Author: Bryan Orr

Bryan Orr is a lifelong learner, proud technician and advocate for the HVAC/R Trade

In HVAC/R we are in the business of moving BTUs of heat and we move these BTUs on the back of pounds of refrigerant. The more pounds we move the more BTUs we move.

In a single stage HVAC/R compressor, the compression chamber maintains the same volume no matter the compression ratio. What changes is the # of pounds of refrigerant being moved with every stroke(reciprocating), oscillation (scroll), or rotation (screw, rotary) of the compressor. If the compressor is functioning properly the higher the compression ratio the fewer pounds of refrigerant is being moved and the lower the compression ratio the more pounds are moved.

In A/C and refrigeration the compression ratio is simply the absolute discharge pressure leaving the compressor divided by the absolute suction pressure entering the compressor.

Absolute pressure is just gauge pressure + atmospheric pressure. In general, we would just add the atmospheric pressure at sea level (14.7 psi) to both the suction and discharge pressure and then divide the discharge pressure by the suction. For example, a common compression ratio on an R22 system might look like-

240 PSIG Discharge + 14.7 PSIA = 254.7
75 PSIG Suction + 14.7 = 89.7 PSIA
254.7 PSIA Discharge ÷ 89.7 PSIA Suction = 2.84:1 Compression Ratio

The compression ratio will change as the evaporator load and the condensing temperature change but in general, under near design conditions, you will see the following compression ratios on properly functioning equipment depending on the efficiency and conditions of the exact system.

In air conditioning applications compression ratios of 2.3:1 to 3.5:1 are common with ratios below 3:1 and above 2:1 as the standard for modern high-efficiency Air conditioning equipment.

In a 404a medium temp refrigeration (cooler) 3.0:1 – 5.5:1  is a common ratio range

In a typical 404a 0°F to -10°F freezer application 6.0:1 – 13.0:1 is a common ratio range

As equipment gets more and more efficient, manufacturers are designing systems to have lower and lower compression ratios by using larger coils and smaller compressors.

Why does the compression ratio number matter? 

When the compressor itself is functioning properly the lower the compression ratio the more efficient and cool the compressor will operate, so the goal of the manufacturer’s engineer, system designer, service technician and installer should be to maintain the lowest possible compression ratio while still moving the necessary pounds of refrigerant to accomplish the delivered BTU capacity required.

The compression ratio can also be used as a diagnostic tool to analyze whether or not the compressor is providing the proper compression. Very low compression ratios coupled with low amperage and low capacity are often an indication of mechanical compressor issues.

Compression ratio higher than designed = Compressor overheating, oil breakdown, high power consumption, low capacity 

Compression ratio lower than designed = Can be an indication of mechanical failure and poor compression

Understanding compression is critical to understanding the refrigeration process. Don’t be tempted to skip past this because it is a really important concept.

Look at the pressure enthalpy diagram above. Top to bottom (vertical) is the refrigerant pressure scale, high pressure is higher on the chart. Horizontal (left to right) is the heat content scale, the further right the more heat contained in the refrigerant (heat, not necessarily temperature).

Start at point #2 on the chart at the bottom right. This is where the suction gas enters the compressor. As it is compressed it goes to point #3 which is up because it is being compressed (increased in pressure) and toward the right because of the heat of compression (heat energy added in the compression process itself) as well as the heat added when the refrigerant cooled the compressor motor windings.

Once the refrigerant enters the discharge line at point #3 it travels into the condenser and is desuperheated (sensible heat removed). This discharge superheat is equal to the suction superheat + the heat of compression + the heat removed from the motor windings. Once all of the discharge superheat (sensible heat) is removed in the first part of the condenser coil it hits point #4 and begins to condense.

Point #4 is a critical part of the compression ratio equation because the compressor is forced to produce a pressure high enough that the condensing temperature will be above the temperature of the air the condenser is rejecting its heat to. In other words, in a typical straight cool, air cooled air conditioning system the condensing temperature must be higher than the outdoor temperature for the heat to move out of the refrigerant and into the air going over the condenser.

If the outdoor air temperature is high or if the condenser coils are dirty, blades are improperly set or the condenser coils are undersized point #2 (condensing temperature) will be higher on the chart and therefore will put more heat strain on the compressor and will result in lower compressor efficiency and capacity.

As the refrigerant is changed from a liquid vapor mix to fully liquid in the condenser it travels from right back left between points #4 and #5 as heat is removed from the refrigerant into the outside air (on an air cooled system). Once it gets to #5 is is fully liquid and at point #6 it is subcooled below saturation but ABOVE outdoor ambient air temperature. The metering device then creates a pressure drop that is displayed between points #6 and #7. The further the drop, the colder the evaporator coil will be. The design coil temperature is dictated by the requirements of the space being cooled as well as the load on the coil but the LOWER the pressure and temperature of the evaporator the less dense the vapor will be at point #2 when it re-enters the compressor and the higher the compression ratio will need to be to pump it back up to point #3 and #4,

This shows us that the greater the vertical distance between points #2 and #4 the higher the compression ratio, which means that both low suction pressure and/or high head pressure result in higher compression ratios, poor compressor cooling, lower efficiency and lower capacity.

In some cases, there isn’t much that can be done about high compression ratios. When a customer sets their A/C down to 69°F(20.55°C) on a 100°(37.77°C) day they will simply have high compression ratios. When a low temp freezer is functioning on on a very hot day it will run high compression ratios.

But in many cases, you can reduce compression ratios by –

  • Keeping set temperatures at or above design temperatures for the equipment. Don’t be tempted to set that -10°F freezer to -20°F or use that cooler as a freezer
  • Keep condenser coils clean and unrestricted
  • Maintain proper evaporator airflow
  • Install condensers in shaded and well-ventilated areas

Keep an eye on your compression ratios and you may be able to save a compressor from an untimely death.

— Bryan

Some techs and contractors swear that flex ducts are an evil invention and should never be used in ANY circumstance. I agree with what duct design expert Jack Rise said on the podcast when I asked him about flex ducts he said:

“There’s a lot of problems with flex duct, there really is and it’s a good product but we abuse it…. It’s a good product, it’s just poorly handled”

While the proper sealing of ductwork in unconditioned spaces is nearly universally recognized as important, it is rare that a flex system get’s installed properly in these other important areas.

Fully Extend The Flex 

Some guidelines suggest pulling a 25′ piece of flex fully extended for 1 full minute before attempting to install it. This reduces the compression and the depth the of the corrugation (the accordion spiral inside the duct). The more compressed the duct is when it’s installed the greater the air resistance of the duct will be. The air duct council states that 30% of compression can result in 4 TIMES the air resistance. This means that fully extending the flex is a big deal and may be one of the most overlooked aspects of flex system installations. Cutting off that 2′ – 6′ of extra flex on the end instead of just “using the whole bag” can mean the difference between a good and a poor duct system in many cases.

Strap and Support the Flex 

Jack Rise spoke about how he tested a duct and measured a .2″ wc change in static when he altered a duct from sagging to properly strapped. In retrofit applications, many companies focus on “sealing” connections but they often don’t truly address sagging ducts with proper strapping. the allowable amount of sag is only 1/2″ per 4′ of length which isn’t much. Don’t ONLY rely on the code required strapping in your jurisdiction, just because a system passes inspection doesn’t mean it’s installed correctly.

Keep the Curves to a Minimum 

When designing a duct system you must calculate TEL (Total Effective Length) not just length. In a flex system each curve has a HUGE impact on the TEL and when a field install doesn’t match the design it can throw the whole system out of whack both from an air balance standpoint as well as a system performance by increasing the TESP (Total External Static Pressure). Every bend and angle matters so keep it extended, properly routed and well supported and all will be well so long as the design is correct.

Seal all the connections

As with all ducts the connections need to be well sealed. With flex, this will generally need to be done with mastic and the BEST way is to fully seal and allow the inner liner to dry before pulling the insulation over the connection. Also keep in mind that leaks, where the boot / can meet the sealing, are very cannon leak points and it’s a good idea to seal them from the inside and/or outside to the final floor or ceiling before installing the grilles

For more info go to the ADC (American Duct Council) website at flexibleduct.org or download their excellent guide HERE

— Bryan

I didn’t install this unit

First off, attic installations are among my least favorite applications from a serviceability, system longevity and a laundry list of other items. Here in Florida, it’s just a bad idea due to the high humidity and temperature in a vented attic and the condensation issues that can and usually does occur on the equipment.

Besides all of this, the IMC (International Mechanical Code) 2015 edition has some specific code requirements related to attic installation that you should be aware of. The IMC isn’t the “law of the land” and the final say on codes comes down the AHJ (authority having jurisdiction ) in your area, but in general the IMC is the basis for most local codes.

IMC 306.3 (2015) Appliances in Attics

This is a plain language paraphrase of the code

  • The opening needs to be large enough to remove the unit.
  • The opening/passageway must allow for unobstructed access.
  • The passage must not be smaller than 30″ high x 22″ wide and no longer than 20′ unless it’s at least 6′ tall and then no more than 50.’
  • Passageways must have a solid floor no less than 24″ wide.
  • The work area in front of the unit must have a solid, level floor of no less than 30″ x 30″ .
  • You don’t need a floor/passage when you can access/service/remove the unit from the opening itself.
  • There needs to be a light and an outlet by the unit with a switch located at the opening to the passageway.

Practical Considerations

  • Don’t ever cut trusses unless you have engineering that shows it is allowed.
  • If the unit is suspended make sure not to drill trusses in a location that will structurally compromise them. Follow manufacturer recommendations for proper mounting of the equipment.
  • In unvented attics take extra precaution to properly insulate drain lines/copper and seal unit penetrations to prevent moisture issues
  • Make sure that you CAREFULLY read manufacturer install instructions for horizontal installation and run test the system long enough in cooling to ensure there are no condensation issues. Coils and pans are OFTEN installed improperly in horizontal applications.
  • Install a secondary pan at least 3″ wider than the appliance (1.5″ in each direction) and condensate overflow protection to ensure that an overflow won’t result in MAJOR damage in accordance with IMC 307.2.3
  • When it comes to condensate in an attic CHECK EVERYTHING TWICE.
  • Be prepared with plenty of fluids and comply with OSHA confined space rules when applicable.

Mostly, avoid attic installs whenever possible and when required do them with care and prepare to do some extra prep work on the work area to comply with the code.

— Bryan

 

The term “short” has become a meaningless phrase in common culture to mean “anything that is wrong with an electrical device”.

A short circuit is a particular fault that can mean one of two things in technical lingo.

Any two circuits that are connecting in an undesigned manner. This would be the case if a control wire had two conductors connected together due to abrasion. Like a Y and G circuit “shorted” in a thermostat wire between the furnace and the thermostat. This would result in the condenser running whenever the blower is energized. This is disputed as to whether this is even a “real” short or not but is commonly referred to that way in the trade.

A short can also be described as a no-load path between two points of differing charges. This would be a traditional “short to ground” low voltage hot to common connection or a connection between legs of power without first going through a load of appropriate resistance.

Both of these conditions will result in something occurring that should not be occurring. Either something being energized when it shouldn’t be or fuses and breakers tripping or blowing or damaged components.

This is different than an Open circuit which is no path at all. So if a load has power applied and NOTHING is happening it is open. If power is applied and breakers or fuses trip or blow or something comes on at the wrong time or order, that is a short

Many techs advocate for using an ohmmeter to find a short circuit. We like that method but we often find that using the 24v as is and simply using a process of elimination to find the cause is easier for most techs as shown above.

 

— Bryan

If you work in refrigeration you may have heard the term “hot pull down”. This phrase is used to describe a condition where the load on the evaporator is above design due to the box temperature and/ or the temperature of the product in the box being higher than it would normally be.

My grandpa called me a few months back all upset “I just slaughtered a bunch of chickens and I’m going to lose all my meat because this freezer you got me isn’t working” he gasped into the phone. Now I had helped him pick out a commercial freezer a year or two back and he put it in his garage (a less than ideal location to begin with). What I had forgotten to mention to him was the importance of only loading with meat that was already down to temperature.

I showed up to look at it and sure enough, there sat a bunch of freshly slain birds PACKED into his freezer and the box temperature struggling to get below 15° instead of the 0° we really needed.

Most refrigeration equipment is designed to only maintain the temperature of the product, not to bring it down to temperature all at once, at least not in large quantities. This is due to two aspects of the design.

  1. Capacity – Most freezers and refrigerators just don’t move enough pounds of refrigerant to generate the necessary refrigeration effect to “pull down” warm product in a timely fashion. In other words, just like many A/C systems don’t keep up on a freak 98-degree day in Indiana, refrigeration equipment won’t pull down quickly if you add in more BTUs of heat than it is sized to remove.
  2. Coil Feeding Range – In the case of a cap tube or other fixed orifice metering device, the amount of refrigerant fed into the evaporator is directly proportional to the amount of refrigerant pressure differential between the liquid line and the evaporator. With a TXV the valve responds to superheat in order to open and close, opening as superheat rises and closing as the superheat falls. In a hot pull down the load on the evaporator is so high that the expansion valve goes wide open but still,  the coil “starves” or underfeeds refrigerant. This results in high superheat, high suction pressure and high head pressure but will also often result in low subcooling because so much of the refrigerant charge will move to the evaporator coil.

During a hot pull down the compressor will draw higher than usual amperage due to the increased density of the suction gas, this coupled with high superheat can result in compressor damage if it is allowed to run outside of specs for an extended period (Sporlan has a great piece on compressor overheating you can read HERE).

The conclusion is that most equipment should be allowed to get down to temperature before being loaded with product and the product should generally be at or near the design temperature. There are freezers and refrigerators that are designed specifically for “flash freezing” or pulling product down to temperature often called a “blast freezer”.

In the case of my grandpa’s freezer, we moved some of the meat around to other freezers and got it down in time to prevent salmonella… at least I hope so… I was feeling funny after Grandma’s chicken soup for Sunday dinner…..

— Bryan

 

Imagine a glass of ice sitting on a table.

Now imagine you place a lid on the glass so all the water and ice is contained in the glass.

If the ice and water are well mixed the water and ice will both be at 32°F because the ice is slowly changing state from ice to water which we call melting. Becasue this is happening at atmospheric pressure we can know what temperature this will occur at and the heat being transferred is going toward melting the ice rather than changing the water temperature which we call latent heat.

Let’s say the temperature in the room is 75°F. In this scenario, heat leaves the air molecules as they contact the exterior of the glass and heat moves through the glass into the water and ice. Becasue glass is a pretty good insulator this happens pretty slow but this heat still moves from hotter to colder.

This movement of heat from the air to the exterior of the glass transfers THROUGH the glass via conduction.

What happens if we blow air toward the glass? what changes? 

If we move more air over the side of the glass we deliver more air molecules to the glass via convection but it doesn’t change the fact that the heat makes it through the walls and into the glass via conduction.

By delivering more air to the glass we warm the outside of the glass more which causes the water melt inside the glass faster, in other words more air over the glass means more heat transfer even though we didn’t change the temperature of the water or the air.

This same basic thing happens inside an evaporator and condenser coil, when we increase the flow of air we also increase the transfer of heat through the walls of the copper tubing in the coils. In the condenser more airflow increases the heat rejection out of the refrigerant and in the evaporator more heat is gained.

Because the refrigerant circuit is dynamic (refrigerant moving) and under pressure more or less heat entering or leaving the system impacts the process and changes the pressures of the refrigerant inside.

If we move less air over the condenser the pressure on the high side increases, if we reduce the air over the evaporator coil less heat enters the circuit, and pressures drop.

This is a basic picture for you to consider next time you see high or low system pressures and how coil airflow impacts heat transfer.

A more advanced but similar thought experiment is what would happen if the evaporator coil had no fins.

— Bryan

Before I start on this one… At HVAC School we focus on a wide range of topics, many of them are very basic. My experience as a trainer for over 16 years has taught me that no matter what I assume others SHOULD know, it doesn’t change that fact that they often do not. This write up is very basic but you may find that some of the content will be useful for you to give apprentices or junior techs or it may give you a new idea of how to explain it to them… or maybe not. Either way, I feel an obligation to cover even the most basic concepts in the trade to help ensure that nothing gets missed. 

Thanks for understanding.


Before reading this you need to understand some of the terms surrounding air conditioning charging and diagnosis, specifically the term saturation

Next, you need to know something of the basic refrigerant circuit, I suggest that you understand these words and concepts before you ever dive into attempting to charge an air conditioner.  Many who start here may ask “what should my pressures be”, this is NOT how you charge a system so if you are reading this to try and find that answer just be aware, it isn’t that simple.

READ THE MANUFACTURER SPECS ON PROPER CHARGING FOR THE MODEL YOU ARE WORKING ON FIRST WHENEVER POSSIBLE

In order to set a proper charge on an A/C system, you must first know the type of metering device.  The piston / fixed orifice type system primarily uses the superheat method and the TXV / EEV primarily uses the subcooling method.  When setting a charge, it is always preferable to set the charge in cool mode.  Whether you set the charge in heat or cool mode, you should always follow the manufacturer’s recommended charging specifications.  In this section, we will discuss manufacturer-recommended charging and some indicators that you have set a proper charge in heat mode.

But first, There are some things that Trump these guidelines and should make you stop and do more diagnosis

A properly running A/C system with indoor and outdoor temperatures above 68 degrees will have a suction saturation above 32 degrees (freezing), don’t leave a system with a below 32˚ saturation suction without doing more diagnosis even if the superheat/subcool looks correct.

If you see a liquid line pressure that is more than 30 degrees saturation above outdoor temperature (like a 440 psi liquid pressure on an R410a system on a 90 degree day), do not proceed until you have further addressed the possible causes of high head, regardless of what the superheat or subcool might be reading.

Always purge your hoses to prevent introducing air into the system and never mix gauges when using low loss fittings and different types of refrigerants.

Charge in the liquid phase (tank upside down) and add the refrigerant slowly and carefully to ensure you do not flood/slug the compressor with liquid refrigerant. You can do this by watching your manifold sight glass or using a special liquid preventing adapter such as the Imperial 535-C Kwik Charge.

These precautions will prevent causing system damage.

Also, at a minimum doing a full visual inspection of the equipment including

  • Inspect filters
  • check blower wheel
  • check evaporator coil
  • check condenser coil cleanliness
  • make sure the system is wired properly and running in the correct mode

Note: This is only a basic guide for charging. There are innumerable conditions that can alter refrigerant pressures, superheat, subcool and saturation that are not related to the refrigerant charge. This is not intended to cover the complete diagnosis of the refrigerant circuit. 


Superheat Charging

To charge a system using superheat, you will need to monitor the actual temperature of the low-pressure suction line, the saturation temperature of the low side suction gauge and the indoor and outdoor temperatures entering the unit(s).

Most if not all manufacturers have a charging chart available with their respective units.  With the information you have gathered on indoor and outdoor temperatures, you can calculate the recommended superheat or in a pinch, you can use a superheat calculator such as the Trane superheat calculator or a free app like our superheat calculator or even better the MeasureQuick app. A good calculator will require that you determine the wet bulb temperature in the return air stream.  Without a sling or digital psychrometer or hygrometer, you will not be able to determine wet bulb temperature.

Once you know the target superheat you can adjust the system charge to hit it. Let’s say, the recommended superheat was 18 degrees, you would add/remove refrigerant to the system until the actual temperature of the suction line was 18 degrees above the indicated saturation temperature from your low-pressure gauge. Adding charge will decrease the superheat and recovering refrigerant will increase the superheat. 


Subcool Charging

To charge a system using subcool, you will need to monitor the actual temperature of the liquid line and indicated saturation temperature on the high-pressure gauge.  Information on the entering temperatures is not necessary to charge the unit by the subcooling method.

Most manufacturers have recommended subcool charging information with the units if it is designed for a TXV (TEV).  If for some reason, there is no information with the unit, or if it has worn off, you can set a typical residential air conditioner charge to 10 to 12 degrees of subcooling which is a relatively safe range to use.

Let’s say for example the manufacturers recommended subcool is 14, you would add enough refrigerant to the system so the actual temperature of the liquid line was 14 degrees less than the saturation temperature, as indicated on the high-pressure gauge for that particular refrigerant. Adding more refrigerant will increase the subcool reading and recovering refrigerant will decrease the subcool reading. 


Approach Method

 Lennox factory information asks that we charge by the approach method on TXV systems. I suggest charging to at least a 6˚ subcool before even attempting to calculate the approach method. 

The approach method is a calculation based on the relationship of liquid line temperature to outdoor temperature.  To calculate approach, subtract outdoor ambient from actual liquid line temperature.  The outdoor temperature used to calculate approach should always be taken in the shade and away from the hot condenser discharge air. To increase the approach differential you would remove refrigerant to decrease it you would add refrigerant. 

Some Lennox heat pump systems come with a subcool chart next to the approach chart. This subcool chart is for < 65˚.  This means the subcool chart is only valid when the outdoor temperature is below 65˚.  Follow the instructions on the unit carefully when charging in subcooling in <65˚ temperatures.  The method requires that you block sections of the coil to achieve higher head pressures before setting by subcooling.


Heat Mode Charging for Heat Pumps

In most, if not all, cases you will charge a unit in heat mode according to the manufacturer’s recommendations.  In those cases where no information is available, there are other indicators that you may use to set a proper charge in heat mode.

First, make sure you switch your hoses so the suction gauge is reading off of the “common suction” port that taps in between the compressor and reversing valve. You may put your high side gauge on either the discharge or liquid (on most systems) depending on what you are checking.

Before doing any heat mode charging use common sense, if installing a new system the best bet is to calculate line distance and weigh in any additional charge before moving on to the detailed testing phase.

The first one is the 100˚ over ambient discharge temperature rule.  The general rule to this is that a properly charged unit will have a discharge line temperature of 100˚ above the outdoor ambient temperature but this only a rule of thumb and cannot be relied upon.  If the discharge line is too hot. you would add refrigerant which would lower the discharge temperature.  Alternately, if the discharge line were too cool, you would remove refrigerant to raise the discharge temperature.  This rule is to be used only as an indicator and, in some instances, may not be accurate given some other factors such as dirty coils, excessive superheated refrigerant entering the compressor, etc.  

Another common rule of thumb is suction pressure will be close to the outdoor temperature in an R-22 system, this is totally a fluke and has no scientific basis other than it just generally tends to work out that way. this means that on a properly functioning R22 system if it is running in heat mode and its 40 degrees outside the suction pressure tends to be around 40psig. This guideline obviously doesn’t work on an R-410A system or any other refrigerant.

A more applicable guideline is 20˚- 25˚ suction saturation below outdoor ambient temperature. This means if it is 50˚ outside the suction saturation temperature would generally be between 25˚and 30˚on a functioning system.

Remember that in heat mode the colder it gets outside, the lower the suction pressure and the hotter it gets inside, the higher the head pressure.  Since the roles of the coil are reversed in heat mode, if you notice an abnormally high head pressure it may be due to a dirty air filter or evaporator coil.  A dirty condenser coil would cause the suction pressure to drop below normal and also cause superheat problems.

Once heat mode a charge is set, whether by manufacturer specification or an alternative method, you can still verify the subcool and superheat on the unit in some cases.  Do not confuse the superheat or subcool methods recommended by the manufacturer though when running in heat mode.  These are only used for setting the charge in cooling mode and not in heat. Look for heat mode specific or low ambient guidelines. 


 

Finally and most importantly is ALWAYS TEST EVERYTHING. Airflow, Delta T, Superheat, Subcool, Suction Pressure, Head pressure, Amps, Incoming voltage, Filter etc…

Read manufacturers specs, understand the units the units you are working on, only then will guidelines and rules of thumb help instead of hinder you.

— Bryan

 

 

There has never been a more complicated and confusing time surrounding refrigerants that what we are in right now.

We are seeing flammable HC (Hydrocarbon) refrigerants with increasing regularity and EPA rules that just changed appear to be changing again

With all this tumultuous change it’s important to know what to look for in refrigerants and what makes a good refrigerant in the first place.

A good refrigerant –

  • Has high latent heat of vaporization (it moves a lot of heat per lb when it boils)
  • Boils and condenses at temperatures we can easily manipulate with compression (the pressures work)
  • Mixes with the oil appropriately so that the oil can do the job of lubrication in the compressor as well as return.
  • Doesn’t blow stuff up or catch on fire
  • Doesn’t poison people
  • Doesn’t hurt the environment

That pretty much sums it up

Because we have seen increased environmental regulations over the last 25 years there has been a push to find good refrigerants even if it means going into the flammable and toxic spectrum.

Thankfully, refrigerants are well marked and so long as we pay attention and follow best practices there shouldn’t be any issues.

The markings are pretty simple

A refrigerants have low toxicity

B refrigerants have high toxicity

1 refrigerants have low flammability

2L refrigerants are only “mildly” flammable

2 refrigerants are low flammability but higher than 2L

3 refrigerants are highly flammable

The most common toxic refrigerant is Ammonia and you would generally only find it in old appliances or in large industrial applications.

Propane (R290) is a flammable refrigerant and it is becoming quite popular in small self-contained refrigeration units like vending machines and reach-in coolers. These propane units will be very clearly marked and should be handled with extreme caution, especially when electrical sparks or open flame are or could be present.

True Refrigeration has some good training materials on R290 such as this video

As refrigerants become more toxic and flammable it becomes more and more important that we evacuate the system properly to get oxygen out of the system and that we make sure the systems are free of leaks.

Skilled and well-trained techs will ALWAYS be needed in our trade and never more than now.

— Bryan


Most motors are designed to set amount of work, usually rated in either watts or horsepower, which is  746 watts per HP.

Watts law states that Watts = Volts x Amps. If a particular motor needs to do 1 horsepower of work at 120 Volts it will draw about 6.22 amps. And yes in an inductive load like a motor it’s not quite as simple as VxA=P but we are keeping it simple here.

A motor designed to do the same amount of work (1HP) at 240v will draw half the Amps (3.11).

This does not make the second motor “more efficient” because the power company charges by the Kilowatt NOT by the amp.

) If you take a load that is designed for a particular voltage and you DROP the voltage it will also decrease the wattage according to Watts law (Watts = Volts x Amps) as well as decrease the amperage according to Ohm’s law (so long as the resistance remains the same).

Let’s say you take a 5KW heat strip that is rated as 5Kw at 240v and you instead connect it to 120v.

It would then only produce 1.25 kw and draw 1/4 the amps, this is because while we may call it a “5 Kilowatt heater” it is actually just a fixed resistor designed to do 5 kilowatts per hour of work in the form of heat at 240 Volts. Cut the Volts in half you also cut the amps in half and you decrease the amount of work done down to 1/4 because Watts = Volts x Amps.

— Bryan

 

Callbacks are horrible… They kill the trade from every possible angle in ways that are hard to fully quantify or make up for. They destroy customer satisfaction, reduce technician morale by causing long hours resulting in unprofitability for companies and less earning opportunity for everyone. Possibly worse of all, callbacks tell customers that you are no better than their cousin the maintenance man or the $35 an hour Craigslist tech. If they wanted to call someone back they could have just called them instead of a true pro.

Callbacks make me furious!

They have always made me furious. Back when I was a tech there was NOTHING I hated more than having a callback… Wait… I take that back, I hated being accused of a callback when it wasn’t a callback in my mind even more.

Since those immature days of pitching a fit whenever I got a callback, I have come up with my definition of what is and isn’t a callback.

Callbacks Are – 

  • Anytime an installation or repair error is made either due to overlooking a problem or doing it incorrectly, regardless of how long ago it occurred
  • When a customer calls back for a similar issue on the same piece of equipment within 30 days, even if it isn’t the exact same problem
  • Cases where the customer cannot be charged for the work performed due to its relationship to prior work
  • Calls back out or complaints due to a failure to communicate, diagnose or repair completely

What we have learned is that the only way to reliably prevent callbacks is to come up with systems and processes that actively PREVENT callbacks rather than assuming that if you are a good tech they won’t occur. Often we would blame the customer, the follow-up tech or faulty parts for callbacks when it was actually within our power to prevent if we were more proactive. Here is what we learned.

Look Around More Carefully

Before you start diagnosis with tools look over the equipment for anything abnormal. Strange sounds, signs of abnormal condensation and oil spots can all be signs of trouble.  Look for wire rub-outs, loose connection and arcing. If it looks like work was done recently, double check that the correct parts were used and that they were installed properly. If wires are a mess, electrical connections exposed, refrigerant lines rubbing out or severe corrosion/deterioration on critical metal parts it should be addressed with the customer.

Never just fix the first problem you find and leave. If that’s all you do you won’t have a low callback rate and you will miss opportunities to serve the customer better. In my experience, the vast majority of systems have either initial installation/commissioning deficiencies maintenance issues, abrasion concerns or just plan faults that get missed when the tech fixes only the first and most obvious problem.

Diagnose More Precisely 

The proper and full diagnosis of HVAC/R equipment isn’t that difficult if you are using the proper tools and techniques, but we still hear techs say “it should be fine” when looking at a charge or “That looks pretty normal” when taking an amperage reading. These aren’t things that a good diagnostician guesses at, it is either within design specifications or it is in need of repair, alteration or upgrades and the customer needs to be communicated about it. KNOW the target evaporator DTD, condenser CTOA, motor RLA and system design capacity vs. delivered capacity for the piece of equipment you are working on. If you don’t know what these things mean then start HERE and download the MeasureQuick app to help.  Once you stop guessing you will get it right the first time more often and prevent some nasty callbacks.

Improve Your Workmanship

Most bad workmanship is due to poor training, tools, supplies and real or perceived time constraints. You always have time to do the work correctly or you need to FIND time to do it again. None of us get everything right, but you can work to improve your workmanship with every job you do whether it is how you make a wire connection to how to connect ducts or making a flare that never leaks. Get it right the first time and leave it looking like a pro did it instead of a handyman or a kid fresh out of trade school.

Keep the right tools and materials on your truck to execute great workmanship and then do it a little better each time based on what you learn along the way.

Communicate Completely 

  1. Communicate with the customer when you arrive and listen carefully to understand ALL of their concerns, not just the obvious ones and not just the ones that are easy to repair. If the customer is concerned about a high power bill, a noise, an odor or a warm room…. INVESTIGATE IT
  2. Explain your diagnosis process to the customer before you begin working. Let them know that you will check the system as completely as possible and bring them results of your findings before you proceed with any repairs.
  3. Once you find and note any and all issues ask them if you can show them your findings and either bring them to the points of interest if practical or show them photos on your phone or tablet. Do not use fear, negativity or drama to present the issues, be factual and to the point about the issues and prices to repair. Once the customer approves or declines each item let them know you will make the desired repairs and retest to ensure that there are no additional concerns once the system is up and running.
  4. Once you are done with the work make sure to reiterate any remaining issues that they did not approve and get them to sign an invoice or document that clearly shows what was and what was not done. Once this is complete ask the customer if they are satisfied with the service and if there is anything else you can address for them before you leave. Make sure to reiterate what you left the thermostat set to and what they should or should not expect from equipment based on the repairs made. If the customer does not have a maintenance plan in place make sure that their paperwork includes a suggestion of maintenance and that you discuss the importance or proper maintenance to the customer.
  5. Fill out your paperwork fully and clearly with all work performed, and work declined and any condition issues on the equipment. Be detailed about which unit you were working along with proper model and serial numbers.

If parts are required make sure to get photos of EVERYTHING you can find, data tags, parts tags, boards, compressor model and serial etc… going back to a call just to get a model # because it was missed or written down wrong is a huge waste of time.

Eliminate the Careless Errors

Walk the job before you leave and put your tools away in their proper place. This will help prevent leaving disconnects out, caps off, float switches tripped, thermometers in the duct, screwdriver on the roof etc…

Some of you are just more prone to these sorts of careless mistakes but that is not an excuse, you just need to come up with systems that prevent these forgetful errors. Here are the best ways –

  • Create a checklist you go over at the end of every call that you review before you pick up your keys and put them in the ignition.
  • Don’t talk on the phone, text or look at social media while on a call. Create a Do Not Disturb rule on your phone during the work day so that it only rings if the person calls twice in a row. Let your loved ones, manager and dispatch know that they will need to call twice to get you if it is urgent.
  • Force yourself to put tools and parts in the same place every time so that you can tell very quickly if you left or forgot anything.
  • Never leave in a rush. Finishing a call is never as simple as hopping in the van and peeling out. Follow a process and think through the job before you pull away. Don’t be in a hurry to “get away before the customer walks out and asks another question”, that sort of thing will get you in big trouble.

Gut Check

The final test is a gut check. If your gut tells you the diagnosis isn’t right, you didn’t make the repair right or the customer isn’t 100% understanding what’s going on then please DON’T LEAVE. 

I know it can be tempting especially after a long day or an especially difficult call or customer but trust me, leaving never makes it better. Hang in there, read up on the system, perform more tests, check the ducts again whatever you need to do but don’t bail.

Sometimes you will have a customer that you just know is going to turn around and call back. You can tell they aren’t listening to you about your findings or they have a misunderstanding about the system operation. These are the ones you want to MAKE SURE you get your recommendations in writing, clearly spelled out with a signature.

If you really want to ensure it doesn’t come back, spend 15 extra minutes and write them a nice, positive email and copy your dispatcher and your service manager with a description of what you found, what you recommended, what you repaired, any system condition issues and how they should expect the system to operate with photos attached.  It will really reduce those immediate callbacks from difficult customers.

  1. Observe the entire system

  2. Diagnose all the issues

  3. Test the system fully

  4. Communicate through the entire process

  5. Follow a process to ensure you don’t miss anything silly

— Bryan

 

 

 

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