StinkyPanda
New member
Jpizle, the following was taken from Cannabis.com's grow FAQ
1. Air temperature
Your standard mercury/alcohol-bulb or digital thermometer is designed to measure the temperature of the air (But not radiant heat). This is what is being referred to in the usual growers 'rules of thumb' such as maintaining your grow above 16degC and below 30degC.
Most thermometers are only designed to measure air temperature – growers often mistakenly place their thermometer in direct light; radiant energy will warm your thermometer and give a higher than actual reading.
*Assuming your air is well mixed up by oscillating fans, it doesn’t really matter where you locate your thermometer. The best spot is probably about half the way up a wall, with a piece of cardboard over it (To shade it from radiant heat), exposed to the mixed air in the grow room.
2. Radiant temperature
Radiant temperature is the result of heat transfer bewteen objects at different temperatures without whats inbetween i.e. the air, being effected. In our case the plants are naturally at a lower temperature that the light and reflector so heat is transferred to the plants foliage from the light/refecltor through radiation. This causes the leaves to heat up. The plants can withstand much higher radiant temperatures (around 40-50degC) than they can air temperatures but if this is too high the plants can 'burn'.
The plants can withstand much higher radiant temperatures than they can air temperatures, but if this is too high the plants can “burn”.
'The hand test': Place your hand in a comfortable position for some time at the tips of your plants should be. If your hand feels “hot”, then the lights are too close, the radiant energy is too intense, and light burn may result. Do this test and raise your HID lights/reflectors periodically to keep light burn to a minimum.
Finally, monitor the conditions in your grow regularly as things are changing all the time, and you will soon get to understand the thermal dynamics of your particular grow space so you can get the most from it.
For future reference, if you run a digital 250 in the Secret Jardin DR60, your temperatures should be fine as long as you have a fan for extraction and passive intake flaps open. Now if the room that your tent is in is too hot, then you may want to go with the 150w.
1. Air temperature
Your standard mercury/alcohol-bulb or digital thermometer is designed to measure the temperature of the air (But not radiant heat). This is what is being referred to in the usual growers 'rules of thumb' such as maintaining your grow above 16degC and below 30degC.
Most thermometers are only designed to measure air temperature – growers often mistakenly place their thermometer in direct light; radiant energy will warm your thermometer and give a higher than actual reading.
*Assuming your air is well mixed up by oscillating fans, it doesn’t really matter where you locate your thermometer. The best spot is probably about half the way up a wall, with a piece of cardboard over it (To shade it from radiant heat), exposed to the mixed air in the grow room.
2. Radiant temperature
Radiant temperature is the result of heat transfer bewteen objects at different temperatures without whats inbetween i.e. the air, being effected. In our case the plants are naturally at a lower temperature that the light and reflector so heat is transferred to the plants foliage from the light/refecltor through radiation. This causes the leaves to heat up. The plants can withstand much higher radiant temperatures (around 40-50degC) than they can air temperatures but if this is too high the plants can 'burn'.
The plants can withstand much higher radiant temperatures than they can air temperatures, but if this is too high the plants can “burn”.
'The hand test': Place your hand in a comfortable position for some time at the tips of your plants should be. If your hand feels “hot”, then the lights are too close, the radiant energy is too intense, and light burn may result. Do this test and raise your HID lights/reflectors periodically to keep light burn to a minimum.
Finally, monitor the conditions in your grow regularly as things are changing all the time, and you will soon get to understand the thermal dynamics of your particular grow space so you can get the most from it.
For future reference, if you run a digital 250 in the Secret Jardin DR60, your temperatures should be fine as long as you have a fan for extraction and passive intake flaps open. Now if the room that your tent is in is too hot, then you may want to go with the 150w.