# Heat mats need a 13 amp fuse?



## r20mad (Oct 18, 2008)

I'm getting back into reptiles again after a few years out. 
I bought 4 23"x6" heat mats for my 'Really Useful Boxes' but was in need of a few more. 
Checked in the shed and found a couple of 305 x 178mm 8.5 watt Pennine Pets mats. 
Thing is, when I plugged them in, they wouldn't heat up. 
Changed the old 3 amp fuse for a 3 then a 5 amp but still nothing. Put a 13 amp fuse in (mat and plug recommend 3 amp) and work as well as the new ones. 
I only tried the 13 amp fuses because the new ones use them.
Is this okay?
The mats are undamaged and modern design (copper strips on two edges and black strips with gaps the other way.
I do have some ancient 'solid' mats but given their age, I'd rather forget about them.


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## htf666 (Jun 23, 2007)

Heat mats need a 3amp fuse max.This will take 720watts so that covers any mat you have.The old fuses must have been duff.Change to 3 amp a.s.a.p. If you use too great a fuse it might not blow if something goes wrong and start a fire.Harry


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## r20mad (Oct 18, 2008)

I know the safety side of fuses, I also know the new 3 amp fuses I tried on the old mats were good. 
The only thing I can guess is the old mats are knackered.
I actually opened the Habistat mats plug to find a 3amp fuse (not 13amp as on plug) and the mat itself states 0.07 amp.
Looks like I'll have to buy a couple more.
Thanks:2thumb:


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## fixitsan (Apr 15, 2008)

r20mad said:


> I know the safety side of fuses, I also know the new 3 amp fuses I tried on the old mats were good.
> The only thing I can guess is the old mats are knackered.
> I actually opened the Habistat mats plug to find a 3amp fuse (not 13amp as on plug) and the mat itself states 0.07 amp.
> Looks like I'll have to buy a couple more.
> Thanks:2thumb:


As the mat is rated at 0.07A (240 x 0.07 = 16.8Watts) a 1 Amp fuse ought to be more than it will ever draw.

Lightbulbs in particular, and less common among heaters, is a phenomenon called inrush current. When lamp is cold it draws several times more current than when it has reached the correct temperature. A fuse in such a circuit should be able to withstand a short rush, and you can buy slow-blow fuses for that very reason.

In your case, I would go as low as you can as far as domestic fuses are concerned, the lowest commonly available size is 1Amp, and as you can see, even if your mat draws ten times the normal current, 0.7A the fuse will still not blow , but it's still better than a 3 or 5 Amp fuse, relatively speaking


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## bilko (Oct 22, 2008)

Fixitsan is right but also all 3 pin plugs are 13 amp then you select correct value fuse for appliance so mats usually come with 3 amp fuses along with all other items that draw low current.


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