Electronic – How are electric under blankets fail safe


Electric under blankets are mains powered and yet you lie on them. 240V in the UK. They appear to effectively be a single resistive heating element. Clearly they're not earthed as that would be difficult, and I can't see how double insulation could apply.

It seems to me that if the element breaks, it could poke through the material and cause a shock hazard to the sleeper. And what if my old dog wees on it, or bites it? If they were a danger, they wouldn't be sold. So how are they made fail safe?

Best Answer

Since 2001, all electric blankets now have a safety mechanism that will kill power if it detects that the element is broken. Many are now operated using 12 or 24VDC as well, so there is less danger of shock if something goes awry; the control unit is also a DC power supply.

If your dog wees on it and the element is not already damaged, nothing will happen, the heating element wire is insulated. But you can't really wash it, so don't let that dog on the bed!