LOW VOLTAGE WARNING

[Chris]

Another thought occurs to me with regard to electric roasters; if a roaster has enough 'head-room' and can easily attain more than adequate heat, then voltage drops may be a non-issue. 

I'm just thinking out loud, as my SC/TO's haven't given me any apparent slowness or lack of response in the 3? years I've used them.  Perhaps roasters like the Behmor that have programmed temp/time don't/can't compensate for voltage drops, and don't have the 'head-room' either.

If a heating element has the ability to get the beans to say 475?, then if a voltage drop limits its potential to say 450?, it's no big deal.  But if a heating element can only get beans to 450?, then it may be in trouble when power is lessened.

Thoughts of an unlearned man, but it seems to make sense.

For me, the whole voltage issue affects repeatability, not really a roasters ability to get X ounces of beans to Y temp in Z time.

It is clear that a pound is about the max we can properly roast in an electric roaster on a single 120VAC/15A circuit, and that is usually adequate for most home roasters.

[dsil]

I have been trying to get a great roast from my Behmor since Jan. My voltage is 122, and drops to 117.4 when the heating element kicks on. I think I finally compensated by using 12 oz. on P1 maxed out. Getting just to the edge of 2nd crack, and using all of the allowable time. I am going to install a dedicated outlet for roasting, hopefully that will give me better results.
Your Slow Learning Friend,
Doug

[Chris]

I have been trying to get a great roast from my Behmor since Jan. My voltage is 122, and drops to 117.4 when the heating element kicks on. I think I finally compensated by using 12 oz. on P1 maxed out. Getting just to the edge of 2nd crack, and using all of the allowable time. I am going to install a dedicated outlet for roasting, hopefully that will give me better results.
Your Slow Learning Friend,
Doug

One word: Variac

[Ascholten]

A Watt is a watt is a watt, whether you get it from 110 volts,  150 volts, 120 volts, whatever you call it in your area,  or 220 volts.

hell if voltage is the key, using that logic why don't you just forego the stepdown transformer and get a cooker that will roast beans at 4160, or perhaps skip another transformer and do a 33.6K cooker?  Aww hell, why not just take it right off the tap and go with a 220KV cooker, don't stand closer than 5 feet though or you might become involved in the cooking process.

The only REAL reason folks use 220 is because of the power needed, not because it's better or cleaner power, it all comes from the same transformer, from the same fusebox in your house.   Household wires for 115, are limited to carrying about 15 amps,  sure you can get a 115 volt 30 amp circuit put in, but you will pay for that extra copper.  It will be stable as hell too.

Generally things at about 1800 - 2000 watts swap over to 220 so there is less current draw through the lines, it's the amps that cause the unwanted heat.  Higher voltage = less amps for the watt hence less heat loss... all other things being equal.

why does the usa use 115.  Umm good question, it is safer than 220 really... yes it does kill a lot of folks but if you get hit by it by mistake, your chances of getting back up, possibly cursing and walking away are a lot greater than getting swatted by 220, 277 or the likes..  Higher voltage pushes the amps, and the amps are what kills.

For home roasters, your residential 110 volts will work fine with a 110 volt coffee roaster if all else is good.  If you get a voltage drop on the 115 you are going to get a bit of a drop on the 220 as well... if the drop is caused by insufficient wire load handling ability then that is a fault with the wiring, NOT with the electricity being supplied.    BIG difference there.

Before we go running out to put in brand new dedicated circuits, spend hundreds extra on 240 volt stuff, etc... check that the existing wiring is not the fault.  If you live in a 50 year old house with 50 year old wiring, umm guess what... the electrician who puts the 'new' stuff in is probably going to tell you the entire house needs rewiring to conform to code if you want the job done correctly, and might even refuse it....

Instead of 16 ounces of beans, try 14 or 13 ounces, ... sometimes little things are a lot easier and a lot less expensive of a fix.

aaron

[kwksilver]

I think the power of a heating element directly describes the amount of energy it can dump into the bean mass. So a roaster starved for power will take LONGER to dump the same energy into the beans and if the rate of energy loss of the bean mass equals the rate of energy dumped in we are at max temp.
So my guess is that the first sign of trouble would be a longer timeframe to get toa  usual spot.
I think one LOW COST approach to thisacute problem is to go with a slightly decreased batch size.
Less beans need less energy, so the rate of heat input issue can probably be combated a little bit?
Not a hot solution, obviously also throws of consistency and knowledge that one might have devloped for his roast profile with fixed variables (bean mass weight times and so on).
Lucky for me im such a bloody amateur i sit in front of the gene and twist those knobs by the seat of my pants and some rough road points (total time, end point , 350 and aroudn 1st crack...pretty modest goals)

Felix

PS: idea being that I think we would see a routine take longer before we see a roast stall at a lower temp?

[Lektrk]

After the power company told me its summertime they must have had a change of heart and checked to see if there was a problem. Tonights roast gave me the following numbers 127.6V before I started and 124.4V under load. This voltage allowed me to draw 1711Watts under full load with the light on and 643W with only the afterburner and light on. Cooling drew 663W with the light on. At this level the small grid basket didn't make any difference. Anybody think this voltage is going to cause premature failure of anything, especially the motor?

The lowervoltage sounds like it should be within its ratings (they are usually +/- 10%, it will likely make your elements last a bit longer.

[kwksilver]

sure a watt is a watt. A watt is just another word for power or energy.
However if you try to draw a large amount of energy from a low voltage line you have terrible inefficiency. That is why long distance lines are high voltage lines and why residential areas have local transformers. (and a similar reason makes AC the more efficient current to send over long distances)
Nonetheless it is not possible to cleanly deliver high wattages out of a 110V outlet. The 20 AMP circuits that arose are a patch covering the fact that 110V is a very low electromotive force. With less force you will always have a horrible time delivering great amounts of power. use thicker wires tolerating greater amperes, you have not solved your problem. You patched it...

You can drink fast through a straw, but you have to suck VERY hard.
Big gulp opening on gatorade bottles are pretty sweet.

(that analogy actually holds very well) all the way to likening the frictional loss of turbulent flow (reynolds nubmer and that) to the heat generated in thinner wires)

[Chris]

While there are theoretical reasons why 220 is more efficient than 110, in the household it is usually not an issue.

And in fact, pulling 10 amps on 110 or 5 amps on 220, the Electric company will charge you the same since they bill you for Wattage (Killawatt-Hours), not Amps or Volts.

The truth is that 220 is often used so that new wire does not have to be run, since it is max amperage that determines the wire size (independent of voltage as I understand it).  This means that the same wire that can handle 110V/15A, can also handle 220V/15A.  And I can tell you that an appliance that can run at the latter, can do a lot more heating (or work) than the former.

The reality is that most homeowners in the US don't want to run new wiring, or re-do their breaker box, and so we live with the 110/15 in most cases, though many kitchens now get 110/20 circuits.  I have managed to run several 110 espresso machines and roasters without problems on 1970's outlets (and with the help of a Kill-a-Watt & Variac).

[Ascholten]

Yes running 220 volt appliances will help with the amp loading on the receptacles, but with that mindset...unfortunately you can't find too many 220 volt toasters,  220 volt can openers etc in the usa.  It would be very easy  indeed to redo your fuse box to put out 220 volts to each and every of your receptacles but you would also have to replace every 115 volt appliance in your house with a 220 volt one... unless you ran every one through a transformer at the plug... and here is the inefficiency / waste thing again.

Seriously though, if you are that adamant on putting 220 volts in, an electrician can run an isolated receptacle, or convert an old one already there for you fairly easily.  It'll be on its own breaker and everything.  One thing to keep in mind,  if you have a water heater, dryer, stove etc, nearby, those run off 220 volts AC, you might have an easy source to tap into very nearby.  If you want to get creative, you an jack a 220 volt receptacle into your stove, on top where the controls are and run your machine that way, it will save having to run an entire new line since the line is already run / and breakered for your stove, howver id install another inline breaker at say 10 amps or whatever you need to be safe.  It doesn't have to be a hack job either, you can do this very easily and have it look very neat, and technically it will be very safe too... if you do it properly.

Aaron

[kwksilver]

heh,
I did put 220V in my kicthen. That is what some of my things run on. See the pic of my espresso machine under that thread.
You are completely correct that 22oV/15 amps is the same as 110V 15amps in terms of current running. But 110V cannot run 30 Amps. That is the ballpark you need if you actually do want to run the heating elements in both tanks on something with boilers that are around a liter.
(brewtus... cannot actually run both heating elements simultaneously and deliver full wattage to them. Vivaldi in non economy mode has 5 extra ampere's that does not mean both elements now get the same the priority element got in 15 amp mode, it is a compromise maxed out at 20 ampere)
Just take a peak at the differences between the 110V Robur, 220V (3-phase 220V).
Mazzer Robur 110v: 7.5 seconds
Mazzer Robur 220v three phase: 4.5 seconds
The 220V runs at 900W you could draw that from a 110V line, but the picture is more complicated than that.

[Lektrk]

heh,
I did put 220V in my kicthen. That is what some of my things run on. See the pic of my espresso machine under that thread.
You are completely correct that 22oV/15 amps is the same as 110V 15amps in terms of current running. But 110V cannot run 30 Amps. That is the ballpark you need if you actually do want to run the heating elements in both tanks on something with boilers that are around a liter.
(brewtus... cannot actually run both heating elements simultaneously and deliver full wattage to them. Vivaldi in non economy mode has 5 extra ampere's that does not mean both elements now get the same the priority element got in 15 amp mode, it is a compromise maxed out at 20 ampere)
Just take a peak at the differences between the 110V Robur, 220V (3-phase 220V).
Mazzer Robur 110v: 7.5 seconds
Mazzer Robur 220v three phase: 4.5 seconds
The 220V runs at 900W you could draw that from a 110V line, but the picture is more complicated than that.

You can install a 120V 30A circuit very easily, just use 10 gage wire.

[Lektrk]

heh,
I did put 220V in my kicthen. That is what some of my things run on. See the pic of my espresso machine under that thread.
You are completely correct that 22oV/15 amps is the same as 110V 15amps in terms of current running. But 110V cannot run 30 Amps. That is the ballpark you need if you actually do want to run the heating elements in both tanks on something with boilers that are around a liter.
(brewtus... cannot actually run both heating elements simultaneously and deliver full wattage to them. Vivaldi in non economy mode has 5 extra ampere's that does not mean both elements now get the same the priority element got in 15 amp mode, it is a compromise maxed out at 20 ampere)
Just take a peak at the differences between the 110V Robur, 220V (3-phase 220V).
Mazzer Robur 110v: 7.5 seconds
Mazzer Robur 220v three phase: 4.5 seconds
The 220V runs at 900W you could draw that from a 110V line, but the picture is more complicated than that.

110V and 220V are not the same. Take a motor that pulls 12A 110V, that same motor wired 220V will pull 6A.

[kwksilver]

yes you could indeed do that (30amp 110V circuit). However inside the machine the wires would have to be able to withstand the used current at the incoming voltage. That is a bit of a problem :p
Running 30 amp fused circuits and feeding multiple outlets is done pretty often in "special code" installations :p
I just don't know any appliances that need a lot of current that have taken this route. I would guess that some J-things must have that though.
They are running 100V aren't they?

110V and 220V are not the same. Take a motor that pulls 12A 110V, that same motor wired 220V will pull 6A.

  That is (((())))
I was going to say that is completely correct, but this morning i thought for a second. Help me out here. V=IR
R= the motor and is a constant?
Now if we up the voltage from 110 to 220 we doubled the electromotive force. The current flow of electrons should also double if resistance stayed the same... not half.
yes, no???

[Lektrk]

I (Amps) = E (Volts) / R (Ohms) (resistance of the motor)  The resistance of the motor stays constant, double the voltage and you half the Amps.     

[Ascholten]

The resistance of the motor may necessarily NOT stay constant.  You have impedance to play with too, CEMF, other issues, but probably diving deeper than most care to understand or even can.  Go ahead and plug your 115 appliance into 220 volts.  Ill stand by with the camera because yer gonna let the magic smoke out.

Aaron