Saturday, December 3, 2016

Cranking Out The Rules

 With only weeks left in the Obama administration, federal agencies such as the Energy Efficiency and Renewable Energy Office (EERE) are finishing up work on a number of initiatives and publishing final rulings. Who are the EERE? They are a subset of the Department of Energy (DOE). These rulings have an impact on the HVACR industry. While the rulings do not have a direct effect on technicians in the field, they have a big effect on HVACR manufacturers. Indirectly they will affect us as manufacturers respond to the directives. Most of the rulings have to do with how different equipment is tested by the manufacturer, and in some cases, what equipment is covered.  Here is a list of recent rulings with links for more information.

12/02/2016 DOE Issues a Notice of Final Rule Pertaining to Test Procedures for Walk-in Coolers and Walk-in Freezers

12/01/2016 DOE Issues a Notice of Final Rule Pertaining to Test Procedures for Compressors

11/30/2016 DOE Issues a Final Rule Pertaining to Test Procedures for Central Air Conditioners and Heat Pumps

11/21/2016 DOE Issues a Comment Period Extension Pertaining to Energy Conservation Standards for Residential Furnaces

 11/15/2016 DOE Publishes a Final Determination of Compressors as Covered Equipment

11/10/2016 DOE Publishes a Final Rule Pertaining to Test Procedures for Commercial Packaged Boilers

10/07/2016 DOE Issues a Final Determination Pertaining to Energy Conservation Standards for Direct Heating Equipment  

10/04/2016 DOE Issues a Direct Final Rule Pertaining to Energy Conservation Standards for Miscellaneous Refrigeration Products

Tuesday, November 22, 2016

Check Combustion Air

With the weather getting cooler, I thought that now would be a good time to talk about combustion air. Don’t forget to check for proper combustion air. Most codes provide detailed drawings illustrating where combustion air should come from and how much you need, but there are still many furnace installations that rely entirely on air from inside the building for combustion air. In days gone by this was often considered adequate so long as the furnace was located in a large enough space. In newer homes, combustion air should always be provided.

Most 90%  furnaces today can operate using sealed combustion. In the case of a sealed combustion furnace, the combustion air is being piped in from the outside. The combustion air is piped directly into the furnace. These are easy to spot, they have two pipes: one for combustion air and one for the vent. Also, their panels have no louvers for combustion air. 

Traditional furnaces get their combustion air from the space where they are installed. Combustion air enters through louvers in their panels.Since the furnace is drawing air from the space it is in, fresh combustion air must be supplied to the room to keep the process going. Failure to supply the correct amount of combustion air can lead to negative room pressure, vent spillage, poor combustion, and CO production. All these things together can be disastrous.

When a technician checks a furnace that does not have sealed combustion, one of the first things to look for is how the furnace receives combustion air. If the furnace is in a ventilated crawlspace or attic, the ventilation for those spaces provides the combustion air. However, even these can be a problem. A large furnace in a small crawl space may not have adequate combustion air if the crawl space vents are closed. I have also seen crawlspace vents clogged with debris, effectively reducing the combustion air.  

The most troublesome installations are furnaces located inside the house in a closet. They should have a combustion air vent near the floor and another near the ceiling. Someone asked me about a furnace installed in a closet off of a bathroom. When they turn on the bathroom vent fan, they can smell gas! Another story involved a fireplace and a furnace. When the furnace came on it sucked the smoke out of the fireplace into the room. These types of stories indicate that the furnace does not have adequate combustion air. 

What if there are no obvious combustion air vents? Sometimes the vents were never provided, other times they have been covered up. I have seen combustion air vents covered with tape or plastic. Undoubtedly, someone noticed cold air coming in the vent and “fixed” the problem – thereby creating a combustion air problem. Occasionally insulation covers the grille into the attic. Another problem is using the furnace closet for storage. This is dangerous in and of itself, but it can also cause combustion air problems if boxes are stacked in front of the combustion air grilles.  For details on combustion air requirements check your local code. Unit 53 Gas Furnace Installation in Fundamentals of HVACR, 3rd ed also has detailed drawings and specifications for the most common applications.  

Saturday, November 12, 2016

Veterans Have the Right Stuff

On this Veteran’s Day I would like to suggest a way that the HVACR Industry can help those who served their country: offer them jobs. Veterans have many characteristics that make them ideal employees.

Veterans are disciplined.
Veterans have developed both self discipline and group discipline – both crucial skills for employment.

Veterans know how to work hard.
Remember, they made it through boot camp and survived years of living conditions most of us would find intolerable, all the while performing their job.

Veterans know how to be a team player.
The armed forces cannot function if everyone is freelancing. Installation is so much easier if you have a good team. Far more efficient than working alone.

Veterans can master technically difficult machinery.
Take a look at the equipment today’s armed forces work with. Much of it is incredibly complex. A veteran is someone who has been in a position where their life depended upon knowing how to operate that machinery.

Today, finding people who are good candidates for employment in the trades can be tough. Veterans already have the traits employers look for in a good employee, and that is a good base to build on. If the industry will reach out to veterans we will also help ourselves.

Here are links for people considering hiring a veteran or for veterans looking for help getting started in HVACR.

Troops to Trades 
Nexstar Legacy

Sunday, November 6, 2016

Digital Data Recording and Reporting

A relatively new class of communicating digital tools makes it possible to share your readings electronically. They not only take accurate pressure and temperature readings, they can share those in an email with your supervisor, company, customer or energy utility. And many of these can take more than just refrigerant pressure and temperature readings. The Stride I-Manifold, Testo Smart Probes, Fieldpiece System Analyzer, Sporlan Smart Tools, Yellow Jacket Mantooth, and Appion ION gauges can all send data to your electronic devices, which then use free applications to create and send the reports. Some can collect information from a variety of instruments and report on them as well. For example, you can also get ambient temperature, indoor wet bulb, and indoor airflow. I am sure I probably missed a few.  The point is, tools are available now that can do more than collect data; they can help you organize it and report your results.

The reporting capability allows you to document what you have done. For example, you can produce before and after reports showing the system performance when you arrived and the system performance after you have made adjustments. You can also send reports to your supervisors if you need help. Some utilities have rebate programs which require that the contractor use a particular reporting setup. The idea is that the utility can verify that the system really is performing as designed by the manufacturer.

This is both exciting and a little bit intimidating. Until now, if you went on a call and checked the system performance, you were generally the only person that would see all the measurements and make the judgement. If you have checked more than a handful of systems, you know that checking system performance really is a judgement based on a lot of variables. And, you only have control of a few of those variables. It is not as simple as matching a couple of pressures and temperatures.

There is the outdoor temperature, the indoor temperature, the indoor wet bulb, the airflow across each coil; any one of which can make your system perform in a way you don’t expect. That is before issues such as plugged expansion valves, restricted filter driers, underperforming compressors, or installation errors. All of these things must be verified before adjusting the charge. It would be nice if we could just state a couple of pressures and/or temperatures and leave it at that, but that is not reality. Even manufacturer performance charts and tables assume a lot of this information. If just one value is off from the assumption, the manufacturer’s chart will not work.

So, if you ever needed any incentive to up your game when checking systems, having to send reports to supervisors, utilities, and customers should do the trick. Beer-can cold is just not good enough in an environment that expects documentation and verification. That is unless you plan to strap a can of Coors to the suction line and send in a photo of the color change. Here are a few links to check out these new-age tools.

Appion - http://www.appioninc.com/products/ptgauges.html
Fieldpiece - http://www.fieldpiece.com/products/detail/sman460-wireless-4-port-digital-manifold-with-micron-gauge/system-analyzers/
I-Manifold - http://imanifold.com/
Sporlan - https://sporlanonline.com/smart/
Testo - http://www.testo.us/smartprobes/index.jsp
Yellow Jacket - http://yellowjacket.com/product/mantooth-dual-pressure-wireless-digital-pt-gauge/

Friday, October 28, 2016

What is an HFO?

Hydrofluoroolefins, HFOs, are a relatively new class of low global warming potential refrigerants. They are actually composed of the same chemicals found in an HFC: hydrogen, fluorine, and carbon. If you define an HFC as a chemical containing those three elements, then HFOs are actually HFCs. The difference is in how they are constructed.
Ethane
HFC 134a
 Both HFCs and HFOs start out as a hydrocarbon, containing a chain of carbon atoms surrounded by hydrogen atoms. To make a traditional HFC you replace some of the hydrogen atoms with fluorine atoms. Standard hydrocarbon molecules and traditional HFC molecules are composed exclusively of single atomic bonds. You can think of an atomic bond as a type of Velcro strip holding the atoms together. Carbon has four atomic Velcro strips while hydrogen and fluorine just have one. Single bonds just attach one strip between atoms. Using only single bonds a carbon atom will connect to four other atoms because it has four bonds. Molecules constructed this way are called saturated. They have the maximum number of atoms joined together.
Propane


HFO 1234yf
What makes HFOs different is that they use a double bond between two carbon atoms. These two caron atoms are connected together with two Velcro strips instead of just one. Since carbon atoms only have four connections, using two to connect to each other means that each carbon can only connect to two other atoms besides each other. This reduces the total number of atoms that can be connected together. This type of molecular construction is called unsaturated.

Why does this make a difference? Unsaturated molecules are far less chemically stable and tend to break down easier. Since HFOs are less chemically stable, they do not survive long in the atmosphere – and so they do far less harm than the more stable saturated HFCs. The difference is dramatic. HFC 134a has a GWP of 1430 while HFO-1234yf has a GWP of 4.

However, HFOs have a design challenge to overcome: they are mildly flammable. The very instability that reduces their GWP increases their flammability. At present, building codes in the US generally do not recognize a difference between highly flammable refrigerants and mildly flammable ones. Most building codes do not allow the use of significant amounts of flammable refrigerant inside the building. ASHRAE is working on revising their Safety Standard for Refrigeration Systems,  Standard 15. It is projected to be ready by January 2018. For more information on the work being done on flammable refrigerants check out this article in Contracting Business
http://contractingbusiness.com/refrigeration/codes-preparing-technology-refrigerant-changes

Saturday, October 15, 2016

Personal Gas Safety

Time for furnace tune-ups is here. Soon you will be taking the first no-heat calls of this heating season. No doubt you will be inspecting equipment for safety concerns that affect the customer. Don’t forget to pay attention to your own personal safety. Gas leaks, leaky vent systems, incorrect combustion, and lack of combustion air can all create immediate hazards to the service tech working on the system. There are pro-active steps you can take to stay safe while working on gas fired equipment.

Gas Leaks
If there are existing gas leaks it is possible that a combustible atmosphere exists in the space. Ideally, you want to check the air in the space for combustible gas before entering. You can use an electronic combustible gas detector for this. Many techs now use these to check for gas leaks, so you might already have the tool. Just turn it on and let it sample the air in the room as you enter. There are also personal detectors which you can wear to monitor the conditions wherever you are. If you do detect combustible gas in the room, do NOT turn on or off any electrical switches and leave the room. Shut off the gas outside and ventilate the room before continuing. You will have to turn the gas back on to find the leak, but you can ventilate the room and start with a safe atmosphere while you are doing it.

Carbon Monoxide
Negative room pressure, incorrect or leaky gas venting, and lack of combustion air can all contribute to a build-up of carbon monoxide in the room. You can’t smell or see carbon monoxide, so it is especially dangerous. Again, you should test the atmosphere in the room. There are electronic detectors made to check for carbon monoxide in the air, and some are made to wear to monitor the air continuously. If the monitor indicates a build-up of CO in the room, you should shut off the gas outside the room and ventilate the room. Once the room is cleared of CO you can start to look for the cause. Before turning the gas back on make sure to check for obvious things such as blocked combustion air intakes or compromised gas vents. After restarting the furnace you should check the flame color and test the flue for proper operation. Also be sure to check the flue gasses for CO.

Gas Ignition Problems
When observing a gas furnace light, you should never place your face directly in front of the furnace. If there is a delayed ignition or flame roll-out you can be inside the fire-ball. I have made that mistake. It was over before I knew what happened. For a second all I could see was yellow because my head was in the fireball that came out of the furnace. Luckily it just singed my eyebrows a bit and gave my face a slight burn similar to a sunburn. Afterwards I worked out what had happened: a leaky gas valve had allowed a build-up of gas prior to turning the furnace on. Had my face been off to the side I would not have been in the flames when they came out.


Don’t leave your personal safety to chance. 
Take steps to detect and avoid possible personal safety hazards. It is an inconvenience to the customer to have to call 911.


Friday, October 7, 2016

Sorting Out Refrigerant Flammability

Most techs know that ASHRAE Standard 34 originally established three categories of refrigerant flammability: 1,2, and 3. They ranged from 1 – nonflammable, to 3, highly flammable. Category 2 was listed as mildly flammable, or somewhat flammable. Then they added a new category – 2L – for an even lower category of still flammable refrigerant. I admit that I always found that a bit confusing. In my mind, it either burns or it doesn’t.  In order to get a better handle on this I have done some studying.

Two characteristics are used to differentiate category 1 and category 2 refrigerants: the lower flammability limit and the heat of combustion. The lower flammability limit is the lowest percentage concentration of gas in a gas-air mixture that will ignite. Concentrations lower than the lower flammability limit will not burn. Even highly combustible gasses such as gasoline have a lower flammability limit. Refrigerants with a lower flammability limit of 3.5% or less are considered class 3, highly flammable. For comparison the lower flammability limit of gasoline is 1.4%  and propane‘s is 2.1%. Another way for a refrigerant to be considered class 3 is for its heat of combustion to equal or exceed 19 million joules per kilogram. In general terms, it does not take very much class 3 refrigerant to burn and when it does it is very hot.

Class 2  refrigerants have a lower flammability limit greater than 3.5%. It requires more than 3.5% concentration in order to ignite. Class 2 refrigerants do not burn as hot as class 3 refrigerants: their heat of combustion is lower. The lower heat of combustion is important because that is what sets other things on fire. It is possible for a class 2 refrigerant to burn without burning up everything around it.

So where does the 2L come in? Flammability class 2L is really a subclass of 2. Refrigerants with a 2L designation have a burning velocity of 10 centimeters per second or slower. The burning velocity is how fast the flame travels. A burning velocity of 10 cm/s means that the flame will travel about 4 inches in a second. In contrast, the class 2 refrigerant HFC-152a  has a burning velocity of 23 cm/sec.  – a little more than twice as fast.  Propane, a class 3 refrigerant, has a flame velocity of 39 centimeters per second – 4 times as fast.

Why is this important? The flame velocity and heat of combustion are what determine whether or not an explosion can occur. Rapid burning and high heat of combustion expand the air and combustion gasses so rapidly that great pressure is created, blowing things apart. Class 2L refrigerant cannot burn fast enough or hot enough to blow anything up. In many cases, a burning class 2L refrigerant will not even catch other combustible things around it on fire.

To summarize:
Class 3 Refrigerants have a lower flammability ratio of 3.5% or lower and/or a heat of combustion equal to or greater than 19Mj/kg. They burn fast and hot.

Class 2 Refrigerants have a lower flammability ratio exceeding 3.5%. It takes more of them to burn and they do not burn as hot as class 3 refrigerants.

Sub-Class 2L Refrigerants in addition to a lower flammability ratio exceeding 3.5% also have a flame velocity of 10 cm/sec or less. They burn slowly and without releasing as much heat.

Class 1 Refrigerants do not burn.