Voltage Drop for Spa Installation

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sean1

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Customer wants to move his spa; here is my problem:
Existing spa is apprx. 80 feet form panel, fed by a 50 amp circuit with #6 conductors. Customer wants to relocate spa approx. 110 from existing location. Existing conduit and panel location doesn't allow me to upgrade my wire size to #4. My concern is voltage drop. If I put a breaker panel where the existing spa disconnect is, and add 110 feet of conduit and #6 wire, will this eliminate my voltage drop problem, or does my voltage drop calculation start from the original sub-panel?
 

catchtwentytwo

Senior Member
sean1 said:
Customer wants to move his spa; here is my problem:
Existing spa is apprx. 80 feet form panel, fed by a 50 amp circuit with #6 conductors. Customer wants to relocate spa approx. 110 from existing location. Existing conduit and panel location doesn't allow me to upgrade my wire size to #4. My concern is voltage drop. If I put a breaker panel where the existing spa disconnect is, and add 110 feet of conduit and #6 wire, will this eliminate my voltage drop problem, or does my voltage drop calculation start from the original sub-panel?

You could increase the wire size for the 110 foot extension. Before you do that, what is the voltage at the present location, taken with it running? What is the manufacturer's specfication.

You could always use a Buck-Boost Transformer? http://www.solaheviduty.com/products/transformers/BuckBoost/index.html
 

ramsy

Roger Ruhle dba NoFixNoPay
Location
LA basin, CA
Occupation
Service Electrician 2020 NEC
Using Electrical Designer's Reference (EDR) a 120vac nominal should be at most 118vac at the existing spa disconnect 80ft away, running at 49A, PF=1. The voltage boost between PF=1 and PF=0.85 is less than 1 volt over 190 feet.

Single phase motors usually run at 115/230, so if the spa nominal runs at 115vac, extending that #6cu to 190 total feet, EDR shows the spa-pump motor target at 111vac, for a total 9% V-Drop. Using two #8cu in parallel, a total of four #8cu, for that 110.ft section will boost one volt more than #6 by itself.

If the spa load could be set to 230vac, fed with 240 nominal, the same 9.12 volts dropped on one #6cu is only 3.8% of 240, or 231vac, 190 feet away. Any risk of pump motor heating from undervoltage could be eliminated.
 

iwire

Moderator
Staff member
Location
Massachusetts
catchtwentytwo said:
You could always use a Buck-Boost Transformer?

Not really a good solution for voltage drop issues.

Unless the load is constant the voltage will be up and down as the load changes.
 

ramsy

Roger Ruhle dba NoFixNoPay
Location
LA basin, CA
Occupation
Service Electrician 2020 NEC
iwire said:
That is an NEC violation.
If terminals are listed or designed for a single conductor only, or smaller conductor than needed for your voltage drop, one legal method is pigtailing the different sizes with an appropriate wire nut or splice. Another legal method is pin terminal adaptors, if your sizes are available. You may have heard of Polaris connectors, www.nsiindustries.com

Using either method to terminate two paralleled #8cu or #6AL doesn't really help much, but then neither does a single #4cu, at 2 volts more than a single #6cu over that 110.ft length.

Paralleling two #6cu over 110.ft boosts 2.7 volts more than a single #6cu, which is closer, but still short of a 115vac target over the 190 foot total.

You might use EDR's segmented v-drop calculator yourself, to make sure these figures are correct, before recommending anything to your client. Free download here http://www.edreference.com/
 

iwire

Moderator
Staff member
Location
Massachusetts
ramsy said:
If terminals are listed or designed for a single conductor only, or smaller conductor than needed for your voltage drop, one legal method is pigtailing the different sizes with an appropriate wire nut or splice.

Roger in this application none of the above suggestions will make it NEC complaint.

In general 310.4 prohibits conductors smaller than 1/0 in parallel.
 

infinity

Moderator
Staff member
Location
New Jersey
Occupation
Journeyman Electrician
Bob's problem with paralleling # 8 conductors is not with the terminations, it's with the violation of 310.4 that it would create.

310.4 Conductors in Parallel.
Aluminum, copper-clad aluminum, or copper conductors of size 1/0 AWG and larger, comprising each phase, polarity, neutral, or grounded circuit conductor, shall be permitted to be connected in parallel (electrically joined at both ends).
 

ramsy

Roger Ruhle dba NoFixNoPay
Location
LA basin, CA
Occupation
Service Electrician 2020 NEC
Thanks guys. I guess you'ld have to be in an elevator, or using 400Hz motors to get away with this, 310.4 Ex. 1 & 3.
 

sean1

Member
Spa Relocation Additional Information

Spa Relocation Additional Information

Per some of your suggestions, I went back and took what readings were possible. The spa has already been disconnected, so it is not possible for me to get my readings under load. However, at the disconnect that is located apprx. 80 feet from the panel, the reading is 240 volts (Existing wiring is 2 #6 hot conductors, 1 #8 neutral and 1 #10 ground), the name plate on the equipment required 240 volt, 40 amp, fed by a 50 amp circuit. My new question is, if I put a NEMA 3R enclosure at the end of the original 80 foot run, with 2 #4 copper conductors, 1 #6 neutral and 1 #10 ground, from the junction box to the new location of the spa, will this satisfy and voltage drop?
Thanks
 

George Stolz

Moderator
Staff member
Location
Windsor, CO NEC: 2017
Occupation
Service Manager
I'm with Trevor on this one. I'd use a #6 CU for the 110' run. Overall your voltage drop wouldn't be bad at all at that distance.

Plus, you could use a #10 EGC if you stayed with the #6 ungrounded conductors on the 50A circuit.

If you upsize more to a #4 ungrounded conductor, you would need a #8 grounding conductor. :)
 

ramsy

Roger Ruhle dba NoFixNoPay
Location
LA basin, CA
Occupation
Service Electrician 2020 NEC
If the spa pump motor nameplate expects 230vac, I'm with Trevor also, since 240 drops to 236vac with a balanced 40 amps over 190.feet away on #6cu.
 
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sean1

Member
Spa Relocation Additional Information

Spa Relocation Additional Information

Spa motor plate does read 230 volts, 1 hp, but heart element plate reads 240 volts at 5.5 amps. Do you and Trevor agree that #6 is still sufficient?
 

catchtwentytwo

Senior Member
georgestolz said:
If you upsize more to a #4 ungrounded conductor, you would need a #8 grounding conductor.
The grounding conductor size is based on the maximum overcurrent device size not conductor size (250.122). A #10 awg is good for up to 60 amps.
 

iwire

Moderator
Staff member
Location
Massachusetts
catchtwentytwo said:
The grounding conductor size is based on the maximum overcurrent device size not conductor size (250.122). A #10 awg is good for up to 60 amps.

Yes....and no.

Check out 250.122(B) it requires the EGC to be increased in size when the circuit conductors are over sized.

If for example you happen to run 6 AWG for any reason (voltage drop, it's what you had, etc.) for a 20 amp branch circuit the EGC would be required to be 6 AWG as well
 
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