If you’ve worked on a Daikin VRV R-32 EMERION outdoor unit, you may have noticed the upper and lower Schrader ports inside the unit and wondered where they actually go — and whether there’s ever a reason to use them.
It’s a question that’s come up several times during recent startups.
After tracing the piping on a freight-damaged unit, we confirmed where both ports lead. As it turns out, they’re shown on the piping diagram — but it isn’t immediately obvious which port is which.
There is also a clear label on the unit stating not to use these ports, although we’ve found that the label is sometimes removed during installation.
Can the Schrader Ports Be Used for Refrigerant Recovery?
Short answer: Don’t use them for recovery.
Technically, you can access the refrigerant circuit through these ports. However, in recovery mode, using them only removes refrigerant from the high side of the system because of the check valve at the compressor.
That means they aren’t a good option when you’re trying to fully recover refrigerant from a closed-off outdoor unit.
For refrigerant recovery, use the king valve Schrader ports rather than these upper or lower Schrader ports.
Can They Be Used for Adding Refrigerant?
Short answer: Technically yes, but the suction ling king valve is the better option.
Both of these ports have access to the receiver. The lower port has access to the top of the receiver through the pressure regulating valve and associated solenoid valves.
If the unit isn’t running, adding refrigerant through either port would essentially push the charge into the receiver.
But there’s a more practical option: the suction line king valve. It provides access through a larger pipe and will get the charge into the accumulator more effectively. Please follow the instructions in the manual for charging and use additional charge mode, 2-20 during operation.
Neither Schrader port is particularly useful for adding refrigerant while the system is operating.
Can They Be Used to Check System Pressures?
Short answer: They can, but there’s usually little reason to.
The lower Schrader port essentially measures liquid pressure coming from the fan coils during heating mode. This is the same pressure that can be measured at the liquid line king valve.
The upper Schrader port provides a pressure reading before the subcooling heat exchanger subcools the liquid refrigerant leaving the condenser during cooling mode.
In heating mode, the upper Schrader port provides pressure after the subcooling heat exchanger from the fan coils.
There may be specific diagnostic situations where that information is useful, but for normal system performance checks, the liquid line king valve is generally the more useful location.
Field Takeaway
So, what’s the point of the upper and lower Schrader ports?
Now we know where they go and what they can tell us. But for normal charging, recovery, and system performance checks, there’s really no reason to use them.
The label on the unit says not to use these ports, and based on where they connect within the refrigerant circuit, that’s good guidance to follow.