Steps for calculating the total length of MHI GAXP® heating elements for a new furnace.
Step 1. Power Required.
Please size the furnace interior. Now use the furnace calculator on GAXP® to determine how much power is required for the furnace at the maximum temperature..
Step 2. Additional Power Required?
Make further power corrections if the planned furnace insulation is weak or a high heat -up rate is required. Adding about 50% more than calculated power in Step 1 may be ideal if the insulation is weak.
Step 3. Determine the Shape and Size of Individual Heating Element
The Choices are Dumbbell, U- Shaped or Coil Shapes
U-shaped elements are hung from the furnace-roof or from the furnace sides. Dumbbell elements are used in a horizontal position inside a furnace. Schematics of various configurations inside a box. Coils may be hung from the roof.
furnace are shown below under step 5 in ‘More Resources’. Calculate the total GAXP® element heater length required by choosing a shape, sizing it to your furnace.
The calculator will also show the total power for the number of heating elements considered. Please ensure that the total power is at least equal to the Step 2 result.
The cold (terminal) section, Lu, should be at least a few inches larger than the insulation in order to connect your electric (braided wires) properly. Connections must not get hot during use. Good furnace manufacturers use strong fans to keep the terminal area (electrical connections region) in a cold state.
Step 6. Consult Resources.
Contact MHI for a final check. MHI can provide advise on the control system you may need (BPAN, XPAN or TRIPAN). BPAN prices are listed in the MHI store. When purchasing a control panel please ensure features like soft start and current limits. Please use a power transformer that matches the voltage of the furnace. MHI can also provide a certification-logo for the furnace.
*Furnaces should be constructed only by experienced furnace maker. Please observer all safety rules/practices commonly associated with high temperature, high voltage, high current. Always please use only industry approved insulation. Please use high temperature safety