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
jrosenblum@famous-supply.com

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
jrosenblum@famous-supply.com

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
jrosenblum@famous-supply.com

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
jrosenblum@famous-supply.com

Advancing Education

I attended a monthly Dealer Association meeting and during the meeting it was announced that 2-3 members were going to retire from the business. I am sure it has occurred to us all that there may not be 2-3 new qualified personnel ready to replace the hole left behind in the HVAC fabric, and it is happening all over the country the same way. How big will this hole be in 5, 10, or 20 years?

We need to instill in the youth of today, and our associates just starting out, that success may not be quick, but that our industry is a good one to work in. That they can provide a good living for themselves and others.

When I was watching the Summer Olympics, I was reminded that there are hundreds of athletes that have competed in 5 or more Olympic trials, over a period of 20 years. They were shown early in their careers that the “long view”, not the “short view” would give them the best chance at success, along with constant training. They strive to achieve better results daily for many years.

We need to make sure we are offering our advice to both the young and new employees working for us on good practices, and to influence them to take classes and build their knowledge of constantly changing products and techniques, and that training will go on until they themselves decide to retire.

If you can show them the benefits, allow them to share in your success, and teach them the proper way to be pro table for your business, this group may end up buying your business when you want to retire instead of just filling in the “hole” in the fabric that you leave behind.

Famous University provides educational programs to professional contractors and their employees in the HVAC, Plumbing, Industrial/PVF industries, to better serve you and to help raise the standards in the fields we serve. Course schedules are located online at www.famous-university.com, and in each issue of Supply Chain.

Jim Hohman
Famous Supply Sales

Why Use a Start Assist Device On Your Compressor

Many times we receive questions as to why someone would want to install a start capacitor (5-2-1). There are several reasons why this would be beneficial. As a compressor ages it may become more di cult to start. The windings may be ne, and once it’s running it operates properly, however, sometimes it just doesn’t want to get going. Oftentimes, adding a start assist device can give the compressor a bit of a boost.

This same theory applies to new units where the compressor may have a di cult time starting. Many times technicians think the compressor needs replaced, so why would a new unit need a start cap? Oftentimes, with long line sets or TXV’s, a start cap is recommended, and newer compressors are built with closer tolerances. As we try to manufacture units with more efficiency and less chance of bypass gas (which robs efficiency) we end up making the compressor tighter. Just because a new compressor doesn’t start, doesn’t mean it’s bad. Sometimes a little boost is all it needs. Just like us, we need co ee to get us going, a compressor needs a start assist to “wake up”.

Some of the benefits of a start assist are less wear and tear on capacitors, less light dimming on startup, and reducing the chance of a breaker tripping on start up. Before you condemn a compressor, try a Start assist (5-2-1).

I was told back in the day that start assists are only for failing units. This is not true. They can be used on new and existing units without problem. I have used them successfully for years. So before you say a seized compressor must be replaced, try a 5-2-1. You may be surprised by the results.

Jeff Rosenblum
Technical Support
17 Years Industry Experience
Cell (330) 962-2491
jrosenblum@famous-supply.com

Diagnosing a Smart Valve, First Generation

First generation smart valves act as ignition controls and gas valves. There are internal and external safeties that can prevent the valve from working properly. As the valve operates on a 24V signal from a blower control or thermostat, diagnosing these valves is relatively simple.

The smart valve 1 has a 4 pin Molex plug that attaches to the top or side of the control. This 4 pin plug houses 4 wires: a 24V hot, 24V common, electronic fan timer output, and a 24V input from the pressure switch (see diagram below). You should find 24V present between the 24V hot and common at all times when power is applied to the furnace. With a call for heat, the blower control will energize the induced draft blower, which will close the pressure switch. When the normally open pressure switch closes, 24V will be introduced to the pressure switch wire at the valve. This allows the furnace to attempt to light the pilot. After ignition has occurred, the valve will send a 24V signal back out on the EFT terminal to energize the blower motor.

If the pilot light will not light, verify voltage to the pressure switch terminal and the 24V hot terminal. Check for voltage to the igniter with the igniter plug still attached to the valve. If the pilot will light but not the main burners, check flame sense to the valve. Verify that the pilot tubing is securely attached
to the valve.

Jeff Rosenblum
Technical Support
16 Years Industry Experience
Cell (330) 962-2491
jrosenblum@famous-supply.com

Static Pressure

Whether performing an installation in a new construction home or a system change-out on a 50 year old home, knowing the static pressure on your duct system may give early detection of problems that may not present themselves for several years.

Measuring static pressure gives a solid indication of the volume of air being moved throughout the system. Most residential systems are designed to operate within .5 inches of water column.

To measure the static pressure in your duct, you must have either a digital or magnahelic manometer.

  1. Drill a small hole in the return ductwork on the blower side of the filter (after the filter)
  2. Drill a small hole in the supply ductwork close to the unit
  3. Insert tubing from the manometer (+ on the supply side, – on the return side) and turn the thermostat to “fan on”
  4. If the return measures -.25 and the supply measures +. 25, the static on the system would be .5 inches of water column.

If the numbers show anything higher than the manufacturers recommended ratings, check the sizing of the ductwork (both return and supply), and the filter to verify that the system can handle the rated pressure drop.

Jeff Rosenblum
Technical Support
16 Years Industry Experience
Cell (330) 962-2491
jrosenblum@famous-supply.com

Filters

There are many misconceptions when it comes to properly sizing a filter. Many installation and service technicians believe that a filter should be sized based on a “rule of thumb”. The truth behind filter sizing lies in the required velocity and air volume for each individual system.

Calculating velocity for a system can be accomplished using basic tools and a “ductulator”. This velocity can be manipulated by increasing or decreasing the duct size. Each filter is rated at a certain velocity to provide optimal filtration. For example: a media filter may require 400 FPM to provide optimal filtration, but your duct design specifies a velocity of 800 FPM. In order to satisfy the requirements for the filter, the duct sizing should be increased as the air is introduced to the filter. Then decreased as it leaves the filter. This will allow for a velocity drop at the filter; the velocity will then increase as it passes through the remaining return duct and back to the unit.

Jeff Rosenblum
Technical Support
15 Years Industry Experience
Cell (330) 962-2491
jrosenblum@famous-supply.com

Filter Driers and When to Replace them

When an air conditioner or refrigeration unit is installed a Filter Drier is needed. That Filter Drier stays in the system as long as the AC is in service. If a repair is needed to the refrigeration side, replacement of the drier should be considered. Why would the Drier need replaced? Below are a few reasons: Does the sight glass indicate any moisture? Was the refrigeration system open to atmosphere? Was there any reason moisture could have entered the system? Was the compressor burnt out? Was there any excessive heat detected? Is the refrigerant oil acidic? Is there a chance any dirt or metal particles are in the system? If you answered yes to any of these questions then replacing the Drier should be on your “to do” list. If there is any acid in the system (proven with an acid test kit) then a Suction Line Drier is also recommended. Remember, when replacing the drier; do not heat it up to unbraze it. This can release what has been trapped in the Drier. Instead, cut it out and dispose of it. Following these easy steps will help increase the life of the system. As always, if you need any help, feel free to call the Famous Supply HVAC Tech Support Team.

Jeff Rosenblum
Technical Support
15 Years Industry Experience
Cell (330) 962-2491
jrosenblum@famous-supply.com

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