Greenhouse boiler

Ed Diamond

Small 20' X 30' greenhouse construction just started. Benches are U shaped around the outside, 3.5' deep. Center bench 7' X 19'. Constant light air movement above plants. Weil-McLain Ultra 80 boiler with Starfin heat pipes under the benches. Do you think that zoning the benches would produce different tempetures to the plants that sit on the slatted benches or do you think that the air movement would equalize the tempetures? I would like 55, 60 an 65 degree night temperaturs at the 3 zones.

Brad White_9

I would expect

the air temperature local to and above the radiation to be warmer certainly, than the ambient. If the elements were against the glass allowing a film of warm air to hug the walls, the inside would be more constant in temperature. Remember the only way the heat gets into the structure is to have the radiation warmer than the surrounding air. (Captial DUH there).

Air temperatures will generally (not definitively) be about halfway between the incoming air and the average water temperature. In other words if you have water at 150 in/130 out (140 average) and your air temperature is 60, your radiation leaving air would be about 100F. This will dilute with height at a fairly even rate as ambient air is entrained into the rising stream.

The temperatures near the elements will diminish with height. Your task then, if the plants are atop the benches, is to measure and elevate accordingly.

john_27

you can create different hot zones...and cold zones....within greenhouse by simple observation using a thermostat set 18" above bench height. In my greenhouse( 1916 lutton), we actually have two glass partitioned rooms to create separate temperature zones....also, the number of pipes under the bench varies with the evenness(in terms of day/nighttime swings), and, each bench has a valve which can be partially closed to partially control each bench....so, you can do what you wish, but you will have to do at least some room segimentation....pictures please...john