Direct-fired heating system proves safe, efficient, according to study

Editor's Note: Back in January, we reported on an Ohio State University study that analyzed the efficacy of L.B. White's propane-fueled direct-fired heater system (see article at the end of this writeup). Now, we provide you comments from Eric Keil, the president of New York's Emma's Garden Growers, who has been using these heater systems for five years:

"Thank you for reporting on the research being done at OSU with L. B. White's direct-fired heaters. We have had eight of these units in service at our nursery for five years with excellent results and no evidence of plant damage. Our experiences with these heaters might be helpful to others.

"First, we are burning natural gas. Our gas supplier had significant reservations about supplying fuel to direct-fired heaters. They were most concerned about the build up of carbon monoxide and at first did not want to provide gas service for our heaters. Since we had already purchased the heaters, we were committed to finding a solution. After some negotiation and with the help of L.B. White, we were able to use our heaters. I recommend that anyone considering these heaters first check with their gas supplier to be sure they can meet their requirements.

"Another consideration pertains to installation. These units are designed so that they can be mounted outside the greenhouse or building in the southern states. For this reason the control panel is on the back. We did not take this into consideration prior to installation and located our heaters close to the side wall. This makes the panel difficult to access.

"Finally, as shown in the photo, we covered the opening in our heaters with hardware cloth. This was done because the first year we had the heaters in service every one of the units had a family of birds living in it. This was an easy fix that also prevented the potential fire hazard. I would recommend these heaters to others interested in using hot air heaters." --Eric Keil, president, Emma's Garden Growers

And here's the original story:

Direct-fired heating system proves safe, efficient, according to study

Direct-fired heating system doesn't cause plant damage and uses 11.6 percent less fuel than indirect-fired heater, according to recent study.

L.B. White’s Therma Grow propane-fueled direct-fired heater system is up to 11.6 percent more efficient than certain indirect-fired models, according to a study recently conducted by the Ohio State University and funded by the Propane Education & Research Council (PERC).

The study also concluded that the Therma Grow system does not cause plant damage, according to a PERC press release. The trial compared the Therma Grow system with an indirect-fired model and took place in two separate 24 by 48 foot double-poly greenhouses.

During the trial, scientists monitored fuel consumption, relative humidity, temperature, CO₂ and ethylene in both greenhouse environments. The greenhouse using the Therma Grow system reportedly used 11.6 percent less fuel than the greenhouse with the indirect-fired heater.

The reduction in fuel consumption is the result of Therma Grow’s heat combustion design, which converts almost all fuel energy into useable heated air, according to PERC. While an average vented heater is able to convert only 80 percent of its given fuel into usable heat, the Therma Grow is able to convert 99.9 percent.

Assessing plant damage
Along with monitoring fuel usage of the two houses, six plant varieties were tested during the study for signs of damage and overall quality. They were tomato, zinnia, marigold, impatiens, snapdragon and petunia plants. Researchers monitored plants for symptoms of off-gas damage as well as pests, diseases and signs of phytotoxicity throughout the experiment. No damage or other issues were reported while using the Therma Grow system, according to PERC reports.

The study does not validate all other direct-fired heaters as being plant-safe. The study only tested the Therma Grow system.