Transformer Question

[Ken In NJ]

Is the statement below in Red a fact ?

We did a new service and transformer installation for a small restaurant. Power company could not give us the required 200 Amp 120/208 power that was needed in a timely manner. Only 227/480 was available.

We installed a 200 amp 600 volt meter socket (provided by the power company) below the meter socket a 100 amp 600 volt locking fused switch, then into the basement with # 2 THHN feeders to the 75 KVA transformer.

Out of the transformer and directly up to the first floor (About 10' - 14') to a 200 amp main breaker panel.

Job is done, but the prints had to be re done to show the higher voltage and transformer.

The engineer sent the prints out showing a load side 200 amp disconnect on the transformer. When we questioned it .. the notes in Red are their answer Via E-mail

NEC REQUIRES secondary disconnect for conductor protection on the load
side of the transformer with-in 10' and in line of site of the transformer.
Breaker in the panel CAN NOT serve as the disconnect.

Maybe we are missing something .. but we thought a line side disconnect would be required .. not one on the load side

Any help would be appreciated .. to add a 200 amp switch to the load side now would be a nightmare

 

[raider1]

There is no NEC requirement for a disconnect on the secondary side of a tranformer to be within sight of the tranformer.

You must provided secondary overcurrent protection of the secondary conductors in accordance with one of the rules in 240.24(C) but that overcurrent device does not have to be within sight of the transformer.

Chris

 

[david luchini]

That statement is not true IF the installation complies with 240.21(C)(6).

Then the secondary conductors are permitted to be not over 25' long.

And as Chris noted, there is no requirement for the disconnect to be in
sight of the transformer.

 

[billyzee]

taps is played at funerals

taps is played at funerals

Article 240.21 lists where overcurrent protection is required in a circuit.

Article 240.21(B) addresses where overcurrent protection is required on feeder taps. I was alway taught to treat transformer secondaries as a "tap"

You need to look at 240.21(B)(2) and 240.21(B)(3) to see if you met these requirements. You?ll need transformer secondary conductor size.

 

[jim dungar]

Article 240.21(B) addresses where overcurrent protection is required on feeder taps. I was alway taught to treat transformer secondaries as a "tap"

Then you were taught poorly.

240.21(C) is specifically for transformer secondary conductors.
It looks a lot like 240.21(B), but it has more possibile 'methods'.

 

[Ken In NJ]

Thanks for your input everyone .. Code book is in truck and truck is on the road rite now. Office copy was lent to someone who lost theirs.

Not sure if it matters, County where the job is, is still using 2002 Code

Secondary conductor size is 3/0 THHN

 

[david luchini]

Not sure if it matters, County where the job is, is still using 2002 Code

Secondary conductor size is 3/0 THHN

2002 Code wouldn't make a difference. The 25' rule in 240.21(C)(6) was added in 2002.

 

[brian john]

Thanks for your input everyone .. Code book is in truck and truck is on the road rite now. Office copy was lent to someone who lost theirs.

Not sure if it matters, County where the job is, is still using 2002 Code

Secondary conductor size is 3/0 THHN

Check for over 1000 VAC, the engineer appears to be reading the wrong section of the NEC, this is (from memory and mine is very poor) that section.

In Florida with no NEC to reference.

 

[Ken In NJ]

A little FYI about the engineering Firm

If we have to change one little bit from the Cookie Cutter format, its always a nightmare. I guess with them doing the prints for the entire country for this Restaurant Chain, makes it tough .. especially when they never see the sites Or see or understand what goes on in the field.

I so much prefer working with local Firms

 

[jtester]

A little FYI about the engineering Firm

If we have to change one little bit from the Cookie Cutter format, its always a nightmare. I guess with them doing the prints for the entire country for this Restaurant Chain, makes it tough .. especially when they never see the sites Or see or understand what goes on in the field.

I so much prefer working with local Firms

I am an engineer in New Mexico and often get hired to site adapt chain restaurant plans for our local jurisdiction. I never had a problem when I needed to make changes to meet our local requirements. If it is not required by our local jurisdiction, just specified on the plans, they can often dig in their heels.

Jim T

 

[Ken In NJ]

I am an engineer in New Mexico and often get hired to site adapt chain restaurant plans for our local jurisdiction. I never had a problem when I needed to make changes to meet our local requirements. If it is not required by our local jurisdiction, just specified on the plans, they can often dig in their heels.

Jim T

I'm well aware of that Jim .. and have seen it many times in the past.

It's just real sad to see some of these Franchisees trying to get a store open at a reasonable cost .. only to have to spend extra $$ for unnecessary things spec'd out on a cookie cutter type print. Not the case this time with the service drawling .. but with many other items on the prints. Your dammed if you do (added costs) and damed if you don't (Failed inspections, sometimes)

 

[Ken In NJ]

I thank everyone one for their input so far !!!

Another issue has been brought up by the inspector after to speaking to him on the phone late afternoon ..

While he agrees that no secondary fused safety switch is required and that the main breaker in the Panel 15' or less away is OK

He now says that a Primary Side in-site disconnect is required ???

The transformer is protected by an outdoor fused lockable safety switch already .. with less then 20' of conductors in between ..

Does this in fact need an in-site switch ? Code Reference ??

Thanks in advance

 

[shamsdebout]

Sounds like the inspector is thinking of article 110.58 Disconnecting Means that calls for a disconnecting means within sight of the transformer.

I think it is a good idea to add the disconnecting mean inside.

 

[PUEE]

I hope the inspector is not referencing article 110.58 since this is for Tunnel Installations over 600 Volts, Nominal.

 

[PUEE]

To All,

The fact that is missing in this whole discussion is that the revised drawings for the change in system voltage indicated that there was a fusible disconnect on the secondary side of the transformer feeding a main lug only panel. The panel was not specified as a main circuit breaker panel. Please note that the revision made by providing a main circuit breaker panel is not a problem in our eyes it was just an unexpected change to our design. Many times I have had electrical contractors indicate that a fusible disconnect switch is more cost effective than having a main circuit breaker panel.

And YES I AM A MEMBER OF THIS FORUM AND DO READ THESE POSTS IN THE EVENINGS.:grin:

 

[iceworm]

article 110.58, Disconnecting Means

Well, the OP could point out to the inspector that Tunnel installation, over 600V doesn't really apply

I think it is a good idea to add the disconnecting mean inside.

For this disconnecting means, do you recommend a switch, a fused switch, or a CB?

Why is that (a good idea)? What is gained? Not from a legal code aspect, but rather from a design aspect, how does the extra disconnect help safety, operation, or maintenance?

ice

 

[shamsdebout]

Well, the OP could point out to the inspector that Tunnel installation, over 600V doesn't really apply


Thanks for the clarification, I am not sure what I was thinking. I am going to blame on it being sick.


For this disconnecting means, do you recommend a switch, a fused switch, or a CB?

Why is that (a good idea)? What is gained? Not from a legal code aspect, but rather from a design aspect, how does the extra disconnect help safety, operation, or maintenance?

ice

If I am reading correctly the OCPD for the transformer is outside the building.
I think it is a good idea because having a Nonfused switch inside will allow you to deenergize the transformer to change taps, or replace if damaged without going outside, especially in a thunderstorm :grin:

 

[Ken In NJ]

To All,

The fact that is missing in this whole discussion is that the revised drawings for the change in system voltage indicated that there was a fusible disconnect on the secondary side of the transformer feeding a main lug only panel. The panel was not specified as a main circuit breaker panel. Please note that the revision made by providing a main circuit breaker panel is not a problem in our eyes it was just an unexpected change to our design. Many times I have had electrical contractors indicate that a fusible disconnect switch is more cost effective than having a main circuit breaker panel.

And YES I AM A MEMBER OF THIS FORUM AND DO READ THESE POSTS IN THE EVENINGS.:grin:

I'm glad to see you join in

And since we are giving wedgies in the open forum I'll clear things up a tad bit more too.

Your Fact is 100% incorrect. From day one, of finding out we could only have the 277/480 this panel in question has had a main breaker. I built the service from what I know as an electrician was needed to get the job done and the store open.

The design by you or whomever was supposed to be based off of my build, which was and is done to code. I assume it was not you who I spoke to on the phone giving all the details of the build, when I received a call from Bre__ asking me explain what we built, so it could be correctly put on paper ?

The secondary fused disconnect came into this when it was shown on the drawings, even though it was not part of the build. And when I questioned that .. the below in red response is what I received.

NEC REQUIRES secondary disconnect for conductor protection on the load
side of the transformer with-in 10' and in line of site of the transformer.
Breaker in the panel CAN NOT serve as the disconnect.

The job in question .. is way behind schedule because of change delays, for a few reasons. Shall we discuss the first set of drawings showing a 400 amp single phase service, with two 6 Ton Roof Top A/C units ? Which do not exist ?

I'm glad your a member here .. I have been for a long time and have learned much by reading posts in my spare time. Its a great learning experience from your position as well as mine and all in between.

 

[shamsdebout]

Oh man this is getting real good . I heard from more experienced ones of requires for line of sight. I think I too believed that the NEC called out the disconnecting means to be in line of sight for all disconnects.

You live you learn and you get better.

 

[PUEE]

Interesting that you bring up the original design for the service being 400 amp single phase 120/240 volt. Per the site investigation report we obtain for each site the existing service voltage was 120/240 volt single phase. So if you would like to discuss that would be fine but this is the information which we received. Bad information in bad information out.....