Author: Kaleb Saleeby

Technician/Trainer/Content Creator Myrtle Beach, SC

   

Everyone in the HVAC/R trade uses some form of torch to braze or solder alloys together. So what is the proper way to handle an oxyacetylene torch? Turns out, there’s more than one right answer. Depending on which torch rig you use, the manufacturer’s manuals for operation may vary. 

Everyone (hopefully) knows a neutral flame on a torch tip is suitable for most applications. Sometimes a carburizing flame is useful for reducing oxidation. The only flame we all should avoid is the oxidizing flame. However, in order to achieve the correct flame, a technician must fully understand the type of torch tip they are using, and the application for which the torch is being used.

For example, a “rosebud” tip is a (often) a large high BTU tip, and may be too large for most residential applications. A lot of technicians will attempt to lower the fuel and oxygen pressures feeding the tip to reduce the temperature. However, the tip begins to starve due to a lack of adequate fuel/oxygen mixing, and the flame will back into the torch tip and coat the inside with a carbon coating, which can damage the tip and torch over time. On the other hand, a torch that is too small will never get hot enough for an application outside its design parameters.

So what tips are best? At what pressures must tips be set? There are many answers to these questions, and they all depend on the brand of equipment you use, and the application in which you work.

I had the opportunity to speak to Tim Thibodeaux from the Service Dept. at Victor Technologies, and with Matt Foster from Uniweld Products, Inc. Both confirmed that pressures are tip specific, and operating procedures are brand-dependent. For example, many technicians have been taught to shut off the FUEL first when shutting down the torch, but this contradicts manufacturer instructions.    

Uniweld states in their operation manual to shut off the OXYGEN first at the torch when following proper shutdown procedures. This is done to prevent flashback, or backfire. 

Uniweld Shut-down Prodedure

Victor Shut-Down Procedure

Victor, too, requires the operator to shut off the OXYGEN first at the tip, then the operator may shut off the fuel valve. The reasoning remains the same: to prevent backfire/flashback. So where does this “Shut off the fuel first” myth come from? Turns out, it’s been taught that way for decades, but not without reason.

I had the opportunity to speak with HVAC/R Training Legend Bill Johnson, one of the original authors of the Refrigeration and Air Conditioning Technologies (RACT) Manual, and we spoke extensively on the topic. The RACT Manual offers an alternative method of shutting down the torch rig. The textbook teaches to shut the FUEL off at the torch first

“Shut off the fuel gas (acetylene) valve at the torch first”
Refrigeration and Air Conditioning Technologies (8th Edition)

I asked Bill Johnson why that was, and he explained it was a way of protecting the technician over the tool. Starve the flame of its fuel first, and eliminate the flame right away. Also, this was the way he had been taught many years ago, and the first edition of the RACT Manual was published in 1987. Perhaps there was once a manufacturer operation manual that specified the “fuel off first ” method, but the procedures have since changed. This method is not without merit, as its intentions are pure.

With the proper PPE and setup procedures, following the manufacturers’ approved operation instructions should be standard across the trade. Some would argue that shutting the oxygen off first can cause the little carbon “bunnies” that are created when the acetylene pressure is low enough. This is easily rectified by changing the way you setup the torch to begin with keeping acetylene pressure at the tip specified level.

Uniweld Tip 17-1

Matt Foster from Uniweld mentioned several operating tips for torch tips and setting a flame. The most common torch tip he finds most technicians use is the Type 17-1, and is good for pipes with an inside diameter of up to 1”. The manufacturer’s design operating pressures for this tip is 5 acetylene/5 oxygen. Another common tip is the Rosebud Type 28-2; its operating pressures are 5-7acetylene/5-8 oxygen, and it is good for pipes with an inside diameter of up to 1-5/8”.    (Caveat: According to Matt, these published operating pressures may be even higher, as torch tip engineering changes over time, and the current catalog has not yet been updated. Therefore, when in doubt, take a look at the spec sheet that comes with the torch tip, or call the manufacturer to clear things up).

The Uniweld welding/brazing tip rated operating pressures can be found in their catalog here. The Victor welding/brazing tip rated operating pressure can be found here. As you can see, there is no one right answer when it comes to setting regulator pressure at the tanks. In schools, it is often taught to set fuel to 5psig at the regulator, and oxy at 10psig at the regulator. Some say the pressures should be the same at the regulator. The purpose for the pressure specifications is to ensure proper mixing of the gasses for the best quality flame, and to protect the torch rig from damage and compromised safety functions. So the answer to how to set your oxyacetylene regulator pressures is: it depends!

In other words…RTFM! (Read the FANTASTIC Manual) Hopefully, this clears up any confusion about torch rig operation and setup/shutdown procedures. Remember to ALWAYS wear proper PPE when dealing with any flame (eye protection, gloves, etc, and avoid polyester clothing), and follow industry best practices regarding safety.

— Kaleb

Pump down solenoid valves are commonplace for any refrigeration technician. They are energized with the compressor still running, shutting off flow in the liquid line so the refrigerant is pumped into the condenser and receiver. The compressor will then shut off once a low-pressure switch opens the circuit when the pressure falls below a set pressure. However, there are other applications for which liquid line solenoid valves are useful. Long line applications in HVAC incur a wide range of challenges a technician must evaluate. Among those challenges include oil return, refrigerant migration in off-cycle, compressor workload, efficiency and capacity losses, added refrigerant charge, and metering device selection.

Long line applications (for R410a straight AC and Heat Pumps with ⅜” liquid lines) are generally defined as any system with a line set longer than 80 ft in equivalent length. Equivalent length in this context means that all pressure drops (copper fittings, bends, diameter size changes) translate to a length equivalent to a run of straight copper. Manufacturer spec data for copper fittings will have printed the equivalent length of those fittings in its literature. The length to be exceeded before long line application procedures are used may vary depending on line set diameter size and on which plane the indoor and outdoor units are located, but 80 ft is the general rule for Residential AC and HPs. Any system with a 20 ft uninterrupted vertical rise in the line set should also be treated as a long line application, per Carrier’s Long Line Application Guideline, which will be linked here.

 

There are many ways manufacturers have sought to resolve the challenges with long line applications. Some of these solutions include crankcase heaters and txv metering devices. Most manufacturers will specify an OEM hard-start kit for the purposes of protecting compressor effectiveness against the added refrigerant charge. Some commercial applications require oil traps to aid in oil return. 

 

Liquid line solenoid valves are specifically utilized to prevent refrigerant migration in the off-cycle. The valve is positioned with the arrow printed on the valve body pointing toward the outdoor unit. For heat pumps, the valve must be biflow. It is important to note that the valve is normally closed in these long line applications. When energized with the contactor of the outdoor unit, the coil in the valve body will pull the valve open to allow flow. However, when closed, the valve only stops refrigerant from flowing in the direction of the arrow printed on the valve. With the system in the off-cycle, the solenoid valve will keep refrigerant liquid and vapor from migrating to the compressor down the liquid line. But don’t let the refrigerant tubing size fool you! Just because the liquid line is 3/8″ doesn’t mean any liquid line solenoid valve with 3/8″ sweat or flare connections will do. Care must be taken when selecting a solenoid valve. Choose valves to match the capacity of the system on which it will be installed (with a pressure drop of no more than 1 psi), then pay attention to refrigerant rating, THEN select by line set diameter size. 

 

Wiring a liquid line solenoid valve will generally tap in with the thermostat’s call for the compressor. The valve should be wired into the Y (outdoor unit contactor) and C (common) terminals on single-stage equipment. For two-stage equipment, make sure the valve opens with a call for the first stage of heating or cooling (Y1). This prevents the valve from remaining closed during compressor operation.

Solenoid valves are incredibly simple in design and operation, and troubleshooting for long line applications is also quite simple. Confirm the coil is receiving its rated applied voltage when the system is energized, and test temperature drop across the valve. A maximum of 3° difference is allowable. The valves are NC (normally closed), so if there is a temp drop across the valve body, but no applied voltage during system operation, confirm your wiring. 

 

Always make sure you are applying industry best practices when installing a solenoid valve. Remove the coil from the valve body before installation to prevent overheating. Use a heat absorption putty, spray, or wet rag on the valve body. Flow nitrogen while brazing, and install filter driers everytime (oversized if possible).

 

Long-line applications are few and far between in residential HVAC. But if you ever encounter a situation where you see a liquid line solenoid valve next to the outdoor unit, pay close attention to the way that system is setup and any other added accessories that may have been installed. You may refer to the Residential Long-Line Application Guideline at any time.

 

-Kaleb Saleeby

Capacitors are traditionally tested with a capacitance meter (commonly found as a function within a multi-meter) with the component taken completely out of the circuit. “Bench testing”, as this method is referred to, is hands down the safest method of checking capacitance in micro-farads. All other methods require the capacitor to be wired into the circuit with an applied load. To bench test, you simply take the meter leads and check across the terminals of the capacitor. For a dual-run capacitor, you would check between the Common terminal and whichever side (Fan or Herm) you wished to test.

Another popular test many technicians use is the “Under Load Capacitance Calculation”. This test is performed while the system is in normal operation. A technician would measure voltage across the terminals of the capacitor (again, Common and Motor terminals if dual-run), then current off the start winding of the motor to which the capacitor is attached. Next, you plug those values into a calculation, which uses a mathematical constant: (amps x 2,652) ÷ voltage. Finally, the product of that calculation is compared against the rated capacitance printed on the capacitor. As long as the calculated value is within +/- 6% of the rated value, the capacitor quality is acceptable.

Bench testing and capacitance calculations are pretty popular choices when verifying the capacitance of a capacitor against its rating. However, there is yet another way to test a capacitor under load you may not have thought of before. You can use a power quality meter to check the capacitor under load using power factor. In order to explain the validity of this measurement, here is a review of reactive power, inductive loads, and capacitors.

Reactive power is one of three different types of power in an alternating current circuit. True Power is the actual energy in watts dissipated by a circuit. In other words, the real work being done. Then there is Apparent Power, measured in Volts-Amps (VA). Apparent power is the RMS current multiplied by the RMS voltage. Reactive Power is the power dissipated as a result of either inductive or capacitive loads. Reactive Power is measured in Volts-Amps Reactive (VAr). When the current and voltage waveforms are out of phase with each other, that is reactive power.  Inductive loads, such as a condenser fan motor, are inductive by virtue of the fact their alternating current lags behind the alternating voltage as the current flows into the load. Capacitive loads have an alternating current waveform that leads the alternating waveform of the voltage.

For the purposes of this tech tip, inductive loads will be exclusively discussed, because they are most common in the residential field; i.e. condenser, blower, and compressor motors. Inductive loads use a magnetic field to cause physical movement. The magnetic field is generated as electric current flows through a coil. In other words, this current/energy used to generate a magnetic field is known as reactive power. Notice, however, there is no real work being done. The force of the magnetic field can cause physical movement (work), but it does no real work itself. Inductive loads need reactive power in order to do work, but by using more and more reactive power, the load uses also uses more current (usually from the utility company). Take a look at the “Power Triangle”. Pictured is a power triangle depicting an inductive load. The hypotenuse of this triangle is notated as Apparent Power (the available power in the circuit). The leg on the y-axis is notated as Reactive Power (magnetic field), and the leg on the x-axis is notated as Real Power (actual work being done). If you notice the Theta symbol in the left acute hypotenuse angle (𝜭), this is referring to the Power factor of the load. Power factor (cos𝜭) is the ratio of the average Real Power in watts to the Apparent Power in volts-amps . Ideally, the Apparent and Real Power would be the same, as in a Resistive load (i.e. a power factor of 1). However, inductive loads need a magnetic field.

If the reactive power leg on the y-axis were to increase and rise higher on the y-axis, the hypotenuse (apparent power) would also increase. The power factor, in this case, decreases, and moves closer and closer to the left acute hypotenuse angle, thereby increasing the distance between the Apparent power and Real power. This is counter-productive, because as the load uses more current, more heat energy is generated, and the energy used to do the actual work becomes inefficient.

Therefore, the goal of the engineer is to minimize the amount of reactive power the inductive load uses from the apparent power. Basically, the goal is to increase power factor back to as close to unity (1) as possible. This is when capacitors enter the scene.

Capacitors are generally accepted as reactive power generators. To understand more about how capacitors work, and some common misconceptions, check out these other tech tips/podcast episodes: Run Capacitor Facts You May Not Know (Podcast) 5 Capacitor Facts You Should Know

Capacitors, when applied to a circuit, decrease the amount of apparent power needed by the inductive load to generate the magnetic field. This effectively increases the power factor. Looking at the power triangle again, as the Reactive power on the y axis decreases, the hypotenuse (Apparent power) also decreases, moving closer to the Real power. This is the endgame for capacitors.

Therefore, it can be inferred from the understanding of inductive loads and capacitors: if a capacitor is attached to an AC circuit in an inductive load (like a PSC motor) for the purpose of bringing power factor back to as close to unity as possible, but the power factor is measured to be low, the capacitor must then be either sized incorrectly or failing/failed.

Using a power quality meter on an inductive load, a technician can judge the functionality of a particular capacitor. To do this, Voltage and Current must be measured simultaneously at the load. The Supco Redfish iDVM-550 is a great tool for this application.

It must be mentioned that using a power quality meter to measure power factor on a load is valid only when the load contains run capacitors like compressors and permanent-split capacitor motors. ECMs (electronically commutated motors) use a different type of technology altogether, and they are engineered for use with a lower power factor by design. Also, power factor testing is not practical for start capacitors either, since the capacitor is taken out of the circuit too quickly. This measurement is valid and practical only for PSC type blower, condenser motors, and most single-phase, single-stage compressors. 

We all understand vacuum pump oil is the life-blood of our vacuum pumps. We know what the function of vacuum pump oil is, and how it functions. But how do we apply that knowledge when choosing the oil best suited for our pumps? Many of us simply pick up what’s in the stock room, or on the shelves at the parts house. However, there is a good possibility your stock room and suppliers don’t carry the correctly designed pump oil for our trade’s vacuum pumps. In order to understand the types of vacuum pump oil, here’s a quick review on the characteristics of pump oil:

  • Vapor Pressure

    • The lower the vapor pressure, the deeper the vacuum the oil is rated for

  • Viscosity

    • Medium viscosity (thickness) is used for warmer temperatures

    • Lower viscosity (thickness) is used for cooler temperatures

  • Distillation

    • The process of removing sulfur from mineral oil to refine the oil and reduce vapor pressure

It is important to understand distillation because distillation defines the application for which the pump oil is designed.

Single distilled oil is mineral oil that goes through a distillation process one time. The process reduces the sulfur content of the oil, and the resulting oil color is light brown. This oil is used for single-stage oil-sealed rotary vane pumps. The ultimate vacuum of single distilled oil is 10 microns (1 x 10-2 torr).

Double distilled oil goes through the distillation process a second time, further removing the sulfur content of the mineral oil. The resulting color is a lighter brown. This type of oil is designed for use on most two-stage vacuum pumps and has an ultimate vacuum of 1 micron  (1 x 10-3 torr).

    

Triple distilled oil goes through yet another molecular distillation process and is devoid of sulfur or other impurities. This oil is chemically inert and is highly resistant to oxidation and reactance to other gases. Triple distilled pump oil is transparent and is designed for an ultimate vacuum of 0.6 microns (6 x 10-4 torr).

Hydrotreated oil is a high-end pump oil designed for high vacuum applications, such as industrial and science. Hydrotreated oils are inert, and achieve a higher purity than any distillation process could boast. The process by which this oil is refined involves a hydrocarbon oil being combined with hydrogen under high pressure and temperature. This removes sulfur, nitrogen, and various other impurities from the oil. This type of oil is the purest oil available (as well as the most expensive), and is clear in color. The ultimate vacuum of hydrotreated oil is not important, as this is not an oil our trade uses. However, it is important to understand some drawbacks associated with hydrotreated oils, because I have seen companies use this highly expensive oil without fully understanding the characteristics.

Distilled vacuum pump oil is mixed with specific solvents, which aid in lubrication, oxidation resistance, and foaming resistance. These characteristics are important for vacuum pump oil, as they increase the life and performance of the pump and the oil itself. Hydrotreated pump oil, however, does not share the same solubility as distilled pump oil. This means hydrotreated oils do not mix with the necessary additives our trade specific vacuum pumps require. This can lead to damage to a vacuum pump and decreased vacuum efficiency, if not used in the appropriate application.

    

Synthetic (Perflouropolyether) oil is the final oil we will discuss here. This particular oil is very inert, and has a molecular consistent viscosity. The non-naturally-occurring molecules of synthetic oil are uniform in composition; whereas a typical distilled mineral pump oil has a viscosity based on the average molecule size. Synthetic oil is designed specifically for highly corrosive vacuum environments that contain gases like hydrogen peroxide, chlorine, hydrogen fluoride, etc.. If a distilled mineral oil were used in these applications, it would quickly break down and end up overheating the pump due to inadequate lubrication. This type of oil is not for use in our trade.

 All these different vacuum pump oils are designed for a specific application. Many of the suppliers in my area carry triple distilled pump oil, and it is on the shelves of many stock rooms. However, the ultimate vacuum triple-distilled oil is rated for is beyond the design of our trade specific pumps. Triple distilled pump oil is for use in pumps rated for continuous operation, not the intermittent operation we apply to our pumps. The typical HVAC/R technician will use either a single distilled, or double distilled pump oil. Single-stage pumps use single distilled oil, and two-stage pumps use double distilled oil. It’s fairly simple to remember. Both oils are cheaper than triple distilled oil anyway, so there is really no reason to carry triple-distilled oil on the truck or in the stock room. Next time you’re in the supply house, look at the rated viscosity and vapor pressure of the oil on the shelves.

Another vacuum pump fluid worth mentioning is flushing oil (fluid). Flushing fluid is basically a solvent oil containing high concentrations of the helpful additives already present in distilled mineral pump oil. This pump fluid can be used to clean the residual contaminants (water, oxides, etc.) from your pump leftover by the previous oil. Flushing fluid can be highly beneficial before and after use of the vacuum pump.

 In summary, there are many different types of oil used in vacuum pumps, and our trade must be aware of the type of oil we use in our trade’s specifically designed vacuum pumps. In order to optimize the full performance our pumps were designed to deliver, we may sometimes need question the unspoken norms. Constructive skepticism will push our trade to the next level of professionalism and overall growth.

   

Know your pump, know your oil. The performance and ultimate vacuum of your pump demands you keep the correctly design pump oil in its vanes…see what I did there?

– Kaleb

References:

https://vacaero.com/information-resources/vac-aero-training/24460-vacuum-pump-oil.html

www.edwardsvacuum.com

www.vacoil.com

This article is written by up and coming young tech and new contributor Kaleb Saleeby. Thanks Kaleb!


Recently, I came across a work order description in my dispatch that made me scratch my head.


“Clean Salamander broiler”

I had to ask the omniscient Google for answers. Turns out, it has nothing to do with vividly-colored, “fireproof” amphibious creatures! The name does, however, pay homage to 17th-century lore that salamanders could withstand the heat of a fire, and were even believed to come from fire itself.

    

None of this information aided me in understanding how to clean this particular type of open-air broiler, so I did more research on how the appliance was constructed, and how it operates. From my findings, the overhead broiler is a very simple design. The basic components of a gas salamander broiler are as follows:

  • Gas valve

  • Gas manifold

  • Fuel orifice

  • Distributor

  • Igniter

  • Burner

  • Food racks

    

The gas valve on the appliance I worked on was quite literally just a knob the client manually turned on or off. When open, the gas valve allows a set fuel pressure through the manifold to be fed out a single orifice, which then gets fed through the burner. The gas is spread through the burner via a distributor to feed the ceramic plates at the end of the burner. The igniter would be the next in this sequence of operations; however, the appliance I worked on did not have a functioning igniter, and the client refused replacement, resulting in manual lighting. The ceramic plates of the burner are littered with tiny holes that allow the flame to burn uniformly across the burner with little to no major fluctuation.

    

None of my research gave me any answers on how to clean this equipment. I reached out to Refrigeration Technologies’ Chief Executive Officer and Founder, John Pastorello for advice on what chemicals, if any, he recommended for this job. According to John, Viper HD cleaner is safe and appropriate for the cleaning of this type of broiler. Viper HD is a slightly alkaline (basically neutral on the PH scale) cleaner that will not damage the fragile ceramic burner, as long as it gets rinsed. John states,

 

“You will need Viper HD and a scrub brush. As long as you rinse you will not have a problem with the heating elements. On stainless [steel], you can use HD with a soft scrub. Rinse then use a stainless steel cleaner to finish. The [stainless steel cleaner] will have a mineral oil that leaves a finger proof coating and brings out the luster. This is a labor [intensive] job because of the heavily carbonaceous soil.”

    

The cleaning of the appliance was fairly simple, albeit frustrating. The grease and grime were the hardest part. Once everything was clean and dry, I reassembled the appliance and relit the burner. After a few minutes of allowing the flame to stabilize, the appliance was operating well and to the satisfaction of the client.

    

In retrospect, I probably would avoid forcing water into the burner section. The burner assembly I worked on was riveted together, and did not allow access to the inside. I have since learned that there is insulation on the inside of the burner assembly, and wetting the insulation can potentially cause issues with the equipment, even if it has been dried off. I would recommend anyone else who encounters a job like this to use a Viper HD saturated towel and wipe the ceramic burner to clean it, and then rinse with a water-damp towel. I would also recommend focusing on the distributor inside the burner, as it may be heavily caked with carbon buildup. All other steps would remain the same. I also learned that there are overhead broiler models that have a burner design that does allow you to change the ceramic plates and insulation, if necessary, to make the cleaning process easier.

    

I hope this helps other guys, like me, who may get sent to do hot side service. It certainly is interesting!

– Kaleb

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