Central Air Feed Under Main Breaker???

[Jimmyboy]

I recently took on a 150 lot mobile home park, as an account. In November, a mobile home burned to the ground, because the Central A/C line was under the 100 amp main breaker (in the mobile home), and not on a DP 30. The line became damaged and could not trip the DP 100, so it just melted and caused fire. The park owner is now mandating that ALL tenants have their panels inspected (by me), to make sure that this is not the case in other homes. I have found 4 other homes that the A/C line is feed from the lugs on the main breaker, before it goes to the A/C disconnect outdoors. Is this code compliant, and where can I find it in the code book? I know there is a "tap on" rule, but not sure if applies to this scenario. It is my belief that there shall be ONE conductor under each lug, NOT a #2 and #10. PLEASE help me clarify this. Thanks in advance!

 

[kwired]

I recently took on a 150 lot mobile home park, as an account. In November, a mobile home burned to the ground, because the Central A/C line was under the 100 amp main breaker (in the mobile home), and not on a DP 30. The line became damaged and could not trip the DP 100, so it just melted and caused fire. The park owner is now mandating that ALL tenants have their panels inspected (by me), to make sure that this is not the case in other homes. I have found 4 other homes that the A/C line is feed from the lugs on the main breaker, before it goes to the A/C disconnect outdoors. Is this code compliant, and where can I find it in the code book? I know there is a "tap on" rule, but not sure if applies to this scenario. It is my belief that there shall be ONE conductor under each lug, NOT a #2 and #10. PLEASE help me clarify this. Thanks in advance!

A tap could possibly be made, it would have to follow requirements in 240.21(B). But such taps can not be made with two conductors in a lug only designed for one conductor. I would have to dig a little deeper, but I think this tap would have to be the load side of main breaker and not line side. Since this main is in a mobile home it is not going to the service disconnect - that may possibly throw my thinking off a little as we would be taping a feeder and not service conductors in this case.

After checking 550.11(A) requires a single disconnecting means, so the tap would have to be load side of main.

 

[GoldDigger]

I recently took on a 150 lot mobile home park, as an account. In November, a mobile home burned to the ground, because the Central A/C line was under the 100 amp main breaker (in the mobile home), and not on a DP 30. The line became damaged and could not trip the DP 100, so it just melted and caused fire. The park owner is now mandating that ALL tenants have their panels inspected (by me), to make sure that this is not the case in other homes. I have found 4 other homes that the A/C line is feed from the lugs on the main breaker, before it goes to the A/C disconnect outdoors. Is this code compliant, and where can I find it in the code book? I know there is a "tap on" rule, but not sure if applies to this scenario. It is my belief that there shall be ONE conductor under each lug, NOT a #2 and #10. PLEASE help me clarify this. Thanks in advance!

You have identified at least two problems correctly.
1. Very good chance the breaker lugs do not allow two wires, especially mismatched sizes. Bad practice anyway for a branch circuit.
2. A feeder tap could be run from a compliant connection to the supply side of the panel to an OCPD located elsewhere or from a feeder leaving the panel through a breaker. But it would definitely have to be protected for the wire size (not the AC FLA) at that OCPD. 240.21(B) 2011 This is a fused A/C disco, right? Next, the wire could not be rated for less than 1/3 of the 100 amp protection, or 33Amps. However, since they were connected on the supply side of the main breaker, that assumes that there was a 100A OCPD farther upstream. If not, the tap conductors would have to be sized to whatever OCPD there was, even if it is just the service protection. And in any case, that would not necessarily eliminate the fire scenario which you ran into, depending on some details we do not know yet.
3. Possibly a problem, depending on just how the wire was run:

The tap conductors are protected from physical damage by being enclosed in an approved raceway or by other approved means.

 

[kwired]

You have identified at least two problems correctly.
1. Very good chance the breaker lugs do not allow two wires, especially mismatched sizes. Bad practice anyway for a branch circuit.
2. A feeder tap could be run from a compliant connection to the supply side of the panel to an OCPD located elsewhere or from a feeder leaving the panel through a breaker. But it would definitely have to be protected for the wire size (not the AC FLA) at that OCPD. 240.21(B) 2011 This is a fused A/C disco, right? Next, the wire could not be rated for less than 1/3 of the 100 amp protection, or 33Amps. However, since they were connected on the supply side of the main breaker, that assumes that there was a 100A OCPD farther upstream. If not, the tap conductors would have to be sized to whatever OCPD there was, even if it is just the service protection. And in any case, that would not necessarily eliminate the fire scenario which you ran into, depending on some details we do not know yet.
3. Possibly a problem, depending on just how the wire was run:

Tap on supply side of the main breaker would not be allowed by 550.11(A) as I mentioned in earlier post.

 

[Jimmyboy]

Wow... Thanks guys. This helps tremendously. The typical scenario that I am running across is... Outside the mobile homes is a meter and 100 Amp Breaker/Disconnect. The homes are than fed with 4 conductors to the (now 100 amp sub panel) inside the homes. Due to lack of spaces, (usually only 12 circuit Federal Pacific panels)... the 10-3 UF was installed directly under the main breaker lugs along with the #2's. It is than ran (without physical protection) under the mobile homes to the (sometimes) fused A/C disconnects. Now you have 20-30 feet of #10 AWG wire (un)protected by a 100 amp breaker. I was almost 100% sure this was NOT code compliant.

 

[Jimmyboy]

I can't find in 550.11(A) anything about Line Side Conductors. It only speaks about Amperage and Supply Cords. Can you clarify what I am doing wrong? :rant:

 

[GoldDigger]

I can't find in 550.11(A) anything about Line Side Conductors. It only speaks about Amperage and Supply Cords. Can you clarify what I am doing wrong? :rant:

Have you tried looking in the 2011 code?

550.11 Disconnecting Means and Branch-Circuit Protective Equipment.

What version are you on?
(A) basically says that the inside panel in the mobile home must have exactly one disconnect that de-energizes everything. If the A/C is tapped to the supply side of the main breaker, then opening the main will not disconnect the A/C.

 

[jumper]

I can't find in 550.11(A) anything about Line Side Conductors. It only speaks about Amperage and Supply Cords. Can you clarify what I am doing wrong? :rant:

It sounds like you are looking at 550.10 and not 550.11.

 

[augie47]

Are there any breaker spaces available it the 100 amp service disconnect outside ?

 

[kwired]

Are there any breaker spaces available it the 100 amp service disconnect outside ?

There is a good idea. Even if no spaces you can tap the feeder. As long as this tapped circuit doesn't enter the home (which it shouldn't need to for an outdoor AC condenser unit) then you will not create additional disconnecting means in the home. Also there is unlimited length for outdoor feeder taps. The disconnect at the unit will need to have overcurrent protection of course.

 

[templdl]

After a quick review of the previous posts I see that there were references to a disconnect but there were no references made to a "fused disconnect" which would make a tape rule a possibility.

 

[acrwc10]

I recently took on a 150 lot mobile home park, as an account. In November, a mobile home burned to the ground, because the Central A/C line was under the 100 amp main breaker (in the mobile home), and not on a DP 30. The line became damaged and could not trip the DP 100, so it just melted and caused fire. The park owner is now mandating that ALL tenants have their panels inspected (by me), to make sure that this is not the case in other homes. I have found 4 other homes that the A/C line is feed from the lugs on the main breaker, before it goes to the A/C disconnect outdoors. Is this code compliant, and where can I find it in the code book? I know there is a "tap on" rule, but not sure if applies to this scenario. It is my belief that there shall be ONE conductor under each lug, NOT a #2 and #10. PLEASE help me clarify this. Thanks in advance!

There is no lug on the market that I have seen in 30+ years that allows a #2 & #10 under the same lug, good call. You should take a picture of the whole panel and post it, we will help you see a problem that may exist.

 

[Jimmyboy]

Thanks for all the help. I am still confused on one issue, and that's the tapping, on the external disconnect. If I understand correctly, you are saying even if there are no spaces in the exterior disconnect, it is compliant to feed the A/C unit from the line side of THAT service disconnect? (Which in most cases is just another DP100 Breaker.) Can you tell me where to locate that scenario in the Code book. Thanks again for ALL the help. It is greatly appreciated.

 

[Jimmyboy]

My apologies... I should have said, these scenarios involve a fused disconnect (DP 100) on the exterior. I still cant see it being possible to install the 10's with the 2's under the line side of the breaker...even on the exterior panel/disconnect. That would basically be right after the meter...with no protection at all.

 

[kwired]

Some quick mobile home basics.

First service equipment can not be located in or on the mobile home. That is your typical 100 amp breaker at/near the meter. Any service (not limited to mobile home services) can consist of up to 6 disconnecting means grouped in one location, so a tap ahead of a service disconnect may be possible but it must feed another service disconnect grouped in same location.

Second, the mobile home must be supplied by a feeder from the service, and according to 550.11(A) can only have one disconnecting means. So this means a tap inside the home on the supply side of the feeder would make there be more than one disconnecting means on the mobile home - violation there.

External air conditioning unit or other mobile home accessory buildings or structures can be supplied from the service or other site supply equipment in the case where the service is not at the mobile home site.

 

[Little Bill]

Funny timing on this thread, I just replaced one a few weeks ago with the same scenerio...A/C under the same lugs as the load on the main breaker to mobile home.

This may or may not be like the OP's, but thought it might help to see pictures of what he is describing.
You can see in the bottom of the enclosure where someone gave the 4/0 conductors a "hair cut" to get them in the lugs. Likely greatly added to the cause of the failure here.
HO called POCO with power flickering. They immediately pulled the meter and cut the drop.
Told the HO they wouldn't reconnect until this mess was fixed.

 

[kwired]

Something tells me the improper two conductors on the load side lugs had nothing to do with the failure of the line side lugs.

I see the main bonding jumper "floating" in those images also.

 

[Little Bill]

Something tells me the improper two conductors on the load side lugs had nothing to do with the failure of the line side lugs.

I see the main bonding jumper "floating" in those images also.

I said greatly added to the failure of the entire thing. I didn't take pics of anything after I demoed it but there was definitely heat damage on the load side conductors. I had to trim them back to get good conductors to re-terminate.

 

[acrwc10]

That's a thing of beauty!!!!!! You don't get to see work like that everyday. Maybe every other day.

 

[Little Bill]

That's a thing of beauty!!!!!! You don't get to see work like that everyday. Maybe every other day.

I only got to see "the beauty" in good light for a few minutes as it was almost dark when I got started on it.:lol:

It was one of them fun Saturday night jobs that just can't wait until Monday!:happysad: