Heat

[cluelesshillbilly]

How much heat could I produce if I assembled four 25 ohm, 25 watt, Cement Type Wirewound Resistors in front of two fans in a 4 cubic foot space? I was planning on housing them turned 45 degrees (for better aerodynamics) in a small metal box with two 2 inch fans recirculating the air in the enclosure over the resistors.

The specs:25 ohm, 25 watt Wirewound Resistor from Madisound
5mm Ø Ceramic Core, Perfect Winding, Solder plated copper leads, 10% Tolerance"

25 watt resistor dimensions

60 mm long
14 mm tall
15 mm wide
35 mm long leads

Thanks Everyone!

 

[cluelesshillbilly]

**broken link removed**

 

[smanches]

1W == 3.412 BTUs.

 

[cluelesshillbilly]

Do you believe this will keep the space above 80 degrees F? 4 cu ft

 

[Ubergeek63]

Do you believe this will keep the space above 80 degrees F? 4 cu ft

that depends on what the temp is outside and how well insulated it is

 

[cluelesshillbilly]

Made of r16 foam board in my garage (about 50 degrees).

 

[cluelesshillbilly]

Also I forgot to ask what amperage are these going to pull? I need to grab the appropriate power source.

 

[tcmtech]

4 amps at 25 volts. 100 watts or 341 BTU's.

At an R16 rating the box should easily get well over 100 F above the ambient external temp in a few hours or less.

 

[Ubergeek63]

for 25W they will take 25V@1A

 

[cluelesshillbilly]

4 amps at 25 volts. 100 watts or 341 BTU's.

At an R16 rating the box should easily get well over 100 F above the ambient external temp in a few hours or less.

Thank you very much! Now all I have to do is tackle my first actual electronics build since 2004 during my naval training. This is just as simple as 12v (with the apropiate amperage) power source and a on off toggle and an inline fuse right?

 

[cluelesshillbilly]

for 25W they will take 25V@1A

two seperate power sources for the fan and resistors, got it.

 

[Ubergeek63]

two seperate power sources for the fan and resistors, got it.

that is 1A each.... what the heck? are you sitting there hitting refresh with bated breath?

 

[BrownOut]

P = I^2*R, rearranging:

I = sqrt(P/R)

= sqrt (100/(25/4))

= sqrt(16) = 4 amps

The voltage is:

V = I*R = 4*25/4 = 25Volts

A supply of 25 Volts and 4 Amps for the resisitors only. The fans will draw additional amperage.

 

[MikeMl]

I have placed a 10W lamp in a small foam beer cooler, and the insides got well over 100degF. With 100W, you will start a fire, or a least create a molten puddle of urethane...

You dont need the fans. Convection will stir the air such that the temperature will be quite uniform. Or dump the resistors, and use only the fans. They dissipate about 3W apiece, which will just about heat the box by themselves....

 

[cluelesshillbilly]

P = I^2*R, rearranging:

I = sqrt(P/R)

= sqrt (100/(25/4))

= sqrt(16) = 4 amps

The voltage is:

V = I*R = 4*25/4 = 25Volts

A supply of 25 Volts and 4 Amps for the resistors only. The fans will draw additional amperage.

I knew someone would take it over my head. lets just say I solder these up in parallel and supply them with a 4.5 amp fused 24 volt source then hook the 500ma source I already have for my fans and switch the power on it will all work?

 

[BrownOut]

lets just say I solder these up in parallel and supply them with a 4.5 amp fused 24 volt source then hook the 500ma source I already have for my fans and switch the power on it will all work?

It should work. You'll just get slightly less than the full 100 Watts.

 

[cluelesshillbilly]

I have placed a 10W lamp in a small foam beer cooler, and the insides got well over 100degF. With 100W, you will start a fire, or a least create a molten puddle of urethane...

Guess I'll drop that to two resistors and build it from wood. I am building a brooder for my hatch and I'm kind of on this build my own ^%*$ kick. Keeps me off the streets and occupied at work.

 

[cluelesshillbilly]

I should work. You'll just get slightly less than the full 100 Watts.

Thank you, for your help and working around my ignorance.

 

[cluelesshillbilly]

that is 1A each.... what the heck? are you sitting there hitting refresh with bated breath?

Yes I need help I thought that's what this forum was for. I am a diy kind of guy and you guys are experts. I apologize if I need more help than the more technically savvy members.

 

[BrownOut]

Those who have notification turned on can dang near communicate in real time. It's all good though.