Replacing Wires Inside a Unit

Occasionally it is necessary to replace original factory wiring inside a unit. Sometimes critters have nibbled on them, sometimes the weather has degraded them, and sometimes the overheating or failure of a connected component has made the wire stiff and brittle. Whatever the reason, it is important to note that all wiring must meet the original manufacturer factory specification. Of course you should replace the original wire with the same material and gauge, but there is more to the specification than just the actual wire.

The wire insulation rating is just as important. For example, a wire from an NM-B cable should never be used to replace power wring inside a unit even though it might be the same material (copper) and gauge. The wiring inside most equipment is rated as machine tool wiring (MTW).  MTW insulation is a thermoplastic that is rated for up to 600 volts and is moisture, heat, and oil resistant. The insulation on NM-B cable is not moisture, heat, or oil resistant.

The wire insulation rating can be found printed or embossed on the wire. The figure below shows the marking.

Note that the wire gauge can be seen in the yellow circle and the insulation type, MTW or THHN, can be seen in the green circles. You should check to make sure any wiring you plan to use inside a unit meets the manufacturer’s original specification. This specification can often be found in the wiring diagram notes. A common note is that any replacement wiring must be rated for a temperature of 105°C. The insulation of NM-B cable is only rated for temperatures up to 60°C, and so should not be used inside the equipment cabinet.

Condensate Drain Cleaning

It is time for annual spring AC maintenance calls. One thing you should be doing is cleaning out the condensate line and checking to see that the condensate drain is working properly. The customer is paying you for a seasonal maintenance to avoid having problems – such as a mess caused by something as simple as a clogged drain line. If you can get to the condensate drain easily, you can blow it out with nitrogen using a rubber stopper with a 1/4” copper pipe and flare connection.

Gallo Gun

Another option is the Gallo Gun that uses CO2 charges. Both of these options require access to the drain opening inside the evaporator drain pan. The drain opening is usually accessible on cased coils by removing a panel on the front of the coil casing. Likewise, the drain opening for the coil in most heat pump air handlers can be accessed by removing the front panels.


However, for coils in hard to reach places, or coils installed inside a plenum with no access panel, it may be easier to suck out the muck using a Sludge Sucker. The Sludge Sucker is installed on the drain outlet. Nitrogen pressure creates a vortex which makes a strong suction on the drain line, sucking out the water and muck in the entire drain system.

Uniweld Sludge Sucker

Foe some systems you may need to clean out the condensate line trap. If  the drain is already plugged, then chances are the trap is plugged. Most manufacturers require condensate line traps. The trap is designed to stop air from sucking in through the condensate line during operation. Unfortunately, because traps tend to trap stuff, they get blocked with crud. Most codes now require that condensate lines have clean-outs which allow the trap to be cleaned without cutting out the existing trap and replacing it. For many site built traps, this has been common for many years. The only practical way to clean them was actually to just replace them.

If you do have to cut out and replace a condensate trap, make sure that what you replace it with can be opened and cleaned. This can be done by installing tees in a couple of places where you would normally use ells and plugging or capping the unused branch. Alternatively, you can use a manufactured product such as the Rectorseal EZ Trap of the All-Access AA1 cleanout.

Rectorseal EZ Trap

All Access AA1

Another solution would be to remove the traditional trap and replace it with a product designed to provide a drain seal without trapping water. Three types are available – the Cost Guard condensate drain seal by Trent Technologies, the Air Trap by Des Champs Technologies, and the Rectorseal Waterless Kit for their EZ Trap. I will talk more about how these work in a future post.

Trent Technologies Cost Guard

Des Champs Air Traps

Rectorseal Waterless Kit

If the system you are working on does not have a safety overflow switch installed, consider adding one. The safety switch is typically wired in series with “Y” to prevent the outdoor unit from operating and creating more water.  Some are installed in the primary drain clean-out, and some are installed in the secondary drain port. They are inexpensive, easy to add, and help prevent property damage. In the case of coils installed on top of furnaces, they can prevent the destruction of expensive electronic components inside the furnace from an overflowing condensate drain.

Rectorseal Safety Switch in primary drain

Diversitech safety switch in secondary drain

Service IS What We Sell

HVAC/R service technicians must master many different skills to be successful. There are the hard skills that involve manipulation and mechanical ability like electrical wiring, brazing, and refrigerant handling; there are the problem solving skills like refrigeration and electrical troubleshooting; and there are soft skills such as customer service. Service technicians must be competent in every one of these skillsets. Note that these skillsets are quite different from each other. The hard skills require mechanical ability and a good kinesthetic sense. Problem solving requires abstract thinking and the ability to take several pieces of information and form a reasonable judgment. Even if a service technician has great mechanical ability and is an accomplished problem solver, they must be able to deal with customers. Service work is primarily about customer service. Often, individuals who are mechanically gifted are not “people persons.” They would much rather rebuild a compressor than talk to the compressor’s owner. The problem is that the compressor is not who writes the checks, the owner is. So if you want to be paid, you need to learn to talk to the customers.

Increasingly, service technicians are required to make out a bill and collect payment. I consider this yet another skill set – financial. In the good old days, I would simply tell the customer that they would receive a bill. When they wanted to know how much it would be I honestly did not have a clue. I might as well have told them to write a check and leave the amount blank so I could fill it in for their convenience later on. Customers now expect to know what they owe before the technician leaves. In many cases, the company expects the technician to collect payment. To create bills and collect payment technicians must be familiar with the company’s pricing policies. Many companies use price books which list prices for specific services. The price includes all aspects of the cost - parts, labor, overhead, and profit . Technicians bill customers according to the services they deliver. The technician needs to learn how the book is organized and be comfortable looking up prices in the book. Many technicians are uncomfortable using the books, making bills, and collecting payment. Often, companies just hand the new technician the book without much training. Although every company’s price book and billing procedure are unique, most companies now require their service technicians to produce bills and collect payment.

I think every HVAC/R program should have some example pricing procedures available to their students. The point is not to tell them what to charge, but to help them prepare to make bills using pricing policies that are prevalent in your area. A vendor for a price book that is used by several contractors in our area supplied us with a sample book. The prices do not reflect any particular company and all services are not in the book. Further, SAMPLE is written prominently across every page. But this book lets us inject a dose of reality into troubleshooting. Students should not only be able to track down the cause of the problem, they should also be able to find the service required to repair the system in the price book.

One thing that many students have a hard time with is the large price discrepancy between the cost of the part being replaced and the cost of providing the service. I emphasize that the customer pays far more for the technician’s expertise and service than they do for the part. The cost of the part is almost negligible. I point out that this is true for nearly any service business. Otherwise, the company cannot make money and their technicians cannot earn a good living. They are not cheating the customer by charging a high price. They are cheating the customer if they fail to deliver complete and competent service. We are called service technicians for a reason.