How to Determine and Overcharged Unit with a TXV

This quarter’s Tech Tip is brought to you by Allied Air.

When a unit is slightly overcharged with a TXV metering device, both suction and superheat may appear normal but the performance and efficiency are diminished. These conditions are caused by the TXV as it meters refrigerant flow into the evaporator and excess charge is stored in the condenser. If excess charge levels are extremely high, this elevates the head pressure and liquid sub-cooling levels. If the charge is high enough, the suction pressure may be high with low superheat present.
When charging R-410A systems, always charge as a liquid and follow the procedure below:
•  Operate unit a minimum of 10 minutes before checking charge..
•  Measure liquid service valve pressure by attaching an accurate gage to service port.
Measure liquid line temperature by attaching an accurate thermistor type or electronic thermometer to liquid line near outdoor coil.
•  Calculate subcooling (saturation temperature—measured temperature) and compare to table on back of control box cover
•  Add refrigerant if subcooling is lower than range shown in table. Recover refrigerant to decrease subcooling.
 If ambient temperature is lower than 65°F, weigh refrigerant according to the nameplate data.

As always, if you need assistance with charging please feel free to contact the Famous Supply Technical Services Department.

Jeff Rosenblum
Technical Support
19 Years Industry Experience
Cell (330) 962-2491

How safe is the home that you’re entering

Hello all! I have a question. How safe is the home you are entering and how safe is that home when you leave? Do you know?

So, what exactly am I taking about? Carbon monoxide. We are in the heating season now and unfortunately we are going to hear stories on the news about CO poisoning. This is an ongoing issue and we hear about it every year. There are too many stories of families, businesses and daycares having CO issues. One story that comes to mind was from a few years ago. There was a daycare in the basement of a church. The boiler was having issues and was causing CO levels around 400ppm in the air. The teachers noticed a problem when all 20 kids were getting sick and so were the adults. Was the CO level of this boiler ever checked?

Now we all know that CO is a product of incomplete combustion. But how do we know if it’s incomplete? We’ve all probably heard that if the flames are blue then it’s burning clean. That is a pure myth. We cannot judge the safety of the equipment based on the color of the flame. We must test it!

In order to test it you need to use a combustion analyzer. There are several on the market right now. By utilizing a combustion analyzer we can determine CO, O2, CO2, flue temp and efficiency and much more. In this day and age we simply cannot guess. We must test! By testing the equipment, we can determine if there are any potential safety concerns. Now you can feel better that at the time you leave, the equipment is running correctly.

So what is correct? We like to see CO levels no higher than 100ppm undiluted and stable. Lower levels are always better but we need to make sure it is stable. This is just the beginning of combustion testing but a good starting point. As a note: CO should be tested in the equipment, undiluted, not in the air. Testing for CO in the air has its merits but often leaves potential issues unseen.

So going forward lets make sure we are well equipped this winter and we test everything.

If you need any additional info please don’t hesitate to call the Famous Supply HVAC Tech Dept. Have a safe winter!

Jeff Rosenblum
Technical Support
19 Years Industry Experience
Cell (330) 962-2491

How to Test a Pressure Switch

To test a pressure switch, you must first have a compound pressure gauge (digital or analog). Install a plastic tee for both the positive and negative ports for the pressure gauge, start up the unit and observe the reading on the gauge. The reading must be higher than the setting listed on the pressure switch. If the pressure switch only has one port, install the tee in the correct port of the pressure gauge and leave the other port open to atmospheric pressure. If the reading on the gauge is lower than that of the switch then the problem is in the furnace or venting. If the reading on the gauge is higher than that of the switch and the switch is not closing, then the problem is the switch. If you need technical assistance please call the Famous Supply Tech Support Team.

Jeff Rosenblum
Technical Support
18 Years Industry Experience
Cell (330) 962-2491

Importance of a Filter Drier

Hello all! For this Supply Chain our Technical Tip is straight from Allied Air regarding the use of a filter drier. Using the correct drier and following proper installation procedures will aid in the longevity of the system.

A filter drier is designed to remove moisture from a refrigeration system. It uses desiccant material or a substance to absorb the moisture in the system. The desiccant is designed for a specific oil base in the refrigerant system and should not be interchanged. It also filters foreign particles, which prevents these substances from circulating in the system. If moisture is not removed from the system it can cause hydrochloric and hydro fluoric acids to form, which can damage the system.

A liquid line filter drier needs to be used in any new installation and any time a system is opened to the atmosphere. On the Allied product line, most models have the liquid line drier already factory installed. If not, it is shipped with the outdoor unit. A liquid line filter drier is used because refrigerant in the liquid state is the best place to catch moisture in the system.

There are two different types of liquid line filter driers and do not need to be confused. The first is a one-way drier, which is primarily used on straight air conditioners. The second type is a bi-flow liquid line filter drier that is primarily used on heat pump type units. To prevent getting these two liquid line driers confused there is an arrow on the drier to show which direction the refrigerant may flow. These flow directions are extremely important. If not selected correctly this will create a restriction in the refrigerant circuit causing nuisance calls and extended time trouble-shooting the equipment. If you need technical assistance please call the Famous Supply Tech Support Team.

Jeff Rosenblum
Technical Support
18 Years Industry Experience
Cell (330) 962-2491

Properly Evacuating ACs & Heat Pumps

Warm weather is fast approaching, and with that comes an increase in air conditioner installs. This brings up an important topic: correctly evacuating a system. The right way has nothing to do with time; it’s about the level vacuum achieved and if that level held when isolated.

Be sure to have the tools listed below for the job otherwise the task cannot be properly performed. Do NOT proceed until you are properly equipped.

  • Vacuum pump with extra oil
  • Micron gauge
  • Evacuation hose and vacuum rated core puller (optional)

First we’ll use the evacuation hose and core puller. Connect the core puller to the liquid line service port and remove the core. Next, connect the hose to the core puller and the larger end to the vacuum pump. Then connect the micron gauge to the suction service port. Lastly, turn the micron gauge on and start the pump. Allow the pump to run while keeping an eye on the micron gauge. Most manufacturers recommend a level below 500 microns.

Removing the “air” is easy and is usually done by 5000 microns. Dehydrating the system is a bit more di cult and requires a deep vacuum. How are we actually removing moisture? As we pull a deep vacuum we reduce the boiling point of water, which allows the moisture in the air to boil o at ambient temperature.

Once we’ve achieved the correct micron level, isolate the pump from the system by closing o the valve on the pump or by closing the valve on the core puller. Wait about 30 minutes. If it holds vacuum without going over the 500-micron mark, the system is sealed and properly dehydrated. You may need to pull below 500 microns to get it to hold at 500 when isolated. This method is good for most residential systems. Commercial, industrial, and refrigeration systems may have a different goal.

It’s hard to say exactly how long it will take. Having fresh oil in a properly functioning vacuum pump will help speed things along. If you need technical assistance please call the Famous Supply Tech Support Team.

Jeff Rosenblum
Technical Support
18 Years Industry Experience
Cell (330) 962-2491

Why We Use Dry Nitrogen

We are gearing up for the air conditioning start up season and you know what that means: more AC installations. As the number of installs increase, so does the workload. Let’s not forget one critical part of any AC installation—the use of nitrogen while brazing.

Why do we use nitrogen? Nitrogen is an inert gas, meaning it is not chemically active. By using nitrogen, we prevent oxidation inside the tubing. But what causes oxidation, and why is important to us? When we are brazing copper, we use a lot of heat. This heat can cause the oxygen to react with the copper and cause oxidation. Have you ever noticed a black residue on the outside of the copper lines after brazing? Without nitrogen, this happens on the inside of the tubing also. Externally, this looks bad. Internally, this can cause harm. The black residue can break free and circulate with the refrigerant throughout the system. This can plug strainers and cause bearing damage to the compressor.

Over the years, I’ve seen a number of installs that were done without nitrogen. I have seen many plugged strainers, bad TXV’s, and ruined compressors. This is not something that we want to see on any installation, let alone a brand new one. This is a warranty call waiting to happen.

So what is the proper method? Once the piping is all fitted together, remove the Schrader cores from the service valves. Hook up the nitrogen to one of the service valves and add nitrogen. The pressure should be just enough to push the oxygen out. Allow the nitrogen to purge through for a few minutes (or longer if the line sets are long). Once this is done, release the pressure but keep a small amount of nitrogen owing through the tubing. This will keep nitrogen in the system without causing so much pressure that it will blow the braze out. Now the line can be brazed together. Once done, the nitrogen is already hooked up for a pressure test.

Using nitrogen while brazing will ensure no oxidation occurs in the system, which will reduce warranty calls. As always, if you need any technical assistance please call the Famous Supply Tech Support Team.

Jeff Rosenblum
Technical Support
18 Years Industry Experience
Cell (330) 962-2491

Understanding Mitsubishi Wire Sizes

Recently I have been receiving a lot of questions regarding the wire sizes that connect to the indoor units and line set sizes on Mitsubishi equipment. Here is a brief explanation:

  • An M Series 1-to-1 system (1 indoor, 1 outdoor) wire size is 14GA
  • A P Series 1-to-1 system is 16GA
  • An M Series Multi-Zone without a branch box is 14GA
  • An M Series with a branch box requires 16GA wire from the indoor head to 
the branch box. It also requires 16/2 stranded shielded wires to be run from the branch box to the outdoor unit. It will also need 14/2 to be run from the branch box to the outdoor unit (this powers the box). This wiring must be followed for proper operation.

The last thing to bring up is the line set sizing. Line set sizes must follow what the indoor unit requires. For example:

If the indoor unit requires 1/4″ – 3/8″ then the line set must be 1/4″ – 3/8″ regardless of the port of the outdoor unit or branch box. If a change in size is needed to connect to the outdoor unit or branch box, we sell adapters to be used at the outdoor unit or branch box.

If you have any questions please feel free to contact the HVAC Technical Support Team.

Jeff Rosenblum
Technical Support
18 Years Industry Experience
Cell (330) 962-2491

Cold Weather is Coming!

Sorry to break it to you, but cold weather is coming. Before you start throwing tomatoes my way, this is only some advice to help you be prepared.

So what do you need to be prepared to brave the cold weather? I’m not talking about long johns and snow boots. I’m talking about tools! Unfortunately, we get so wrapped up in the heat that we often times forget to get our tools ready. Below is a partial list of tools you should have ready to take on the majority of problem calls.

  1. Combustion Analyzer (fresh batteries and professionally calibrated)
  2. Oil test kit (smoke test papers, etc.)
  3. Draft gauge
  4. Hygrometer (used to test humidity levels)
  5. Multimeter
Dual port manometer (to test static pressure and diagnose pressure switches)
  7. Typical hand tools

If you need any tools to help you get through this heating season, feel free to stop by your local Famous branch to see our selection. If you need any advice or tech support, please call our Famous Tech Support Team.

Jeff Rosenblum
Technical Support
17 Years Industry Experience
Cell (330) 962-2491

14 SEER Heat Pump System Replacements

We’ve had numerous questions over the last few weeks where a heating contractor is replacing a heat pump system for a homeowner and they want to use the existing air handler and just replace the coil inside. There are various reasons why you can’t or you shouldn’t replace only the coil. Instead, replace the entire air handler.

  • The minimum efficiency is 14 SEER, it’s practically impossible to find a coil that will t in the air handler that AHRI matches to the heat pump.
  • If you decide to use a non-AHRI matching coil, the system is not going to work properly and will have significant operation issues.
  • Replacing the entire system gives the homeowner a brand new system warranty on ALL parts.

We’ve seen the negative side effects when trying to match up a coil or selecting the wrong coil. We have seen liquid slugging back to the compressor in AC mode and head pressure issues in heating mode. Both of these issues can reduce the lifespan of the equipment.

It is fitting to also talk about airflow. Proper airflow must be set and verified before the charge can be checked. I always tell people that if I purchased a 3-ton system, I want 3 tons of air! Why sell a 3-ton system but only deliver 2 tons? Incorrect airflow can cause several issues like:

  • Incorrect superheat and subcooling
  • Poor humidity control
  • Head pressure issues in heating mode
  • Inefficient operation
  • Nuisance lockouts
  • Excessive use of backup heat, and more

As always, if you need any help with your heat pump, feel free to call the Famous Supply Tech support department at 330-962-2491.

BY JEFF ROSENBLUM – Training & Technical Support
& COLLIN MURPHY – Armstrong Air/Concord Equipment Specialist

Mitsubishi Electric Updates and Applications

Hello Everyone! As the HVAC industry changes so does the Mitsubishi Electric line- up. I would like to take a moment to introduce some of the newest Mitsubishi units.

PUY-6 P series cooling only unit: Mitsubishi released the -6 cooling only P series unit. This unit has the ability to run in cooling mode down to -20 degrees outside (with the use of the 3 piece wind baffle). This makes it a great option for server rooms where non-critical cooling is needed.

MXZ Multi-Zone Hyper-Heat units: Yes, that’s right! A multi zone unit that is hyper heat! This has the ability to provide heating down to -13 degrees or lower. They can provide 100% capacity at 5 degrees.

MVZ Air Handler: Mitsubishi has finally released their air handler. This is available in 12, 18, 24, 30, & 36 KBTU’S. This unit must be teamed up with their multi zone unit. This can be used to replace an existing air handler, and match to a Mitsubishi outdoor unit.

Thermostat interface: The interface allows the usage of a conventional 2 heat 2 cool thermostat. The homeowner can then use a thermostat that they are comfort- able with, or one they prefer the look of.

Kumo Cloud: The Kumo cloud is Mitsubishi’s wireless app-based interface. You can download the app and control your equipment by your phone or tablet.

6,000BTU one to one Hyper-Heat Heat Pump: When a 9,000 is just too big, Mitsubishi has released their 6,000 BTU hyper heat system.

MFZ-KJ floor mount 1 to 1 Hyper-Heat system: An excellent option for the home where a wall mount system won’t t. Available in 9, 12, 15 & 18 KBTU’s

That sums up the new releases in the land of Mitsubishi. These systems can be ordered if it is not in our current inventory. As always, feel free to contact the Famous Supply Technical Support department if you have any questions.

Jeff Rosenblum
Technical Support
17 Years Industry Experience
Cell (330) 962-2491

Posts navigation

1 2 3 4 5
Scroll to top