Why is it the standard now that electrical engineers write in their specification that the contractor shall be responsible for short circuit and coordination study? As an electrical engineer myself, I think that’s completely wrong. It should be the responsibility of the engineer to do the short circuit analysis and coordination. I used to work for a large MEP firm and non of them even checked this stuff unless they are paid to do it.
Short Circuit and Coordination Responsibility
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petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- Semi-retired engineer
What difference does it make what entity is responsible as long as it gets done?
In a lot of cases the contractor is making so called value engineering changes that might affect these calculations, so it makes at least some sense for them to have to deal with the consequences of that value engineering instead of it getting lost in the shuffle.
Plus, if the engineer makes his calculations based on his estimates of wire lengths and sizes, that can easily change. Someone needs to keep up with that. The contractor is the obvious person to do that.
As an engineer, you have to design a system that will work. Typically it will take the fault current and coordination studies to feel comfortable that what I am designing will work, so I will do those studies as part of my design. I require the contractor to perform the study as well to capture the actual installed conditions. For example, I may have done the coordination study based on Square D equipment, but the contractor bought Siemens instead.
- Location
- Wisconsin
- Occupation
- PE (Retired) - Power Systems
The issue is that it gets done correctly and in a timely fashion.
The specifications should require a preliminary, based on estimated conductors, before approving equipment submittal drawings. A final report should be required after the installation, and change orders, have been completed.
I did one hospital that had three different phase done by two different contractors over a period of 3 years. The hospital was provided with 3 separate reports rather than one single coordinated study. I think there were problems getting he occupancy permit due to this.
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What difference? More room for error, and also having the customer have a peace of mind that the engineer is doing their due diligences. The designer knows more about their system than the contractor because they designed it.
romex jockey
Senior Member
- Location
- Vermont
- Occupation
- electrician
I'm not sure why you think that's "standard". It's an option, but I don't think its standard by any means.
Some engineers may do the short circuit design, and still add a note to make the contractor responsible. That way the contractor is on the hook for any changes they make.
If you spec. 3 different gear manufacturers, its almost impossible to do a coordination study for anything more than the basis of design.
ATS's severely complicate things too. Its hard to design not knowing what manufacturer you will end up with.
In most cases, if the engineer puts the contractor in charge of doing these types of calcs., the engineer should still be reviewing the work on shop drawings.
Some engineers may do the short circuit design, and still add a note to make the contractor responsible. That way the contractor is on the hook for any changes they make.
If you spec. 3 different gear manufacturers, its almost impossible to do a coordination study for anything more than the basis of design.
ATS's severely complicate things too. Its hard to design not knowing what manufacturer you will end up with.
In most cases, if the engineer puts the contractor in charge of doing these types of calcs., the engineer should still be reviewing the work on shop drawings.
petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- Semi-retired engineer
Why would there be more room for error? And why would the customer even care? Most of them probably don't care other than having to pay for it.
Same likely to me that the contractor knows a whole lot more about what was actually installed than the engineer does.
David Castor
Senior Member
- Location
- Washington, USA
- Occupation
- Electrical Engineer
In my experience, the main issue is money. The coordination cannot be done until the equipment is purchased and suppliers are known. In terms of the engineer's contract with the owner, this would be considered "Services During Construction" or perhaps commissioning and may not be part of the engineer's scope of work. When competing for engineering services for design, this generally isn't included unless specified by the owner. It's simpler to include the cost of the coordination study in the overall construction bid. On a large project, the cost of a coordination study is in the noise level when looking a general construction bid. It's not the best way to do it from an engineering perspective.
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