Why more than 6 disconnects need MAIN!!

[Cletis]

Just curious how and when someone decided you needed a main with more than 6 disconnects ??? I'm guessing this was back in the 1930's if I had to take a stab. Did they roll dice, flip straws to get that number?? why 6 not 5,3,4,7,9 I can't grasp why they picked 6 and I'm starting to lose sleep over it I take ambien some nights it bothers me so much. Please help

 

[Dennis Alwon]

You'll never change will you Cletis.... Remember in the 2020 you cannot use the 6 disconnect rule if you have only one panel. There has to be a main.

To answer your question the same person that decided 25 ohms for a ground rod decided 6 disconnect was just enough to quickly shut down a building. If 7 were used then the entire building would burn down because the firemen could shut the power off quickly enough. :lol:

 

[electrofelon]

If 7 were used then the entire building would burn down because the firemen could shut the power off quickly enough. :lol:

Or, if seven were used, cletis would be loosing sleep and taking ambian over wondering why they didn't pick 6. hmy:

 

[Cletis]

Well, I just happen to be setting up a 6 unit (meter) apt building is what made me think of this. Prob gonna have to do 2-3gang meter packs since eaton is backlogged 27weeks around here to get a 6gang meter pack and the owner is a cheapo so ....hence the question

 

[Jraef]

Waaaaay back when I was learning this trade in the 70s, I took a code class and this subject came up (where the 6 hand motion rule came from). As I recall, the teacher said it came along after a particularly bad fire in the 20s where firefighters were injured by live electrical circuits while fighting the fire, because there were multiple sources of energy coming into the building and they didn’t know of all of them. So that became the nexus of Service Entrance Equipment rules and at the same time they tested how many switches a firefighter, holding his axe in one hand, could operate in 5 seconds standing in one spot at the service entrance. 6 was the number they decided on.

Back in in those days we didn’t question what teachers told us. I tried Googling for some corroboration of this but there was too much garbage to filter though. It would be interesting to find out if that was right.

 

[mbrooke]

Never question the source of information, it is always right.

 

[oldsparky52]

Remember in the 2020 you cannot use the 6 disconnect rule if you have only one panel. There has to be a main.

I did not know that, ... thanks.

 

[Little Bill]

Waaaaay back when I was learning this trade in the 70s, I took a code class and this subject came up (where the 6 hand motion rule came from). As I recall, the teacher said it came along after a particularly bad fire in the 20s where firefighters were injured by live electrical circuits while fighting the fire, because there were multiple sources of energy coming into the building and they didn’t know of all of them. So that became the nexus of Service Entrance Equipment rules and at the same time they tested how many switches a firefighter, holding his axe in one hand, could operate in 5 seconds standing in one spot at the service entrance. 6 was the number they decided on.

Back in in those days we didn’t question what teachers told us. I tried Googling for some corroboration of this but there was too much garbage to filter though. It would be interesting to find out if that was right.

They must have been handles on a fused disconnect as I don't think breakers were around the the 20's.

 

[synchro]

They must have been handles on a fused disconnect as I don't think breakers were around the the 20's.

Or pull-out disconnects, often with cartridge fuses in them.

 

[DBoone]

You'll never change will you Cletis.... Remember in the 2020 you cannot use the 6 disconnect rule if you have only one panel. There has to be a main.

To answer your question the same person that decided 25 ohms for a ground rod decided 6 disconnect was just enough to quickly shut down a building. If 7 were used then the entire building would burn down because the firemen could shut the power off quickly enough. :lol:

Cletis ? ..... he is entertaining

 

[romex jockey]

Waaaaay back when I was learning this trade in the 70s, I took a code class and this subject came up (where the 6 hand motion rule came from). As I recall, the teacher said it came along after a particularly bad fire in the 20s where firefighters were injured by live electrical circuits while fighting the fire, because there were multiple sources of energy coming into the building and they didn’t know of all of them. So that became the nexus of Service Entrance Equipment rules and at the same time they tested how many switches a firefighter, holding his axe in one hand, could operate in 5 seconds standing in one spot at the service entrance. 6 was the number they decided on.

Back in in those days we didn’t question what teachers told us. I tried Googling for some corroboration of this but there was too much garbage to filter though. It would be interesting to find out if that was right.

I was privy to the same story , & told it was the Waldorf Astoria fire....

~RJ~

 

[jtinge]

Just curious how and when someone decided you needed a main with more than 6 disconnects ??? I'm guessing this was back in the 1930's if I had to take a stab. Did they roll dice, flip straws to get that number?? why 6 not 5,3,4,7,9 I can't grasp why they picked 6 and I'm starting to lose sleep over it I take ambien some nights it bothers me so much. Please help

I believe it was the same rationale that was used to determine that a maximum of 3.4 oz of liquid was safe to carry on a plane.

https://www.youtube.com/watch?v=IHfiMoJUDVQ

 

[Jraef]

Found an interesting post in an Inspector's forum related to this issue, indicating that the rule apparently goes back to 1931:

In the 1931 NEC the requirement was one switch (disconnect) for each set of service conductors, with an exception for single-family dwellings which were allowed to omit that switch if there were no more than 6 branch circuits (there is the first appearance of the maximum of 6 disconnects per service).

Prior to that (my 1928 and earlier editions), the references all state that each set of service conductors have "a switch", "the switch", etc., all with the singular references of "a" or "the" in reference to the singular reference "switch", not the plural reference switch"es".

Thus, only one was allowed until 1931, then for single-family with not more than 6 branch circuits was allowed to eliminate that one, leaving six.

No mention as to why they settled on 6 as the limit though. As Little Bill said, they would not have been circuit breakers in the 1920s so if I had to guess, I'd lay odds that at that time, 6 circuits may have been the limit to a (then 30A) residential knife switch style service panel; 3 on one side, 3 on the other. I had a house in Seattle that was built in 1910, the old original service panel was embedded into the outside wall, so it was abandoned and left there when the service was upgraded (probably) in the 70s. It had a main knife switch, but then just 4 poles of branch switches, probably going to a fuse box in the basement (it wasn't there, I guessed that was replaced with the breaker panel).