It only took this electrician about two minutes to shake his head when he saw all the household-grade extension cords plugged into one another, getting power to heat lamps and electric heaters inside a barn used as a birthing area and as a nursery. He knows household cords are called household cords for a reason – they're designed for light duty inside the house. They're not designed to pull heavy loads, such as would be pulled by a heat lamp, even with a 125-watt bulb, in a dirty, dusty, less than ideal environment.
Related: How To Make Old Barns Useful Today
Will heat lamps turn on if the household cords are strung together and plugged in? Yes. Can you run several off of them? Most likely. Can you get by with it for years? Possibly. Will you get by with it forever? Maybe, maybe not. What are genetics in animals you've spent years producing worth if there is one time when the cords fail and a fire results?
The electrician says that heavy duty cords are better than household cords. Ideally, permanent wiring of a grade that meets code for the barn where it is installed running to outlets mounted where heat lamps can be plugged directly into them is a much better solution. Then properly working breakers add protection on the lines. The breakers in many barns are old – at least in older barns. Some are still fuse types. Even newer style breaker may have been in service for 30 to 40 years. Will they trip in time if a short occurs and deaden the circuit, before sparks and/or flame ignite insulation or straw and start a fire?
People fear heat lamps because of the fire hazard. The electrician who talked to us says it's not just the heat lamps that you have to worry about. It could well be the wiring and light-weight cords you're using to get power to the heat lamps that actually causes the problems.
If you've got extension cords like those pictured strung throughout the barn, maybe it's time to rethink your approach.