Caught One!

The lead story of the August 11, 2014 Air conditioning Heating and Refrigeration NEWS is “Man Gets Prison Time for Venting R-22.” In this particular case he was stealing copper – he just did not bother to recover the refrigerant first. The police literally caught him in the act, and knowing what he did was a Federal violation, reported him to the EPA. Now he is serving 31 months in prison. Truthfully, most people who steal copper or vent refrigerant are not caught. However, this case proves that you CAN be caught, and there is a substantial penalty.  Some people do the right thing because that is the way they conduct their lives. Others need some external reinforcement to avoid doing what they know they are not supposed to do.  Without penalties for breaking the rules, these folks will ignore the them. Hopefully this incident will be widely publicized so that other potential thieves in need of external reinforcement will consider another line of work. Or at the very least, steal something that does not involve venting refrigerant.

Here is a link to the story Prison Time for Venting Refrigerant

Oxy-Acetylene Torch Safety

One of my e-buddies, Dave Christensen, suggested that I write about oxy-acetylene torches. He recently bought a new torch and confessed that he read the instructions before using it. In the instructions, he noticed that the regulator settings were different from the ones he had used for years. When we teach students to use torches in school, we typically teach them the regulator settings that work for the equipment we have. I am afraid we may not always make sure students understand that torch settings are not universal. The correct regulator setting depends upon the torch manufacturer, the tip size, and the application. Torch manufacturers typically provide these settings in the instructions.

There are a few guideposts that stay the same. For example, you NEVER, NEVER, NEVER set acetylene above 15 psi. In fact, I get nervous above 10. The reason is that acetylene is unstable at pressures above 15 psi and can explode. So how does it not explode in the acetylene cylinder at 250 psig? It is dissolved in acetone liquid which is stabilized in a porous core. That is why you should never transport or use acetylene cylinders on their side – it lets the liquid run out of the cylinder into the valve area. Also, you really don’t need the oxygen above 20 psig. Many tip charts have it about half that for most applications. However, the exact settings you should use are ... in the instructions!

Another common safety issue is leaving your regulators set and just opening and closing the tank valves when you want to use the torch. This is convenient and saves time, but it is dangerous. Regulators can fail because of the sudden bump in pressure. This can cause parts to fly and high pressure gas to stream down the hoses. The last thing you should do when shutting off your torch is to adjust the regulator T handles out counterclockwise until all the spring pressure is released. When the cylinder valves are opened they should be in this position. AFTER opening the cylinder valves you can adjust the regulators to he correct pressures.

When lighting the torch, you should light the acetylene first by itself and then bring in the oxygen. Opening both the acetylene and oxygen simultaneously can cause oxygen to flow into the acetylene hose and regulator if the oxygen pressure is higher than the acetylene pressure. This can create a very dangerous situation – a mixture of fuel and oxygen under pressure in the hose and regulator. The only place we want this type of combustible mixture is in the tip.  When shutting down, reverse the process. Close the oxygen first and then the acetylene.

Torch manufacturers have some very good training material available for free. Here are some links to some good training resources.

http://training.victortechnologies.com/

http://www.harrisproductsgroup.com/en/Products/Equipment.aspx

http://uniweld.com/en/uniweld-videos

Stubby Gauges

Anyone who has ever disconnected a hose from a Schrader valve knows about the spray you get as a result. If you are taking a hose loose from the liquid line there can be quite a lot of very cold refrigerant spraying out. Many people don’t realize that the spray is usually NOT coming from the Schrader valve, but from the hose! The spray is from refrigerant that is trapped in the hose coming back out when you loosen the hose. By my calculations a standard 5 foot 1/4” hose holds about 3.5 ounces of R22 liquid. Releasing it is bad for the atmosphere, bad for the system, and bad for you if it gets on your skin. If the system was perfectly charged before you connected your gauges, it is no longer after you take them off.  If you were to connect a 5 foot hose to the liquid line of a dorm refrigerator and fill up the hose, you would essentially suck most of the charge out into your hose and gauges. Of course you would first have to install a piercing valve or two – creating potential leaks to boot.

My point is that you don’t always need to connect your gauges to every system you see – especially small critically charged systems. Even on larger systems, if you are connecting gauges just to check the system operation, consider getting a couple of “short gauges.” These are essentially a gauge mounted on just enough tube to connect it to the system. They hold a minimal amount of refrigerant, so the amount released is much less. This saves the atmosphere, is better for the system, and is way better for your fingers. Here is a link to a picture of a set of stubby gauges used in an article on ice machine service found in Contracting Business Magazine.

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.

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.

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.

The Hidden Cost of Service

Many technicians wonder why the company bills $100 an hour for their work even though they make $20 and hour. The implication is that if they could collect the $100 for themselves, they would be rich! What follows is a short article I did a few years back in an attempt to answer that specific question. Some of the dollar amounts quoted can vary a good bit from one location to another, and also vary with time. But the basic principles remain the same.

The Cost of Providing Service

The cost of operating a business is an investment which is made with the expectation of receiving a financial return. Logically, why should someone invest a large sum of money in an air conditioning business if they are not going to make at least as much money as they would earn at the bank on that same investment?  For example, look at investment required to purchase a truck, tools, and supplies to put a service truck on the road. A modest truck with minimal tools and parts would easily be $120,000. If the business owner invested in bank notes and bonds, they would earn $6,000 to $12,000 with far less trouble or risk. But that is just the start. 

The original cash investment will not depreciate with time but the service truck will. After 5 years the truck and tools will need to be replaced. So $120,000 must be collected over the span of 5 years to replace the initial investment. That brings the annual total to $30,000 to $36,000 just  to recover your original investment and make a return comparable to bank returns. But there is more.

The truck will need insurance, maintenance, and gas if it is to make any money. This can easily run $100 a day. A service technician will be needed. If the technician is earns $20 an hour, their cost to the company is at least $30 per hour by the time mandatory obligations like social security, unemployment insurance, and health insurance are factored in.  Over a year this works out to $67,600 per year. But wait, there is more.

Unless this is a one truck service company, the company needs a place of business. This represents a much larger investment than the truck, but it is spread out over several trucks. Besides the obvious cost of owning or leasing the business, there is the cost of utilities, maintenance, and insurance on the building. These costs vary widely from one business to another, but it is common for the business overhead cost to be at least as much as the truck cost, so add another $30,000 to $36,000 per year for this truck’s share of the business overhead. 

A tally of these costs reveals that the truck will need to make $139,600 per year just to preserve the original investment and make a modest return that could be gained through bank deposits and bonds. Assuming that the truck is busy 52 weeks a year, 5 days a week, it needs to make $67 an hour just to recover the company’s investment. Also note that this cost does not stop if the truck is not working. If the truck averages 6 billable hours a day, the rate must increase to $90 per hour to cover the cost. 

Notice that the company now must charge $90 an hour to simply recover their cost even though the technician is only earning $20 an hour. If the company does not collect this much money, it will lose money and the technician is out of a job.  Please realize that these figures are for illustration only, every company’s costs are different. What is consistent from one business to another is that there are many costs besides the obvious ones and that failure to recognize and account for these costs will certainly result in failure of the business. 

Hilmor Scholarship Winners

Those of us who have been involved the HVACR industry sometimes wonder where the bright, energetic, new techs are going to come from. The need for more trained technicians is critical to the industry’s continued success. Recently, Hilmor showed us that the technicians can be found if we offer the right incentives and look hard enough. Hilmor, a brand new HVACR tool company offered three national scholarships in their first year of business and received over 500 applicants nationwide. Clearly there is some untapped talent out there. They chose three winners from among the 500+ entries: David Hall, Francisco Iniquez, and Kenneth Chavez. You can view their stories online at Hilmor’s web  page HERE

Watching these three young men describe why they wanted to study air conditioning it hit me: they are out there – we just have to find them. Their stories are similar to thousands of other young people who want to improve their life and are willing to work hard in order to do it. We need to show them that our trade offers that opportunity. I am proud to say that David studies at my school, and he has a bright future ahead of him. I know him personally, and I know he is exactly what this industry needs. I am sure Francisco and Kenny will do the industry proud as well. Take a look at the videos and think about the thousands of other people who could tell similar stories – then go out and find them.  They are out there.

Why Excess Air Is Important

Combustion requires oxygen, which furnaces get from the air. Ventilation of the combustion products from a draft hood appliance, such as a water heater or an older natural draft furnace, requires even more air. For theoretically perfect combustion you need 10 cubic feet of air for every cubic foot of natural gas that is burned. However, the burners in even the most modern and well designed furnaces are not perfect. Combustion appliances all introduce excess air to insure there is enough oxygen for safe combustion. Too little excess air will have the burners operating in an oxygen starved condition, creating high levels of carbon monoxide (CO). Too much excess air can also be bad. Too much excess air will cool the flame, and also produce high levels of CO. Typical older natural draft appliances with atmospheric burners use around 50% excess air, turning the 10 CF of combustion air to 15 cubic feet. Nearly all residential furnaces manufactured today are induced draft appliances with atmospheric burners. In these furnaces, the excess air is more typically 20% - 40%. Excess air can safely go as low as 10% for commercial power burners that do a better job of mixing the air and gas.

In general, excess air decreases efficiency by cooling the combustion process. For any furnace, the ideal amount of excess air would produce the highest combustion efficiency without introducing an excessive level of CO in the flue gas. In most cases, as you reduce excess air you will see both the efficiency and CO increase. If the amount of excess air is excessive, reducing the excess air may actually decrease the CO produced in the flue gas. You want to keep the air-free CO below 400 ppm, the ANSI standard. Many techs try to keep the air-free below 100 ppm. Older gas furnaces had primary air adjustments, making it possible to adjust the amount of air being mixed with the gas. Newer furnaces do not have any air adjustments. You can only adjust the amount of fuel by adjusting the manifold pressure or orifice size. Increasing the gas being burned has the effect of reducing the excess air because now more air is needed. However, you should NOT overfire the furnace in an attempt to improve efficiency. When making any adjustments to manifold pressure or orifice size, always check orifice sizes and manifold pressure against the manufacturers specifications and the heat content of the gas supplied by the local gas utility. To read more on how combustion efficiency and CO production are affected by excess air, check out the Combustion Guide from Tru-Tech Tools (it is a free download HERE).

Furnace Drains

One important aspect of condensing furnace installation is sometimes overlooked – the furnace drain. A 90% condensing furnace makes a lot of water – comparable to an air conditioner evaporator. All that water needs somewhere to go. In most installations, there will also be an air conditioning evaporator and a drain for it. It is natural to just run the furnace drain into the air conditioning drain, but that can lead to problems. The positive air pressure inside the evaporator cabinet can create a slightly positive pressure on the evaporator drain. If the furnace drain is connected directly to it, this positive pressure can push back on the furnace drain. On some furnaces, this can create a positive pressure at the vent draft switch, causing it to open and shut off the furnace. One solution is to run completely separate drains for the furnace and air conditioner. If the air conditioner and furnace are connected to a common drain, you need to leave an air gap between the furnace drain and the common drain so that pressure cannot back up into the furnace drain and vent. If you are using a condensate pump, make sure it is rated to handle furnace condensate. Because furnace condensate is slightly acidic, some condensate pumps are specifically NOT approved for use with furnace condensate. In case you are concerned about the acidity, you can breathe easy. It is about the same as a carbonated beverage. However, some codes early on required that the condensate from condensing furnaces be neutralized before going into a sewer system. So manufacturers produced acid neutralizing filters which were basically large PVC containers filled with rocks (usually limestone or marble). The acid reacts with the rocks, which have a basic ph that counters the acid. I don’t believe most places require this any longer, but I am not certain. Another issue to watch is the drain outlet. If a gravity drain ices up or is blocked with snow, the draft switch can trip and shut off the furnace. Also, remember that the furnace really does make a lot of water. Try not to dump this water in a place that will cause problems – like right over a sidewalk.

Hand Cranked Generator

I have had several people ask about building a generator students can turn by hand. I am putting a short explanation and several pictures on my blog. We built one using an ECM motor minus the module.

It puts out 3 phase AC. It is regulated only by the speed of the person turning it: you would not want to run your computer on it. To get enough speed we used a 12 inch pulley for the students to turn and a 1 inch pulley on the motor shaft: This produces 12 spins of the generator for every one revolution of the hand crank. I ordered the bearings, pulleys, belt, and shaft from Grainger.

We used heavy slotted shelving material to make the frame. This also came from Grainger - but it was left over from other projects.

We brazed a large hex nut onto a hub that mounts on the shaft and we turn it with a large socket on the end of a speed wrench.

 It has been working for years - just needs a little tightening and adjusting from time to time. Students can fairly easily get to 120 volts - until I turn on a light.

 


One change I would make - we mounted the bearings to a couple of pieces of slotted angle and it is too flexible - hard to align the bearings so they don't bind. Plus, the bolts holding the slotted metal are also the ones that have to be loosened and tightened to adjust the belt. I would replace that with a solid block of metal and then mount that block to the frame.

 It took 2 of us about 4 hours to make.

Reading Voltage Across Switches

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

The Air First Pledge

I want you to take the “air first” pledge. “I solemnly swear to check the system airflow before I connect my gauges.” If the system airflow is off, the pressures are going to be wrong, so there is no point in connecting your gauges until you know that both the evaporator and condenser are clean and the correct amount of air is moving through each of them. No amount of refrigerant can correct for a dirty air filter, you have to change the filter. I understand that not everyone in the air conditioning business has a tool for measuring airflow. But we are in the AIR conditioning business! Would you trust an electrician who worked without a volt meter? You don’t have to have a flow hood to measure airflow. There are several tools under $300 that do a good job. You can get a Fieldpiece hot wire anemometer, several companies make reasonably priced digital manometers, there are many inexpensive rotary vane anemometers, or you can get a Magnehelic gauge for less than $100. Dwyer sells an airflow meter for less than $50 that reads both velocity and inches of water column pressure. It is not in the same class as the other tools mentioned, but it is a whole lot better than nothing. Why should you invest in a tool that you have been doing without? For one, customers notice when you use instruments instead of guessing. But the best reason is because it makes your job easier. It is always easier to solve problems if you have good data, which you can’t get by holding your hand over the register. How many times have you added refrigerant to a system only to discover later that the coil was plugged up with cat hair? Wouldn’t it have been easier to check the airflow first and correct the real problem? Even if I can’t convince you to start measuring airflow, please at least check the air  filter and check out the airflow with your handomometer before pumping refrigerant into a system that does not need it. Take the air first pledge! 

The Hand-O-Mometer

Most technician’s favorite instrument is the hand-o-mometer. They use it to measure air temperature, suction line temperature, liquid line temperature, air velocity, and airflow. A few even use their hand-o-mometer to measure voltage, although that is not recommended as it can fry the microprocessor. Yes, we grab the suction line to see if it is cold, we grab the liquid line to see if it is warm, we hold our hand over air outlets to see if we have good airflow. At times it seems like we are trying to heal the system by laying on of hands. I must admit, I do it too. I feel compelled to touch the unit. We are like Thomas – unless we put our hands on the suction line and in the air-stream, we will not believe. The problem is that hand-o-mometers take decades to calibrate. In truth, even the most experienced hand-o-mometer is just not very accurate at any of these readings. We can say that the fan is blowing, the unit is cooling, or the unit is heating using our hand-o-mometer. However, we can’t say for certain that a system is performing the way it should just because the suction line is cold and the air leaving the registers feels good. In the era of high energy costs and increased awareness of system efficiency, this is simply not good enough. Employers and customers are demanding accurate measurements – not just rough approximations.

The idea is to use accurate measuring instruments to take system operational data and compare the data with a standard provided by the equipment manufacturer or system designer. Then if the data does not fall within specified parameters, we analyze the cause, make adjustments, and take new measurements. I believe this takes three things: accurate instruments to take the measurements, a good understanding of how the system works, and the patience to perform service work correctly. In the end, you will save time doing things once the right way, instead of several "close enough" attempts. Brian Baker has suggested a phrase to me that sums this all up

“Diagnostic analysis is the rule, so use proper tools”

So my suggestion is that we start using accurate instruments to perform diagnostic analysis and use our hands for more important things, like holding a cold beverage at the end of the day or hugging our wife and kids.

R-22 Conversion - What to Avoid

After reading a lot of technical literature, attending several talks and seminars on R-22 conversion I have developed the following cautions on R-22 conversion.

First and foremost – if you convert a system from R-22 to ANY replacement refrigerant, you are conducting a field experiment on the customer’s equipment using their money. Make sure the customer understands that they are paying for an experiment which may or may not end successfully. I think I would get that in writing.

Since all the replacement refrigerants are zeotropes, they should not be used in flooded systems because they will fractionate in the evaporator.

Since all the replacement refrigerants are immiscible with mineral oil, they should not be used in systems with large receivers (without changing the oil to POE) because the mineral oil will separate and float on top of the refrigerant in the receiver.

Some of the replacement refrigerants have trace amounts of hydrocarbons or POE to help prevent oil logging in the coils and lines. This works well in many systems, but it does not help in the receiver where there is not much refrigerant movement.

DuPont says that the churning in accumulators discourages separation in the accumulator. However, they also say that you may need to add 10% POE if you have oil return problems. 

I am nervous about heat pump accumulators – especially in cold weather when a large amount of the charge is just sitting in the accumulator.

You should NOT weigh in the same amount of replacement refrigerant as R-22 because all the replacement refrigerants are less dense than R-22. A general rule is somewhere around 75-80%.

You should NOT just try to match the pressures you are used to seeing with R-22. A better indicator would be to measure the system subcooling and superheat and shoot for “reasonable” numbers.

You should replace all O-rings and Schrader valve cores before putting in the new refrigerant. O-rings can shrink when exposed to the new refrigerant creating a leak where none previously existed.

You should NOT just add the new refrigerant on top of the R-22. If you do that, you are creating your own special blend which is not EPA SNAP approved.

Just because a refrigerant matches the pressures of R-22 does not mean it will match the mass flow rate. If the mass flow rate is too different from R-22 the metering device won’t work correctly.

Make sure any refrigerant you use is EPA SNAP approved for the application. Any reputable refrigerant will have an ASHRAE refrigerant number and safety rating – not just a trade name or number.

One way to be sure what you are using is safe is to only buy refrigerant from recognizable manufacturers at normal supply houses, not online.

Under NO CIRCUMSTANCES should you use any of the “Organic” replacement refrigerants available on the internet. The “organic” components are propane and butane. They don’t have trace amounts of hydrocarbons, they are ALL hydrocarbon. These refrigerants are NOT EPA approved and they are NOT safe to use in a system which was not designed for flammable refrigerant.

If the customer has already purchased some “organic” refrigerant and tried charging their system, I would not work on the system. It is an accident waiting to happen.

Sucking Through a Coffee Stirrer

Have you ever tried using a coffee stirrer as a straw? I have attempted to use a coffee stirrer as a straw when I was really thirsty, needed a straw, and none were available. After all, they do look like a straw: they have a small hole running up the middle. In fact, you can get a little bit through, but the process is slow and frustrating. The restriction created by the small hole in the coffee stirrer just will not allow very much through. When you connect your vacuum pump up through standard 1/4” hoses, leaving the Schrader cores in the Schrader valves, you are essentially forcing your vacuum pump to draw through a coffee stirrer. It’s not impossible, but very slow and frustrating. The restriction imposed by the Schrader valve and small diameter hoses restrict how much gas can come through, slowing the process down. You can dramatically reduce the time it takes them to evacuate a system by removing these restrictions. In fact, removing the restrictions will do far more than getting a bigger vacuum pump. The same pump you already own can probably evacuate systems in half the time you are accustomed to by simply removing the restrictions (assuming you keep the pump clean and change the oil). The biggest restrictions are the Schrader valve cores. You can buy two vacuum rated core removal tools and dramatically reduce your evacuation time, even using the same hoses and gauges  (so long as they don’t leak). The core removal tools allow you to remove the core, evacuate the system, charge the system, and then replace the cores. Next, you might want to use 3/8” or even 1/2” hoses to evacuate rather than 1/4” hoses that came on your charging manifold. That replaces the coffee stirrer with a properly sized straw. Finally, you should consider using a manifold with a larger bore. Any one of these improvements will make a noticeable difference; all together, the effect is close to amazing. Appion sells a Megaflow Speed kit that packages these three components together. Tru-Tech sells a Rapid Evac Kit that contains the hoses, valve core tools, and some Nylog vacuum sealer. They are both a little expensive compared to standard manifolds or 1/4" hoses, but they work much faster. Just ask yourself this – how much would you pay to cut your evacuation time in half.

If you teach air conditioning, you should contact Appion. They are giving away a vacuum pump to schools that purchase one of their Megaflow Speed Kits. While you are at it, ask for one of their recovery machines too. Note: this deal is just for schools – they are not giving away a recovery machine and vacuum pump with every gauge set sold. E-mail sharon@appioninc.com and ask for details on their educational program.

Warning: After you use better equipment you won’t want to return to your old coffee stirrers.

Does Your Vacuum Pump Suck?

For many technicians, the answer is no – which is bad. Vacuum pumps are supposed to suck. If you are using your compound gauge to tell you when you have a vacuum, you really don’t know what your vacuum pump can do because a compound gauge can’t tell you. The difference between a great vacuum and an awful vacuum just can’t be seen on a compound gauge. It is a little like trying to measure the distance of a millimeter using your car’s odometer. You need a micron vacuum gauge to check the vacuum your pump produces. It is not unusual for a vacuum pump to be in such bad shape that a vacuum gauge connected to it won't register anything. That is not because the gauge is broken, but because the pump does not suck. 

The reason many vacuum pumps in the field do not produce anything close to their rated vacuum or capacity is that their oil is not changed often enough. How often should it be changed? Basically, whenever it gets dirty, it should be changed. You might be able to pull a vacuum on several small, clean systems before changing the oil, or you might need to change the oil in the middle of an evacuation on a particularly nasty system. Vacuum pump oil should be clear. If it has become cloudy or discolored, it needs changing. It is never wrong to change the oil. You normally have several hundred dollars in your vacuum pump even if you got it on sale. Leaving dirty oil in it really does not make economic sense because the crud in the oil is eating up your machine.

The oil not only lubricates the mechanical parts, it also provides the vacuum seal. When stuff is dissolved in the oil, the oil produces a vapor pressure from all the stuff in it – water, refrigerant, flush solution. The vacuum pump cannot pull down any lower than the vapor pressure of the oil in it. So if you have 10W30 instead of vacuum pump oil, or your 10W30 is full of water from all the systems you evacuated this past month, your vacuum pump likely does not suck.  If you have a traditional rotary vane vacuum pump with the oil reservoir on the outside and a sight glass in the middle, you can usually remove that oil reservoir and clean it. We actually change our oil a lot at school – a whole lot more than usually happens in the field. But we still get a good layer of scum on the bottom.  We dismantle our pumps at school at least once a year and clean out all the crud that has collected in the bottom of the oil reservoir. Just pouring oil through does not get the job done. So if your vacuum pump does not suck, try cleaning it and changing the oil. 

Its In the Bag!

I have had an eventful two weeks – first in Colorado Springs at the 2013 HVACR & Mechanical conference and next in Las Vegas at the 2013 HVAC Excellence Educators and Trainers Expo. Even though I am very glad to be home I always am energized by these events. The educational sessions are great, put on by industry professionals who are tops in their field. Although I love ogling the latest techie toys, there are often inexpensive ideas and tips that help demonstrate how systems work. For example: you can use a large plastic garbage bag and a stop watch to demonstrate airflow. You flatten the bag, place it over a register, and time how long it takes to fill up. Then a quick calculation gives an idea of the CFM. The formula works like this – there are approximately 7.5 gallons per cubic foot, so a 55 gallon trash bag = 55 gal/7.5 gal/ft³ = 7.33 ft³. The flow in cubic feet per second is determined by dividing 7.33 ft³ by the seconds it takes to fill the bag. That multiplied by 60 gives you CFM. Written out it looks something like (7.33 / seconds to fill bag) x 60 = CFM. You can even do return air by filling the bag and then holding it over a return grill so that it completely covers it. You time how long it takes to collapse the bag. Now I am not recommending this as a means of checking system performance, but it is great for demonstrating exactly what is meant by cubic feet per minute. What I love about this is it demonstrates both the volume by seeing the bag fill up, and the time by clocking how long it takes. After demonstrating the concept of air flow you can show how to measure it properly with accurate instruments. Hopefully, the students will have a better idea of exactly what is meant by CFM and the measurements will mean more to them.

Preventative Maintenance Saves Money in the Long Run

Every now and then I take a break from writing and give someone else an opportunity to contribute to my blog. The following article was provided by my friends at Chiller Systems Service in Denver Colorado. 

You depend on your air conditioning unit to keep you cool during those hot summer months. Neglecting that comforting utility could lead to days without cool air to keep you satisfied when the temperatures are too hot to handle. With preventive maintenance on your AC, you don’t need to worry about sitting in the heat and being miserable. 

Just like your other valuables, preventative maintenance is necessary in order to keep those possessions running and possible increase its life span. A professional technician is capable of giving you the peace of mind you deserve with your AC unit. They are able to address the voltage and electrical current levels on the AC motor, clean the coils and filters, and check the refrigerant. By checking that all of the parts of your AC are working properly, your system will not run longer than appropriate, restrict air flow, or have high pressure levels. When your AC system works properly it will be efficient, durable and have good indoor air quality.

One performance you can do without a professional technician as preventative maintenance is changing the filter on a regular basis at least twice a year. This is the least expensive thing you can do to maintain your AC system. Without a clean filter, dirt and air pollutants can easily enter through the system, damaging your health and the equipment. Colorado has a tendency to have higher pollutant levels, so having a clean filter at least twice a year will help you avoid the pollutants from entering your home.

A professional technician is required to keep your AC running properly and they can perform the preventative maintenance needed. Each AC unit is different, therefore there are customized programs created to meet the variety of needs that each AC has. A professional technician will also be able to solve any issues that might be happening and prevent it from being an issue when using your AC is essential by being consistent and having the proper technology to diagnose any issues.

By committing to yearly preventative maintenance on your AC, you will reduce the cooling costs of your home, saving you money in the long run. You will also be increasing your equipment efficiency, giving you the most from your initial investment and providing you with comfort throughout the summer without any hassles.

About the Author:

Denver HVAC repair company, Chiller Systems Service, is pleased to bring you this article about preventive maintenance on your A/C unit. If you are interested in Denver HVAC, please be sure to check out their website today, at www.chillersystemsservice.com.

Acetylene Cylinder Safety

I am writing on this subject because I saw a report on CNN discussing an explosion in the back of a car set off by energizing the electric trunk latch. It blew off the trunk and mangled the rear end of the car. Fortunately, nobody was hurt, but the possibility of a lethal accident was certainly there. The fireman that is interviewed mentions that there was an acetylene cylinder in the back of the car which leaked, and the trunk latch set it off. The acetylene should not have been there at all. Acetylene cylinders contain liquid acetone that is stabilized in a porous, cement like material. The acetone is there to dissolve the acetylene gas stored in the cylinder. Acetylene gas is unstable above 15 psig, but must be stored at a much higher pressure to store enough for practical use. Dissolving it in the acetone allows the higher pressure without creating a bomb. The cylinder regulator reduces the acetylene pressure to less than 15 psig. The actual pressure depends on the regulator setting. Note that you should NEVER adjust an acetylene regulator to a pressure above 15 psig.

Since acetylene cylinders contain liquid acetone, they should NEVER be laid on their side. They should ALWAYS be transported in the vertical position, securely fastened to the vehicle. Laying an acetylene cylinder on its side can result in the liquid acetone leaking out into the valve and regulator – setting up a very hazardous situation. You also should not have cylinders in the back seat behind you. Not just for the explosion hazard, but also because of the shifting weight in case of an accident. Any heavy objects behind you will crush you in an accident. My wife’s cousin was killed many years ago transporting cylinders in the back of his car. They crushed him in an accident that would otherwise probably not have killed him. That is why working trucks have a metal cage between the driver and the stuff in the back – to save your life in an accident. Basically, what this all means is that THERE IS NO SAFE WAY to carry an acetylene cylinder in your Prius! If you are going to transport torches or cylinders, you need a properly outfitted truck – not your family sedan.