Power Frequency of Heating Element

I found a heating element that's 4000W / 230V / 50HZ

Can a 50HZ element be used? Will it change anything like the Amps drawn?

 

Can't be used AFAIK, in the US our power is 60Hz. If I'm wrong about this someone please chime in.

 

Anyone?

Some stuff I could see not working properly, but I'm not sure about a heating element.

 

Unless there's something special about this specific element (attached electronic controller, etc), heating elements are just resistors. Should behave the same at any frequency.

 

230/50hz is Europe. Link to the element?

 

Yeah, I REALLY don't think the frequency of the power matters.

When I was in the Army in Europe, we used a US clothes iron with a transformer. It worked then, and still works.

 

The Hz doesn't matter.

But note that it is a 230V element. If you run it at 240V, you will get more than 4000W out of it (4366W, to be specific).

Edit: if you run it at 220V, you will get 3660W out of it.

 

Shows that I only know enough about electric to get in trouble.

I thought that the 4000W wouldn't change if you went from 230V to 240V.

I thought that the amps drawn would go from 17.4 to 16.7.

So, you're saying that the amperage is constant and the wattage changes?

 

No, the amps are not constant either. The only thing constant about it is that it is a resistor of a certain size. The "rating" they give you always specifies a wattage and a voltage, which means that you will get 'that' wattage if (and only if) you run it at 'that' voltage.

Run it at any other voltage and the current drawn and power produced start to change.

IN this case, advertised as 4000W/230V, the thing is a 13.2 Ohm resistor. The math for this is based on two basic electrical equations.

P = I * I * R
and
V = I * R, which is the same as I = V/R

So, plug that back into the Power equation as
P = (V/R) * (V/R) * R = (V*V*R)/(R*R) = (V*V)/R
and solve for R
R = V*V/P
R = 230*230/4000 = 13.2


If you put a 13.2 Ohm resistor on 120V (as an extreme example)...

V = I * R
120 = I * 13.2
120 / 13.2 = I = 9A

And Power is

P = I * I * R
P = 9 * 9 * 13.2 = 1089Watt

 

Ahhh. So, it's the resistance that is constant to the element.




I took and course in electronics about 35 years ago while doing my toolmakers apprenticeship. Those equations look familiar, but I'll file that under "use it or loose it."

Thanks for setting me straight.

 

No problem. Glad to help.

The fact that the element is a fixed size resistor seems to be something that a lot of people miss, even some of the folks that know how to build these electric systems pretty well.

One nifty thing about it is that you can use this to your advantage if you want a super low density heating element. You can take a 6000W/240V element and run it on 120V, which makes it only 1500W.

I would NOT suggest going the other way with that and run a 1500W/120V element at 240V to turn it into a 6000W element.

 

Firstly, add me into Walker's disclaimer
Another thing I have seen is the ratings even for the same country are somtimes higher or lower depending on who's specing it. From what I understand is you are never going to get exactly 230/240/22/110/120/or what ever voltage they say is coming out of your wall. For some reason a number of +/- 5%(or was it 10%) comes to mind.
This point is made constantly on this board if you pay attention as everyone states a different voltage for over there in the USA, I have seen 110/115 & 120V stated for single phase voltage. I think I have also seen someone say 110V single phase and 240V between phases.

 

Yup... That's also something to keep an eye on.

I suggest people check thair actual voltage at their house so that they know what they are really getting.

I actually measured 243V on my brewery outlet and (appropriately) 122V on my standard sockets elsewhere in the house.

My buddy measured 222V and 111V.

 

I am an electrical engineer. What Walker said is all true for resistive loads. Heating elements are resistive loads. As such, they can be used at any frequency you like. I could go into the math and a few useless disclaimers but that is more likely to cause sleep than anything positive.

A 50hz heater is fine at 60hz.

 

What is the best/safest way to go about that? We all have been told from a young age not to go sticking this (other than plugs) into the wall sockets

Also Charlie what happens with an inductive load (say a pump) running a 60hz on a 50hz supply, does it just go slower or do things mess up. I have noticed the pump curves (from march) show the 50hz have lower head/flow and wondered if there was a difference in the motors or not for the 50/60hz models.

 

In this case, you are going to need to stick something in the outlet. I suggest a voltmeter.

As for inductive loads (as opposed to purely resistive loads)... That's a whole differwnt ball of wax. I am not refreshed enough on inductors to comment (haven't done any work with them since the middle of my electrical engineering degree in the mid 90's).

 

110V, while used in the past, is no longer used and is out of spec with US standard. 120V +/- 5% is what's delivered now. Substations dynamically compensate for load so what's seen at your house should be really close to 120V. If there are other in-house loads on the tested circuit, they will cause a voltage drop, of course.

 

For this post, there are 2 types of electric motors, both inductive. One is the type used in drill motors. Its speed and current are not dependent of frequency but is on voltage and load. The second is the type generally used on pumps. There speed in rpm will be the (frequency * 60 - the slip frequency) * 2 / number of poles. Usually, the slip frequency is 150Hz and there are 2 poles. So a standard motor will spin at 3450 rpm @ 60hz or 2850 rpm @ 50hz.
60hz ~ 60 * 60 - 150 = 3450 rpm
50hz ~ 60 * 60 - 150 = 2850 rpm

These motors will attempt to pull whatever power required to maintain that speed. So, if you use long extension cords, and have a XX% voltage drop you will have a XX% current increase. This can cause the wires inside the motor to over heat.

 

Why not? It could be...EXCITING. For a second or two.

 

Sweet, so you are saying that there is no such thing as a 60 or 50 hZ pump just it will run at a different speed (hence the lower head/flow).
Cheers

 

60 hz 4 pole : 1800 RPM - Slip
60 hz 2 pole : 3600 RPM - Slip

Slip is dependant on Motor design. Ac motors also will draw anywhere from 30% - 50% rated current just for magnetizing before they even produce torque as well.

 

Is the power company required to maintain that within the +/- 5%? When the temperature gets over 90 they seem to think it's OK to drop us back to 100-105V. I can't see that as being good for anything computer related or possibly other electric devices. The florescent lights in my shop start to flicker around 105V.

 

The power company is king. They pretty much do what they want or need to do. They drop power across the board to prevent blackouts. I had an issue once with a system wide power surge and got the utility to reimburse me for a fried network device. YMMV

 

They have to lower the voltage as the temp goes up especially if they have old transformers. Their transformers are oil submerged and as the temperature goes up their permittivity and permeability change and they are also more likely to break down and arc, so if they dont lower the voltage you may blow a transformer.

Not only that but as the temp goes up more people pull a lot more power for air conditioning which means the line voltage will drop as they cant supply enough current to keep the voltage up under high load, so they are just load leveling.

I dont know the spec, but my "220" line measures 248 RMS and my "110" line measures 120 RMS. They can vary a fair amount. Keep in mind that normally in a system within 10% is good enough, and at 120v RMS that means 12v.

 

Remember that your pump motor also runs its cooling fan. If you run a 50Hz motor on 60Hz, the motor turns faster, slightly increasing the cooling capacity of the fan. If you run a 60Hz motor on 50Hz, it turns slower, reducing the cooling capacity. Probably not enough to worry about in open air, but if you have your 60Hz motor running on 50Hz, enclosed in a box, it may get a little hotter.

We have a few machines here at work that we got used from England. The hydraulic pump motors are rated for 50Hz, but we run them here on 60Hz with no problems.

Again, as far as heaters go, any frequency is fine, you can even run them on DC (0Hz).

 

The safest way is to purchase a kill-a-watt, but a voltmeter will work fine also.