Wheeler on HVACR: My greatest HVACR servicing fear
Since I moved to Florida, I've lost my life-long access to purchasing HVACR parts and equipment, because I don't have a contractor's license.
It's a strange situation for a former HVACR contractor, instructor, service technician, national service manager and industry writer to find himself in. Yes, the day is coming - perhaps this summer - when I may have to call a local contractor to service and add refrigerant to my home heat pump. Oh, no!
What am I afraid of? Having someone else doing the work and having to pay for the service doesn't bother me at all. It's just that I know all the contractors around here, and frankly I don't trust any of them to do the job properly.
In fact, I know few companies on this continent that I'd trust the life of my heat pump to. Am I just a little paranoid, or do I have valid reasons for my concerns?
Enough knowledge to be dangerousOther than hooking your HVACR system up to the wrong voltage, having trash in the refrigerant lines, or having a condenser or evaporator fan quit for a long period of time, the worst thing that can happen to a system is to let air get into it during installation or service and not to pull a proper vacuum. Yet that's what really happens most of the time with most contracting companies. Oh, don't get me wrong: Almost every company has at least one technician who does the job properly.
Unfortunately, the rest of the technicians and installers don't, and customers pay the same hourly rate no matter who shows up.
Now, perhaps you feel that I'm making too sweeping an accusation of our entire industry. I'm not. I have traveled all over this country and watched technicians and installers do their work. I've gone out on jobs hundreds of times and tested for air in failed systems. The fact is that 10 years ago, few installers gave system evacuation much more than a lick and a promise, if anything at all. And today, with the need to carry refrigerant recovery machines, even fewer want to bother with carrying a heavy vacuum pump to the site. And forget about changing the pump oil regularly so they can pull deep vacuums.
So what's all the hullabaloo about pulling a proper vacuum? You need to understand these points:
- Air in the system drastically reduces operating efficiency. It fills up heat transfer surfaces inside condenser coils, which raises pressure differences (making the compressor draw more energy) and provides less cooling. Connecting refrigerant lines to a condenser or evaporator without pulling a deep vacuum can introduce several quarts of air into a system that doesn't use all that much refrigerant to begin with.
- All ambient air contains moisture (humidity), which will precipitate out at least a few drops of water into the system, even on days when it isn't raining. Guess what happens to the lubricating oil when a couple of drops of water enter a closed, hot, churning compressor or the inside the motor winding of a hermetically sealed compressor. Yes, locked and shorted compressors.
Pin holes and hairline cracksIf you're in the refrigeration-parts business, air and moisture create an additional problem. Cracks and crevices in the system - especially at the weld joints in evaporator coils - collect water. With a low- or medium-temperature system, the water micro-droplets freeze over and over again as the system cycles on and off. This in turn creates pin-hole leaks in the evaporator. Do you get a lot of evaporator warranty claims due to leaks? Could it be that the problem isn't with the manufacturer?
Most HVACR compressors don't fail due to old age or manufacturer defects. They fail because of improper installation and servicing. Think about it. Do you get a lot of warranty compressor returns? Don't get me wrong. Manufacturers mess up too, but the vast majority of early compressor failures are created in the field.
Now do you understand why I don't want someone else servicing my home system? And can you understand why you should be just as concerned?
Close only counts in horseshoesThere is only one way to remove efficiency-robbing air from a her- metically sealed HVACR system, and that is to pull a vacuum in the area where the air is located. The good news here is that even a hit-or-miss vacuum will usually get rid of most of the air in a system.
The bad news is that the same is not true of moisture in the system! When a condensing unit is first installed, air and moisture are usually just found in the connecting lines, and either a deep vacuum (30 minutes or more), or a triple-dilution vacuum, where shorter vacuums are broken with pure refrigerant, does a great job.
This also works when a technician has to remove air he introduced by opening a clean system for service reasons. Once water gets in the oil, however, only a long, deep vacuum (12 hours or more); installing an oversized filter/dryer; or doing both procedures will clean the sludge from the oil.
So what's the point? First of all, you'd better keep a close eye on the techniques of anyone servicing your own HVACR equipment. But more importantly, I believe it's time to get the word out to all your dealers regarding the dangers of not dehydrating HVACR systems. Then conduct service-training classes to show more of them how to do the job right.