But wait theres more.... flexwatt questions!!!!!!!!

[zeke]

ok so I am puttin flexwatt into place, the tank sits on a wooden shelf. My question is can I put tinfoil between the flexwatt and the shelf and be safe in doin that? I will be using foil tape to hold the flexwatt in place. Also can I cut the flexwatt inbetween the black lines? The flexwatt I have is the 11" but i need to cut the length down some is it doable?? Thank you in advance


Cheers

[zeke]

Anyone?

[ctrlfreq]

My question is can I put tinfoil between the flexwatt and the shelf and be safe in doin that?

Possibly, but I wouldn't due to the potential of a short. The flexwatt will be fine secured directly on the shelf by the foil tape.

Also can I cut the flexwatt inbetween the black lines? The flexwatt I have is the 11" but i need to cut the length down some is it doable?

No, do NOT do this. Either get smaller tape, or shift the 11" tape back to where some hangs out from under the tub, but DO NOT CUT it.

With flexwatt it's not the size, but the wattage density (watts per square inch) that determine the amount of heat given off. As such, 3 inch flexwatt at 6 watts will get hotter than 11 inch at 20 watts because it's more dense, and if you shorten an 11 inch piece, you will be concentrating that 20 watts across say 5 inches, which WILL result in failure, possibly burning the flexwatt and anything on it.

[mykee]

Watts/foot, not watts/sq. inch.

[Adam Chandler]

I don't work with flexwatt enough to give a good answer. But here is a Flexwatt FAQ that might give some info you need. http://www.reptilebasics.com/flexwatt-faq.html

If not I would contact Rich at ReptileBasics.com(http://www.reptilebasics.com/help.ph...us&mode=update). He wires up all my flexwatt projects. The guy is pretty handy with the stuff and might have the info you need.

[zeke]

Possibly, but I wouldn't due to the potential of a short. The flexwatt will be fine secured directly on the shelf by the foil tape.



No, do NOT do this. Either get smaller tape, or shift the 11" tape back to where some hangs out from under the tub, but DO NOT CUT it.

With flexwatt it's not the size, but the wattage density (watts per square inch) that determine the amount of heat given off. As such, 3 inch flexwatt at 6 watts will get hotter than 11 inch at 20 watts because it's more dense, and if you shorten an 11 inch piece, you will be concentrating that 20 watts across say 5 inches, which WILL result in failure, possibly burning the flexwatt and anything on it.

ok thanks, I didnt use the tinfoil, it is just taped with the foil tape and is sitting on the shelf.. thanks for the info on not cuttin between the lines.. never thought of the wattage..


Thank You all for the info and help.

Cheers

[ctrlfreq]

Watts/foot, not watts/sq. inch.

You need to reduce it to the sq.in in order to compare the output of of different widths of tape. For instance, a foot of 3 inch/10 watt tape puts out quite a bit more heat at full blast than a foot of 11 inch/20 watt tape because it's wattage density is almost double.

[Gloryhound]

Watts/foot, not watts/sq. inch.

This is correct!

I just disected a piece of 11" flex watt to verify what I already thought through my knowledge of electricity.

One 11" piece of flex watt uses 20 Watts with 120 Volts applied. Since Amps is equal to Watts/Volts we get 0.1667 Amps per foot. Since Resistance is equal to Volts/Amps we get 720 Ohms of resistance per foot of 11" flex watt.

I measured the Resistance of the single foot long peice of flex watt and got 721.2 Ohms. I measured the Voltage at my power outlet and got 117 Volts AC. I powed up the piece of flex watt going directly into the power outlet and used my clamp on Amp meter to read the current and got 0.161 Amps. Going back and doing the math everything came out within acceptable ranges given my voltage supply was not up to the 120 VAC used in origional calculations. 745 Ohms for the Flex watt and a total power use of 18.8 Watts Given the added resistance of the power cord and Lower supply voltage I kinda expected the lower wattage reading.

Now since the 11" flex Watt I have has 90 little black lines in a zig zag across it and at the ends they are tied into groups of 3 it cutting it perfectly in half was not an issue. I cut it in half at the between lines 45 and 46 and this even allowed me to keep the groups of 3 in tact. I was very careful to follow the Zig Zag and make sure none of the little black lines were nicked or cut.

When I measured the Resistance it came back at 1444 Ohms. This is exactly what I suspected and doing the calculation of the Volts applied 117 VAC divided by Resistance of the circuit I came up with a current draw of 0.082 Amps. Then calculating for watts I multiplied applied volts by calculated current and came up with 9.59 Watts of power consumption. That is pretty close to half of the advertised 20 Watts for half a piece of flex watt. I plugged it in and again used my clamp on amp meter and read 0.08 Amps which translated into 9.3 Watts of power being used.

Now for anyone with further doubt on this idea we can also get into the conversion of Watts into units of heat or BTUs.

With that said, yes you can cut an 11" piece of Flex-Watt in half and use it without it developing any more heat per square inch of surface than if it was its full length. Full length will give you 1.14 BTUs of heat a minute and half length will give you 0.57 BTUs of heat a minute. But, you must make sure you do not damage any of the connection points of the little black traces going across the flexwatt to the silver edge connector.

[zeke]

thats way too much info in one shot. But I'll try to retain it all.. thank you all for the info and help. I did not cut the flexwatt, it is just over hangin a lil bit.

Cheers