Wire Sizes To Carry On The Truck

[SKal]

Hey Guys,

Just getting started in the field. I know that MCA ratings on equipment will dictate the wire size from the breaker to the disconnect (typically wired by electrician) and from the disconnect to the contactor (CU whip). My question is what about all of the wiring after the contactor in condensers (and even wiring inside AHUs): going to the compressor, condenser fan, capacitors, relays, blower motors, heaters, etc? Is the size of all of these internal wires dictated by the amperage of the specific component the wire is hooking up to (I'm assuming this applies for 24V internal unit wiring - or does one gauge wire typically work for all 24V application in residential/light commercial HVAC)? I know most of this internal wiring is already sized and wired at the factory and we would just replace like for like, but I'm playing devil's advocate and thinking about a situation of an empty unit where I have to start from scratch and rewire everything internally. Do you guys carry all different sizes of wire in your truck if something should need to be replaced? What are the typical wire sizes I should be carrying on the truck for residential/light commercial HVAC? Also, what type of wire should this be THHN Stranded, other?

Thank you!

[Melting_in_NOLA]

90% of what you will see is burned connectors with a small amout of damage up the wire . it is simple as cutting off the damaged section and crimping on a new connector. there is almost always slack to do this. for those rare times where there is no slack , I collect wires from old units to keep on the truck to splice in ( like old fan motor, and compressor wires ) . I've NEVER had to rewire a whole unit from scratch. That would be a some sort of catastophic failure that would require a entire unit replacement .

[SKal]

Thanks! Yes, I was just using an extreme example where maybe you go to a job and the previous company maybe tried to do some weird things and maybe pulled a bunch of wires out of the unit. In this case, what do you do to make sure that you're using the right wire sizes to hook everything back up to spec?

[TechmanTerry]

I find that carrying THHN solid/stranded #14,12,10,8,6,4,red,white,blue,black,tan,orange,br own,pink,green,gray helps in most situations.

[JayMan7]

I did go to a unit one time that was so f*ed up by some hack that I had to rip everything out and completely re-do it.

The best thing you can do is cut out old wiring harnesses and save them...here's my collection

I like to match up wire colors when I'm making repairs. I also like the flexibility of the wire as compared to something you would by from a supply house that has that super stiff insulation.



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[Melting_in_NOLA]

and maybe pulled a bunch of wires out of the unit. In this case, what do you do to make sure that you're using the right wire sizes to hook everything back up to spec

See Rats nest of collected wires in the JayMan7 post above. I have one that looks just like that . Don't forget to keep those plastic molex plugs( you can't get them even if you tried ) I also have the big wires 4-6ga to large tonnage compressors that I carry . That covers all repairs , color coded and all . If I opened a unit totally rewired with THHN solid/stranded wire on a new service call that had a electrical problem ...... well, I would walk . ( Although is that any diffent than opening up a 60's era worthington that has all black wires ? or a carrier anything before 1985-all yellow - yipes)

[SKal]

So, if we have the large "rats nest" of different wire sizes on the truck, how do we go about determining what wire sizes we need to hook everything back up if we have to go in and re-wire a unit that has had it's wiring completely or even partially gutted (for both AHU and CU)? I know that would be a rare case in the real world, but I'm just trying to figure out the approach on something like this.

[pecmsg]

Order a harness!

[Snapperhead]

After almost 20 years I have a spaghetti pile just like JayMan that comes in handy alot

In addition to that , I have a roll of 12-2 and 10-2

More importantly , get you a THomas n Betts terminal kit . They are heavy duty

You will whimper when buying it , but its a nice kit

When looking for more terminals , look up 3M , or sometimes supply houses have decent brands also

[Hurst11]

Keep wires from scrap machines of all kinds. Keep a nest of em just like in precious photos. Keep some from outside units,gas furnaces and electric air handlers and when you run across a wire that needs replaced all wires have the size and rating on the wire, given it’s still the original wire and hasn’t been changed or shortened in some way. See what the rating on the wire is your replacing them go to your nest and find the one you need. Make sure to keep an array of crimp on wire fittings so you can make what you need.

[theoldscroll]

I find that carrying THHN solid/stranded #14,12,10,8,6,4,red,white,blue,black,tan,orange,br own,pink,green,gray helps in most situations.

You forgot #18 thermostat wire

[theoldscroll]

After almost 20 years I have a spaghetti pile just like JayMan that comes in handy alot

In addition to that , I have a roll of 12-2 and 10-2

Wires with factory crimp connectors are usually pretty good connectors.

[ehsx]

It just happens. Whatever I need , I buy a roll...eventually end up with a good inventory on the truck.

[AIRCON8]

i buy rolls of wire and sometimes i keep old one from replaced system

[ga-hvac-tech]

As noted earlier... when you scrap equipment, cut out (or better pull the connectors from the terminals)... and keep the wire...
I have a paint bucket of misc wire in the van... usually have what I need.
Another paint bucket has a couple of whips and some MX wire (armored)... in my area; the wire from the power switch to the furnace must be conduit or MX wire.

[Snapperhead]

Oh yeah , I have about 20 feet of MC cable , and the connectors

Plus I have a few 4" square metal boxes with blank covers , rec covers , switch covers

[ga-hvac-tech]

Oh yeah , I have about 20 feet of MC cable , and the connectors

Plus I have a few 4" square metal boxes with blank covers , rec covers , switch covers

Yeah, forgot those...

Double wide metal box and switch/outlet cover...

In this area... lots of installs have the power switch for the furnace on the side of the furnace...
Generally we replace it with a new metal box and new switch.

[RLJN]

I too scrap out and save control wiring from units. Most have at least one good usable factory crimp on them.
I have a 2' and 1' length of 1" PVC in a tool box drawer.
The wires are stuck in the pipes with a little ID end hanging out.
If too long then they are folded as needed, with the crimp end hanging out.
All good clean wires of all colors. You can stuff a lot of #14 thru #18 stranded wires in a 1" pipe.
You find the color/gauge/length you are looking for and pull it out of the pipe.

For longer lengths of 5-20', these are coiled up and stuffed into a 1 gallon clear plastic jar.
You can see the colors as needed. I also have reels of #14 stranded copper for commercial boiler control wiring in the shop. The jar gets the ends of the rolls.

[SKal]

Thanks guys! I'll take a look at salvaging as much as I can and maybe look into the Thomas and Betts terminal kits.