208 single phase electric furnace

Status
Not open for further replies.
R

ronball

Senior Member
Location
Champaign Il.
Occupation
Electric Contractor
Does an electric furnace require a neutral or not. Rated for 60 amp circuit.
planning on using 6/2 romex. I don't belive it requires neut.
 
ronball said:
Does an electric furnace require a neutral or not. Rated for 60 amp circuit.
planning on using 6/2 romex. I don't belive it requires neut.
Click to expand...

I have never seen one require a neutral but are you sure it is 208V single phase and not 240V
 
6/2 nm may not be large enough. Many of the electric heaters are rated 10kw and have a minimum cir. amp. of 56. NM must be rated at 60C-- only 55 amps for #6. If it truly is 208V then it probably won't be over 55 amps but check.
 
voltage

voltage

incoming voltage is 120/208 three phase/apartment complex. 120/208 single phase out to each unit. furnaces were rated at 11kw. I figured this to be around 53 amps.
 
ronball said:
incoming voltage is 120/208 three phase/apartment complex. 120/208 single phase out to each unit. furnaces were rated at 11kw. I figured this to be around 53 amps.
Click to expand...
Check the nameplate. You don't know the size of the blower and it may take you over 55 amps.
 
I don't know of any that require a neutral. I would check on the 11kw. Some manufacturers are calling their 9.8kw@240v strips 11kw or it could be a 15 kw@240v(14.4kw) strip that would be about 11kw@208v. If it is 11kw@208 the unit should have a 60 amp breaker and a 30 amp breaker.
 
Mgraw said:
I don't know of any that require a neutral. I would check on the 11kw. Some manufacturers are calling their 9.8kw@240v strips 11kw or it could be a 15 kw@240v(14.4kw) strip that would be about 11kw@208v. If it is 11kw@208 the unit should have a 60 amp breaker and a 30 amp breaker.
Click to expand...
I think you mean if its a 15kw unit.

If this unit is truly a 208 unit and 11kw then you get 53 amps but then you need to multiply by 125% to get the ampacity of the circuit. That means you need a conductor for 66 amps-- this means you need 4/2 nm not 6/2nm.
 
I used the 11kw@208v asuming it is really a 15kw@240. I don't know of any truly 1ph 208v units. If it is a true 11kw@208v yes it would require 4/2 with a 70 amp OCPD acording to manufacturers specs.
 
While I was checking several manufacturers specs I noticed some are no longer using just multiples of 5kw for their heat strips. Some have 7kw, 8kw, 14kw. I think it is very important that we as electricians get the specs of the units before we pull wire or we may be suprised when the units are set. 60 and 30 were common for 15kw@240v, now it may be 45 and 40, etc.
 
Status
Not open for further replies.
Top