# Relay gets hot: probably normal?

#### likes_shiny_things

Joined Sep 11, 2011
27
I have a Magnecraft W250ACPX_9 octal relay - 120VAC, rated continuous duty. It's the style that has the clear plastic dust cover.

The only part that gets hot is the screw head that connects to the coil and is exposed to the exterior of the dust cover.

I've let it remain engaged for at least 24 hours at a time and the screw head gets hot enough so I can hold my finger on it for only a few seconds. The plastic dust cover is barely warm, even in the immediate area around the screw head.

I'm assuming this is normal but I wanted to check with those who have more experience with this type of relay.

Thank you!

#### mik3

Joined Feb 4, 2008
4,843
If you can keep your finger on the screw for a few seconds it is fine!

#### crutschow

Joined Mar 14, 2008
30,441
Due to cost considerations, many devices are designed not for maximum efficiency, but just enough efficiency so their temperature rise does not cause the part to fail. Thus it is normal for the relay coil to become quite warm, but that temperature is still well below it's failure point, which is likely well above 100°C.

#### thatoneguy

Joined Feb 19, 2009
6,359
When it gets to the point that when you touch it and immediately pull your hand back by reflex, it is running too hot. If you end up with a screw shaped blister, it is running way too hot.

You can get low accuracy (+/- 5 degrees) for cheap, handy to have around when looking for hotspots in circuits or devices. Cost is around $15 to$75, the higher end ones have a laser to point at center of the exact area the temp is being measured at.