Grounding a transformer with lightnening protection

Status
Not open for further replies.
M

mannyb

Senior Member
Location
Florida
Occupation
Electrician
we are installing some equipement for communication equipment and it requires grounding. The room is on 3rd floor with no building steel. There is
XFMR in the room, on 3rd floor, has a 3/4'' conduit with #6 for ground rod running to 1st floor. is there a reason, by Code, i couldnt run a #2 to a ground bus bar
and use that for XFMR grounding or cellulr equipment.
 
You are out of luck.

There are allowances to do what you suggest but the conductor running to the main service GEC must be at least 3/0.
 
iwire said:
You are out of luck.

There are allowances to do what you suggest but the conductor running to the main service GEC must be at least 3/0.
Click to expand...

i did consider that. the guys say the 3/0 looks to hard to pull in 3/4'' conduit. Could i run a bare 3/0 along the surface and protected in area where subject to
physical damage?
 
don_resqcapt19 said:
What exactly requires the equipment to be grounded? What is the equipment?
Click to expand...

the equipment is telecommunication equipment. The equipment tie to a master ground bar for lightning protection. my thoughts were....could i run a 3/0 from 1st to 3rd with 3/0 and also ground my transfotmer off same MGB??
 
mannyb said:
the equipment is telecommunication equipment. The equipment tie to a master ground bar for lightning protection. my thoughts were....could i run a 3/0 from 1st to 3rd with 3/0 and also ground my transfotmer off same MGB??
Click to expand...

You have not been very clear.

Am I understanding correctly that you have two different items to ground?

A power transformer and telco equipment?
 
mannyb said:
we are installing some equipement for communication equipment and it requires grounding. The room is on 3rd floor with no building steel. There is
XFMR in the room, on 3rd floor, has a 3/4'' conduit with #6 for ground rod running to 1st floor. is there a reason, by Code, i couldnt run a #2 to a ground bus bar
and use that for XFMR grounding or cellulr equipment.
Click to expand...

The requirements in the code are what they are. The size of the GEC for the transformer is dependent on the transformer rating. No reason you can't snake it along the existing conduit down to the existing GES.

Unless I am grossly mistaken, there is no code violation in bonding equipment to an existing GEC, you just can't use it as a common GEC. where a GEC connection is required.
 
petersonra said:
The requirements in the code are what they are. The size of the GEC for the transformer is dependent on the transformer rating. No reason you can't snake it along the existing conduit down to the existing GES.

Unless I am grossly mistaken, there is no code violation in bonding equipment to an existing GEC, you just can't use it as a common GEC. where a GEC connection is required.
Click to expand...

If he is trying to use the GEC of one existing transformer for a new transformer GEC 250.30(A)(6) comes into play.

Here is part of it.

(a) Common Grounding Electrode Conductor. The
common grounding electrode conductor shall be permitted
to be one of the following:

(1) A conductor of the wire type not smaller than 3/0 AWG
copper or 250 kcmil aluminum

(2) The metal frame of the building or structure that complies
with 250.52(A)(2) or is connected to the grounding
electrode system by a conductor that shall not be
smaller than 3/0 AWG copper or 250 kcmil aluminum

(b) Tap Conductor Size. Each tap conductor shall be
sized in accordance with 250.66 based on the derived ungrounded
conductors of the separately derived system it
serves.

Exception: If a separately derived system originates in
listed equipment suitable as service equipment, the grounding
electrode conductor from the service or feeder equipment
to the grounding electrode shall be permitted as the
grounding electrode conductor for the separately derived
system, provided the grounding electrode conductor is of
suffıcient size for the separately derived system. If the
equipment ground bus internal to the equipment is not
smaller than the required grounding electrode conductor
for the separately derived system, the grounding electrode
connection for the separately derived system shall be permitted
to be made to the bus.
Click to expand...
 
iwire said:
If he is trying to use the GEC of one existing transformer for a new transformer GEC 250.30(A)(6) comes into play.

Here is part of it.
Click to expand...
Not too sure about that... it's only for multiple SDS's. Unless I'm mistaken, only one existing xfmr involved.
 
Smart $ said:
Not too sure about that... it's only for multiple SDS's. Unless I'm mistaken, only one existing xfmr involved.
Click to expand...

I am unsure of what he has but my thinking is he has an existing transformer, he is adding a transformer and he has telco equipment to ground and he wants to use the existing transformers GEC to handle it.

BUT .... I really don't know.
 
iwire said:
I am unsure of what he has but my thinking is he has an existing transformer, he is adding a transformer and he has telco equipment to ground and he wants to use the existing transformers GEC to handle it.

BUT .... I really don't know.
Click to expand...
Your point will be correct if there will be two transformers when all is said and done.

I am interpreting his posts as one transformer total.
 
mannyb said:
we are installing some equipement for communication equipment and it requires grounding. The room is on 3rd floor with no building steel. There is
XFMR in the room, on 3rd floor, has a 3/4'' conduit with #6 for ground rod running to 1st floor. is there a reason, by Code, i couldnt run a #2 to a ground bus bar
and use that for XFMR grounding or cellulr equipment.
Click to expand...


More speculation, but sounds to me like:

1) has existing #6 GEC for SDS
2) adding some communication equip and it requires grounding because the EGC serving the equipment isn't "good enough" and "better" grounding solves all problems ;)
3) wants to use the GEC as the ground for the comm equip

why use a #2 if its tapping onto a #6? I don't see why you couldn't lay in lug onto that GEC if it makes you or someone feel better or meets the specs for the job.
 
Smart $ said:
Your point will be correct if there will be two transformers when all is said and done.

I am interpreting his posts as one transformer total.
Click to expand...



there is 1 existing transformer on 3rd floor. the transformer has a 3/4'' conduit with a single GEC #6 inside. we are installing new telecommunication equipment inside the same room as transformer. we would like to use 3/4' conduit going to transformer and tap off ground for Lightning protection. i was wanting to get
opinions, code implied, Can i share the lightning protection and GEC for transformer on same GEC? i want to use existing 3/4'' conduit for raceway. What options could be available it any?
 
mannyb said:
there is 1 existing transformer on 3rd floor. the transformer has a 3/4'' conduit with a single GEC #6 inside. we are installing new telecommunication equipment inside the same room as transformer. we would like to use 3/4' conduit going to transformer and tap off ground for Lightning protection. i was wanting to get
opinions, code implied, Can i share the lightning protection and GEC for transformer on same GEC? i want to use existing 3/4'' conduit for raceway. What options could be available it any?
Click to expand...
See 800.100
 
Status
Not open for further replies.
Top