# My first load calc



## WronGun (Oct 18, 2013)

Are there any cookie cutter forms/websites you guys use for doing in depth load calculations.. I'm doing my first one and something to follow would be a big help 


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## telsa (May 22, 2015)

You lazy dogg.


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## WronGun (Oct 18, 2013)

telsa said:


> You lazy dogg.




Lol , I've honestly started it already using the code book .... it being my first one , it sure would be nice to see some sort of base worksheet... it involves large Commercial kitchen equipment and I want to check my work multiple times 


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## Glock23gp (Mar 10, 2014)

I doubt such a thing exists due to the complexity of each occupancy and bouncing between tables you can or can't use depending on certain loads.

Residential is the worst due to being able to derate your derates in certain circumstances.

Best way is to go slowly page by page in 220 breaking down each load by article and balancing your phases as you go (including neutrals).

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## HackWork (Oct 2, 2009)

For resi I just use this spreadsheet: https://www.mikeholt.com/documents/calculations/formulas/ResidentialLoadCalculations.xls


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## WronGun (Oct 18, 2013)

HackWork said:


> For resi I just use this spreadsheet: https://www.mikeholt.com/documents/calculations/formulas/ResidentialLoadCalculations.xls




Nice!


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## Southeast Power (Jan 18, 2009)

Glock23gp said:


> I doubt such a thing exists due to the complexity of each occupancy and bouncing between tables you can or can't use depending on certain loads.
> 
> Residential is the worst due to being able to derate your derates in certain circumstances.
> 
> ...


Really?
I can smash out a residential load calculation in less than a minute.


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## HackWork (Oct 2, 2009)

WronGun said:


> Nice!
> 
> 
> Sent from my iPhone using Tapatalk


That is older than I am, so hopefully it still works.

It's nice because you can add your company name to it and a job name. There is a town here that wanted a load calc when doing service upgrades, so I used to use that spreadsheet to include a load calc with every service upgrade permit application I submitted. All the inspectors liked it and a few made comments about how they didn't need to look closely at things because they are sure I did them right, based off of my going above and beyond with the load calc.


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## Glock23gp (Mar 10, 2014)

Suncoast Power said:


> Really?
> I can smash out a residential load calculation in less than a minute.


Congrats.

I'm talking about commercial and industrial sizing load, wire and conduit from xfmr to each circuit including sizing additional transformers, motors and neutral loads.

My 3 year old can do resi calcs.

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## HackWork (Oct 2, 2009)

Glock23gp said:


> Congrats.
> 
> I'm talking about commercial and industrial sizing load, wire and conduit from xfmr to each circuit including sizing additional transformers, motors and neutral loads.
> 
> ...


In all fairness, you did say "Residential is the worst" which I also kinda wondered about.


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## Glock23gp (Mar 10, 2014)

HackWork said:


> In all fairness, you did say "Residential is the worst" which I also kinda wondered about.


I meant like a multi family complex with different buildings (multiple xfmr calcs) and occupancies.

Say a residential over commercial with different occupancies downstairs to calculate different based on different lighting loads.

My bad.

As CS says.. I digress....

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## HackWork (Oct 2, 2009)

Glock23gp said:


> I meant like a multi family complex with different buildings (multiple xfmr calcs) and occupancies.
> 
> Say a residential over commercial with different occupancies downstairs to calculate different based on different lighting loads.
> 
> ...


I see what you're saying, makes sense.


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## Glock23gp (Mar 10, 2014)

HackWork said:


> I see what you're saying, makes sense.


Here's an example that was used on my supervisors test.

Other questions are

What is the load in, in amps, on the grounded conductor for the office service 

Same for multifamily building

What is min feeder conductor size for a dwelling unit using THWN-2 aluminum wire

What is minimum service rating for the multi family building if using the optional method.

What is the feeder neutral load in amps for each unit

Etc...

This is a good practice calc Wron









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## WronGun (Oct 18, 2013)

this isn't that easy for commercial. Do you guys do all your commercial load calcs yourselves? It just seems being my first time a mistake could cost me large on this type of job. Following the code book , but my numbers dont seem right...should i hire this out?

A commercial kitchen where everything could very well be running at the same time, along with lighting, receptacle and HVAC loads im looking at 325A with the potential for future additions, Im figuring 400Amps....

This just got a whole lot complicated especially when the service is 2'' underground pipe, This may put me out of this job because now it seems i may not be a big enough contractor to handle this


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## Signal1 (Feb 10, 2016)

Aren't you just starting out? One man?

If you're not comfortable with it, you may want to reconsider this job.
I don't think there's a guy on here that would look down on you for it, we've all been there.


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## WronGun (Oct 18, 2013)

I am just starting out...But this has the way its been this year....Ive been jumping in and grinding it out until i figure it out and get it..... And all those situations that were stressful are now a walk in the park because i never walked away. Im looking at this situation the same way, if i take it on the next one I will be experienced. I have the resources to pull it together....

Ive figured and designed the whole branch circuit layout...

Now that I just received more information on this job regarding the service. I need to make sure before i tell the GC we have a serious problem.

I didnt really do much calculation regarding the load...I have a list of equipment that may very well be running all at the same time day in and day out. I added up the amps and then did load calcs for the lighting and receptacles by SQ', then figured HVAC and left room for future expansion. 

which is why i came up with 325 which im upping to 400.....This is a issue with a 2'' underground pipe


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## Signal1 (Feb 10, 2016)

It sounds like you're off to a really good start and I applaud your ambition for taking things head on. What you're doing isn't easy, I know first hand.

It sounded like you were apprehensive about taking on this job because of the size of your operation. All I meant is that sooner or later you may have to say no, and there's nothing wrong with that.

Growing too fast can be a killer, many small shops find themselves with hyper-extended credit, and little to no capital real fast this way.

What ever happens good luck with it.


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## Glock23gp (Mar 10, 2014)

Did u do the calc page by page like I said in Article 220?

It looks intimidating at first but if you break it down step by step it simplifies it big time.

Lighting make sure it's all at 125%
Recep
AC heat
Equip

Why are you stuck with only a 2" conduit? 

This is an existing building retrofit?

If it's 3 phase make sure you are diving kva by square root not the voltage.

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## WronGun (Oct 18, 2013)

Yes , I did a load calc... with all the codes and rules I'm not 100% sure I'm correct. It seems I figured larger.... 

but regardless that's my main coming up from the floor , even if I could get away with 325A Using copper I'm still undersized with my pipe.

Currently the main is 225A and I've added up 260A of equipment being installed in the kitchen... this is 100% rating of some pieces and 125% of a few others.

The code says 65% of more than 6 pieces of equipment in a non-dwelling kitchen which seems odd because my list of equipment could all very well be running together


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## Glock23gp (Mar 10, 2014)

WronGun said:


> Yes , I did a load calc... with all the codes and rules I'm not 100% sure I'm correct. It seems I figured larger....
> 
> but regardless that's my main coming up from the floor , even if I could get away with 325A Using copper I'm still undersized with my pipe.
> 
> ...


What's your final kva?

And

What did u divide it by?

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## Glock23gp (Mar 10, 2014)

I see a block wall assuming meter is on the other side?

Possible to bring in a larger service outside and bring multiple conduits inside?

No matter who the contractor is (you or somebody else) the load is the same so if the service is too small it will be the EC responsibility to make it the correct size or they will have to reduce their load. Period.

Don't underestimate yourself because of potential problems. The job is the job and anyone doing it will have to make it work.

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## WronGun (Oct 18, 2013)

Yes meter is on opposite side of wall....

My VA is 105,900 which I'm going over again because something isn't right 




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## Glock23gp (Mar 10, 2014)

WronGun said:


> Yes meter is on opposite side of wall....
> 
> My VA is 105,900 which I'm going over again because something isn't right
> 
> ...


Break it down on paper step by step

Recep va per table
Lighting at 125 per table
Ac or Heat per table
Equip per table

Any other derates?

Total va / sq rt X voltage

360.25 for 208v 
415.68 for 240v


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## WronGun (Oct 18, 2013)

Yes did it all in my computer to get 105,817 total 

I'm going to go back and derate , but could it really be 65% load on kitchen equipment , look at that list ... it's not uncommon for at some point all that stuff to be running at the same time

Also , I'm thinking of future , they are definitely going to be adding equipment .. in this case I don't even think I should derate and instead give them the full calculated load , ofcourse this was mentioned by Owners....leave room for future 












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## Glock23gp (Mar 10, 2014)

Just a quick add I have total load of between 223, 268.5 & 279 amps in each leg. (So even if I balanced better it's not going to be under 200...)

That's some hefty appliance load so unless your in an absolute desperate need to be the cheapest bid and need to verify with the inspector the use of the 65% derate (I'm not sure it applies due to the wording intermittent use even though some is thermostatically controlled) I would look for the best way to get 400 amps in there. (Especially if there is to be any future expansion)

Just my $.02

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## WronGun (Oct 18, 2013)

Glock23gp said:


> Just a quick add I have total load of between 223, 268.5 & 279 amps in each leg. (So even if I balanced better it's not going to be under 200...)
> 
> That's some hefty appliance load so unless your in an absolute desperate need to be the cheapest bid and need to verify with the inspector the use of the 65% derate (I'm not sure it applies due to the wording intermittent use even though some is thermostatically controlled) I would look for the best way to get 400 amps in there. (Especially if there is to be any future expansion)
> 
> ...




I agree , and I appreciate your opinion .. 


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## telsa (May 22, 2015)

Electric restaurants are power pigs, no doubt about it.

2" pipe is too small, you're way past 200A.

This build demands 400A 3 phase... and there is no way that the customer is going to stop with just this gear.

An electric restaurant will fire up every piece of gear at the same time -- at the start of the day.


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## WronGun (Oct 18, 2013)

Yes ,

This actually isn't a Restaurant that seats people but it is a catering and food vending company that packages/seals food .. which I'm sure this equipment which they have not listed also has a considerable draw


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## telsa (May 22, 2015)

WronGun said:


> Yes ,
> 
> This actually isn't a Restaurant that seats people but it is a catering and food vending company that packages/seals food .. which I'm sure this equipment which they have not listed also has a considerable draw
> 
> ...


Hence this is a food factory.

It's an even BIGGER power pig.

You can rest assured that every piece of gear will be fired up all at the same time -- and kept roaring for the better part of the workday.


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## frenchelectrican (Mar 15, 2007)

I came up the figures and I am pretty much hitting near 300 amp line.


You denfently need 400 amp service that is the barebone size what ya got on the figures.,,

If the owner plan to add more equiment in not too far in future ya have to kick it up to at least 600 maybe 800 amp service on 208Y120 volt service. 

I would suggest to talk to the owner what the plans for future and heavy up hard in future. 

The other thing is the photo what you posted I dont know how it got passed with inspection like that with metered and unmetered conductors in the same encloseure box .,, :blink: that part the POCO will really raise a ruckus on that. ( trust me on that I have see it over here as well.)


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## WronGun (Oct 18, 2013)

frenchelectrican said:


> I came up the figures and I am pretty much hitting near 300 amp line.
> 
> 
> 
> ...




thanks for checking that. 

Also , Im not sure what you mean The main comes up into the box and goes out to the meter and comes back in. They then land on the Line side of the 225A Disco and branch out from there?

Also, Here is another picture , of the disc on the left of the main going to a second floor panel


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## WronGun (Oct 18, 2013)

Hey French , 

I miss read , I understand what you mean about the metered and unmetered conductors in the Same enclosure ... I didnt realize the violation 

At the end of the day isn't it all metered though ?

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## Glock23gp (Mar 10, 2014)

frenchelectrican said:


> I came up the figures and I am pretty much hitting near 300 amp line.
> 
> 
> You denfently need 400 amp service that is the barebone size what ya got on the figures.,,
> ...


It's legit like Wron said
Up inside coinduit fed to meter outside then back into line side of disco. Follow the wires as they come up in the 2"

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## telsa (May 22, 2015)

Marc is correct.

My Poco would wig out.


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## frenchelectrican (Mar 15, 2007)

WronGun said:


> Hey French ,
> 
> I miss read , I understand what you mean about the metered and unmetered conductors in the Same enclosure ... I didnt realize the violation
> 
> ...



Ya I understand what ya try to get there.,,

but my main moot point was that big arse conduit comming up from the floor is that is unmetered and run into the big " hoffman " enclosed box in the centre.

I know., I did see the photo on other page where the " unfused / unmetered " conductors ran up from the floor to the large box then to the meter then it come back in the box and swing toward to the main fuse box on the left.

that part I was refering to that. 

but for rest of the disconnect switchs and load centre that I am not too worry about that. beside just pay attetion to the fused main switch for connection if they did use proper lugs it is fine but anything else off the spot that is a voliation there. 

this is one of few project you will have to face it hard and make sure that owner understand the situation he is facing.


Note ; please look at posting # 19 that is the photo for my comment above.


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## frenchelectrican (Mar 15, 2007)

Glock23gp said:


> It's legit like Wron said
> Up inside coinduit fed to meter outside then back into line side of disco. Follow the wires as they come up in the 2"
> 
> Sent from my SAMSUNG-SM-N910A using Tapatalk


Glock .,, I do understand what you are saying but just want to let you know most POCO will have a fit when they see metered and unmetered conductors in that large enclosere box on the wall.
( I am not worry about the meter socket itself but the large box inside that someone may come up a way to bypassed it unless the POCO tell them to put a seal or use oneway screw in there. )

WronGun .,,

Can you tell me if that conduit is 3 or 4 inch comming up from the floor ?


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## Glock23gp (Mar 10, 2014)

frenchelectrican said:


> Glock .,, I do understand what you are saying but just want to let you know most POCO will have a fit when they see metered and unmetered conductors in that large enclosere box on the wall.
> 
> WronGun .,,
> 
> Can you tell me if that conduit is 3 or 4 inch comming up from the floor ?


2" that's his dilemma.

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## frenchelectrican (Mar 15, 2007)

Glock23gp said:


> 2" that's his dilemma.
> 
> Sent from my SAMSUNG-SM-N910A using Tapatalk


*2*inch conduit .,, daymm .,, Ok now that fun just start now .,, 

coconut rum time ??

the biggest issue is the POCO conductors all it depending on where it come from if from outside then it is not too bad but if it was ran under the building that can get a headache there. 

I will let WronGun answer that question.


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## Glock23gp (Mar 10, 2014)

That's why I said another way to get 400 amps inside would be good if at all possible.

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## frenchelectrican (Mar 15, 2007)

Glock23gp said:


> That's why I said another way to get 400 amps inside would be good if at all possible.
> 
> Sent from my SAMSUNG-SM-N910A using Tapatalk


I been thinking why not boost the incomming source to 480 volts ( 200 amp ) then use the transfomer to down step back to 208 then he can get full 400 amp on 208Y120 so could kept the 2 inch conduit.


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## telsa (May 22, 2015)

frenchelectrican said:


> I been thinking why not boost the incomming source to 480 volts ( 200 amp ) then use the transfomer to down step back to 208 then he can get full 400 amp on 208Y120 so could kept the 2 inch conduit.


That WOULD be elegant. :thumbsup:

STILL, the disco would have to be 'addressed.'

I'd jerk it and replace it with a suitable MAIN C/B.

The joint needs to be re-engineered.


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## WronGun (Oct 18, 2013)

frenchelectrican said:


> *2*inch conduit .,, daymm .,, Ok now that fun just start now .,,
> 
> 
> 
> ...




This is the main concern I brought up to the Owners , that 2" pipe run needs to be traced... the panels are located at the very back of the building

As you can see if this was ran from the front we have a big problem 

At this point I can see how 480V with a Tformer may be our only option 












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## frenchelectrican (Mar 15, 2007)

WronGun said:


> This is the main concern I brought up to the Owners , that 2" pipe run needs to be traced... the panels are located at the very back of the building
> 
> As you can see if this was ran from the front we have a big problem
> 
> At this point I can see how 480V with a Tformer may be our only option


It don't matter which way the uility run from.,, there is always a solution for that.

But yes please do trace that uility conductors and see where it do run so you can able figure out where it run and may ran to the transfomer pad or to the pole in the back if latter you may get lucky depending on the distance from that location to the uility source useally either pad or pole depending on how it strung. 

but if you going to use the transfomer route the transfomer size for that size of useage you will need at least 150 Kva transfomer that is kinda common item but little lead time to find it.


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## WronGun (Oct 18, 2013)

frenchelectrican said:


> It don't matter which way the uility run from.,, there is always a solution for that.
> 
> 
> 
> ...




I will definitely be checking with the inspector about all of this .... I don't recall ever installing transformers outside of enclosed electrical rooms within a building 

Regardless I'm going to first see if I can bring something in overhead 

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## telsa (May 22, 2015)

That Service Lateral pipe has to terminate underneath some ( pad mounted?) Poco transformer... or run up some pole.

75kVA Poco pad mount trannys are pretty common, and would be expected if this is a free standing building.

In which case, the Poco could swap it out ( for $$$ ) to give you your 480Y277.

&&&

The big can needs to be transformed into a CT cabinet, with the meter left as is. (to Poco standards)

The fused disconnecting switch has to go entirely, perhaps re-used on the secondaries of your 480 to 208Y120 transformer. ( Mount it directly to the transformer body -- on the side. ) This space then would permit a 200A 208Y120 MLO panel. (It could even be the existing one, which will have to come off the wall to be remounted. Its space is needed for the 200A 480Y277 MAIN panel.)

You could go with twin 75kVA transformers off of the new 200A 480Y277 MAIN panel.

Twin 200A 208Y120 panels would give you plenty of breaker spaces. One of those panels could be the existing one, moved over and re-mounted.

The new MAIN panel would have a MAIN C/B... and could power lighting circuits at 277VAC, etc.

75kVA transformers are small enough that it's often practical to mount them directly overhead on some frame that is also secured to the wall. CBU is usually too weak to hold them without auxiliary steel framing.

Also consider setting a gutter, below the transformers and above the panels, so that you can pick up all of the old EMT runs cleanly and quickly.

The above scheme would let you re-use components and not hog up too much space.


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## frenchelectrican (Mar 15, 2007)

WronGun said:


> I will definitely be checking with the inspector about all of this .... I don't recall ever installing transformers outside of enclosed electrical rooms within a building


I have done that pretty often by installing the transfomer outside of electrical room espcally with very large area.

serveal reason why I do that is I can bring 480 volts circuits further and use the transfomer to branch out the local circuits as it need to be.

and yes Tesla did bring up few good points and I done simuair way what he is describing. 



WronGun said:


> Regardless I'm going to first see if I can bring something in overhead


Try to see you can bring it in overhead if possible if overhead clearance is there otherwise run a new lateral run with much larger size . something sized at least 600 amp 208Y120 volts otherwise bring in 600 amp 480 volts service then use the transfomers as it need to be. 

Note some of the kitchen equiment some can switch over to 480 volts ., if so I would go that route if possible espcally with high power hogs units. 

Keep us posted on the progress what ya got there.


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## Signal1 (Feb 10, 2016)

WronGun said:


> I will definitely be checking with the inspector about all of this .... I don't recall ever installing transformers outside of enclosed electrical rooms within a building
> 
> Regardless I'm going to first see if I can bring something in overhead
> 
> Sent from my iPhone using Tapatalk


I've done this in shopping malls all over New England, right on the stockroom floor of the tenant space.



frenchelectrican said:


> Note some of the kitchen equiment some can switch over to 480 volts ., if so I would go that route if possible espcally with high power hogs units.


This is a great point. Does your customer own this stuff already? If not maybe they could look at getting more 480V equipment.


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## WronGun (Oct 18, 2013)

Signal1 said:


> I've done this in shopping malls all over New England, right on the stockroom floor of the tenant space.
> 
> 
> 
> ...




Yes , they do own the equipment all
Of which is 120, 240, and 208. 

I will start to draw this out as soon as I get more info. Ive spent the last 11-12 yrs following prints, so putting this together will be new to me. 

I highly doubt they expected this , and I'm sure they signed the lease without ever thinking if they have enough power. 


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## frenchelectrican (Mar 15, 2007)

WronGun said:


> Yes , they do own the equipment all
> Of which is 120, 240, and 208.
> 
> I will start to draw this out as soon as I get more info. Ive spent the last 11-12 yrs following prints, so putting this together will be new to me.
> ...


I would go with Wye system for very obvous reason.,, but try to come up couple alterante plans so if the POCO and cost is not too bad I will use the latter route and use that for expandision so that way the customer dont have to heavy up twice on the dammed service. ( trust me on that some customer found out in hard way ) 

That is very common with alot of customers signed in the lease and not really relaized about the service size that useally bite their butt pretty hard if they are not aware of it.


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## telsa (May 22, 2015)

Once they see the tab, don't be too surprised if they back out of the lease.


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## WronGun (Oct 18, 2013)

telsa said:


> Once they see the tab, don't be too surprised if they back out of the lease.




I will not be surprised. Unfortunately, they have already done so much work in the office areas. Their options are limited 


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