1. Greenhouse Management
Greenhouse Heating

2. Greenhouse Heating
After the cost of labor, greenhouse heating is the greatest expense a grower will have.
Heating costs:
Fuel
Greenhouse location
Crops grown

3. An Outline of Heating Systems
Central Heating
Steam
Hot water
Biotherm Heating
Unit Heater
Infrared (Radiant) Heater

4. Central Heating Boiler heats water or makes steam.
Hot water systems operate at temperatures of around 180 degrees F.
Steam systems operate at temperatures between degrees F.

5. Central Heating
Coil

6. Central Heating-Coil Location
The pipes (coil) that distribute the hot water or steam are mounted:
on the curtain wall
above the crop
below the benches
in the floor

7. Coil Location: Curtain Wall

8. Coil Location: Above the Crop

9. Coil Location: Below the Benches

10. Coil Location: In the Floor
Delta Tube HD Floor Heating

11. Floor Heating Plastic tubes are buried in the floor.
Can be used in gravel or concrete floors.
Good for bedding plants which are typically grown in flats on the floor.

12. Advantages of Below Crop Heating
Improved heat transfer to the crop.
Better root development and plant growth.
Increased foliage temperatures and reduced condensation problems.
Energy savings.

13. Finned Pipe vs. Bare Pipe
Finned pipe increases the surface area for heat dissipation.
The external surface area of 100 linear feet of Delta Fin Multi Fin pipe is approximately the same as 844 linear feet of 2” bare pipe.
DeltaFin TF
Delta Fin Multi Fin

14. Hot Water Biotherm Heating
Uses flexible plastic tubing through which hot water is circulated.
The tubes are installed 2-3 inches apart across the width of the bench.
Pots or flats are placed directly on top of the tubes.

15. Hot Water Biotherm Heating
DeltaTube Heating System

16. Hot Water Biotherm Heating
Supply Manifold
Return Manifold

17. Unit Heaters Typically fueled by natural gas.
Some models contain a coil that circulates hot water or steam.
Unlike boilers, unit heaters are located inside the greenhouses they heat.
Air flow can either be horizontal or vertical depending upon the model selected.

18. Gas-fired Horizontal Unit Heater

19. Horizontal vs. Vertical Unit Heaters
Horizontal Unit Heater
Vertical Unit Heater

20. Infrared (Radiant) Heaters
Installed directly above the crop.
Consists of a metal tube in which natural gas is burned.
Tube is heated to 900 degrees F.
A metal reflector directs the heat downwards.

21. Infrared (Radiant) Heaters
CoRayVac Infrared Heater

22. Infrared (Radiant) Heaters
Advantages:
very efficient (90%)
reduced fuel costs
since the heater heats the plants, soil, and benches, foliage condensation is reduced.

23. Infrared (Radiant) Heaters
Disadvantages:
cold spots; plants must be directly under the heater.
heater blocks incoming sunlight.
cold soil; as the crop grows larger it prevents the radiation from reaching the soil. Root rot is more problematic in cold soils.

24. The End