I am working on a design build project of a 2 1/2 story commercial office building. The engineer has sized the main service at 1200 amp 120/208. The HVAC load consists of 8 units that have a ckt. amp. of 40.2 per unit. The units are straight heat and are single phase. The building is 3000 square feet per floor on the 1st and 2nd floor and 1500 square feet in the basement. If you figure 20VA per foot(which to me would be extremely high) I am coming up with around 416 Amps. What are some opinions on what size service that you would install? I think that a 600 amp would be enough for this space. The building is land locked and no place for expansion.
Don't agree with engineers service calculations!
- Thread starter rlwiley
- Start date
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I would install what was engineered.
The engineer may working for his clients best interest - future tenant demands. Who knows what the future holds and what the demand will be on an electrical system - elevators, chillers, maybe a lab of some sort....who knows?
The client may have even asked that the service be 1200A.
The engineer may working for his clients best interest - future tenant demands. Who knows what the future holds and what the demand will be on an electrical system - elevators, chillers, maybe a lab of some sort....who knows?
The client may have even asked that the service be 1200A.
As an engineer we always as a rule over design if we can get away with it. It is very hard to explain to a customer why we undersized in the first place and he needs an upgrade now.
My guess is the engineer knows something you do not and is planning on the future as it is much more economical on the initial build versus an upgrade later. As for you being the contractor, you can only profit from the experience.
My guess is the engineer knows something you do not and is planning on the future as it is much more economical on the initial build versus an upgrade later. As for you being the contractor, you can only profit from the experience.
petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- engineer
Re: Don't agree with engineers service calculations!
what possible benefit is it to you to install a lesser service? if the specs call for something that exceeds the bare minimum the code requires, that is to your benefit as it increases your potential profit.
my guess is the engineer knows something about likely future demand that you do not.
i don't do this kind of design but I often specify feeder size that exceeds the bare minimum a machine needs right now because I know or suspect that a future upgrade will require more juice and it is much cheaper to run the feeder once rather than twice.
what possible benefit is it to you to install a lesser service? if the specs call for something that exceeds the bare minimum the code requires, that is to your benefit as it increases your potential profit.
my guess is the engineer knows something about likely future demand that you do not.
i don't do this kind of design but I often specify feeder size that exceeds the bare minimum a machine needs right now because I know or suspect that a future upgrade will require more juice and it is much cheaper to run the feeder once rather than twice.
- Location
- Massachusetts
I also agree with the others, install what was specified.
Price it that way and make money. 8)
If your pricing correctly the profit should be higher on the 1,200 amp than the 600 amp service.
I can't help but appreciate engineers over engineering and specifications of copper. 8)
Can you tell me why a 3000 amp 480Y/277 service needs a full sized neutral?
Who cares......they want and we are happy to provide it.
Price it that way and make money. 8)
If your pricing correctly the profit should be higher on the 1,200 amp than the 600 amp service.
I can't help but appreciate engineers over engineering and specifications of copper. 8)
Can you tell me why a 3000 amp 480Y/277 service needs a full sized neutral?
Who cares......they want and we are happy to provide it.
The rest of the story......
Since this is a design/build I am also looking out for the best interest of the client. Which is to save them money. Why would it be necessary to double the size of a service if there is no need. I am by no means trying to slam the engineer. With the cost of copper at an all time high why should the owners pay for something that will never be needed. I was just questioning the service size to get feed back (from this forum) on what it thought a would a minimum size service would be. Just based on a typical commercial office building with typical loads. I have a good friend of mine that is an engineer. His office building is 4 stories with 4000 square per floor loaded with computers on every floor and the service is a 400amp 120/208. Why would you possibly need 3 times more service for half the size building with the same equipment going in the building. Once again I will say that this building is landlocked. There is know way to add on unless you level the building and start over.
Since this is a design/build I am also looking out for the best interest of the client. Which is to save them money. Why would it be necessary to double the size of a service if there is no need. I am by no means trying to slam the engineer. With the cost of copper at an all time high why should the owners pay for something that will never be needed. I was just questioning the service size to get feed back (from this forum) on what it thought a would a minimum size service would be. Just based on a typical commercial office building with typical loads. I have a good friend of mine that is an engineer. His office building is 4 stories with 4000 square per floor loaded with computers on every floor and the service is a 400amp 120/208. Why would you possibly need 3 times more service for half the size building with the same equipment going in the building. Once again I will say that this building is landlocked. There is know way to add on unless you level the building and start over.
hardworkingstiff
Senior Member
- Location
- Wilmington, NC
I have a friend who owns a business. He is always trying to tell the customer how to lower their cost. Some of the customers want certain things and don't mind paying for them. It amazes me when he trys to talk them out of the bells and whistles to save a dollar.
My motto is to give them fountains if they want fountains (and are willing to pay for them).
I'm a contractor. I install stuff. If you want it, and can pay for it, who am I to talk you out of it?
My motto is to give them fountains if they want fountains (and are willing to pay for them).
I'm a contractor. I install stuff. If you want it, and can pay for it, who am I to talk you out of it?
jeff43222
Senior Member
- Location
- Minneapolis, Minnesota
Sometimes I come across people that want me to do something for them, and I talk them out of it and give them a more cost-effective option to solve their problem. I once had a customer ask me to upgrade their service to 200A, but they were barely even using the 100A service they had (all appliances were gas). They had no plans to get any big electric appliances. They mistakenly thought they needed a service upgrade because they needed more panel slots for new circuits in the newly finished basement. I told them what they actually needed was a panel upgrade and explained how they'd get what they needed and spend a lot less money.
Sure, I make less money in cases like this, but people sure remember that I was the guy that was honest with them and wasn't just looking to maximize my bottom line at their expense. Guess what kind of effect this has on my referral business.
As to the OP, if you are concerned that the customer is buying way more than he needs, I'd have a chat with him and make sure he knows what he's doing. Maybe there is a good reason for the big service that you don't know about yet.
Sure, I make less money in cases like this, but people sure remember that I was the guy that was honest with them and wasn't just looking to maximize my bottom line at their expense. Guess what kind of effect this has on my referral business.
As to the OP, if you are concerned that the customer is buying way more than he needs, I'd have a chat with him and make sure he knows what he's doing. Maybe there is a good reason for the big service that you don't know about yet.
jtester
Senior Member
- Location
- Las Cruces N.M.
I think there is no question that different engineers, given the exact same information and design parameters, would come up with very different sizes for the service.
I am a small firm, work out of my house, and I'm sure that the service I designed would be significantly smaller than the one designed by the firm that leases the top floor of the bank tower. Larger firms have justification for why they oversize things, but they do.
If you, as a design build contractor, have hired the engineer to work for you, I agree you can expect the engineer to at least explain his design. If you didn't hire the engineer, your responsibility probably is limited to mentioning your idea to the Owner and engineer.
Even with my frugal designs, I regularly get asked to justify things, and I don't mind reviewing my calculations with the Owner or Contractor at all.
Jim T
I am a small firm, work out of my house, and I'm sure that the service I designed would be significantly smaller than the one designed by the firm that leases the top floor of the bank tower. Larger firms have justification for why they oversize things, but they do.
If you, as a design build contractor, have hired the engineer to work for you, I agree you can expect the engineer to at least explain his design. If you didn't hire the engineer, your responsibility probably is limited to mentioning your idea to the Owner and engineer.
Even with my frugal designs, I regularly get asked to justify things, and I don't mind reviewing my calculations with the Owner or Contractor at all.
Jim T
- Location
- Lockport, IL
- Occupation
- Retired Electrical Engineer
What is your business relationship with this engineer? As a "design-build project," the owner will have a contract with only one company, and that company is responsible for both the designing and the building. You are obviously the builder, but does the engineer work for you, or do both you and the engineer work for some other prime contractor?
I ask because it impacts your ability to influence the final call on this question. In any event, I think it would be perfectly in-line for you to ask the engineer for a copy of the calculation used to come up with the 1200 amp service.
Speaking as an engineer who has done design-build projects, I would be grateful to get questions and suggestions from my "partner" company who is going to build what I design. I may stand firm on my choices, but I would be willing to explain to you the reasons for my choices. I strongly disagree with the suggestions that you simply build what I over-designed, in order to increase your own profit. I strongly agree with your statement that it is also your responsibility to look after the owner's best interests.
I ask because it impacts your ability to influence the final call on this question. In any event, I think it would be perfectly in-line for you to ask the engineer for a copy of the calculation used to come up with the 1200 amp service.
Speaking as an engineer who has done design-build projects, I would be grateful to get questions and suggestions from my "partner" company who is going to build what I design. I may stand firm on my choices, but I would be willing to explain to you the reasons for my choices. I strongly disagree with the suggestions that you simply build what I over-designed, in order to increase your own profit. I strongly agree with your statement that it is also your responsibility to look after the owner's best interests.
I belive in oversizing as well for future expansion and upgrades, but that is crazy (if the calculations are correct), Over 200% increase come on!
Here is the way I look at it in a design build situation, you have to get to know your clients current needs and where he sees his potentially growth in the future, meaning does he have enough property to expand the building if so could it double? if not he would be limited to the current Sq' he is in and maybe pack it.
once you know all this info you could use some deductive reasoning of how much potential load could increase and up size your service accordingly. usually not anywhere near 200+%
we did have a building last year that was intentionally built with the idea of doubling the size of the manufacturing floor, (he had the property to do so), we even went as far as putting a limited amount of wiring on the expansion side of the building. so my point is It could happen, but in most cases not.
Here is the way I look at it in a design build situation, you have to get to know your clients current needs and where he sees his potentially growth in the future, meaning does he have enough property to expand the building if so could it double? if not he would be limited to the current Sq' he is in and maybe pack it.
once you know all this info you could use some deductive reasoning of how much potential load could increase and up size your service accordingly. usually not anywhere near 200+%
we did have a building last year that was intentionally built with the idea of doubling the size of the manufacturing floor, (he had the property to do so), we even went as far as putting a limited amount of wiring on the expansion side of the building. so my point is It could happen, but in most cases not.
- Location
- Massachusetts
hardworkingstiff said:
Right on. 8)
Some people like to pay $250.00 for pair of sneakers, some people want twice as much power as they need. If it makes them happy all is good.
8)
All I really am interested in is getting an opinion on what a standard service size would be on a 7500 square foot building. Would you agree that 20 VA per foot would be gracious plenty for square foot calculation. A lot of the repies that I have received states that I should do what the engineer draws. Why is it wrong to question a service size that seems to me to be way out of whack. Most engineers get payed a % of the overall job cost. I think this engineer just oversized it to make more money. I was asked by the owner to make value engineering changes to get the cost down. The first thing I questioned was the need for so much service. The owner's answer is that he does not know. I would think that everyone by now knows the ridiculous cost of copper wiring. If the MDP is 150 feet away from the entrance point the following would apply. 4 sets of 4 - 350 MCM for a 1200 amp service =2400 feet of 350MCM @ $10.90 per foot = $26,160.00 just fo wire.
2 sets of 4 - 350 MCM for a 600 amp service = 1200 feet@10.90 per foot =$13,080.00 just wire.
If we also deduct the additional conduit, fiitings, etc. and the additional cost of 1200 amp gear we would probably be looking at saving the owner around $17,000.00 just for asking the engineer a question. How many jobs have you seen come in over budget that never get started. I think that it would be in my best interest to help get the job within budget.
So the question I ask this board again. Do you think that 20 VA per foot on a 7500 square foot office building with just basic loads nothing special would be a safe assumption? I am not asking for a stamped set of drawings just some opinions.
Thanks
2 sets of 4 - 350 MCM for a 600 amp service = 1200 feet@10.90 per foot =$13,080.00 just wire.
If we also deduct the additional conduit, fiitings, etc. and the additional cost of 1200 amp gear we would probably be looking at saving the owner around $17,000.00 just for asking the engineer a question. How many jobs have you seen come in over budget that never get started. I think that it would be in my best interest to help get the job within budget.
So the question I ask this board again. Do you think that 20 VA per foot on a 7500 square foot office building with just basic loads nothing special would be a safe assumption? I am not asking for a stamped set of drawings just some opinions.
Thanks
- Location
- Lockport, IL
- Occupation
- Retired Electrical Engineer
I hope that you noticed that my reply was not among them, despite my being an engineer.rlwiley said:
I have never seen that arrangement. I have seen, however, an engineer's fee being limited to no more than a specific percentage of the project costs. The percentage is usually not high enough for the engineer to make a reasonable profit on the amount of work required to perform the design.rlwiley said:
But to intentionally create a design that exceeds what the project needs, and to do it for no better reason than to increase your fee, is a breach of professional ethics. I would ask you to be slow to pronounce such opinions, unless you possess supporting evidence.
Then you are going about it in the right way.rlwiley said:
It is certainly more reasonable than 57.6 VA per square foot (equivalent to 1200 amp service).rlwiley said:
petersonra
Senior Member
- Location
- Northern illinois
- Occupation
- engineer
You seem to have a problem with the engineer but instead of asking him directly you want to go behind his back to the owner and to other people like this forum.
Show some spine and ethics and talk to the engineer about it.
Show some spine and ethics and talk to the engineer about it.
Thanks you Charles for your opinion.
Bob, I asked this question to the forum to get professional opinions. I am not an engineer and do not claim to be one. I simply wanted to make sure that my opinion was in line with what should be an appropriate service size b/f I go into a meeting with the owner and engineer. I had stated b/f that I was not trying to bash the engineer. My only intention for this questions is to some gain some knowledge from professionals b/f I go into a meeting to get the project within budget.
Thank you again to Charles for your response.
Bob, I asked this question to the forum to get professional opinions. I am not an engineer and do not claim to be one. I simply wanted to make sure that my opinion was in line with what should be an appropriate service size b/f I go into a meeting with the owner and engineer. I had stated b/f that I was not trying to bash the engineer. My only intention for this questions is to some gain some knowledge from professionals b/f I go into a meeting to get the project within budget.
Thank you again to Charles for your response.
ctrane
Member
- Location
- Jacksonville, Florida
First you should talk to the engineer. If he is a professional, and especially design build, there is a great check and balance relationship that can take place between engineer and electrical contractor. Second, this is a guess, but they seem to be sprouting up more and more, are Imaging centers. Cat Scan, X-Ray, MRI, etc...Maybe the owner is in works to attract a doctor, nice revenue. And, for a 3000sq ft. imaging center, we had to ask for a 700 Amp service, and that is at 480. So, maybe something like that is going on.
tincan44
Member
- Location
- Indian River County, Fl.
I go to work in a good mood happy with my job.
I get my itinerary hop into my truck and head to your job.
You see me pull up, meet me and ask about my day, my weekend, fishing or even the weather.
I answer politely "all is well."
"Can I see your plans and permit, please?"
I read all the electrical notes, study the plans and riser diagram.
I start the inspection and quickly realize you didn't follow what was specified.
I ask you why?
_________________________ < (insert great story here)
I tell you I NEED the engineer to approve your changes. Bring 3 copies of his statement and revised "as built" plans, WITH his raised seal, to the Building Dept for review and approval BEFORE your job will be inspected. I will give you this notice in writing, most likely, on a Yellow Tag (no fee).
Have a good day!
I drive to my next inspection.
I get my itinerary hop into my truck and head to your job.
You see me pull up, meet me and ask about my day, my weekend, fishing or even the weather.
I answer politely "all is well."
"Can I see your plans and permit, please?"
I read all the electrical notes, study the plans and riser diagram.
I start the inspection and quickly realize you didn't follow what was specified.
I ask you why?
_________________________ < (insert great story here)
I tell you I NEED the engineer to approve your changes. Bring 3 copies of his statement and revised "as built" plans, WITH his raised seal, to the Building Dept for review and approval BEFORE your job will be inspected. I will give you this notice in writing, most likely, on a Yellow Tag (no fee).
Have a good day!
I drive to my next inspection.
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