hot tap rules

[jbwhite]

This is a three phase 208 volt feeder from a 225 amp breaker to an old disconnect for a HVAC split system. The old disconnect is fused down to 200 amps and feeds the condensing unit. A 20 amp circuit was run from the CU to the fan coil illegally hot tapped the distance is 30 to 40 feet. No fuses in the CU.

We need to remove the switch and feed new CU and FCU.

New CU is max fuse 60 amps, new FCU is max fuse 20 amps.

I propose removing the old switch, and installing a troff then installing two fused disconnects under the troff. One will be 60 amps the other a 30 amp with 20 amp fuses.

I want to install tap blocks in the troff and run #6 to feed each new switch then run #6 to the CU and #12 to the FCU.

Did I break any hot tap rules?

 

[websparky]

Re: hot tap rules

It looks like 240.21(B)(1) would apply in this case (if I'm understanding correctly) as long as you use 4AWG to feed the 60A disco because the lugs are rated at only 60 degrees.

 

[infinity]

Re: hot tap rules

Originally posted by websparky:
It looks like 240.21(B)(1) would apply in this case (if I'm understanding correctly) as long as you use 4AWG to feed the 60A disco because the lugs are rated at only 60 degrees.

Why would the lugs only be rated for 60 degrees?

 

[jbwhite]

Re: hot tap rules

lugs and breaker are rated 90 c. i checked.

 

[jim dungar]

Re: hot tap rules

If the feeder is 60A and is run to the line side of each disconnect, there is no need to even look at a tap rule. Tap rules are only for when a reduced size conductor is directly connected to a larger conductor without an overcurrent protective device.

But, if the feeder was 60A to the first disconnect and then a #12 was used to feed the second disconnect a tap rule could be employed correctly.

Check your devices for the proper conductor rating of either 60 or 75C. I find it hard to believe any new equipment is not rated 75C, but you still need to confirm it.

 

[jim dungar]

Re: hot tap rules

There are no UL Listed breakers with terminations rated for 90C. Yes, the lugs themselves are rated that high but the entire assembly is not. Even 100% rated devices, which require 90C conductors, are still only rated for the 75C ampacity.

 

[websparky]

Re: hot tap rules

I think 110.14 has the lug ratings. Check it out and let me know if I am wrong!

 

[jbwhite]

Re: hot tap rules

Originally posted by jim dungar:
There are no UL Listed breakers with terminations rated for 90C. Yes, the lugs themselves are rated that high but the entire assembly is not. Even 100% rated devices, which require 90C conductors, are still only rated for the 75C ampacity.

The feeder is 225 amp, that is the only leg connected to a breaker. All the other leges are connected to a tap block or disconnect switch. I will look more closely at the main breaker tomorrow when I open the panel. I need to check to see if the origianal installers put the ground wire on the neutral buss. It is taped white at the 200 amp switch.

[ January 08, 2006, 07:07 AM: Message edited by: jbwhite ]

 

[iwire]

Re: hot tap rules

Originally posted by websparky:
I think 110.14 has the lug ratings. Check it out and let me know if I am wrong!

110.14(C) Temperature Limitations. The temperature rating associated with the ampacity of a conductor shall be selected and coordinated so as not to exceed the lowest temperature rating of any connected termination, conductor, or device. Conductors with temperature ratings higher than specified for terminations shall be permitted to be used for ampacity adjustment, correction, or both.

(1) Equipment Provisions. The determination of termination provisions of equipment shall be based on 110.14(C)(1)(a) or (C)(1)(b). Unless the equipment is listed and marked otherwise, conductor ampacities used in determining equipment termination provisions shall be based on Table 310.16 as appropriately modified by 310.15(B)(1) through (6).

 

[infinity]

Re: hot tap rules

Originally posted by websparky:
I think 110.14 has the lug ratings. Check it out and let me know if I am wrong!

As iwire pointed out you may be wrong. All of the equipment that I've seen lately comes rated for 75 degrees so the provisions of 110.14(C)(1)(a)(3) would apply. This would allow the conductors to be sized at 75 degrees. Assuming that the lugs are automatically rated for 60 degrees based on 110.14(C)(1)(a)(1)is a poor assumption.

 

[jbwhite]

Re: hot tap rules

Originally posted by jbwhite:
lugs and breaker are rated 90 c. i checked.

I didnt check good enough. I was there today.
disconnect switches are rated 75 c and I dont know about the condensing unit.

So what I have is this: I sure hope I can explain it well.

3/0 from an existing sq d I line panel on a 225 amp breaker. To feed tap blocks in a troff.

First tap to feed a condensing unit rated min ckt amps 52.6. #6 from tap block to fused disconnect, #6 from disconnect to unit.

Second tap to feed AHU. min ckt amps 15.7 #6 from tap block to fused disconnect. #12 from disconnect to unit.

It looks like the original 225 amp breaker is illegal as the sq d web site says that the I line breakers are rated 75c.

Is the #12 and the 20 amp fuses in the 30 amp switch illegal, as they are less than 10 percent of the 225 amp original feeder?

 

[websparky]

Re: hot tap rules

Here is the rest of the article. I guess no one wants to read the entire text. Iwire only quoted the first part and no one cracked their code book to see if I was right or if Iwire was. You have to read things for yourself and make your own decissions.

(a) Termination provisions of equipment for circuits
rated 100 amperes or less, or marked for 14 AWG through
1 AWG conductors, shall be used only for one of the following:
(1) Conductors rated 60?C (140?F).
(2) Conductors with higher temperature ratings, provided the
ampacity of such conductors is determined based on the
60?C (140?F) ampacity of the conductor size used.
(3) Conductors with higher temperature ratings if the equipment
is listed and identified for use with such conductors.
(4) For motors marked with design letters B, C, or D, conductors
having an insulation rating of 75?C (167?F) or
higher shall be permitted to be used, provided the ampacity
of such conductors does not exceed the 75?C
(167?F) ampacity.
(b) Termination provisions of equipment for circuits
rated over 100 amperes, or marked for conductors larger
than 1 AWG, shall be used only for one of the following:
(1) Conductors rated 75?C (167?F)
(2) Conductors with higher temperature ratings, provided
the ampacity of such conductors does not exceed the
75?C (167?F) ampacity of the conductor size used, or
up to their ampacity if the equipment is listed and identified
for use with such conductors

[ January 08, 2006, 11:16 AM: Message edited by: websparky ]

 

[jbwhite]

Re: hot tap rules

sparky. #6 is good to 55 amps at 60c. unit is rated 52.6. next common size fuse is 60 amps.

do I have a problem with this part?

 

[websparky]

Re: hot tap rules

I want to install tap blocks in the troff and run #6 to feed each new switch then run #6 to the CU and #12 to the FCU.

"each new switch" terminals would be rated at 60 degrees. This is what limits the ampacity of the conductor.

The logic I guess I don't agree with is the "I want to do this the absolute cheepest way possible as long as I think it is code compliant." When in doubt, why not try to learn from others with an open mind rather than trying to find others that will support your logic? Since when is it "not cool" to perform electrical work that goes slightly above code minimum? How many more $'s would it be to install 4AWG and be sure you were code compliant?

 

[websparky]

Re: hot tap rules

Yes. The code says

(1) The ampacity of the tap conductors is
a. Not less than the combined calculated loads on the
circuits supplied by the tap conductors, and
b. Not less than the rating of the device supplied by
the tap conductors or not less than the rating of the
overcurrent-protective device at the termination of
the tap conductors.

[/quote]

 

[websparky]

Re: hot tap rules

Originally posted by websparky:
[QB] Yes. The code says

(1) The ampacity of the tap conductors is
a. Not less than the combined calculated loads on the
circuits supplied by the tap conductors, and
b. Not less than the rating of the device supplied by
the tap conductors or not less than the rating of the
overcurrent-protective device at the termination of
the tap conductors.

 

[roger]

Re: hot tap rules

Dave, no one is debating what the article section says per your quote, the key is what Iwire quoted which is part of the article.

Unless the equipment is listed and marked otherwise

I don't see where there is a debate at all.

I will ask you if you know of any major manufactures modern safety switches that are listed strictly at 60 deg?

Roger

[ January 08, 2006, 11:31 AM: Message edited by: roger ]

 

[infinity]

Re: hot tap rules

Here is the rest of the article. I guess no one wants to read the entire text. Iwire only quoted the first part and no one cracked their code book to see if I was right or if Iwire was. You have to read things for yourself and make your own decissions.

Actually Dave I did read the article that you've posted but I guess that you didn't.

(3) Conductors with higher temperature ratings if the equipment
is listed and identified for use with such conductors.

If you read #(3) from your post you would see that if the equipment is rated for 75 degrees than you can size your conductors for 75 degrees, not 60.

Iwire was correct in his first post.

 

[jbwhite]

Re: hot tap rules

Originally posted by websparky:

The logic I guess I don't agree with is the "I want to do this the absolute cheepest way possible as long as I think it is code compliant.

Them is fighting words. I am trying to find out the rules. Maybe learn.

 

[websparky]

Re: hot tap rules

I will ask you if you know of any major manufactures modern safety switches that are listed strictly at 60 deg?

Roger,
Yes, unfortunately I do. There are several of the now popular plastic enclosure types of disconnects I have seen on residential AC units. I too wish they all used the 75 lugs. It would make my job easier and make for safer installs.