Gas Pipes.

You need hundreds of amps to warm up a 15mm or 22mm dia pipe to any thing like a dangerous temperature, the resistance is so low.


The wall thickness is 0.7mm on  a 15mm pipe, and more like 0.9mm on a 22 .

Pi* diameter* thickness = 47mm*0.7=  32mm2 for the 15mm pipe

= 69* 0.9 = 62mm2 for the 22mm pipe.


If you compare these areas with the rating of similar cross-sections of PVC insulated cable you'd be looking at 170A and 250a for method C , but then the pipe is better cooled than a solid cored wire as it has a far larger exposed surface, and in any case that current rating only gets you up to 70C - solder melts at about 200C, so you'd need to increase the current by a large multiple to get hot enough to unsolder a joint ! Though water pipe is better cooled against hot spots.


Generally, the only problems arise really when screwed joints are being un-done for maintenance, or in very odd cases where perhaps there is tape in a join, or an earth clamp is loose so that all the current is tunnelled into a much smaller area and it sizzles and burns through,and that is not common.

Diverted neutral current is as much a risk as the CPC if not more so, but at least if there is bonding where the pipes come in, we are not passing current via internal piping of gas cookers and boilers and their CPC of unknown cross-section.

You need hundreds of amps to warm up a 15mm or 22mm dia pipe to any thing like a dangerous temperature, the resistance is so low.


The wall thickness is 0.7mm on  a 15mm pipe, and more like 0.9mm on a 22 .

Pi* diameter* thickness = 47mm*0.7=  32mm2 for the 15mm pipe

= 69* 0.9 = 62mm2 for the 22mm pipe.


If you compare these areas with the rating of similar cross-sections of PVC insulated cable you'd be looking at 170A and 250a for method C , but then the pipe is better cooled than a solid cored wire as it has a far larger exposed surface, and in any case that current rating only gets you up to 70C - solder melts at about 200C, so you'd need to increase the current by a large multiple to get hot enough to unsolder a joint ! Though water pipe is better cooled against hot spots.


Generally, the only problems arise really when screwed joints are being un-done for maintenance, or in very odd cases where perhaps there is tape in a join, or an earth clamp is loose so that all the current is tunnelled into a much smaller area and it sizzles and burns through,and that is not common.

Diverted neutral current is as much a risk as the CPC if not more so, but at least if there is bonding where the pipes come in, we are not passing current via internal piping of gas cookers and boilers and their CPC of unknown cross-section.