Glove Cut Resistance Ratings

Did you know that gloves have ratings? When looking for a glove to protect your hands from cuts and scrapes you should get a pair that matches the required duty. There are actually two different glove ratings for cut resistance: ANSI/ISEA 105 and EN 388. In the United States we use ANSI/ISEA 105 which had a significant update in 2016.  There are nine levels, A1 – A9, with A9 being the most cut resistant. The gloves are tested by placing a fixed amount of pressure on a blade while moving it across the glove for a distance of 20 millimeters (roughly ¾ of an inch). The tool used is called a tomodynamometer which moves a razor blade slowly across the material being tested at a specified pressure for a specific length. The glove cut resistance levels are established based on the amount of pressure required to cut through the material. The Table below shows the nine levels in the ANSI system. You can see that the minimum recommended cut level for HVAC work is A4.

ANSI/ISEA 105 2016 Glove Cut Rating
Grade	Pressure Required to Cut Through	Recommended Use
A1	200-499 grams	General Purpose Material Handling
A2	500-999 grams	Packaging, paper handling
A3	1000 – 1499 grams	Handling construction materials
A4	1500 – 2199 grams	HVAC, duct work
A5	2200 – 2999 grams	HVAC, metal fabrication, metal stamping
A6	3000 – 3999 grams	HVAC, metal fabrication, metal stamping
A7	4000-4999 grams	HVAC, metal fabrication, glass manufacturing
A8	5000 – 5999 grams	HVAC, metal fabrication, glass manufacturing
A9	6000 or more grams	HVAC, metal fabrication, metal recycling

There is no requirement for glove manufacturers in the United States to test and label their gloves, so many gloves are sold without the cut rating. However, better manufacturers test and label their gloves. Look for gloves that have an ANSI/ISEA rating of at least A4 to protect your hands. To learn more, check out this page from Superior Glove Company.

Glove Rating Systems Explained

Replacing Wires Inside a Unit

Occasionally it is necessary to replace original factory wiring inside a unit. Sometimes critters have nibbled on them, sometimes the weather has degraded them, and sometimes the overheating or failure of a connected component has made the wire stiff and brittle. Whatever the reason, it is important to note that all wiring must meet the original manufacturer factory specification. Of course you should replace the original wire with the same material and gauge, but there is more to the specification than just the actual wire.

The wire insulation rating is just as important. For example, a wire from an NM-B cable should never be used to replace power wring inside a unit even though it might be the same material (copper) and gauge. The wiring inside most equipment is rated as machine tool wiring (MTW).  MTW insulation is a thermoplastic that is rated for up to 600 volts and is moisture, heat, and oil resistant. The insulation on NM-B cable is not moisture, heat, or oil resistant.

The wire insulation rating can be found printed or embossed on the wire. The figure below shows the marking.

Note that the wire gauge can be seen in the yellow circle and the insulation type, MTW or THHN, can be seen in the green circles. You should check to make sure any wiring you plan to use inside a unit meets the manufacturer’s original specification. This specification can often be found in the wiring diagram notes. A common note is that any replacement wiring must be rated for a temperature of 105°C. The insulation of NM-B cable is only rated for temperatures up to 60°C, and so should not be used inside the equipment cabinet.

Zero is NOT Nothing!

Many times people have remarked that even though they recovered a system to 0 psig or lower, when they opened the system, there still appeared to be some refrigerant. Often the presence of some refrigerant was most noticeable when they started brazing on a system that supposedly has nothing in it, and noxious green flames come out of the joint. This is because zero is not nothing. And no, that is not my “casual” grammar coming out. Don’t assume that because you have recovered a system down to 0 psig, or even into a vacuum, there is no refrigerant remaining. In fact, there can be quite bit of refrigerant in the compressor oil even under a vacuum. Since the refrigerant oil and the refrigerant are miscible, refrigerant dissolved in the refrigerant oil leaves the oil very slowly. The attached video shows refrigerant boiling out of oil removed from a compressor that was removed from a system which was recovered down to 28” of vacuum. The oil continued to boil for hours after being removed.



 This helps explain why system pressure can rise in a system which is left under a vacuum. This also explains why you should make sure the compressor oil sump heater(crankcase heater) is on before recovering refrigerant. If you are planning on recovering refrigerant from a system that has an operable compressor, run the system until the compressor is warm before beginning recovery. The compressor can draw out the refrigerant from the oil faster than your recovery machine. A heat gun applied to the bottom of the compressor can also help a great deal. While you are heating places that trap refrigerant, go ahead and heat the bottom of accumulators, receivers, and filter driers as well. A little time spent warming these areas trap oil and refrigerant will save time during recovery and evacuation. Remember, zero is not nothing!

New HCFO Refrigerants

We might be seeing refrigerants containing chlorine again sometime in the near future. Some of the new olefin based refrigerants contain chlorine but still manage to have almost no ozone depletion potential. These chemicals are hydrochlorofluoro-olefins, or HCFOs. Why are chemical manufacturers taking a new look at chemicals containing chlorine? In short, to produce chemicals that have a low global warming potential, are non-flammable, and work at pressures common to “normal” refrigeration systems. Hold on - what about ozone depletion? Turns out, eliminating chlorine is not the only way to make a refrigerant that will not deplete the ozone. Another way it to make a compound with a very short atmospheric life. The atmospheric life of HCFOs is measured in days instead of years. HCFO refrigerants break apart quickly in the atmosphere, before they are able to reach the stratosphere. This same characteristic also helps reduce the global warming potential of HCFO refrigerants. For example, HCFO-1224yd(Z) has an atmospheric life of 21 days and HCFO 1233zd(E) has an atmospheric life of 26 days. They also have nearly 0 ozone depletion potential; for example HCFO 1233zd(E) has an ODP of 0.00012, which is commonly reported as 0.  Both a GWP less than 1. In addition, both have an A1 safety rating and can be used with both POE or napthenic mineral oil. HCFO 1233zd(E) from Honeywell and HCFO 1224yd(Z) from AGC Asahi Glass are currently the only two HCFO refrigerants I know about. They are both for low pressure centrifugal chillers. One more characteristic of these new HCFO refrigerants - they are very expensive. Like, if you have to ask how much you can't afford it expensive. 

Bearing Failure Leads to Cooked Winding

I ran across a failed capacitor start motor on an air compressor recently. It is obvious that the start winding got barbecued (see picture).

A student asked me how I knew right off that it was the start winding.  Notice that the winding which is burned has smaller gauge wire than the winding that appears OK. The start winding in single phase motors is constructed of smaller gauge wire than the run winding and has fewer turns. It is tempting to call this an electrical failure after seeing the cooked winding. However, most motor failures can be traced back to bearing failures.

Disassembling the motor we saw that the rotor had been dragging – a sure sign of bearing failure. (see picture)

The lead end bearing was to blame in this case. You can see that the dragging all took place on the lead end of the motor. Taking a close look at the stator you can see where the rotor has been rubbing the stator. (see picture)

This can cause two types of winding failures: one where the rotor knocks some of the metal layers into the slots where the windings are, and another where the rotor stays magnetically locked down at startup, which is what I believe happened here. Even though the rotor turns easily by hand and there is no play that can be casually observed by hand, it is obvious the bearing was allowing the rotor to touch the stator. If this happens on startup, the reaction will be like two magnets with opposite polarity pulling together. The motor will lock down, draw high current, and heat up.

Toggle Switch Failure in a Crawl Space

A very common problem encountered in crawl spaces is for the toggle switch used as a furnace disconnect to die. Often you turn it off, and it will never turn on again. They can also fail on their own over time. Toggle switches are not really made for the environment found in most crawl spaces. The contacts and the switch mechanism get corroded. The contact corrosion causes voltage drop and heat, further degrading the switch. 

The picture shows what is left of the toggle switch that was serving as a furnace disconnect. The switch had failed, keeping power from reaching the furnace. It was relatively easy to diagnose: nothing happening with any thermostat setting, no transformer hum, and no LEDs glowing. My non-contact voltage detector showed power entering the switch but not leaving it. When I started to remove it so I could check it, it just fell apart.

To avoid similar problems, toggle switches in crawl spaces should be installed inside a weather proof switch box. I also recommend spending a few extra dollars to get a commercial, heavy duty toggle switch instead of the normal light duty residential toggle switch. In fact, the NEC requires the weatherproof box, but it is often overlooked. The relevant NEC sections are listed below. These are from the 2017 edition, but I do not think these particular sections have changed from previous code versions.

“404.4 Damp or Wet Locations

(A) Surface-Mounted Switch or Circuit Breaker. A surface mounted switch or circuit breaker shall be enclosed in a weatherproof enclosure or cabinet that complies with 312.2.

312.2 Damp and Wet Locations.

In damp or wet locations, surface-type enclosures within the scope of this article shall be placed or equipped so as to prevent moisture or water from entering and accumulating within the cabinet or cutout box, and shall be mounted so there is at least 6-mm (1∕4-in.) airspace between the enclosure and the wall or other supporting surface. Enclosures installed in wet locations shall be weatherproof. For enclosures in wet locations, raceways or cables entering above the level of uninsulated live parts shall use fittings listed for wet locations.

Exception: Nonmetallic enclosures shall be permitted to be installed without the airspace on a concrete, masonry, tile, or similar surface.”

Entropy, oh Entropy, What Art Thou?

Ok, so Shakespeare did not wax lyrical about entropy. I was talking with Bryan Orr the other day and the subject of entropy came up. Bryan does HVACR podcasts and organizes educational resources for HVACR. His website is hvacrschool.com. The quickest way to discover that you don’t really know everything you should about a subject is to try and explain it to someone else. In talking with Bryan, I realized my grasp on entropy was a bit tenuous.

Anyone looking carefully at a refrigerant pressure-enthalpy diagram might have noticed the steep, diagonal lines on the right side of the saturation curve labeled entropy. Entropy is a measure of the level of disorganization in something. Entropy is a natural process: everything tends to become less and less organized over time. The inside of most service technician’s trucks towards the end of the week is an example of increasing entropy. Parts and tools scattered about, service tickets and coffee cups in the dash, and a copy of Fundamentals of HVACR, 3rd edition open in the front seat. So how does this concept of increased randomness have anything to do with air conditioning?

In researching for an answer to that very question I came upon many explanations that were honestly a bit beyond me. It seems I am not the only person who struggles with exactly what entropy is. The definition that I found which came the closest to something which made sense from an HVACR point of view was “Entropy, the measure of a system's thermal energy per unit temperature that is unavailable for doing useful work. Because work is obtained from ordered molecular motion, the amount of entropy is also a measure of the molecular disorder, or randomness, of a system.” Another idea that helped was “Thermodynamic entropy is part of the science of heat energy. It is a measure of how organized or disorganized energy is in a system of atoms or molecules.” From these descriptions I can visualize that entropy is a measure of the amount of energy required to keep something at its present condition and state. That energy is unavailable for useful work because that amount of energy is required just for the substance to remain as it is.

If you think about the different physical states and the way molecules are arranged, you can see that solids have a low entropy – the molecules have very few possible arrangements, liquids have a higher entropy – the molecules move freely around, and gasses have the highest entropy – the molecules are whizzing around nearly independently. Extending the mental concept a bit further, increasing the temperature of a gas increases the entropy because now the molecules are moving more, so there are more possible arrangements. On the other hand, increasing the pressure of a gas decreases its entropy because the molecules are packed in more tightly, decreasing their ability to move around. Increasing the volume of a gas increases the entropy because the molecules have more room to play, and thus, more arrangements.

OK, so we still have not really nailed down how this has anything practical to do with a refrigeration system. Entropy is measured in BTU per pound per degree. Basically, that is the definition of specific heat. Notice that if you follow any line of constant entropy from left to right, the gas increases in temperature and pressure. That is exactly what happens in a compressor. These two changes counteract each other in terms of the effect they have on entropy, leaving entropy unchanged. When gas is compressed its entropy remains the same. Mechanical energy is converted into heat energy, but the amount of heat per degree for each pound of refrigerant stays the same.

Next time you are on a job and want to plot the system operation on an enthalpy diagram, remember that you can use the lines of constant entropy to make it a bit easier. The compressor line starts where the evaporator pressure line intersects the suction temperature line. Compression will follow the lines of constant entropy up until you intersect with the condenser pressure line.      

Court Rules Against EPA SNAP Ruling

Two refrigerant manufacturers, Mexichem and Arkema, have successfully sued the EPA over their decision to start phasing out HFC refrigerants because of their global warming effect. The gist of the argument is that the law which established the EPA’s right to regulate refrigerants is specifically about ozone depletion, not global warming. The EPA’s legal right to regulate replacement refrigerants is limited to their effect on ozone depletion. The court ordered the EPA to redo their ruling with this in mind. Below are a couple of direct quotes from the ruling.

“The fundamental problem for EPA is that HFCs are not ozone-depleting substances, as all parties agree. Because HFCs are not ozone-depleting substances, Section 612 would not seem to grant EPA authority to require replacement of HFCs. Indeed, before 2015, EPA itself maintained that Section 612 did not grant authority to require replacement of nonozone-depleting substances such as HFCs.”

“EPA’s novel reading of Section 612 is inconsistent with the statute as written. Section 612 does not require (or give EPA authority to require) manufacturers to replace non-ozone depleting substances such as HFCs. We therefore vacate the 2015 Rule to the extent it requires manufacturers to replace HFCs, and we remand to EPA for further proceedings consistent with this opinion.”

The EPA still has to do their rewrite, and of course it is possible that they might choose to appeal to the supreme court. But for now, the HFC phase down has been phased out.

You can download the ruling and read it for yourself here:

https://www.cadc.uscourts.gov/internet/opinions.nsf/3EDC3D4817D618CF8525817600508EF4/$file/15-1328-1687707.pdf

Below are two links to other articles about this ruling.

http://r744.com/articles/7787/u_s_court_rules_hfcs_cannot_be_limited_by_current_epa_rules?utm_source=mailchimp&utm_medium=email&utm_campaign=Bi-weekly+Newsletter

http://cen.acs.org/articles/95/web/2017/08/Court-strikes-down-US-restrictions-on-HFCs.html

Stay Away from Unapproved Flammable R22 Substitutes

At the risk of sounding like a broken record, I am once again talking about the dangers of unapproved, highly flammable R22 substitute refrigerants which are still easily available over the internet to anyone who wants to buy them. A quick Google search for R22 replacement refrigerant will list several places to buy these dangerous mixtures. The manufacturers market these under a variety of names. The EPA has listed many of them as specifically NOT approved for use. They include refrigerant products sold under the names R-22a, 22a, Blue Sky 22a refrigerant, Coolant Express 22a, DURACOOL-22a, EC-22, Ecofreeez EF- 22a, Envirosafe 22a, ES-22a, Frost 22a, HC-22a, Maxi-Fridge, MX-22a, Oz-Chill 22a, Priority Cool, and RED TEK 22a. The main component of all of these is propane.
 
It is true that the EPA has approved some flammable refrigerants for use in new systems with  lot of restrictions. However, the allowed use is for small refrigerators. The total allowable amount is very small, the systems must be new and specifically designed for flammable refrigerant. Refrigeration systems designed for flammable refrigerant meet strict safety standards, including non-sparking controls and labeling.  Class 3 flammable refrigerants are specifically NOT approved for use as a retrofit refrigerant for R22, or any other system designed for non-flammable refrigerant.

Every time a contactor or relay opens or closes they make a spark which is hot enough to ignite a flammable gas. If someone is losing refrigerant, their system has a leak. Continuing to add a flammable refrigerant on top of R22 will eventually create a flammable mixture. More worrying is that the flammable mixture will be leaking out somewhere.

As a practical matter, most recovery units are not designed to handle flammable refrigerants. Master Cool has just come out with one that is  specifically designed to safely handle flammable refrigerant. Even if you did not use any flammable refrigerant, are you certain that someone before did not add one of these flammable substitutes?

Here is a copy of some of the text from the EPA ruling

“ For retrofit residential and light commercial AC and heat pumps— unitary split AC systems and heat pumps, EPA is listing as unacceptable, as of January 3, 2017:
• All refrigerants identified as flammability Class 3 in American National Standards Institute (ANSI)/ American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) Standard 34–2013; and
• All refrigerants meeting the criteria for flammability Class 3 in ANSI/ ASHRAE Standard 34–2013. These include, but are not limited to, refrigerant products sold under the names R-22a, 22a, Blue Sky 22a refrigerant, Coolant Express 22a, DURACOOL-22a, EC-22, Ecofreeez EF- 22a, Envirosafe 22a, ES-22a, Frost 22a, HC-22a, Maxi-Fridge, MX-22a, Oz-Chill 22a, Priority Cool, and RED TEK 22a. “

Here is a link to the EPA ruling banning flammable refrigerant as a retrofit refrigerant. https://www.gpo.gov/fdsys/pkg/FR-2016-12-01/pdf/2016-25167.pdf

Alphabet Soup

Daikin just announced the release of R407H and the US EPA has added it to their SNAP list of acceptable refrigerants for both new and retrofit uses. 407H is designed to be a lower GWP refrigerant to replace R404A and R22 in commercial refrigeration applications. I confess, I did not know there was a 407G. I am often asked where all these numbers and letters come from.

The numbers for refrigerants which are mixtures of two or more refrigerants start with either a 4 or a 5. All zeotropic refrigerant numbers start with a 4 while azeotropic refrigerants numbers start with a 5. Zeotropic refrigerants separate when boiling; azeotropic refrigerants do not separate when boiling. The number after the 4 indicates the order that mixture of chemicals was tested by ASHRAE. For example, R401A was the very first. The letter after a zetropic refrigerant designates the order of testing for that specific mix of chemicals. For example, 407A was the first mixture of R32, R125, and R134a to be tested while 407H is the eighth. Please note that the letters for 400 series refrigerants should be upper case.

So what is the difference between 407A, 407C, 407H, and all the other 407 refrigerants? Just the percentage mix of the three ingredients. All eight versions of 407 have slightly different mixtures of the same three constituent refrigerants. A lot of this is done to tweak performance for a specific application or improve a particular characteristic, such as lowering the refrigerant’s GWP. 407H has a GWP of 1500 compared to 404A of 3922.

So what about the other refrigerant numbers, such as 22, or 134a, or (gasp) 1234yf? These describe the chemical construction of the molecules in these refrigerants. These refrigerants all consist of just one chemical compound. Compounds such as R12 or R22 are simple enough to be described without a trailing letter because there is only one way to build them. On the other hand, refrigerants 134a and 1234yf can be built many ways because they have more than one carbon atom. The trailing letters describe how the atom is constructed, which makes a difference in how it behaves. Note that these letters are lower case.

Flammable Refrigernats

I confess that I have always thought of flammability as an either or question: it either burns or it doesn’t. So the concept of different levels of flammability was a hard one for me to grasp. I wondered: what is the difference between 3,2, and 2L refrigerant designations? What follows is a somewhat lengthy discussion of what I learned.

First off,  found that it is not all that simple. There are several flammability characteristics that can be compared: lower flammability limit, upper flammability limit, auto ignition temperature, minimum ignition energy, heat of combustion, and flame velocity. The table at the bottom of the article shows these different specifications for a small selection of flammable refrigerants. Note that pressure and temperature also play a part. For the ASHRAE safety tests, a temperature of 140°F at atmospheric pressure is specified. You get different results when applying higher pressures and temperatures.

The original three classifications (1,2,3) were determined by the lower flammability limit and the heat of combustion. A refrigerant is classified as highly flammable, Class 3, if  either it requires 3.5% or less less by volume for a flammable mixture or it has a heat of combustion equal to or exceeding 19 kilojoules per gram. Note that EITHER condition will place it in class 3. Class 2 refrigerants require a concentration greater than 3.5% by volume to create a flammable mixture and they must have a heat of combustion less than 19 kilojoules per gram. Note that BOTH conditions must be met in order to be classified as class 2. Later, ASHRAE added a 2L category for refrigerants with burning velocities less than 10 centimeters per second. The table below summarizes the different flammability classifications.

Classification	Lower Flammability Limit % by volume	Heat of Combustion	Burning Velocity
1	Does not support combustion at atmospheric pressure
2L	Greater than 3.5%	Less than 19 kj/g	10 cm/s or less
2	Greater than 3.5%	Less than 19 kj/g	Greater than 10 cm/s
3	3.5% or less	19 kj/g or more	NA

Lower flammability limit (LFL) is the minimum percentage required in air to be combustible. For example propane (R290) has an LFL of 2.1% by volume while ammonia (R717) has an LFL of 15%. Notice that propane only requires 2.1% while ammonia requires 15%. So that is one difference – the amount that must build up before it can burn.

Upper flammability limit (UFL) describes the maximum concentration which will still burn. If the concentration of flammable vapors exceeds the UFL, it will not ignite. It is more difficult to draw a straight line comparison using the UFL. However, you can say that refrigerants whose LFL and UFL are closer together are generally a bit safer simply because the conditions dor a flammable mixture are less likely to occur.

Auto ignition temperature is the lowest temperature at which it spontaneously ignites in normal atmosphere without an external source of ignition. With the exception of 1234yf, the lower flammability refrigerants have higher auto ignition temperatures than the more flammable refrigerants.

Minimum ignition energy is a bit different than the auto ignition temperature. It is the minimum amount of energy required to ignite a flammable mixture, measured in megajoules. Note that in this case R1234yf stands out because the minimum ignition energy is so high compared to the other refrigerants. Also note that the class 2L refrigerants all have minimum ignition energy ratings in the hundreds of megajoules or higher while propane’s minimum ignition energy is a very small 0.25 megajoules. Basically, this means it takes a lot more energy to ignite the 2L refrigerants than a highly flammable refrigerant such as propane. Again, this means that the chance of having the right condition for combustion is much lower for class 2L refrigerants.

Heat of combustion is a measure of the amount of heat created when the refrigerant burns. Note that the class 2L and class 2 refrigerants have a heat of combustion in the single digits per gram while propane jumps to 46 kilojoules per gram. This means that the heat produced by combustion of a class 2L or class 2 refrigerant is far less than a class 3 refrigerant. Indeed, it would be possible for a class 2L refrigerant to burn and not ignite other nearby flammable materials.

Burning velocity is the characteristic which distinguishes 2 and 2L refrigerants. It is the speed with which the flame advances. Note that the 2L class refrigerants have a burning velocity in the single digits while 152a, a class 2 refrigerant, has a BV of 23 cm/sec. Propane’s burning velocity is twice that of 152a. The take home point here is that the flames from higher flammability refrigerants spread faster.

So wrapping it up, my general impression is that lower flammability refrigerants are less likely to burn in the first place and when they do burn, the flames are not as hot and do not spread as quickly as a high flammability refrigerant such as propane.

  

Refrigerant	R1234yf	R32	717 Ammonia	152a	290 Propane
Safety Group	A2L	A2L	B2L	A2	A3
Lower Flammability LImit	6.5%	14.4%	15%	3.9%	2.1%
Upper Flammability Limit	12.3%	33.3%	28%	16.9%	10%
Auto Ignition Temperature	405°C	648°C	651°C	440°C	455°C
Minimum Ignition Energy	5,000 – 10,000 mJ	30 – 100 mJ	100 – 300 mJ	0.38 mJ	0.25 mJ
Heat of Combustion	9.5 kJ/g	9 kJ/g	22.5 kJ/g	6.3 kJ/g	46.3 kj/g
Burning Velocity	1.5 cm/sec	6.7 cm/sec	7.2 cm/sec	23 cm/sec	46 cm/sec

Measuring System Airflow Using a Ductblaster

If you install systems in a state which requires duct leakage tests on all new installations, chances are you have a ductblaster which you use for that purpose. Your ductblaster is more accurate at measuring airflow than just about any tool you have. Afterall, the way it works is to pressurize the ductwork and measure the airflow required to maintain that pressure. You can use the ductblaster to measure system airflow using a procedure called pressure matching.

Operate the air conditioning system normally and use the ductblster manometer to measure the static pressure in the supply plenum or trunk. You should measure after the coil but before any takeoffs. Record this pressure. Now, turn the system off and connect the ductblaster to the blower on the return side. You will need to block the return air trunk off so air only goes through the unit and into the supply ducts.

Now turn on the ductblaster. Once again, measure the supply air static at the same location where you measured it with the unit operating.  Dial the ductblaster up until the measured supply air static equals the reading you took when operating the system. The amount of airflow the ductblaster is moving is the same as the airflow through the system when it was operating.

How does this work? You are matching the airflow required to create a supply static equal to the supply static created by the system blower. Note that this does not require any particular manufacturer’s data. This procedure allows you to make an accurate airflow measurement using a tool you may already have. It also allows you to get more from your investment in the ductblaster.

Refrigerant Don'ts

With summer now upon us and the price of R22 skyrocketing there are many questions regarding replacement refrigerants. This discussion could fill a book, so I am going to restrict this post to a list of don'ts. The intent is to help people avoid issues that can be caused by improper application of 400 series R22 replacements.

Do NOT use a flammable replacement refrigerant in ANY system originally designed for R22. There are some hydrocarbon (propane) based replacement refrigerants sold online. They are NOT EPA approved and represent an explosive hazard when charged into a system that was not designed for flammable refrigerant.

Do NOT add ANY replacement refrigerant on top of an existing R22 charge. This is an EPA violation. You are essentially creating a “new” refrigerant which has not been tested or approved. There are NO replacement refrigerants which are legal to add in on top of an existing R22 charge. You must first remove ALL of the R22 when doing a conversion.

Do NOT use ANY 400 series refrigerant in a flooded system. Even refrigerants which are advertised to work in systems with mineral oil will still separate in the flooded portions of the system because they are not truly miscible. There is a difference between miscibility and solubility, but that is the subject for another whole article.

Do NOT use ANY replacement refrigerants in ANY system using an electronic expansion valve. This would primarily be older R22 minisplits, multisplits, and VRF systems. Trane hyperion heat pumps can sometimes have an R22 charge. In that specific case, the indoor air handler is designed for both R22 or R410A, so switching to R410A and changing the refrigerant dip switch solves that problem for the indoor air handler. Unfortunately, you will still have to replace the outdoor unit with one designed for R410A.

Do NOT use ANY 400 series replacement refrigerant in systems which were originally designed for R22 and have Trane 3D Scroll compressors. The lubrication system that specific compressor design uses does not work well with HFC refrigerants, including ones advertised as being compatible with mineral oil.

This all come down to one main strategy for replacing R22 in most older systems: it is generally best to replace the whole system. Not only does this avoid application problems, it usually provides a significant efficiency upgrade as well.

Latent Cooling and Variable Capacity Systems

If you live anywhere other than the southwestern part of the US, you probably need latent cooling in the summer. The word latent means hidden. Cooling capacity is required to condenses water on the evaporator coil. This is referred to as latent cooling because there is no temperature change involved, you can’t sense, or measure the heat change using temperature, but cooling capacity is required. Two things help increase latent cooling: long run times and reduced airflow across the evaporator. These increase the percentage of system capacity used for latent cooling.

I have a brand new communicating, 20 SEER system with a variable speed scroll and an ECM indoor blower motor. One fun thing about the thermostat is that it reports the compressor speed and the furnace reports the blower CFM. I have been watching both.

The compressor is most often operating less than 50% capacity, but stays running most of the day once it starts. This ability to match system capacity to the load makes for long run times, which helps control humidity. It does not use more power, even though it is running a lot because it is using much less electricity while it is operating.

I have noticed that the fan almost never runs at the traditional 400 CFM per ton. For example, on one occasion I found the compressor running at 96% while the fan was moving 1230 CFM. It is a 4 ton system, so traditional CFM math would place the “normal” airflow at 1536  (4 x 0.96 x 400 = 1536). However, the system was operating at only 320 CFM per ton ( 1230 / (4 x 0.96)).

The thermostat also lets you set the indoor relative humidity and reports the indoor relative humidity. I set it at a fairly low 45% and the system has kept it between 45% and 50%. During the day when the system is running, it keeps it right at 45%. It accomplishes this by using long run times at reduced capacity with lower than normal airflow. Summer comfort in the southeast involves more than controlling temperature, it also involves controlling humidity. One bonus of the variable capacity systems is that they do a better job of controlling humidity than fixed capacity systems.

Motor Rotation

Many single phase motors can only turn in one direction. For example, pump motors and fan motors. Since the pumps and fans they operate only work in one direction, the motors that drive them re usually built for one direction.  This can pose a problem for service techs when replacing these motors. Often, service motors solve this problem by being reversible. However, OEM replacement motors are generally not reversible, so you must specify the correct motor rotation. To do this you need to understand the terminology that is used to describe motor direction.

There are only two possible rotations: clockwise and counter-clockwise. However, there are also two perspectives: looking at the shaft end of the motor or looking at the lead end (opposite the shaft end). A motor which turns clockwise looking at the shaft end is turning counter-clockwise when viewed from the lead end! The point is that just stating a direction is not good enough. You must also identify a perspective.

There are several names for the two possible perspectives. The most common are shaft end and lead end. The shaft end can also be called the output end, drives end, or pulley end. The lead end is sometimes referred to by placing “opposite” in front of whatever phrase is used to describe the shaft end; such as, “opposite drive end.”

Normally these descriptions are abbreviated, which tends to add to the confusion. Below is  list of some of the abbreviation used. The graphic above each group uses an arrow to show the rotation looking at the motor shaft.

CCWSE Counterclockwise shaft end
CCWOE Counterclockwise output end
CCWDE Counterclockwise drive end
CCWPE Counterclockwise pulley end
CWLE   Clockwise lead end


CWSE  Clockwise  shaft end
CWOE Clockwise output end
CWDE Clockwise drive end
CWPE Clockwise pulley end
CCWLE Counterclockwise lead end

Clockwise and Counter-Clockwise

Many folks have heard the phrase “righty tighty, lefty loosey.” This little limerick is a clever way of remembering which way traditional right-handed threads turn. However, it can be misleading. The right or left direction refers to the direction the top of the circle will turn. But the bottom of the circle turns in the opposite direction. So while the top is being turned to the right, the bottom is being turned to the left.

CLOCKWISE

COUNTER-CLOCKWISE

I really prefer the terms clockwise and counter-clockwise to describe rotational movement because you don’t have to be concerned if you’ re looking at the top of the circle or the bottom. You only have to remember which way a clock hand moves. Therein lies the problem. In today’s digital age, some people can’t tell you which way a clock hand moves because they rarely see one.

Every program should have an operating analog clock in the class room so students can learn the difference between clockwise and counterclockwise. Notice how the numbers on the clock face progress from the top to the right, creating clockwise motion. Logically, counter-clockwise motion is the opposite.

LEFT HAND THREAD ON ACETYLENE HOSE

This little saying also ignores the left handed threads, which are exactly backwards from right-hand threads. Although far less common, left hand threads are often found on connections for flammable gas, such as the regulators and hoses used for Acetylene on an oxy-acetylene torch. In that case it is “righty loose, lefty tighty.” Doesn’t have quite the same ring to it. Left hand threads on torches have a hash mark on them to indicate that they are left-hand threads. The acetylene and oxygen have opposite threads for a reason – to prevent mixing up the regulators and hoses. Mixing the gasses under pressure can create a combustible mixture.

Intelligent Controls Improve System Charging

"Charge View" by Johnson Controls

Units with intelligent boards that assist in system charging are available. Many VRF systems can assist technicians in charging the unit. They are so complex that some type of automated assistance is really necessary. With multiple heads and variable capacity compressors there is really no way to use system pressures to determine the correct charge. Computer assistance is available through installation and charging applications that run on laptop computers, to evacuation and charging modes built into the system controls.

Trane introduced split system units with “Charge-Assist” back in 2008 in their Xli line. These systems have pressure transducers and temperature thermistors which are used to operate the electronic expansion valves in the unit. The board can also use the input from these sensors to determine if the system charge is correct. An external  “Charge Assist” solenoid can be controlled by the board to allow the unit to charge itself. On these units, the technician only sees a blinking LED on the unit control board.

Johnson Controls (York, Coleman, Luxaire) are now offering units with built in pressure and temperature monitors and a screen to display system pressures, liquid line temperature, suction line temperature, superheat, and subcooling. The system will also tell you if it is correctly charged. It is like having a digital gauge set built into the unit. The main point is that you can check the unit charge without attaching any gauges or temperature probes. That means you will not lose any refrigerant while checking the charge.

These examples represent only the very high end systems from a few different manufacturers, but I believe it shows the direction the industry is headed. Systems will have sensors and intelligent controls monitoring system operation. I am sure that as the technology matures, its cost will come down, making this technology attractive to other manufacturers and in more main line units. Another driving force will be the desire to insure actual equipment performance and efficiency match the design. The most efficient system available installed incorrectly may perform worse than the lowest builder grade equipment available. Designing intelligent controls into a system is a way to improve system installation and service by taking guesswork out of charging. With systems employing these intelligent controls you really have no excuse for leaving the unit improperly charged.

Measure System Capacity and Efficiency

System tune-up time is here. Imagine if you could give your customers a report that shows the system capacity and efficiency before and after your system tune-up! There is a tool that can do that, the iManifold. It not only can measure system characteristics such as pressure, temperature, superheat, and subcooling; it can use the measurements to determine BTUs/hr capacity and system EER. To be sure, you need a few other measurements; namely, dry bulb and wet bulb in and out of the evaporator as well as system operating voltage and current. The iManifold with the correct accessories can measure the characteristics necessary to do system capacity and efficiency calculations and perform the calculations. It can also produce reports showing the details, including system capacity and efficiency. The report can be printed or e-mailed to the customer. The only “report” most customers get now after a traditional system tune-up is a bill. The iManifold and iConnect are the only tools I know of that can do this.

What accessories do you need? You also need two wireless temperature/humidity probes made to work with the iManifold and an electric meter that can communicate with the iManifold. The iManifold and the necessary accessories required to measure system capacity and efficiency are definitely more expensive than many other digital gauges. However, the iManifold does things other digital gauges cannot do.

To learn more about the iManifold chaeck out their web site imanifold.com

Don't Make the Problem Worse

There is a saying that if the only tool you have is a hammer, every problem looks like a nail. Many inexperienced techs make the mistake of trying to fix everything using the handful of procedures they are familiar with.

The most common “fix” applied to many systems is to add refrigerant. If a system is operating with low pressures or freezing up, many techs will add some refrigerant. Homeowners often actually ask for techs to add refrigerant, thinking that more refrigerant must mean colder air. However, adding refrigerant may not actually fix the problem. In fact, often it may make things worse.

For example, if a system has low airflow it will have low pressures, and often will freeze up. The reduced load will cause low superheat and refrigerant floodback. Adding refrigerant just makes the floodback worse, shortening the compressor life. An undercharged system would have a high superheat. You should always check the system airflow, superheat, and subcooling before adding refrigerant.

Another common example is a system with a refrigerant restriction, such as a plugged up filter drier. Again, both pressures will be low, and BOTH the superheat and subcooling will be high. This can look similar to an undercharge, except for the subcooling. An undercharged system will have a low subcooling. Adding refrigerant fills up the condenser, raising both the high side pressure and the already high subcooling. It may marginally improve the low side pressure and capacity. However, it forces the system to run at an excessive compression ratio and uses lots of power trying to force the refrigerant through the restriction. A far better solution is to remove the restriction.

Finally, a clogged or stuck expansion valve behaves like a refrigerant restriction. Failed expansion valves used to be quite rare. Unfortunately, they are pretty common today. Between the valves that were fouled up because of the compressor manufacturing problem and the valves that become clogged with black copper oxides, failed expansion valves have become all too common. The symptoms are identical to a refrigerant restriction: low pressures, high superheat, and normal to high subcooling. If someone has already tried to “fix” the problem by adding refrigerant, then the high side pressure may be high and the subcooling will be very high.

Please don’t make the problem worse. Before adding refrigerant to a system with low pressures, first check: airflow, superheat, and subcooling. A truly undercharged system will have adequate airflow, a high superheat, and a low subcooling. And if the system is undercharged, then maybe you should try to figure out why.