Value engineering

[Alwayslearningelec]

I just read an article on EC&M and they mentioned value engineering areas and they mentioned VE areas for switchgear and panels and they listed the following as potential savings:

1. AIC ratings
2. Feed thru lugs
3. Bolt on as compared to Snap in.

What determines when feed thru lugs can be incorporated into the design? Is there code that also comes into play?

How would you purpose an AIC change to something other than what the schedules show. If the engineer came up with those ratings isn't that final based on some sort of calculations.

If bolt on are cheaper why ever use snap in? Are most commercial panels nowadays bolt on anyway? Thanks

 

[Sierrasparky]

fully rated vs. series rated
push on are cheaper in most cases that bolt on. This saves

 

[mkgrady]

You could propose VE with reduced AIC by showing that the specified is overkill. No different than any other requirement that is more than needed to do the job. Just be prepared to show them your calcs's and how much they will save.

 

[Alwayslearningelec]

You could propose VE with reduced AIC by showing that the specified is overkill. No different than any other requirement that is more than needed to do the job. Just be prepared to show them your calcs's and how much they will save.

How is AIC calculated?

 

[Alwayslearningelec]

fully rated vs. series rated
push on are cheaper in most cases that bolt on. This saves

Can you explain series rted versus fully rated? Thanks

 

[Sierrasparky]

Fully rated equipment would be as follows.:
lets say the engineer states that the available fault current is 42k. well if you have a fully rated system then all your panels and breakers down stream need to be rated at 42k also. This can be expensive. However if you are allowed to have a seiries rated system then you would have in most cases. The main SWG rated at 42k then sub breakers at 22 and final branch breakers at 10K.
Much cheaper.

 

[don_resqcapt19]

How is AIC calculated?

Its not calculated. It is an equipment rating and has to be higher than the available fault current at that point in the circuit. The available fault current is calculated.

 

[Alwayslearningelec]

Its not calculated. It is an equipment rating and has to be higher than the available fault current at that point in the circuit. The available fault current is calculated.

Thanks Don. So how is that calculated? If you have two panels feeding each other with a 22AIC rating???

 

[don_resqcapt19]

Thanks Don. So how is that calculated? If you have two panels feeding each other with a 22AIC rating???

The calculations start with the available fault current at the utility transformer. That comes from the utility and then you do calculations based on the size and length of the wire and a number of other things to get the available fault current at the downstream points. Most engineers use a software program for the calculations. It is not a simple calaculation to do correctly, especially on a system of any size.

 

[Alwayslearningelec]

The calculations start with the available fault current at the utility transformer. That comes from the utility and then you do calculations based on the size and length of the wire and a number of other things to get the available fault current at the downstream points. Most engineers use a software program for the calculations. It is not a simple calaculation to do correctly, especially on a system of any size.

Got it, thanks

 

[cdslotz]

The calculations start with the available fault current at the utility transformer. That comes from the utility and then you do calculations based on the size and length of the wire and a number of other things to get the available fault current at the downstream points. Most engineers use a software program for the calculations. It is not a simple calaculation to do correctly, especially on a system of any size.

Yes. It requires the available fault at the utility xfmer and the impedance. Also, you need to know each feeder length, type of conduit, type of wire.
Basically you have to have a complete takeoff with all of that info.
What you might do is ask your supplier to quote you an alternate for series rating to arrive at a magnitude of savings that you can propose, subject to approval. If the owner wants to consider it, the EE will probably go along.