How can I reduce the output of this heating belt?

[DuncB]

I have a couple of these 100W heating belts which I wrap around my fermenters ( PET ), only one per fermenter.
They are a little too powerful I think, controlled either by Brewpiless controller or STC 1000. The other 30 watt heating belt I have seems to work fine for my purposes.

I am on a 220V supply.
Would using a 110V transformer reduce the power output? I do have one of these, it is rare that I'm using three heating belts at once.
Could I cut a couple of the wires ( safely ) to halve the power output ?

Some form of rheostat? Although might be cheaper to buy a 30W belt.

Thanks

 

[day_trippr]

You could rewire those to use NEMA 1-15P plugs (ie: conventional two pin 120VAC plugs in the USA) which would drop the power to 25 watts...

Cheers!

 

[DuncB]

You could rewire those to use NEMA 1-15P plugs (ie: conventional two pin 120VAC plugs in the USA) which would drop the power to 25 watts...

Cheers!

My house supply in NZ is 220 V so not sure using a conventional 2 pin plug modified to fit in our sockets ( this can be done by bending the vertical prongs of the plug to fit the 45 degree angle of our sockets ) would work as there is no stepdown with a plug.

 

[whoaru99]

My house supply in NZ is 220 V so not sure using a conventional 2 pin plug modified to fit in our sockets ( this can be done by bending the vertical prongs of the plug to fit the 45 degree angle of our sockets ) would work as there is no stepdown with a plug.

Yeah, I think trying to use one leg won't work there. If I recall, it's 220V line to ground there, not 120/240V split phase like here in US.

 

[day_trippr]

Ohhh. Ok, I'm a *******, didn't even look to see where you're located. Like most of the world you don't have the 240vac/120vac split phase thing we have in the USA so my approach would definitely not gain an iota. Sorry...

 

[whoaru99]

I'm thinking a standard light dimmer might do the trick since it sounds like you're not looking for closed loop temp control.

Another way could be to run a light bulb in series with the belt. Different wattage of bulb would give different wattage from the belt. But, I believe it'd have to be a standard incandescent bulb, not a LED bulb.

 

[MaxStout]

Ohhh. Ok, I'm a *******, didn't even look to see where you're located. Like most of the world you don't have the 240vac/120vac split phase thing we have in the USA so my approach would definitely not gain an iota. Sorry...

OP did mention having a 110V xformer, so your original calc would work for 25W.

 

[day_trippr]

^That^ would indeed work. As would a "dimmer", assuming they have those in NZ (not gonna assume anything more in this thread ) or a rheostat. It might be a close call which option would be least expensive vs buying a 25 watt brew belt - other than using an existing step-down transformer...

Cheers!

 

[DuncB]

OP did mention having a 110V xformer, so your original calc would work for 25W.

I thought halve the voltage halve the output, there is a lot of A level physics I've forgotten.

 

[DuncB]

^That^ would indeed work. As would a "dimmer", assuming they have those in NZ (not gonna assume anything more in this thread ) or a rheostat.

Cheers!

It's behind the times here but we do have dimmer switches.
The consensus is use my transformer and or get a dimmer switch.

Cutting wires hasn't been suggested and it seems risky with potential liquids etc around.

 

[day_trippr]

I thought halve the voltage halve the output, there is a lot of A level physics I've forgotten.

Yeah, it never seemed right to me either, and I was an EE by trade, FFS

But, in short, power is proportional to the square of the voltage, so reducing the voltage by half results in the power being reduced to 25% of its original value...

Cheers!

 

[whoaru99]

Cutting wires hasn't been suggested and it seems risky with potential liquids etc around.

The problem with cutting the wires is it could be a series circuit. Cut one and you might have no heat at all due to an open circuit.

Personally, I try either a lamp dimmer or a bulb in series. Either of those facilitates some variability, dimmer easier of course.

But, a series lamp would work. 100W lamp in series with your 100W belt would get you something around 25W from the belt. A 200W lamp in series would get you something on the order of 45W from the belt (presuming I did it right).

 

[DuncB]

Thank you
Now to find that transformer, must have bought it last century to use on a device when living in England. I'll bet it doesn't work when I find it!

 

[whoaru99]

There isn't much to go wrong with a transformer unless it was overloaded or connected to higher voltage and burnt/damaged.

 

[MaxStout]

Was an EE many years ago. Used to keep this handy.

 

[DuncB]

Little physics refresher completed, won't forget Ohms law for a while now.

 

[Lalo_uy]

You could wire 2 belts in serie and got the same 25% power.
Oulet a to belt1 a
Belt1 b to belt2 a
Belt2 b to oulet b

 

[day_trippr]

But that would mean 50 watts net...

 

[Lalo_uy]

But that would mean 50 watts net...

No , 25w. Duble de R, 1/4 Pw. But could be enough for a 20L pet. And zero cost.

 

[MaxStout]

P = V^2 / R

Power drop is inversely proportional to the resistance. If resistance is doubled, power is cut in half. Basic Ohm's Law. See the power diagram I posted above.

 

[whoaru99]

No , 25w. Duble de R, 1/4 Pw. But could be enough for a 20L pet. And zero cost.

I believe he's meaning the series string would be 50W total, 25W per belt.

While no extra cost in hardware, 50W cost more to run than 25W, but would less than 100W.

 

[HighVoltageMan!]

Each belt is @ 484 ohms. In series that would be 968 ohms. 220 volt/968 ohms = .227 amps. 220 volt x .227 amps = 50 watts.

It's the long way to figure the math, but it is the correct answer. Basic Ohm's Law. Light dimmer is the easiest answer, it would make the heater completely adjustable from 0 to 100 watts.

 

[MaxStout]

Each belt is @ 484 ohms. In series that would be 968 ohms. 220 volt/968 ohms = .227 amps. 220 volt x .227 amps = 50 watts.

It's the long way to figure the math, but it is the correct answer. Basic Ohm's Law. Light dimmer is the easiest answer, it would make the heater completely adjustable from 0 to 100 watts.

Username checks out. And your math is spot on.

 

[mac_1103]

Username checks out.

Just don't ask him any 12 volt questions.

 

[DuncB]

Interesting extra idea, will try the transformer first.

 

[RM-MN]

Separate the heating belt from the fermenter with a bit of insulation. It doesn't need much. Experiment with how much.

 

[dtashmore547]

another option is to put a 1n4005 or 1n4007 in series with the belt wired into the plug will halve the power

 

[dtashmore547]

sorry they are 1Amp rectifiers so would only allow one half of the power through.

 

[whoaru99]

Yeah, that's an option too I'd forgotten about. I used that technique in the past to make a high/low power point for a soldering iron using a diode and split wired duplex receptacle.