Partial Electric Using a Variable Transformer

[Ravenshead]

I'm looking to save on propane by adding a 1500W-ish 120 V water heater element to my keggle. I plan to use it to maintain my boil once I reach it with my propane burner. I have a 0-140V 10A variable transformer I can use to control power.

Is 1500W enough to maintain a 7 gal or even 13 gal boil?

 

[Ravenshead]

Here's the transformer. I think it's older than I am.

 

[passedpawn]

Sure, not a problem for 5g. Might need to insulate it well though. WIth good enough insulation, you could keep the boil on the 10g going.

I think you can change the brushes on those old autotransformers. If it gets flakey, look into that.

 

[DaleHair]

with 1500w I don't think you will need that gizmo

 

[Ravenshead]

Excellent, I'm looking forward to a quiet brew day next time. My crawfish boiler sounds like a jet engine.

The transformer at this point still works like a champ controlling drill speeds.

 

[Junkster]

1500 watts is probably a bit much for that transformer if it's only 10A.

 

[Ravenshead]

1500 watts is probably a bit much for that transformer if it's only 10A.

Why, it goes up to 140V so the transformer will limit the draw of the heater to 1400W. I'm losing 100W to gain control of the element. Since I'm just maintaining the boil with the heater (I'll use the jet engine to get it there), I'm not too worried about the 100W.

If I find later that I never turn the tranfomer below 140V I'll remove it from the system.

 

[DaleHair]

a 1500w heater at 120v will draw 12.5 a, if you give it more volts it will draw more current, less volts less current. You give volts it draws current.

 

[Ravenshead]

That's only true if you let yours amps float.

I'll put a multi-meter on it tomorrow but I'm pretty sure it puts a out a constant 10A. Varying the voltage varies the power which how it works to control motor speed. It should work the same way for a heater output.

 

[Junkster]

What DaleHair said..... Test it and report back - I'm curious!

 

[SimBrew]

it's not your variac (transfo) that limit the current, it's good for 10 but it will deliver 15a or 20a but it will burn.

 

[wilserbrewer]

IME a 1500w element really does not need control. It is not capable of boiling, let alone boiling over, why bother to limit it?

 

[Ravenshead]

it's not your variac (transfo) that limit the current, it's good for 10 but it will deliver 15a or 20a but it will burn.

You're right there. In fact, I kept burning fuses when I put an amp-meter on it so it's definitely isn't a constant current supply like I was thinking.

It just goes to show that I don't understand AC. Back in college, we used to read strain gages by measuring delta-V across a Wheatstone bridge using a constant current DC power supply. Or was that delta-A with a constant voltage supply?

I can't remember but that was the theory I was working off of with this thingy. Obviously that part was wrong.

Either way, I'll try using the 1500W heating element to maintain a boil with or without the controller unless someone tells me it's not enough to even maintain the boil.

 

[SimBrew]

On a 5 gal batch if it even maintain a boil, it will not be that much and won't need any control.

 

[Ravenshead]

Amazon has a 2000W 120V heater. I may go with that since I don't have a good way to run 240V at this time.