Question on watts/voltage

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sohara

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Hi there,

I don't have much electrical background so I was hoping I could ask a question about wattage and voltage of heater elements. I have a ~25 gallon kettle that is powered by a single 4500 watt element (rated at 240). As you can imagine, the kettle is seriously under-powered. Toda we checked the line using a voltage meter and when touching the two lines it read 211. Does this mean it is basically 208? I am thinking of trying to get an element that is rated 5500 watts at 208 volts. Make sense?

Thanks,
Sean
 

kal

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211V on a 240V circuit seems really low. Sometimes it'll sag a bit when power is at peak usage (like in the summer with A/C units running) but usually not that much.

208V (3-phase) is usually for industrial stuff where large motors are used. If you're in a regular house, you likely do not have 3-phase. Nothing normal works on 3-phase. You can't buy something and plug it in.

Getting a 5500W element will help. I know lots of people that do 20+ gallon boils with a single 5500W element just fine.

You'd use the same 30A / 240V circuit.

Kal
 
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sohara

sohara

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211V on a 240V circuit seems really low. Sometimes it'll sag a bit when power is at peak usage (like in the summer with A/C units running) but usually not that much.

208V (3-phase) is usually for industrial stuff where large motors are used. If you're in a regular house, you likely do not have 3-phase. Nothing normal works on 3-phase. You can't buy something and plug it in.

Getting a 5500W element will help. I know lots of people that do 20+ gallon boils with a single 5500W element just fine.

You'd use the same 30A / 240V circuit.

Kal
It's an industrial location. But I gather from what you're saying that the kettle wouldn't have worked if the power source was 3 phase? The label on the element gives a rating for 240 (4500) and another for 208 (around 3700). Is 208 always 3-phase?

Also, since you're in Canada, do you know a good source for these elements? They seem kind of hard to track down. The higher wattage ones seem hard to find.

Thanks,
Sean
 
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sohara

sohara

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Oh, one more question for you. How long does it usually take for the people you know doing 20+ gallons on 5500w to get a boil going? Yesterday I did a test and after 2 hours starting from 11°C water I was in the mid 90s, not quite boiling yet.
 

aquenne

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Also keep in mind when you have your voltmeter between lines, you are seeing AC voltage, so it will be jumping up and down. A consumer voltmeter will not allow you to step thru the waveform, so you would not see the peaks (the 240v). You just see snapshots of where the voltage is.
It is not like DC, where the voltage is stable.
 

aquenne

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It's an industrial location. But I gather from what you're saying that the kettle wouldn't have worked if the power source was 3 phase? The label on the element gives a rating for 240 (4500) and another for 208 (around 3700). Is 208 always 3-phase?

Also, since you're in Canada, do you know a good source for these elements? They seem kind of hard to track down. The higher wattage ones seem hard to find.

Thanks,
Sean
I looked long and hard for a 5500W ULWD and was unable to find any in Ontario. I ended up having two shipped from the US.
 
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sohara

sohara

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I looked long and hard for a 5500W ULWD and was unable to find any in Ontario. I ended up having two shipped from the US.
Yeah, I'll probably order from the US too. I have some stuff to pick up at the border anyway, so I'll pick up the elements at the same time.
 

kal

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It's an industrial location. But I gather from what you're saying that the kettle wouldn't have worked if the power source was 3 phase? The label on the element gives a rating for 240 (4500) and another for 208 (around 3700). Is 208 always 3-phase?[
Still works, just ~208V instead of ~240V.
I don't know of any countries that offer 208V on single phase so I'd say that yes, if it's 208V, it's most likely 3-phase.

Also, since you're in Canada, do you know a good source for these elements? They seem kind of hard to track down. The higher wattage ones seem hard to find.
Sorry, no. Amazon.com ships them to Canada. Probably your best bet.

Kal
 
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sohara

sohara

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Just ordered from amazon.com

This is what wikipedia says that I think applies to my situation:

If heating equipment designed for the 240-volt three-wire single phase system is connected to two phases of a 208 volt supply, it will only produce 75% of its rated heating effect.
 

Bobby_M

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Also keep in mind when you have your voltmeter between lines, you are seeing AC voltage, so it will be jumping up and down. A consumer voltmeter will not allow you to step thru the waveform, so you would not see the peaks (the 240v). You just see snapshots of where the voltage is.
It is not like DC, where the voltage is stable.
This is not true. Most digital meters have an AC measuring mode that measures the peaks rather accurately. If you were trying to measure AC in DC mode, I can see what you're saying.

I don't know what the typical variance is in Canada but it's common that I measure 107-115 on a 120v circuit and 214-230 on a "240".
 

PleasantValleyHops

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aquenne said:
Also keep in mind when you have your voltmeter between lines, you are seeing AC voltage, so it will be jumping up and down. A consumer voltmeter will not allow you to step thru the waveform, so you would not see the peaks (the 240v). You just see snapshots of where the voltage is.
It is not like DC, where the voltage is stable.
What????? Not sure if u understand what most meters do. Unless ur spending $600+ u mos likely are not going to get a meter that will show u a peak V. What ur seeing when u are looking at ur meter is an rms "effective" voltage. Which is ehat the references r such as 120, 208, or 120,240,277,480.

Now also if ur seeing something as low as 214 instead of 240 or somewhere close to 240. U should prob contact ur utility. U could potentially be messing up motors and other heavy loads that really need that voltage to work properly. At my house im actually a little high. I read anywhere from 120-124 on any giving day and 240-245. Which also if it goes up anymore ill contact utility as well bc to high can screw up sensitive equipment just like to low will mess up motors and such.
 

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You are seeing the secondary product of a three phase transformer, one will choose this transformer when you are looking to feed multiple panels. It is more economical than buying three single phase transformers.
 

thargrav

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Also keep in mind when you have your voltmeter between lines, you are seeing AC voltage, so it will be jumping up and down. A consumer voltmeter will not allow you to step thru the waveform, so you would not see the peaks (the 240v). You just see snapshots of where the voltage is.
It is not like DC, where the voltage is stable.
aquenne,

Just so you know, 240V AC is 240V RMS (average), not 240 V peak. The peak voltage for 240V AC is 339V. AC volt meters are calibrated to direct measure in RMS volts and will measure 240V for a 240V AC circuit.
 

kal

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aquenne,

Just so you know, 240V AC is 240V RMS (average), not 240 V peak. The peak voltage for 240V AC is 339V. AC volt meters are calibrated to direct measure in RMS volts and will measure 240V for a 240V AC circuit.
+1.

Even cheap $10 AC voltmeters will do this. Stick one in a 120V AC outlet in your home and it won't jump around. It'll measure around 110-120 (depending on your neighbourhood load/time of day/year/etc). 240V is no different. You're just measuring across two HOT lines instead of a HOT and NEUTRAL.

Kal
 
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