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I am doing a hobby project where I am using a thermostat which has a contact rating of 230 VAC, 5 A. Please see below thermostat details (RS link also contains full datasheet).

I want to drive a couple of fans based upon temperature setting on the thermostat for cooling purposes. The fan I want to use has a normal consumption of 0.6 A.

I have been advised by my teacher that usually fans have a starting in-rush current which is usually 5-6 times higher (for only during initial start-up period) than the normal current consumption of the fan. So when I am selecting a thermostat, I should take this into account. The fan datasheet doesn't give any inrush current. If I have two fans (each consuming 0.6 A at 230 VAC) connected in parallel, would the below thermostat contact of 5 A be sufficient?

Technical specifications of thermostat contact (for cooling):

  • Bi-metal controller as a temperature-sensitive element with thermal feedback
  • Contact population: Single-pole change-over contact as a quickbreak contact
  • Permissible contact load: Category 5 – 3 (heating) AC 10 (4) A (inductive load at cos φ = 0.6)/category 5- 4 (cooling): AC 5 (4) A (inductive load at cos φ = 0.6)/DC = max. 30 W
  • Switching difference: approx. 1 K ± 0.8 K

Link to full datasheet: https://uk.rs-online.com/web/p/thermostats/4570991

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  • \$\begingroup\$ Fan datasheet as well? \$\endgroup\$
    – Tim Williams
    Commented Jul 31, 2022 at 10:52

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This is an AC circuit, which is much easier on contacts than DC, and your thermostat is rated about 4 times more than fans, so should fine.

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  • \$\begingroup\$ many thanks michaeldthorpe. would you know what does this sentence mean (Switching difference: approx. 1 K ± 0.8 K) in the thermostat specification datasheet (link in my post above)? \$\endgroup\$
    – elecrobot
    Commented Jul 31, 2022 at 14:53
  • \$\begingroup\$ It probably means the hysteresis or temperature differential between the ON state and OFF state. The value seems to be in degrees Kelvin (K), which is equivalent to Celsius shifted for absolute zero. \$\endgroup\$
    – PStechPaul
    Commented Jul 31, 2022 at 20:45
  • \$\begingroup\$ Cool thanks. I thought 1K was 1000 but didn’t notice its capital K which is used for Kelvin. It makes sense now. \$\endgroup\$
    – elecrobot
    Commented Jul 31, 2022 at 21:23

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