# Zoo Med Undertank Heater exploded and caused a fire!



## christinas (Jun 24, 2017)

Hello,

As the title says, the undertank heater made by Zoo Med Laboratories that I had been using for about 8 months to heat up my Dumpy Frog tank has exploded and caused a small fire. Everyone is fine (aside from the bookshelf that supported the tank).  

But now I'm wondering the following:

1) Did I do something wrong when using the UH? I propped the tank up on the rubber feet that came with the tank, as the instructions said, and it was working fine for about 8 months until the big bang today. You can see the hole in the heater itself. 

2) How do I heat up my froggie's tank now? I'm afraid of using another UH. I have another one, also by Zoo Med, under my hermit crab tank, so there's that to worry about ... 

Thanks!


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## The Snark (Jun 24, 2017)

Can you give me the exact info? The product name and identifying numbers if any, power source, extension cords used, wattage of the device. Additionally was the unit compromised or modified in any way shape or form? Subjected to extreme pressure or temperature? 
(I enjoy sleuthing these occurrences.)


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## Anoplogaster (Jun 24, 2017)

A moderate version of this happened to me recently. The heat mat under my roach colony overheated and burned itself out. Luckily, the internal damage caused the unit to shut off before too much burning could occur. 

Is there a chance that yours got any water around it? Since you mention it's for a frog enclosure. 

I always prefer to heat from above using a ceramic heater attached to a homemade lid. I have an argus monitor that needs a basking temp of around 120 degrees F, and have never had burning issues with lights and ceramic heaters.


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## christinas (Jun 24, 2017)

@The Snark The heating mat was as follows: REPTI Therm UTH, Item # RH-4, 120 VAC, 60 Hz, 8W
I was using a simple extension cord, 800V from Amazon.
The tank isn't entirely new but wasn't compromised in any way, and it still isn't. No changes in temperature or pressure; however, since it's for a White Tree Frog I do routinely put water inside the tank and did so today. It is entirely possible some of it got on the outside of the tank and/or dripped down onto the bookshelf, but the heating pad was smaller than the bottom of the tank and was glued in the middle, not touching the sides. It seems unlikely to me that water would have gotten that far under the tank, not just at the sides, but it is possible I suppose. I was just wondering if there was a possibility of a "spontaneous combustion" for UH's ... but I'd prefer if it was caused by something I did since then I can hopefully prevent it from happening again.


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## Introvertebrate (Jun 25, 2017)

christinas said:


> @The Snark The heating mat was as follows: REPTI Therm UTH, Item # RH-4, 120 VAC, 60 Hz, 8W
> I was using a simple extension cord, 800V from Amazon.
> The tank isn't entirely new but wasn't compromised in any way, and it still isn't. No changes in temperature or pressure; however, since it's for a White Tree Frog I do routinely put water inside the tank and did so today. It is entirely possible some of it got on the outside of the tank and/or dripped down onto the bookshelf, but the heating pad was smaller than the bottom of the tank and was glued in the middle, not touching the sides. It seems unlikely to me that water would have gotten that far under the tank, not just at the sides, but it is possible I suppose. I was just wondering if there was a possibility of a "spontaneous combustion" for UH's ... but I'd prefer if it was caused by something I did since then I can hopefully prevent it from happening again.


I believe he's asking you if the heater was compromised in any way, not the tank.


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## The Snark (Jun 25, 2017)

For what it is worth, it has a one year warranty. They expressly state it is not to be used in any conditions where it can contact moisture.

What I don't understand is why it didn't come with a fuse. A 1/10th amp fuse would have kept it from going bang. (120v, 8 watts, 1800 ohms, .066 amps.)

https://zoomed.com/wp-content/uploads/RH-456-Mini-UTH-instr17.pdf


BTW, a good rule to follow with these putz suicidal appliances. Divide the watts by the voltage: 8 / 120 =.06667... then round up to tenths or whole numbers. = .1 amp fuse. Fuse blows, replace the fuse. Fuse blows again, replace the appliance.

Reactions: Informative 1


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## christinas (Jun 25, 2017)

The Snark said:


> For what it is worth, it has a one year warranty. They expressly state it is not to be used in any conditions where it can contact moisture.
> 
> What I don't understand is why it didn't come with a fuse. A 1/10th amp fuse would have kept it from going bang. (120v, 8 watts, 1800 ohms, .066 amps.)
> 
> https://zoomed.com/wp-content/uploads/RH-456-Mini-UTH-instr17.pdf


Is it normally sold with a fuse? Can I buy a fuse separately?


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## Anoplogaster (Jun 25, 2017)

christinas said:


> Is it normally sold with a fuse? Can I buy a fuse separately?


They don't come with fuses. I've never seen any reptile appliances sold off the shelf with fuses included, unless it's internal (meaning not replaceable). If you are handy, you can install an inline fuse that you would have to purchase at a hardware store.

Heat mats make me uncomfortable for a lot of reasons. Even when you use those silicone feet provided, the bottom of the terrarium still gets incredibly hot. And there's really no way to monitor it. With a ceramic heater emitting heat from above, you rely on raising the air temperature, rather than just contact heat from below. Then, you can also control the temp with a thermostat.

Reactions: Agree 1


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## The Snark (Jun 25, 2017)

Shop around. Many plug strip extension cords come with a fuse or each socket has a fuse. Like this: https://www.alibaba.com/product-detail/Customized-Power-Socket-and-Outlet-Multi_60534133117.html

and just stick in one of these: https://vetco.net/products/1-10-amp-mdl-slow-blow-fuse-5pk
Or just bust the hot or neutral wire and wire in an inline fuse. http://uk.rs-online.com/web/c/fuses-sockets-circuit-breakers/fuse-holders/inline-fuse-holders/


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## The Snark (Jun 25, 2017)

PS Don't forget the amendment to Murphy's law.  _The chance of an appliance or output device blowing first to protect the fuse is in direct proportion to the cost of replacing said device/appliance._

IE fuses are there to prevent catastrophic destruction and fires.

Reactions: Agree 1


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## basin79 (Jun 25, 2017)

Could be missing it but i don't seem to see a thermostat being used.

Reactions: Agree 1


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## The Snark (Jun 25, 2017)

http://arachnoboards.com/threads/tu...tension-cord-into-a-fuse.295444/#post-2646181


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## christinas (Jun 25, 2017)

Thanks everyone for the replies! I indeed did not use a thermostat. I was also considering a lamp but then some other people seem to be strictly against lamps, saying they dry out the air etc. and recommended UH's so ... For my crab tank I used pieces of wood to prop it up so that the furniture underneath doesn't come in direct contact with the heater.

@The Snark : Thanks for the advice! I know absolutely nothing about electricity and am completely incompetent when it comes to DIY, so I'd prefer to just buy something with a fuse already in it (I have no idea where I'd stick the vetco fuses). The alibaba link requires minimum 500 pieces ...

Edit: @The Snark : I do not have permission to view the link in your last message.


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## basin79 (Jun 25, 2017)

Absolutely all heat sources should be used in conjunction with a thermostat.

Heat mats are a perfectly safe heating method if used correctly.

And you're correct. Bulbs shouldn't be used to heat amphibians.

Reactions: Like 1


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## christinas (Jun 25, 2017)

basin79 said:


> Absolutely all heat sources should be used in conjunction with a thermostat.
> 
> Heat mats are a perfectly safe heating method if used correctly.


So what was incorrect about my usage of the heating pad? I don't think the presence of a thermostat would have prevented the fire.


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## Anoplogaster (Jun 25, 2017)

christinas said:


> So what was incorrect about my usage of the heating pad? I don't think the presence of a thermostat would have prevented the fire.


I think it depends on the actual cause of the fire. If it was due to overheating (like mine did), then a thermostat could help. Although, I'm not sure how you would rig that. But if it had to do with too much energy input, then a fuse is your answer. Basically, every electrical wire and appliance has a maximum load it can safely carry. Overload it, and it will burn. So the fuse is designed as a sacrificial piece, which will burn out when enough electricity passes through it. When the fuse burns, it causes a break in the connection and the appliance shuts off before it can burn.

Reactions: Agree 1


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## basin79 (Jun 25, 2017)

christinas said:


> So what was incorrect about my usage of the heating pad? I don't think the presence of a thermostat would have prevented the fire.


It might not have. But then again it might have if the mat actually caught fire due to overheating. You'll never know.


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