Ok, without looking it up somewhere, at what temperature does the
fusible plug blow on the refrigerant system for a R-22 carrier heat
pump? (50TJ series)
Next question, how in the hell can it get that hot in order to blow
out, blowing all the freon into the atmosphere?
And last but not least, what is the saturated pressure of r-22 at that
If I recall, Fusible plugs really are not for pressure relief due to a fan
failure or plugged condenser. A mechanical relief valve is meant for that.
A fusible plug is really designed for a unit located in a fire. This would
allow the refrigerant to blow off before an excessive amount of pressure
could rupture the receiver/system and cause injury or death. Its true that
they sometimes fail due to high pressures but originally it was a UL thing
for fire, If I recall my facts correctly. I can look at my old Sam's if this
discussion goes further.
Ive not heard that one but I have seen a lot of Carriers and Bryants
with blown fuseable plugs. Always found them on outdoor units with bad
cond motors, leaking suction accumulators, leaking evap or condenser
coils or screwed up rev valves. Never saw one in a fire yet.
Maybe Carrier, (WHICH btw is very possible) has it on their units for low
temp release. But I'm very very sure (99.9%) that in refrigeration they
mostly are for fire and shipping. Shipping is a big thing as well, a vessel
that carries so many pounds of refrigerant must have a relief that if fire
hits it the unit will release verses explode.
I've seen them on Carriers too, on the discharge line if I recall, but never
found one that leaked.
I'll see if I can even find my books on the subject and if I do I'll look it
up. Maybe AC and Refrigeration is different.
I've seen these plugs ONLY on carrier products, ie Bryant, Carrier,
Day & Night, BDP etc. On the older models they're mounted between the
accumulator & comp in the copper tubing, the one that blew was located
on the top of the accumulator. Rated to blow at 210F. In my case
the rev valve is stuck half way between ht & cool. Natchurly I didnt
find that out until i evacuated and dropped in a charge. :(
fyi- <most> fusible links (fire dampers, smoke dampers) etc melt at
Link to various low melt point alloy and showing actual melting temps.
( Thought wouldn't hurt to divulge...little trade secret...esp beings as
someone was suggesting just the other day to fill tubing with sand prior to
On Wed, 03 Jan 2007 00:46:10 GMT, firstname.lastname@example.org wrote:
Dont actually know the temps but dont care or matter either. Its an
old one. They usually blew because the coils or elsewhere were leaking
refrigerant. The unit runs hot, the plug melts and out goes the
refrigerant. Rretty stupid design but very cheap to make. As usual,
Carrier's engineering that says, "Screw the customer. We will protect
our compressor. We dont care what it costs the customer to repair."
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