Key Challenge:
Verifying correct refrigerant charge during cold weather can be challenging due to reduced system load.

 

We get this question alot during the shoulder months, " Its 64 degrees where I'm at, What should my pressures, SH/SC be?"

Verifying correct charge can be difficult when its cold outside and there is little to no load in the home. 

 

Verifying correct charge in cold weather is really not as difficult as one would think. This can be done one of two ways.

 

"Note: By most manufactures, Cold weather is considered as low as 55*F without Low ambient accessories. Low ambient accessories will allow us to operate as low as 0*F at the outdoor section."

 

The first way to accomplish this is by weight. We all should know by now that standard residential AC equipment comes with a factory charge that in most cases will include the Evap and 15' of line-set. We also should know by now that if we need to add refrigerant to these systems, that the appropriate amount for that is .6oz per foot or 3oz per 5 feet of 3/8 liquid line. So, all that being said, we can add up our line-set length, look at the factory rating plate of the equipment, and determine how much refrigerant should be in the system. Easy peezy lemon squeezy!

 

The second way to verify charge in cold weather is to simulate "design" conditions as best we can. Field-piece allows us to do this with their Charging jacket. This method save time as we will not need to recovery the refrigerant and weigh, pull vacuum and "re-charge". 

 

Attached is the user manual for the Field Piece charging jacket (S365)

 

Note: The charging jacket method is for TXV systems ONLY!!!!

 

Carlos

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Two Methods for Verifying Charge in Cold Weather:

1. By Weight (Recommended for Accuracy)

   • Residential AC units typically include a factory charge that accounts for the evaporator coil and 15 feet of line-set.

   • For additional line-set length, add:

   • 0.6 oz per foot or 3 oz per 5 feet of 3/8" liquid line.

   • Calculate total refrigerant based on the equipment's rating plate and your line-set length.

2. By Simulating Design Conditions (Quick Method for TXV Systems Only)

   • Use a Field Piece Charging Jacket to create simulated design conditions.

   • This method avoids the need for refrigerant recovery, vacuuming, and recharging.

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Cold Weather Conditions Definition:

• Most manufacturers define cold weather as 55°F or lower (without low ambient accessories).

• With low ambient accessories, systems can operate in conditions as low as 0°F.

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Pro Tip: The weight method ensures precision, while the charging jacket offers a faster alternative for TXV systems.