How Long before i go to a bigger wire?

Status
Not open for further replies.

spaman

Member
A hot tub/spa
Running 50Amp service
The guy wired it with 8 gauge wire, we told him because of the length of the run, over 100ft. that he would need to go to 6 wire to carry the load that far.

any answers for me?
 
Re: How Long before i go to a bigger wire?

No. 6 would not be required for voltage drop. Loss is about 3% for 50A in 100ft. for No.8. However unless terminations at both ends are rated for 75C, No. 6 would have to be used. I am assuming this is a 240V circuit.

[ October 21, 2004, 08:18 PM: Message edited by: electricman2 ]
 
Re: How Long before i go to a bigger wire?

Actually, it could be close to being acceptable. I can?t be sure without more information.

First of all, the size of the service is not relevant. I would need to know how much load the equipment draws. Next, I would need to know whether the equipment is fed at 120 volts or 240 volts. Finally, being ?over 100 feet? is not enough detail.

Just for an example, if the run is exactly 100 feet, and the equipment is fed at 240 volts, and if the load is 45 amps, then a #8 gives you a reasonable voltage drop of 3%.
 
Re: How Long before i go to a bigger wire?

50 amp is the OCPD not the load, voltage drop will be even less of an issue when calculated using the actual load.
 
Re: How Long before i go to a bigger wire?

This is the set up,

The spa contains 2 240v 2 speed motors 5000watt heater and 12v tranformer for light.
The motors are 4.5 hp..not sure of the amp draw.

The wire is run in plastic conduit and the 100ft is approx. its more or lees in that range.

I was under the assumption that in that long a distance that the amp would drop lower than needed to accomidate both motors and the heater running under full load.
 
Re: How Long before i go to a bigger wire?

Length and load both effect voltage drop.

CharlieB took a educated guess that the load on the 50 amp breaker would not be more than 45 amps, at that load voltage drop is not a problem for 100' of 8 AWG.


Two 240 volt 4.5 hp motors?

Are you sure as those would draw about 30 amps each along with 21 amps of heat.

I doubt you have 81 + amps of load on a 50 amp breaker. ;)
 
Re: How Long before i go to a bigger wire?

Positive on the 2 4.5hp motors..thats one of our selling points...also positive on the 240v..and the only require 50 amp breakers
 
Re: How Long before i go to a bigger wire?

Interested in this also, as I am running a spa 50a GFI feed to my new hot tub.

Please read the next post. I have edited out your question. Sorry, you need to go to another site for specific DIY information. I highly recommend that you get a qualified electrical contractor to do work around a spa or hot tub to keep from electrocuting someone. Charlie

[ November 12, 2004, 01:30 PM: Message edited by: charlie ]
 
Re: How Long before i go to a bigger wire?

Scuba_Dave

This NEC? Forum is for those in the electrical and related industries.
Questions of a "How-To" nature by persons not involved in the electrical industry will be removed without notice.
Please read our rules and disclaimers.
 
Re: How Long before i go to a bigger wire?

Spaman

Something doesn't seem to add up. 4.5 isn't a standard size in Table 430.148, but if you use the value for a 5 hp motor, the flc is 28 amps. The heater draws 21 amps so you would have a demand load of 28x1.25+28+21=84 amps, too much for a 50 amp breaker.
The second problem especially with #8 is that depending on the lugs you land on at the spa, you can only rate #8 at 40 amps. The general rule for reading the tables in Article 310 is spelled out in 110.14C, breakers and equipment rated at 100 amps or less shall be wired with conductors whose ampacity is based on the 60 degree column. Exceptions allow for the 75 degree column if all terminations are rated for 75 degrees. You must check this before you use the 75 degree column.
 
Re: How Long before i go to a bigger wire?

Sorry for posting on this board, with 20 years experience, I thought your Home page welcomed those involved & experienced:

This site is designed for:
Contractors
Electricians
Engineers
Inspectors
Instructors
Other electrically related individuals

and I've had too many experts do a terrrible under spec job to trust them. Which is why I opted long ago to eduacte myself & do my own work.
Just never finished that engineer degree.

My apaologies
 
Re: How Long before i go to a bigger wire?

In regard to 4.5HP motors. I've found in recent years that the advertised HP for motors be it air compressors, pool,spa pumps, etc seem to be governed by some mysterious advertising gimic that maximizes rated HP. Hence swimming pool pumps darwing 10 amps @ 120V are rated at 1 HP. (Some term called developed HP)

What we need is actual loads in amperes to determine the REAL HP and then we can figure out voltage drops and wire size.
 
Re: How Long before i go to a bigger wire?

Posted by stanley: seem to be governed by some mysterious advertising gimic
The figures that sometimes can be found in the promotional literature associated with a product seem to come from alternate universes.

I was involved with a shop vac comparison article, and tried to get the manufacturer's motor specs. One manufacturer made no attempt to acknowledge a motor nameplate rating of HP, Volts, Full Load Amps, etc., rather, the manufacturer claimed the motor developed 135 Air Watts of suction. :confused:
 
Status
Not open for further replies.
Top