HVAC conductor and breaker sizing - AGAIN???

spurlockda

Member
Location
Nevada
Hi guys,

Sorry to bore you guys with this topic again but I'm having issues with an HVAC company that is installing a new system in my Mother's house. She is a 90 yr old widow (Dad passed away 15 yrs ago) and I just recently retired from the Navy after 30yrs and I am now dedicated to making her home safe and sound for her remaining yrs.

Here are some details:
Distance from main breaker panel (MBP) (in basement) to outside corner of house (adjacent to and right above MBP: 48"
This corner is where the A/C Compressor unit disconnect (they have provided a 60amp non-fused disconnect box) will be. The corner mounted disconnect will be in a direct line of sight from the compressor.
Distance from corner disconnect to compressor: 25'

The manufacturer's (Goodman) label plate says "Max. Fuse Amps or Max. Circuit Breaker 40" and
"Min. Circuit Amps 23.9" and "A.C. Volts 208 - 230"

The problem I'm having is that the installer is trying to install the 60amp disconnect, 8 awg whip, and 60 amp breaker. I've told them that all of that is oversized and that based upon the 2014 NEC, they should be using a 40 amp breaker, 10 awg wire and 40 amp disconnect.

I have researched everything I can find (NEC, local codes, Mike Holt forums and etc.) and cannot find out why they are so insistent on their plan. The installers are falling back on the old "That's what the boss told us to use."

Any help would be appreciated and I'll show them your all's comments - unless I'm wrong in which I will tuck my tail between my legs and walk away.

Thanks,
Dave
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
The only issue is that the OCPD needs to be a maximum 40 amps, everything else is OK.
 

edward

Senior Member
You may even be able to get away with #12 and a 40A fuse.

Show him the name plate instructions that say "MAXIMUM ocpd 40A"

However, I don't think you will find a 40Amp disconnect. You HAVE to go with a 60Amp rated pull out disconnect.
 

JFletcher

Senior Member
Location
Williamsburg, VA
Installer may be accounting for voltage drop with #8 wire - I read 73' from panel to HVAC, probably 80-90' for wire length. The disco's we use are rated for anywhere from #14 to #1 wire, and dont really have an amperage rating (aside from what #1 can carry). The breaker should be 40A max per mfg instructions (110.3(B)).

The real worry/concern is that they run and test all the ductwork correctly. If it's not done right, you could lose 30% or more of your heating/cooling to dead spaces (attics, crawlspaces, walls).
 
Hi guys,

Sorry to bore you guys with this topic again but I'm having issues with an HVAC company that is installing a new system in my Mother's house. She is a 90 yr old widow (Dad passed away 15 yrs ago) and I just recently retired from the Navy after 30yrs and I am now dedicated to making her home safe and sound for her remaining yrs.

Here are some details:
Distance from main breaker panel (MBP) (in basement) to outside corner of house (adjacent to and right above MBP: 48"
This corner is where the A/C Compressor unit disconnect (they have provided a 60amp non-fused disconnect box) will be. The corner mounted disconnect will be in a direct line of sight from the compressor.
Distance from corner disconnect to compressor: 25'

The manufacturer's (Goodman) label plate says "Max. Fuse Amps or Max. Circuit Breaker 40" and
"Min. Circuit Amps 23.9" and "A.C. Volts 208 - 230"

The problem I'm having is that the installer is trying to install the 60amp disconnect, 8 awg whip, and 60 amp breaker. I've told them that all of that is oversized and that based upon the 2014 NEC, they should be using a 40 amp breaker, 10 awg wire and 40 amp disconnect.

I have researched everything I can find (NEC, local codes, Mike Holt forums and etc.) and cannot find out why they are so insistent on their plan. The installers are falling back on the old "That's what the boss told us to use."

Any help would be appreciated and I'll show them your all's comments - unless I'm wrong in which I will tuck my tail between my legs and walk away.

Thanks,
Dave
Actually did almost the same thing a few days ago: Min ckt ampacity 13, max OCPD 20 (I think). Grabbed a 60 amp non fused pullout, its what they had and it was cheap, grabbed one of those 6 foot sealtite whips made up with #10 conductors already installed - didnt have any 14 or 12 THHN with me. IT probably cost $4.37 more than the minimum sized parts. What are you worried about, that is is incorrect or they are wasting money?
 

rlundsrud

Senior Member
Location
chicago, il, USA
Forget about the pullout disconnect, that's just what the name implies, a disconnect. Focus on what size breaker they have in the panel feeding it. As long as that is no bigger than 40 amps you're good to go.
 

kwired

Electron manager
Location
NE Nebraska
The manufacturer's (Goodman) label plate says "Max. Fuse Amps or Max. Circuit Breaker 40" and
"Min. Circuit Amps 23.9" and "A.C. Volts 208 - 230"

The problem I'm having is that the installer is trying to install the 60amp disconnect, 8 awg whip, and 60 amp breaker. I've told them that all of that is oversized and that based upon the 2014 NEC, they should be using a 40 amp breaker, 10 awg wire and 40 amp disconnect.
Standard safety switches jump from 30 amp to 60 amp for standard sizes if you need 40 amps you are stuck with 60 as your minimum.

You can find 40 amp motor rated switches that would work for this application - they will cost at least 3 or 4 times what a 60 amp pullout type "AC disconnect" usually costs. I can get a "AC disconnect" for about 10 bucks but spend 40 to 50 on a two pole 40 amp motor switch - and it still needs an enclosure and cover to go with it.

HVAC guys are known to stock "whips" for use in connecting their AC units. Conductor size may be overkill, but if it is all they have it will cost more to run after different materials then the cost difference is worth just to reduce six feet of conductor from 8 AWG to 10 AWG. There isn't much for single phase units that can't use an 8 AWG whip, which I'm sure is why they stock them that size.
 

spurlockda

Member
Location
Nevada
Compressor run

Compressor run

Actually did almost the same thing a few days ago: Min ckt ampacity 13, max OCPD 20 (I think). Grabbed a 60 amp non fused pullout, its what they had and it was cheap, grabbed one of those 6 foot sealtite whips made up with #10 conductors already installed - didnt have any 14 or 12 THHN with me. IT probably cost $4.37 more than the minimum sized parts. What are you worried about, that is is incorrect or they are wasting money?

I guess i was was more concerned with incorrect. I'm still learning and all - don't want to piss off my mentor. It's hard enough here where fundamentally they don't know how to say 'Code'. I worry about Home Owner's insurance. I also want to make sure my Ol' Mom is safe and secure. Normally I live on the other side of the country from her so taking care of the house for her is hard.

I asked if I was going to meet the inspector (my sneaky way of letting the installer know I was concerned by permits and inspections) and I still haven't gotten an answer to that.

As long as it's not going to be code wrong to use oversize conductors and Disconnect, I guess I am OK with it.

I guess I overlooked this: For the run from the disconnect to the compressor (25') I think I would want them to run #10 THWN inside of schedule 40? Is that right or since they used #8 in the whip to the disconnect, will they have to run #8 inside the PVC to the unit?
 
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brian john

Senior Member
Location
Leesburg, VA
If the CB in the Panel is 40 Amp you should be OK (sight unseen) If I were you I would be pleased they are upsizing the conductor and most likely if I was installing this I'd tell you to get lost.
 

JFletcher

Senior Member
Location
Williamsburg, VA
The 25' of PVC... outside... would it be mounted between two boxes, or just between the disco and the other end to a sealtite whip? If it's the former, it'll need an expansion fitting. I can easily see 60 if not 90* temp variation in NV. 352.44.

premade whip would indicate a j-box from conduit to sealtite...
 

spurlockda

Member
Location
Nevada
Yep oversized breaker

Yep oversized breaker

They left a 60 amp breaker for inside the main panel. They left the 60 amp breaker, 60 amp disconnect (with sliding switch-like control inside), number 8 red, black and green liquid tight whip and that was it. Everything was/is delayed because I had some excavation to do to make room for the outside compressor unit. I am putting the all right stuff (hopefully) into a different box until I see what they come up with - so I can be as prepared as possible for whatever happens I have 40 amp breaker, I'll use their disconnect, and I have three rolls (1 ea. red, black and green in 10 AWG and also 8AWG (I'm assuming that if we use their no. 8 whip out to the d/c, we'll have to use no. 8 out between the d/c and the unit?) and I have the sched 40 grey pvc for/as the buried raceway from the disconnect to the unit. Hopefully they'll bring all of the correct stuff and I can take all of my stuff back for a refund :roll:

Thanks you you all for making me smarter! Dave
 
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infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
They left a 60 amp breaker for inside the main panel. They left the 60 amp breaker, 60 amp disconnect (with sliding switch-like control inside), number 8 red, black and green liquid tight whip and that was it. Everything was/is delayed because I had some excavation to do to make room for the outside compressor unit. I am putting the all right stuff (hopefully) into a different box until I see what they come up with - so I can be as prepared as possible for whatever happens I have 40 amp breaker, I'll use their disconnect, and I have three rolls (1 ea. red, black and green in 10 AWG and also 8AWG (I'm assuming that if we use their no. 8 whip out to the d/c, we'll have to use no. 8 out between the d/c and the unit?) and I have the sched 40 grey pvc for/as the buried raceway from the disconnect to the unit. Hopefully they'll bring all of the correct stuff and I can take all of my stuff back for a refund :roll:

Thanks you you all for making me smarter! Dave

Just curios why you're buying material if you've contracted with someone else to do the job?
 

spurlockda

Member
Location
Nevada
Installation concerns

Installation concerns

That was my thought exactly. If I contracted them to do the job, why am I buying stuff?

A little background first. I live and work in the construction trades in Las Vegas but my Mom lives in WV. After I retired from the Navy (30yrs), I went to WV because I knew her house needed repairs and that she could no longer climb stairs and we needed to set her up on the ground floor. Her house was built in 1938 and the last time anything was done was 15 yrs ago when my Dad passed away.

Unfortunately I discovered that the house needed to be rewired, replumbed, the furnace replaced and since there was no A/C except window units, a new central A/C system installed.

So far it has been a comedy of errors with the local talent. For example, when I had the building inspector come out to check the plans for the new downstairs bathroom, he told me to not worry about the permits: "We don't use those much around here." Then, I hired a "Master Electrician" for the rewire job and after helping and watching him work, my concern was growing (which was based upon the Apprentice training from out here in Nevada) so I started asking him about his experience and licenses. Turns out he was a Master coal mine electrician. He didn't have the traditional Master License???

Then came the HVAC guys (again I have a good familiarity with HVAC from my work in LV) and it got kinda interesting with them. Generally they did a good job but they started doing some shade tree mechanics and when I called them out on it, they didn't have the right stuff and had to go get it. I ask them about where the licensed electrician was for doing the electrical for the HVAC system and they replied that they didn't need one here (in WV I guess). Then I asked about permits and they said that they didn't have any with them-that the boss must have them??? That's when I really started worrying. Here's another example. They installed a steam humidifier and installed two separate circuits, one for the furnace and one for the humidifier. Two wire runs, two c/b's.

Oh by the way, the "master electrician" rewired one and one half rooms and had to go take care of another job. That was 6months ago. Oh yeah, I was digging through all the stuff he bought (with my money) and found that the cable he bought for the service drop and feeder was for mobile homes. Southwire 4/0,4/0,2/0,4 AlumaFlex, USE-2.

So now I'm checking everything. So now my question is back to the circuit for the outdoor compressor. The #8 whip from the c/b panel (in the basement) to the d/c box (on the brick wall just outside and up from the basement c/b panel. Here's my question: Since they started with #8, will they have to run #8 from the d/c box to the compressor unit? My understanding (which may be wrong (apprentice)) is that you cannot change wire gage in a branch circuit.

whoops, I forgot one: is there a specialized breaker req'd for the compressor unit? I was studying up on the specs and the LRA loads seem pretty high for a regular Ol' 40 amp breaker. On the spec plate it says (Time delay fuse or HACR circuit breaker required). I examined the one that they left and I can't find anything on the breaker that says HACR. I'm thinking the HACR is Heating Airconditioning R?

I also have some questions related to the main house rewire and service entrance cables but I won't hijack my own thread and I'll start a new thread.

Sorry to be long winded but I wanted to make sure I didn't miss any details - Navy training I guess :D
 
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infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
Here's my question: Since they started with #8, will they have to run #8 from the d/c box to the compressor unit? My understanding (which may be wrong (apprentice)) is that you cannot change wire gage in a branch circuit. No you can change the condcutor size.

whoops, I forgot one: is there a specialized breaker req'd for the compressor unit? I was studying up on the specs and the LRA loads seem pretty high for a regular Ol' 40 amp breaker. On the spec plate it says (Time delay fuse or HACR circuit breaker required). I examined the one that they left and I can't find anything on the breaker that says HACR. I'm thinking the HACR is Heating Airconditioning R? No, all modern CB's are HACR rated.
:)
 

kwired

Electron manager
Location
NE Nebraska
Oh by the way, the "master electrician" rewired one and one half rooms and had to go take care of another job. That was 6months ago. Oh yeah, I was digging through all the stuff he bought (with my money) and found that the cable he bought for the service drop and feeder was for mobile homes. Southwire 4/0,4/0,2/0,4 AlumaFlex, USE-2.

So now I'm checking everything. So now my question is back to the circuit for the outdoor compressor. The #8 whip from the c/b panel (in the basement) to the d/c box (on the brick wall just outside and up from the basement c/b panel. Here's my question: Since they started with #8, will they have to run #8 from the d/c box to the compressor unit? My understanding (which may be wrong (apprentice)) is that you cannot change wire gage in a branch circuit.

whoops, I forgot one: is there a specialized breaker req'd for the compressor unit? I was studying up on the specs and the LRA loads seem pretty high for a regular Ol' 40 amp breaker. On the spec plate it says (Time delay fuse or HACR circuit breaker required). I examined the one that they left and I can't find anything on the breaker that says HACR. I'm thinking the HACR is Heating Airconditioning R?

I also have some questions related to the main house rewire and service entrance cables but I won't hijack my own thread and I'll start a new thread.

Sorry to be long winded but I wanted to make sure I didn't miss any details - Navy training I guess :D
That quad cable is marketed for use with mobile homes, but is suitable for most any place you would need same conductor sizes. It better have more markings then just USE-2 though, otherwise it is not rated for use inside of buildings. Does it by chance also have RHW, or similar marking on it?

All miniature breakers for past 30 or so years have been HACR rated.

Conductor sizes can change within a circuit, often when long lengths are involved you will find a large conductor for the bulk of the run to help with voltage drop but may see a reduction at some point because the end equipment can not physically handle the larger conductor in it's terminals.
 

ritelec

Senior Member
Location
Jersey
You may even be able to get away with #12 and a 40A fuse.

Show him the name plate instructions that say "MAXIMUM ocpd 40A"

However, I don't think you will find a 40Amp disconnect. You HAVE to go with a 60Amp rated pull out disconnect.
Since the MCA is 23.9 amps the disconnect could be a 30 amp.
?

Confirming please.

Since mca is 23.9 amps the conductors AND disconnect would be rated for 30 amp
While the ocp is the circuit breaker rated at 40 amps.

The disconnect is to be sized as the conductors. In this case a 60 amp disconnect is not required.

Not micromanaging. Confirming for my head. Thank you.
 
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