How Can B-Y Help? Have B-Y contact you Why Can’t I Charge With A Sight Glass Alone? When working on a refrigeration system that uses a TXV you normally have a liquid receiver. This liquid receiver stores enough extra refrigerants to properly feed the TXV under any load condition. Charging this unit to a clear sight glass in most cases will ensure that you have added enough extra refrigerant to the receiver to properly feed the TXV. If a flooded head pressure control valve is being used enough additional refrigerant must be added after filling the sight glass to ensure proper condenser flooding during low ambient conditions. The condensing unit manufacturer will normally tell you how much additional refrigerant this will require. Not adding this extra refrigerant may starve the TXV during low ambient conditions even if the unit worked fine while ambient temperatures were warmer. A/C and heat pump condensing units don’t normally have liquid receivers. The extra refrigerant required to feed the TXV under heavy load conditions must be stored in the condenser coil itself.

If a sight glass is used to charge one of these units the sight glass will only show that liquid refrigerant is leaving the condenser at the time of charging. As the load increases and the TXV throttles open, we may not have enough refrigerant stored in the condenser and a starved TXV will be the result. A lot of time may be spent looking for a leak that doesn’t exist. In the heating mode we may not get the heat output the unit is rated for. best place to buy ac unitsThe best way to charge a heat pump is by weighing in the charge or by sub cooling for A/C systems.outside unit of ac Sub cooling is the amount of temperature below the saturated condensing temperature. ac unit cost per hourThe condenser contains mostly saturated vapor. An R22 A/C system with 226 # of head pressure will have a condensing temperature of 110 F.

The majority of the condenser will contain 110F saturated vapor/liquid. Once all of the refrigerant has condensed to 110F liquid, the refrigerant temperature will begin to fall below the SCT of 110F. If the liquid line temperature is 105F the system has 5 degrees of sub cooling. The more liquid that is stored in the condenser the more it will cool below the 110F SCT. Higher sub cooling indicates more liquid stored in the condenser. Lower sub cooling indicates less liquid refrigerant in the condenser. Adding refrigerant will increase sub cooling while removing refrigerant will reduce sub cooling. The equipment model tag will normally indicate the required sub cooling a system should be charge to. When a system is charged to the proper amount of sub cooling, enough refrigerant is now stored in the condenser to properly feed the TXV under all load conditions. This method of charging is normally used in the cooling mode under normal operating conditions. Weighing in the charge is the best way to charge a heat pump especially when it needs to be charged in the heating mode.

Most heat pumps use fixed metering devices for the heating mode so sub cooling charging is not normally possible. Most Heat Pumps come pre-charged for a small amount of liquid line. The manufacturer will give a multiplier per-foot to determine how much extra charge needs to be added or removed. More refrigerant is added for longer line length while some refrigerant may need to be removed for shorter line lengths. Heat Pumps are critically charged systems that require accurate charge calculation to be weighed in to the system to ensure proper heating operation.Recharging Air Conditioners – Straight from an HVAC Specialist The cooling season is ramping up quickly here in Madison. We’re looking at temperatures in the 90’s this weekend. As our customers in Madison are turning on their AC Units, they’re discovering problems they didn’t know existed. The most common question we’ve had is about recharging AC unit Freon. We wanted to address it and explain our thoughts on recharging and exactly when it makes sense or doesn’t.

We all know that any air conditioner or furnace can fail at any time without warning. We live in a climate where we alternate hibernating and operating our mechanicals as we switch between heating and cooling seasons. Because we’ve come to depend on these units for comfort in our homes and businesses, we know all too well how that comfort can be compromised quickly when our mechanicals aren’t functioning properly. AC Maintenance and Repairs Many issues with air conditioners are a result of insufficient maintenance. The easiest repair is one that’s avoided altogether by keeping up on regular maintenance check-ups. In fact, if you haven’t been consistently maintaining your unit and notice your air conditioner starting to slack, a maintenance check-up may be just what you need to get your air conditioner back up to speed.  Below are some ways you can diagnose air conditioning problems, descriptions of some common problems your air conditioning system may experience, and some special issues you should know about the refrigerant (Freon) in your system.

Check fuse box or circuit breaker – First thing to do if your air conditioner is not functioning properly is to check the fuse box or circuit breaker that services the unit.  Air conditioner turns on and off frequently – The compressor and fan controls may be worn out. Unit turning on but not cooling – If your unit is turning on, but the air isn’t cooling efficiently, your refrigerant may be low.  You may also need to clean off the evaporator or condenser coils by brushing them off or vacuuming them. In addition, the filter may need to be replaced. Insufficient Air Flow – Dirty air filters and/or closed or obstructed supply-air and return-air grilles may cause insufficient airflow through your system. Leaks – These are usually associated with low refrigerant or a clogged drain pipe. Clogs can be fixed by clearing out the clogged pipe within the evaporator coil pan. Leaks should always be handled by a professional HVAC Contractor. Refrigerant Leaks –  If your air conditioner is low on refrigerant, either it was undercharged at installation or it leaks.

A trained AC technician should fix any leak, test the repair and then charge the system with the correct amount of refrigerant  Remember that the performance and efficiency of your air conditioner is greatest when the refrigerant charge exactly matches the manufacturer’s specification, and is neither undercharged nor overcharged. Inadequate Maintenance –  If you allow filters and air conditioning coils to become dirty, the air conditioner will not work properly, and the compressor or fans are likely to fail prematurely. Electronic Controls and Sensors Failure –  The electronic controls and sensor that cause your air conditioner, fan and condenser to kick off and on properly are often the first components to go.  Fan and Condenser Failure – Fan and condenser failure, on the other hand, can add up to some pretty pricey repairs. Replacing burnt-out fan motors is usually worth the expense in order to get your air conditioner up and running again, though a failed condenser can be a different story.

Special Note About Air Conditioner Refrigerant (Freon): Contrary to popular belief, air conditioners do not consume refrigerant (Freon) as a car consumes oil, so under ideal conditions it would never need changing or filling. Therefore, a low Freon level indicates a leak which should be repaired before adding more. Problems with Freon leaks: Low Freon levels reduce efficiency of the air conditioner. The heart of the unit is the compressor, which is cooled by the refrigerant. Over time, low Freon levels can cause overheating and premature failure of the compressor, often requiring complete replacement of the compressor or the entire condensing unit. Always contact a HVAC professional when dealing with refrigerant (Freon). Clint Pharo is a local HVAC Contractor in Madison, WI. He and his team of HVAC professionals at Pharo Heating & Cooling cover a broad range of services in commercial buildings, new home construction, and residential homes and locally represent Bryant Heating and Cooling Products.