What percentage of an electrical system, is based on the mechanical design?

[samblv]

I'm always telling architects, "I can't finalize my electrical plans, until mechanical is done with theirs!" In most cases, 50-70% of my loads, are based on the mechanical equipment. Without them, I'm unable to determine the size of my branch wiring and associated conduit, feeders, panels, switchboards, size electrical rooms and electrical service. So the point of all this is, with so much of my design dependent on mechanical, is it a "reasonable expectation" for a client (architect, developer, etc) to demand my plans are 100%, before mechanical has finished theirs?

I mean, if I've met all my due dates and notified my client of what information I need from other disciplines to finish my design, how have I not performed my contract?

 

[Carultch]

I'm always telling architects, "I can't finalize my electrical plans, until mechanical is done with theirs!" In most cases, 50-70% of my loads, are based on the mechanical equipment. Without them, I'm unable to determine the size of my branch wiring and associated conduit, feeders, panels, switchboards, size electrical rooms and electrical service. So the point of all this is, with so much of my design dependent on mechanical, is it a "reasonable expectation" for a client (architect, developer, etc) to demand my plans are 100%, before mechanical has finished theirs?

I mean, if I've met all my due dates and notified my client of what information I need from other disciplines to finish my design, how have I not performed my contract?

Sounds like you've answered your own question. 50% to 70%. I'd agree with those numbers. HVAC is a major portion of a building's load.

It sounds like you've performed all that you can within your contract at this time. I suppose the remainder of your contract, is that you can promptly return an updated set as soon as the HVAC people are done with their drawings, when you receive them a month or several months later.

 

[jglavin427]

I'm always telling architects, "I can't finalize my electrical plans, until mechanical is done with theirs!" In most cases, 50-70% of my loads, are based on the mechanical equipment. Without them, I'm unable to determine the size of my branch wiring and associated conduit, feeders, panels, switchboards, size electrical rooms and electrical service. So the point of all this is, with so much of my design dependent on mechanical, is it a "reasonable expectation" for a client (architect, developer, etc) to demand my plans are 100%, before mechanical has finished theirs?

I mean, if I've met all my due dates and notified my client of what information I need from other disciplines to finish my design, how have I not performed my contract?

The alternative is to oversize everything in anticipation of worst-case loads, so I would say the client would do well to be patient and wait for the coordinated design. Unfortunately electrical is one of the last disciplines in line in terms of coordination (mainly waiting for mechanical, plumbing, fire protection, and sometimes a lighting/interior designer depending on the type of project), so we are often placed under difficult schedules.

 

[kwired]

I'm not an engineer but have to design a majority of what I wire and have same problem, just my projects are often smaller then what you may be designing, but is still a problem when you don't know what you will need to supply. People want estimated costs for a project and a lot always depends on what will be there for HVAC and it is never decided yet when they want an estimate from me:roll: