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spencerin
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# Posted: 10 Sep 2021 02:54pm
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I'm lookin at buying a specific 12V heat cable/tape on Amazon. The ad says it's self-regulating, with rated power of 15W/m at 10* C, "max maintain" temp of 65* C, and "max enduring" temp of 135* C.
Am I right in concluding that it takes the water temp up to 10* C (50* F) and then shuts off, that it can go up to 65* C in order to take the water temp up to 10* C, and that the max it can handle is 135* C? And how do these things self-regulate without an obvious thermostat?
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travellerw
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# Posted: 10 Sep 2021 03:52pm
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Your assumption of "that it shuts off" is not correct. Its a restive based heating element an no matter what will only consume 15W/m @ 10C (this is a power rating and has nothing to do with what its heating). It never shuts off.
The design of the heating element is such that even if you left it plugged in and sitting in open air, it will never go above 65C. So that would be the max maintain temp (in all the right conditions).
The max enduring temp is the temperature that it will be damaged. This is useful when the tape is used to keep a line clear that might have hot liquids pumped through it later. You can't pump anything hotter or it will damage the tape.
Not sure what you plan to use this for, but it may or may not work. If you are trying to heat a big container of water, it may not work. While it may keep the water from freezing, it won't get it warm in COLD weather. The losses on the container will probably be more than the watts the unit can put out. These tapes are mostly intended to keep pipes from freezing. However farmers use them to keep water troughs from freezing sometimes (water never gets hot, just above freezing temp).
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spencerin
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# Posted: 10 Sep 2021 04:06pm - Edited by: spencerin
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I'm using it to keep pipes from freezing.
The ad says, "cable automatically adjusts heat output as needed, based on surface temperature." Seems to me that it does, if not turn on and off, warm up or cool down, and thus that power draw would follow suit. Am I wrong on that?
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Brettny
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# Posted: 10 Sep 2021 04:23pm
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If it dosnt self regulate you can use a STC-1000 thermostat controller to set specific on/off temps. They can come 12v or 120v and have a digital readout along with a remote temp probe.
I used one very successfully to run chicken heat lamps many years in a row. it helped keep my every use low and give me a temp reading.
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ICC
Member
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# Posted: 10 Sep 2021 05:37pm
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A link to the item being considered?
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travellerw
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# Posted: 10 Sep 2021 05:41pm
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Quoting: spencerin The ad says, "cable automatically adjusts heat output as needed, based on surface temperature." Seems to me that it does, if not turn on and off, warm up or cool down, and thus that power draw would follow suit. Am I wrong on that?
LOL.. Sounds like marketing wank to me. %99 sure the stuff you are looking at just contains PTC heaters. Really just fancy materials that change resistance (and thus the ability to generate heat) with temperature. As they heat up, they "resist" less and thus draw less current. Eventually they reach and equilibrium and "self regulate". They are actually used in all sorts of common items (Glade plugin air fresheners are a common one).
Here more technical details if you are interested.
https://gmnameplate.com/resource-center/blogs/what-are-ptc-heaters
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spencerin
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# Posted: 10 Sep 2021 06:12pm - Edited by: spencerin
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Here's the link - https://www.amazon.com/Self-regulating-Heating-Anti-Freeze-Protection-Selection/dp/B0 99ZFK9JJ/ref=sr_1_11?dchild=1&keywords=12v+heat+tape&qid=1631311798&sr=8-11
I thought it could've been a marketing "catch". But, I read your link/article and it does say, "PTC heaters draw full power initially to quickly heat up and reach the optimum temperature. As the heat increases, the power consumption simultaneously drops." Maybe not the same as a thermostat, but seems close.
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ICC
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# Posted: 10 Sep 2021 06:44pm - Edited by: ICC
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Quoting: travellerw As they heat up, they "resist" less and thus draw less current.
Actually the reverse... as they heat up the resistance increases so they use less power and produce less heat.
https://gmnameplate.com/resource-center/blogs/what-are-ptc-heaters
https://www.youtube.com/watch?v=wZqiOA9dusQ
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travellerw
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# Posted: 10 Sep 2021 07:13pm
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Quoting: ICC Actually the reverse... as they heat up the resistance increases so they use less power and produce less heat.
True.. I had it backward (which is embarrassing since I work with stuff like that every day).. Oh well.
However, its not really like a thermostat as they don't cycle in and out. They start drawing high and within seconds they will start dropping their amp consumption, then eventually level out.
Since you are looking at a 12V version you need to make sure you power supply can handle it. When its first hooked up it may draw a ton of amps (probably up to 10 or 15), then wind down. At the rating specified it will average out to about 3.5A @ 12.8V for a 3 meter length.
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spencerin
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# Posted: 10 Sep 2021 08:10pm - Edited by: spencerin
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Why would it draw 10 or 15 apms when it starts up when it says 15W/m, which equals 1.17 amps/m at 12.8V? I'm looking at 1-2m lengths. I know there's generally a surge when an electric appliance kicks on, but 10+ amps seem far-fetched for something this small.
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ICC
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# Posted: 10 Sep 2021 08:42pm
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Quoting: travellerw first hooked up it may draw a ton of amps (probably up to 10 or 15), then wind down.
Total draw for the length? Maybe he normally works with longer lengths than what you are considering?
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ICC
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# Posted: 10 Sep 2021 08:44pm
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Quoting: travellerw Since you are looking at a 12V version you need to make sure you power supply can handle it.
That is always my biggest concern when working with something that supplies heat and where the power comes from batteries when the sun is not shining.
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spencerin
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# Posted: 10 Sep 2021 09:25pm - Edited by: spencerin
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My concern, too. Go solar or grid? I like solar in this instance because it's easier for me to service, and it'll also work when the grid is down.
But, what capacities do I need to get me through the night? I just want to run the pump (Shurflo 4048 high-flow) occasionally, and this heating element in the winter. I was thinking a 50+ ah deep-cycle SLA or gel batt with a 110W or 180W panel. I'm in southern IN, with unobstructed sunlight.
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Brettny
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# Posted: 11 Sep 2021 05:39am
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Your grid connected and want all this for a backup incase? Why not just build your plumbing with a single drain and an air compressor plumbed in? 3 valves and the flip of switch along with a drizzle of a antifreeze in every drain.
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spencerin
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# Posted: 11 Sep 2021 08:14am - Edited by: spencerin
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Grid-connected, yes. But, the pump isn't wired yet and is in a pit below ground. Grid power needs to be trenched to the pit and rectified. Or, I could do a small, stand-alone solar system. Not sure yet which I want to do.
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gcrank1
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# Posted: 11 Sep 2021 11:03am
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A small, stand alone solar system will power some led light bulbs, usb ports, light duty stuff; imo Not resistance heating elements. Well, unless you want to spend $1000 and up.
If one has grid power available use a 'hot-tub' type breaker box and keep it simple.
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ICC
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# Posted: 11 Sep 2021 12:06pm
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If I had reliable grid power I would use grid power. Probably look for 120 VAC heat tape to be able to skip the 12 VDC conversion. But if that 4048 pump is 12 VDV then I'd Consider a converter or skip right to my next plan....
If I had grid power that was iffy at times I would consider 12 VDC tape and a battery plus a good 3 stage charger. I believe the Iota brand can be used as a smart charger or a power supply converter.
If I wanted to get into solar and power other stuff as well, I'd do my solar planning with that in mind and do it "right".
Does your area have grid tie net metering?
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ICC
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# Posted: 11 Sep 2021 01:24pm
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Also, if there is a battery involved in this, how about freezing weather? If a lead acid type is depleted to 50% it will freeze at about -10 F IIRC.
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