Posted By Nigel Hammond
Our head office is an open plan building with a rather ineffective air conditioning system.

When the weather was cold some of our managers bought small fan heaters. I do not like this because of the fire risk. Without ripping out the air conditioning system and starting again, is there a less risky alternative to fan heaters?

Posted By Jane Blunt
Dear Nigel,

You will need to keep an eye on the loading on your circuits. Outlets are routinely 13 Amp, which means that each can supply around 3 kilowatts (at 240 V). Any more and you are overloading the system.

If you have cartridge fuses, and you get to the point of blowing them you have should review your loading urgently. Cartridge fuses can normally take up to around 2 to 3 times the rated current (that is, a cartridge fuse of 13A rating will often not fail until it is carrying over 30A). This is a serious fire risk, because by then some of the cable is probably getting quite hot, or can do so if it is improperly laid out.

We routinely demonstrate to new students how easy it is to overload a cable to the point where it sets fire to something, by running several heaters from a single 4-way extension lead using a reeled cable (such as you can buy in a hardware store for reeling out cable to your electric lawnmower).

Before you all go and copy this experiment, we do it in an extracted booth, so that people are not poisoned by the burning cable, and we have practised it a lot, so we know how to do it safely.

Jane

Posted By Ken Taylor
After radiators, convectors are probably the most practical. Fan heaters are expensive, noisy, smelly (when dusty) and easy to tread on or trip over. Presumably you get all 'introduced' additional heaters of this type PAT tested before use? Don't even consider portable LPG or paraffin!