Pablo Posted August 31, 2005 Report Share Posted August 31, 2005 Looking to fabricate an under tank heater for a new 1.8m x .5 x .7 tank, I have 8.5m of pyrotenax cable (with tails) which was made for a plant propagating bottom heat set up, but never used. I have yet to measure output, but can regulate it. also have self regulating chromalux (33 watts / metre) freezer door heating cable (about 4.5 m) any ideas which would be better to use? also, will use a styrofoam base and router out a groove to lay the cable in, any ideas for a high thermal conductivity base to dissapate the heat across the glass? Thanks in advance. Quote Link to comment Share on other sites More sharing options...
Sharkey Posted September 1, 2005 Report Share Posted September 1, 2005 I'm confused why this system and not a Normal heater? Quote Link to comment Share on other sites More sharing options...
HandS Posted September 1, 2005 Report Share Posted September 1, 2005 I have often thought of this but never done it. The method i would use\try is to cover the inside botom ot the tank with a thin layer of silicon,lay the heater wire in strips the length of the tank aprox 5-10cm apart, poaking the ends out one corner to the outside. Place a 5mm peace of glass cut to fit the inside of the tank on top of the wires before the silicon sets, then run a bead of silicon around the edge. there would be a thermostat in there for temp control but havent thought to much in depth about that, it would probably involve old heater parts. Hope this helps give you some ideas :lol: Quote Link to comment Share on other sites More sharing options...
Caryl Posted September 1, 2005 Report Share Posted September 1, 2005 We have 2 tanks with undertank heat pads (home-made). I suggest the longer cable laid out on top of the styrofoam so that it covers it as evenly as possible. You can then place the tank straight on the cable as long as the gaps between adjacent parts of the cable are small the glass will handle it without any problem assuming everything is perfectly flat. That is how we made our heat pads using electric blanket wire laid out on Pinex board. We didn't make grooves for the wire, the tank just sits on top. We have polystyrene under the Pinex for added insulation. This tank (1.2 x .5 x .5) has been running over 10 years now and never missed a beat (or leaked). It is important to place the tank on the cable without moving it sideways to prevent damage to the cable. heat contact with the glass is fine so heat losses are low. Ensure everything is well sealed for safety and run it off an RCD for added safety. Sharkey we did this cos it was cheaper, worked well and meant no hardware in the tank. Quote Link to comment Share on other sites More sharing options...
DiverJohn Posted September 2, 2005 Report Share Posted September 2, 2005 I actually emailed the people who make the "Nuclear mirror demister" for a 500l (5foot) tank. They do a range of other heat pad products/ sizes as well as a cut to lenght option... Word from them was as per Caryl. Just straight onto poly' then tank on top, can handle load, but no movement. I thought maybe a layer of plain tinfoil between poly and cable but apart from that it seemed a good idea. Just wondering tho.. why dissapate heat across the glass? I thought the idea of heater cable was to create a thermocline type circulation in your substrate? Hence hot spots + cold spots? John Quote Link to comment Share on other sites More sharing options...
Alan Posted September 2, 2005 Report Share Posted September 2, 2005 Jan Payne and I use to make them and we would lightly staple them onto softboard, then cover with a vinyl. Worked fine. Looked very professional too. We also used a thermostat in line for contol of the heat. This looks similar to a heater-stat, but doesn't have the heater. It is in the tank. We use this system for heat control of our Killifish display stand. About 48 tanks. They are in three tiers and we only have six thermostatsfor the whole setup It, the stand, was used at the last National Show, that was held in Napier. So some of you may have seen the stand, but not realized the setup that we use. Alan 104 Quote Link to comment Share on other sites More sharing options...
Ira Posted September 2, 2005 Report Share Posted September 2, 2005 Just wondering tho.. why dissapate heat across the glass? I thought the idea of heater cable was to create a thermocline type circulation in your substrate? Hence hot spots + cold spots? My understanding is you're looking for the thermocline to be from the bottom glass upwards. Quote Link to comment Share on other sites More sharing options...
DiverJohn Posted September 2, 2005 Report Share Posted September 2, 2005 Yep your right Ira, but when i was thinking it through i decided that having cold spots would be better. I imaginged this is what happens??? End of the day its probably going to achieve the same result as spreading the heat. But when Pablo said... any ideas for a high thermal conductivity base to dissapate the heat across the glass I just thought $$$$ John Quote Link to comment Share on other sites More sharing options...
Pablo Posted September 2, 2005 Author Report Share Posted September 2, 2005 Thanks for feedback team, just received my tank (aqua one R2 180) didnt realise that under the bottom glass is a wafer thin layer of foam wrap? and custom wood!!! thermal conductivity of custom wood is 0.052w/m.k, now I am unsure whether the heat will get through all three layers? I suppose it will eventually?? path of least resistance? the styrofoam has a layer of aluminium foil each side. also I have picked up some thin heating cable that they use to heat under tiles etc 150 watts, which is a bit over capacity at the rule of thumb .1 ~ .2 watts per litre? 540 litres = 54 ~ 108 watts. methinks I will try a dummy run dry and measure heat rise of bottom glass over time, watcha think?? Quote Link to comment Share on other sites More sharing options...
Pablo Posted September 2, 2005 Author Report Share Posted September 2, 2005 Sharkey, I want to go this way as I want to optimise for plant growth, incl bottled CO2, realise that there is debate over value of bottom heat but this is the easiest time to do it and T. Amano thinks its a good idea so I'll truck along with his view. Quote Link to comment Share on other sites More sharing options...
Brianemone Posted September 2, 2005 Report Share Posted September 2, 2005 i wouldnt use one on a viaaqua tank unless you took the bottom off and put it in there Quote Link to comment Share on other sites More sharing options...
Sharkey Posted September 2, 2005 Report Share Posted September 2, 2005 Very interested in seeing how it goes, please keep us updated Quote Link to comment Share on other sites More sharing options...
Pablo Posted September 2, 2005 Author Report Share Posted September 2, 2005 Caryl, will use a RCD definately, for the whole tank, at the switchboard, therefore an auto reset after power interuption. the extension lead and multi box types are generally manual reset, right? John, I'll have to investigate this thermocline thing youve raised, had'nt considered that. Brian. is your reservation because of the types of materials and number of layers or some other reason? Is it viable to silicone the hot wire to the topside of the bottom glass then silicone a layer of heavy acrylic plastic (like the strips in the doorways of big Commercial Freezers that the forklifts drive thru), but one peice, sealed to the edges with silicone, therefore sandwiching the heater between the substrate and the bottom glass ???? Cant fit a glass sheet, in one piece in, because of the configuration of the bars across the top. appreciate all inputs, cheers. Quote Link to comment Share on other sites More sharing options...
Pablo Posted September 2, 2005 Author Report Share Posted September 2, 2005 Just been reading melatainomas postings, re Diana Walstads book, does anyone out there have it? does she advocate substrate heating or no?? Quote Link to comment Share on other sites More sharing options...
Faran Posted September 2, 2005 Report Share Posted September 2, 2005 Outstanding. I'm just making up an under tank heater for a 100cmx60cm (30cm tall) breeding tank. Was completely miffed on heating it properly so I decided to go with under-tank. Plan is to use electric blanket bits on poly and trial and error from there. Will be keen to see your results and compare. Thanks! Quote Link to comment Share on other sites More sharing options...
Alan Posted September 2, 2005 Report Share Posted September 2, 2005 Remember silicone does not stick to plastic There are systems, albeit expensive, that you can buy and fit into suckers and supports on the inside of the tank and of low voltage. These wires are covered by the layer of gravel on the bottom. I wont say where to get them from cause they don't support us. Alan 104 Quote Link to comment Share on other sites More sharing options...
Caryl Posted September 3, 2005 Report Share Posted September 3, 2005 Caryl, will use a RCD definately, for the whole tank, at the switchboard, therefore an auto reset after power interuption. the extension lead and multi box types are generally manual reset, right?. Yes Quote Link to comment Share on other sites More sharing options...
DiverJohn Posted September 4, 2005 Report Share Posted September 4, 2005 Hi Pablo, I wouldnt worry too much a bout the theory of it all... I was just trying to save some $$. I also IMO wouldnt worry about the silicone... but perhaps invest in a slightly thicker sheet of polystyrene. Over time the weight of the tank will push the cable into the poly'. If you are worried about damaging the cable maybe a double layer of black polythene between the tank and poly'. Its how the "Nu-clear" people recommend you do it when using their heat pads under seed raising trays in a nursary. john Quote Link to comment Share on other sites More sharing options...
Pablo Posted September 5, 2005 Author Report Share Posted September 5, 2005 Thanks for input, for those interested in developments, finally got enough arms and legs here to throw the tank over on its top, what my old eyes perceived to be custom wood underneath, as I peered up under one small corner, was in fact brown paper, stuck onto plastic. with foam on top. therefore, for future reference to others, putting an element underneath an Aqua R2 180 is a complete no brainer. I will now use the thin Tile heater under the second hand 6ft all glass tank I have, using the principles described by Forum contributors. I will use the 8.5 metre pyrotenax heating cable in the substrate of the Aqua one 180, stepping it down to 24 volts, which should produce about 250 watts, more than I need, but I will pulse it on and off by Thermostat. Cheers. Quote Link to comment Share on other sites More sharing options...
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