100 Amp breaker with #4 feeding A/C disconnect

[kwired]

Seems the breaker might obsolete. But as others have mentioned there other compliant solutions.

You mentioned earlier it is Iline. I-line is notn obsolete although certain breaker types that fit I line panels have been discontinued but there most likely is something else available that will work in place of the type you have. Basically need to know voltage and AIC rating needed to determine what will work. 480 or 600 volt breakers will work on 208 or 240, but 208 or 240 volt breakers can not be used on 480 or 600 volts. They all plug onto any I-line bus.

How long is the run to the disconnect? It possibly can still be compliant if it fits conditions of any feeder tap rules and you do have proper overcurrent device at the disconnect. More than 25 feet and inside the building, forget it you need proper protection on supply end.

 

[Little Bill]

Sorry about all the oops messages. I will be more careful about that going forward.

There is also, “the it’s worked fine these way for years”, so I wanted to be sure I was justified in my recommendation.

The "Oops" message was not directed at you. The Forum is experiencing problems, and when it does, we get an "Oops" message.

 

[LarryFine]

The "Oops" message was not directed at you. The Forum is experiencing problems, and when it does, we get an "Oops" message.

Yes, I have been unable to get past a generic page several times in the past few days.

 

[BarryO]

My intention, would be to leave the 100 amp breaker if replacing the 70 amp fused disconnect would be compliant. But I don’t believe that would be.

Why not? The compressor overload protection is permitted to be also be the same as the branch circuit protection, but is not required to be. Just put in a 60A or 70A fused disconnect.

 

[wwhitney]

Why not?

#4 Cu is not normally allowed to be protected at 100A. It would either need to meet one of the tap rules, or perhaps be spliced in a separate enclosure to #3 Cu that terminates on the 100A breaker, if the insulation is rated 90C.

Cheers, Wayne

 

[J2H]

The "Oops" message was not directed at you. The Forum is experiencing problems, and when it does, we get an "Oops" message.

Aha, yes I have gotten a quite few of those too in the last few days, but also realized I could have combined some of those messages.

 

[BarryO]

#4 Cu is not normally allowed to be protected at 100A. It would either need to meet one of the tap rules, or perhaps be spliced in a separate enclosure to #3 Cu that terminates on the 100A breaker, if the insulation is rated 90C.

Cheers, Wayne

Oops, missed that part; the way I read it I thought the concern was the maximum compressor fusing. Yes need to go to #3, assuming 75C terminals.

 

[Eddie702]

This is a common problem in the HVAC roof top world and I used to do a lot of RTU replacements. My boss held the Masters license but can't change a light bulb. I had a Master's as well.

When quoting a RTU replacement they never looked at wire size breaker size etc. To them a 20 ton unit is a 20 ton unit. WRONG.

The older units especially the larger equipment was often semi-hermetic compressors---looked sort of like a car engine for those that havent seen one.

It would have been common for a 20 ton unit to have 2 10 ton compressors back in the day.

Now a 20 ton unit they all use tin can scroll compressors might have 2 7 1/2 ton and 1 5 ton compressor or even 4 5 ton compressors.


This changes the MOCP and MCA of the new unit.

The more compressors you have the smaller the MCA gets because you only take 125% of the largest compressor.

Frequently you find the conductors are the right size or oversized but the ocp is wrong. Just like in the OPs post above.

So when we did the install and I told him we had to change a breaker or reconfigure something he couldn't understand. So he would decide not to get a permit instead of spending more $$$$.

Which is why i quit that place and walked out one day. 9 years later I am still pissed!!!!!!!!!!!!

 

[J2H]

You mentioned earlier it is Iline. I-line is notn obsolete although certain breaker types that fit I line panels have been discontinued but there most likely is something else available that will work in place of the type you have. Basically need to know voltage and AIC rating needed to determine what will work. 480 or 600 volt breakers will work on 208 or 240, but 208 or 240 volt breakers can not be used on 480 or 600 volts. They all plug onto any I-line bus.

How long is the run to the disconnect? It possibly can still be compliant if it fits conditions of any feeder tap rules and you do have proper overcurrent device at the disconnect. More than 25 feet and inside the building, forget it you need proper protection on supply end.

I believe the panel uses FA type I-line breakers, which it seems may be obsolete, though it sounds like you are very familiar with Square D equipment. It's a 240 volt delta, 400 amp service. I do not see AIC markings on the existing breakers, based on the information I briefly ran in FC², it appears that 22,000 would sufficient for 150 kVA delta bank. But sounds like I would need to contact the utility to have the proper numbers.

The run is under 25 feet and mostly outdoors but not completely.

 

[J2H]

This is a common problem in the HVAC roof top world and I used to do a lot of RTU replacements. My boss held the Masters license but can't change a light bulb. I had a Master's as well.

When quoting a RTU replacement they never looked at wire size breaker size etc. To them a 20 ton unit is a 20 ton unit. WRONG.

The older units especially the larger equipment was often semi-hermetic compressors---looked sort of like a car engine for those that havent seen one.

It would have been common for a 20 ton unit to have 2 10 ton compressors back in the day.

Now a 20 ton unit they all use tin can scroll compressors might have 2 7 1/2 ton and 1 5 ton compressor or even 4 5 ton compressors.


This changes the MOCP and MCA of the new unit.

The more compressors you have the smaller the MCA gets because you only take 125% of the largest compressor.

Frequently you find the conductors are the right size or oversized but the ocp is wrong. Just like in the OPs post above.

So when we did the install and I told him we had to change a breaker or reconfigure something he couldn't understand. So he would decide not to get a permit instead of spending more $$$$.

Which is why i quit that place and walked out one day. 9 years later I am still pissed!!!!!!!!!!!!

Yep, I suspect that the HVAC contractor who installed the unit did the electrical work based on the looks of things, such as the foil tape covering the knockout where the rigid was moved, and the fact that NM-B was used on the load side of the disconnect which is mounted on the unit, with no bushing or connector.

 

[wwhitney]

The run is under 25 feet

Is the run all within a raceway rather than a cable method? If so, you can use the 25' tap rule to keep the #4 on the 100A breaker, as long as at the load end the #4 lands on a <=85A OCPD. E.g. the 70A OCPD for your new unit.

Cheers, Wayne

 

[J2H]

Is the run all within a raceway rather than a cable method? If so, you can use the 25' tap rule to keep the #4 on the 100A breaker, as long as at the load end the #4 lands on a <=85A OCPD. E.g. the 70A OCPD for your new unit.

Cheers, Wayne

Line side is entirely in a raceway and it wouldn’t be difficult to address the load side. The EGC would have to be increased since it’s only #10 but it avoids repulling everything, although that’s a possibility I considered too.

That’s quite interesting I never realized previously that the tap rules could be applied to this situation in that manner, but it is quite useful.

 

[AC\DC]

What’s the raceway?? If it’s a metal why pull repull a ground

 

[J2H]

What’s the raceway?? If it’s a metal why pull repull a ground

Raceway is a combination of EMT and Rigid with an LB in the run.
Yes the ground could be omitted. As I understand the code, if a ground is pulled it must be sized correctly, possibly because it could prevent a fault from clearing if it is undersized.

 

[AC\DC]

how??? If it’s bonded having a smaller wire ain’t doing nothing wrong-
I’d cut it off and call it a day- now it’s a spare or pull string and my raceway the egc

 

[kwired]

I believe the panel uses FA type I-line breakers, which it seems may be obsolete, though it sounds like you are very familiar with Square D equipment. It's a 240 volt delta, 400 amp service. I do not see AIC markings on the existing breakers, based on the information I briefly ran in FC², it appears that 22,000 would sufficient for 150 kVA delta bank. But sounds like I would need to contact the utility to have the proper numbers.

The run is under 25 feet and mostly outdoors but not completely.

FA breakers were rated 10kA @240 volts, QBA is the current product that is pretty similar also with 10kA rating @ 240 volts.

Since the run is under 25 feet, I also agree you can leave breaker as is and use tap rule. They are pretty proud of I line breakers. List price I see is 1913.00 you may be able to get it for as low as maybe 650 or so from a Square D distributor. They only tend to be lesser when purchased with a panel as a job order. One breaker may not save anything. three or more breakers, buy with a panel and either sell or scrap the panel, it will cost less than purchasing three breakers on three separate orders.

 

[J2H]

FA breakers were rated 10kA @240 volts, QBA is the current product that is pretty similar also with 10kA rating @ 240 volts.

Since the run is under 25 feet, I also agree you can leave breaker as is and use tap rule. They are pretty proud of I line breakers. List price I see is 1913.00 you may be able to get it for as low as maybe 650 or so from a Square D distributor. They only tend to be lesser when purchased with a panel as a job order. One breaker may not save anything. three or more breakers, buy with a panel and either sell or scrap the panel, it will cost less than purchasing three breakers on three separate orders.

Thank you for the detailed information. Looks like I can get it from a local distributor for around 1200, but most likely will use the tap rule since there is a mechanical failure on the disconnect...blades jam, and can't be closed without moving the switch mechanism manually, with the breaker open of course. Seems best replaced.

 

[J2H]

Thanks to everyone for the responses. I had not considered the possibility of applying the tap rules to this situation.

Ideally seems like the best and most standard solution is to replace the disconnect and breaker, but I have a feeling they won’t like the cost.