Air Conditioning Wire Sizing

[Lucia1222]

There's a lot of confusion between our industries but every carrier outdoor residential unit I've seen accepts a breaker at the panel not just fussed disconnects. Mitsubishi on the other hand is the one that says fuses only. The internals obviously will have their own requirements but those actually use taps based off of the actual usage of each load. That's how all small controls are done with maybe one fuse for the whole control section.

Mini spits definitely are a different breed work amazing though I’ll be honest rarely work on them the don’t break often as far as troubleshooting on those I have very little experience with them hopefully that changes because I wanna learn them I think all the inverter stuff is gaining popularity quick

 

[Dennis Alwon]

Mini spits definitely are a different breed. They work amazing though I’ll be honest I rarely work on them. They don’t break often and as far as troubleshooting on those I have very little experience with them. Hopefully that changes because I wanna learn them I think all the inverter stuff is gaining popularity quick

I re-wrote your post above in this post. Look at how much easier your post is to read when there are punctuation marks. It is really helpful if you use them. Thanks

 

[mtnelect]

The number one problem I find on "Ductless" systems installed by others are:
1) Control cable(s) mis wired, especially when changing colors. As in extending a cable with a different color scheme.
2) Multiple units, refrigerant lines crossed.

 

[Lucia1222]

The number one problem I find on "Ductless" systems installed by others are:
1) Control cable(s) mis wired, especially when changing colors. As in extending a cable with a different color scheme.
2) Multiple units, refrigerant lines crossed.

So far it’s been mostly leaking flares for me.

 

[mtnelect]

So far it’s been mostly leaking flares for me.

Nice to see another HVAC person on this forum !

 

[kwired]

Makes sense to me and I’m not a electrician I showed everything I got I found the people don’t believe it’s safe but if you watch a air conditioner shut off on overload the breaker doesn’t trip it cools down and comes back on

Motor overload is what is cycling here - particularly on smaller single phase units.

Fuse or circuit breaker on motor and air conditioner compressor circuits is for short circuits and ground faults. They often would not hold during startup if selected for overload protection. But the also required motor overload protector not only protects the motor/compressor from overload but inherently protects the supply conductors as well. They will only draw excess current for very brief period during starting and after that they will be protected from overloading. If it fails to start, either the motor overload or the fuse/breaker ultimately will open the circuit.

 

[Lucia1222]

Nice to see another HVAC person on this forum !

In my opinion hvac is way behind other trades everyone goes straight to I’m an installer or I know service.The field isn’t good a fielding people for the job.especially these smaller companies there’s no end game the money vs skill set is way off.nothings more annoying than someone with 1 year installing try and reinvent the wheel.

 

[kwired]

And if you think about it carrier does not want to be known for burnt wires all through their units so they want to protect their small stranded wires too that would mean you would have to protect it at the end off the line with that you make it safe

Their internal conductors should be able to handle anything the motor overload will allow.

If they can't handle a short circuit or ground fault, then possibly the unit is used where it's rated fault current level has been exceeded, which goes well beyond just selecting overcurrent protection setting.

I think most units are only rated for 5kA available fault current max unless otherwise marked.

 

[Lucia1222]

I wish there was a way to make the people who install them understand this at least more widely known.every time it’ll turn into a d*** measuring contest.

 

[mtnelect]

Motor overload is what is cycling here - particularly on smaller single phase units.

Fuse or circuit breaker on motor and air conditioner compressor circuits is for short circuits and ground faults. They often would not hold during startup if selected for overload protection. But the also required motor overload protector not only protects the motor/compressor from overload but inherently protects the supply conductors as well. They will only draw excess current for very brief period during starting and after that they will be protected from overloading. If it fails to start, either the motor overload or the fuse/breaker ultimately will open the circuit.

Since summer weather is now arriving soon, I thought it was appropriate to list the number problem for split HVAC system(s):
1) Combination Capacitor(s) are the number one cause of Hermetic Compressors not starting. In our Maintenance Contracts we include new capacitor(s) every two years. As the summers get hotter each year the condensing units really get a workout. On a service call we arrive and see the hermetic kicking out on the internal overload. 95% of the time it's the capacitor(s) so if you haven't replaced them in a long time, do it now and save yourself a headache !

 

[kwired]

Since summer weather is now arriving soon, I thought it was appropriate to list the number problem for split HVAC system(s):
1) Combination Capacitor(s) are the number one cause of Hermetic Compressors not starting. In our Maintenance Contracts we include new capacitor(s) every two years. As the summers get hotter each year the condensing units really get a workout. On a service call we arrive and see the hermetic kicking out on the internal overload. 95% of the time it's the capacitor(s) so if you haven't replaced them in a long time, do it now and save yourself a headache !

Why are they failing? every two years seems too short of lifetime.

Are your replacements lasting longer than the originals or are they same brand as originals?

Most these you would think should only need replaced just once, if that, during the expected lifetime of the unit.

I change a lot more start capacitors than I do run capacitors on other motors. Many of those are either just the terminal pulls off the unit or centrifugal switch not working properly and leaving start in the circuit for too long.

 

[mtnelect]

Why are they failing? every two years seems too short of lifetime.

Are your replacements lasting longer than the originals or are they same brand as originals?

Most these you would think should only need replaced just once, if that, during the expected lifetime of the unit.

I change a lot more start capacitors than I do run capacitors on other motors. Many of those are either just the terminal pulls off the unit or centrifugal switch not working properly and leaving start in the circuit for too long.

Hermetic compressors are manufactured to very high tolerances and withstand a lot of abuse. But a HVAC compressor has to deal with very high refrigerant pressures in addition to the summer heat. Heat is the main culprit. Heat dries out the capacitor(s) and changes the capacitance value. Just like breaks on a car, you don't notice it until it's too late. Capacitors are inexpensive so it makes sense to replace them, verses waiting for them to fail in a 100 + degree day.