[newbiedude]

On a heat pump with 3 service valves one that taps inside just above the accumulator, and two that connect to the lineset: a 3/8 smaller line, and 5/8 larger insulated line. Which lines are to be used for measuring subcool and superheat in both heating and cooling modes?

 

[JJboy]

On a heat pump with 3 service valves one that taps inside just above the accumulator, and two that connect to the lineset: a 3/8 smaller line, and 5/8 larger insulated line. Which lines are to be used for measuring subcool and superheat in both heating and cooling modes?

3/8 ( LiquidLine ) - subcooling
5/8 ( Suction Line)- SuperHeat

 

[newbiedude]

3/8 ( LiquidLine ) - subcooling
5/8 ( Suction Line)- SuperHeat

For both heating and cooling modes?

 

[Marty S.]

The small line is always a liquid line unless the mfr puts a metering device before the service valve. The large line is superheated vapor only in cooling . For heating you'll use the other port.

 

[newbiedude]

The small line is always a liquid line unless the mfr puts a metering device before the service valve. The large line is superheated vapor only in cooling . For heating you'll use the other port.

Thanks.

Just to verify - with regards to measuring subcool and superheat, when in:

• Cooling mode use:
  • 3/8 (LiquidLine) - subcooling
  • 5/8 (Suction Line) - superHeat
• Heating mode use:
  • 3/8 (LiquidLine) - subcooling
  • service port taps above accumulator (Suction Line) - superHeat

Is that correct?

 

[Marty S.]

Correct. Not every heat pump has an accumulator but there will be a access port in the true suction line so you can get pressures.

 

[newbiedude]

Correct. Not every heat pump has an accumulator but there will be a access port in the true suction line so you can get pressures.

Thanks.

Out of curiosity then, if not all have an accumulator, how do you prevent liquid flood-back during defrost?