As we approach winter in tight financial times in the swine industry, producer’s thoughts are turning to how to best manage their heating and ventilation systems to keep their utility and energy expenses in line.

There are few publicly available production cost summaries.  One of the best is the information from the Center for Farm Financial Management at the University of Minnesota (www.finbin.umn.edu).  For the 4 year period of 2004-2007, wean-to-finish cooperators in this record program reported an average fuel and oil expense of $1.43 per pig and a utilities expense of $1.04 per pig.  Fuel and oil includes both propane and any diesel and gasoline charged to the swine unit for such items as tractors, lawn mowers, power washers, generators, pickups, etc.  Utilities include electricity and telephone/internet.  Surprisingly, both fuel and oil and utilities varied little for the 4 year period.  There was no indication in the data set of what the mix is of curtain sided versus tunnel wean-finish facilities.

Finishers of feeder pigs reported fuel and oil expenses of $0.71/pig and utility expenses of $0.62/pig.  For farrow-weaning cooperators (average inventory of 950 sows), the fuel and oil expense was $0.49 per pig weaned while utilities were $1.03/pig weaned.

Once facilities are tightened for winter operation and have the appropriate insulation in the ceiling and side walls, the major causes of excessive heating expenses are:

1. improper minimum ventilation rates
2. improper furnace sizing
3. improper temperature selection

As I work with a large number of different types of facilities and production systems in the upper Midwest and Canada, I continually find that producers have a very limited knowledge of their ventilation system.  In most situations, they don’t have any idea of the capacity of their system, nor do they fully understand the impact of small ventilation mistakes on propane usage.

The MWPS (Midwest Plan Service) recommends the following minimum ventilation rates for moisture control in swine facilities:

            Weaning – 30 lb (13.6 kg)        2 cfm/pig

            30-75 lb (13.6- 34 kg)             3 cfm/pig

            75-150 lb (34-68 kg)               7 cfm/pig

            >150 lb (> 68 kg)                     10 cfm/pig

            Gestating female                       12 cfm/female

            Farrowing                                 20 cfm/crate

These numbers don’t mean much to most producers until you add in the approximate capacity of various sized fans.  While such items as shutters, discharge cones, hoods, etc have an impact on the capacity of exhaust fans in negative pressure systems, the following rough estimates are valuable starting points for producers trying to understand their ventilation systems:

                        Fan blade diameter, in.  Approximate CFM

12                                                                                        1200

14                                            2000

16                                                                                        2500

20                                                                                        4500

24                                                                                        6000

36                                                                                        12000

Suppose that you have a 300 head weaned pig room, and there is a 12” fan running as the minimum fan.  This fan has the capacity for 4 cfm per pig, which is twice the recommended minimum ventilation rate.  Either this fan needs to be replaced with a smaller fan, or it needs to be connected to a variable speed controller and set to operate at 50% of its rated output.  Notice that I didn’t say 50% of its rated speed or 50% on the controller.  Generally small variable speed fans achieve 50% of their rated output at approximately 65-70% of their rated rpms.  Twenty four (24) in. diameter fans often achieve 50% of their rated output at 60-65% of their maximum rpms.

There is quite a bit of variation between ventilation controllers on how they control variable speed fans.  Depending on the controller specifics, a 50% setting as the minimum speed may or may not be anywhere close to the intended 50% operating performance.

Improper furnace sizing is usually the result of installation of a furnace that is too large for the facility.  A furnace is large enough if is shuts off occasionally on the coldest day of the year.  When furnaces are too large, the end result is rooms that have large temperature variations when the furnace operates.  Many times this results in the temperature at the controller temperature probe rising beyond the room set point, resulting in the ventilation system increasing the ventilation rate to remove the extra heat, which means the room cools and the process starts again.

Most ventilation controllers log the high and low temperature for the last day or since the controller was last reset.  Using the controller’s temperature logs, the high, low and set point temperatures should recorded on a daily basis.  When the facility is operating in the heating mode, the daily high temperature should never be at or above the set point temperature.  If the high gets to or above the set point, this suggests that the ventilation system responded by exhausting the heat just added to the room with the furnace.  To prevent this from happening, as a starting point, set the furnace to shut off at 2^oF (1^oC) below the room set point temperature.

Many producers make the mistake of assuming that the set point temperature for the controller will be the room temperature at the temperature probe.  This is not the case.  In cold weather, if the furnace is set to turn off 2^oF below the set point, the room temperature should be 2^oF colder than set point as the furnace ‘OFF’ temperature is the control point for the room.

As pigs grow and produce increasing amounts of heat, the ventilation system responds by increasing the ventilation rate.  If stage 1 is variable speed and has a 2^oF bandwidth, when stage 1 is operating at 100% speed, the room must be 2^oF warmer than set point.  This is because the controller is set to not attain 100% speed unless the room is 2^oF warmer.  Set point is just the decision point from which the controller makes decisions as to which devices to operate in the ventilation and heating system.

Photo caption:  Nursery heater-1 – Having more furnace or heater capacity than required leads to more variable temperatures and higher energy bills