This is an immersion-heater-timer burning out problem.
I have a photo of the damage but have been unable to find a way to include it in this document.
I have installed two 13A Masterplug Mechanical Immersion Heater Timers (one timer on each of two different occasions) in the power supply cable between the on/off switch (about 40cm away) and the water tank (about 50cm away). The immersion heater thermostat is set to about 1/3rd up the temperature range (40-45 degrees?).
The cables are all twin plus earth (T+E) single strand of considerable thickness.
The first timer burned out after a few days and was replaced with a second one. This second one has gone all winter without incidents but has now fallen foul to the same problem.
The visible evidence shows that overheating took place at the connection of the Neutral supply to the timer. The heat was sufficient to melt the solid plastic of the timer. The effect on the cable itself was less obvious but there are signs of overheating to about the first 1cm of the neutral conductor. This seems to be caused by heat transmission from the timer connector where the main source of heat was generated.
All overheating seems to have been confined to the Neutral input connector area of the timer. Although arcing could possibly have occurred, because of the first timer problem I am practically certain that all the cables on the second timer were very tightly connected.
I have no idea if the timing function has been affected.
I am mystified by this double occurrence and would appreciate any help or advice that anybody can offer as to
a) the cause
and
b) how to avoid it recurring.
Many thanks.
I have a photo of the damage but have been unable to find a way to include it in this document.
I have installed two 13A Masterplug Mechanical Immersion Heater Timers (one timer on each of two different occasions) in the power supply cable between the on/off switch (about 40cm away) and the water tank (about 50cm away). The immersion heater thermostat is set to about 1/3rd up the temperature range (40-45 degrees?).
The cables are all twin plus earth (T+E) single strand of considerable thickness.
The first timer burned out after a few days and was replaced with a second one. This second one has gone all winter without incidents but has now fallen foul to the same problem.
The visible evidence shows that overheating took place at the connection of the Neutral supply to the timer. The heat was sufficient to melt the solid plastic of the timer. The effect on the cable itself was less obvious but there are signs of overheating to about the first 1cm of the neutral conductor. This seems to be caused by heat transmission from the timer connector where the main source of heat was generated.
All overheating seems to have been confined to the Neutral input connector area of the timer. Although arcing could possibly have occurred, because of the first timer problem I am practically certain that all the cables on the second timer were very tightly connected.
I have no idea if the timing function has been affected.
I am mystified by this double occurrence and would appreciate any help or advice that anybody can offer as to
a) the cause
and
b) how to avoid it recurring.
Many thanks.