Fixing space heater - 128˚ fusible link blown.

Thread Starter

Tonyr1084

Joined Sep 24, 2015
7,901
No idea why the FL (Fusible Link) blew (yet). First inclination is to replace it.

Markings are
Microtemp
SBDCVY
G4A01
128˚ C

Tried googling it but am not sure what I'm looking for. Went on Ebay and found "Microtemp" and "128˚ C" fuses rated at 10 amps. However, I've seen other FL's rated at 128˚ C @ 15 amps.

The heater (thermal element) is rated at 1500 watts. That would suggest 12.5 amps. Given the very small amount of current drawn in addition by the electronics, it looks like 10 amps just won't cut it.

Here's one rated for 15 amps:
http://www.ebay.com/itm/128degreeC-...103169?hash=item1eab3fc981:g:ZkEAAOSwyQtVrEXZ

And here's one rated for 10 amps:
http://www.ebay.com/itm/10pcs-Micro...002969?hash=item464e473fd9:g:q0AAAOSwxehXPELs

How do I know for sure which one is the one I need? At first GUESS I'd say I need the 15 amp unit, given I'm drawing 12.5+ amps during normal operation. The FL is on the Line side of the power cord, before all electronics. In other words, EVERYTHING goes through it.

Of course, the RIGHT part means proper protection from fire and other hazards, so I don't want to just bypass it. Besides, I haven't yet figured out why the FL blew in the first place. The electronics on the board (and the PCB) look pristine, but that doesn't always mean anything.

Your help is appreciated. Thanks.
 

AlbertHall

Joined Jun 4, 2014
12,346
The attached pdf includes this paragraph:
"G4 SeriesRated for continuous operating currents up to 10 amps @ 250VAC (15 amps @ 120VAC), the G4
series MICROTEMP® TCO is the industry standard for over-temperature protection. The G4 series is
applied to millions of appliances and personal care products each year, providing reliable back-up
protection for temperature controlling thermostats and other over-temperature conditions. The
G4 series is also widely applied in office machines, portable heaters and industrial equipment as a
thermal safeguard. "
 

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Thread Starter

Tonyr1084

Joined Sep 24, 2015
7,901
Honestly, I'm not comfortable putting something rated for 10 amps when I know the circuit will use at least 12.5 amps. The engineering doesn't make sense to me. Why fix it to blow it out again? What would be the danger in using something rated to handle 15 amps? I still have the thermal protection. And given the nature of the heat element, I don't see it failing and suddenly drawing a rush of current. Besides, it would be on a 20 amp breaker circuit - so even if it dead shorted the house wouldn't run any risk of fire.

Of course, if the heater over heated, having it blow at 128˚ C (262˚ F) will still blow the FL. So there's still protection at the current rated temperature.

Anyone have any practical advice? Words of wisdom? Any concerns, cautions, warnings?
 

AlbertHall

Joined Jun 4, 2014
12,346
The G4 series is rated for 15A at 120V. From my link above:
"G4 SeriesRated for continuous operating currents up to 10 amps @ 250VAC (15 amps @ 120VAC)"
 

wayneh

Joined Sep 9, 2010
17,498
There's also a distinction between peak and continuous current, and obviously you want to compare on the same basis. I think these ratings are both continuous, but it makes me nervous when I see the word "max". What does that mean? It's hard to tell from only those listings.
 
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