Before the first hose goes onto a small appliance, a careful technician evacuates the recovery hoses and the manifold. What problem does that step prevent?
Correct Answer
D) It stops the air trapped in the hoses from being pushed into the recovery cylinder
Hoses and a manifold that have been sitting open are full of room air. Once the machine starts, that air is the first thing it moves, and it ends up in the recovery cylinder as a non condensable. Air in the cylinder raises the pressure, makes the cylinder harder to fill to its limit, and ruins the recovered refrigerant for reuse in the same appliance. Pulling the hoses and manifold down before connecting to the appliance costs a minute and keeps the cylinder holding refrigerant rather than a refrigerant and air mixture.
Why This Is the Correct Answer
Everything inside the hoses and manifold when the job starts gets pumped into the recovery cylinder. On a set that has been open to the shop, that is a volume of air, and air does not condense at cylinder pressures. It sits in the vapor space raising the pressure and contaminating the refrigerant underneath. Evacuating the hose set first means only refrigerant from the appliance reaches the cylinder.
Why the Other Options Are Wrong
Option A: It stops the recovery machine from short cycling on its own low pressure control
Low pressure controls on a recovery machine respond to the appliance side pressure, not to a small pocket of air in a hose.
Option B: It stops the appliance from losing charge into the hoses before the machine starts
Charge only moves into the hoses once a valve is opened, and the small volume involved is recovered along with everything else.
Option C: It stops oil from the previous job travelling into the appliance being worked on now
Oil carryover into hoses is a genuine nuisance, but the reason for evacuating a hose set is the air in it, and evacuation does not remove oil films anyway.
Memory Technique
Whatever is in the hose gets a free ride to the cylinder.
Reference Hint
Evacuate or purge recovery hoses and the manifold before connecting, so shop air does not end up in the recovery cylinder.
More epa-608-type-1 Questions
An under-counter ice maker is one factory-sealed cabinet, while a modular ice machine head is joined to a remote condenser by field-run tubing. What certification does servicing the modular machine's circuit require?
A technician recovers refrigerant from a small appliance using a recovery machine that was manufactured in 1991. What recovery level must that older equipment achieve?
Two technicians recover from identical refrigerators with working compressors, one using a 1991 recovery machine and the other a 2015 machine. Why do their required recovery levels differ?
System-dependent recovery equipment may be used only on appliances that normally hold up to what amount of refrigerant?
What feature defines a self-contained recovery unit and sets it apart from the system-dependent kind?
When system-dependent recovery equipment is used on a small appliance whose compressor still runs, how can that working compressor be put to use?
Recovery from a small appliance has slowed down and the pressure is barely moving. What accepted technique helps drive the remaining refrigerant out?
After the recovery unit stops pulling on a small appliance, how does a technician confirm that the recovery is actually complete?
A sealed small appliance offers no service port at all. What has to happen before recovery equipment can be connected to it?
As refrigerant from a string of small appliances collects in a recovery cylinder, what fill limit applies to that cylinder?
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