Ckt for a heater

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augie47 said:
40 ??
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Correct. 15 plus 40 doesn't always add up to 55.

Heater draws 27.8 amps x 1.25 = 34.75

Blower draws 1.8 amps not sure it even needs to have 1.25 factor applied but either way puts you over 35 and under 40, so minimum conductor ampacity and minimum overcurrent protection for the feeder is 40 amps. You can tap that feeder with those two loads with a 40 and a 15 amp breaker.
 
K8MHZ said:
It looks like the heater is 3 phase 40 amps and the motor is single phase 15 amps max OCPD. Two circuits. At least that's how I see it.
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I agree. I'd go the small sub-panel route. One 3p breaker and one 2p breaker.
 
kwired said:
Correct. 15 plus 40 doesn't always add up to 55.

Heater draws 27.8 amps x 1.25 = 34.75

Blower draws 1.8 amps not sure it even needs to have 1.25 factor applied but either way puts you over 35 and under 40, so minimum conductor ampacity and minimum overcurrent protection for the feeder is 40 amps. You can tap that feeder with those two loads with a 40 and a 15 amp breaker.
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Heater draws 37.8 amps.
 
my inclination would be a #8 with a 50A feeder CB with local 15 and 40 A OCPD.

or run two branch circuits. a 2 pole 40A Cb for the heater and a 3 pole 15A CB for the heater.

probably not cost much difference.
 
david luchini said:
4th line of the nameplate says: Heater Amps 27.8

Of course, then you'd have to wonder how they got an MCA of 37.8 for the heater.
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That was my initial thought that it was only one circuit for both the heater and fan, like an AC unit. The numbers work out close when you add them together.
 
K8MHZ said:
Heater draws 37.8 amps.
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David answered with what I had to say.

david luchini said:
4th line of the nameplate says: Heater Amps 27.8

Of course, then you'd have to wonder how they got an MCA of 37.8 for the heater.
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david luchini said:
It's close, but it's pretty clear that the unit is meant to have separate connections.
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I don't know the manufacturer knew what they were doing when marking it. MCA should be 125% largest load plus other loads I believe, worst case it would be 125% both the loads, they didn't match for either way, was close enough if rounding to tenth of an amp for an individual blower circuit though.
 
K8MHZ said:
It looks like the heater is 3 phase 40 amps and the motor is single phase 15 amps max OCPD. Two circuits. At least that's how I see it.
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I agree,
see schematic 3 phase connections to L1,L2,L3 to bottom of rotary switch for heating elements. And single phase connections to terminal block L1,L2 for fans.
 
Going abck there today just going to add another 20 a 208v ckt and charge him for it $$$$$ I love change orders

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peter d said:
That is some of the worst factory wiring I've ever seen but fairly typical for HVAC manufacturers. :roll::roll:
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Several years down the road when the wiring diagram can't be read, it will be easier to trace conductors when troubleshooting because they aren't all bundled together:)
 
peter d said:
That is some of the worst factory wiring I've ever seen but fairly typical for HVAC manufacturers. :roll::roll:
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I'd be shot on sight (twice) if I ever let something looking like that leave our shop. That's embarrassing, or it should be.


SceneryDriver
 
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