- #1
fourthindiana
- 162
- 25
- TL;DR
- When I am recovering refrigerant from a heat pump with a recovery machine, why do I have to turn off the recovery machine and wait 10 minutes once I reach 10 Hg?
I am a student attending an HVAC program at a trade school. Today I recovered refrigerant out of a heat pump in order to debraze the compressor out of the heat pump. My instructor has taught me how to use a recovery machine to recover refrigerant out of an air-conditioner or heat pump before. My instructor tells me to recover refrigerant out of the heat pump until the pressure on the compound gauge of my gauge manifold reaches 10 Hg. Then I must turn off the recovery machine and wait for 10 min and watch to see if the pressure on my compound gauge goes back up. If the pressure in the heat pump goes back up, there is still refrigerant in the heat pump, and I need to continue recovering refrigerant from the heat pump. If the pressure in the heat pump stays at 10 Hg vacuum for 10 minutes, then there is no more refrigerant in the heat pump, and it is safe to start debrazing the compressor on the heat pump.
When I recovered refrigerant out of the heat pump today, I recovered refrigerant until the pressure on the compound gauge went down to 10 Hg vacuum. Then I started debrazing. At the actual moment when I pulled the refrigerant lines apart from each other, there was an explosion and a giant fireball. Nobody was hurt, but my instructor told me that if I used a more flammable refrigerant, the fireball would have been 3 times bigger and I would have gotten burned. The mistake I made was that after I recovered the refrigerant down to 10 Hg, I forgot to turn the recovery machine off and wait for 10 minutes to see if the pressure went back up.
I ran the recovery machine for about two hours to get down to 10 Hg. I ran the recovery machine for about 15 minutes at 10 Hg.
It seems like turning the recovery machine off and letting the heat pump sit for a few minutes after reaching 10 Hg magically gets refrigerant & oil out of the heat pump that you could not recover out of the heat pump if you tried to recover all the refrigerant & oil out of the heat pump all at once. I asked my instructor about this, and I could not understand his answer. When I recover refrigerant from a heat pump, why do I have to turn the recovery machine off once I get to 10 Hg and wait for several minutes to let the pressure rise again to get all the refrigerant & oil out of the heat pump instead of just recovering the refrigerant all at once by running several minutes longer once I get to 10 Hg?
When one is recovering refrigerant & oil out of a heat pump and the heat pump stays at 10 Hg for an extended period of time and one cannot pull all the refrigerant & oil out of the heat pump, how does turning the recovery machine off for 10 minutes make it so that you one can successfully recover all the refrigerant & oil out of the heat pump when one turns the recovery machine back on?
When I recovered refrigerant out of the heat pump today, I recovered refrigerant until the pressure on the compound gauge went down to 10 Hg vacuum. Then I started debrazing. At the actual moment when I pulled the refrigerant lines apart from each other, there was an explosion and a giant fireball. Nobody was hurt, but my instructor told me that if I used a more flammable refrigerant, the fireball would have been 3 times bigger and I would have gotten burned. The mistake I made was that after I recovered the refrigerant down to 10 Hg, I forgot to turn the recovery machine off and wait for 10 minutes to see if the pressure went back up.
I ran the recovery machine for about two hours to get down to 10 Hg. I ran the recovery machine for about 15 minutes at 10 Hg.
It seems like turning the recovery machine off and letting the heat pump sit for a few minutes after reaching 10 Hg magically gets refrigerant & oil out of the heat pump that you could not recover out of the heat pump if you tried to recover all the refrigerant & oil out of the heat pump all at once. I asked my instructor about this, and I could not understand his answer. When I recover refrigerant from a heat pump, why do I have to turn the recovery machine off once I get to 10 Hg and wait for several minutes to let the pressure rise again to get all the refrigerant & oil out of the heat pump instead of just recovering the refrigerant all at once by running several minutes longer once I get to 10 Hg?
When one is recovering refrigerant & oil out of a heat pump and the heat pump stays at 10 Hg for an extended period of time and one cannot pull all the refrigerant & oil out of the heat pump, how does turning the recovery machine off for 10 minutes make it so that you one can successfully recover all the refrigerant & oil out of the heat pump when one turns the recovery machine back on?