Sunday, July 27, 2014

EPA Proposes Ban on R-404A and Other Refrigerants

You may have heard that the EPA is proposing to ban the use of some common refrigerants  I would like to give a brief overview of things you should know about this proposed ruling. First – at this stage it is still a proposal – not a ruling. Typically the way this works they publish a proposed ruling, allow us to comment on it, revise the ruling based on the comments (if they choose to), and publish the final ruling.  Since this is still a proposed ruling, you have a little time before it will take effect. Second, not all industries are affected by this ruling. Air conditioning caught a break – air conditioning systems are not covered . However, motor vehicle air conditioning IS covered. For motor vehicle air conditioning the big news is that 134a will no longer be acceptable in NEW VEHICLES beginning January 2016. A large number of zeotropes are also banned from use in new vehicles, but most of those are mainly used today as an R12 substitute. That should not have a great effect because they are only banned in NEW vehicles.

Retail refrigeration appliances and vending machines are also covered. The big news here is that R507 and R404A will be considered unacceptable for both new AND retrofit applications in retail refrigeration beginning January 2016. Retail refrigeration would include things such as display cases in grocery stores.

Four areas that are NOT covered by this proposed rule (yet) include cold storage warehouses, ice machines, refrigerated transport, and industrial process  refrigeration. However, the EPA is specifically asking for comments about the possibility of using low GWP refrigerants in these areas as well.
 “EPA requests comment on the use and viability of both low-GWP refrigerants (e.g., R-744, R-717, and HCs) and other HFC-blends (e.g., R-407A and R-407F) and the possibility of listing R-404A, R-507A, and other high-GWP blends unacceptable in any or all of these four end-uses.” I encourage you to do some of your own research into this. Here is a link to the proposed RULING. Here is a link to a FACT SHEET about the ruling. Here is a table summarizing the proposed changes to the auto air conditioning and retail refrigeration refrigerants.


Refrigerant Uses Deemed Unacceptable as of January 1, 2016
End-use
Substitute
Further Information
Retail food refrigeration (new and retrofit)
R-404A
R-404A is a blend, by weight, of 44% HFC-125, 4% HFC-134a, and 52% HFC-143a. It has a high GWP of approximately 3,920. Other substitutes are available for this endues with lower overall risk to human health and the environment.
Retail food refrigeration (new and retrofit)
R-507A
R-507A is a blend, by weight, of 50% HFC-125 and 50% HFC-143a. It has a high GWP of approximately 3,990. Other substitutes are available for this end-use with lower overall risk to human health and the environment.
Retail food refrigeration (condensing units and supermarket systems) (new)
HFC-227ea, R-407B, R-421B, R-422A, R-422C, R-422D, R-428A, R-434A
These refrigerants have GWPs ranging from 2,729 to 3,607. Other substitutes are available for this end use with lower overall risk to human health and the environment.
Retail food refrigeration (condensing units and supermarket systems) (retrofit)
R-407B, R-421B, R-422A, R-422C, R-422D, R-428A, R-434A
These refrigerants have GWPs ranging from 2,729 to 3,607. Other substitutes are available for this end use with lower overall risk to human health and the environment.
Retail food refrigeration (stand alone units only) (new only)
HFC-134a
HFC-134a has a Chemical Abstracts Service Registry Number (CAS Reg. No.) of 811-97-2 and it is also known by the name 1,1,1,2-tetrafluoropropane. HFC-134a has a relatively high GWP of 1,430. Other substitutes are available for this end use with lower overall risk to human health and the environment
Retail food refrigeration (stand alone units only) (new only)
FOR12A, FOR12B, HFC-227ea, IKON B, KDD6, R- 125/290/134a/600a (55.0/1.0/42.5/1.5), R-407A, R-407B, R-407C, R-407F, R-410A, R-410B, R-417A, R-421A, R-421B, R-422A, R-422B, R-422C, R-422D, R-424A, R-426A, R-428A, R-434A, R-437A, R-438A, RS-24 (2002 formulation), RS-44 (2003 formulation), SP34E, THR-03.
These refrigerants have GWPs ranging from approximately 550 to 3,607. Other substitutes are available for this end-use with lower overall risk to human health and the environment.
Vending machines (new and retrofit)
R-404A
R-404A is a blend, by weight, of 44% HFC-125, 4% HFC-134a, and 52% HFC-143a. It has a high GWP of approximately 3,920. Other substitutes are available for this endues with lower overall risk to human health and the environment.
Vending machines (new and retrofit)
R-507A
R-507A is a blend, by weight, of 50% HFC-125 and 50% HFC-143a. It has a high GWP of approximately 3,990. Other substitutes are available for this end-use with lower overall risk to human health and the environment.
Vending machines (new only)
HFC-134a
HFC-134a has a Chemical Abstracts Service Registry Number (CAS Reg. No.) of 811-97-2 and it is also known by the name 1,1,1,2-tetrafluoropropane. HFC-134a has a relatively high GWP of 1,430. Other substitutes are available for this end use with lower overall risk to human health and the environment
Vending machines (new only)
FOR12A, FOR12B, IKON B, KDD6, R- 125/290/134a/600a (55.0/1.0/42.5/1.5), R-407C, R-410A, R-410B, R-417A, R-421A, R-422B, R-422C, R-422D, R-426A, R-437A, R-438A, RS-24 (2002 formulation), SP34E.
These refrigerants have GWPs ranging from approximately 550 to 3,085. Other substitutes are available for this end-use with lower overall risk to human health and the environment.

Saturday, July 19, 2014

Dryer Sheets In The Coil

Recently, two different techs have told me stories about finding dryer sheets used creatively in customers air conditioning systems.  When they asked their customer why there were bunches of dryer sheets stuck to the air filter, the customer said they liked the “clean, fresh scent.” Another story involved customers removing supply registers and stuffing  dryer sheets across the outlet of the register to “filter and freshen” the air. Naturally, some of these found their way to the coil where they clogged the coil and caused enough air flow restriction to freeze the system up. In all cases, dryer sheets stuffed into clever places only serve to restrict the airflow. Even if they did not, all you are accomplishing is introducing whatever chemical is on them into your system. They don’t remove odors – they just add more. Honeywell used to sell a system to do that called the “Scentrol.” Scentrols used little gel cans that looked like sterno. They system controlled how much air circulated over the can to regulate the scent. It even had a wall control. My father sold one to a customer who also bought an electronic air cleaner with an activated charcoal filter to remove smells. The customer insisted on having the Scentrol installed, even after dad explained that they were buying one machine to put smells in the air and another to take them out. Here is a link to an online forum that has a picture http://www.hvacproforums.com/threads/honeywell-scentrol.1148/

So what do you suggest to customers who want the air conditioner to improve their home’s odor? I don’t think you can buy a Scentrol anymore. First, try to find out if there are specific odors they are trying to get rid of. Finding and eliminating the source is really the best option. My brother once discovered that the kitchen sink drain leaving the disposal had never been connected on a new house in which the customers were complaining about dirty sock syndrome. If the odors are system related, look at the condition of the indoor coil and make sure there are not problems such as a leaky return in a crawl space. If they just like the idea of having a “fresh scent” system there are a number of filters that use activated charcoal to absorb odor. Just check that the pressure drop across the filter is not too high. Like the famous 1” pleated filters, some of the charcoal filters can add enough restriction to cause an airflow problem even when they are clean. Another option would be an air cleaner that uses titanium dioxide and UV light to eat up compounds that cause odors. Both Field Controls and Lennox make air cleaners that use this technology.  Now you are on the high end of the cost spectrum, but you are dealing with solid, reputable companies who sell things that work.

Sunday, July 13, 2014

Check System External Static BEFORE Sealing Ducts

I recently read a thought provoking article by David Richardson in the July 7 Air Conditioning Heating and Refrigeration News. In it he argues that sealing an undersized duct system can cause problems. The system cooled BEFORE you sealed the ducts, and now that you have worked on it, the system cannot move enough air to stay operating. I know I have seen many systems with marginal ductwork that still managed to operate, even if inefficiently. The duct leaks could be allowing just enough extra air flow to keep the system operating. The combination of leaks on both the return and supply sides of the system serve to reduce the static pressure difference against which the fan must move the air. If the static pressure difference between the return and supply is already at or past the limit the manufacturer publishes for their system, sealing the ducts will increase the already high static pressure difference and push the system over the edge. This is why Mr. Richardson advises taking a reading of the total external static pressure difference BEFORE sealing the duct to avoid this trap. If it is too high, the duct system will need more attention than just sealing – it will need some duct modifications as well. Better to know before you do the job. What is too high? I don’t like to see anything higher than 0.8” wc – that is usually the top end on most residential systems. Most residential systems will operate comfortably around 0.5” wc. Some will go all the way to 1” wc, but at a cost. With ECM fan motors you are burning electricity to shove air through restrictive ductwork. With PSC blowers you lose airflow at high external static pressures. This costs electricity in another way. The suction pressure drops, the compression ratio increases, and system capacity decreases – causing extended run times and inefficient operation.

Thursday, June 26, 2014

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.
 

Friday, June 13, 2014

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

Wednesday, June 4, 2014

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.

Friday, May 30, 2014

Sensible and Latent Cooling

When you look at manufacturer’s tables showing the capacity of their units, you will notice terms such as latent capacity, sensible capacity, or total capacity. The sensible capacity expresses the unit’s ability to reduce the air temperature. In most conditions, only part of the system cooling capacity goes into reducing the air temperature. The name comes from the idea that this change in heat can be sensed, or measured with a thermometer. I have had students tell me they remember it because it makes “sense,” and is therefore “sensible.” The word latent means hidden. Latent cooling capacity is used to take water out of the air. It is latent, or hidden, because you cannot measure it through temperature change. Latent changes involve a change of state. The water in the air is changing state from a vapor to a liquid. To accomplish this, the heat that went into the water to vaporize it must be removed. A system’s capacity is not fixed – it changes with the temperature, relative humidity, and volume of the air blowing across the evaporator coil. System capacity used for latent cooling is not available for sensible cooling. So as you increase the percentage of latent cooling a system performs, you decrease its sensible capacity. Here in the southeast, latent cooling is just about as important as sensible cooling. We MUST remove water from the air to be comfortable. In other parts of the country, such as the southwest, taking water out of the air may be undesirable. We can have some control over this by controlling the airflow. As a general rule, as you increase airflow across the evaporator coil, you increase sensible cooling and decrease latent cooling. In a humid area it makes sense to set the system airflow to a level that will increase latent cooling. For example, 350 CFM per ton rather than 400 CFM per ton. In a dry area, you may want to increase airflow to minimize latent cooling. For example, 450 CFM per ton. Although most systems will operate at 400 CFM per ton with no mechanical problems, that may not be the ideal airflow for your application.