N_Cook wrote:

Phil Hobbs wrote in message
...
The Daring Dufas wrote:

On 3/21/2012 11:03 PM, jeff_wisnia wrote:
Over the years I've had a few thermal fuses in houshold appliances go
open for no apparent reason. When I've replaced them with ones with
the
same temperature rating they stayed working fine for years more.

A couple of days ago our three year old Bunn coffee maker quit,
because
a 141 degree celcius overtemperature thermal fuse on the water tank
opened. It might possibly have happened because the water tank
thermostat stuck closed, but after I repaired it the thermostat cycled
just as it should.

I was suprised to find that there were TWO identical thermal fuses
connected in series located right next to each other, the bodies were
actually touching. That seemed like a belt and suspenders approach,
unless there's a significant likelihood that a thermal fuse won't open
when it should?

Comments?

Thanks guys,

Jeff



I could understand parallel fuses because one may not handle the
current. Perhaps in series it's safer because the unit will shut
off if one fails to open? o_O

TDD

Nasty cheap Chinese thermal fuses-higher rate of failure to open in a
real overtemp condition-using two in series may keep your house from
burning down, if they don't both fail the same way.

Perhaps the voltage rating was lower than the required use, ie in fused
state not rated for the service voltage across the broken section so someone
thought, I know , we'll put 2 in series ;-)

Nah, even good equipment is made that way. I sort of collect
European-made espresso machines, and they all have two thermal fuses in
series with the thermostat. (I don't collect the fancy ones, you
understand--I just took a fancy to the long-discontinued Krups Il Primo,
because it has the best designed valve in the business. I've bought
about 5 off eBay at various times.)

Cheers

Phil Hobbs