Blast from the Past

I ran into a Carrier unit yesterday that had the old compression type access valve on the suction line. I realized that there are probably many techs working today that may have never seen one of these. They were common in the late 1970’s. Most units came that way, with compression fittings for the refrigerant lines. Every manufacturer had their own type of compression nuts and ferrules. Sometimes the ferrules were shipped with a plastic plug in them and the nut hand tightened. More than once I had a unit where the nut was a little too tight and the ferrule was compressed around the plastic plug, making it useless. I don’t expect we will see those return, but I wanted to point out that what was once commonplace is no longer even recognized by most people in the field. I am sure there is technology that is common today that will seem equally strange in another 30 years. Knowing the mechanical fine points of today’s equipment is valuable for working efficiently, but that information will be next to useless in ten years. Understanding how and why systems operate and why things are done the way they are is more lasting. The physics behind the basic refrigeration cycle has not changed in 30 years and is not likely to change in another 30 years because it is based on laws of physical science. What types of connectors the refrigerant lines have, what the metering device looks like, what wires are used for control, what type of motors a unit has, or even what type of compressor it has can all change drastically in 30 years. What won’t change are the concepts of saturation, pressure temperature relationship, superheat, and subcooling. Learn all you can about why systems work because that knowledge will be the foundation you will use for understanding tomorrow’s systems. Knowing which heat pumps available today energize the reversing vale on orange and which energize on blue probably won’t be a lot more useful than being able to differentiate a Carrier ferrule from a York ferrule is today. By the way, here is what the Carrier compression access valve looks like.

 

Digital Gauge Roundup

Just a few years ago there were only a few choices if you were looking for a gauge manifold with true digital gauges. Now there are at least 16 different options available. There are also at least two new options that are very different from the others. The most expensive have a retail price in the $1,000 range, but there are at least four offerings in the $300 range. Nearly all of these are billed as Digital System Analyzers because they do more than measure pressure. All of them also measure temperature, many also measure vacuum, and all will perform calculations such as superheat and subcooling. Even though they are still a bit expensive, by the time you compare them to the cost of a set of gauges, thermocouple thermometer, and vacuum gauge they start to look a lot more affordable. If you don’t currently own a vacuum gauge and digital thermometer (not an infrared thermometer) you can consider the cost of a digital system analyzer as part of the cost of acquiring tools your are SUPPOSED TO HAVE! A vacuum gauge will cost around $200 and a thermocouple thermometer and clamp $150. When you add that $350 to around $100 for the least expensive analog gauge set that is good enough to use, you are looking at $450.

The least expensive analyzers have a standard 2 valve manifold and no vacuum gauge while the more expensive models typically have a better 4-valve manifold and a vacuum gauge. At least two models feature wireless data connectivity as well. Be aware that the prices you see usually do not include hoses. A good set of hoses can cost $100 if you are getting three 1/4” charging hoses and one 3/8” vacuum hose. If you are getting large hoses, such as Appion 3/8” or 1/2” hoses, they can cost $100 a hose. So when shopping, make sure you are getting an analyzer, a manifold, and hoses - unless of course you are going to use one or more of those pieces you already own.

The gauges that read vacuum typically switch from displaying pressure to displaying microns of vacuum at some point during the evacuation. On the subject of vacuum, one problem with having a vacuum gauge built into the gauges is that the gauges are not the best place to be checking the system vacuum. However, I have used a Fieldpiece set like this and have been generally pleased with the result. So far, our Fieldpiece SMAN4 set has held up well under student use. Yellow Jacket has a built in vacuum gauge in theirs, but a separate vacuum sensor so you can still measure the vacuum at the unit but use the built in vacuum gauge in the analyzer.

Hilmor has a digital gauge set that has both analog like displays and a digital readout. It looks a bit more like a traditional gauge set but still gives you all the digital goodies. I find the Hilmor gauges the easiest to use – no screens to scroll through and all the information on display all the time. Imperial has a brand new i-manifold which has no display! It uses Bluetooth to connect with your smart phone or tablet and uses that as the display. With the display being part of an app, it can do a lot more things and be more easily updated. You can download the app for free and use it by entering the temperatures and pressures. Pretty shrewd move! Once you get hooked on the app you will want the manifold to go with it, like the story “If You Give a Mouse a Cookie.” If you are not conversant with that reference to classic literature, you probably don’t have kids. Finally, my friends at Appion are coming out with digital high side, compound, and vacuum gauges that connect to the side port of the valve core tool they sell. No manifold needed!

I have uploaded a table of available digital system analyzers with a summary of the features of each. The file, “Digital_Gauges,” is in the Survival Kit on my Google Drive. I gleaned these from information available on the internet. The Appion gauges are not included because they are not released yet, but I saw them in March at the instructor’s conference in Baltimore. The address for the survival kit is https://drive.google.com/#folders/0B0i1Mw3czgHrLTN4M1p1LVh6Yms

Defining Amps Without Ohm's Law

Here is a pretty basic question : What are amperes (amps for short)? Many folks will tell you using Ohm’s Law. However, defining volts, ohms, and amps in terms of each other is circular logic – it does not really explain what they are – only their relationship to each other. Amperes have a definition that does not involve Ohm’s Law. Amps are a measure of electrical current flow. The flow part is important. This means that time is involved. Amps are not really a quantity, but a rate. One amp is the flow of one coulomb of electrical charge per second. Note that the coulomb is the quantity and the ampere is the rate. Compared to gallons and gallons per minute (GPM), Coulombs are like gallons and amps are like gallons per minute (GPM). A gallon is a quantity – a specific amount of water. A gallon per minute (GPM) is that quantity of water moving in a minute. To have GPM, the water has to be moving and there is a time involved. Amps are the same way: the electric current must be moving and there is time involved. So what about Ohm’s Law? Well it is great for explaining the relationship of volts, amps, and ohms. I just find it useful to explain the concept of amps as a measure of current flow first.