240 connector failure

[jcaudill]

Hello,

I have a simple control panel built for my hot water heater that uses a 240v auber PID controller and a 5500w stainless element. The circuit is 220 30-volt. It use properly rather cable between the receptacle and the panel, and panel to element. The main cable and element cable connect with Leviton locking connectors.

I've been using this setup for at least 10 brews now. So Saturday night I set the controller to start heating water. When I came down Sunday morning to check on it everything was fine but I noticed when I cracked my garage door I got a slight whiff of electrical smell. I didn't think much of it thinking maybe it was something outdoors. Well a couple hours later when I was getting ready to mash in I noticed I could smell it in just a certain area of my garage. Perplexed I hunted and hunted. The smell would come and go so it was very mysterious. When when I went to refill my hot water tank for the second brew the smell got much stronger and once I started hunting again it was obvious it was coming from that direction and I noticed immediately dripping plastic and smoke from the control panel.

I cut the circuit immediately. Upon inspection it looks like one or both of the Leviton connectors failed. The plastic around one of the phase wires was badly melted along with the wire leading into the connector from the main feed terminal block.

I eliminated the connectors, wirenutted the cables and proceeded along with a watchful eye. That went perfectly fine.

So my question is: what safety device can I put in place in my control panel that will cut the power in the event something like this happens again? A fuse seems logical, however, if it wasn't drawing enough power to trip the breaker, unless I put a fuse that will blow earlier that doesn't seem like it would have solved this particular situation.

I'm pretty much open to everything because this is my worst nightmare and the only 240v brewing related appliance I have,

Thanks in advance.

 

[itsnotrequired]

nine times out of ten, these faults are caused by loose wiring. the current draw can be such that the breaker can't 'detect' it until damage has occurred. only real solution is periodically inspecting your wiring for loose connections. different connectors have different torque requirements for the screws, you could get a torque screwdriver to ensure everything is tightened properly.

 

[jcaudill]

I definitely double-checked my wiring inside the remaining connectors. It seemed like it was fine in the previous ones as well but they were pretty damaged so it's hard to be 100% certain.

I'd certainly like to put any safety mechanism in place, if possible, before putting this back into service. I'm home when this runs but the last thing I need to do is burn down my house and my neighbors. I got a nest to put in there in hopes it would have helped detect something like this.

 

[itsnotrequired]

unfortunately, there just isn't much that can be done to protect against loose connections. an afci circuit breaker might offer some additional protections if there was an arcing connection but that's about it. unless you want to investigate an exotic temperature sensor that shuts the panel down or thermal imaging or something like that.

 

[jcaudill]

Bugger - well thanks for the reply, however! There is one option I need to look into. Now that I've got the NEST Protect in the garage, provided it would have detected that in the first place, I might be able to do something with IFTTT if I can find a 240v capable receiver.

 

[dyqik]

I don't think there's any automated way you could detect this kind of fault, which basically manifests itself as extra resistance on the circuit, but not enough to kill all your power at the element. High resistance that causes heating is indistinguishable for something in the breaker panel from just using a lower power rated element, or a lower power appliance.

However, if you were particularly worried, you might be able to detect it is by monitoring the voltage in your control panel (with a combined current/voltage/power meter), if the added resistance is high enough.

If the voltage starts dropping (more than usual?) as you apply more power to the element, so that you have a low voltage for the current compared to normal, then you have some extra resistance on the supply side of the panel, possibly due to a failing connection. This would be clearest if you used another meter to measure the supply voltage on another circuit at the same time to eliminate the possibility of a supply voltage drop to the whole house.

If, on the other hand, the element is drawing less current than usual for the voltage when at full power, you have extra resistance on the element side of the control panel, again, possibly due to a loose connection.

But all of this will require you to a) fit a (fairly cheap, but accurate) voltage/current/power meter, and b) keep accurate notes of the nominal currents and voltages in your system, and c) compare the values while brewing. I guess this _could_ be automated in some advanced automatic brewery controller. And you might run into a problem with the element resistance changing with temperature.

 

[jcaudill]

I don't think there's any automated way you could detect this kind of fault, which basically manifests itself as extra resistance on the circuit, but not enough to kill all your power at the element. High resistance that causes heating is indistinguishable for something in the breaker panel from just using a lower power rated element, or a lower power appliance.

However, if you were particularly worried, you might be able to detect it is by monitoring the voltage in your control panel (with a combined current/voltage/power meter), if the added resistance is high enough.

If the voltage starts dropping (more than usual?) as you apply more power to the element, so that you have a low voltage for the current compared to normal, then you have some extra resistance on the supply side of the panel, possibly due to a failing connection. This would be clearest if you used another meter to measure the supply voltage on another circuit at the same time to eliminate the possibility of a supply voltage drop to the whole house.

If, on the other hand, the element is drawing less current than usual for the voltage when at full power, you have extra resistance on the element side of the control panel, again, possibly due to a loose connection.

But all of this will require you to a) fit a (fairly cheap, but accurate) voltage/current/power meter, and b) keep accurate notes of the nominal currents and voltages in your system, and c) compare the values while brewing. I guess this _could_ be automated in some advanced automatic brewery controller.

Very interesting, and thank you!

Luckily, this is just a standalone hot water heater that I use to pre-heat water for brewing and then it's shutoff. My concern is that I usually fill it the night before the brew, go to sleep then wake up with water ready to go. So I'm around, but I'm asleep and I'm not going to detect smoke until it's too late. I'm running an exhaust fan too so that smell and smoke will likely get sucked out before it has a chance to accumulate unless it's a real fire by then.

I'll do a little poking based on your feedback!