Contractor Talk - Professional Construction and Remodeling Forum banner

L1 L2 on 110 volt circuit

94K views 25 replies 7 participants last post by  DuMass 
#1 ·
Neighbour in village has a roof mounted hood fan on chip wagon/trailer. It keeps thermal tripping. I ask my HVAC guy to take a look. He said the fan motor (new) was reversed wired. His understanding (and mine as well) is that on a 110 circuit, hot is L1, neutral L2. Sticker on motor says the same. White from motor to L1, then choosing the wire for the rpm you want from the motor to L2.

Thoughts?
 
#2 ·
First off- How do you reverse wire a 110 volt motor ? There are only 2 wires. Yes, Hot is L1 & but it is a black wire & not a white. The neutral is a white wire. If you reverse these it is a dead short
Also, There is no choosing for different RPM's with an L2 neutral wire.

I'M sorry, I am not trying to be smart, but this makes no sense at all, and that is why there are no answers here !!
 
#3 ·
First off- How do you reverse wire a 110 volt motor ? There are only 2 wires. Yes, Hot is L1 & but it is a black wire & not a white. The neutral is a white wire. If you reverse these it is a dead short
Also, There is no choosing for different RPM's with an L2 neutral wire.

I'M sorry, I am not trying to be smart, but this makes no sense at all, and that is why there are no answers here !!
Maybe I wasn't as clear as I thought. The motor has 4 wires coming from it. The label on the motor says which wires to connect depending on what speed you want from the motor. In all 3 examples it says white to L1 and then the wire for the speed you want to L2.

When we opened the box, it was black (1550 rpm) from motor to L1 and white from motor to L2 with blue and red capped, each giving a different rpm when connected to L2.

I know full well which supply wire is hot and neutral. What the HVAC guy was saying was that the electrician didn't follow the label on the motor and just wired it black to black, white to white.
 
#6 ·
I suggest you contact the Manufacturer on this one-as it makes no sense to me that it was wired black to L1 from the factory & that configuration is not on that plate. It leaves alot to be desired ! Sorry, I was no help..............
There's no terminal board for this, just a connection box inside the housing. The fan internal wiring was done at the factory. It was the on-site electrician that connected it fan-black to L1, fan-white to L2.

Why the manufacturer chose to colour their wires in the manner they did is beyond me, but they did.

Based on the motor tag and fan docs, can we agree the electrician didn't follow wiring instructions? (hence my original "reverse wired" comment)
 
#7 ·
I would say the Electrician wired it wrong improperly per the manufacturers diagram, but how he wired it is normal for most applications. My question is why is the electrician wiring up the fan that would normally be the HVAC conractors job, or at least around here it is anyway? The diagram is calling for 3 different line feeds for change of speed so i am assuming there is a control box sending power to the fan? Did the fan come with a pigtail with all the properly color coded wires, if so then the electrician was wrong in not researching the proper wiring. If it did not come with a pigtail with the properly color coded wiring then i would say the electrician was doing what he felt was the proper way to wire it.
 
#8 ·
There is no external speed control, if I'm reading your post correctly. The documentation says to choose the rpm speed you need/want and connect the appropriate coloured wire to L2. There is a tag right on the interior housing beside the fan in plain view stating the wiring connection. I can understand an oversight in this situation regarding the black/white situation. What I don't get is why, when told and shown documention, he didn't connect it as specified. All wires were the colours stated on the tag.

As to my original question, would the wires being reversed (as wired by the electrician) cause thermal tripping?
 
#9 ·
I would say yes due to a possible direct short. What i fail to understand is how many wires are there at the fan motor? Is it just your typical black/white or are the other optional wires present? If there is going to be optional speed settings per color wire then there must be a speed controller somewhere, or are there more than the L1/L2 terminals to chose from? If the multiple wires were there at the fan motor and the diagram was in plain view then i would have to say he is at fault and being mis-wired could cause the tripping.
 
#11 ·
There's 4 wires coming from the fan motor. There is no connection board, only a 2x3 box. All 4 fan wires and the 2 supply wires (black/white)are in this box, the blue and red are individually capped. Of the 4 fan wires, tag says white to L1, then choose the fan rpm you want, connect the appropriate colour wire for that speed to L2 and cap the other 2. If you want raise, lower the rpm's later, change the wire from fan that's attached to L2. There's no external speed control as you are only connecting 1 of the remaining 3 wires to L2.

We checked, at the time, for an external thermostat, temperature probe but no go.
 
#10 ·
Woodchuck from what I am getting from OP is there are your standard 2 wires coming from power source, and 4 wires on the fan, alot of HVAC motors are like this. 1 wire on the fan is a common, the other 3 allow you to hard wire for the speed you wish, it is not something that can be controlled, you wire it one way get 1 speed etc. as long as it is wired with 1 wire to common and 1 to a speed select wire it should not make a difference on a 110 motor? right? unless there are capacitors involved? Not an electrician but was a licensed HVAC Tech for 5 years.
 
#12 ·
Woodchuck from what I am getting from OP is there are your standard 2 wires coming from power source, and 4 wires on the fan, alot of HVAC motors are like this. 1 wire on the fan is a common, the other 3 allow you to hard wire for the speed you wish, it is not something that can be controlled, you wire it one way get 1 speed etc. as long as it is wired with 1 wire to common and 1 to a speed select wire it should not make a difference on a 110 motor? right? unless there are capacitors involved? Not an electrician but was a licensed HVAC Tech for 5 years.

My HVAC guy did say there was a capacitor. It didn't involve any of the wires previously mentioned and was mounted to side of fan.
 
#13 ·
On a side thought, it is very possible the motor just has a bad thermal protector from the factory! Has anyone thrown an ameter on the wire to check amperage draw? Checked actual operating temp with a infrared thermometer?
 
#14 ·
Bad thermal?, possibly. Our intention was to correct the wiring to supply and take it from there. After I was told that the electrician just returned the wires to his original configuration despite docs to the contrary, I told the neighbour that short of getting another electrician to investigate, our involvement was finished.
 
#16 ·
This is why i was asking how it was suppose to be wired and what controlled the speed. I figured either there was a speed controller somewhere to vary the voltage or their was a different series of brushes to control the speed. I think the OP should just reverse the wires like the diagram stated and run it. If it still trips then the problem is elsewhere.
 
#21 ·
L1=neutral
L2=hot
in that context

Neutral to fan white
Hot to fan's black, blue or red, but the label you showed says its recommend to wire for blue(medium).

The fan is a piece of crap if it can't handle being used on max speed for extended period or there's a fan/motor mismatch causing it to be overloaded.

Disconnect black, cap off fan's black and red, then connect hot to blue.
Retry

I don't know what's so confusing.

Polarity is irrelevant in function of a motor. It's just a safety issue if you're switching neutral and leaving the fan always floating above ground.
 
#22 ·
L1=neutral
L2=hot
in that context

Neutral to fan white
Hot to fan's black, blue or red, but the label you showed says its recommend to wire for blue(medium).

The fan is a piece of crap if it can't handle being used on max speed for extended period or there's a fan/motor mismatch causing it to be overloaded.

Disconnect black, cap off fan's black and red, then connect hot to blue.
Retry

I don't know what's so confusing.

Polarity is irrelevant in function of a motor. It's just a safety issue if you're switching neutral and leaving the fan always floating above ground.
So you're saying there's no definitive designation for L1/L2 connections on 110 circuits and that in this instance they are interchangeable ?

If I'm understanding this right, with electric motors, fan white, being the common wire, goes to neutral and whatever fan rpm wire is chosen goes to hot irregardless of the understanding that L1 is supply hot ?

I'm not questioning what you've said, just trying resolve this for my own understanding.
 
#23 ·
I don’t know about that particular 120V motor, but many single-phase 208V-240V PSC motors can have their rotation reversed by changing the polarity of the Line 1 and Line 2 connections, so maybe the reversed 120V line / neutral connections with the run capacitor being present are causing a problem, since it sounds like it is a PSC type motor.

Not sure why they designated L1 for neutral and L2 for hot on that motor. Maybe the engineer that designed it was used to automotive electrical… who knows

Is the fan running with the correct rotation to provide air flow for cooling for the air-over motor?
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top