What are your most common/frustrating design mistakes?

Status
Not open for further replies.

ptrip

Senior Member
Where do you put the home runs on a circuit for multiply rooms?

Do you always put it to the closest point in respects to the panel?

Do you just run it to any light on the circuit for a clear presentation or do you bring it to the switch?

If you don't bring the power to the switch then your creating either a secondary wire or conduit back to switch or possibility creating a raceway in a light that is not rated for the service.

While it might be understood where to bring a branch circuit, some would say it is simple enough.
If the work is UL or quality inspected, its destracting to have to argue with an inspector why one did not follow the Spec's or drawing as shown.

Do you ever look at the HVAC plan and the sprinkler plan for the layouts in hallways for Grilles and head placements? Seems no one ever does.
Either one of two things happen everyones needs to be in the same space or there's no over head space to get by the HVAC main trunk in the hallway.

Then theres always seems to be some problem with a Grille to the smoke detectors...

Homerun for a lighting circuit is attached to the first light from the switch. This is how I was taught and how each company thereafter has done it as standard. Now, for mechanical equipment that goes thru motor rated toggle switches, the homerun comes off the switch. It just seems more logical to me that way.

We coordinate lights and HVAC grilles in-house, but sprinklers are performance spec'd. We don't locate heads, so we unfortunately can't coordinate their locations at design.

Smoke detectors have become a non-issue in most of my buildings now as they are fully sprinkled. (Notification is by the sprinklers, not by smoke detectors now) I only need duct detectors as required and a smoke above the FACP.
 

ptrip

Senior Member
#1 problem with designs from architects and engineers:

Lack of compliance with section 505 of the IECC. Almost every single State in the Union has agreed to comply with energy requirements from the federal government and the IECC applies is most cases. In our state, it always applies. I reject more electrical drawings for this reason.

#2 on printed drawings: Not specifying conductor insulation and conduit type. Just labeling the drawings as #4 Cu in 3" conduit does not help me to do fill calculations.

I agree, IECC (or ASHRAE 90.1) compliance is probably the one thing I tend to forget. Funny thing ... last job that I submitted I had done it ... and forgot to submit it with the drawings! <shaking head> At least that was a REALLY easy correction response item!

Conductor insulation is called out in our spec book ... is this not sufficient? With my work, we really only use about three types of conductors, since it's either service entrance, dry location in conduit or underground.
 

ptrip

Senior Member
During my 37 years of working mostly from engineered drawings we didn't see that many problems. We got paid to put it in, paid to take it out or paid to fix it. I don't have any complaints at all, some things just can't be avoided.

That's just the thing. I don't mind paying you to put it in ... but I get hollered at when I have to pay you to take it out and fix it! ;)
 

ptrip

Senior Member
I have a job checklist I usually try to run through before I send out a set of drawings. A few things to check:

1. Did the legend get put on the drawings? (I don't think I have ever sent out a set without one, but I frequently don't notice we don't have a legend until the project is almost complete.)

I've never sent one out final without a legend, but I sent out a Progress set without one and got my wrists slapped. I've also received comments when the legend is a cookie cutter legend and not customized for the project.

2. Running 500 kcm wire from a transformer to a 400 A breaker. Or (2) sets from a transformer to a 800 A breaker. Or (3) sets to any 1200 amp breaker.

You have me confused here. These are good things or bad things?

3. Not getting two emergency lamps over the exterior doors.

Yeah ... I've been bit by that one. But I'm forgetting the lesson learned since it's so often not addressed and I work with designers that haven't been bitten by it yet so they don't think it's an issue.

4. Architects like to flip the door swings at the last minute, and not tell anyone. Guess whose fault it is when the light switches wind up behind the doors.
5. Always show doors on the lighting plan (see number 4 above).

Agreed ... also, make sure there aren't sidelights where you want to put the switches.

6. Make sure an important layer isn't turned off at the last minute. (ie: drawings go out without any smoke detectors shown).

For some reason I always seem to have the opposite affliction ... which also causes RFIs.

7. I always make a note to field verify any equipment requirements. There are frequently minor changes in their requirements that nobody can know about until long after the drawings are out.

Love the CYA notes. But you're right, especially with jobs where three or more manufacturers are required. You can't design specifically to all of them.


8. I always make a note to coordinate all outlet locations. Things get changed (even after the drawings go out), and I always get blamed when the contractor puts an outlet behind a cabinet.

Steve

One thing I tend to forget with outlet locations is heights. I put an outlet on a wall with a cabinet, I see it above the cabinet. But if I don't specify it, then I can't argue when it's installed at 18" aff ... since that's what my legend called for!

Thanks for your input!!
 

480sparky

Senior Member
Location
Iowegia
Without reading the whole thread, I'm gonna throw this one out:

Many commericial buildings have Men & Womens' restrooms. Usually, a SP switch is installed in each (or an occupancy sensor) to turn the lights on and off.

Seems no EE that designs the buildings I wire can understand that if you use circuit LB12 for the mens room, and circuit LC26 for the womens, you cannot take those two circuits to the same exhaust fan.

When I present this problem to the designer/engineer, they simply say to rewire the switches to 3-ways.:confused:

What further compicates the matter is when there's a third restroom for "Family".:mad:
 

ptrip

Senior Member
Without reading the whole thread, I'm gonna throw this one out:

Many commericial buildings have Men & Womens' restrooms. Usually, a SP switch is installed in each (or an occupancy sensor) to turn the lights on and off.

Seems no EE that designs the buildings I wire can understand that if you use circuit LB12 for the mens room, and circuit LC26 for the womens, you cannot take those two circuits to the same exhaust fan.

When I present this problem to the designer/engineer, they simply say to rewire the switches to 3-ways.:confused:

What further compicates the matter is when there's a third restroom for "Family".:mad:

I attached a wiring diagram for restroom fan lights and common restroom exhaust. Our biggest issue lately is the 277V lights and 120V exhaust fan. Yes, the restrooms are generally on the same power circuit ... but that doesn't matter with this setup. Thoughts?

This wiring diagram was being used in this office when I started here ... I haven't had any personal contractor reactions to it yet.
 

ptrip

Senior Member
Not in any particular order:

1. Conduit fill and conductor derating.
2. Arc Flash/Short Circuit Current Rating.
3. Not using devices within the manufacturer's specifications, especially supplementary OCPD's.
4. Grounding of cabinets downstream of an isolation transformer.
5. Conductors undersized per the upstream fuse.
6. Lack of OCPD co-ordination.

...and my personal pet peeve of the week...

7. Not reading the manufacturer's manual until after the design was completed and their product is sitting on the shop floor.

I have been guilty of all of that.

Some of the coordination issues have to be left to the contractor due to the "multiple manufacturer" requirement by many owners. Trip-current current curves can vary widely from manufacturer to manufacturer and there isn't any budget to do coordination for every possible combination in the spec.

There are things we, as designers, need to start doing that we haven't had to do in the past ... and one of those thing is arc flash rating. Now ... if only our company could spring the 5 figures for the fancy software!

Conductor and conduit sizing. So seemingly simple ... but yet so complex. I'm amazed at how often I can size things one day ... and go back to it a week later and change the sizes around. :roll:
 

cowboyjwc

Moderator
Staff member
Location
Simi Valley, CA
Got another one. Me: "You know that building has a rated corridor running all through it" EE: "No I didn't, I've never actually been out to the site."
 

elohr46

Senior Member
Location
square one
I attached a wiring diagram for restroom fan lights and common restroom exhaust. Our biggest issue lately is the 277V lights and 120V exhaust fan. Yes, the restrooms are generally on the same power circuit ... but that doesn't matter with this setup. Thoughts?

This wiring diagram was being used in this office when I started here ... I haven't had any personal contractor reactions to it yet.

most office buildings will have the bathroom ex. fan(s) controlled by the BAS (if there is one) one hour before employees arrive 'til one hour after they leave. The fan needs to be running non-stop in the men's room for sure.
 

steve66

Senior Member
Location
Illinois
Occupation
Engineer
I agree, IECC (or ASHRAE 90.1) compliance is probably the one thing I tend to forget. Funny thing ... last job that I submitted I had done it ... and forgot to submit it with the drawings! <shaking head> At least that was a REALLY easy correction response item!

Sometimes we have to throw the plan reviewers a bone, just to keep them happy. :grin:
 

steve66

Senior Member
Location
Illinois
Occupation
Engineer
Running 500 kcm wire from a transfromer to a 400 A breaker. Or (2) sets from a transformer to a 800 A breaker. Or (3) sets to any 1200 amp breaker.

You have me confused here. These are good things or bad things?

Those are bad things. I get in the habit of using 240.4(B) so often, I forget there are times you can't put 380A wire on a 400A breaker. Transformer secondary conductors are one of those times. See 240.21(C) - specifically, the last sentance (before 240.21(C)(1) where it says you can not use 240.4(B).

Also, you can't use 240.4(B) for circuit breakers over 800 amps. Three sets of 500 KCM would be good for 1140 amps. So you need a breaker sized at 1140 amps or less. (Most 1200 amp breakers can be set at 1100 amps, so this usually isn't too much of a problem, but it would be easier if 600 KCM wire had been specified.)

Steve
 

e57

Senior Member
We coordinate lights and HVAC grilles in-house, but sprinklers are performance spec'd. We don't locate heads, so we unfortunately can't coordinate their locations at design.
Common excuse - but often the sprinkler plan is several months or more older than all other revisions of other RCP's - available to everyone and changes little after plan review.... Yet it takes two Foremen <5 minutes on site to realize the conflicts on some large peices of paper, another hour or so to generate a copy and paste RFI for 20+ RFI's of the same topic and wording but location specific, and another 3 months or more to get someone to not bury their head in the sand about it???? When at some point after plan review of the sprinkler set - that layer can be added as backround during the numeous revisions post de facto. It can be done - I've seen it - it's just rare for some reason.... Otherwise - It becomes what I call Contractor Aided Design.... Or Build and then Design...
 

ptrip

Senior Member
I attached a wiring diagram for restroom fan lights and common restroom exhaust. Our biggest issue lately is the 277V lights and 120V exhaust fan. Yes, the restrooms are generally on the same power circuit ... but that doesn't matter with this setup. Thoughts?

This wiring diagram was being used in this office when I started here ... I haven't had any personal contractor reactions to it yet.

most office buildings will have the bathroom ex. fan(s) controlled by the BAS (if there is one) one hour before employees arrive 'til one hour after they leave. The fan needs to be running non-stop in the men's room for sure.

I generally use this for K-12 schools ... and no ... they only want the fans running while the lights are on. This includes when somebody is in there and a 30 minute delay after they've left.
 
Do you ever look at the HVAC plan and the sprinkler plan for the layouts in hallways for Grilles and head placements? Seems no one ever does.
Either one of two things happen everyones needs to be in the same space or there's no over head space to get by the HVAC main trunk in the hallway.

Then theres always seems to be some problem with a Grille to the smoke detectors...


Absolutely my biggest pet peeve over the years has been coordination with other systems.

Everybody seems to want the center of the hallway.

You get a 12' structural ceiling and a 10' finished ceiling, 18" duct work; Sprinkler pipe; 12" high recessed cans all running straight down the middle.

The Seattle Art Museum was horribly designed from an installer's point of view.

The solution was to cut "hats" into the duct work where our lights went.
 

ptrip

Senior Member
We coordinate lights and HVAC grilles in-house, but sprinklers are performance spec'd. We don't locate heads, so we unfortunately can't coordinate their locations at design.

Common excuse - but often the sprinkler plan is several months or more older than all other revisions of other RCP's - available to everyone and changes little after plan review.... Yet it takes two Foremen <5 minutes on site to realize the conflicts on some large peices of paper, another hour or so to generate a copy and paste RFI for 20+ RFI's of the same topic and wording but location specific, and another 3 months or more to get someone to not bury their head in the sand about it???? When at some point after plan review of the sprinkler set - that layer can be added as backround during the numeous revisions post de facto. It can be done - I've seen it - it's just rare for some reason.... Otherwise - It becomes what I call Contractor Aided Design.... Or Build and then Design...

No, actually this is not the case. The actual sprinkler plans are not fully created until the project has been awarded to the contractors. Fire Protection plans that leave our office (and every other office I've worked at) are very schematic only. Mains and risers are shown ... no heads, no detail. Actual locations are determined by the sprinkler contractor, who is hired as a subcontractor to the plumbing contractor. The plumbing contractor can't hire them until they have been awarded the job ... which is months AFTER the final RCPs have been created. I understand you may see things differently on your projects ... but this is how things work in my area.

I will admit when I flub things. There are times when I really don't know the means and methods to get something done so I create a CYA note to tell you to figure it out. There are times when the deadline crept up on me and I never did figure out "x". I don't do arc flash calculations (since it depends specifically on the gear and equipment used, and I don't know that until I get submittals). And there are a few other things, I'm sure. But I can't coordinate sprinkler head locations before you see the plans.

Honestly ... I haven't seen too many RFIs dealing with this coordination. The Fire Protection contractors I've had must've been good!
 

e57

Senior Member
But I can't coordinate sprinkler head locations before you see the plans.

Honestly ... I haven't seen too many RFIs dealing with this coordination. The Fire Protection contractors I've had must've been good!
I think you missed my point about the revisions... If the sprinkler plan is dated 2008, and the last revision of lighting is 2009 - means there is no coordination between plans in the event of conflict... If you don't get too many RFI's about this - the client may have already made an economic decision about who'll sort it out for you... ;) Depending on the cost of the trade CO and designer fees. Often it's the plumber shifting... But after we get into a fist fight on site about it.... :D
 

sparkie001

Senior Member
I have been guilty of all of that.

Some of the coordination issues have to be left to the contractor due to the "multiple manufacturer" requirement by many owners. Trip-current current curves can vary widely from manufacturer to manufacturer and there isn't any budget to do coordination for every possible combination in the spec.

The solution is that you do your coordination settings AFTER receiving the submittals showing what is being purchased. Then you issue the settings as an ASI.

Regarding other's comments:
The sprinkler contractor's submittals are never shared with the EE. Ditto most of the time for elevator and HVAC submittals. And why does the EE have to verify the elevator voltage when the EC is the one connecting it? :)

I happily answer RFI's within a day or two. Now if I could just get the EC to think ahead and submit the RFI's without every one being labeled URGENT. And for example talk to the mech contractor instead of writing an RFI asking what a particular fan is being used for.

Thanks for the comments as well... they are helpful. I will add the missing ones to our 14 page checklist.
 

e57

Senior Member
Yep - this is an aptly named thread.... :roll: Lot's of NMJ, and NMF... Most, if not all plans eventually land in one place - the printer, and for the most part most printers host virtual plan rooms. (In an effort to get more printing - under the guise that people use it to discuss and coordinate to avoid conflict... Create more plans, print more...) If not there - the advent of so many electronic software and transmission protocols like e-mail and FTP make it easy and cheap to share information. And no-one does....

And right after they get off the printer the mistakes are evident when the trades meet while they put a ladder in the same place at the same time, or worse - in reversed order of priority. (Big holes - small holes - function - form)

That is the most frustrating design mistake... Leave the details to Joe in the field, then get upset that they're asked to clarify or resolve anything. Deny responsibility. Then further get upset if their design got changed, or that design decisions were made without them... Because the design didn't work in the first place - because each compartmentalized element was done by individual people who closed their eyes to the other parts of the whole.
 

jrannis

Senior Member
This might not be as technical as the other questions but,

Why do we have a nice sheet of boiler plate specs/notes that obviously do not pertain to the project?
I can tell that some of these notes have been complied over several decades. I still see THW mentioned on some notes. Has anyone here installed any THW in the last 25 years?
Why do engineers call out solid wire for #12? Why is that done? I don't like using solid #12 if I can help it!
 
Status
Not open for further replies.
Top