Month: November 2017

Beware of “Ghost” Voltage

This article serves two purposes. First, it is an article for technicians who have heard of the dreaded “ghost” voltage but never understood why it happens. Second, for my own apprentices and techs who I stumped this morning with a diagnosis problem that involved “ghost” voltage that they were unable to diagnose.

If they read my tech tips they will get the answer… sneaky right?

So what is meant by ghost voltage?

In some cases, you will be diagnosing an electrical issue, usually controls / low voltage issue. You will be measuring potential on a circuit and then when the circuit is connected to the load the voltage will disappear … like a “ghost”.

For example, you make be measuring 24v at a condensing unit on the “Y” contactor circuit when the conductor (wire) is disconnected, but as soon as you connect it to the contactor/control board the voltage “disappears” when measured across the load (across the contactor coil) or more simply from Y to C.

In other cases the voltage may not disappear completely, it may just drop way down, or in other cases the contactor may chatter, circuit board lights dim etc…

I have heard all of these situations called “ghost” Voltage, but they are actually just voltage drop and these symptoms are caused by additional resistance in the circuit OTHER than the designed load.

Quick Note: there are also “induced” voltages that can appear as ghost voltage due to conductors running in parallel with other current carrying conductors. This is more common in Commercial and industrial applications where many wires are bundled or in close proximity over long distances. These charges are usually small and often “disappear” under load.

Rarely do we want more than one electrical load (resistance point) in a single circuit. When this does occur it is usually undesigned and caused by of long wire lengths, improperly sized wire and poor connections.

Now to CLARIFY, when referring to a circuit we mean one complete path between electrically different points (say L1 and L2 in single phase 240 or 24v hot to 24v common on a control transformer). Some think of parallel circuits as a single circuit, but while they may share conductors they have an individual load path.

To cut to the chase, whenever wire is undersized, runs of wire are too long or the circuit contains poor connections there will be additional resistance introduced to the circuit. When there is more resistance added in places other than the load (in this case a contactor coil) there will be a voltage drop and therefore the voltage applied to the load will be decreased. When a wire isn’t connected to the load this drop will be invisible because the load isn’t in the circuit and therefore you are simply reading across the OTHER, unintended load (resistance) which will often be the full voltage depending upon the exact issue and when you are making the measurement.

In every complete and independent circuit, including a series circuit, the amperage is the same no matter where in the circuit you measure it. Before the load, between loads, after the loads… it doesn’t matter. The amperage is dictated by the total applied voltage and the resistance (or more accurately the impedance) of the entire circuit.

The voltage applied to each load is dependant on the resistance of the load in comparison to the total resistance of the circuit. In the example below, you can see that the amperage is the same on each load and is dictated to be 500 microamps because the total circuit ohms is 18,000.

The voltage drop of each load in series is equal to it’s percentage of the total circuit resistance. Since  loadR1 is 16.5% of the total resistance in the circuit, the voltage drop across R1 is 1.5V because 1.5 is 16.5% (0.165) of 9V.

There are a few other factors that make the trouble with voltage drop worse. Let’s say you use an undersized wire to feed a lightbulb, an undersized wire means that the conductor has a lower ampacity (amp capacity) than it should have. Once the circuit is energized the wire will begin to heat up, as it heats up the molecules in the wire begin moving faster which increases the resistance of the wire. The greater the resistance of the wire the greater the voltage drop across the wire resulting in a hot, dangerous wire, increased voltage drop at the bulb, less light from the bulb and decreased circuit amperage (less total work being accomplished).

In the case of many loads including inductive (magnetic) loads like a compressor contactor, the resistance in the coil isn’t just resistance you can measure with the contactor de-energized. This resistance that is created within an electromagnet once it is energized is called “inductive reactance” and it is measured in ohms of impedance. In order for the contactor coil to properly engage it requires the correct applied voltage and without the properly applied voltage, the resistance of the coil remains low. The crudely drawn diagram below (I’m no artist) shows a contactor coil circuit with no issues and a 0.5 amp  current at 48 ohms

When you add in a 200 ohm “bad connection” or any other type of resistance, not only does it create huge voltage drop, it also drops the impedance of the contactor coil itself with the result being a very low applied voltage (3.13V) on the contactor coil with it connected and under load. Under these conditions, the contactor won’t try to pull in at all. Under less extreme conditions it may chatter or become noisy.

Now, this is a hypothetical situation, but you will notice that the poor connection is AFTER the contactor coil in what we call the common circuit in 24v controls. It doesn’t matter WHERE in the circuit resistance is added, whether before the switch (in this case a thermostat) in the line side or after the switch on the load side. It could even be in common or in the switch itself.

Anytime additional resistance is added to a circuit it results in voltage drop when the circuit is intact. When we disconnect wires to test voltage or test voltage with a circuit that has an open switch we can create confusion and observe “ghost” voltage. In reality it is simply extreme voltage drop caused by additional resistance in series with the load.

— Bryan

Variable Speed Motors and Why They Matter w/ Jamie Kitchen (Podcast)

Jamie Kitchen from Danfoss talks all about variable speed motor technology. Why it exists, what it does and how to think differently about the future of HVAC/R.

If you have an iPhone subscribe to the podcast HERE and if you have an Android phone subscribe HERE.

Be Careful When Jumping Out a Blower

We’ve seen it before.

A tech diagnoses a failed blower relay or board so they leave the blower jumped out by putting a terminal multiplier on the common terminal of the relay/board and connecting the fan speed tap right to power.

There can be an issue with that.

Some electric heat fan coils have a heat/blower interlock where the heat relay/sequencer back feeds and brings on the blower across normally closed (NC) contacts. The purpose of this is to ensure the blower comes on with a heat call without the need for a G call.

In some circumstances when you put in a terminal multiplier and constant power the blower, the G call sends that constant power back to the Heat strips and brings them on.

Not good… high power bills, melted wires, fire, death and stale doughnuts.

So, if you are leaving a blower jumpered out to run constantly I advise doing it separate from the board completely.

Coincidentally the photo at the top is a setup that will not back feed because it uses two isolated circuits on the Heat sequencer for fan and heat…. so the photo I chose wasn’t the best. Cut me some slack, the blower assembly was sitting right behind my office.

— Bryan

Leak Free Systems w/ Bill Johnson (Podcast)

Bill Johnson is one of the great educators and writers of our time in HVAC/R and he shares about his career and some of his top tips on keeping systems leak free.

If you have an iPhone subscribe to the podcast HERE and if you have an Android phone subscribe HERE.

Ice Machines – Cuber, Flaker & Nugget Basics

There are several types of Ice Machines but in this article, we will focus on Cuber style and Flaker or Nugget style. Both types produce Ice but the process of freezing and harvesting is a little different. The application in which the Ice will be used will determine what style of machine is needed. I primarily work with Restaurants and Hospitals so my article will be geared in that direction.

Let’s start by simplifying the ice making process, if we take water and circulate it over an evaporator that is below freezing we will at some point start to freeze that water, once our Ice has formed we than harvest the ice and start our process again. That’s about as simple as it gets

The steps to make Ice seem simple take water and freeze it, but It’s not that simple. Making Ice cubes is actually a pretty complicated process, with several critical steps that must be met for the process to work correctly. The first step starts with properly cleaning the water that will be made into the ice to remove any impurities, water itself naturally contains minerals and those minerals are an Ice Machines worst enemy. The minerals lead to calcium buildup which causes issues with the ice machine. A quality ice machine install will have a high-quality water filter system installed that was sized properly and has the appropriate filters inside that are chosen after a water quality test has been performed. Once we have properly filtered water we bring the water into a reservoir inside the machine and the water waits until the machine is ready to make Ice.

Among all the ice machine manufacturers there are several methods that the machine will tell itself that the ice storage bin is low on Ice and to turn on, the most common methods are a thermostat and or some sort of mechanical control that is actuated by ice buildup, subsequently telling the machine that the ice is low and it’s time to turn on.

Cuber style ice machines

Assuming the machine is ready to turn on, most brands of ice machines will start in a pre-chill, which means we cool the evaporator with no water running over it, this is done to try and prevent slush from forming. Than by means of a water pump the machine will start to circulate the water over the evaporator, and that water will continually run over the evaporator and down into the sump than it will be pumped over the evaporator again, each time it passes over the evaporator the water will get colder and colder and eventually a little bit of the water will start to freeze to the evaporator plate, this process will continue over and over again until the ice is the proper thickness. The thickness can be determined by many methods including a thickness sensor, water level monitoring, and or a timer. Once it’s time to harvest the ice the most popular method is to introduce hot refrigerant from the discharge of the compressor into the evaporator and subsequently melt the ice off the evaporator from the inside out while running a little bit of water over the cubes to assist dropping the cubes off the evaporator. The harvest cycle is usually terminated by a timer that is in the circuit board. Each manufacturer has their own unique way of making and harvesting the ice. With all cuber style ice machines the harvest cycle is very dependent on maintaining an adequate high side pressure as their defrost depends entirely on it. When the machine is self contained and located indoors its not too hard to maintain the proper head pressure because the building will likely be conditioned, however on remote systems where the condenser is located outside we utilize head pressure control valves (headmasters) to back up the refrigerant in the condenser to reduce the condensing capacity of the condenser and subsequently raise the head pressure.

Flaker or Nugget style Ice machines

These machines have a unique way of making ice they utilize a round cylinder evaporator that has an auger inside of it that is turned by a high torque gear motor. The auger sits directly In the center of the evaporator with less than 1/16th of an inch clearance on either side and the auger is always spinning it has the shape of a corkscrew. The machine will have a water reservoir that supplies water to the evaporator whenever it gets low. The machine will start to freeze the water and as it becomes ice the continually turning auger will force the ice up to the top of the evaporator and out of a nozzle that will shape the ice into the desired style (Crushed, Flaked, and or Nugget). It is important to notice that with this style of ice machine the harvest cycle happens when the ice gets thick enough for the auger to scrape it off and it both freezes and harvests the ice at the same time.

— Chris Stephens

P.S. – we have a new podcast out on ice machines HERE enjoy

How to use an Adjustable (Crescent) Wrench, Pipe Wrench and Tongue & Groove (Channel Locks) Wrenches

My Grandfather is a really interesting guy. He grew up working in the Pennsylvania coal mines starting at the age of 7 or 8 and then worked as well driller, and a plumber, also went to HVAC school, and did some gas work worked a while as an electrician, welder, diver and ended up as an aircraft salvage man.

One of his favorite phrases is to call adjustable wrenches and channel locks (slip groove or tongue and groove pliers) “shoemakers tools”. I literally have no idea WHY he would call them that, or why he thought it was so funny to call them that but he certainly didn’t mean it as a compliment.

It is usually best to use a properly sized socket or wrench to do a job rather than reaching for a “multi-purpose” wrench, but every tool has a purpose and if you are going to use a tool it’s best to use it properly. I know this is basic, but we cant assume everyone has a grandpa like mine.

Pull Don’t Push (When You Can)

Whenever possible orient the wrench so that you are pulling rather than pushing (Yes, I know I’m awkwardly pushing in the GIF below) . This is a much more smooth and natural motion and you will be able to apply more force.

Pipe Wrenches are Special

A pipe wrench is only for working with pipe, NOT nuts, and bolts. I know this should be obvious but I worked with a guy once who treated a pipe wrench like a regular wrench and left a lot of damaged bolt heads in his wake.

A pipe wrench has sharp, angled teeth that will grip in one direction and release in the other direction. Open the jaw wide enough that the pipe sits in about the center of the pipe wrench unlike a typical where the object to be turned sits all the way in the back of the jaws.

Keep in mind that a pipe wrench will leave marring on the surface of the pipe, if you don’t want it to be damaged you can use a leather (or even rubber) strap around the pipe to protect it before using the wrench. A leather belt can do the trick.

Turn the Wrench Toward the Bottom Jaw

Maybe there is an exception to the rule, but not in any of my wrenches. If you turn the wrench toward the bottom jaw they will grip properly and be less likely to slip. In order to tighten vs. loosen just flip the wrench over and turn the opposite direction

Righty Tighty is Annoying

Half my childhood was HAUNTED by the phrase righty tighty, lefty loosey. IT IS ROUND! there is no right or left unless it is a reference to another direction (the top). It’s better said as clockwise tighty… and yes, I know that doesn’t sound cool.

— Bryan

Furnaces – Introduction and History w/ Jim Bergmann (Podcast)

Jim takes us all the way through the history of furnaces from the stone ages when he was a child all the way to modern modulating condensing furnaces.

If you have an iPhone subscribe to the podcast HERE and if you have an Android phone subscribe HERE

Heat Pump Defrost Boards and W2

If you are used to simple, straight cool split systems you know that the low voltage to the outdoor unit is usually VERY simple with just a Y (contactor power) and a C (common) connected to the outdoor unit in many cases. When the condensing unit controls are strictly two wire low voltage there is no continuous low voltage power so there is also no timers or other logic in the condensing unit. Usually, in these cases, the LV wires connect directly to the contactor coil.

A heat pump needs to be able to switch between heat and cool and defrost which brings in the necessity for more control conductors and complexity.

A heat pump defrost board like most modern controls contain both loads and switches to control different functions.  because it has timers and some basic “logic” the board requires a power supply and for most residential split system boards this power comes from the C (common) and R (hot) terminals from the indoor 24v transformer.

The defrost board also utilizes the constant power on the defrost board R terminal to backfeed voltage through the W2 wire back to the secondary heat inside whether it be heat strips, furnace or hydronic secondary heat.

This helps to counteract the cooling effect that occurs when the heat pump when it shifts from heat to cool mode for defrost. This function is an important thing to test on heat pumps to reduce cold draft complaints during the winter.

Simply force the board into a defrost and check for 24v between w2 and c at the outside board to confirm proper operation or check the secondary heat via ammeter or visual confirmation during the defrost cycle.

— Bryan

Electrical Circuits Class (Podcast)

This class recording discusses transformers, ground, common, and line vs. load sides of a circuit.

If you have an iPhone subscribe to the podcast HERE and if you have an Android phone subscribe HERE

3 Bad Techs That Don’t Know It

First, let’s state the obvious and clear the air a bit. The photo above is SUPER CHEESY! But this story is about three bad techs who don’t know it so three models clearly posing in clean clothes makes as good of a proxy for a bad tech as anything else.

First off, I’m not being negative about the trade or making fun of people, the point of this story is to identify some traits that many of us may exhibit or see in others techs and it can be hard to identify our own issues or issues within your organization. See if any of these techs sound a LITTLE TOO FAMILIAR and maybe we can learn something. Before you ask… No, these are not real people…. probably… maybe

Randy the Drama King

Randy, like most dramatic people who work in the trades, doesn’t see himself as being dramatic. He just thinks he is being constantly disrespected by management and co-workers and customers are crazy and the dispatcher is out to get him and it’s always about to rain and that ladder (and every ladder) looks unsafe.  These things aren’t DRAMA they are FACTS in Randy’s world and if you question this reality you get added to the long list of people who are disrespecting him.

Randy starts conversations with customers with phrases like “you aren’t going to want to hear this” or “Do you want the good news or the bad news”. He also tends to pass blame to his coworkers or his company because they are just clueless and he knows what’s REALLY going on.

Randy is actually a good tech, but he get’s in a lot of conflicts with coworkers, customers don’t always like his negativity (or as he calls it “being honest”) and he is inefficient and largely unpopular with other techs and management. Randy knows people think poorly of him because everyone is conspiring against him with that blankety-blank dispatcher Donna!

Randy always feels persecuted by the people around him and usually has something negative or conspiratorial to share about every topic. Politics, The weather, customers, co-workers, spouses… you name it.

Here is a test you can take to see if you might be a bit of a Randy

• You have more than 5 people you are ticked off with or avoiding at any given time
• You consistently see “danger” around you that nobody else sees
• During work hours you have multiple conversations over 5 minutes with others about things that are “wrong”
• You use a lot of negative and fear-inducing language with customers

If you find you are allowing negativity and drama get to you the best practice is to give yourself a break from negative speech. Like your grandma used to say, “If you don’t have anything nice to say”. Negativity is a hard habit to break but the best time to start is now and the best antidote for negativity is gratefulness.

Bob the Excuseful

Yes, excuseful is a word… I made it up and I like it.

Bob is confident that he would be able to do his job if he was just given the proper training and tools and enough time to do the job and enough sleep and wasn’t forced to work these ridiculous hours. Bob often wonders if he should go back to school and get his degree in …. something and all the courses he would take if his cheapskate boss would just invest in him.

Sure he was given a book and sent to a seminar last month but that was all THEORY, he is a hands-on learner and he CANNOT learn from books or videos or seminars or anything unless he can get his hands on it.  Once he DOES get his hands on it he can’t be held responsible for any mistakes he makes because he has to be SHOWN what to do and how to do it and if he isn’t SHOWN how can he be held responsible? Now, when he is shown, he is a hands-on learner so he can’t learn things by being shown… he needs to do it himself.

His truck may be a mess but he would clean it if he ever had time with these ridiculous hours but in the slow season that is his one time of the year to relax, you can’t expect him to take his own time during the slow season to clean his van can you?

Here are some indications you may be struggling with a bit of Bobish excusefullness

• You feel jealous when others succeed  and immediately give some reason why they have an advantage over you
• You read fewer than 5 books last year but still feel like your lack of education is someone else’s fault
• You find yourself using “hands-on learner” as a reason for failing to understand something
• When you don’t understand something you call or text someone rather than looking up an answer yourself
• You have a sense that your lack of progress is due to a lack of “opportunity”

The best way to stop making excuses is to begin living and working with what old-timers called “grit” or “gumption”. This means doing whatever it takes to solve problems, making excellence a goal and going after it no matter the barriers. Start by reading and learning on your own, don’t wait for someone to show you or tell you, go get it yourself.

Todd the Careless

Todd knows he is just forgetful, he TRIES to remember to tie down his ladder and put the caps back on and close his back doors on his van but he just forgets sometimes OK!

Sometimes Todd get’s defensive when other techs call him out for leaving the panel off or “forgetting” to clean the drain, but usually Todd just apologizes and says he will do better next time, but he knows he won’t because he didn’t do it on purpose, it just …… happened.

Some of the “Grouchy” old techs have told him that doesn’t seem to care about his job, but they are WRONG! (in Todd’s mind) he does care, he just has other things going on in his life and in his mind and sometimes accidents happen… like the time he stepped through the attic ceiling, or the time he slipped on the ladder, and that one time he rear-ended that car in the parking lot… oops

You may be a Todd if ….

• You regularly make mistakes where you “just forgot”
• You find yourself looking at your phone, texting and using social media during the workday
• Your mind is preoccupied with personal matters during work and while driving

We have entered a new era of carelessness due to the advent of smartphones, social media, and texting. Many of us find our minds constantly distracted by things other than work during the work day and it leads to poor outcomes, mistakes and safety hazards. everything from climbing a ladder, to driving, to filling out a service call requires ATTENTION and distraction can lead to costly and dangerous mistakes. The best advice is to put the distractions way during the work day… unless it is reading this article. Just remember to put the panels back on and run test the equipment when you are done.

— Bryan

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