Month: September 2018

I need to warn you…

This is the actual process we use at the company I own for our typical “standard” residential maintenance. I’m sure you will find some things you do differently. Take it for what it is and I’m happy to get any feedback you may have.

  • Read the call notes, property notes and customer notes. Check the last service call and last notes and readings so you are aware of the service history.
  • Check the filter size and ensure you have the PROPER filter if possible
  • Wear shoe covers in the home, ask the customer if they have noticed anything unusual with the system.
  • Inspect and set the set the thermostat to run, shine a light in the return to check for filters, blockages, debris or damage.
  • Visually inspect the system operation to make sure all of the components appear operational before beginning the maintenance. Note anything out of ordinary you observe to the owner and address / diagnose before proceeding.
  • Remove disconnects / shut off breakers. Check for proper breaker sizes and inspect disconnect wires, lugs and pulls.  
  • Remove the condenser top and panels and place them carefully in the grass away from damage.
  • Remove any debris from the bottom of the unit. Inspect wires and compressor terminals while doing this. Use a vacuum to remove dirt and leaves as required. If grading is poor, use a shovel to scrape dirt/leaves away from the base of the unit.
  • Wash the coil well, starting from inside out and from top to bottom. Only use coil cleaner according to the labeled dilution and only use it when the coil requires it.
  • Check the inside of the condenser one final time for any potential wiring or copper rubouts and repair / isolate as required. Note any rust on the compressor, roto locks or accumulator.
  • Inspect the crankcase heater if the system has one. Confirm operation by amperage or ohming out.
  • Look for any signs of refrigerant oil (potential leak points)  
  • Replace the top carefully, ensuring that you don’t pinch any wires. Rewire the fan.
  • Inspect all wiring connection in the condenser control box for tightness and damage. Check contactor points and note condition.
  • Move inside, if the air handler has a finished floor around it, lay down a drop cloth. Always keep the work area inside clean during and after work.
  • Check the evaporator coil condition and cleanliness top and bottom. If the coil is a slant coil orientation and has any dirt on it clean the surface with evaporator coil cleaner, pump sprayer, rag and a soft brush.  If the coil is dirty and an A or another coil type that cannot be easily cleaned in place you may quote a removal and clean if the coil has no known leaks and is less than 7 years old.
  • Connect a wet vac to the drain outside
  • Remove the panels from the air handler and begin pouring water into the drain pan all the while helping any sludge in the pan get removed by moving it toward the pan outlet. Use duct tension straps or zip tie ends / small bottle brushes to help pull sludge out from the sides of the pan under the coil and clean all channels.
  • Run a minimum of 2 gallons of water through the pan and then empty the vacuum. Run another gallon through and repeat the process until the pan is visibly clean and the water in the vacuum is clean.
  • Run 1 more gallon through the drain one done and ensure it runs out.
  • Spray and wipe down the inside and outside of the air handler, including wires with a safe anti-microbial solution.
  • Remove any dust from the blower motor body and end bell with a vacuum, rag or soft brush, being careful not to force dust further into the motor. When the dust buildup is severe, use compressed air or nitrogen and a vacuum to remove it.  
  • Test the blower capacitor by removing the leads, testing with a capacitor tester and reconnecting the leads.
  • Inspect the blower wheel for cleanliness. If it is dirty check the particular maintenance type to see if removing and cleaning the blower is extra or included.
  • Check the blower motor bearings for play.
  • Inspect all wires for rub out inside and outside the air handler. Inspect and disconnects and check any lugs for tightness.
  • Check low voltage wiring and dip switch/pin settings. If the system has an advanced interface you will need to check for proper settings at the controller.
  • Check coil feeder tube location and condition. If tubes begin to rub out, isolate them and strap them together using foam tape and zip ties.
  • Inspect the float switch for proper installation and wiring. Test the float switch to ensure it breaks the circuit when the float rises. If there is no float switch, quote to install one at the end of service. 
  • Check air handler panel insulation, glue or retape as required.
  • Spray down the coil surface lightly with antimicrobial and add 3 pan tabs to the front of the drain pan away from the outlet.
  • Install a new air filter with date and your name.
  • Replace the bottom air handler panels and turn the air handler breaker on.
  • Run the heat and test the heat strips on and off using an amp meter. Note heater and blower amps.
  • Shut off the air handler, replace all panels and double check the drain cleanout cap is in place and the float switch is in the correct position.    
  • Put the system into cool mode and turn the air handler back on (condenser disconnect still off / out)
  • If the system has been checked during previous calls and has no history of leaks then use the historic data to perform a Non-invasive refrigerant test. If this is the first maintenance or if the system has a history of issues then connect gauges.
  • Connect an amp clamp to compressor common and observe as you turn on the condenser breaker/disconnect.
  • Test the L1 & L2 voltage and ensure it is in the acceptable range
  • Allow the system to run for at least 10 minutes. During this time you can Begin Cleaning up
    1. Start filling out the service call/collecting model and serial numbers if required
    1. Inspect suction insulation and thermostat wire outside for damage or poor splices
    1. Perform the “under load” capacitor test
    1. Read across the contactor points to see if there is any voltage drop in the contact points
  • Once the system has run for 10 – 15 minutes perform either the non-invasive test protocol or check and note suction, head, superheat, subcool and delta T according to the “5 pillars” tests and any manufacturer guidelines.
  • If the system is a heat pump, test the opposite mode (usually heat) to ensure the reversing valve shifts properly and the system runs.
  • Note and suggested repairs or improvements to the customer and get their response.
  • Clean up fully and double check drains refrigerant caps and disconnects. Call in standby.
  • Wrap up paperwork with the customer.
  • Ask the customer if there is anything else you can do to make their experience better and if they can think of any way you or the company could improve.
  • Complete all call notes, finish timesheet entry, neaten van in preparation for the next call.

   — Bryan

P.S. -Since publishing this article the first time I’m always asked how long we “give” to do it. With a maintenance this complete the time it takes will vary a lot and can be done in 45 mins on a new clean unit all the way up to 2 hrs.

  

Testo 760 Category IV Multimeter

I was standing at a 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

We all have some weird tools we keep in our Tool bags, a Baster may look suspicious but it comes in really handy for removing water from a float switch.

This one is extra handy because it comes with a nice tapered bottle brush inside it that works great to clean out the outlet port from the pan and the pan segments on the sides of the coil.

I got this one for $1.98 from Walmart, you can’t beat that!

What’s a weird tool that you keep in your bag?

— 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 the 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 set up 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 the 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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