Nichrome Wire
Contents
Intro
Nichrome wire is used to make electric heaters. It heats up to a high temperature while retaining its strength. It is resistive, so it is easy to heat by sending electric current through the wire.
Nichrome wire is live with electric potential. It is useful to insulate it to use it reliably without shorting out on itself or on other metal parts. To this end, nichrome wire is coated with teflon.
Design Rationale
- Select for power.
- Minimize length to simplify the amount of wiring
- Check that it doesn't get too hot for a given length with Nichrome Wire Calculator
- Make wire thin to get lower length for a given power
- Don't make it too thin so it doesn't get too hot.
Sourcing
Plain
Coated
- Teflon coated nichrome wire on Alibaba 200C - [3] - 36 cents/meter
- Pelican Wire makes coated resistance heating wire - [4]
- Fiberglass coated wire, 5' Ultimachine, 8 Ohm/foot ga 31, 290C max - [5]
- Take thin fiberglass sleeving and place nichrome inside,
- Fiberglass insulated - ebay - 200C limit - 17.5 Ohm/foot, $14 for 50 feet - [6];
- 4 Ohm/foot $12 for 50 feet - [7] Appears to be good only to 120C - [8] - not great.
- Fiberglass and other Sleeving for wire - [9]
- Nichrome wire - $18 for 445 feet, about gauge 30 - [10]. AKA Chromel C or Nichrome 60.
Calculations
- See Nichrome Wire Calculator
- For Nichrome 60 at 500W - 20-24 gauge is recommended [11]. Ga 24 is 0.02" [12]. 1.67 ohms per foot for ga 24 - [13]. Would need 18 feet of nichrome for a 500W heater.
- For 400W, we can use 26 gauge.
- To get the right balance of heater wire - I would start with fiberglass insulated wire so burn-through is not likely as with silicone rubber. We rely on the physical contact and not adhesive, since we would want to use insulation on the heatbed.
DIY
- Coat it with chimney cement - [14]
- Use ceramic beads - [15]. Recyclebot work. Claims temperature can be higher than pre-coated wire. Suggests also https://pelicanwire.com/
Resistance Data
Links
- 120V Heatbed
- Grades of Nichrome Wire - 60 and 80 - [16]
