Know it all customer!!

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wayne123

Senior Member
Location
North Carolina
I have just recently quoted wiring for a boathouse. The customer was pretty satisfied with the layout that I came up with except for the price of a feeder. To fill you in a bit more this boathouse will have about a 40 amp load on it ( 2 boatlifts, water heater, 2 battery chargers, refrigerator,ceiling fans(3),4 flourescent fixtures over the two boat slips and some floodlights and some gen purpose recept).The feeder will be fed from a saw service which will be permanent for campers. Anyway the feed will be a bit over 300ft. amp sized for 60 amps so i did a voltage drop calc. and came up with #2 cu feeder 240 volts with a neut. and a ground. She told me that there is no way she needed a feeder that big to feed it so she went to a jack leg electrician and he told her that #6/2 will work just fine. I told her that if thats what she wanted then get someone else to do the job for her. She didn't understand why I turned down the job and I told her that when I do a job I do it like I would be doing it for myself, THE RIGHT WAY!! thinking about sending her a bill for the quote because the job is about an hour and a half away from my shop.Man do I feel better getting that off my chest! Thanks for listening! May her lights blink and refrigerator compressor burn up due to low voltage!!!
 
Re: Know it all customer!!

Let him deal with the problem when she starts burning out motors.I think maybe i would have priced it in alum to cut cost with option of copper.Might go along with him if it was 6-3 and balanced some loads.I have seen some of them boat houses,no telling what will be added.TV,MICRO,COOKING,ETC
 
Re: Know it all customer!!

What I like to do when trying to sell the issue of voltage drop, is to show the numbers in dollars. People don't understand or don't care about voltage drop. They do care about their electric bill.

Take your example above:

A 40A load on #6 at 300-ft. will be at about 11.8 VD. That is about 472 watt losses alone. (I^2xR)

The same 40A load on your suggested #2 at 300-ft. will be about 188 watt losses alone.

Put those numbers into a standard power cost formula and you will find that the #6 installation will cost the owner $3.00 a month verses the #2 installation of only $1.18 per monthy. This is figuring only 3 hours of operation a day at 7 cents a kW/hr. This is only power losses on the conductors. Figure in the total load and equipment failure or misoperation from the voltage drop and the numbers climb even higher.

Bascially, its like turning on 4, 100-watt light bulbs in a closet and shutting the door. Doesn't make sense literally and financially. :)
 
Re: Know it all customer!!

It is not as simple as that to figure the loss.

Any power lost to heating the wire is power not getting to the utilization equipment.

But the power used ends up the same.

Of course you still paying for electricity that is not doing the work you want it to.
 
Re: Know it all customer!!

wayne123, not that I disagree with you voltage drop theory, but you might of wanted to consider a # 4 AWG. The reason I say this is what is the possibility of the service pulling the load you calculated. I assumed you used 80% of the breaker. Doubtfull that load would ever be developed for any length of time. Just a thought.
 
Re: Know it all customer!!

I agree with Dereck. I did a quick calculation myself and the #4 is adequate for a 40 amp load at 3% max voltage drop.

Bryan, I'm curious as to how you arrived at your numbers. I calculated a 230 watt loss with the #6 and a 91 watt loss with the #2.
 
Re: Know it all customer!!

2 x 12.9 x 300 x 40 / 26240 = 11.8 vd x 40A = 472-watts. Or I^2 x R, 40 x 40 x .2946 = 472-watts (the .2946 is the R of #6 at 600')

I then performe the same above for the #2. :)
 
Re: Know it all customer!!

Wayne123 just a follow up. I ran some numbers using a modified formula I have developed over some years of collecting test data. It is the standard formula of CM=(K * I * 2 * D)/VD. The change I have made is changing the value of K from 12.9 to as low as 10. In my example I use 11.1. I have found 11.1 to still be conservative, so you can even go lower if budget pressures are an issue. So the modified formula I use is:

CM = (22.2 * I * D) / VD

Where:
CM = Circular Mills
I = Max load current in amps
D = One-Way distance in feet.
VD = Desired voltage drop

Assuming these values
I = 40-amps
D = 300-feet one-way distance
240-volt supply

4.2% VD @ 6 AWG
2.6% VD @ 4 AWG
1.6% VD @ 2 AWG

IMHO a 6 AWG would have been adequate. I base that on I doubt you would ever see a full 40-amp load. And even if you did, none of the equipment listed is sensitive load and should not be effected.

As to the energy usage sales pitch is a little mis-leading IMO. True the higher resistance burns more heat, but the overall circuit will use less power. Use a 60 watt light bulb as an example. First figure the actual load considering a super conductor. Naturally you consume 60 watts total power. Now throw in 1 ohm resistance in each leg (P & N) for a total of 2 ohms conductor resistance. What is the total power consumed? 59.5 Watts.
 
Re: Know it all customer!!

Originally posted by dereckbc:
Use a 60 watt light bulb as an example. First figure the actual load considering a super conductor. Naturally you consume 60 watts total power. Now throw in 1 ohm resistance in each leg (P & N) for a total of 2 ohms conductor resistance. What is the total power consumed? 59.5 Watts.
Click to expand...
Dereck I thought the total power would be the same.

In your example I thought we would have 59.5 watts to the lamp and .5 watts wasted heating the cable for a total of 60?

Bob

[ June 03, 2004, 04:53 AM: Message edited by: iwire ]
 
Re: Know it all customer!!

Thanks for the replies. I forgot that there will be small kitchen in the boathouse and there will be a microwave and a large beer cooler and also I am getting my figures from the 60 degree column in 310.16 because I am using UF. I did price aluminum for the job but all the supply houses in my area only had 250' rolls of 2/0, running single cables in pvc would have been more expensive. I probably could have gotten away with # 4cu after I thought about it and read your replies. I just feel that the #2 cu will be a better choice in order to alieviate the voltage drop and make sure that possible future loads wouldn't be a problem.
 
Re: Know it all customer!!

Bob not for a resistive load, just plain old Ohm's law. A 60 watt light bulb is 240 ohms. Add 2 more and you get 242 for the circuit. 242 ohms @ 120 is 59.5 watts consumed by the circuit. 59 watts for the light, and .5 for the wire.
 
Re: Know it all customer!!

Originally posted by jimwalker:
Let him deal with the problem when she starts burning out motors.I think maybe i would have priced it in alum to cut cost with option of copper.Might go along with him if it was 6-3 and balanced some loads.I have seen some of them boat houses,no telling what will be added.TV,MICRO,COOKING,ETC
Click to expand...
I agree with Jim...if she finds herself burnt to a crisp, then she'll come back asking for help. Curse you Home Depot, for your DIY classes!!! :)
 
Re: Know it all customer!!

Wayne, how did you get on the subject of voltage drop with the customer in the first place. When I price a project, its based on my experience to do the job. Sometimes you can talk yourself out of the job, by providing too much tech information. Not to mention lets see if her jack leg can file the job!
 
Re: Know it all customer!!

Megawire, she wanted to buy all the material herself so there wouldn't be any markup. This was fine with me because I raised my hourly rate to compensate for it. I gave her a list of the material and off she went, I thought, to go and pick it up. Well she decided to stop by her so called plumber/HVAC/poolboy/carpenter/roofer/electrician friends house so he could look over the material list for her and he decided thet the feeder was too large and that he could save her money by using a smaller size.And the story goes on and on.When I called her to see if she was ready for me to get started she told me the story and told me that jack leg was going to do the job instead of me. By the way I got all this info from one of our mutual friends. Hope she gets what she pays for.
 
Re: Know it all customer!!

... I gave her a list of the material

That was your first mistake. A red flag should have gone up as soon as you found out that your customer was too cheap to pay your regular rates and for the material. You just fed into it by allowing her to purchase the material. From where? How do you know she will get it right? You are the electrician YOU purchase the materials.

So, if you walked away in the beginning like you should have you would have lost the job. Now you not only lost the job but it is costing you!

-Hal
 
Re: Know it all customer!!

I agree with you all wholeheartedly about my stupidity in giving her the list. I can remember that there was a thread here somewhere that says....DON"T TRUST ANYONE..... Thats my new moto. I live in a small community south of Greensboro where most people are honest and thats just the way I was brought up to be. I have a full time job and operate a small contracting business on the side so it's not going to hurt me real bad to loose a job or two, it's just the principle of the matter.
 
Re: Know it all customer!!

What does giving the list of materials to a customer have to do with trust? Did you tell the customer not to share the list with any other contractor? Did the customer promise not to share the list?

The customer did nothing wrong by sharing your list with another contractor. She was merely trying to make sure that you were giving her a fair and correct quote.

It is drilled into people's heads to get more than one quote when planning to hire someone for a job, whether it be roofing, painting, an addition to a house, or electrical work, at least when the work is substantial. The customer is using your mistake to her advantage, probably without even fully understanding that you made a mistake or that perhaps she shouldn't be sharing your information without your permission.

Now the customer has conflicting information, and needs further clarification. Here is where you come back in the picture, at least if you want to, which it doesn;t sound like you want to do. You need to convince the customer that you are correct and the other electrician is incorrect. Perhaps you need to suggest that she get a third estimate for the job, this time without sharing your list of materials, specifically asking about the wire size.

In this case I personally think that the customer should have waited to see what the other electrician proposed and then made comparisons, specifically asking about such things as feeder wire size, subpanel size, etc. But that is not relevant at this point.
 
Re: Know it all customer!!

EE Bob:

Of course this is basically "bid shopping". And we all know thats not really fair. If you show contractor A's bid to contractor B, B will beat A's number 9 out of 10 times. And if you take A's material list to B, that's even worse.

Of course, the homeowner hasn't thought about any of this (and she probably wouldn't care if she did), she is just trying to get the cheapest price. So don't stop trusting everyone Wayne, just be a little more careful who you trust, don't hand out any more material lists, and realize not everyone is playing by the same rules.

Steve
 
Re: Know it all customer!!

I agree with racraft and steve66. The moral of the story is not to become the customer's set-up man. Some of the best lessons learned are ones that cost $.
 
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