The use of EMT as a service mast

[randyheggem]

Where exactly in the NEC does it explicitly say you cannot use EMT as a service mast? 230.28 only speaks to being of adequate strength or be supported by braces to withstand the strain. It doesn't say specifically no EMT. I cannot find a code article listing approved wiring methods for service masts. 230.3.B is only applicable for underground service conductors. In 358.12 for EMT uses not permitted it says nothing of service masts. I know according to my internet searches EMT cannot handle the high levels of fault current which could fall under 358.12.1 but that isn't very specific and subjective due to the fact RMC cannot withstand the levels of fault current either and RMC is able to be used as a service mast. Is it written in the MN residential building code somewhere or do the manufactures of EMT state their product will not work for use as a service mast?

 

[Dennis Alwon]

The power company will also determine that emt isn't strong enough.

230.28 Service Masts as Supports. Only power service-drop or
overhead service conductors shall be permitted to be attached
to a service mast. Service masts used for the support of servicedrop
or overhead service conductors shall be installed in
accordance with 230.28(A) and (B).
(A) Strength. The service mast shall be of adequate strength
or be supported by braces or guys to withstand safely the strain
imposed by the service-drop or overhead service conductors.
Hubs intended for use with a conduit that serves as a service
mast shall be identified for use with service-entrance equipment.
(B) Attachment. Service-drop or overhead service conductors
shall not be attached to a service mast between a weatherhead
or the end of the conduit and a coupling, where the coupling
is located above the last point of securement to the building or
other structure or is located above the building or other structure.

 

[jap]

Are the service conductors actually attaching to the mast?

JAP>

 

[Little Bill]

The power company will also determine that emt isn't strong enough.

They will (at least where I am) tell you what to use for a mast, or what choices you have.

 

[roger]

Are the service conductors actually attaching to the mast?

JAP>

Many times yes and even if not it's as Bill says, the POCO conductors might and they can dictate what they want.

 

[jap]

Many times yes and even if not it's as Bill says, the POCO conductors might and they can dictate what they want.

I meant EMT may be acceptable as a service mast as long as it is not being used as a means of support for the service conductors.

JAP>

 

[infinity]

I meant EMT may be acceptable as a service mast as long as it is not being used as a means of support for the service conductors.

JAP>

What is the actual definition of a mast? Isn't it the service raceway that also supports the drop? If the drop isn't supported by the raceway is it still a mast?

 

[jap]

What is the actual definition of a mast? Isn't it the service raceway that also supports the drop? If the drop isn't supported by the raceway is it still a mast?

Not sure,,,, is a mast on a sailboat not a mast if the sails aren't raised?

JAP>

 

[jap]

The rule says that only power service-drop or over head service conductors are permitted to be attached to a "Service Mast"
Then goes on to explain how to be installed if used as a means of support.

Therefore a service mast is considered a "Mast" before anything is ever attached to it.

At least that's the way I see it.

Jap>


230.28 Service Masts as Supports. Only power service-drop or
overhead service conductors shall be permitted to be attached
to a service mast. Service masts used for the support of servicedrop
or overhead service conductors shall be installed in
accordance with 230.28(A) and (B).
(A) Strength. The service mast shall be of adequate strength
or be supported by braces or guys to withstand safely the strain
imposed by the service-drop or overhead service conductors.
Hubs intended for use with a conduit that serves as a service
mast shall be identified for use with service-entrance equipment.
(B) Attachment. Service-drop or overhead service conductors
shall not be attached to a service mast between a weatherhead
or the end of the conduit and a coupling, where the coupling
is located above the last point of securement to the building or
other structure or is located above the building or other structure.

 

[gadfly56]

The rule says that only power service-drop or over head service conductors are permitted to be attached to a "Service Mast"
Then goes on to explain how to be installed if used as a means of support.

Therefore a service mast is considered a "Mast" before anything is ever attached to it.

At least that's the way I see it.

Jap>


230.28 Service Masts as Supports. Only power service-drop or
overhead service conductors shall be permitted to be attached
to a service mast. Service masts used for the support of servicedrop
or overhead service conductors shall be installed in
accordance with 230.28(A) and (B).
(A) Strength. The service mast shall be of adequate strength
or be supported by braces or guys to withstand safely the strain
imposed by the service-drop or overhead service conductors.
Hubs intended for use with a conduit that serves as a service
mast shall be identified for use with service-entrance equipment.
(B) Attachment. Service-drop or overhead service conductors
shall not be attached to a service mast between a weatherhead
or the end of the conduit and a coupling, where the coupling
is located above the last point of securement to the building or
other structure or is located above the building or other structure.

What would a drop be supported by if it isn't supported by the mast? What other function would a mast serve?

 

[jap]

What would a drop be supported by if it isn't supported by the mast? What other function would a mast serve?

An eave of a house,,,, an anchor into a Pole,,,, anywhere where it's not actually attached to the "mast" or "riser" or whatever one wants to call it.


JAP>

 

[mtnelect]

In California, Southern California Edison only allows rigid steel or IMC conduit for risers when attaching service drops.

 

[gadfly56]

An eave of a house,,,, an anchor into a Pole,,,, anywhere where it's not actually attached to the "mast" or "riser" or whatever one wants to call it.


JAP>

This was how the service was connected on my last house. The town inspector said I had to put a mast in before closing on the sale, because that type of connection was not allowed.

 

[Dennis Alwon]

What is the actual definition of a mast? Isn't it the service raceway that also supports the drop? If the drop isn't supported by the raceway is it still a mast?

I was thinking that the nec may need a definition to clarify for some people. Imo. the mast is the raceway that rises above the rooftop- usually thru the overhang of the building - that gives the power company's a place to attach the service drop. That is why the power company determines if the conduit is strong enough. In a residence of 200 amps 2" rmc is the standard around here and I have seen it get bent to a 45 degree angle when a tree falls on the overhead lines. Obviously the higher you go above the roof the weaker the conduit and hence the need for a tie down

looking at the definition of mast in the dictionary you can see the similarities between a ship's mast and the electrical mast.

Definition of mast
The meaning of MAST is a long pole or spar rising from the keel or deck of a ship and supporting the yards, booms, and rigging.

The riser is the raceway that does not go above the roof and doesn't support the overhead conductors.

 

[Dennis Alwon]

Here is a nice graphic for longer masts. I believe this is from Washington state

 

[jap]

This was how the service was connected on my last house. The town inspector said I had to put a mast in before closing on the sale, because that type of connection was not allowed.

It's still allowed depending on your area.

JAP>

 

[jap]

I was thinking that the nec may need a definition to clarify for some people. Imo. the mast is the raceway that rises above the rooftop- usually thru the overhang of the building - that gives the power company's a place to attach the service drop. That is why the power company determines if the conduit is strong enough. In a residence of 200 amps 2" rmc is the standard around here and I have seen it get bent to a 45 degree angle when a tree falls on the overhead lines. Obviously the higher you go above the roof the weaker the conduit and hence the need for a tie down

looking at the definition of mast in the dictionary you can see the similarities between a ship's mast and the electrical mast.


The riser is the raceway that does not go above the roof and doesn't support the overhead conductors.

Yes, that's the a mast, but, it doesn't have to have service conductors "attached" to it to make it a mast.

The mast is nothing more than the upward raceway.

If you look up the definition of a service mast it will call the conduit rising up out ouf the meter base a "mast" at times even though no service conductors are attached to it.

If it does get attached to, then, it must follow the rules of strength and support.

JAP>

 

[jap]

In California, Southern California Edison only allows rigid steel or IMC conduit for risers when attaching service drops.

That's one example, and, rightfully so if they are attaching to it, but, go online and look at Midamericanenergy.com/electric-service-connection for instance.

It shows examples of service masts that are on the side of a house, and, not attached to.

In that case it the riser would not be required to support the strain of any conductors attached to them.

Oh well,,,, to each his own.

JAP>

 

[Dennis Alwon]

Yes, that's the a mast, but, it doesn't have to have service conductors "attached" to it to make it a mast.

The mast is nothing more than the upward raceway.

If you look up the definition of a service mast it will call the conduit rising up out ouf the meter base a "mast" at times even though no service conductors are attached to it.

If it does get attached to, then, it must follow the rules of strength and support.

JAP>

Where do you find the definition of a service mast in the nec.

 

[kwired]

Yes, that's the a mast, but, it doesn't have to have service conductors "attached" to it to make it a mast.

The mast is nothing more than the upward raceway.

If you look up the definition of a service mast it will call the conduit rising up out ouf the meter base a "mast" at times even though no service conductors are attached to it.

If it does get attached to, then, it must follow the rules of strength and support.

JAP>

Where is this definition. I don't see anything in art 100 or 230 which is were I would expect to find it if there was one.

Note 230.28 that has been quoted a couple times here is titled "230.28 Service Masts as Supports."

I have on occasion installed or run into masts used as support for other than service applications as well though NEC seems to only focus on "service masts".