Here we go I have 4 transformers (230V to 12V) and 4 radio receivers. I have one transformer connected to one receiver. Similarly all transformers are connected in the same way. Now, I used a connection box (normal heavy duty ones bought at hardware shop-i think its made of some kinda fibre) to house 2 transformers and 2 receivers. This scenario is happening in my roof. I went to open one of the box the other and the transformer was hot. It wasn't hot to the point of not being able to hold it. But hot enough for me to hold it for for a while before letting go. So the basics here is that one transformer is only powering one receiver which is OK for the load. But I am a bit worried as to whether this can start a fire in the roof. Any advice please? Can this scenario lead to a fire? (Even though there is no overloading)
Not knowing the rating of the transformer and the actual load on them, all I can do is give you generic answers: a) Transformers have a rating which is the continuous amount of load it can carry without overheating. b) Typically, a transformer can handle momentary loads at 125% of rating - but that is neither a good idea nor always accurate. And momentary means just that - a motor starting, for instance. With that in mind, if a transformer gets warm to the touch, it is probably working within its range. If it is hot to the touch, it is being overloaded. The generic rule-of-thumb is that if you can touch the transformer indefinitely, it is OK. If you have to remove your finger/hand in less than 3 seconds, you are far into the danger zone. If you have to let go after any period at all, you are in the danger zone. Check the rating of the transformer and the actual load of the receivers. Now, when transformers fail, they typically do so in a fairly spectacular manner. The coils get very hot, the insulation (varnish in most cases) fails, and they begin to short inside - getting hotter as they do so until they eventually either blow a fuse, open, or melt down. It is the last that absolutely *can* start a fire. But before that happens, they often toast whatever is connected to them as well.
It's possible but very unlikely. Many transformers have a heat-operated fuse connected in series so that it breaks before the transformer coils get dangerously hot. It will be hotter inside because the heat can't escape easily, so if the transformer fails the wire will melt inside it, not on the outside. If you are worried about it then you could either check if your transformers have such a fuse, or if they don't, you could fit one yourself. You could also fit the transformers into a big metal box with air vents and a fan to help keep things cool. It's normal for a transformer to get warm, just feel any mains adapter in use. The main component is a transformer. Electrical fires are caused mostly by bad connections sparking, or bad practice which allows a cable to get red-hot from an overload, something which will not happen in a standard installation, because fuses and breakers are installed to prevent it. There is a huge difference between the temperature your hand finds uncomfortable, and the temperature of melting copper which could cause a fire.
Pete's answer is a winner. The only thing I'd add to it is that all electronics that generate heat must be vented. You didn't say you had any venting. Sometimes that venting can be convective current venting (hot air rises, cool air enters from below) OR can be a cooling fan. Like Pete said, without specs and loads we can't tell for sure if there's a danger. And until you KNOW there is no danger, assume there is. Hope this helped. '')
