alternate heating - will it work?

Discussion in 'Filters, Pumps, etc..' started by el_piraña, Mar 26, 2010.

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  1. el_piraña

    el_piraña Flamingo Tongue

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    I've been thinking about an alternative heating choice for my 55 gal aquarium. I haven't bought heaters yet, so now's the time to decide.

    I may have a source for some heater 'pads'. I'm not sure what they are necessarily called. It is essentially a resistor that dissipates heat through the pad that it's built into. You can attach them easily to various surfaces.

    I'm thinking about adhering several pads to the bottom of the glass tank - on the outside of the tank. Power could be turned on and off by a normal thermostat type circuit.

    This is one of the heater pads...

    [​IMG]

    The heat would just radiate up through the glass and substrate. I don't have a sump where other heaters could go and I like the idea of keeping things out of the display tank if possible.

    Does anyone have any opinions on this? Any reason why it wouldn't work?
     
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  3. Telgar

    Telgar Snowflake Eel

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    two conserns, not sure of the long term effects of the heat source directly on the glass bottom of the tank and second is the danger of spilled water reaching the pads electrical, pretty sure its not waterproofed.

    It is an interesting idea and I have considered it a few times while in the lfs and seeing those reptile heating pads.
    Another option might be the cable heater that is used under the substrate in planted tanks, but I don't know what the temp range is for those.
     
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  4. pgoodsell

    pgoodsell Horrid Stonefish

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    It might work, but would be a less effective way to do it. Your heating the glass first then then water. It would take a lot of them and cost more in electricity than a regular in tank heater. And then I'm not even sure if you could get enough to heat all that water to 78. Just my opinion.
     
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  5. pgoodsell

    pgoodsell Horrid Stonefish

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    Also the substrate would cause another problem in that it would tend to trap the warm water at the bottom.
     
  6. Tangster

    Tangster 3reef Sponsor

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    Radiant heat will work but unless you insulate the heating element in between the glass with a reflective type of Styrofoam then its a lot of heat loss and in the summer the insulation will need to come off to keep tank cool . Its doable alright just not that efficient like radiant heated floors waste alot of fuel needed to heat the water to heat the pips then to transfer that heat to the floor then heat loss in the flooring . The media on thebottom would be of no conceren as it will radiate quickly and trap no heat at all as its in direct contact with the water and the warmer water will move to the cooler water fast .
     
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  7. fischkid2

    fischkid2 Dirty Filter Sock

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    so the tank would sit on the pads? wont it get squished? your looking at ~500lb on top of the pads. would be interesting to see set up tho. maybe the gravel would retain the heat and keep the tank warmer for longer..
    IMO i would just go with a known submersible heater tho and not risk the possibility that it does not work well. if you find out the heat pads are not great then you would have to remove all the water just to remove them.
     
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  9. el_piraña

    el_piraña Flamingo Tongue

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    Thanks for all the ideas!!

    The tank's bottom glass panel is actually raised...maybe 1/2" above the bottom of the sides. I think this is a somewhat common way that glass tanks are built from what I've read. The tank is sitting on one of those old cheap steel framed stands. Only the outside panels are sitting on the stand, there's no support across the middle. So the heaters won't be smashed in between the tank and the stand.

    The heater pad I showed is 36W, but it's only like 2" x 2" in size. I figured somewhere between 5 to 10 pads would work. 10 heater pads would be 360W of heat.

    The specs are 36W, 24V. So it'd be around 1.2A of current flow for the full output power. I think I could put 5 pieces in series and run 115VAC through it.

    If I have a thermostat to control it, then it should be ok in summer.

    I don't have water in the tank yet....maybe it'd be a good experiment?? ;D
     
  10. NASAGeek

    NASAGeek Eyelash Blennie

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    I would think that this would not work well at all from an energy and cost point of view.

    1) only a small fraction of the heat will make it to the actual water.... heat would have to travel from heat strip to glass, glass to substrate, substrate to water. That is a LOT of thermal insulation and conduction inhibitors... it would be extremely inefficient heat transfer.
    2) delta-T required would be huge.... with all those inhibitors you'd need to get the heat strip very hot to get a meaningful temp change in the substrate.
    3) poor heat heat transfer to water.... the water flow rate along the surface of the sand is where the heat transfer would occur... this isn't an area for particularly high flow, thus, it would make the situation worse.

    I could go on... all these inefficiencies will both make it unsafe and dramatically expensive to operate.

    Contrast this to a regular heater... emmerse in fast water flow next to sump pump.... heat transfer directly from heater to water... no losses.... heater emmersed in water .... no losses.... small delta-T directly heats water.... high flow rate... a FAR more efficient solution... very hard to beat.

    Sorry for saying "No Go" on the idea.... I explore 'out of the box' ideas frequently and get shot down, but only by exploring do we discover new things. I would encourage to continue seeking new ideas.... but not this one.

    Mark.... the resident NASA guy...
     
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  11. Powerman

    Powerman Giant Squid

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    I agree with the above. Placing the pads under the tank would not be very good. If you placed the pads on the back glass, that would be better cause it would not have to go through the substrate. However, to be efficient, it would still need to be insulated.

    Another reason for it being a bad idea is thermal expansion. You are heating one of your panes of glass.... that will expand at different rates than all the colder ones... and that could be dramatic depending on how hot the pads get. This might not be a problem immediately.... but most people cringe at the thought of coming home to a blown out tank no matter how remote the possibility. I would hate for this to increase your odds in a bad way.
     
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  12. Powerman

    Powerman Giant Squid

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    Actually, now that you mention it, it might even effect the substrate in a negative way. If convection is carrying heat up, it might not do the job of dentrification, and perhaps it would effect worms and others critters that would normally keep it clean.