some help please

Status
Not open for further replies.
memyselfandI

memyselfandI

Senior Member
Location
Hampton Roads, Virginia
We have a heat treat furnace getting installed in a couple of weeks and I need to have a few things clarified. The ambient air temperature where this furnace is gets to be about 120'- 130' F in the summer. We put the project out for bid and everyone came back with different numbers. There is a 225A circuit that feeds a transformer which is the heat source for the furnace. The raceway has to be ran overhead above the furnace approximately15' above it, total distance is about 80' with about 50' feet of the run being exposed to these high air temperatures. one contractor proposed running parallel 3/0 CU. Another was going to run 4/0 CU only because the breaker was rated at 50'C (I don't know why). I need some engineering help on this one.
 
I'll take a shot at this but.... no guarantees here

If the breaker is not in the temperature I am not sure what that has to do with it. So--- I would take 1/0 copper at 90 and multiply it by the correction factor of .76 for those temp.

1/0 copper at 90C = 170
Correction Factor at 130F = .76

170 x .76 = 129

Parallel the 1/0 and you get 258 amps. Seems big enough to me

You could just run one run of 300MCM copper and get 243 amps after the correction factor.
 
memyselfandI said:
We have a heat treat furnace getting installed in a couple of weeks and I need to have a few things clarified. The ambient air temperature where this furnace is gets to be about 120'- 130' F in the summer. We put the project out for bid and everyone came back with different numbers. There is a 225A circuit that feeds a transformer which is the heat source for the furnace. The raceway has to be ran overhead above the furnace approximately15' above it, total distance is about 80' with about 50' feet of the run being exposed to these high air temperatures. one contractor proposed running parallel 3/0 CU. Another was going to run 4/0 CU only because the breaker was rated at 50'C (I don't know why). I need some engineering help on this one.
Click to expand...
There are some additional info I would want to know. Transformer size, voltage, rated load amperage.
 
I admit that I don't know what a "heat treat" furnace is. The question that comes to mind is "is the heat being used in the summer?". If not, then why would the summer ambient tempature be an issue? (Assuming the transformer is just feeding the heater).
 
The heat treat furnaces I have worked on were for drying jet engines, LARGE 2500 amp SCR controlled. These furnaces are utilized in a variety of manufacturing applications. The transformer is utilized most likely utilized to step up the voltage at the furnace.
 
brian john said:
The heat treat furnaces I have worked on were for drying jet engines, LARGE 2500 amp SCR controlled. These furnaces are utilized in a variety of manufacturing applications. The transformer is utilized most likely utilized to step up the voltage at the furnace.
Click to expand...

Thanks Brian!
 
Status
Not open for further replies.
Top