I have my room all setup ready to go. It seems to be too hot. I hav ea few questions.

1) where should the thermometer and hygrometer be mounted to get the temperature measurement we are looking for?

2) Do i need to make a better intake system or a better exhaust system?

I have a 4" exhaust with a diy carbon filter. Then i have about 10 1" holes drilled around the bottom for intake. I have the fan on the bottom trying to help move air around. Do you guys have any suggestions? Im not growing yet im just trying to make sure i have all the kinks worked out before i jump in.

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forgot to add that im using a 400 watt mh/hps setup. The light is abought 4 1/2 feet above where the plants will be. I just realized i forgot to seal up the top of the closet where i had to get the ballast through. I sealed it up and it seems like it migh tbe helping out a bit. Im open to any other suggestions though.

welcome to the forum. If you are going to use a 400 watt light in that area you will want to air cool that light seperate from the rest of the room. Mogie has great post on how you can do this by making a glass shield for the light fixture. Ckeck FAQ upper left hand corner of this page, the DIY list to find it. She has included pictures of the process. VV

question: is that aluminum foil? if it is, you may want to consider mylar or panda plastic as aluminum foil can cause hot spots which will burn your plants.

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No its mylar. I would never use aluminum foil. I figured i might have to air cool the light. Wanted to see if it was necessary or not yet.

Thanks for the responses though.

In order to know you are providing the right thermal environment for you plants through ventilation, oscillating fans etc. you need to understand the physical nature of the 'heat' in grow spaces, how it should be measured, and the mistakes that can easily be made.

Essentially there are two aspects to the thermal environment that you need to be aware of:

1. The AIR temperature
2. The RADIANT temperature

Although obviously related, these are 2 distinctly separate phenomena and your plants have different tolerances for each.

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.

Note:
[Cannabis loves high light levels/high radiant energy levels, but exceeding their tolerance for light can result in light burn and chlorophyll leaching out of the leaves. 600's & 1000’s put out a lot of light, and light burn can easily damage clones and young plants.

Light burn damage: initially the leaves look pale green (the edges may turn upwards, mimicking a Mg deficiency), then they turn yellow and finally yellow/brown as the leaves scorch.

Often you can see a circular pattern of intense light where the reflector has focused the light onto the plants. If plants outside of this intense light zone look greener and healthier, consider raising your lights.]

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Wow man thanks for a great response there. Im gonna go rip up a little piece of carboard around the termometer to get a better reading on the temp. Thanks a lot.

Brad

No problem. Good Luck! Thanks for the rep too.

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Well after playing around with it some more it looks like im definately gonna have to air cool the light. Gonna probably just go with this here...

High Tech Garden Supply

i have this setup righ tnow...will it be a good fit for it?

High Tech Garden Supply

i have the same euro reflector.. it works real good.. make sure you buy the inline fan from them too. if you get it from home depot you need to wire it your self (i made that mistake) youll also need ducting