So I’m down a bit of a rabbit hole here.
My understanding of things electrical has developed quite a ways since starting in this biz, but this one is above my head and I’m having a hard time getting ahold of the manufacturer for assistance:
We run an AEC TrueTemp circulating heater on our Bizzy Bee silver serpent for ethanol recovery. I’ve been tasked with calculating the electricity it uses (in watts and/or kilowatt-hours), and through my attempts have found that calculating 3-phase power consumption is a good bit more gnarly than single-phase. Power factors, volt-amperes, Line-to-Line vs. Line-to-Neurtal, etc., certainly not as simple as ‘Volts x Amps = Watts’.
A shot of the label on the unit:
My work so far using a 3-phase Line-to-Line formula
(watts = √3 x Power Factor x Amps x Volts)
gets me this:
Volts: 480
Amps: 62.85
Volt-Amperes: 52,252.5
Power Factor: .58
Watts: 5,714,282.1
first one feels low, second seems ridiculously high, even if I know these units are intense in their energy consumption. feels like i’m chasing my own tail over here.
I’ve not found any existing articles on the forum that lead me in the right direction; if anyone can give me a nudge in the right direction or to an article or site that could, I’d appreciate it!
Totally ignorant about what you’re doing or the equipment but circulating heater and seeing ‘pump’ and ‘heater’ on the label, I think the label already shows you what you’re looking for.
It’s a 3 hp pump, 3 hp to KW is about 2.24 and that’s on the label. The heater isn’t measurable with hp but it states it’s 48 KW, so total it’s about 50,000 watts. Maybe lol
thanks, I saw those too, and kept them in the back of my mind, preferring to use the info for the unit as a whole. for some reason. likely ignorance.
i realize though that you might be absolutely correct and I might have lead myself on a wild goose chase. unfortunately my personal Oracle for these kinds of things has left our company and left a large gap of expertise – so unfortunately i lost my sounding board, who could have told me ‘the info’s right there on the label and you’re overthing this’. if that’s the case, great, and i will have learned, which is all i ever want to do
I think your PF calculation is a little messed up — 0.58 is really low.
I could be totally wrong here, but calculating it with the total power from both the heater and pump (50.24kW) leaves you with a PF of 0.9615 instead. I’m not confident the 30,168W from the single-phase formula can be used for calculating 3Phase PF.
I believe this might be a step in the right direction because PF is typically between .85 and 1. (0.58 would be really inefficient, out of phase)
Replacing this value in your work should give you exactly 50.24 kW, same as our calculation from adding up the power from both the heater and pump. Makes sense in theory, but seems too easy… Open to hearing some feedback from an expert - I’m confident I’m missing something here.
@VAcutsclub i think you’re right, certainly 57,000 is closer to the kW of the heater/pump combined, possibly the controller/etc accounts for the difference
@analyte from what I read about Power factors, yeah that seemed off. I suspected that I had one number wrong somewhere in the steps i took and it threw the end results way off. What you’re saying makes absolute sense. and you nailed it–it seems too easy! but experience tells me it could just as easily be the answer, right under my nose. hoping as well someone more experienced can confirm, in the meantime thank you both for your input!
They sell amp meters that read current by clamping around a wire and reading the electrical field created because of the current passing through the wire. That would be more accurate to determine the actual use since the #s on the label are presumably maximums. The voltage is constant but the power readings in KW are based on the FLA current measurement, and the current draw will depend on load on the heater which depending on environment and use case could be drastically lower than the max, variable with varying degrees of variability, or pegging the max.
A power meter is the only real way to know what you’re pulling.
If you’ve got a 48kW resistive heater, and it’s a single coil, you’re pulling 48kW, but only when it is running.
Does it run 100% of the time the equipment is on? Likely not. So figure out what your % on time is to determine your approximate real world consumption.
The pump probably runs 100% of the time, or close to it, but does it actually pull 3hp 100% of the time? Also likely not. It might need that 3hp to get up to speed, but only consume half (or 1/4 or 3/4) of that at steady state.
Determining real-world energy consumption (or what it SHOULD be) accurately with pumps is actually a lot harder than it seems, and requires a ton of math and pump curves and efficiency data and such.
If a pump is connected to a standalone VFD you should be able to pull a time-stamped of amps pulled. I doubt you can on that system.
@Autumn_Ridge_Hemp@VAcutsclub@Lincoln20XX thanks, you’re all absolutely right, I’ve just been pursuing this estimate method as I’m subject to budgets, which is near the limit this month, and those clamp meters are $250ish. however I can’t argue that due to all the variables mentioned it’s the only really accurate way to get this info, and considering this is all geared towards getting an energy credit to apply towards some new, more energy-efficient equipment, it’ll effectively pay for itself. just a matter of selling the idea and this info will help. thanks for all for your input
In that case I’d just use the FLA numbers. Simple math and definitely covers the worst case scenario, and you can pass the red face test if someone ever inquires - “I used the manufacturers nameplate data.”
The heating element isn’t going to really use 3-phases of power to do it’s job, so you don’t need to use the complicated math for that. You can take the kilowatt rating at its word for its max power draw, although often these heating elements are not drawing 100% of the power they are rated for, even when running at “max” according to the device.
The motor is the only actual 3-phase component and the standard calculations for that will apply.
To make it easier on yourself just use the FLA ratings on the device, consult an electrician for sizing the breakers appropriately. You really wont know what the device is drawing until you put it in operation and have a device that monitors the current load. We had a wireless device that did this for the total power draw at our service connection in a facility I helped design. I have no idea what the brand was, but it was cool as fuck to be able to watch power consumption in real time.
