Radiant Heating for Greenhouses

On the bench or on the greenhouse floor, Delta T’s radiant heating systems offer the grower distinct advantages, including accelerated rooting and plant growth, as well as 20-30% fuel savings over conventional forced air heating. Maximum soil and plant temperature control combine with the ability to create different temperature zones for the ultimate in flexible growing. And because radiant systems heat objects first and air last, people stay warmer and more comfortable, and in the case of floor heat, happier with warm feet!

Delta T’s engineered radiant heating systems can meet the needs of any grower. Packages include heating system components (heat source, controls, and radiation) as well as performance engineered drawings (pipe layouts and electrical diagrams), installation supervision, or installation itself, as required.

How do you know how much heat is needed for your greenhouse? Our heat loss calculator can determine how much heat is being lost on a per house basis.

DELTA-TUBE™ EPDM SD rubber tube bench heating

This bench system heats the greenhouse starting at the soil level. Heat rising from the bench warms the soil and the plant roots. Tubing spaced 2 to 3 inches apart provides even soil temperatures, which prove extremely beneficial to propagators. Seed germinators and plug producers have found that by heating the soil, they achieve a higher germination rate and quicker production time. Growers have found a reduction in rooting cuts by heating the soil directly.

The DELTA-TUBE EPDM rubber tubing used in this hot-water heating system offers superior heat transfer capabilities as well as excellent resistance to temperature degradation and chemicals. The SD system’s small tube design reduces water volume, enabling the system to respond quickly and efficiently.

The DELTA-TUBE manifolds use a unique plastic fitting that creates a watertight connection to the tubing guaranteed not to leak. Tubing is easily installed into the manifold, and each manifold is custom manufactured for each system. Cut to the bench width for ease of installation, tubing spacers secure the Delta T tubing at optimum intervals.
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DELTA-TUBE™ EPDM LD rubber tube in-ground (sand, soil or gravel) heating

Similar in concept to the DELTA-TUBE EPDM SD system, with the same productivity and fuel saving advantages, this hot water heating system with its 4 to 6 inch tube spacing is the system of choice for starter houses. It also excels in the nursery industry for general growing. Growers using this system for heating soil or nutrient bags of tomatoes and cucumbers have shown a 50% increase in yield. Grape growers have found a quicker and more even callusing pattern by using bottom heat to callus grade stock.
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DELTA-TUBE™ PEX tube floor heating

The DELTA-TUBE PEX heating system heats the greenhouse from the floor by running hot water through a grid of durable, cross-linked high-density polyethylene polymer tubing installed in the concrete. Using the concrete floor as a radiant surface, heat radiates from the floor into the greenhouse and directly to the plants. The direct contact between the root zone and the warm floor provides for maximum soil and plant temperature control, resulting in consistent temperatures and even crop growth. Compatible with any type of heat source, the DELTA-TUBE PEX floor system allows for different temperature zones, increasing grower flexibility. Because it eliminates the need for loud and unsightly unit and infrared heaters, it is an excellent choice for a retail area. In fact, retail garden centers report that customers stay longer and buy more because this silent and comfortable heating system makes for a great shopping environment. 

DELTA-FIN™ TF under-bench heating system

The DELTA-FIN™ aluminum under-bench heating system heats the greenhouse by running hot water at temperatures of up to 230°F through the fin tube system. The fin tube then heats the air around it, distributing heat to the soil, roots and foliage of the plants through a combination of natural convection and radiation. Because of the superior transfer capabilities of the DELTA-FIN TF, even temperatures are maintained throughout the system and the growing media. The end result is an envelope of warmth around the entire crop which the grower controls.

Two fin sizes allow for targeted applications:

• TF1 two-fin aluminum with 3/8" fins is ideal for climates that have low heat requirements or need closer temperature control, like plug production
• TF2 two-fin aluminum with 1" fins has the added surface area for more heat transfer to meet high heat requirements

Other advantages:

• Lightweight aluminum construction allows for hanging material from benches without special support
• Rugged construction can be supported on 12-foot OC hangers
• External coupling technology for easy installation
• Requires NO special tools for installation
• Does not restrict flows like internal couplers
• Does NOT require Tek screws to hold material together
• All-aluminum return loops make installation rigid. No rubber hose required for loops.
• Special barb connection to main lines using a minimal hose connection
• Low water volume allows for quick response time

DELTA-FIN™ SF high-output heating system

Placed around the perimeter or under the gutter, the DELTA-FIN SF heating system puts out enough energy to heat a greenhouse range, melt snow from the gutters, or supplement an under-bench heating system. Channeling hot water at temperatures of up to 230°F, the finned pipe heating system heats the air around the tube and distributes it via natural convection.

The high output finned pipe is made of schedule 40 aluminum pipe and fins that are twice as thick as standard baseboard radiators. This heavy-duty construction guarantees long life in a harsh environment, and allows the material to be hung from greenhouse columns spaced as far as 12 feet apart without additional center support.

Two sizes (1.25" and 2") allow for application flexibility when designing long runs or small temperature differentials requiring high flow rates. Grooved coupling technology absorbs enough expansion from the heated aluminum pipe so that, in most installations, no special expansion joints are required. Special fin configurations can be provided for under gutter snow melt or corridor heating.

Typical fin spacing:
48 fins per foot for 1.25" size
24 fins per foot for 2.00" size

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Greenhouse Heat Sources

Centralized or localized? Together, that’s the first question we need to answer when it comes to heating your greenhouse.

Centralized systems typically use a boiler to generate heat in one spot. Piping is then used to distribute the heat throughout the greenhouse. Centralized systems are often more efficient for large operations. However, the cost of installing and maintaining one can be high, and difficult to justify for smaller operations. These systems generally distribute heat as either steam or hot water of varying temperatures. Hot water systems require more complicated plumbing and circulating pumps. In addition, they require large volumes of water to achieve heat levels. Steam systems require less plumbing, and no circulating pumps. They provide more BTUs and allow for more rapid temperature adjustments. However, they do not provide heat reservoirs.

Localized systems are situated in the section of the greenhouse they are responsible for heating. There are many types of localized heating systems, ranging from gas fired and hot water unit heaters to radiant bench, under–bench, and floor systems, often the systems of choice for propagation and germination.

RBI boilers High quality construction, quiet operation, and energy efficiency as high as 82% make our RBI boilers the perfect choice for hydronic heating. Integral, 2-pass heat exchanger and standard bronze headers ensure long life and years of worry-free service. In fact, our RBI boilers virtually eliminate standby losses and condensation problems.   Multi-Stage Boiler Control RBI Dominator Power Draft Boiler   RBI natural draft boilers are the workhorses of the industry, using surrounding air to provide the required heat. Available in sizes from 100,000 to 400,000 BTU/hr, these boilers offer fast response, smooth heat transfer, load matching and up to 82% energy efficiency. Integral, 2-pass heat exchanger and standard bronze headers ensure long-life performance and years of worry-free service. RBI sealed combustion boilers. Looking for superior performance and serviceability in a high-efficiency, multi-stage boiler? Look to our RBI sealed boilers. Their sealed combustion chamber offers the flexibility of using outside air or mechanical room air, and provides a low NOx rating that meets the strictest air-quality standards. Plus their fan-assisted, multi-speed blowers and advanced staging control create high-efficiency stage firing in a compact package. Delta T oil fired boilers are available for capacities up to 15,000,000 BTU/hr and working pressures up to 125 psi. They come completely assembled, wired, and fire-tested for quality assurance. There is full access to the water sections and combustion chamber, and the easily removable tube bundle makes the boiler easy to maintain. Our electronic boiler control is an add-on microprocessor-based energy management control that regulates water temperature by sequencing up to 12 stages on a single multiple-boiler installation. With on-board diagnostics for easy troubleshooting, our electronic boiler control not only ensures lower operating costs; it can maximize crop turnovers, creating savings that can pay back your initial investment quickly. Click here for more information. (386KB)

Heat exchangers Our steam-to-water and water-to-water heat exchangers represent the latest technology in performance.  All are designed for superb efficiency, low maintenance, long life and fitting into tight spaces. Understanding how important growing space is, Delta T’s heat transfer units use up to 80% less floor space than shell and tube models, and weigh up to 10 times less. That means they are easy to ship and handle, and don’t use up precious growing space.

Gas-fired Shield unit heaters With their 5-year warranty, our Shield gas-fired heaters have 2-1/2 times the warranty of the competition. Which makes them a longer lasting, more durable, and more reliable source of safe, efficient, and economical heating for you. The GF Heater offers you stainless steel construction to withstand moisture and chemicals, a tubular heat exchanger for significantly longer life, 80% thermal (combustion) efficiency, and the highest BTU output of any gas-fired heater. Click here for more information. (2.5KB)     Sterling hot water unit heaters Sterling model “HS” horizontal unit heaters are available in both serpentine and header designs. Serpentine units offer outputs from 8030 to 35,900 BTUs and are ideal for hot water installations with limited clearances. Header type horizontal units range from 18,000 to 360,000 BTUs, and can operate with either hot water or steam. Both units come standard with totally enclosed motors. Explosion-proof motors are also available.

Piping for Greenhouse Heating How heat is delivered in a greenhouse is critical. Even distribution of heat, without hot or cold spots, is the goal. It is a goal that Delta T takes seriously. In our experience, uneven temperatures can result in uneven crop growth rates, as well as inconsistent maturation times. That's why at Delta T, we offer a range of piping options to optimize the heating in every greenhouse. How do you know how much heat is needed for your greenhouse? Our heat loss calculator can determine how much heat is being lost on a per house basis. Centralized greenhouse system piping When a central heating system is used to produce hot water or steam, grooved steel, copper, or PVC pipes can be used to distribute the heat energy throughout the greenhouse. Hot water systems typically require more piping and circulating pumps; steam systems require fewer pipes because steam provides more BTUs per linear foot of pipe than hot water. Steam also offers less movement resistance, which means smaller pipes can be used. Grooved steel pipe and fittings for greenhouse heating Delta T heating systems that use high temperatures (140° to 230°F) can use steel piping as the main lines to the radiation material. Although some companies use welded steel pipe for this, our grooved steel piping is just as good and reduces labor costs by as much as 50%. Copper pipe and fittings are an excellent choice for both low and high temperature greenhouse heating systems that require exceptional corrosion resistance. PVC pipe and fittings for greenhouse heating Delta T also offers low temperature/low pressure heating systems. These provide growers the ability to use less expensive PVC piping and fittings to distribute the heat from the heat source to the radiating materials. Care in designing the PVC piping system is required, but the advantages are numerous: PVC can be direct buried as there is no problem with rusting PVC is easy and quick to install; Just cut, primer and glue PVC piping is inexpensive compared to other materials

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Also see Delta-Temp™ warm water irrigation systems.