Is a heater catching fire under water dangerous to fish???

[crnozemski]

Your GFCI operated as designed at least in respect of an earth fault. GFCIs watch out for only electricity leaking out of what should be a closed circuit. If it is given the chance, electricity will always flow out of a closed circuit and off to earth. It appears from your photographs that the heater itself is not earthed (they don't tend to be), as it has only two conductors not three, and nothing else in your tank was. As such, when the heater failed and then melted there was no path to earth for the electricity to flow to. Without a path to earth, the GFCI cannot detect an imbalance in the current between the line (live) and neutral conductors so it would not trip. In other words, in order to trip a GFCI needs to be able to 'see' electricity 'escaping' out of a circuit but there was in your case no escape - it was 'stuck' inside the tank. Had you for example been wearing no shoes and been standing on the ground with wet feet, then placed your hand in the saltwater tank with all of its salty free ions, you would likely have provided the electricity with a near perfect path to earth and in theory either i) the GFCI should have tripped within a few milliseconds or ii) you would have experienced injury or death.

None of that answers why your breaker did not trip for either i) short circuit or ii) overload. I suspect that that is a matter of timing; you mentioned you were there when it happened. Had it been unattended, at some point we hope the breaker would have tripped for a short fault. Any competent electrician can test your breakers for you, and your GFCIs. They will also be able to suggest an appropriately rated GFCI if they are not happy with yours - I suggest 5 mA, but you may run into nuisance tripping and need a higher rating (even high quality devices tend to leak a tiny amount to earth and a lot of these adds up). The same point applies for the rating of your breaker - to trip a 15A breaker would require a heck of a lot of fault current (they actually trip somewhat higher than their rating). Again, this is easy stuff for a competent electrician.

Going forward I would suggest you get a Schego titanium heater because i) they are far more reliable than other heaters ii) they are earthed. However, for a titanium heater you'll need a temperature controller or an aquarium controller.

As to a ground probe, that's a hotly debated topic but yes in this case had you had one then your GFCI would almost certainly have tripped immediately and prevented the issue you've had to deal with. This is because a ground probe is an 'open door' - a permanent route to earth that is available to electricity to flow down, if there is a fault. If it's of any help at all, despite the endless debate I am of the view that your tank should be earthed and mine is so earthed.

Are you guys talking about ground probes for the actual aquarium itself or the whole house?

Also if you have an earthed titanium heater and some other piece of equipment creates fault current within the aquarium will your residual current device still trip? (Casing of heater being grounded) In assuming GFCI is same as an RCD...im in aus

 

[Matt Peacock]

Are you guys talking about ground probes for the actual aquarium itself or the whole house?

Also if you have an earthed titanium heater and some other piece of equipment creates fault current within the aquarium will your residual current device still trip? (Casing of heater being grounded) In assuming GFCI is same as an RCD...im in aus

Talking about a ground probe for the aquarium itself. So that would link your aquarium system to the ground of your house (be that in a rod outside, or via the electricity supply).

Yes exactly right, as long as it has no faults the heater would itself act as a grounding probe does (assuming that the extension lead or temperature controller you connect it to is also grounded).

GFCI and RCD are different names for the same device.

 

[crnozemski]

Talking about a ground probe for the aquarium itself. So that would link your aquarium system to the ground of your house (be that in a rod outside, or via the electricity supply).

Yes exactly right, as long as it has no faults the heater would itself act as a grounding probe does (assuming that the extension lead or temperature controller you connect it to is also grounded).

GFCI and RCD are different names for the same device.

Thanks for clarifying!

 

[RobW]

Yea I do not have one of those. I'll contact an electrician asap.

Problem with switching from a standard breaker to a "dual function AFCI/GFCI breaker is that there may be 2 individual circuits sharing a neutral conductor. In that case the electrician would either A. have to run a dedicated line for you with that type of breaker or B. Use a 2 pole AFCI/GFCI breaker to also pick up the other circuit that is sharing the neutral. The breaker won't even reset if there is another circuit sharing the common neutral. Could rack up a bill real quick sorting that out. Depending what you have for circuitry... a device change may have to suffice.