12
HEATER SELECTION
DETERMINE THE RIGHT SIZE FAN FOR YOUR BIN SIZE FIRST
WARNING!
Determining the correct size fan for the size of the bin, type of grain and needs, is the key to
successful drying. Your heater selection only needs to match your fan size, fuel source at hand, and type
of heater controls desired. RESPONSIBILITY FOR THE GRAIN CONDITION IS YOURS!
WARNING!
Incorrect fan size will cause your heater to not preform to your expectations. Too much
static pressure is the leading cause of poor heat, burnt wiring in the chamber, and may cause your
chamber to burn up. Oversized fans for a bin will cause as much damage as undersize.
Recommendation
We recommend the resources of the University of Minnesota’s Bioproducts and
Biosystems Engineering Department. Their handy Fan Selection Guide program can be accessed at the
following web site:
http://webapps.bbe.umn.edu/fans/
Please note that we do not recommend over 4” of static pressure when using an axial fan, and 5” up to
10 HP 1 phase 1700 RPM. Low speed centrifugal fans, from 3 HP to 7.5 HP not exceed 5”. 10 HP threw
15 HP no higher than 7”. 20 HP threw 25 HP, 9 inches; and 30 HP to 40 HP, 11”.
NOTE:
Provide one square foot roof opening per thousand cfm fan capacity.
FUEL SOURCE:
Liquid propane models (with vaporizer) are recommended for drying when using over
one million BTU per hour
(see table on page 13 for tank size selection).
Always use liquid propane when
achieving more than a 50 degree raise; otherwise consider a super low temp heater using vapor
propane. For LP fuel line, use 5/8” OD type K copper tubing or ½” schedule 80 black steel pipe. Use 3-5
foot of flexible LP hose between fuel line and heater. Before connecting to heater, purge gas line to
blow out any dirt in pipe. When using vapor heater, connect at regulator
(see A-LP Vapor drawing on
page 13).
When using LP liquid heater, connect at Y strainer (
see B-LP Liquid drawing on page 13
).
Natural gas models are available. Your gas company should deliver 15 psi under flow to obtain
maximum heat output. Check with Gas Company for pressure available and pipe size required to
expected btu/hr load. Regulator is not included with natural gas models. Install gate value (not
include) in gas line near heater to control heat output.
LOW TEMPERATURE DRYING:
Low temperature drying is used to achieve a 25% drop in relative
humidity. Raising the outside temperature (ambient) by no more than 10 degrees, when using an axial
or centrifugal fan producing 2/3 to 3 cfm per bushel, and a Super –Low heater will achieve this. Keep in
mind, we suggest a grain spreader for your bin and this type of drying should be in a situation where you
are using your bin to dry one bin full per year (not for continuous flow drying). All super low heaters
come equipped with thermostat and under bin thermometer. Never exceed 15 degree temperature rise;
this can cause a number of problems like over drying, and cause a crusted condition resulting in bin
failure that is not covered by the bin manufactures warrantee.
Further notes on low temperature
drying can be found on pages 19-21.
