Month: March 2017

 

I was sitting in a session at the HVAC Excellence educators conference (which was excellent by the way) and my phone buzzed. So like a typical punk kid I looked down at it to see that my friend Josh had sent me a Facebook message asking if we served the East side of Orlando because he wanted an A/C maintenance on his home. I told him that we did not serve that part of town and I didn’t think anything else about it.

Then yesterday I see this post

So we go out to look at it, and sure enough. The system is BARELY low, like 3 degrees of subcool low and we added 1/2 of a lb of R22 (weighed in) and did a leak detection. Yes, there was a TINY leak in the evaporator coil so Josh will probably end up getting a system at some point… However, the other tech did not do a maintenance at all, he did not quote a coil or anything other than a system. He literally showed up, saw the unit was 14 years old, pulled out his leak detector, found a hit and wrote up a proposal for $5400.00. He tried to close the “deal” right on site. No load calculations, no looking at the ducts, just a leak detection, a proposal and run.

How many 14 year old units have zero leaks?

He didn’t clean the drain or the condenser coil, he hardly even checked the charge. Heck, Josh has a UV light that wasn’t even working due to a simple loose connection, he didn’t even look at that.

Unfortunately for this company, my friend Josh is a local consumer advocate who goes on local TV news REGULARLY to talk about ways to save money and EXPOSE SCAMS. I bet you can see where this is headed.

HOW DOES THIS HAPPEN?

The standard narrative is that there are just a bunch of greedy scammers out there trying to take advantage of people. Clearly this is true sometimes, but many times the story is longer and sadder than that, often this type of thing happens when well meaning people get worn down.

Tell me if this sounds about right.

A new tech get’s hired into the trade, maybe he has some schooling maybe he doesn’t, either way he get’s his EPA license and starts riding around with another tech. The tech he rides with spends most of the day complaining about his boss, dispatch, other techs, customers and politics but almost no ACTUAL training. When they arrive at the job there are two main objectives

#1 – Get in and out as quickly as possible with as little work as possible.

#2 – Sell as much as possible during that short time. This can be hard start kits, capacitors and surge protectors some places, IAQ products others and some it’s always finding a way to push a new system. For many, it’s all three.

Usually this makes the new tech feel at least a little uncomfortable but this starts to fade as the days of riding around whining broken by short stints of selling continue.

After a few months the new tech is put into a van with some parts, pamphlets, invoices and proposal forms and set loose on the world. If he is smart, he realizes pretty quick that when his bosses talk about customer service what they really mean is making as much money as possible in a day with as few customer complaints and call backs. Usually, the easiest way to do that is to condemn everything , when a system is replaced nobody ever knows if your diagnosis was correct or not. When you do a PM there is always something you can point to as a major issue that gives you an easy out, cleaning after all does not ring the register.

Techs justify their behavior

When I was still in trade school back in 1999 I participated in a skills challenge against other students from schools across Florida. There was another guy who was already working in the field and I remember him saying “I never just change one part, I change as many as I can and the customers never know the difference and their unit will last longer”. I was appalled then as I am now by this type of thinking but I’m pretty sure he honestly believed he was doing the right thing. He had been brainwashed into thinking that this was what being a technician meant.

So this all begs a question, who is to blame and what can be done about it?

The Root Cause

 It is just easier to make money when you focus on selling instead of technical excellence. You can be great at what you do and still not make a profit but when you FOCUS on profit at every level you will usually make more of it…. for a while.

I actually blame the quality techs and companies who don’t charge enough for what they do as one reason this happens.

I have been one of these contractors for years. We squeaked out a meager profit every year driving used vans, using cheap tools, trying to make ends meet and praying the vans don’t break down. All the while, the sales focused businesses have new trucks and spiffy, clean uniforms.

The good guys need to stand up and stop apologizing for what we charge and what we do. we need to CHARGE for the high quality maintenance we do so that we actually make a profit on it. We need to diagnose the whole system and make quality recommendations to our customers based on the solid and complete diagnosis we perform. There is no reason we shouldn’t be able to afford quality tools and a well stocked van if we are the ones WHO ACTUALLY KNOW HOW TO USE THEM.

Instead we beat one another up on price and undercut one another, calling another good, quality company who charges more a “rip off” or a “scam” just because they have their pricing figured out to where they can actually make a profit.

This company who went out my friend Josh’s  house was going to charge $5,400.00 for a Lennox 3.5 ton 14 SEER Heat Pump system, that isn’t a crazy price but to some it may be seen as a “ripoff” because they would charge $4,500.00. We might charge $6,000.00 for the same system… with a new return liner, and line set, installed with nitrogen flowing, evacuated to 300 microns, with a proper load calculation, permits and a perfectly weighed in charge confirmed by manufacturers specs to a proper subcool.

The “Ripoff” is the one who doesn’t deliver on their promise, not the one who charges more.

What to do About it 

If you are a manager or owner of a company make sure you are supporting your techs to get more TECHNICALLY sound and support them to use those legitimate technical skills to translate into profitable repairs and quality workmanship. Communication skills are key in a residential tech, a tech who understands IAQ like the back of his hand will naturally sell more IAQ products, a tech who understands air flow and duct design will sell more duct upgrades and the tech who understands complete system performance will make more needed repairs. This is long road and there are no shortcuts.

If you are one of the good guys let’s band together, keep our heads up and charge enough to have a good life.

— Bryan

Testo 760 Category IV Multimeter

I was standing at booth at the HVAC Excellence Educators conference and an instructor walks up, grabs a meter and asks me “what’s the difference between a category 3 and a category 4 meter”?

Well, I really wasn’t sure other than that the category 4 is rated for more demanding conditions. So I did some research and dug into IEC 61010-1 and found that category 3 is rated for most uses OTHER than outdoor utility connections and category 4 meters are rated for all uses.

Courtesy of Fluke

There are also some voltage considerations and limitations to the different categories but the primary difference is not the regular duty but the high voltage transients. High voltage transients are often called “surges” or spikes and are most likely when working on outdoor transformers and distribution panels.

Rubber meets the road is that for HVAC use a category 3 meter is likely going to do the job but if you ever work in main panels, or outdoor transformers go for a cat 4 meter.

— Bryan

PS – Fluke has a great info sheet on this HERE

You can see more about the Testo 760 shown HERE

I heard a great presentation by Ron Auvil on VAV systems and it got me thinking…

Can you size a commercial system / perform a block load by the number of occupants?

Yes! 

No, just kidding that’s crazy talk. There is way more too it than that.

However, in a commercial environment, while the perimeter of the building is affected by heat loss/heat gain to the outdoors, the internal zones are “cooling only” zones with the primary load usually being PEOPLE.

This is where the 500 btus per hour comes in. On average a sedentary worker in a building will add 500 btus per hour to ALL areas of the building whether it is hot or cold outside. This creates an issue in the winter when the perimeter of a building requires heating and the center of the building requires cooling.

Now, keep in mind, a sleeping person generates heat more in the neighborhood of 260 btu/ hr so if it’s a REALLY boring job where workers dose off at their computers it may be less.

Add in the internal electrical loads from lights, computers and other equipment and you start to realize that EXTERNAL loads are only part of the equation, especially in large commercial buildings with many occupants. In fact, in a busy commercial space the internal loads generally far outweigh the heat entering from the outside (external load).

This is where the concept of thermal diversity comes in. On a cold day there may be a need for heat at the perimeter of the building to offset heat losses to the outside while still requiring cooling in the center of the building to offset the internal loads.

In a good commercial design you must have some method of dealing with the thermal diversity between internal and perimeter zones along with maintaining appropriate ventilation / outdoor air.

Food for thought.

— Bryan

 

Photo Courtesy of Emerson

CO2 (R744) is naturally better suited for lower temperature refrigeration applications because of its low temperature saturated state at atmospheric pressure (-109.3F). You will notice I said “saturated state” because CO2 does not “boil” at atmospheric pressure. At any pressure below 60 psig CO2 goes straight from solid (dry ice) right to a vapor, This is why 60 psig is known as the “triple point” or the point that could be either solid, liquid or vapor.

Now go to the top of the range with CO2, when you apply 1055 psig the saturation temperature is 87.8F but go up even 1 more degree and CO2 CANNOT be liquified, this is known as the critical point of the substance. Whenever a substance is forced beyond it’s critical point it becomes what is known as a supercritical fluid and has properties that are unique to this state but it is certainly not a liquid. You can see more in this natural refrigerants PT chart.

In a transcritical (trans means beyond or through so transcritical means “beyond critical”) booster refrigeration system the low temp portion of the system operates using it’s own compressors that “boost” the refrigerant from the low temp side and discharge into the suction of the medium temp side. The high stage compressors then pressurize the CO2 (R744) above its critical pressure / temperature.

What is traditionally called a condenser becomes a gas cooler and decreases the temperature (rejects heat from) of the discharge without actually condensing it into liquid. The cooled supercritical fluid goes through a pressure reducing valve, where some of it condenses into liquid and the rest remains as gas. Liquid and gas are separated in a flash tank (receiver). Pressure in this tank are usually controlled to around 450 to 500psig.

It’s super critical that you understand all of this…

See what I did there.

— Bryan

 

 

The definition of a transformer is a device that changes the voltages in an alternating current circuit.

You may have heard of an autotransformer or a buck and boost transformer and these terms are usually being used for the same type of device just highlighting different aspects. A transformer does not need to be a buck and boost to be autotransformer and it does not need to be an autotransformer to be buck and boost but often the two elements go together.

Autotransformer

The word auto in auto transformer really just means one or single not really automatic or automated in the way we usually think of it. It is an autotransformer because it only has one inductive (magnetic) winding shared by both the primary and secondary.

Buck and Boost

Buck just means that it decreases the voltage and boost means it increases it. A buck and boost transformer means that it can both increase or decrease the voltage.

What is their application? 

Buck and Boost autotransformers are often used to make small changes in voltage, say from 208v to 240v (boost) or from 240v to 208 (buck). They are usually efficient and inexpensive when only small changes are needed, whereas a traditional two coil transformer is more practical for larger changes.

Most of these transformers will have multiple tap points for different output and input voltages and can often be connected in different configurations to perform a wide range of functions like in the case of the Emerson Sola HD.

One major consideration with an autotransformer is that there is no isolation between the primary and secondary so a failure of the isolation of the windings of an autotransformer can result in the input voltage being applied to the output and component damage. There is also greater likelihood of harmonic and ground fault issues because of this “mixing” of primary and secondary.

— Bryan

Photo Courtesy of Emerson

What is Cascade refrigeration?

Cascade refrigeration is a term you will hear more and more over the coming years, and while some of the systems may be very complex, the concept is actually pretty simple.

Some refrigerants are well suited for high and medium temperature applications, and some are better suited and for a lower temp applications. In a cascade system the high/medium temp refrigerant circuit is used to cool the condenser of the low temp circuit by way of heat exchanger. In essence, the condenser for the low temp system is also the evaporator or part of the evaporator of the high/medium temp system.

In the diagram above the medium temp circuit is used in the medium temp cases and is ALSO used in the heat exchanger to condense the refrigerant in the low temp circuit.

There are many reasons for this type of system but one of the big reasons is it is a practical solution for using CO2 (R744) as a low temp refrigerant.

— Bryan

 

Have you ever noticed a blower motor rated for 120V draws about twice the amperage of a motor rated at 240V?

This is because motors are rated in Watts or Horsepower and according to Watts law Watts = Volts x amps.

In order to keep the Wattage output the same at 120V it draws twice as much current.

This is different than what happens when you drop the voltage of a motor below its rating.

Here is an experiment I did.

I took a regular 1/6 HP 208 – 230v condenser fan motor and tested it under normal conditions at my office and here is what I got


I then connected the common wire to neutral instead of L1 power which leads to approximately 120v applied and here is what I got.


By dropping the voltage by around 50% the amperage dropped slightly, the wattage went to less than half and the power factor also went in half and the motor slowed way down.

The motor slowing down is due to slip in the motor, meaning that the motor is running significantly slower than the speed it is designed for.

This means that not only is the motor running inefficiently, but it is also going to get hot because as the motor runs slower it has lower inductive reactance (the magnetic resistance in the windings). As the inductive reactance drops the windings have lower resistance and thus get hotter.

Even after all of this, the motor still consumes less than half the watts.

Rubber meets the road is that when a motor is designed for lower voltage it will draw more amperage to do the same work.

When you apply lower voltage you both decrease the work done as well as the efficiency and life of the motor because more of the energy goes to heat instead of mechanical work as the motor slips more and more. You also see higher power factor as the motor begins to slip resulting in even worse power efficiency.

This is one reason why voltage drop is a such an important thing to consider when sizing conductors and why 208-230V units are slightly derated or n both capacity and efficiency when installed on 208v.

Pay attention to Voltage, it can save a lot of money over time in both power efficiency and motor longevity.

— Bryan

We work on a lot of Carrier split heat pumps and I have heard the common pressure switch inside called a low pressure switch (because it opens on fall in pressure ) and a high pressure switch (because it’s in the liquid line) but RARELY do I hear it called it’s true name.

Loss of charge switch

In a heat pump system the operational suction pressure can vary greatly from the suction you will run on a hot day in cool mode to the suction you will run on a cold winter day in heat mode. This makes a traditional low pressure switch ineffective.

The loss of charge switch performs much the same role as the low pressure switch but since it is in the liquid line in cool mode (before the metering device and after the condenser) and in the expansion line in heat mode (after the metering device and before the outdoor coil) it will not be as prone to fluctuations and will only keep the system off in cases of very low charge or “loss of charge”in cool mode. 

In heat mode it will also open during loss of charge but also if there is a line drier or heat mode metering device restriction.

All in all it’s pretty easy to understand, so long as you know it’s true identity and purpose.

— Bryan

Let’s take a walk through the startup and commissioning procedure of a conventional or “single” refrigeration condensing unit.  We’re going to start with a unit that is fully piped in and has been pressurized for leak and strength testing. For brevity, we are going to assume a basic familiarity with industry standards, company and customer policies and requirements and the job site and any policies in place there.
Before we even swing a wrench at the machine, let’s familiarize ourselves with the job site and equipment.   Take a walk around, check with the job supervisors, check in with other trades, etc. Find all the equipment you’re to be starting and make notes.
Step one is to make final leak tests.   Typically, the installer records time, date and pressure data.  If you put the pressure charge on the equipment, you should have done so.  If you have had any temperature change, you MUST account for that.   While nitrogen is chemically inert, all gasses respond to changes in temperature by changing pressure.   The math is simple and I’ve addressed it in another article.

 

We’ll assume here the installers did their job properly and that there are no leaks to track down and fix.  Blow that charge off and break out a nitrogen cylinder.  Yeah, I know, you just blew off the nitrogen… That’s OK  – you aren’t leak checking anymore.

Disconnect the pressure controls; you’re going to SET them.   If they’re the little-encapsulated type, we’re at least going to check and record the operating pressures.  If they’re of the brazed in variety, you’ll need to try to isolate parts of the system to pressurize them to test.   I recommend referring to the manufacturer’s literature for proper control settings and, if they don’t offer a guideline, referring to the Heatcraft installation manual for guidance.   Use your nitrogen regulator and manifold gauges to adjust each control to precisely the setting desired.  The procedure that I typically use is to adjust the control to a setting that is near the top of the scale, set the applied pressure with the nitrogen to the desired pressure then adjust the control down until it closes.   Some controls have a very audible ‘click’ when they open and close, others will require you to use an ohmmeter to determine when the contacts open or close.

Use a sharpie to record that setting right on the cover of the control or, if you prefer, inside the electrical control panel.  Since many larger customers have specific commissioning paperwork they require, you might as well get your notebook out and record it there, too.

 

Once you’re done setting the controls, it’s time to evacuate the equipment.   Make sure you’ve opened any and all service valves in the system and that any control valves are open or that you’re connected on both sides of the valve.

 

Even though you’ve got a lot of work to do while the pump is running, I still prefer to use the faster no manifold, large hoses, core pulling method.   That way, I’m spending more time in a deep vacuum and, if something goes wrong and I have to make a repair and evacuate the system a second time, I’m not spending a lot of time watching a vacuum pump run.  I’m not even digging my micron gauge out just yet, just hook up the pump and let it run.

 

While the pump is running, you’ve got some details to attend to.

 

  1. Record model and serial of the condensing unit and the indoor equipment.
  2. Check phase rotation if possible. If not, you will check this during the initial startup. Remember not to energize equipment while under a deep vacuum.
  3. Check and tighten all electrical connections. I prefer to use a torque indicating device for this just to eliminate any chances I can for a problem down the road.
  4. If there are flanged or threaded connections on the refrigeration system, I’ll check and torque or tighten them at this time as well. Again, I prefer to use a torque indicating device when and where possible.
  5. Check that the metering device, condensing unit and oil type match the refrigerant being used. Make sure TEV bulbs are installed properly.
  6. If the unit has a headmaster and a fin/tube condenser, strip the panels off of the unit and measure the condenser for calculating a flooding charge. Go ahead and figure it and write that down, too.  Microchannel coils just have a lookup chart.
  7. Verify that any other trades involved have completed their work. It’s no fun to have a piece of equipment ready to run and not have power to it or to find out a day later that a condensate drain wasn’t  properly installed or heated if necessary.
  8. Check any doors on fixtures to make sure they close and seal properly. Make any adjustments needed.

Get that micron gauge out now and let’s check the progress of our evacuation.   Again, much has been written on this subject, so I don’t want to belabor the point of the how and the why here.  Pull a proper deep vacuum on the equipment according to the customer’s standards, the manufacturer’s standards or industry standards and record times and evacuation levels here if the commissioning paperwork requires it.

Evacuation complete, here is where starting a refrigeration unit diverges from starting up a residential one.   Residential equipment typically comes precharged for a specific amount of line set length.  All you have to do is open the lines, start the equipment and check charge.   Split refrigeration equipment doesn’t come precharged because the manufacturer can’t know how their machine is going to be installed.  We will have to field charge it.
Final checks before charging:

  1. Power to the unit on? Leave disconnect open for now.
  2. Power to the evaporator unit? Go ahead and turn that on.
  3. Power to any control valves like a liquid line solenoid?

Put the cylinder on a scale and start adding refrigerant to the equipment.  Techniques vary somewhat here, but I start by adding liquid refrigerant straight into the receiver valve and liquid line while monitoring suction pressure.  Suction pressure is rising, so we’ve got flow through the system.  If we don’t see a suction rise, we need to stop and investigate.    Maybe a valve is closed or not energized properly. For us, everything is going nicely, go ahead and close that disconnect to the condensing unit to energize the equipment.  If you weren’t able to test phase rotation earlier, now is the time.  Verify that the compressor and fan motors are rotating in the correct direction and make any corrections necessary before proceeding any further.
While adding gas, the compressor is going to short cycle a fair bit while you’re getting enough refrigerant into the system to keep it running. Some guys like to bypass the low-pressure safety and I’ve done that.  I’m also not opposed to opening up some liquid to the suction line.   Not full flow, but get some in there.

 

For right now, we’re  going to charge this unit to a moderately cloudy/bubbly sight glass.   We’ll come back and finalize the charge later and I’ve always found it easier to start low and add up to final charge than to add too much and have to remove some or be uncertain of our charge.  It’ll work, sorta, even low on charge.  Once the machine is running on its own, add just enough to get that sight glass in that cloudy state and stop.  Record the amount of refrigerant added in your notebook.  Monitor pressures and suction temperature for right now.  If your superheat really starts to drop into the flooding range, it’s time to go check the evaporator to see why, but that’s pretty rare.

Continually monitor temperature in the box while monitoring the unit operation until box temp gets to within 5° or so of the desired temperature.
Now, we get to do some wrench twisting.
First things first, you MUST HAVE a solid column of liquid to continue, so add the rest of the charge.   Clear the glass and add your flooding charge. Record that total amount of refrigerant added both on the unit and in our notebook
Now, let’s go check and set the superheat.   Having a box that is close to temp and a solid column of liquid is important because without both conditions being present, a TEV cannot properly regulate superheat at the coil.   Connect your gauges and temperature probes and monitor for a couple minutes.    Again, record the information.   Pressures, temperatures, superheat….    Write it down.    Adjust the superheat to the manufacturer’s or customer’s specifications.   Be aware as you’re doing this that the unit may cycle off and throw your readings off.    You can adjust thermostats or bypass controllers to keep the unit running while doing this but be careful to not allow the unit to get too cold as this will affect the operation of the valve at normal conditions.
Final details and checkout.
Now our unit is running and we’ve got everything setup right where we need it, we need to turn our attention to details.

  1. Set the thermostat or temperature control and verify the setting with an accurate thermometer.
  2. Set the defrost timer to manufacturer’s specifications or customer’s specifications. Test operation of the timer as well and ensure that it not only keeps time but switches properly. Then set the timer to correct time of day.  If requested, provide customer with the defrost schedule.   Verify that any defrost heaters draw proper amperage and record.
  3. Many cases and freezers have mullion heaters to prevent frost and condensation on doors and frames. Check these for proper amperage and record.

Now we can sit down, fill out the customer’s paperwork and submit that to them.

 

Before leaving the job site, it should go without saying that we need to clean up any debris left behind.  I also like to present the customer with their case manuals, give them a quick run through of the equipment and answer any questions they have.   Be sure to leave a business card because even though we’ve been diligent in starting and commissioning this equipment, they may have problems or just questions down the road.

— Jeremy Smith CM

 

 

 

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