. It is a function of temperature. Usually the resistance of heating elements increase as they get hot. The frequency (1/wavelength) is a function of the energy of those photons. Hotter materials emit more energetic photons that have shorter wavelenths. Put a piece of steel in a flame and watch the color go from brown to purple to blue to red to yellow, etc as it moves from about 500F to 2300F. Boden |
#12
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Can I put a coffee warmer on a dimmer switch?
Square Peg wrote:
Most coffee mug warmers are under-powered. One reviewer on Amazon said that they were restricted to about 24 watts by law. This one http://www.amazon.com/Bunn-BCW-Warme...1796737&sr=8-3 is made for warming the whole coffee pot. It says it's 120V/15amp. Several of the reviews say that they use it for a single cup, but it keeps it too hot. It only has on/off -- no temperature control. Can I put it on a 300 watt dimmer switch like this? http://www.amazon.com/Lutron-Electro...1799800&sr=8-2 If not, is there a way to ramp the the power down as an external thermostat? I seriously doubt the veracity of that "120V/15 amp" rating, which I did see listed as a "spec" on a couple of other seller's websites. I have a Bunn coffeemaker and I just measured the current draw of the warming plate on it at 1.05 amps. (I made sure that the main water heating element's thermostat was OFF at that time of course.) So, if approximately 120 watts will keep a full caraffe of coffee at proper drinking temperature on my Bunn coffeemaker, the stand alone Bunn warmers probably draw no more than the "built in" ones. Thus, that 300 watt dimmer ought to do just fine after you find the right slider setting to keep a single cup hot. Go for it! Jeff -- Jeffry Wisnia (W1BSV + Brass Rat '57 EE) The speed of light is 1.98*10^14 fathoms per fortnight. |
#13
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Can I put a coffee warmer on a dimmer switch?
On Fri, 19 Sep 2008 08:08:58 -0700 (PDT), ransley
wrote: On Sep 19, 12:23*am, Square Peg wrote: Most coffee mug warmers are under-powered. One reviewer on Amazon said that they were restricted to about 24 watts by law. This one http://www.amazon.com/Bunn-BCW-Warme.../B00023WAS0/re... is made for warming the whole coffee pot. It says it's 120V/15amp. Several of the reviews say that they use it for a single cup, but it keeps it too hot. It only has on/off -- no temperature control. Can I put it on a 300 watt dimmer switch like this? http://www.amazon.com/Lutron-Electro...-300H-WH/dp/B0... If not, is there a way to ramp the the power down as an external thermostat? It will work but if the warmer pulls more than the dimmer spec it will burn out the dimmer, 15a is an expensive dimmer,Ive never seen more than 1000w for 50$ I was worried about that. If it draws 15A, that would be 1650 watts, no? If it does burn out the dimmer, will it cause a fire or melt? I could try it in the garage or back yard. |
#14
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Can I put a coffee warmer on a dimmer switch?
On Sep 19, 8:01*pm, Jeff Wisnia
wrote: Square Peg wrote: Most coffee mug warmers are under-powered. One reviewer on Amazon said that they were restricted to about 24 watts by law. This one http://www.amazon.com/Bunn-BCW-Warme.../B00023WAS0/re... is made for warming the whole coffee pot. It says it's 120V/15amp. Several of the reviews say that they use it for a single cup, but it keeps it too hot. It only has on/off -- no temperature control. Can I put it on a 300 watt dimmer switch like this? http://www.amazon.com/Lutron-Electro...-300H-WH/dp/B0... If not, is there a way to ramp the the power down as an external thermostat? I seriously doubt the veracity of that "120V/15 amp" rating, which I did see listed as a "spec" on a couple of other seller's websites. I have a Bunn coffeemaker and I just measured the current draw of the warming plate on it at 1.05 amps. (I made sure that the main water heating element's thermostat was OFF at that time of course.) So, if approximately 120 watts will keep a full caraffe of coffee at proper drinking temperature on my Bunn coffeemaker, the stand alone Bunn warmers probably draw no more than the "built in" ones. Thus, that 300 watt dimmer ought to do just fine after you find the right slider setting to keep a single cup hot. Go for it! Jeff -- Jeffry Wisnia (W1BSV + Brass Rat '57 EE) The speed of light is 1.98*10^14 fathoms per fortnight.- Hide quoted text - - Show quoted text - My gosh how we manage to make something so complicated. 1) Most dimmers are designed to reduce the brilliance of incandescent lamps. They do this either by reducing the voltage, whereupon the Voltage Squared divided by the Resistance of the load applies. (It's not a theory btw it is "Ohm's Law" etc. And as old as the hills!) And as noted if the voltage is reduced to half one will get one quarter the amount of energy (heat/light or a bit of both) at the load. BTW: Some very old style variable resistance dimmers themselves would get hot in order to do the voltage reduction and this could be classified as 'wasted' heat! OR, the amount of electric power applied to the load (lamp/coffee warmer etc.) is altered by changing the wave shape of the inputted sine wave so that only part of it (or a reshaped wave) gets through to the load which is then not as bright, or in this case not kept as warm. .. 2) Since the coffee/tea warmer is most likely just some sort of resistance heater, yes, most likely the dimmer will work fine. Just find the right setting of the dimmer. Also agree that any appliance that really does consume 115 volts at 15 amps (That's 1725 watts!) sounds a lot more powerful than a 'warmer'. That's sounds more like a kettle, to 'make/brew' tea or coffee! :-) Perahps it's designed to be used to heat up the water, drop in the tea or coffee and then be switched off? In other words it's more of a coffee/tea maker than a 'warmer'! We used to make tea that way, at a work bench, by dropping a wire wound resistor connected to 48 volts DC directly into a mug of water. When it boiled we'd drop in the tea and after a moment or two disconnect and remove the heater. Can't remember the wattage but it was probably around one amp or less at 48 volts; hence V x I = 48 x 1 = 48 watts. The colour of the heater resistance was dark brown; deepening with use. But it was quite easy to make another one if it looked 'too unsanitary'. For example many small floor heaters are no more than around 1500 to 1800 watts for the very reason they can then be plugged into a typical domestic outlet! And hair dryers! And forget all this stuff about the resistance (of the lamp or the coffee warmer) varying with temperature; yes it does. Usually increasing but not necessarily in a direct linear relationship with temperature. But for practical purposes forget it. Just tiddle with the dimmer adjustment until one finds a setting that works. After all the amount of drink fluid will, presumably, be decreasing as it is consumed, so we don't want to get off on the subject of a fixed amount of kilo-calories of heat energy being applied to decreasing amount of fluid of specific gravity X; minus the thermal mass of the container and the rate of heat loss from that container taking into account the ambient temp. of the room! Just sip and enjoy. Also btw if the warmer only takes very small number of watts the dimmer which has probably been designed and produced for a typical incandescent desk lamp bulb of say 40 to 100 watts (maximum 300) may be a somewhat finicky to adjust; also taking into account, as above, the fluid will be decreasing! Which reminds; right now have an almost full pot of Sri Lankan tea 'on the hob'. Must go and refill this cuppa. Cheers. |
#15
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Can I put a coffee warmer on a dimmer switch?
On Fri, 19 Sep 2008 18:01:59 -0400, Jeff Wisnia
wrote: Square Peg wrote: Most coffee mug warmers are under-powered. One reviewer on Amazon said that they were restricted to about 24 watts by law. This one http://www.amazon.com/Bunn-BCW-Warme...1796737&sr=8-3 is made for warming the whole coffee pot. It says it's 120V/15amp. Several of the reviews say that they use it for a single cup, but it keeps it too hot. It only has on/off -- no temperature control. Can I put it on a 300 watt dimmer switch like this? http://www.amazon.com/Lutron-Electro...1799800&sr=8-2 If not, is there a way to ramp the the power down as an external thermostat? I seriously doubt the veracity of that "120V/15 amp" rating, which I did see listed as a "spec" on a couple of other seller's websites. I have a Bunn coffeemaker and I just measured the current draw of the warming plate on it at 1.05 amps. (I made sure that the main water heating element's thermostat was OFF at that time of course.) So, if approximately 120 watts will keep a full caraffe of coffee at proper drinking temperature on my Bunn coffeemaker, the stand alone Bunn warmers probably draw no more than the "built in" ones. That 120 watts is 1 amp x 120 volts, right? Thus, that 300 watt dimmer ought to do just fine after you find the right slider setting to keep a single cup hot. And then duck tape it in place! ;-) Go for it! I'll report back (or just listen for the fire trucks). Jeff |
#16
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Can I put a coffee warmer on a dimmer switch?
On Fri, 19 Sep 2008 16:16:29 -0700, Square Peg wrote:
On Fri, 19 Sep 2008 08:08:58 -0700 (PDT), ransley wrote: On Sep 19, 12:23*am, Square Peg wrote: Most coffee mug warmers are under-powered. One reviewer on Amazon said that they were restricted to about 24 watts by law. This one http://www.amazon.com/Bunn-BCW-Warme.../B00023WAS0/re... is made for warming the whole coffee pot. It says it's 120V/15amp. Several of the reviews say that they use it for a single cup, but it keeps it too hot. It only has on/off -- no temperature control. Can I put it on a 300 watt dimmer switch like this? http://www.amazon.com/Lutron-Electro...-300H-WH/dp/B0... If not, is there a way to ramp the the power down as an external thermostat? It will work but if the warmer pulls more than the dimmer spec it will burn out the dimmer, 15a is an expensive dimmer,Ive never seen more than 1000w for 50$ I was worried about that. If it draws 15A, that would be 1650 watts, no? If it does burn out the dimmer, will it cause a fire or melt? I could try it in the garage or back yard. An 1800 watt coffee warmer? That sounds ludicrous. |
#17
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Can I put a coffee warmer on a dimmer switch?
On Thu, 18 Sep 2008 22:23:52 -0700, Square Peg wrote:
Most coffee mug warmers are under-powered. One reviewer on Amazon said that they were restricted to about 24 watts by law. This one http://www.amazon.com/Bunn-BCW-Warme...1796737&sr=8-3 is made for warming the whole coffee pot. It says it's 120V/15amp. Several of the reviews say that they use it for a single cup, but it keeps it too hot. It only has on/off -- no temperature control. Can I put it on a 300 watt dimmer switch like this? http://www.amazon.com/Lutron-Electro...1799800&sr=8-2 If not, is there a way to ramp the the power down as an external thermostat? I don't know where that 120V/15A spec came from. Bunn says nothing about the requirements of the BCW. Two other heavier duty warmers on the product page have 100W elements. http://www.bunnomatic.com/retail/parts/warmer.html |
#18
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Can I put a coffee warmer on a dimmer switch?
Square Peg wrote:
On Fri, 19 Sep 2008 06:34:10 -0500, "Rick Brandt" wrote: Boden wrote: Yes. It's a resistive load, just like a light bulb. I find it difficult to believe that 15 amps is correct, that would be 1800 watts which will do far more than warm a coffee pot. If you use the Lutron dimmer, make sure that the warmer is under 300 watts, or get one a bit more robust. If it's controlled by a thermostat wouldn't lowering the voltage just make it take longer to reach the same temp? I don't think it is controlled by a thermostat. I think it is just on. At least, it doesn't appear to have any kind of temperature control. Well the warmer on my coffee pot is definitely on one. We had to run things off a generator last year because we lost power and I could hear the load on the generator cycle up and down at regular intervals when we used the coffee pot. I would think all such things would have one of those simple bi-metal switch thermostats on them. Otherwise they could overheat as the liquid in the pot is reduced (or if the pot is removed altogether). |
#19
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Can I put a coffee warmer on a dimmer switch?
It won't work even if you start with the 300 watt dimmer in the off
position. The 1500 watt heater upon startup may draw as much as 10 times its normal current before the element heats up. That means that your dimmer will be initially looking at a resistance of less than one ohm. |
#20
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Can I put a coffee warmer on a dimmer switch?
terry wrote:
On Sep 19, 8:01 pm, Jeff Wisnia wrote: Square Peg wrote: Most coffee mug warmers are under-powered. One reviewer on Amazon said that they were restricted to about 24 watts by law. This one http://www.amazon.com/Bunn-BCW-Warme.../B00023WAS0/re... is made for warming the whole coffee pot. It says it's 120V/15amp. Several of the reviews say that they use it for a single cup, but it keeps it too hot. It only has on/off -- no temperature control. Can I put it on a 300 watt dimmer switch like this? http://www.amazon.com/Lutron-Electro...-300H-WH/dp/B0... If not, is there a way to ramp the the power down as an external thermostat? I seriously doubt the veracity of that "120V/15 amp" rating, which I did see listed as a "spec" on a couple of other seller's websites. I have a Bunn coffeemaker and I just measured the current draw of the warming plate on it at 1.05 amps. (I made sure that the main water heating element's thermostat was OFF at that time of course.) So, if approximately 120 watts will keep a full caraffe of coffee at proper drinking temperature on my Bunn coffeemaker, the stand alone Bunn warmers probably draw no more than the "built in" ones. Thus, that 300 watt dimmer ought to do just fine after you find the right slider setting to keep a single cup hot. Go for it! Jeff -- Jeffry Wisnia (W1BSV + Brass Rat '57 EE) The speed of light is 1.98*10^14 fathoms per fortnight.- Hide quoted text - - Show quoted text - My gosh how we manage to make something so complicated. Fun, isn't it? :-) 1) Most dimmers are designed to reduce the brilliance of incandescent lamps. They do this either by reducing the voltage, whereupon the Voltage Squared divided by the Resistance of the load applies. (It's not a theory btw it is "Ohm's Law" etc. And as old as the hills!) And as noted if the voltage is reduced to half one will get one quarter the amount of energy (heat/light or a bit of both) at the load. BTW: Some very old style variable resistance dimmers themselves would get hot in order to do the voltage reduction and this could be classified as 'wasted' heat! Don't forget the Variac type light dimmers used in some homes before the development of the present wave chopping solid state dimmers. They wasted far less power than those rheostat types you mention. OR, the amount of electric power applied to the load (lamp/coffee warmer etc.) is altered by changing the wave shape of the inputted sine wave so that only part of it (or a reshaped wave) gets through to the load which is then not as bright, or in this case not kept as warm. . 2) Since the coffee/tea warmer is most likely just some sort of resistance heater, yes, most likely the dimmer will work fine. Just find the right setting of the dimmer. Also agree that any appliance that really does consume 115 volts at 15 amps (That's 1725 watts!) sounds a lot more powerful than a 'warmer'. That's sounds more like a kettle, to 'make/brew' tea or coffee! :-) Perahps it's designed to be used to heat up the water, drop in the tea or coffee and then be switched off? In other words it's more of a coffee/tea maker than a 'warmer'! We used to make tea that way, at a work bench, by dropping a wire wound resistor connected to 48 volts DC directly into a mug of water. When it boiled we'd drop in the tea and after a moment or two disconnect and remove the heater. Can't remember the wattage but it was probably around one amp or less at 48 volts; hence V x I = 48 x 1 = 48 watts. The colour of the heater resistance was dark brown; deepening with use. But it was quite easy to make another one if it looked 'too unsanitary'. Back in college in the '50s we used to cook hot dogs in our dorm rooms by jabbing two table forks into their ends and connecting the fork handles to line voltage with an old lamp cord. For a while they made hot dog cooking kitchen appliances which worked on the same principle. They held four (or maybe six) hot dogs jabbed onto pairs of spikes which got line voltage switched onto them when a safety cover was closed over the dogs. I haven't noticed any of that kind advertised lately though. For example many small floor heaters are no more than around 1500 to 1800 watts for the very reason they can then be plugged into a typical domestic outlet! And hair dryers! And forget all this stuff about the resistance (of the lamp or the coffee warmer) varying with temperature; yes it does. Usually increasing but not necessarily in a direct linear relationship with temperature. But for practical purposes forget it. Just tiddle with the dimmer adjustment until one finds a setting that works. After all the amount of drink fluid will, presumably, be decreasing as it is consumed, so we don't want to get off on the subject of a fixed amount of kilo-calories of heat energy being applied to decreasing amount of fluid of specific gravity X; minus the thermal mass of the container and the rate of heat loss from that container taking into account the ambient temp. of the room! Just sip and enjoy. Also btw if the warmer only takes very small number of watts the dimmer which has probably been designed and produced for a typical incandescent desk lamp bulb of say 40 to 100 watts (maximum 300) may be a somewhat finicky to adjust; also taking into account, as above, the fluid will be decreasing! Which reminds; right now have an almost full pot of Sri Lankan tea 'on the hob'. Must go and refill this cuppa. Cheers. Jeff -- Jeffry Wisnia (W1BSV + Brass Rat '57 EE) The speed of light is 1.98*10^14 fathoms per fortnight. |
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Can I put a coffee warmer on a dimmer switch?
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Can I put a coffee warmer on a dimmer switch?
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Can I put a coffee warmer on a dimmer switch?
On Fri, 19 Sep 2008 19:30:04 -0500, "Rick Brandt"
wrote: Square Peg wrote: On Fri, 19 Sep 2008 06:34:10 -0500, "Rick Brandt" wrote: Boden wrote: Yes. It's a resistive load, just like a light bulb. I find it difficult to believe that 15 amps is correct, that would be 1800 watts which will do far more than warm a coffee pot. If you use the Lutron dimmer, make sure that the warmer is under 300 watts, or get one a bit more robust. If it's controlled by a thermostat wouldn't lowering the voltage just make it take longer to reach the same temp? I don't think it is controlled by a thermostat. I think it is just on. At least, it doesn't appear to have any kind of temperature control. Well the warmer on my coffee pot is definitely on one. We had to run things off a generator last year because we lost power and I could hear the load on the generator cycle up and down at regular intervals when we used the coffee pot. I would think all such things would have one of those simple bi-metal switch thermostats on them. Otherwise they could overheat as the liquid in the pot is reduced (or if the pot is removed altogether). Good point. I should have said that I don't think ti has a *variable* thermostat. That's what I thought you meant. There is no temperature control. But I am sure you are right that it may have some sort of threshold control to turn it off at some fixed temperature. |
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Can I put a coffee warmer on a dimmer switch?
Resistive loads don't draw ten times their normal current on startup, that's an induction motor starting stalled and even then 10x would be pretty high. What are you talking about? This resistive load is a tungsten or nichrome or similar metal that with out a doubt changes resistance depending on its temperature. |
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Can I put a coffee warmer on a dimmer switch?
On Sep 19, 8:16*am, "JohnR66" wrote:
"John Grabowski" wrote in message ... "Square Peg" wrote in message .. . Most coffee mug warmers are under-powered. One reviewer on Amazon said that they were restricted to about 24 watts by law. This one http://www.amazon.com/Bunn-BCW-Warme.../B00023WAS0/re.... is made for warming the whole coffee pot. It says it's 120V/15amp. Several of the reviews say that they use it for a single cup, but it keeps it too hot. It only has on/off -- no temperature control. Can I put it on a 300 watt dimmer switch like this? http://www.amazon.com/Lutron-Electro...-300H-WH/dp/B0.... If not, is there a way to ramp the the power down as an external thermostat? You will probably be disappointed in the results and waste electricity at the same time. *The heating elements are designed to perform at a certain voltage. *As that decreases so will the heat level, but it will not be on a straight line but rather a drastic curve due to the resistive nature of the elements. Take a look at what happens when a light bulb is dimmed. *Not only is the light output diminished, but the color of the light changes as well because they were designed for certain voltage. An incandescent light bulb is inefficient at producing light and it gets much worse as the voltage is reduced, however, it is great at producing heat. If you reduce the voltage on a heating element, it will produce less heat but is still nearly 100% efficient at producing the heat. It does not become less efficient if that is what you were trying to say.- Hide quoted text - - Show quoted text - A resistance element in a heater like this behaves a lot differently than a light bulb. The temperature change in a lightbulb goes from room temp when off to thousands of degrees when lit. That causes the resistance of the filament to change substantially from cold to hot. In the case of a resistance heater in a coffee pot, the resistance of the element is going to change much over the small temperature range from 70 to 150 or so degrees. |
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Can I put a coffee warmer on a dimmer switch?
On Sep 20, 1:17*am, wrote:
Resistive loads don't draw ten times their normal current on startup, that's an induction motor starting stalled and even then 10x would be pretty high. What are you talking about? This resistive load is a tungsten or nichrome or similar metal that with out a doubt changes resistance depending on its temperature. What he's talking about is that a resistive load in a coffee pot doesn't change in resistance by anywhere near 10X over it's operating range. If they did draw 10X, then the typical 1500W hair dryer would draw 120amps when first turned on and you'd have tripped breakers. A lot of this is probably being taken out of context from the case of light bulbs, which do vary substantially in resistance from cold to hot. But in this case, cold is room temp or below and hot is it glowing at thousands of degrees. That doesn't happen in a coffee pot, where the heating element is only going from 70 deg to maybe 200 and the resistance change can be ignored. |
#27
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Can I put a coffee warmer on a dimmer switch?
On Sep 19, 7:17*pm, terry wrote:
On Sep 19, 8:01*pm, Jeff Wisnia wrote: Square Peg wrote: Most coffee mug warmers are under-powered. One reviewer on Amazon said that they were restricted to about 24 watts by law. This one http://www.amazon.com/Bunn-BCW-Warme.../B00023WAS0/re.... is made for warming the whole coffee pot. It says it's 120V/15amp. Several of the reviews say that they use it for a single cup, but it keeps it too hot. It only has on/off -- no temperature control. Can I put it on a 300 watt dimmer switch like this? http://www.amazon.com/Lutron-Electro...-300H-WH/dp/B0.... If not, is there a way to ramp the the power down as an external thermostat? I seriously doubt the veracity of that "120V/15 amp" rating, which I did see listed as a "spec" on a couple of other seller's websites. I have a Bunn coffeemaker and I just measured the current draw of the warming plate on it at 1.05 amps. (I made sure that the main water heating element's thermostat was OFF at that time of course.) So, if approximately 120 watts will keep a full caraffe of coffee at proper drinking temperature on my Bunn coffeemaker, the stand alone Bunn warmers probably draw no more than the "built in" ones. Thus, that 300 watt dimmer ought to do just fine after you find the right slider setting to keep a single cup hot. Go for it! Jeff -- Jeffry Wisnia (W1BSV + Brass Rat '57 EE) The speed of light is 1.98*10^14 fathoms per fortnight.- Hide quoted text - - Show quoted text - My gosh how we manage to make something so complicated. 1) Most dimmers are designed to reduce the brilliance of incandescent lamps. They do this either by reducing the voltage, whereupon the Voltage Squared divided by the Resistance of the load *applies. (It's not a theory btw it is "Ohm's Law" etc. And as old as the hills!) And as noted if the voltage is reduced to half one will get one quarter the amount of energy (heat/light or a bit of both) at the load. BTW: Some very old style variable resistance dimmers themselves would get hot in order to do the voltage reduction and this could be classified as 'wasted' heat! OR, the amount of electric power applied to the load (lamp/coffee warmer etc.) is altered by changing the wave shape of the inputted sine wave so that only part of it (or a reshaped wave) gets through to the load which is then not as bright, or in this case not kept as warm. . 2) Since the coffee/tea warmer is most likely just some sort of resistance heater, yes, most likely the dimmer will work fine. Just find the right setting of the dimmer. Also agree that any appliance that really does consume 115 volts at 15 amps (That's 1725 watts!) sounds a lot more powerful than a 'warmer'. That's sounds more like a kettle, to 'make/brew' tea or coffee! :-) Perahps it's designed to be used to heat up the water, drop in the tea or coffee and then be switched off? In other words it's more of a coffee/tea maker than a 'warmer'! We used to make tea that way, at a work bench, *by dropping a wire wound resistor connected to 48 volts DC directly into a mug of water. When it boiled we'd drop in the tea and after a moment or two disconnect and remove the heater. Can't remember the wattage but it was probably around one amp or less at 48 volts; hence V x I = 48 x 1 = 48 watts. *The colour of the heater resistance was dark brown; deepening with use. But it was quite easy to make another one if it looked 'too unsanitary'. For example many small floor heaters are no more than around 1500 to 1800 watts for the very reason they can then be plugged into a typical domestic outlet! And hair dryers! And forget all this stuff about the resistance (of the lamp or the coffee warmer) varying with temperature; yes it does. Usually increasing but not necessarily in a direct linear relationship with temperature. But for practical purposes forget it. Just tiddle with the dimmer adjustment until one finds a setting that works. After all the amount of drink fluid will, presumably, be decreasing as it is consumed, so we don't want to get off on the subject of a fixed amount of kilo-calories of heat energy being applied to decreasing amount of fluid of specific gravity X; minus the thermal mass of the container and the rate of heat loss from that container taking into account the ambient temp. of the room! *Just sip and enjoy. Also btw if the warmer only takes very small number of watts the dimmer which has probably been designed and produced for a typical incandescent desk lamp bulb of say 40 to 100 watts (maximum 300) may be a somewhat finicky to adjust; also taking into account, as above, the fluid will be decreasing! Which reminds; right now have an almost full pot of Sri Lankan tea 'on the hob'. Must go and refill this cuppa. Cheers.- Hide quoted text - - Show quoted text - Dimmers dont control light bulb intensity through variable resistance unless you want to call the difference between off and on a change in resistance. They control the intensity by controling the off/on duty cycle. |
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Can I put a coffee warmer on a dimmer switch?
O
What he's talking about is that a resistive load in a coffee pot doesn't change in resistance by anywhere near 10X over it's operating range. If they did draw 10X, then the typical 1500W hair dryer would draw 120amps when first turned on and you'd have tripped breakers. A lot of this is probably being taken out of context from the case of light bulbs, which do vary substantially in resistance from cold to hot. But in this case, cold is room temp or below and hot is it glowing at thousands of degrees. That doesn't happen in a coffee pot, where the heating element is only going from 70 deg to maybe 200 and the resistance change can be ignored. The element gets much hotter than 200 degrees. The inrush current depends on the particular element material. http://www.eurotherm.com/training/tu...heatermtls.htm |
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Can I put a coffee warmer on a dimmer switch?
Jeff Wisnia wrote:
.... Back in college in the '50s we used to cook hot dogs in our dorm rooms by jabbing two table forks into their ends and connecting the fork handles to line voltage with an old lamp cord. .... Ever done the dill pickle? -- |
#30
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Can I put a coffee warmer on a dimmer switch?
On Sep 20, 10:24*am, wrote:
O What he's talking about is that a resistive load in a coffee pot doesn't change in resistance by anywhere near 10X over it's operating range. * * If they did draw 10X, then the typical 1500W hair dryer would draw 120amps when first turned on and you'd have tripped breakers. * *A lot of this is probably being taken out of context from the case of light bulbs, which do vary substantially in resistance from cold to hot. * But in this case, cold is room temp or below and hot is it glowing at thousands of degrees. *That doesn't happen in a coffee pot, where the heating element is only going from 70 deg to maybe 200 and the resistance change can be ignored. The element gets much hotter than 200 degrees. Exactly how much hotter than 200 deg? Would 300 deg F make you happy? The point is that you do not get anywhere near a 10X change in resistance over the temp range of the heating element in a coffee warmer. You do get that kind of resistance change in a light bulb, where the filament temp changes by 3000 degrees. The inrush current depends on the particular element material. From your own source: "Nickel-chromium alloys. These are the most common, and for control, the most docile class of resistance heater materials. Various formulations, which can include iron, aluminum and silicon, show useable element temperatures up to some 1400 º C. Change in resistance from room temperature over the working range is only some 4 – 6%. It also changes very little during service life, which also makes it easy to detect and warn of partial heater failure by monitoring the combined resistance of several parallel branches." When you have something that says the resistance in a coffee warmer varies by 10X, post a link. http://www.eurotherm.com/training/tu...ion/holland/he... |
#31
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Can I put a coffee warmer on a dimmer switch?
On Sep 20, 12:44*am, Jeff Wisnia wrote:
terry wrote: On Sep 19, 8:01 pm, Jeff Wisnia wrote: Square Peg wrote: Most coffee mug warmers are under-powered. One reviewer on Amazon said that they were restricted to about 24 watts by law. This one http://www.amazon.com/Bunn-BCW-Warme.../B00023WAS0/re.... is made for warming the whole coffee pot. It says it's 120V/15amp. Several of the reviews say that they use it for a single cup, but it keeps it too hot. It only has on/off -- no temperature control. Can I put it on a 300 watt dimmer switch like this? http://www.amazon.com/Lutron-Electro...-300H-WH/dp/B0.... If not, is there a way to ramp the the power down as an external thermostat? I seriously doubt the veracity of that "120V/15 amp" rating, which I did see listed as a "spec" on a couple of other seller's websites. I have a Bunn coffeemaker and I just measured the current draw of the warming plate on it at 1.05 amps. (I made sure that the main water heating element's thermostat was OFF at that time of course.) So, if approximately 120 watts will keep a full caraffe of coffee at proper drinking temperature on my Bunn coffeemaker, the stand alone Bunn warmers probably draw no more than the "built in" ones. Thus, that 300 watt dimmer ought to do just fine after you find the right slider setting to keep a single cup hot. Go for it! Jeff -- Jeffry Wisnia (W1BSV + Brass Rat '57 EE) The speed of light is 1.98*10^14 fathoms per fortnight.- Hide quoted text - - Show quoted text - My gosh how we manage to make something so complicated. Fun, isn't it? :-) 1) Most dimmers are designed to reduce the brilliance of incandescent lamps. They do this either by reducing the voltage, whereupon the Voltage Squared divided by the Resistance of the load *applies. (It's not a theory btw it is "Ohm's Law" etc. And as old as the hills!) And as noted if the voltage is reduced to half one will get one quarter the amount of energy (heat/light or a bit of both) at the load. BTW: Some very old style variable resistance dimmers themselves would get hot in order to do the voltage reduction and this could be classified as 'wasted' heat! Don't forget the Variac type light dimmers used in some homes before the development of the present wave chopping solid state dimmers. They wasted far less power than those rheostat types you mention. OR, the amount of electric power applied to the load (lamp/coffee warmer etc.) is altered by changing the wave shape of the inputted sine wave so that only part of it (or a reshaped wave) gets through to the load which is then not as bright, or in this case not kept as warm. . 2) Since the coffee/tea warmer is most likely just some sort of resistance heater, yes, most likely the dimmer will work fine. Just find the right setting of the dimmer. Also agree that any appliance that really does consume 115 volts at 15 amps (That's 1725 watts!) sounds a lot more powerful than a 'warmer'. That's sounds more like a kettle, to 'make/brew' tea or coffee! :-) Perahps it's designed to be used to heat up the water, drop in the tea or coffee and then be switched off? In other words it's more of a coffee/tea maker than a 'warmer'! We used to make tea that way, at a work bench, *by dropping a wire wound resistor connected to 48 volts DC directly into a mug of water. When it boiled we'd drop in the tea and after a moment or two disconnect and remove the heater. Can't remember the wattage but it was probably around one amp or less at 48 volts; hence V x I = 48 x 1 = 48 watts. *The colour of the heater resistance was dark brown; deepening with use. But it was quite easy to make another one if it looked 'too unsanitary'. Back in college in the '50s we used to cook hot dogs in our dorm rooms by jabbing two table forks into their ends and connecting the fork handles to line voltage with an old lamp cord. For a while they made hot dog cooking kitchen appliances which worked on the same principle. They held four (or maybe six) hot dogs jabbed onto pairs of spikes which got line voltage switched onto them when a safety cover was closed over the dogs. I haven't noticed any of that kind advertised lately though. For example many small floor heaters are no more than around 1500 to 1800 watts for the very reason they can then be plugged into a typical domestic outlet! And hair dryers! And forget all this stuff about the resistance (of the lamp or the coffee warmer) varying with temperature; yes it does. Usually increasing but not necessarily in a direct linear relationship with temperature. But for practical purposes forget it. Just tiddle with the dimmer adjustment until one finds a setting that works. After all the amount of drink fluid will, presumably, be decreasing as it is consumed, so we don't want to get off on the subject of a fixed amount of kilo-calories of heat energy being applied to decreasing amount of fluid of specific gravity X; minus the thermal mass of the container and the rate of heat loss from that container taking into account the ambient temp. of the room! *Just sip and enjoy. Also btw if the warmer only takes very small number of watts the dimmer which has probably been designed and produced for a typical incandescent desk lamp bulb of say 40 to 100 watts (maximum 300) may be a somewhat finicky to adjust; also taking into account, as above, the fluid will be decreasing! Which reminds; right now have an almost full pot of Sri Lankan tea 'on the hob'. Must go and refill this cuppa. Cheers. Jeff -- Jeffry Wisnia (W1BSV + Brass Rat '57 EE) The speed of light is 1.98*10^14 fathoms per fortnight.- Hide quoted text - - Show quoted text -- Hide quoted text - - Show quoted text -- Hide quoted text - - Show quoted text - Hi Jerry. Agree; the variac transformer type; not very common IMHO that's why we wrote "Some older style dimmers etc.". In fact got one of those auto-transformer types somewhere (Pretty heavy wattage, I think it came out of an assembly/dining hall); only reason not using it as an electronics bench variac is that we have another variac. Also need an odd sized shaft knob for the ex-lighting variac. Must make or adapt a knob sometime! Maybe a lever/pointer arrangement would work? |
#32
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Can I put a coffee warmer on a dimmer switch?
On Sep 20, 12:44*am, Jeff Wisnia wrote:
terry wrote: On Sep 19, 8:01 pm, Jeff Wisnia wrote: Square Peg wrote: Most coffee mug warmers are under-powered. One reviewer on Amazon said that they were restricted to about 24 watts by law. This one http://www.amazon.com/Bunn-BCW-Warme.../B00023WAS0/re.... is made for warming the whole coffee pot. It says it's 120V/15amp. Several of the reviews say that they use it for a single cup, but it keeps it too hot. It only has on/off -- no temperature control. Can I put it on a 300 watt dimmer switch like this? http://www.amazon.com/Lutron-Electro...-300H-WH/dp/B0.... If not, is there a way to ramp the the power down as an external thermostat? I seriously doubt the veracity of that "120V/15 amp" rating, which I did see listed as a "spec" on a couple of other seller's websites. I have a Bunn coffeemaker and I just measured the current draw of the warming plate on it at 1.05 amps. (I made sure that the main water heating element's thermostat was OFF at that time of course.) So, if approximately 120 watts will keep a full caraffe of coffee at proper drinking temperature on my Bunn coffeemaker, the stand alone Bunn warmers probably draw no more than the "built in" ones. Thus, that 300 watt dimmer ought to do just fine after you find the right slider setting to keep a single cup hot. Go for it! Jeff -- Jeffry Wisnia (W1BSV + Brass Rat '57 EE) The speed of light is 1.98*10^14 fathoms per fortnight.- Hide quoted text - - Show quoted text - My gosh how we manage to make something so complicated. Fun, isn't it? :-) 1) Most dimmers are designed to reduce the brilliance of incandescent lamps. They do this either by reducing the voltage, whereupon the Voltage Squared divided by the Resistance of the load *applies. (It's not a theory btw it is "Ohm's Law" etc. And as old as the hills!) And as noted if the voltage is reduced to half one will get one quarter the amount of energy (heat/light or a bit of both) at the load. BTW: Some very old style variable resistance dimmers themselves would get hot in order to do the voltage reduction and this could be classified as 'wasted' heat! Don't forget the Variac type light dimmers used in some homes before the development of the present wave chopping solid state dimmers. They wasted far less power than those rheostat types you mention. OR, the amount of electric power applied to the load (lamp/coffee warmer etc.) is altered by changing the wave shape of the inputted sine wave so that only part of it (or a reshaped wave) gets through to the load which is then not as bright, or in this case not kept as warm. . 2) Since the coffee/tea warmer is most likely just some sort of resistance heater, yes, most likely the dimmer will work fine. Just find the right setting of the dimmer. Also agree that any appliance that really does consume 115 volts at 15 amps (That's 1725 watts!) sounds a lot more powerful than a 'warmer'. That's sounds more like a kettle, to 'make/brew' tea or coffee! :-) Perahps it's designed to be used to heat up the water, drop in the tea or coffee and then be switched off? In other words it's more of a coffee/tea maker than a 'warmer'! We used to make tea that way, at a work bench, *by dropping a wire wound resistor connected to 48 volts DC directly into a mug of water. When it boiled we'd drop in the tea and after a moment or two disconnect and remove the heater. Can't remember the wattage but it was probably around one amp or less at 48 volts; hence V x I = 48 x 1 = 48 watts. *The colour of the heater resistance was dark brown; deepening with use. But it was quite easy to make another one if it looked 'too unsanitary'. Back in college in the '50s we used to cook hot dogs in our dorm rooms by jabbing two table forks into their ends and connecting the fork handles to line voltage with an old lamp cord. For a while they made hot dog cooking kitchen appliances which worked on the same principle. They held four (or maybe six) hot dogs jabbed onto pairs of spikes which got line voltage switched onto them when a safety cover was closed over the dogs. I haven't noticed any of that kind advertised lately though. For example many small floor heaters are no more than around 1500 to 1800 watts for the very reason they can then be plugged into a typical domestic outlet! And hair dryers! And forget all this stuff about the resistance (of the lamp or the coffee warmer) varying with temperature; yes it does. Usually increasing but not necessarily in a direct linear relationship with temperature. But for practical purposes forget it. Just tiddle with the dimmer adjustment until one finds a setting that works. After all the amount of drink fluid will, presumably, be decreasing as it is consumed, so we don't want to get off on the subject of a fixed amount of kilo-calories of heat energy being applied to decreasing amount of fluid of specific gravity X; minus the thermal mass of the container and the rate of heat loss from that container taking into account the ambient temp. of the room! *Just sip and enjoy. Also btw if the warmer only takes very small number of watts the dimmer which has probably been designed and produced for a typical incandescent desk lamp bulb of say 40 to 100 watts (maximum 300) may be a somewhat finicky to adjust; also taking into account, as above, the fluid will be decreasing! Which reminds; right now have an almost full pot of Sri Lankan tea 'on the hob'. Must go and refill this cuppa. Cheers. Jeff -- Jeffry Wisnia (W1BSV + Brass Rat '57 EE) The speed of light is 1.98*10^14 fathoms per fortnight.- Hide quoted text - - Show quoted text -- Hide quoted text - - Show quoted text -- Hide quoted text - - Show quoted text - |
#33
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Can I put a coffee warmer on a dimmer switch?
On Sep 20, 12:44*am, Jeff Wisnia wrote:
terry wrote: On Sep 19, 8:01 pm, Jeff Wisnia wrote: Square Peg wrote: Most coffee mug warmers are under-powered. One reviewer on Amazon said that they were restricted to about 24 watts by law. This one http://www.amazon.com/Bunn-BCW-Warme.../B00023WAS0/re.... is made for warming the whole coffee pot. It says it's 120V/15amp. Several of the reviews say that they use it for a single cup, but it keeps it too hot. It only has on/off -- no temperature control. Can I put it on a 300 watt dimmer switch like this? http://www.amazon.com/Lutron-Electro...-300H-WH/dp/B0.... If not, is there a way to ramp the the power down as an external thermostat? I seriously doubt the veracity of that "120V/15 amp" rating, which I did see listed as a "spec" on a couple of other seller's websites. I have a Bunn coffeemaker and I just measured the current draw of the warming plate on it at 1.05 amps. (I made sure that the main water heating element's thermostat was OFF at that time of course.) So, if approximately 120 watts will keep a full caraffe of coffee at proper drinking temperature on my Bunn coffeemaker, the stand alone Bunn warmers probably draw no more than the "built in" ones. Thus, that 300 watt dimmer ought to do just fine after you find the right slider setting to keep a single cup hot. Go for it! Jeff -- Jeffry Wisnia (W1BSV + Brass Rat '57 EE) The speed of light is 1.98*10^14 fathoms per fortnight.- Hide quoted text - - Show quoted text - My gosh how we manage to make something so complicated. Fun, isn't it? :-) 1) Most dimmers are designed to reduce the brilliance of incandescent lamps. They do this either by reducing the voltage, whereupon the Voltage Squared divided by the Resistance of the load *applies. (It's not a theory btw it is "Ohm's Law" etc. And as old as the hills!) And as noted if the voltage is reduced to half one will get one quarter the amount of energy (heat/light or a bit of both) at the load. BTW: Some very old style variable resistance dimmers themselves would get hot in order to do the voltage reduction and this could be classified as 'wasted' heat! Don't forget the Variac type light dimmers used in some homes before the development of the present wave chopping solid state dimmers. They wasted far less power than those rheostat types you mention. OR, the amount of electric power applied to the load (lamp/coffee warmer etc.) is altered by changing the wave shape of the inputted sine wave so that only part of it (or a reshaped wave) gets through to the load which is then not as bright, or in this case not kept as warm. . 2) Since the coffee/tea warmer is most likely just some sort of resistance heater, yes, most likely the dimmer will work fine. Just find the right setting of the dimmer. Also agree that any appliance that really does consume 115 volts at 15 amps (That's 1725 watts!) sounds a lot more powerful than a 'warmer'. That's sounds more like a kettle, to 'make/brew' tea or coffee! :-) Perahps it's designed to be used to heat up the water, drop in the tea or coffee and then be switched off? In other words it's more of a coffee/tea maker than a 'warmer'! We used to make tea that way, at a work bench, *by dropping a wire wound resistor connected to 48 volts DC directly into a mug of water. When it boiled we'd drop in the tea and after a moment or two disconnect and remove the heater. Can't remember the wattage but it was probably around one amp or less at 48 volts; hence V x I = 48 x 1 = 48 watts. *The colour of the heater resistance was dark brown; deepening with use. But it was quite easy to make another one if it looked 'too unsanitary'. Back in college in the '50s we used to cook hot dogs in our dorm rooms by jabbing two table forks into their ends and connecting the fork handles to line voltage with an old lamp cord. For a while they made hot dog cooking kitchen appliances which worked on the same principle. They held four (or maybe six) hot dogs jabbed onto pairs of spikes which got line voltage switched onto them when a safety cover was closed over the dogs. I haven't noticed any of that kind advertised lately though. For example many small floor heaters are no more than around 1500 to 1800 watts for the very reason they can then be plugged into a typical domestic outlet! And hair dryers! And forget all this stuff about the resistance (of the lamp or the coffee warmer) varying with temperature; yes it does. Usually increasing but not necessarily in a direct linear relationship with temperature. But for practical purposes forget it. Just tiddle with the dimmer adjustment until one finds a setting that works. After all the amount of drink fluid will, presumably, be decreasing as it is consumed, so we don't want to get off on the subject of a fixed amount of kilo-calories of heat energy being applied to decreasing amount of fluid of specific gravity X; minus the thermal mass of the container and the rate of heat loss from that container taking into account the ambient temp. of the room! *Just sip and enjoy. Also btw if the warmer only takes very small number of watts the dimmer which has probably been designed and produced for a typical incandescent desk lamp bulb of say 40 to 100 watts (maximum 300) may be a somewhat finicky to adjust; also taking into account, as above, the fluid will be decreasing! Which reminds; right now have an almost full pot of Sri Lankan tea 'on the hob'. Must go and refill this cuppa. Cheers. Jeff -- Jeffry Wisnia (W1BSV + Brass Rat '57 EE) The speed of light is 1.98*10^14 fathoms per fortnight.- Hide quoted text - - Show quoted text -- Hide quoted text - - Show quoted text -- Hide quoted text - - Show quoted text - They really were HOT-dogs!!!!!! |
#35
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Can I put a coffee warmer on a dimmer switch?
On Sep 20, 10:55*am, wrote:
On Sep 20, 1:17*am, wrote: Resistive loads don't draw ten times their normal current on startup, that's an induction motor starting stalled and even then 10x would be pretty high. What are you talking about? This resistive load is a tungsten or nichrome or similar metal that with out a doubt changes resistance depending on its temperature. What he's talking about is that a resistive load in a coffee pot doesn't change in resistance by anywhere near 10X over it's operating range. * * If they did draw 10X, then the typical 1500W hair dryer would draw 120amps when first turned on and you'd have tripped breakers. * *A lot of this is probably being taken out of context from the case of light bulbs, which do vary substantially in resistance from cold to hot. * But in this case, cold is room temp or below and hot is it glowing at thousands of degrees. *That doesn't happen in a coffee pot, where the heating element is only going from 70 deg to maybe 200 and the resistance change can be ignored. Where does the 1500 watts come from????? (Or go to)? The discussion is about a 'Coffee/tea WARMER'! Probably less than 30 watts? Or maybe we have changed over to discussing a coffee 'pot' or coffee maker. If so the 'inrush' current during the first half or full cycle after first switching on from room temperature cold would be ................ what? Maybe half the resistance, for momentarily twice the operating current? Maybe quarter resistance, for momentarily four times the current? Doubtful it would be anything like one tenth the normal operating temperature resistance, even for that few milliseconds (1000/60 = 16.7 m/secs) = one cycle! The temperature-resistance coefficient of typical (nichrome) resistance wire (alpha) is say 0.00017. In other words for a change in temperature from room at say 20C to red hot at say 600C the amount of change of resistance would be about (600 - 20) x 0.00017 = 0.0986. I think that means 9.86 percent lower resistance? Momentarily. |
#36
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Can I put a coffee warmer on a dimmer switch?
When you have something that says the resistance in a coffee warmer varies by 10X, post a link. I never said it did. I said it may. There is a difference. I originally said "The 1500 watt heater upon startup may draw as much as 10 times its normal current before the element heats up." I stand by that because I said "may". I said may because we do not know what the heating element is made of. All you have to do is read the link. It gives resistance of various heating elements. Going by this link I should of said "may be 15 times" instead of 10. .. http://www.eurotherm.com/training/tu...heatermtls.htm |
#37
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Can I put a coffee warmer on a dimmer switch?
wrote:
... If they did draw 10X, then the typical 1500W hair dryer would draw 120amps when first turned on and you'd have tripped breakers. Not necessarily, with a short draw. Nick |
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