High Flow Access Valves

I ran into something this week that I was not aware of ; a new design access valve that works like a Schrader valve with a pin to depress, but allows 5x the flow of a normal Schrader valve. They are called Coremax valves by a company named FasTest. You can’t take these cores out with a typical valve core tool. I assigned a student the task of removing a core from a Carrier packaged unit, and instead, they broke the valve. However, it was not their fault, you can’t remove these cores with a typical core tool. FasTest sells a tool that will do the trick – for $189. Alternately, you can recover the charge and take the core and the assembly that holds it out with two wrenches, which is what we did. 

Important Safety Note

Do NOT take the valve apart without first recovering the refrigerant - you will get a face full of refrigerant!

 

It is easy to tell these valves apart from regular Schrader valves if you look closely. First, the brass fitting holding the valve is larger than typical Schrader valves. Next, you can see that the top part can be removed from the bottom with a wrench Finally, the head on the pin that operates the valve is larger than the head on a traditional Schrader. The advantage of these is that they open to a full 1/4” hole just by depressing the pin – so you get faster recovery, evacuation, and charging. The disadvantage is that if you want to take the core out for even better flow or if you need to change a leaky valve core, you need their $189 valve core tool. I don’t know how many other manufacturers are using these, but I found out Carrier has been using them on packaged units since around 2006. Here is a link to a web site explaining how these valves work and showing pictures. Coremax Valves

Here is a link to a Carrier Service Bulletin that was posted on HVAC-Talk.com

So a word to the wise - if your valve core tool does not appear to fit - maybe it doesn't. You might have a Coremax valve instead of a Schrader valve.

Aluminum Coils

Aluminum coils are here to stay. Not only have they been applied successfully for years by Trane in their spiney fin condenser coils, they have also been used for years as evaporator coils in refrigerators. Now several major air conditioning equipment manufacturers are viewing aluminum coils as a potential solution to the industry wide plague of formicary corrosion in copper tube aluminum fin evaporator coils. Trane and Goodman both now use all aluminum tube and fin coils in their indoor coils for air conditioning and heat pump systems. Nordyne uses all aluminum microchannel coils for their indoor coils, and Carrier is researching the use of microchannel indoor coils. In short, you really need to be prepared for aluminum coils regardless of how you feel about them. I confess to having a prejudice against aluminum coils. One of my issues is the difficulty of repairing aluminum coils. But truthfully, today’s copper tube and aluminum fin coils are not very repairable either. The copper is so thin that it is very difficult to braze. And brazing mico leaks from formicary corrosion is a losing proposition. You plug this tiny hole and leave 3 others. Or 3 more form a week after you leave. The biggest two service differences come in coil cleaning and system charging. Most manufacturers recommend only water to clean aluminum coils. The wrong chemicals can eat them up. As with any indoor coil cleaning, if you do use a chemical – make sure it is approved for use on indoor coils. Using an outdoor coil cleaner on an indoor coil can cause noxious fumes for quite a while. Some chemical companies do manufacture coil cleaners that are approved for use on indoor aluminum coils. One thing you might look for is NSF approval. A cleaner used on refrigeration equipment around food must be NSF approved. While not necessary for air conditioners, an NSF approval should mean that there would be no toxic fumes. For more information on cleaning aluminum coils look at these instructions from York, Nordyne, and SpeedClean.  

Reading Voltage Across Switches

Voltmeters read the difference in potential from one point to another. When a voltmeter indicates a reading of 120 volts, this means that one lead is 120 volts higher than the other lead. We often refer to this as voltage drop. I find that people often misinterpret voltage readings across switches. A switch is designed to either allow current flow, or stop it by opening the circuit. A voltage reading across a switch indicates that the switch is open (off). Let’s take a circuit with a light and a standard toggle switch controlling the light. With the switch off, you will read 0 volts at the light. If you read voltage across the light switch, you will read 120 volts with the switch off. The voltage is dropping across the switch. Now if you turn the switch on, the voltage reading across the switch will change to 0 volts. Checking the light, you now read 120 volts at the light. When current travels through a switch, there should be NO drop in voltage. When current travels through a load, there SHOULD be a voltage drop. A closed switch should have a resistance of close to 0 ohms, while a load should have a measurable resistance. Using Ohm’s law to calculate the expected voltage drop across a switch you would get 0 volts because 0 ohms times any amount of current would still be 0 volts. I have often seen students looking for the break in a circuit read voltage across a switch and declare that switch is OK because they got a reading. In fact, that switch is open because they got a reading. One point to keep in mind is that the voltage across all devices in the circuit should add up to the source voltage. If you are reading 120 volts across a switch in a circuit wit a source voltage of 120 volts, there is no voltage left for the load.

HFC Agreement

Recently on June 7, 2013, President Obama and Chinese President Xi Jinping met for talks in Rancho Mirage, California. One of the agreements to come out of the talks was an agreement for both countries to work together to reduce HFC production. The statement reads

"Regarding HFCs, the United States and China agreed to work together and with other countries through multilateral approaches that include using the expertise and institutions of the Montreal Protocol to phase down the production and consumption of HFCs, while continuing to include HFCs within the scope of UNFCCC and its Kyoto Protocol provisions for accounting and reporting of emissions."

Basically, the big news is that the two biggest producers and users of HFCs agreed with each other to work on reducing their use. Europe has already started their reduction of HFC use and their regulation of F-gasses. F-gasses are their catchy phrase for all fluorinated refrigerants. I believe the F part tells us what they think of them.  There is no need for immediate panic. Notice that the agreement basically says they believe that reducing HFC production and use is something good to do. There are not yet any targets, timetables, or details. However, it clearly lays out that HFC refrigerants will be with us for a far shorter period of time than the CFCs and HCFCs they replaced. You can read more details and background in this White House Press Realease.

Lights Out!

Last night my family and I were all engaged in our own individual electronic pursuits. All of us in close proximity, but worlds away in our own individual internet enabled abstraction. A thunderstorm cut off our power and our internet connection. So lacking the ability to communicate with our far flung internet friends, we were stuck in a room talking to with each other. So we talked about what was going on in our lives. What happened at church this past Sunday, what our friends were doing yesterday, details of the lives of people whose lives are intertwined with our own. Then my son got out his guitar and started singing. Nothing on you-tube compares to the joy of making music with your family. There are certainly better guitar players and singers on line, but they are not sitting in my living room. They don’t share my name and my blood. They don’t compare. I received an early father’s day gift when my connection to the outside world was severed. Preston Stanfield live in concert in my living room.

There is not an app for that.

Random Puzzle Assembly

Many students trying to troubleshoot HVACR systems have difficulty navigating the sheer amount of data one can collect. If you go about just collecting a lot of data, it does not take very long to confuse yourself. I often see people taking resistance, voltage, and current readings on just about every conceivable location on the system without having a clear idea why they are taking the readings. This is like trying to build a 1000 piece jigsaw puzzle by just randomly trying to fit pieces together without looking at the shapes or color patterns on the pieces. When building puzzles, it helps to have a plan. There are different plans – outside edges first, organizing pieces by color, or organizing pieces by shape, but having a plan improves your chances of success. Troubleshooting is the same way. You should have a plan to organize your data collection into something meaningful. You should know why you are taking a voltage, resistance, or current reading before taking the reading. Ideally, each measurement you make should eliminate an area of inquiry. A simple example is checking the power supply to the unit. If you read the correct incoming voltage, you can eliminate that as a source of the problem. But if you don’t read the correct voltage at the power supply, then there is no need to check anything inside the unit until you have solved the power supply problem. There are probably as many systems as there are technicians. It is not too important what your system is, so long as it is based on an understanding of how the equipment functions and proceeds logically. For a non-functioning component, I generally want to know if that component is receiving the correct voltage. If it is, then I need to take a closer look at the component. Otherwise, I need to check the circuit that supplies voltage to the component. Many technicians check the line voltage and control voltage first. This does not take long and covers a large number of problems. Another technique is to start at the thermostat and work towards the non-functioning component until you find a break in the circuit, or eventually reach the component. The key point is that each piece of data you collect should tell you something. This will allow you to take far fewer readings and isolate the problem much faster.

Are You Seeing Ghosts?

Have you ever taken a voltage reading with a digital meter and gotten something that really did not quite make sense? With high impedance digital meters, it is common to get readings where you don’t expect them. This can be very confusing for students. Volt-meters are basically electrical loads. Normally, for them to read anything, they have to be in a complete circuit. The impedance rating of a meter determines the amount of current required to operate the meter. The higher the impedance, the less current required to operate the meter and get a reading. High impedance meters are preferred for electronic work because they don’t add any load to the circuit they are testing. However, high impedance meters can behave differently from older analog meters. A phenomenon called capacitive coupling can cause high impedance meters to read voltages that low impedance meters don’t read. These voltages are sometimes referred to as ghost voltages. Unenergized wires and devices in close physical proximity to energized wires and devices are charged by the energized wires in their proximity. This is a static voltage which cannot move any appreciable current. Since high impedance digital meters really don’t require a current flow to operate, they can read the ghost voltage. To differentiate between a ghost voltage caused by capacitive coupling and a hard voltage that will move current, place a load across the voltage. When loaded, a ghost voltage disappears. Some digital meters actually have settings for both high and low impedance to allow technicians to distinguish between a ghost voltage and a hard voltage. Fluke makes an adapter, SV225,  that can be used with high impedance meters to effectively turn them into low impedance meters by placing a small load across the leads. Low impedance analog meters do require a small current to operate, so they typically will not read the ghost voltage built up by capacitive coupling.