Space heater breaker size

Status
Not open for further replies.
H

hhsting

Senior Member
Location
Glen bunie, md, us
Occupation
Junior plan reviewer
I have 10kva 208V three phase unit space heater. This is Not baseboard heater and its mounted on ceiling.

One dedicated branch circuit breaker size to the unit heater provided is 40A with 3#8 + 1#10G branch circuit cable size.

I cited NEC 2014 section 424.3 breaker size too big but I got response that 40A with #8 cable size is in compliance with 424.3.

I am not sure is 40A breaker size with #8 cable size for 10kva 208V three phase unit heater in compliance with 424.3 or not? What are your thoughts?
 
What part of 424.3 do you feel does not allow the 40 amp circuit. Please read the entire paragraph.

What size circuit do you feel should be installed for this heater? Do the calc's.
 
I see nothing in 424.3 that would prohibit it.

424.3 Branch Circuits.
(A) Branch-Circuit Requirements. Individual branch circuits
shall be permitted to supply any volt-ampere or wattage rating
of fixed electric space-heating equipment for which they are
rated.
Branch circuits supplying two or more outlets for fixed electric
space-heating equipment shall be rated not over
30 amperes. In other than a dwelling unit, fixed infrared heating
equipment shall be permitted to be supplied from branch
circuits rated not over 50 amperes.
(B) Branch-Circuit Sizing. Fixed electric space-heating equipment
and motors shall be considered continuous load.
Click to expand...
 
Check the manufacturers instructions 110.3(B) and 422.11(A), they will usually have a breaker table.
I find this is almost always the case. I have been installing lots of outdoor seating heaters and ordering lots of 35 A breakers...
If not then 422.11(E)(3)
10kW @208 3 phase = 27 Amps X 1.5 = 41 amps
 
tortuga said:
Check the manufacturers instructions 110.3(B) and 422.11(A), they will usually have a breaker table.
I find this is almost always the case. I have been installing lots of outdoor seating heaters and ordering lots of 35 A breakers...
If not then 422.11(E)(3)
10kW @208 3 phase = 27 Amps X 1.5 = 41 amps
Click to expand...

Are space heater covered by 422 or 424?


Sent from my iPhone using Tapatalk
 
Appliance. Utilization equipment, generally other than industrial,
that is normally built in standardized sizes or types and is
installed or connected as a unit to perform one or more functions
such as clothes washing, air-conditioning, food mixing, deep
frying, and so forth.
Click to expand...
 
Review your Manufacturer's specification / installation instruction. Looking at 2020NEC, 424.3 has nothing to do with your situation. 424.4 has no restriction if you are using a dedicated circuit, "...shall be permitted to supply any volt-ampere or wattage rating of fixed electrical space-heating equipment for which the branch circuit is rated."

If you don't have a spec sheet, see if there is a name plate.
 
The last part just says "and so forth.."
Surely you think a heater is a piece of equipment no?

Equipment. A general term, including fittings, devices,
appliances, luminaires, apparatus, machinery, and the like used as a
part of, or in connection with, an electrical installation. (CMP-1)
Click to expand...
 
I agree with Post 2, 3 & 7 & 10
10kw continuous load puts you right at 35 amps and I would guess this heater may have a blower to take into consideration + it should have a nameplate.
I see nothing that would substantiate your thoughts that a 40 amp breaker was too big.
 
augie47 said:
I agree with Post 2, 3 & 7 & 10
10kw continuous load puts you right at 35 amps and I would guess this heater may have a blower to take into consideration + it should have a nameplate.
I see nothing that would substantiate your thoughts that a 40 amp breaker was too big.
Click to expand...
Going with that logic it could be on a 50.
 
hhsting said:
35A breaker size.
Click to expand...
W
augie47 said:
I agree with Post 2, 3 & 7 & 10
10kw continuous load puts you right at 35 amps and I would guess this heater may have a blower to take into consideration + it should have a nameplate.
I see nothing that would substantiate your thoughts that a 40 amp breaker was too big.
Click to expand...
I agree that 35 is a standard size and would work, but I see no requirement that you use the smallest standard size. Where are you getting that from 424.3 hhsting???
 
Were long past the 35 amp breaker..
He got his answer and probably wont be back on this thread.
Regardless if one thinks a heater is equipment that utilizes electricity or not
If the manufacturer does not specify a max OCPD they could use a 40.
 
electrofelon said:
W

I agree that 35 is a standard size and would work, but I see no requirement that you use the smallest standard size. Where are you getting that from 424.3 hhsting???
Click to expand...
Unless it has a blower that draws three tenths amps or less I think the minimum conductor ampacity will be over 35 and minimum OCPD therefore is going to be at least 40.
 
There is 150% limit on branch circuit size in 422.10(E)(3) Not seeing similar wording in art 424. See this applied to water heaters maybe more than about anything else, which is why you almost always see 4500 watt WH on 30 amp circuit, otherwise if limited to 125% they would need to be on a 25 amp circuit.

424.22(B) possibly lets you run up to 60 amp overcurrent protection here with OP's space heater? Of course you would need at least 51 minimum ampacity conductor in that case. I don't see why you couldn't protect 75C #8 with up to a 50 amp breaker though.
 
kwired said:
Unless it has a blower that draws three tenths amps or less I think the minimum conductor ampacity will be over 35 and minimum OCPD therefore is going to be at least 40.
Click to expand...
Sure, whatever, I don't disagree. But the point was to try to understand how/why the OP thought what he did from that section. Ya know, the old "give a man a fish you feed him for a day. Teach a man to fish and you feed him for a lifetime" thing.
 
Status
Not open for further replies.
Top