A technician starts a recovery machine on a small appliance while the valve on the receiving cylinder is still closed. What is the hazard in letting that continue?
Correct Answer
D) Discharge pressure climbs with nowhere to go, which can damage the machine or burst a hose
A recovery machine is a compressor with an inlet and an outlet. Close the outlet and it keeps pumping into a dead end, so discharge pressure rises fast. Certified machines carry a high pressure cutout that should stop them, but a cutout is a protective device rather than an operating procedure, and hoses and fittings are the weakest point in the path. The correct sequence is to open the cylinder valves first, confirm the path is clear, then start the machine, and to listen for the machine cutting out as a sign that something downstream is closed.
Why This Is the Correct Answer
With the cylinder valve shut the machine has no discharge path, so pressure climbs on the outlet side until either the high pressure cutout stops the machine or something in the line gives way. Hoses and their fittings fail before the machine does, which sprays oil and refrigerant. Opening the cylinder valves before starting removes the problem entirely.
Why the Other Options Are Wrong
Option A: The machine draws air backwards through its discharge and contaminates the appliance
The machine's own check valves and its running compressor prevent flow backward, and the problem here is on the outlet side rather than the inlet.
Option B: The appliance is pulled into a deep vacuum that damages its compressor windings
The appliance side will not reach a deep vacuum because the machine stalls or cuts out on high discharge pressure long before that happens.
Option C: The machine's oil is forced out through the low side and into the appliance circuit
Oil migrates with refrigerant flow and there is no flow while the outlet is closed. The pressure rise is what causes damage in this situation.
Memory Technique
A pump against a shut valve has only one way to express itself.
Reference Hint
Open the recovery cylinder valves before starting the machine, since a closed discharge path drives pressure up until something fails.
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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