25 FT Tap Rule

[Johnhall30]

For a service tapped from a wireway; Using the 25 ft tap rule, can a meter be installed prior to the fused service disconnect protecting the tap conductors?

240.21(B)(4)(4) AND 240.21(B)(4)(6) makes me believe that the overcurrent protection will have to be provided before the meter.



However, it looks like using the 10 ft tap rule, a meter can be installed prior to the disconnect

 

[david luchini]

For a service tapped from a wireway; Using the 25 ft tap rule, can a meter be installed prior to the fused service disconnect protecting the tap conductors?

240.21(B)(4)(4) AND 240.21(B)(4)(6) makes me believe that the overcurrent protection will have to be provided before the meter.



However, it looks like using the 10 ft tap rule, a meter can be installed prior to the disconnect

The Article 240 tap rules do not apply to Service conductors

 

[mbrooke]

Tap conductors work on the assumption there is an upstream fuse or breaker.

The wire only permitted smaller on the basis the OCPD will open before the conductor's thermal withstand is exceeded. Length restricted as to limit the amount of impedance added to the system during a fault not to delay the device's tripping time.

Service conductors are considered unfused.

 

[electrofelon]

Tap conductors work on the assumption there is an upstream fuse or breaker.

The wire only permitted smaller on the basis the OCPD will open before the conductor's thermal withstand is exceeded. Length restricted as to limit the amount of impedance added to the system during a fault not to delay the device's tripping time.

Service conductors are considered unfused.

I think a big part of the length restriction is to limit the possibility of physical damage and a fault happening in the 1st place

 

[Johnhall30]

I misworded my question. The wireway is not service conductors. There is a disconnect prior to the wireway. The question still stands if the 25 ft tap needs to terminate in a disconnect prior to the meter.

 

[bwat]

There is a disconnect prior to the wireway.

Fused?

 

[Johnhall30]

Fused?

Yes

 

[Dennis Alwon]

I believe all taps must end in a disconnect of some sort. I am going from memory

 

[bwat]

Looking through 240.21(B) real quick, I don't see any way you could hit the meter first. A lot of "must terminate on single circuit breaker or set of fuses" and no exceptions.

 

[mbrooke]

If the disconnect is

Yes

Go off that.

 

[jap]

Every group metering setup with a Main Breaker in the terminal box is exactly as his picture.

You're essentially tapping a feeder at that point prior to a meter.

Other than this scenario is stick built,,,,how is this any different?

JAP>

 

[don_resqcapt19]

While a common practice, I don't see this actually permitted by 240.21(B). The 10' rule requires the tap conductor to:

(1)
The ampacity of the tap conductors is

• a. Not less than the combined calculated loads on the circuits supplied by the tap conductors
• b. Not less than the rating of the equipment containing an overcurrent device(s) supplied by the tap conductors or not less than the rating of the overcurrent protective device at the termination of the tap conductors

The tap conductor terminates at the meter and the meter does not contain an overcurrent device.

The 25' tap rule says:

...(2) The tap conductors terminate in a single circuit breaker or a single set of fuses that limit the load to the ampacity of the tap conductors. This device shall be permitted to supply any number of additional overcurrent devices on its load side.

This requires that tap conductor land on a breaker or the terminals of a fuse holder.

 

[jap]

...(2) The tap conductors terminate in a single circuit breaker or a single set of fuses that limit the load to the ampacity of the tap conductors. This device shall be permitted to supply any number of additional overcurrent devices on its load side.


To me you have to let the rule finish it's sentence.

Yes, it has to terminate on a single circuit breaker or a single set of fuses that "limit the load to the ampacity of the tap conductors", and they do.

The meter does nothing to increase the ampacity of the tap conductors.


JAP>

 

[don_resqcapt19]

...(2) The tap conductors terminate in a single circuit breaker or a single set of fuses that limit the load to the ampacity of the tap conductors. This device shall be permitted to supply any number of additional overcurrent devices on its load side.


To me you have to let the rule finish it's sentence.

Yes, it has to terminate on a single circuit breaker or a single set of fuses that "limit the load to the ampacity of the tap conductors", and they do.

The meter does nothing to increase the ampacity of the tap conductors.


JAP>

The rating of the OCDP does not even enter into this because the conductors landed on the line side of the meter can are not terminated in a single circuit breaker or single set of fuses. The 25' tap rule requires a direct connection to the OCPD and does not permit the meter to be before the OCDP.

 

[electrofelon]

The rating of the OCDP does not even enter into this because the conductors landed on the line side of the meter can are not terminated in a single circuit breaker or single set of fuses. The 25' tap rule requires a direct connection to the OCPD and does not permit the meter to be before the OCDP.

It depends on exactly what "terminate" means. My opinion is that "terminate" does not necessarily mean anything and everything that isn't the same continuous conductor. For example Some will say that you cannot splice a tap because it terminates on the connector you are using. I don't really see the wording of the tap rules prohibiting the installation questioned.

 

[don_resqcapt19]

It depends on exactly what "terminate" means. My opinion is that "terminate" does not necessarily mean anything and everything that isn't the same continuous conductor. For example Some will say that you cannot splice a tap because it terminates on the connector you are using. I don't really see the wording of the tap rules prohibiting the installation questioned.

The wire conductor physically ends where it lands on on the terminal in the meter can and is terminated at the terminal in the meter can, and I see that as a violation of the actual code language.

 

[jap]

The rating of the OCDP does not even enter into this because the conductors landed on the line side of the meter can are not terminated in a single circuit breaker or single set of fuses. The 25' tap rule requires a direct connection to the OCPD and does not permit the meter to be before the OCDP.

And why not?

A utility meter is not a load, nor does it require overload or short circuit protection.

There's nothing in the rule that indicates the tap conductor has to land on a single breaker or a single set of fuses "first",,, only that it has to land on them to protect the tap conductor.

JAP>

 

[jap]

It depends on exactly what "terminate" means. My opinion is that "terminate" does not necessarily mean anything and everything that isn't the same continuous conductor. For example Some will say that you cannot splice a tap because it terminates on the connector you are using. I don't really see the wording of the tap rules prohibiting the installation questioned.

I'd have to agree.

If the tap conductor you were using wasn't long enough to reach the overload protection, would simply splicing it with the same size wire to make it reach be a code violation?

If so why?

What in the splice reduces the current carrying capacity of the conductor?

We splice feeders every day that do nothing to derate their current carrying capacity.

JAP>

 

[mbrooke]

I'd have to agree.

If the tap conductor you were using wasn't long enough to reach the overload protection, would simply splicing it with the same size wire to make it reach be a code violation?

If so why?

What in the splice reduces the current carrying capacity of the conductor?

We splice feeders every day that do nothing to derate their current carrying capacity.

JAP>

We don't know the resistance or I2R withstand of the meter socket, busbar, ect.

 

[electrofelon]

We don't know the resistance or I2R withstand of the meter socket, busbar, ect.

Meter sockets have a rather high SCCR. But true SCCR should always be checked. Not sure what the resistance has to do with it.