How To Troubleshoot HVAC/R Tools

Gary McCreadie is an HVAC tech, the creator of hvacknowitall.com and the HVAC Know It All Podcast

A Normal Information To HVAC/R Troubleshooting

This can be a basic information to HVAC/R troubleshooting.  We cannot be entering into specifics that contain native codes, OEM procedures and pointers or in-depth evaluation of issues like static stress, superheat or sub-cooling. However, it’s crucial as a technician that you simply perceive fundamental refrigeration/heating and electrical fundamentals with a purpose to safely perform a correct analysis.  In case you are presently studying the fundamental rules, I extremely advocate that you simply talk with a senior technician throughout your service, if that luxurious is obtainable or get entangled with the robust technician tradition on the subscription primarily based HVAC Know It All app.  This text will deal with a some hurdles that should be crossed earlier than the subsequent step of troubleshooting can happen.  

Technicians ought to contemplate themselves expert commerce detectives, gathering information from numerous locations.  Some service calls take a couple of minutes, some can take a number of hours or days relying on the complexity of the issue.  

Professional Tip: Earlier than we start troubleshooting, make sure that the suitable PPE (private protecting tools) is put into place, security glasses, gloves, and so on.

This text is complimented by a podcast episode discussing HVAC/R service.  Hear on the HVAC Know It All Podcast 

Diagnostic Instruments

To be able to perform a analysis of any system there are instruments that will probably be wanted through the course of. One or a mix of the instruments under will allow you to create a giant image snap shot of the issue at hand, let’s undergo them one after the other.  

Manifold Gauges

A compound set of manifold gauges are used to check system pressures of an air con or refrigeration system.  In addition they provide you with a sign of the saturated temperature for every refrigerant, in case your manifold gauge doesn’t embody a scale for the refrigerant you might be engaged on, you have to to make the most of a stress/temperature chart for that specific refrigerant.  Another choice is utilizing a digital equipment within the type of a manifold set or good probes.  Digital gauges implement stress/temperature charts inside and may be learn on the show display or, they’re calculated utilizing a cellular utility. 

This video explains test evaporator superheat utilizing good probes https://youtu.be/_fOKKGdYBZo

Temperature Probe or Clamp

To be able to test superheat and subcooling of a system, you have to a temperature sensing gadget that may be mounted on the refrigerant traces of the system. 

Multi Meter

I good multi meter will probably be used essentially the most on any given service name, as most issues are usually associated to electrical points.  A multi meter or mixture of meters ought to be capable to test AC/DC voltage, amp draw, resistance within the Ohm setting, capacitor micro farads and DC micro amps of a flame sensor for fundamental troubleshooting functions.  

Take a look at the video testing flame sign utilizing DC micro amps https://youtu.be/gV7vjjtpJ5c.  Additionally try the video troubleshooting a stroll in cooler condensing unit utilizing completely different meter capabilities https://youtu.be/cfUUr0J8q3w.

Twin Port Manometer

A manometer serves a number of capabilities like checking gasoline stress of a heating equipment, differential stress throughout coils and filters and checking static stress of duct programs.  

Current day manometers enable for choices, we are able to select a manometer with a show display or a manometer that hyperlinks to a cellular gadget by way of Bluetooth.  Listed below are two movies displaying each sorts in motion within the discipline https://youtu.be/tsLgkRaEyBY and https://youtu.be/a5SR4Ys6Fsk.

Digital Refrigerant Leak Detector 

To seek out leaks inside a refrigeration system successfully and rapidly, a high quality digital leak detector can be utilized to take action.  

You will need to use a mix of an digital leak detector and cleaning soap to confirm the presence of a refrigerant leak.  This text explains intimately the process. https://www.hvacknowitall.com/blogs/weblog/164736-refrigerant-leak-checking-procedure#.X7bF_WlyaDY.

Hygrometer 

A hygrometer measures temperature and humidity and may give readings like moist bulb temperature and dew level relying on the model.  This can be a great tool to test outdoors and indoor air circumstances in addition to provide air and return air. 

Checking room circumstances utilizing a digital good probe and cellular app.

Another instruments to notice which are used for diagnostic functions embody:

• Combustion Analyzer

• Infrared Temperature Gun

• Thermal Imager

• Rotating Vane or Scorching Wire Anemometer        

Sequence Of Operation

Earlier than we dive into the steps of strategy and work by means of a service name we have to perceive tools sequence of operations, what occurs first after which what occurs subsequent.  For an instance of sequence of operations we’ll use a residential furnace. 

1. A name for warmth is created from the thermostat.

2. The induced draft motor begins and air move inside the combustion chamber should be proved by a stress change.  The induced fan runs a timed pre-purge of the burner and venting. 

3. The ignition management is powered, offering that every one security switches are closed.  

4. The technique of ignition is enabled (spark or scorching floor ignitor), the gasoline valve opens, the burner lights and ignition should be proved. 

5. The burner stays lit and blower fan begins after a time delay to permit warmth the exchanger to heat up. 

6. The thermostat satisfies and the burner shuts off after the gasoline valve is powered down.

7. The induced fan motor runs a publish purge of the burner and venting.

8. The blower fan runs a timed calm down of the warmth exchanger.  

Take a look at this video transferring by means of the steps of a no warmth name.

It is essential to grasp that there are numerous forms of tools which will make the most of completely different sequences, it is your job because the technician to know this earlier than continuing.  Utilizing manuals and or tech help is usually a good place to start out in acquiring this information.  

Professional Tip: Understanding wiring diagrams is crucial to troubleshooting and understanding sequence of operations.  It’s suggested you grow to be an professional at studying and comprehending wiring diagrams to troubleshoot safely and successfully.  

Normal Troubleshooting Steps

Step One: Buyer Communication 

If doable, attain out to the client earlier than heading out, have them clarify to you what is going on, probably have them file a video or take an image, from a distance, so that you can reference while you arrive on website.

Be aware:  Don’t ask a buyer to transcend this, for instance, haven’t got them open panels, reset limits, and so on.  Do not put your buyer’s security in danger.  

As soon as en route, “DO NOT”, create eventualities in your head of what could be incorrect, too many fall into the lure of pre diagnosing tools earlier than arrival and instantly try and show their guess is right.  As a substitute, use a methodical strategy, begin from the start to make sure nothing is missed.  Crank up the radio or hearken to the HVAC Know It All Podcast 😉 and maintain your thoughts free and clear.  

When you arrive, analyze any information the client has gathered for you.  Learn how lengthy the difficulty has been current, when it occurs, the place it occurs, and so on. it will allow you to type a sample of the potential points.  If the client has entry to archived pattern logs that present ambient temperature/humidity or provide air temperature for instance, ask to see it!  

Professional Tip: DO NOT settle for a buyer analysis of the difficulty, you’re the skilled, it is your job not theirs to troubleshoot.

Step Two:  Examine Utilizing Your Senses

Be aware: Earlier than getting into right into a mechanical room, crawl house, basement or attic the place gasoline, propane or oil fired tools is getting used…contemplate sporting a private carbon monoxide monitor to make sure your security.    

Earlier than utilizing any diagnostic instruments, visually examine tools, search for apparent issues that may be rectified earlier than persevering with.  For instance, a grimy condenser coil, unfastened or defective wiring connections or improper venting.  We will take this a bit additional to incorporate different senses like listening for odd sounds, smelling for burnt windings, or utilizing our fingers to really feel for vibration, or to get a sign of pipe temperature.  As a reference, the palm of a human hand is roughly 92⁰ Fahrenheit.  Something that feels hotter than your hand is hotter than 92⁰F and the alternative additionally stays true.  

Professional Tip: Earlier than reaching into unit cupboards, guarantee energy has been disconnected and verified with a multi meter and lock out tag out the place vital. 

Step Three: Verifying Energy

After preliminary inspection of apparatus, we should take a look at our major energy supply, with out the proper energy, we won’t transfer ahead.  If energy shouldn’t be current, examine the ability supply for a tripped breaker or open fuse.  If for instance, the breaker is tripped, we might have a brief inside the wiring or major load inside the equipment. This should be rectified earlier than continuing. 

Be aware: An instance of a major load is a motor or compressor that accepts energy from the first supply that’s fed to the tools.  Instance, a condensing unit’s major energy could be 208/230 that’s fed immediately from the breaker panel.  

Professional Tip: Earlier than restoring energy on the primary supply (breaker or fuse panel), make sure the native disconnect is off on the equipment.  If the breaker journeys or fuses blow when re-applying primary energy, we’ve dominated on the equipment being the foundation trigger. 

As soon as major energy has been restored and is right, we have to confirm the presence of management voltage or secondary voltage.  Management voltage can exist in lots of varieties, for instance 24v, 120v, 208/230v and is normally fed from a step down transformer. For this text we’ll assume 24v.    

Professional Tip: In case you are coping with major energy points (breaker tripping when tools begins to run).  It’s  advisable to drag the “R” wire from the equipment low voltage terminal strip till the problems are resolved.  It will forestall tools from making an attempt to start out up through the troubleshooting course of.  

Now that we’ve confirmed that the first and secondary energy sources are right, we should test our technique of management, this might be a easy thermostat or a barely extra difficult constructing automation system.  Make sure the controller is powered up, useful and set accurately.  

Professional Tip: Defective thermostats can typically be identified by bypassing them.  For instance, if the thermostat is asking for cooling and the show signifies a name however the tools hasn’t began, pull the thermostat from the sub base and quick (bounce out) “R” and “Y1” on the sub base.  This take a look at removes the thermostat from the equation.  If the tools begins up, typically, the thermostat has failed.  

Step 4: Warmth Change Medium

If we’ve improper airflow, we cannot trade warmth because the system is designed to do.  The identical lies true for move of water/glycol.  Solely distinction is, air makes use of a fan and fluid makes use of a pump.  We should guarantee we’ve the proper air move or fluid move earlier than the subsequent step of troubleshooting can happen.  Make sure the fan or pump is powered, operating and most significantly rotating within the right path.  Make certain air filters and inline strainers are clear.  In worst case eventualities, system balancing might made have to happen to acquire the proper move.

Till we are able to show the proper move of our warmth trade medium, it’s a good suggestion to maintain the system off because it pertains to heating or cooling.  

Professional Tip: If the fan or pump doesn’t begin on a name, additional troubleshooting will should be finished.  For instance, checking incoming energy to the load and guaranteeing it’s right, checking capacitors if utilized and relays or contactors. If the pump/fan is discovered to be defective, it should be modified earlier than continuing. 

Professional Tip: If the system makes use of a relay board, you have to to make sure the board is receiving an enter (a name) and conversely relaying an output sign.  In a variety of circumstances if the board is receiving an enter and never offering an output, underneath regular circumstances, the board is normally faulty and can want changing.

Step 5: Full System Diagnoses 

We’ve got obtained information from the client, rectified visible defects, ensured the proper energy and name for heating or cooling and ensured move of our warmth trade medium.  What’s subsequent?  For this instance, we’ll focus on a cooling analysis.

We’ve got a name for cooling and the compressor/condenser fan contactor doesn’t pull in, what’s subsequent?  

• Examine the security circuit for any open switches.  For instance, open low or excessive stress switches will maintain up the move of energy to the contactor coil.  Additionally, some items might make the most of interlock circuits to make sure a pump or fan has began, an interlock is normally a usually open contact that closes as soon as move is proved.  

Professional Tip: If the pump or fan is operating and you’ve got decided move is right however the heating or cooling will not interact, the interlock change could also be caught open, if it has one. 

• If the security switches and interlocks are closed and the compressor/fan contactor is receiving 24v throughout the coil however the contactor won’t pull in confirm that the contactor coil shouldn’t be open or faulty.  

Professional Tip: Our multi meter on the ohm setting is used to test winding resistance.  If the meter reads OL throughout the coil, the coil is open and faulty.

Professional Tip: If the low voltage widespread is misplaced or damaged inside the circuit.  Either side of the contactor coil will learn 24v to floor with a multi meter on the volt setting. The damaged widespread should be rectified earlier than transferring on.  

The compressor/condenser fan contactor pulls in and nothing occurs, what’s subsequent.  

• Make sure that the proper energy is passing by means of the contactor to every load.  For instance, if the compressor is 208V, guarantee it’s receiving 208V.  

Professional Tip: On a single section system, the C (widespread) and R (Run) terminals on the compressor are the place the first voltage is offered and checked by making use of your meter leads throughout them.  On three section programs, you could test throughout T1-T2, T1-T3 and T2-T3 and have the proper major voltage on all three phases.   

• Test capacitor MFD’s and begin elements for any defects.  

Professional Tip: If the run and begin windings are reversed on the capacitor it may well trigger the motor to show in the other way.

• Test motor windings to make sure they don’t seem to be open, remember the fact that a shorted winding might in actual fact journey the breaker or trigger a fuse to blow.  

Professional Tip: If any elements are discovered to be faulty at this level, we should change them earlier than persevering with.  

The compressor and condenser fan motor begin as soon as powered, what’s subsequent?  

• Test amp draw of every element to make sure it is inside it is identify plate ranking.
• Test system efficiency utilizing gauges, test system saturated condensing temperature, saturated suction temperature, superheat and sub-cooling and guarantee they fall into the design parameters of the system.  

Professional Tip: If utilizing digital gauges corresponding to a Testo 550 or Good Probes, they hyperlink to the meausreQuick app.  measureQuick can carry out a non invasive take a look at with out the necessity for checking pressures or may also assist diagnose a system with producing targets that should be met. 

There are lots of different apps and instruments obtainable to assist with system diagnoses.  A very good service technician will keep open minded and use the instruments which are obtainable to them.  It is essential to grasp that assuming an consequence will not work, we should confirm by means of testing and are available to the proper conclusion.  An unverified analysis will result in a disturbing go to to the components counter, as you might be guessing or making an assumption as to what the issue actually is.  

In Abstract 

Keep in mind, this can be a basic information to HVAC service, you’ll have to put within the work and procure the information to hold out these duties.  To summarize the article:  

• Technicians ought to contemplate themselves expert trades detectives.
• Fundamental and superior diagnostic instruments will assist with a giant image analysis. 
• Understanding sequence of operations and wiring diagrams is a should.  
• Steps to a service name embody, buyer communications, inspection with the senses, correct energy, right move of warmth trade medium, after which ultimate analysis.  Make certain the analysis is verified 

For those who’re fascinated about getting into the HVAC/R trades, otherwise you’re an apprentice or helper, try this video to offer some useful motivation.  

Good luck and glad HVACing!  

Gary McCreadie 

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