12/2 running to attic A/C unit - Romex gets warm

[5mall5nail5]

Hi guys -

Bombarding the forum with new questions as I just bought a house. There's a retrofitted A/C unit in the attic (house was without AC originally and had in-wall units). Theres a sloppy run of 12/2 Romex from the panel up into the ceiling into the attic, etc., and I am 90% sure it's to the A/C unit up there. My issue is that when it runs the cable, if held, gets warm. Not hot, but warm. It's 12/2 though I haven't traced it back to the exact breaker yet. I am going to look at the panel tonight. It LOOKS like it's on a 15A dual pole, though not sure.

Anyway - is a cable that gets warm something to be alarmed of? I don't like it, but an electrician here at work said "Nah, that's normal" but honestly it kind of peeves me. It's been this way for prob 10 yrs, but before I put it in the studs and behind the wall I want it to be right. I'll trace it proper tonight but if anyone can give feedback I'd appreciate it.

 

[offroadsteve]

I would agree with your electrician friend that "warm" is normal for a cable or wire loaded to a significant fraction of its capacity, which is most likely the case with your A/C unit.

The most commonly used wire size tables in the NEC show the allowed current for a given wire size without exceeding either 60 or 75 degrees CELSIUS. Note that that is 140 and 167 degrees Farenheit. Modern Romex (NM-B, the "B" being important) is rated to 90 degrees C, or 194 degrees F.

All that being said, if it were my house I would verify that the nameplate current for your A/C unit is within the allowable current for 12/2 romex, which should be 80% of 20 amps, or 16 amps. There is also a table for the required wire size for motors, but as long as we are only talking about the inside unit, the only motor is the blower fan, which is a fractional motor and probably not the limiting case here. 12/2 for the inside unit sounds about right in my experience. If we were talking about a compressor in the outside unit, I would be more worried.

 

[wyliesdiesels]

I would agree with your electrician friend that "warm" is normal for a cable or wire loaded to a significant fraction of its capacity, which is most likely the case with your A/C unit.

The most commonly used wire size tables in the NEC show the allowed current for a given wire size without exceeding either 60 or 75 degrees CELSIUS. Note that that is 140 and 167 degrees Farenheit. Modern Romex (NM-B, the "B" being important) is rated to 90 degrees C, or 194 degrees F.

All that being said, if it were my house I would verify that the nameplate current for your A/C unit is within the allowable current for 12/2 romex, which should be 80% of 20 amps, or 16 amps. There is also a table for the required wire size for motors, but as long as we are only talking about the inside unit, the only motor is the blower fan, which is a fractional motor and probably not the limiting case here. 12/2 for the inside unit sounds about right in my experience. If we were talking about a compressor in the outside unit, I would be more worried.

Incorrect. While Romex does have 90* C conductors, its ampacity is limited to the 60* rating. Also, the wire is running through a hot attic, and depending on the ambient temperature, the wire might also need to be derated due to the high temperature.

 

[5mall5nail5]

I would agree with your electrician friend that "warm" is normal for a cable or wire loaded to a significant fraction of its capacity, which is most likely the case with your A/C unit.

The most commonly used wire size tables in the NEC show the allowed current for a given wire size without exceeding either 60 or 75 degrees CELSIUS. Note that that is 140 and 167 degrees Farenheit. Modern Romex (NM-B, the "B" being important) is rated to 90 degrees C, or 194 degrees F.

All that being said, if it were my house I would verify that the nameplate current for your A/C unit is within the allowable current for 12/2 romex, which should be 80% of 20 amps, or 16 amps. There is also a table for the required wire size for motors, but as long as we are only talking about the inside unit, the only motor is the blower fan, which is a fractional motor and probably not the limiting case here. 12/2 for the inside unit sounds about right in my experience. If we were talking about a compressor in the outside unit, I would be more worried.

Thanks Steve. My panel has a spot marked "condenser" which is on a 30 dual pole. Not sure if it's the 12/2 on that, though. I have to confirm the home run of the 12/2. There are two breakers for the AC one looks like a 15A dual pole (but I have to confirm that tonight) and one is a 30A but I am not sure if the 12/2 is on the 30 or the 15. I do see a yellow wire coming out of the panel up and over which I am under the impression is USUALLY 10/2, but I don't see that as gospel anywhere. So hopefully they have the 30A dual pole feeding the condenser over 10/2 and the 12/2 that is warm is on (what looks to be but will be confirmed) a 15A dual pole.

Thanks for the reply I will follow up tonight with more info.

 

[Highbeam]

Modern romex colors

white is 14, yellow is 12, and orange is 10 gauge.

 

[awdblazer]

highbeam
also red is 12 but has red and black conductors (ie 240) whereas yellow is 12 and black and white conductors (ie 120)

 

[pattenp]

I think the 12-2 is to the air handler in the attic since it's just a blower to power. The 10-2 should be the outside compressor(condenser).

 

[rlitman]

I think the 12-2 is to the air handler in the attic since it's just a blower to power. The 10-2 should be the outside compressor(condenser).

Maybe, but every air handler I've seen has the power run parallel to the refrigerant lines. Power goes out to the compressor through a disconnect, and that disconnect kills power to both the compressor and air handler. So the air handler get's its power from the compressor.

So, could the romex coming from the panel be serving something other than the AC?

 

[5mall5nail5]

Maybe, but every air handler I've seen has the power run parallel to the refrigerant lines. Power goes out to the compressor through a disconnect, and that disconnect kills power to both the compressor and air handler. So the air handler get's its power from the compressor.

So, could the romex coming from the panel be serving something other than the AC?

It could be. Though it seems to be warm only after the AC has been running for a bit. I'll know more tonight. There's definitely two breakers on the panel labeled "Air Handler Attic" and "Condenser". The air handler looks like a dual pole 15 and the Condenser is a 30 dual pole.

 

[KenC]

Maybe, but every air handler I've seen has the power run parallel to the refrigerant lines. Power goes out to the compressor through a disconnect, and that disconnect kills power to both the compressor and air handler. So the air handler get's its power from the compressor.

So, could the romex coming from the panel be serving something other than the AC?

That would be unusual in my area. The compressor/condenser get their power independent of the air handler or freon lines. The unit just installed at my place has has a 30A/10ga run to the disconnect, direct from the panel. There is a separate 20A/12ga feed to the air handler/gas furnace.

Normal install here. Every house I've owned or worked on is like that.

 

[pattenp]

I'll still lay my money on the DP15 as being the breaker on the 12-2 that's serving the blower motor. The blower motor is most likely 230V.

It could be. Though it seems to be warm only after the AC has been running for a bit. I'll know more tonight. There's definitely two breakers on the panel labeled "Air Handler Attic" and "Condenser". The air handler looks like a dual pole 15 and the Condenser is a 30 dual pole.

 

[MrMark]

That would be unusual in my area. The compressor/condenser get their power independent of the air handler or freon lines. The unit just installed at my place has has a 30A/10ga run to the disconnect, direct from the panel. There is a separate 20A/12ga feed to the air handler/gas furnace.

Normal install here. Every house I've owned or worked on is like that.

Same here. The only wire running from the compressor/condensor inside is the thermostat/control low voltage AC wire. Never seen the setup referred to with power running with a line set.

Our outside unit is also run on 12 AWG (mc cable - can't breaker 12 nm-b above 20) with a 25 amp fuse and breaker as specified right on the rating plate. One ton small unit. The min required ampacity is stated right on the rating plate.

 

[Jim_No_Garage]

Same here. The only wire running from the compressor/condensor inside is the thermostat/control low voltage AC wire. Never seen the setup referred to with power running with a line set.

Our outside unit is also run on 12 AWG (mc cable - can't breaker 12 nm-b above 20) with a 25 amp fuse and breaker as specified right on the rating plate. One ton small unit. The min required ampacity is stated right on the rating plate.

The only time I've seen it done that way is with a mini-split.

240V to the outdoor condenser. The 120V for the Air handler is fed from the condenser.

Cheers

Jim

 

[2ManyProjects]

Hi guys -

Bombarding the forum with new questions as I just bought a house. There's a retrofitted A/C unit in the attic (house was without AC originally and had in-wall units). Theres a sloppy run of 12/2 Romex from the panel up into the ceiling into the attic, etc., and I am 90% sure it's to the A/C unit up there. My issue is that when it runs the cable, if held, gets warm. Not hot, but warm.

While it MAY not be getting hot enough to constitute a safety hazard in and of itself, I'd replace it with a heavier wire anyway. The simple fact that it is heating up to ANY perceptible degree is proof-positive that it is also imposing a significant amount of voltage drop. That will make the blower motor's life MUCH harder (and very probably shorter). It's also wasting power, perhaps enough of it to notice on your monthly bill, if the A/C system runs enough.

Plus, this gives you a golden opportunity to clean up that "sloppy" installation.

There's definitely two breakers on the panel labeled "Air Handler Attic" and "Condenser". The air handler looks like a dual pole 15 and the Condenser is a 30 dual pole.

I'd wager that you are correct on this part. But it's irrelevant to what I said above. Assuming the breaker is adequately rated for the load as it sits, there's no need to change it, even if you upsize the wiring.

 

[Kevin C]

While it MAY not be getting hot enough to constitute a safety hazard in and of itself, I'd replace it with a heavier wire anyway. The simple fact that it is heating up to ANY perceptible degree is proof-positive that it is also imposing a significant amount of voltage drop.

If I remember right 60°C or 140°F is allowable... To see if you have a problem that needs to be addressed you could measure the current and the voltage drop.

 

[MrMark]

The only time I've seen it done that way is with a mini-split.

240V to the outdoor condenser. The 120V for the Air handler is fed from the condenser.

Cheers

Jim

Must be a regional difference. Do you have an oil burner or separate furnace/boiler?

We use natural gas forced air units out here. The "air handler/evap core" sits on top of the forced air unit and shares the same blower. The combined inside unit is a small 120V load, basically the blower. The compressor outside is the larger 240 load.

 

[5mall5nail5]

Ok so I did confirm there is a 15A breaker on the position labeled "air handler". I still need to confirm if the wire getting warm is the handler wire or the condenser wire. When looking at the insulated freon line going toward the condenser outside there's a 12/2 romex attached to that as well. So, that can't be ideal since I think the condenser circuit breaker has a 30A breaker in position.

Here's my air handler:


Attic air handler by Jon Kensy, on Flickr

Having trouble making sense of this label. Can anyone identify any amp draw or anything??

Also, it says something on there about a heat accessory is this a heat pump unit?

 

[walrus]

Ok so I did confirm there is a 15A breaker on the position labeled "air handler". I still need to confirm if the wire getting warm is the handler wire or the condenser wire. When looking at the insulated freon line going toward the condenser outside there's a 12/2 romex attached to that as well. So, that can't be ideal since I think the condenser circuit breaker has a 30A breaker in position.

Here's my air handler:


Attic air handler by Jon Kensy, on Flickr

Having trouble making sense of this label. Can anyone identify any amp draw or anything??

Also, it says something on there about a heat accessory is this a heat pump unit?

The motor FLA is 4 amps 208/240, and then it lists different heaters that may or may not be in the unit, each one draws a specific amount of current and needs a specific breaker. I'm not sure which heater you have or don't have as the first one listed has no heater so.. From your breaker I'd say you have the first one listed which is 5 amps.

 

[5mall5nail5]

The motor FLA is 4 amps 208/240, and then it lists different heaters that may or may not be in the unit, each one draws a specific amount of current and needs a specific breaker. I'm not sure which heater you have or don't have as the first one listed has no heater so.. From your breaker I'd say you have the first one listed which is 5 amps.

So it must be the condenser 12/2 that is getting warm... I'll confirm.

 

[justsam]

If the 12/2 is feeding your condenser outdoor unit, and is on a 30 Amp breaker, you do need to get that changed.

The function of the breaker is to protect the wiring. A 30 Amp will not protect 12/2.

Change the wiring to 10/2.

 

[kenfath]

Is it possible the wire you report as being attached to the insulated freon line is the low voltage control wire that normally runs between the air handler and the compressor/condenser outdoor unit? Years ago I was around an installer that used 12 or 14/2 NM for the low voltage wire. Being young and naive I asked why he didn't use a thinner wire. His response was "Duh, This is the wire I have and it's the wire I'm using."

 

[5mall5nail5]

If the 12/2 is feeding your condenser outdoor unit, and is on a 30 Amp breaker, you do need to get that changed.

The function of the breaker is to protect the wiring. A 30 Amp will not protect 12/2.

Change the wiring to 10/2.

Thanks - yeah that's where I am thinking. I am thinking of picking up a 250' spool of 10/2 tomorrow and going to town. Think this is something better left to an electrician? I don't think so, I am completely capable of running cable, just wondering. Not sure what happens to the cable once it goes outside of my house/down the wall near the condenser/etc. I am going to pull the panel cover off tonight and see what is what inside just to confirm my suspicions.

Is it possible the wire you report as being attached to the insulated freon line is the low voltage control wire that normally runs between the air handler and the compressor/condenser outdoor unit? Years ago I was around an installer that used 12 or 14/2 NM for the low voltage wire. Being young and naive I asked why he didn't use a thinner wire. His response was "Duh, This is the wire I have and it's the wire I'm using."

Unfortunately I don't think so.


Untitled by Jon Kensy, on Flickr

 

[brewchief]

If the 12/2 is feeding your condenser outdoor unit, and is on a 30 Amp breaker, you do need to get that changed.

The function of the breaker is to protect the wiring. A 30 Amp will not protect 12/2.

Change the wiring to 10/2.

A 30 amp breaker may be perfectly legit on a 12/2 wire feeding an A/C condenser.

A/C equipment is treated like a motor load, the wire is to be sized according to the minimum circuit ampacity listed on the unit's name plate, the nameplate will also have a max fuse or breaker size.

A pic of the outdoor units nameplate will help a bunch here.

 

[MrMark]

Yes, with wire other than nmb. My understanding is that nmb 12 awg cannot be breakered above 20 even in this application under current code. 2008 nec did allow up to 25 on 12 nm-b, but 2011 cut it down to 20. So, the special motor loads allowances for increased breaker sizes would not apply to nmb. Is this not correct?

 

[kschauwe]

Run the air handler with the condenser off. See if it still heats up.

 

[Norcal]

If the 12/2 is feeding your condenser outdoor unit, and is on a 30 Amp breaker, you do need to get that changed.

The function of the breaker is to protect the wiring. A 30 Amp will not protect 12/2.

Change the wiring to 10/2.

Not necessarily true, rules for air conditioning are VERY different then normal branch circuits, there are situations (not this one) where 12 AWG could be on a 40A breaker & be code compliant. W/ HVAC equipment the fuses /circuit breakers are just for short circuit protection.

 

[ishiboo]

Not necessarily true, rules for air conditioning are VERY different then normal branch circuits, there are situations (not this one) where 12 AWG could be on a 40A breaker & be code compliant. W/ HVAC equipment the fuses /circuit breakers are just for short circuit protection.

Definitely. It all depends on what the nameplate on the AC unit says you should use. My AC is 50A breaker on 10/2 and it's correct.

 

[zmaxmotorsports]

Ok so I did confirm there is a 15A breaker on the position labeled "air handler". I still need to confirm if the wire getting warm is the handler wire or the condenser wire. When looking at the insulated freon line going toward the condenser outside there's a 12/2 romex attached to that as well. So, that can't be ideal since I think the condenser circuit breaker has a 30A breaker in position.

Here's my air handler:


Attic air handler by Jon Kensy, on Flickr

Having trouble making sense of this label. Can anyone identify any amp draw or anything??

Also, it says something on there about a heat accessory is this a heat pump unit?

Its got 240v running to the air handler so you can run the 240v motor,15a is the minimum to run the motor with out emergency heat strips installed in the unit.
If you install heat strips in the unit you need to upsize the wiring accordingly.
Have you serviced the airhandler checked filter/coil and motor lately?

 

[5mall5nail5]

Its got 240v running to the air handler so you can run the 240v motor,15a is the minimum to run the motor with out emergency heat strips installed in the unit.
If you install heat strips in the unit you need to upsize the wiring accordingly.
Have you serviced the airhandler checked filter/coil and motor lately?

Yes the unit was serviced prior to settlement the coil was cleaned and all.

I grabbed pics of the condenser today.


Outdoor AC wiring by Jon Kensy, on Flickr


Condenser unit by Jon Kensy, on Flickr

So it looks like it's on a 30A breaker with 12/2 wire and it says min. circuit ampacity 22.xA. Sooo, yeah going to replace the 12/2.

 

[brewchief]

Romex should not be run outdoors like that either, technically it can't even be in a short piece of flexible conduit although it is done that way all the time around here to get it to the disconnect. From the disconnect to the A/C a premade "whip" of sealtite and thhn is normally used.

 

[5mall5nail5]

hmm so what should I do?

 

[brewchief]

hmm so what should I do?

Either run 10/2 and use a piece of flexible conduit outside even though it's not technically right or use a type of wire that is rated for wet conditions.

Around here 6/2 alum service entrance cable is used to wire A/Cs quite a bit since it needs no conduit outdoors and is pretty cheap.

 

[Norcal]

Either run 10/2 and use a piece of flexible conduit outside even though it's not technically right or use a type of wire that is rated for wet conditions.

Around here 6/2 alum service entrance cable is used to wire A/Cs quite a bit since it needs no conduit outdoors and is pretty cheap.

The unit will not be able to be wired w/ AL cable, the whip between the disco & the unit has to be wired w/ copper, it will be a lot easier just to use 10/2 NM cable.

 

[brewchief]

The unit will not be able to be wired w/ AL cable, the whip between the disco & the unit has to be wired w/ copper, it will be a lot easier just to use 10/2 NM cable.

Sorry I meant wire to disconnect with the 6/2 then use a premade whip made of 1/2" sealtite and thhn/thwn 10ga wire.

 

[5mall5nail5]

6/2!? That seems hugely overkill for this unit.

 

[2ManyProjects]

6/2!? That seems hugely overkill for this unit.

Aluminum vs. Copper. It's a whole different ballgame.

 

[5mall5nail5]

Aluminum vs. Copper. It's a whole different ballgame.

Oh yeah, true. Didn't realize Al.

Ok so - I got a fishing tool and popped it out the bottom of the "gutter" conduit thing they have going...


Fish hook through by Jon Kensy, on Flickr

Hooked the 10/2 wrapped it all up in electrical tape, up it goes... but it got tight at the top. The insulation on the 10/2 is torn in a couple spots up in the attic once I managed to pull it through. Ugh. Going to have to redo the pull or figure something else out, I think. I can't remove the 12/2 because its all taped to the condenser line. Ugh.

I did replace the ghetto wiring from the junction box, though.


Replaced wiring by Jon Kensy, on Flickr


Replaced wiring by Jon Kensy, on Flickr

 

[5mall5nail5]

Worth showing - this is how they got the AC piping and romex down the side of the house.

Sigh.


Attic AC wiring by Jon Kensy, on Flickr

And now I see why my 10/2 is getting the insulation torn a little.

Would it be ok to do a junction box in the attic? I am thinking of pushing the 10/2 down a different path down this stupid "conduit" since pulling it is bringing it up this way with sharp edges. If I pushed it I could direct it to the other side. But then I might need to do a junction box.

 

[wyliesdiesels]

If that is a gutter down spout, I gotta say that thats the most ghetto raceway Ive seen for an AC condenser. My house has a nice sheetmetal troff!

As far as the wire path- yes u could use a junction box or run liquid tight down the wall if u dont mind looking at it!

 

[5mall5nail5]

I agree it's lame, thats why I am redoing it. Just need an extension ladder.