I started working as a tech when I was 17 years old, fresh out of tech school. My first winter out on my own I went to a service call in an older part of Orlando, a part of town I had never worked on before. It was an especially cold winter that year, and the service call was for insufficient heat.
When I arrived, I found the system was a really old GE straight cool system. After testing the system, I found the system had a 10kw heater, but only 5kw was working. After a closer look, it was discovered that 5 KW of the heat was disconnected. This was no problem for me; wiring was always my specialty! I grabbed some #12 stranded and had that puppy heating in no time.
#1 – It smoked like a chimney and set off every alarm in the house
#2 – Once I got the doors and windows open and the smell cleared out as best I could it got me thinking… How long has it been since that second 5kw was connected?
When I looked closer I saw that the feed wire going to the air handler was only #10… then it dawned on me.
The REASON they had one-half of the heat disconnected was because the breaker and wire size were only rated for 5kw. Why did they a 10kw you might ask? Likely it's what they had on the truck and they figured if they disconnected one-half it would be safe.
Lessons learned –
#1 – Never assume that a system was installed properly to begin with and keep an eye out for proper feed wire size.
#2 – Don't use improperly rated heat strips or other rated parts and simply make an “alteration”. When the next technician arrives he likely won't understand what you did. At best you confuse him, at worst you kill him.
Connecting more than one wire on or under a single lug or connection point is called “double lugging” and it is ONLY allowed in line voltage wiring under one condition according to NEC 110.14
If the terminal, lug or connector is specifically rated for more than one wire
In the case of a conductor splice like a wire nut or a split bolt, they are only designed for 2 wires unless they specifically state otherwise on the box on the connector itself or in the instructions / product data.
This means that wiring in a surge protector under the same lugs as the main, or jamming as many wires as you can make fit under a split bolt or wire may be common, but it is not allowable according to NEC 110.14
HVAC techs and installers will often double lug contactors when making a repair, or they will connect to the closest, easiest point when installing a 120v or 240v accessories like a UV light , humidifier or air purifier.
In all of these cases is is best to take a few minutes and find an approved and permanent method of making the connection instead of taking the easy way out.
It is also worthwhile to mention that some connections are rated for copper only and will be marked CU while others designed for aluminum will be marked AL or ALR. Some will be marked as CU / AL which means that either copper or aluminum may be used but not necessarily that copper and aluminum may be MIXED.
There are very few connection that allow the mixing of copper and aluminum and if they do they must be specifically listed for that purpose.
I was about 13 years old the first time I bent EMT with my uncle. We were doing a renovation at a church, and watching him bend EMT and then getting to do it MYSELF was a truly religious experience.
There are a few things in the trade where workmanship really comes into play such as copper pipework, making up a panel or fabricating ductwork… bending EMT belongs on that list. While most commercial electricians do it every day, HVAC techs and installers only run into an application where we do it on a rare occasion. When that does happen its good to have a basic understanding of how it works. In this video Juan from the The Air Conditioning Guy channel goes over some quick basics on bending EMT
Erich Vinson is a tech from Colorado and one of the most entertaining people I interact with online. He wrote this quick tech tip on stripping back the outer jacket properly on control wires and it happens to also be something I preach. Thanks Erich.
In the first picture (above), you can see what happens when you try to use a pair of wire strippers to remove the jacket. It damaged the wire underneath. Instead use the pull string when you strip the jacket off of a low voltage (control) cable.
Use your strippers to remove about three inches of the jacket (or cut into the end like I show above – Bryan), and use the pull string to peel away the jacket, as is shown in the below.
Then, cut off the wires just below where you used your strippers.
The result will be low volt wires with no damaged insulation, and no hard to find low voltage short circuits.
When you are checking a unit of any kind you should be keeping your eyes open for signs of arcing and melting at all of your wire connections and contact points. We find issues with melting terminals on contactors and in disconnects regularly, but rarely do we think about the relationship between circuit ampacity and wire size and the connections to our equipment.
First, consider the fact that a #10 wire doesn't always have an ampacity of 30 amps, it has an ampacity of 30 amps with a 60° Celsius rated assembly at 30° Celsius ambient.
Now, look carefully at the wire and the contactor at the start of the article.
The wire (conductor) is rated at 90° and the contactor is rated at 75° when torqued down to 22 in/lbs on screw type terminals and 40 in/lbs on lug type.
So the entire assembly is only as good as the weakest link and the weakest link is the terminals and the terminals are only as good as the contact they are making.
Conclusion: The termination (connection) points are usually the weakest point of the circuit
When sizing conductors don't forget ANY of the termination points. From the breaker to the disconnect to the unit, every termination point should be properly connected and the rating checked if you intend to use any ampacity other than 60° Celsius.
Check those connections. make sure they are snug and that they are properly suited for the ampacity of the circuit.
The photo above is from a video one of my techs took of proper condenser cleaning. I must say, he did a GREAT job of cleaning the coil and he was very careful with the top. However I STILL would have liked to see the top get completely removed during a full maintenance. Pulling the top usually just requires disconnecting the fan wires, cutting a few wire ties, taking out some screws and then removing the fan grille or the entire top and laying it top down in the grass.
This is ACTUALLY how I performed a maintenance, even before I started my own business.
Here is why –
If you wash from the outside – in you are not doing the best possible cleaning. Everyone knows that washing from the inside out is a superior method of cleaning.
If you lay the fan on top of the unit (like shown above) you risk twisting / damaging the wires, scratching the paint and bending the fan bade.
When you pull the top entirely you can more easily clean the dirt and leaves from the inside of the condenser, this should also be part of a proper maintenance because that dirt can reduce coil capacity as well as hold moisture against the base, compressor and accumulator resulting in corrosion.
With the top off you can get a better view of any wire rubouts or potential wire rub outs and address them before they cause a problem.
You can also visually inspect the compressor terminals for signs of heat and corrosion, potentially preventing a major issue such a terminal failure / “blowing a terminal”.
Obviously it will take about 5 mins longer and you will need to rewire it properly with the terminals snugly installed.
So what do you think?
P.S. – Here is the video in case you want to see what I mean and yes… he knows that cleaner isn't always required when washing a coil but he used it for demonstration purposes