Heating Elements

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Chamuit

Chamuit

Grumpy Old Man
Location
Texas
Occupation
Electrician
I am going to install some heaters (heater assembly) for a vat. Currently there is a single phase heater being used right now. It is on a 50A circuit with a 50A res/40A fla contactor to open an close the circuit.

The customer ordered a three heater assembly to replace the single unit. Each heater is a 25A single phase unit with the OCP @ 50A according to the tag.

So if I wire them up to a three phase circuit as the wiring diagram shows. (Doing AB, BC, CA which evenly distribute the loads.) I get 6kW * 3 = 18kW
18kW ? 240V 3P = 43.37A
At 125% I get 54A.

So, do I use a 60A breaker and 60A res contactor?
Or, do I follow the single phase ratios and go 75A and 75A?
 
Smart $

Smart $

Esteemed Member
Location
Ohio
Chamuit said:
I am going to install some heaters (heater assembly) for a vat. Currently there is a single phase heater being used right now. It is on a 50A circuit with a 50A res/40A fla contactor to open an close the circuit.

The customer ordered a three heater assembly to replace the single unit. Each heater is a 25A single phase unit with the OCP @ 50A according to the tag.

So if I wire them up to a three phase circuit as the wiring diagram shows. (Doing AB, BC, CA which evenly distribute the loads.) I get 6kW * 3 = 18kW
18kW ? 240V 3P = 43.37A
At 125% I get 54A.

So, do I use a 60A breaker and 60A res contactor?
Or, do I follow the single phase ratios and go 75A and 75A?
Click to expand...
You don't need to factor by 125% if the heaters will typically not be energized continuously 3 hours or more, i.e. 50A equipment. If typically energized continuously 3 hours or more, use 60A equipment.
 
david luchini

david luchini

Moderator
Staff member
Location
Connecticut
Occupation
Engineer
Smart $ said:
You don't need to factor by 125% if the heaters will typically not be energized continuously 3 hours or more, i.e. 50A equipment. If typically energized continuously 3 hours or more, use 60A equipment.
Click to expand...

What about 427.4? I'd say he needs 60A equipment even if the equipment isn't normally energized continuously for 3 hrs or more.
 
Chamuit

Chamuit

Grumpy Old Man
Location
Texas
Occupation
Electrician
The tank is probably 500 gallons or so and they have to re-heat it in them mornings in the summer and keep it warm in the winter. It is a continuous load. I had looked in the 420-ish sections myself and came away with the 60A ratings.
 
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