Flexwat and gfi outlet question

Ok, was trimming the bushes today and like I seem to do once every few years cut the electric cord with the trimmers. They were on a gfi outlet that tripped due to what I expect is a short when I cut the cord. For some reason that got me thinking. If I plugged my thermostat into a gfi outlet and the flexwat shorted would the gfi outlet pop? If so, it seems like an easy backup. But I don't know if it would. Anyone have any idea on this?

It could depending on what the failure is, a true short then yes, if the flexwatt begins to overheat, not necessarily...the purpose of a GFI breaker or outlet is really to avoid electrocution. Which is why building code requires outlets with this protection built in to be installed in areas that could be exposed to moisture. It compares the current going in vs going out and will trip if it notices an issue.

Now there is also a breaker called AFCI which is an Arc Fault Circuit Interrupter. This will trip if it senses an arc, so it is meant to halt an electrical fire.

So would those help if the heat tape shorted?

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Originally Posted by Bcycling

So would those help if the heat tape shorted?

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The Arc Fault breakers are now standard code of bedrooms and are being incorporated throughout the rest of the house. That being said I don't think they make an Arc Fault outlet, it is generally a circuit breaker that goes into your main breaker box. You can however wire your breaker box up with the Arc fault breaker then make that outlet a GFI outlet that way you get protection against both (which is what I did in my current house and plan to do in my new house after the move). So think of GFCI as "People Protection" and AFCI as fire protection. Here is a pretty helpful read (with more detail then you need):

http://www.afcisafety.org/qa.html

Actually, I think I have those on a few of my brakers. I think they are the ones with the green knob on them. Now I understand them, but would that trip the breaker in the case of a flexwat failure? As I am sure even if it was just over heating it would start to arc when it melted. What are your thoughts? How much do those breakers go for?

an AFCI breaker will have it labeled on in so you can see it from the front as you look in your main panel. Depending on the type of breaker you are looking to replace they vary in price, when I installed mine I think they were 50 bucks a piece. They are meant to sense and try to prevent an ARC so they are pretty sensitive. When talking about flexwatt it is hard to say. If you run it unregulated it can get hot enough to melt plastic, but the flexwatt is operating normally, so I don't see it tripping there, however if the flexwatt actually had an issue, where it shorted and started melting due to a true failure, the breaker should trip, if that makes sense. For example say I have my vacuum switch turned on and I go to plug it into an outlet that is tied to an AFCI and you get a small ARC from that then it will trip.

Just buy an inline fuse holder and size it appropriately. You'll avoid nuisance tripping and save money. What is your failsafe for stat failure?


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Originally Posted by Justinhicks

Just buy an inline fuse holder and size it appropriately. You'll avoid nuisance tripping and save money. What is your failsafe for stat failure?


Sent from my iPhone using Tapatalk

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the safety relay in the herpstats is my safety. That's why I am thinking outside the box to see where I can improve.

If you have a fuse or breaker, that will stop a true short.
If you have an arc fault, it stops arcs, flex watt really doesn't have much opportunity to do that, so it really doesn't help much in that aspect.
Gfcis compare incoming and outgoing current and trip if it is more than 5ma. Given flex watt only has one path, unless your rack is metal, there is no opportunity to have difference in current. So now it really won't help with flex watt.

I'm also not saying these devices are useless, just useless when it comes to heat tape.

With that said the common flex watt "short", isn't really a short, it's an component failure, so that's what I have in mind writing this. Resistors heat up more than they are supposed to, causes more heat, which causes more resistance, which causes more heat, ect. Til bad stuff happens. From what I've seen the failure is normally localized, so it doesn't effect the entire piece of tape. So if your probe is in one spot, doing its job while the heat tape is in runaway heating 3 feet away. So in that situation the thermostat doesn't help.

All I can suggest is take care of equipment, and keep it in good working order. Heat tape is an extremely simple thing, just foil tape and resistors that are laminated. Chances of it going bad are incredibly low. No moving parts to wear. Just when it does go bad, it can be catastrophic.

Physical damage can be an issue, pushing tubs over or against it. Material break down could be a problem, either from age or overheating. If you get new tape make sure it's not defective by giving it a run without putting animals at risk. I always wonder when people have issues, what actually happened to the tape to make it do that.

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Originally Posted by Bcycling

the safety relay in the herpstats is my safety. That's why I am thinking outside the box to see where I can improve.

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Honestly with herpstat safety relay and using heat tape the chance of failure causing something threatening to your animals is very low. But very low isn't non-existent.

While there's not much you can do about localized heat tape failure. The thermostat far more likely to malfunction before the heat tape fails, just because there are so many more components. The herpstats have a relay that is supposed to stop the unit from sticking on full blast, but let's assume for some reason the safety fails or you are using a different thermostat.

Besides a backup thermostat inline, an rheostat (aka light dimmer) is pretty inexpensive way to add some protection. You put it between the heat tape and thermostat, and turn the temp on the thermostat way up, then set the rheostat to keeps the temps about 5 degrees warmer than your target. Once you have that, turn your thermostat back down to target temps. Idea is in the event of failure, the heat tape shouldn't have the ability to dangerously heat the rack because the rheostat takes over. When you check your temp you will see things are running hot, gives you time to identify there's a problem and fix it. What I like about rheostats is they are a basic electrical component, so chances of failure are very low. There's a sticky mark built a pretty robust one, but most light dimmers will work https://ball-pythons.net/forums/show...light=Rheostat

How I like it, use the feature rich precise thermostat for primary control and keep the back up as simple as possible when it needs to work.

Oh and they do make arc fault recepticles, however where most fire starting arcs are from the stab in connections behind the recepticles. So the recepticle itself will not protect that, only thing plugged into it, which are normally not the issue.