I've not clicked on the link yet but after replying to another post I have remembered why my Avon Flo control broke. The fuse somehow melted and never cut the power off resulting in the controller being damaged.
Hi Alan Below is what may have happened to your fuse.
A fuse is a Thermal device, So when a short or overload occurs, the amps being drawn spike and this increases the heat produced in the wiring and components. When this occurs, a fuse or circuit breaker reacts almost instantly to stop the flow of electricity in the circuit and thereby stopping heat production.
Avoid exceeding the fuse rating advised by the manufacturer. For a fuse to open in a fault condition almost instantly (a few hundred milliseconds ) it can require current of 2.2 to 3 times the rating of the fuse. For example a 7.5 amp fuses the actual current to open the fuse may be as high as 22.5 amps.
So in my Test One the current far exceeded this and the 7.5amp fuse with the fuse blowing instantly.
In very rare cases if current is only slightly above or close to the rating of the fuse for prolonged periods there is not sufficient heat or current to blow the fuse, in this case the heat can build up and cause the fuse to melt.
An example of what may cause this would be
* Damaged, rusted or worn connectors
* Corroded Fuse holder and or fuse
* Damaged cable
* Bare cables touching metal (Van panel or Trolley)
* Poor connection (example would be insulation not stripped back)
For example a 15 amp fuse will happily supply current up to 15 amps but will not blow. (to blow it could require current of up to 45 amps) The fuse will however gradually get hot over time in testing at Spring I have seen a 7.5 amp fuse heat to 62C and not blow
So in your case the fault is not sufficient to take the (possible) corroded fuse out instantly, but instead the fault slowly increases the heat. So what you would see is a similar effect to my Test Two result, In your cases this may have taken a few minutes. It would have been this that then took out the Switch
For this reason badly corroded fuses or connectors should be replaced. In some instances people can be tempted to fit a higher rated fuse than recommended. This is not a good idea
Without Properly rated fuses, this quick break in the circuit would not be possible, and damage to components and even FIRE could result.
If you are having a problem with fuses "blowing" please know that these devices are doing their job! It is important that you NOT replace a fuse or breaker with a higher-rated one. Check the circuit for shorts or overloads.
Next it may be the fuse was fitted close to the switch rather than close to the battery
Why then place the fuse close to the battery?
To reduce the risk of over heating in either the cable or device in the event of an electrical fault. The shorter distance current can travel between the battery and fuse means that the amount of cable that may get overheated is reduced to a minimum. For Example: It is possible the the insulation on the red (positive) cable can become chaffed allowing the core or poorly installed cable to come into contact with the chassis creating a fault condition . Without a fuse fitted close to the battery the wire will heat to red hot, burn off all the insulation and potentially cause a fire. Fitting a fuse close to the battery protects the cable run plus control and pump.
Hope this helps
