Make maintenance mandatory

A good maintenance program anticipates problems and takes action to minimize their occurrence. Maintenance should include a thorough inspection and any corrective action needed to keep the structures and equipment in good operating condition. Cleaning and tidying up the greenhouse can save money and increase energy efficiency. The following checklist identifies the major areas:

Greenhouse frame

Inspect diagonal frame bracing to see that it is in place and tight. This bracing is important to prevent racking of the frame and the loosening of the glazing.

• Tighten collar tie and truss bolts. These loosen from expansion and contraction due to heat and movement of the structure in the wind.
• Inspect the gutters. Clean leaves and debris from gutters and downspouts. Caulk any joints that may be leaking water with a gutter caulk. Inspect for rust. Wire brush and coat these areas with a cold galvanizing spray or asphalt coating.

Glazing

Light is usually the limiting factor in plant growth during the winter. The glazing should be clean.

• Repair any small holes or tears in the poly cover with a polyethylene tape or Poly Patch which is available in widths to 10 inches. If the poly has stretched or is loose, it may have to be tightened by removing the lockstrip inserts and pulling the plastic taut. Inspect for soundness at the attachment edge. Replace plastic if it is older than four years. Clean and inspect the inflation blower. Check the inflation pressure. It should be about ¼-inch water static pressure or about the same as an inflated balloon. Too much pressure will stretch the plastic and increase the space between the layers. Too little pressure will allow the plastic to ripple in the wind and tear where it is attached.
• Polycarbonate and acrylic panels should be washed with a mild detergent and lukewarm water using a soft sponge to remove dirt, smog and shading compound. Check to see that the attachment extrusions are tight.
• For glass covered greenhouses, check the barcaps to see that they have not become loose. Remove spray-on shading with a cleaning compound or a shade remover.

Vents and louvers

These allow considerable heat to escape during the winter if they do not close tight.

• Roof and sidewall vents get considerable use and need to be adjusted so that they close even and tight. This involves lubricating bearings, rack and pinions, vent arm hinge points and checking fluid in gearbox drives. In houses with vents that don’t close tight, adding weather stripping may be the only way to stop excess infiltration.
• Maximum and minimum vent position limit switches should be checked to see that they will stop vent travel at the correct position.

Fans and shutters

• With the power turned off, inspect and clean the fan blades, motor and shutter. Check that the blade is not loose on the shaft.
• Check the fan belt for wear. The belt should ride at the top of the “V” groove. Adjust the belt to achieve ½-¾ inch deflection in the center between the pulleys.
• Lubricate the shutter hinge points so that they close tight. A 48-inch shutter that fails to close properly leaving 1-inch gaps allows 23,000 Btus/hr of heat to escape.
• Clean evaporative cooling pads and tanks. Replace deteriorated pads.
• Repair or replace motorized shade/energy blanket system material. Check to see that the limit switches are working properly and that the blanket closes tight.
• Service horizontal air flow (HAF) fans by cleaning the blades and guards. Oil bearings if they are not sealed.

Heating systems

Before the heating season begins, have all equipment serviced.

• On oil fired units this should include replacing the fuel filter and nozzle, cleaning ignition mechanism, and valve.
• On gas fired units, clean burner ports and orifices, pilot burner and air slots.
• Inspect fuel supply piping for leaks.
• Check limit controls including high heat and fan or blower operation and the barometric draft control on the flue pipe. On boilers check the safety pressure relief valves.
• Have a combustion test done on the heating unit to check efficiency, draft and smoke level.
Inspect heat exchangers for leaks and corrosion and clean heat exchanger surfaces including vacuuming and wire brushing radiators and fin pipes.
• Be sure that flue connectors are tight and weather cap is in place.
• Check the fuel supply and operation of backup heaters.

Thermostats and sensors

• Check the accuracy of all thermostats and sensors by using an ice bath or an accurate laboratory thermometer.
• Clean sensor coil with compressed air. Use a contact cleaner or draw a piece of paper through exposed contacts.
• Check that all wire connections are tight and not broken.
• Run a test mode on the temperature alarm system to see that it is operating properly.
• Test the back-up generator and check its fuel supply.

Assigning an employee to do routine maintenance will avoid many annoying problems and save on the heating bill this winter. Using the above checklist as a guide to track preventive maintenance can make this job easier. To save time, set up a file with the operating manuals and the procedures to follow.