For any hobbyist who grows their own plants, a nursery is an indispensable accessory! I propose to describe a model using one of the latest innovations in lighting.

In the beginning, there were the HPS (High Sodium Pressure) lamps with excellent lighting efficiency, but they consumed a lot of energy and heated up enormously; one could take advantage of this last defect but it was difficult to manage. Then came the neon strips, which consumed less current and did not heat up, but had a short life span. Then the LEDs appeared, even more economical in energy, with high efficiency of lighting without loss of performance but more expensive to purchase..

Finally, the DOB LED chip lamps: small technical revolution, minimal space requirement, very attractive price, easy to assemble coming in different powers of 20/30/50 Watts and in emission color from Cold White (6500K) to Warm White (3500K) through Full Spectrum.

Equipped with a chip, these innovations self-regulate according to their heat by decreasing their brightness. To overcome this small inconvenience it is enough to ventilate them, by mounting them on a mason's rule provided at each end with a fan, one in intractor the other in extractor, the circulation of air inside the rule maintaining the temperature between 30 and 33 ° C thus allowing an optimum performance.

Equipped with a chip, these innovations self-regulate according to their heat by decreasing their brightness. To overcome this small inconvenience it is enough to ventilate them, by mounting them on a mason's rule provided at each end with a fan, one in intractor the other in extractor, the air circulation inside the rule maintaining the temperature between 30 and 33°C thus allowing an optimum output.

The nursery which will be detailed below has for framework a metal shelf of 1,80 m(L) X 0,60 m(l) X 2,50m(h) which we dressed with panel OSB of 15 mm. This one will be composed of 4 levels of a little more than 1m² each, 2 for the first age and/or seedling stage and 2 for the second age stage. All DOBs used are 20W.

Seedling/early stage: 1,80 m X 0,60 m X 0,45 m (+/-0,5 m3).

2 rules of 5 DOB (3 Cold White CW - 2 Hot White HW) to be arranged as follows:

 |--CW--------HW-------CW------HW------CW--|

|--CW--------HW-------CW------HW-------CW--|

Floor 2nd age: 1,80 m X 0,60 m X0,70 m (+/-0,75 m3).

2 sets of 5 DOB (2 Hot White - 2 Cold White - 1 Full Spectrum)
1 rule of 4 DOB (2 Full Spectrum - 2 Cold White) to be arranged as follows:

|--CW--------HW-------FS------HW-------CW--|

|---------FS-------CW-------CW-------FS--------|

|--CW--------HW-------FS-----HW-------CW--|

Each ruler is bored at 80 mm, on one side and at each end, so it can be equipped with a fan. One is mounted as an intractor and the other as an extractor, thus creating an air flow to cool the ruler. The DOBs are placed equidistant from each other, we will insert between them and the rule, thermal paste to diffuse the heat released on the rule. Finally, the whole is fixed with self-tapping screws that are insulated with a rubber washer. The fans can be powered by 12V or 9V, in the latter case they will turn less quickly and therefore cool less but this will extend their life as much, to each one to adapt according to its needs.

Each level will also be provided, fixed on a wall, with a small fan of 50 mm diameter as an extractor for the evacuation of the surplus of heat and for the arrival of "new" air thus of CO2 necessary to the photosynthesis. Opposite this one, a vent/hole (+/- 30mm) will be made to allow the exchange of air depleted in CO2 with "new" air. Inside, another fan is placed at the top in a corner in order to stir the air inside the compartment. These two fans will be supplied with 9V so that they do not turn too fast.
The electrical installation, although relatively basic, requires method and precision, especially when combining different voltages, i.e. 220V for the DOBs and 9 and/or 12V for the fans. Each level will be controlled by a programmer, where dedicated switches will be connected, one for the DOBs power supply, another for the ventilation of the rules and a last one for the "used" air evacuation and the mixing inside the boxes. It is strongly advised to draw a dedicated line to the nursery which will be protected by a 30 ma differential circuit breaker in order to protect both the equipment and the user.

In any case, if you do not have the required skills to make the connections, contact a professional to make them.

Some measurements obtained after the first tests: With 15h of lighting per 24 h the estimated DLI (daily quantity of energy received by the foliage and usable for the growth -photosynthesis- in mol/m²). * first age stage: ~ 14 (minimum satisfactory value recommended for the first age ~9/10) * second age stage: ~ 17 (minimum satisfactory value recommended for the second age ~12) Temperature of the boxes during the lighting phase: +/- 23-27°C with an outside temperature of +/-13°C. The thermostats connecting the electrical cords switch off below 20°C and stop at 22°C. The temperature of the ruler has never exceeded 34°C.

Important info: Most of the F1 rootstocks available on the market have in their ancestry "solanum habrochaites" which would be responsible for a physiological disorder of intumescense type (edema/swelling/pustule) under LED type lighting. In the case of cultivation of this type of rootstock and in order to avoid this problem, it is essential to add a very cold white lighting (12000 to 15000K), or the use of CFL UV-B 100-10.0 or CFL UV-B 150-10.0 of 13Watts, these last ones having a higher output, (2 bulbs of this type per m²). The feedback from several amateurs confirms the problem and its resolution with this type of lighting.

Below is a link to a scientific article dealing with this problem…

https://www.sciencedirect.com/science/article/abs/pii/S0304423817305484