# 10 current carring at continuos load

[irelandnewyork]

Hi Guys'
I have an installation where i have to supply power to 2 devices which will use 18 amps each continuous i am going to pull 6 #10s (it is 3 phase) and 2 #10 grds in 3/4 emt. The terms are rated 75c can i breaker this at 30 amps ?
Am i right in thinking # 10 rated 40amps ie 90c col x .8 for 4-6 cccs = 32 so can be protected at 30 amp breakers.
And continuous use 18 amps x 1.25 = 22.5 so a 25 amp or 30 amp breaker will work. Thanks for the help

IrelandNewYork

 

[mike1061]

The EMT pipe should do for the ground conductor. Do you need to pull a seperate ground for some reason?
Thanks
Mike

 

[suemarkp]

What are the devices you're powering, and are they hard wired? You can only use so large of a circuit to power an appliance. GEnerally, you're limited to 150% of nameplate unless there is a "max breaker" listed on the appliance. So a 18A nameplate * 150% = 27A. You can round up to 30A, so a 30A circuit is the largest you can use to power this.

Depending on what the unit is, you could use #12 wire (it is rated at 25A at 75C, but need to watch 240.4(D)). Should have no issue at all with #10.

 

[irelandnewyork]

The devices require a seperate grd for each circuit they are actually DC rectifiers they are not hard wired as such 100' of pipe from the panels to each unit then 2' liquidtight flex from end of pipe run to the unit itself.
They are considered 125% cont use nameplate rating is 25 amps so i just want to know can i fit 30 amp breakers ?

 

[Dennis Alwon]

The devices require a seperate grd for each circuit they are actually DC rectifiers they are not hard wired as such 100' of pipe from the panels to each unit then 2' liquidtight flex from end of pipe run to the unit itself.
They are considered 125% cont use nameplate rating is 25 amps so i just want to know can i fit 30 amp breakers ?

Yes #10 is sufficient assuming no other de-rating

 

[irelandnewyork]

Its not the cable size thats the problem its the breakers can they be 25 or 30 amp ?

 

[bob]

You are using a conductor rated at 30 amps. Yet you seemed to be concerned with using a 30 amp breaker for some reason.

Is there something else you want to tell us . You followed the NEC rules right to the end. I see no problerm.

 

[infinity]

This might apply:

422.11 Overcurrent Protection. Appliances shall be pro-
tected against overcurrent in accordance with 422.11(A)
through (G) and 422.10.
(A) Branch-Circuit Overcurrent Protection. Branch cir-
cuits shall be protected in accordance with 240.4.
If a protective device rating is marked on an appliance,
the branch-circuit overcurrent device rating shall not ex-
ceed the protective device rating marked on the appliance.
(B) Household-Type Appliances with Surface Heating
Elements. Household-type appliances with surface heating
elements having a maximum demand of more than 60 am-
peres calculated in accordance with Table 220.55 shall have
their power supply subdivided into two or more circuits,
each of which shall be provided with overcurrent protection
rated at not over 50 amperes.
(C) Infrared Lamp Commercial and Industrial Heating
Appliances. Infrared lamp commercial and industrial heat-
ing appliances shall have overcurrent protection not ex-
ceeding 50 amperes.
(D) Open-Coil or Exposed Sheathed-Coil Types of Sur-
face Heating Elements in Commercial-Type Heating
Appliances. Open-coil or exposed sheathed-coil types of
surface heating elements in commercial-type heating appli-
ances shall be protected by overcurrent protective devices
rated at not over 50 amperes.
(E) Single Non?motor-Operated Appliance. If the branch
circuit supplies a single non?motor-operated appliance,
the rating of overcurrent protection shall comply with the
following:
(1) Not exceed that marked on the appliance.
(2) Not exceed 20 amperes if the overcurrent protection
rating is not marked and the appliance is rated
13.3 amperes or less; or
(3) Not exceed 150 percent of the appliance rated current if
the overcurrent protection rating is not marked and the
appliance is rated over 13.3 amperes. Where 150 per-
cent of the appliance rating does not correspond to a
standard overcurrent device ampere rating, the next
higher standard rating shall be permitted.

 

[kwired]

The devices require a seperate grd for each circuit they are actually DC rectifiers they are not hard wired as such 100' of pipe from the panels to each unit then 2' liquidtight flex from end of pipe run to the unit itself.
They are considered 125% cont use nameplate rating is 25 amps so i just want to know can i fit 30 amp breakers ?

"Hardwired" is not an NEC term, but is generally used in the trade to mean permanently connected vs cord and plug, or other easily separable connections by the users being used. Your flexible conduit connected equipment is usually considered hard wired.

 

[infinity]

Its not the cable size thats the problem its the breakers can they be 25 or 30 amp ?

BTW, this was answered by Mark in post #3.