What heating element to use? - Page 1
Forum section: electronics / general

author: Jane
author_rank: Frequent Contributor
timestamp: June 03, 2014, 07:28:43 pm
content: I have a metal box( sizes 40 cm x 12cm x12cm) and inside there is overpressure ( from 6 to 8 atmospheres).Can anyone advise a way how to achieve inside temperature between 40 °C to 60 °C?What heating element and thermostat to use? Any idea?Thank you for help

author: staxquad
author_rank: Frequent Contributor
timestamp: June 03, 2014, 07:48:24 pm
content: Quote from: Jane on June 03, 2014, 07:28:43 pmresistance wire (Cupron, Kanthal, Nichrome) or any other heating element controlled by:US $5.24 delivered: -50-110°C DC12V Heat Cool Temp Thermostat Temperature Control Switchhttp://www.ebay.com/itm/400677190587?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649hysteresis is .5*C to 15*Cneeds a 12V power supply, I used this (cheap and efficient SMPS):http://www.ebay.com/itm/261340126682?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649I made 3 heating pads, 60cmx42cm, 60cmx40cm and 77cmx50cm and controlled the temp between 22*C and 24*C in the open when the ambient temperature was 13*C to 15*C. Heating pads each used ~180 to 300 ohms of insulated Cupron at 3.3/ft., so from 54ft to 90ft each. With differing lengths and the same controller, achieved the same result. Don't know how fast you need to heat the enclosed space, but that temp control switch will keep it within a few *C. When I was experimenting with wire length before I got the controllers, it did go in the 30s*C on the pad with an ambient temperature of ~16*C.

author: Jane
author_rank: Frequent Contributor
timestamp: June 04, 2014, 05:34:19 am
content: Thank you for the reply.Can you please let me know on which material you placed that insulated Cupron that you used for your heating pads?54ft to 90ft ~ 16,5m to 27.5m is quite long.Thanks

author: staxquad
author_rank: Frequent Contributor
timestamp: June 07, 2014, 05:16:27 am
content: Quote from: Jane on June 04, 2014, 05:34:19 amIf the surface you're intending on heating is 6 times less than my example (assuming you're heating the top or bottom plane), then the wires would need to be 6 times closer to each other using the same length and resistance or would need to have 6 times more resistance and be spaced the same with a length 6 times shorter.Only two wires and the tip of the probe would enter the pressurized box, holes sealed and everything would be hunky dory, temp controller turning power on and off on the resistance wire to keep temp constant.Wire something like this spaced a little closer together (would be 40% shorter because it's 4.76 ohms/ft rather than 3.3 ohms/ft):http://www.ebay.com/itm/Isotan-Konstantan-Cotton-Insulated-Resistance-Heating-Wire-0-20-mm-AWG-32-/190960459160?pt=UK_BOI_Electrical_Components_Supplies_ET&var=&hash=item2c76215d98what I used, 3.3 ohms/ft:Used duct tape to keep the wire in place and snaked the wire across the glass surface, then placed another piece of glass on top and sealed it with tape (could also be duct tape). The black and red wire was soldered to the resistance wire for connection to the temperature control.after use (container got rusty, the glass was in constant contact with water, but none entered, probably wouldn't matter anyway since the wire is enameled):My application was heating seedlings for gardening. Did a thread on it:https://www.eevblog.com/forum/chat/resistance-is-fertile/msg422176/#msg422176if what you put in the box can't sit on the heat source, then maybe the walls or the ceiling can hold the wirethe resulting wattage in my case might be higher or lower than for your case, but the temp controller does compensate, you just don't want the wire to get too hot, or not hot enough (heating too slow)