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Old May 13th, 2019, 05:06 PM   #1
bendanator
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Heater voltage

Hello everyone,

This may be a dumb question but is there a benefit of using a 240v heater over 480? Most all the equipment I work on has 480 for the main feed and then a second transformer to step it to 240 for heater bands. There are about 15 heaters per unit. Wondering if there is a reason for that and would it have been more effective to just not pay for the second transformer and do everything in 480?

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Old May 13th, 2019, 05:22 PM   #2
jaden
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I have seen two 240 heaters wired in series across 480 volt supply. Seems rather common, which makes me wonder if 480 volt heaters are hard to get.
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Old May 14th, 2019, 07:54 AM   #3
T Gibbs
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We have 480V heaters on many different machines. They're not hard to get
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Old May 14th, 2019, 10:18 AM   #4
NetNathan
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240V is more popular and universal.
Higher voltage variations are anywhere from 380 to 480.
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Old May 14th, 2019, 01:11 PM   #5
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Often it has to do with a concept called "watt density", meaning that if you want a certain amount of wattage, but the size of the element that will fit in the allotted space is small, you may end up causing scorching if the voltage is higher. So the designer plays a numbers game of using heater for a higher voltage, but applies a lower voltage to end up with the desired wattage but a lower amount of watts/sq. inch on the surface of the element.
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Old May 14th, 2019, 01:27 PM   #6
STEMAPPLICATIONS
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Mostly resistive load (fans negligible). Simple single phase example: 24kva of heaters = 100 amps @ 240 VAC or 50 amps at 480 VAC. Savings in wire if this is going to involve hundreds of feet of wire. Simple wire sizing (75 C) #3 AWG vs #8 AWG.
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Old May 14th, 2019, 02:11 PM   #7
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Just instead of connecting the heaters one by one to 240V, connected them in series of 2 to 480V.
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Old May 14th, 2019, 06:35 PM   #8
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Depends on the type of heater whether you series them. If fans or pumps are involved as parts of the heater unit, might not work so well. But at the same time, appears not as you already have some done that way. Only comment I can make is that just because an OEM figured out how to save themselves money by doing it this way doesn't mean it's the best way to do it. You open circuit one heater, neither one will work. You short circuit one heater and you will lose the other in short order. If the heaters are critical to the machine, losing one possibly means losing two ($$) or the machine is without heat at all instead of still having one running. In my experience when you run into something like this from an OEM it usually means they got a great deal on the lower voltage units.

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Old May 15th, 2019, 01:06 AM   #9
Aabeck
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I have found, even from big machinery builders, that frequently what is put on a machine being built is heavily dependent on what they have left over from previous builds.


Using 240V heaters on a 480V machine gives no difference in KWh of electricity used, but there is the added expense of a transformer, fuses and wiring - and there is a consumption of electricity by the transformer itself and heat generation if inside the enclosure to take into consideration.



Plus the wire gauge for a 4KW 240W heater wired to 240V would be larger for double the amps of a 4KW 480V heater or 2) 2KW 240V heaters in series, with larger fuses and terminals.
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Old May 15th, 2019, 09:12 AM   #10
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Quote:
Originally Posted by Aabeck View Post
I have found, even from big machinery builders, that frequently what is put on a machine being built is heavily dependent on what they have left over from previous builds.

Using 240V heaters on a 480V machine gives no difference in KWh of electricity used, but there is the added expense of a transformer, fuses and wiring - and there is a consumption of electricity by the transformer itself and heat generation if inside the enclosure to take into consideration.

Plus the wire gauge for a 4KW 240W heater wired to 240V would be larger for double the amps of a 4KW 480V heater or 2) 2KW 240V heaters in series, with larger fuses and terminals.
Another very plausible explanation for this odd configuration. Love your signature line. Sure echoes my experience!!
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Old May 15th, 2019, 10:03 PM   #11
Geoff White
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I have seen them in series between three phases but with a center tap in each pair. A heating controller varied the output by connecting the center taps as a star point. Confusing but effective.
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