Electrics
Interesting Articles Regarding Electrical Installations
Below is a very interesting guide to cable sizes suitable for model boat use kindly submitted by Alan Oldfield
What Wires For My Boat by Alan Oldfield 23 April 2022
In general the types of suitable wires for model boats will be classified as hook-up or equipment wires, single core, single sheathed, multi stranded. The current carrying capacity is dependant on the operating temperature allowed for the type of insulation, the ambient air temperature and how the wires are installed. Several wires bunched together will carry less current than a single wire due to reduced air circulation. Maximum operating temperatures for insulation types listed below would not normally be used. Some plastics start to get soft at 100 deg c and at 50 deg c is almost untouchable! Consider this when connecting to terminal blocks and other equipment etc. Short term overloads are permitted. e.g. during fuse blowing time or during rapid acceleration of drive motor, (within the limits of the ESC) (See following guide to dc motors and control)
A guide to equipment wire types and insulation properties.
1) PVC insulated to DEF61-12 part 6, also complying with BS4808 is intended for military defence use at an ambient air temperature of 70 deg c and a 15 deg c rise due to current flow. Maximum operating temperature is 85 deg Commercial ratings are suggested for use at 25 deg c ambient. The upper temperature is the temperature at conductor due to a combination of ambient and temperature rise due to current flow. Size range 7/0.2 (0.22 sq mm.) to 32/0.2 (1 sq mm.) De-rating factors for multiple wires, bunched are not available.
2) PVC insulated Tri Rated (UL758, CSA c22.2, BS6231) are intended for commercial use with an ambient air temperature of 55 deg c and a rise of 35 deg c. Maximum operating temperature is 90 deg c. Some manufactures table ratings are for 35 deg c ambient and 35 deg c temperature rise due to current flow. Size range 16/0.2 (0.5 sq mm) to 80/0.4 (10 sq mm) and beyond. De-rating factors are applied for multiple wires, bunched
3) Silicone Rubber, usually extra flexible and with a 150 to 200 deg c maximum operating temperature. Not much information is found for this type of wire. Ratings for Tri rated PVC wire should be applied.
After looking through numerous wire rating tables and model boat forums, there are many answers to the question of what wires for my boat.
Example 1 - 7/0.2 (0.22 sq mm) single core, single insulated.
Hobbies no insulation type no de-rating factors no temperature specs. 2A
Component Shop Silicone no de-rating factors limited temperature specs 3.5A
Cornwall Model Boats Silicone no de-rating factors no temperature spec no rating
Rapid Electronics/Ebay PVC to DEF61-12 no de-rating factors limited temperature specs 1.4A
Farnell Electronics PVC to DEF61-12 no de-rating factors with temperature specs 2A
Example 2 - 16/0.2 (0.5 sq mm) single core, single insulated.
Rapid Electronics/Ebay PVC to DEF61-12 no de-rating factors limited temperature specs 3A
Hobbytronics PVC to DEF61-12 no de-rating factors no temperature specs 4A
Rapid Electronics PVC Tri Rated no de-rating factors limited temperature specs 11A
Farnell Electronics PVC Tri Rated with de-rating factors with temperature specs 11A and less
Sifting through this confusion, the following is a suggested guide to current ratings (amps)
For 2 wires, bunched or twisted, ambient 25 deg c, 35 deg c rise due to current flow. 60 deg c max
Size Approx AWG DEF61-12 Tri rated or Silicone
7/0.2 (0.22 sq mm) 24 2 3
16/0.2 (0.5 sq mm) 20 4 8
24/0.2 (0.75 sq mm) 18 6 11
(0.8 sq mm) 18 - 12
32/0.2 (1.0 sq mm) 17 8 13
(1.3 sq mm) 16 - 15
30/0.25 (1.5 sq mm) 16 - 16
(2.1 sq mm) 14 - 20
50/0.25 (2.5 sq mm) 12 - 24
56/0.25 (4.0 sq mm) 11 - 32
80/0.3 (6 sq mm) 10 - 42
80/0.4 (10.0 sq mm) 8 - 60
Ratings are rounded down to the nearest integer
To use at reduced wire temperature or more than two wires bunched or twisted – use next size up
If in doubt - use the next size up
References – Doncaster Cables for Tri rated, Farnell Multicomp Pro & Elland Cables for Tri rated and DEF61-12 part 6,
What Wires For My Boat by Alan Oldfield 23 April 2022
In general the types of suitable wires for model boats will be classified as hook-up or equipment wires, single core, single sheathed, multi stranded. The current carrying capacity is dependant on the operating temperature allowed for the type of insulation, the ambient air temperature and how the wires are installed. Several wires bunched together will carry less current than a single wire due to reduced air circulation. Maximum operating temperatures for insulation types listed below would not normally be used. Some plastics start to get soft at 100 deg c and at 50 deg c is almost untouchable! Consider this when connecting to terminal blocks and other equipment etc. Short term overloads are permitted. e.g. during fuse blowing time or during rapid acceleration of drive motor, (within the limits of the ESC) (See following guide to dc motors and control)
A guide to equipment wire types and insulation properties.
1) PVC insulated to DEF61-12 part 6, also complying with BS4808 is intended for military defence use at an ambient air temperature of 70 deg c and a 15 deg c rise due to current flow. Maximum operating temperature is 85 deg Commercial ratings are suggested for use at 25 deg c ambient. The upper temperature is the temperature at conductor due to a combination of ambient and temperature rise due to current flow. Size range 7/0.2 (0.22 sq mm.) to 32/0.2 (1 sq mm.) De-rating factors for multiple wires, bunched are not available.
2) PVC insulated Tri Rated (UL758, CSA c22.2, BS6231) are intended for commercial use with an ambient air temperature of 55 deg c and a rise of 35 deg c. Maximum operating temperature is 90 deg c. Some manufactures table ratings are for 35 deg c ambient and 35 deg c temperature rise due to current flow. Size range 16/0.2 (0.5 sq mm) to 80/0.4 (10 sq mm) and beyond. De-rating factors are applied for multiple wires, bunched
3) Silicone Rubber, usually extra flexible and with a 150 to 200 deg c maximum operating temperature. Not much information is found for this type of wire. Ratings for Tri rated PVC wire should be applied.
After looking through numerous wire rating tables and model boat forums, there are many answers to the question of what wires for my boat.
Example 1 - 7/0.2 (0.22 sq mm) single core, single insulated.
Hobbies no insulation type no de-rating factors no temperature specs. 2A
Component Shop Silicone no de-rating factors limited temperature specs 3.5A
Cornwall Model Boats Silicone no de-rating factors no temperature spec no rating
Rapid Electronics/Ebay PVC to DEF61-12 no de-rating factors limited temperature specs 1.4A
Farnell Electronics PVC to DEF61-12 no de-rating factors with temperature specs 2A
Example 2 - 16/0.2 (0.5 sq mm) single core, single insulated.
Rapid Electronics/Ebay PVC to DEF61-12 no de-rating factors limited temperature specs 3A
Hobbytronics PVC to DEF61-12 no de-rating factors no temperature specs 4A
Rapid Electronics PVC Tri Rated no de-rating factors limited temperature specs 11A
Farnell Electronics PVC Tri Rated with de-rating factors with temperature specs 11A and less
Sifting through this confusion, the following is a suggested guide to current ratings (amps)
For 2 wires, bunched or twisted, ambient 25 deg c, 35 deg c rise due to current flow. 60 deg c max
Size Approx AWG DEF61-12 Tri rated or Silicone
7/0.2 (0.22 sq mm) 24 2 3
16/0.2 (0.5 sq mm) 20 4 8
24/0.2 (0.75 sq mm) 18 6 11
(0.8 sq mm) 18 - 12
32/0.2 (1.0 sq mm) 17 8 13
(1.3 sq mm) 16 - 15
30/0.25 (1.5 sq mm) 16 - 16
(2.1 sq mm) 14 - 20
50/0.25 (2.5 sq mm) 12 - 24
56/0.25 (4.0 sq mm) 11 - 32
80/0.3 (6 sq mm) 10 - 42
80/0.4 (10.0 sq mm) 8 - 60
Ratings are rounded down to the nearest integer
To use at reduced wire temperature or more than two wires bunched or twisted – use next size up
If in doubt - use the next size up
References – Doncaster Cables for Tri rated, Farnell Multicomp Pro & Elland Cables for Tri rated and DEF61-12 part 6,
