Friday, August 11, 2017

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

Saturday, July 29, 2017

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

Monday, July 24, 2017

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.

Saturday, July 15, 2017

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.
  
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

Saturday, June 24, 2017

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.

Friday, June 16, 2017

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.

Wednesday, June 7, 2017

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.