Hello Guys,
I am a first time grower (although I have a reasonable amount of horticultural experience), and I'm having problems controlling high relative humidity in my tent now that we are 10 days into flowering. I think that I have all the tools needed to control this properly, but suspect that I just haven't got it all dialed in correctly yet, so I am hoping some wise heads here can help me.
My setup is in my garage, which is not ideal as my intake air will be cold (current ambient temp is about 13 degrees, but this will drop to 5-8c before harvest). During lights off, I have a very effective small oil filled radiator which kicks in at about 20 degrees. There is nothing I think I can do about the intake air temperature except try to manage it. I am using a fan controller to control my intake and exhaust. This is set to kick in at 25 degrees, although it has an idle speed setting to ensure some exhaust / intake occurs below that temperature. I currently have it set to a moderate idle speed, and I have the balance controller slightly biased toward the exhaust, in order to maintain negative pressure. In addition to that I am using a single 600 watt HID for lighting, which currently gives me plenty of lights-on temperature.
I only bought a RH monitor a few days ago, and was shocked to see the RH at between 70-80% at different times through the day. So yesterday I bought a dehumidifier and put that in the tent as well. The probe of the RH monitor is set at the root zone level of the plants, and is adamant that RH is an average of 75%. I don't know where the gauge on the dehumidifier is, but that is reading closer to 55-60%. But the dehumidifier has been running at full blast all night, and is still not winning the battle, so the electricity usage is also getting to be a bit of a concern.
My feeling is that the RH is higher at the root zone because I have a very dense canopy. I have a 1m x 1m tent containing three sativas, which have been kept low and tight using LST. So they are not too high but are nicely filling the width and depth, to the extent that I may need to do some trimming soon to stop any leaves sticking to the sides. We are almost 2 weeks into flowering and some lovely looking flowers are starting to form. But I am concerned about root rot, and possible later bud rot.
The thoughts I have currently are:
1. I only bought the dehumidifier yesterday - perhaps it will take a little while to get things under control (I know this is probably wishful thinking, but hey).
2. Am I overwatering? The plants are taking a total of about 6lt per day between them. They don't look or feel overwatered, but perhaps they could manage on less. I am using coco by the way.
3. I could completely kill the intake fan, so that all intake would be passive. Maybe this would reduce the amount of cold air coming in.
4. I will buy another fan today and aim it directly at the root zone to try to make the RH more equal throughout the tent. (update, I already did this and there is no noticable difference)
5. If there was no other option I could potentially remove the radiator and place it instead in a sort of pre-chamber, so that I wasn't heating the tent directly, but heating the intake air. However this would cost me time, space and money, and so I'd appreciate opinions on whether it would be worthwhile before I go ahead and do it.
6. Lastly, would it be more sensible to simply cull two of my plants? The original intention was always to cull down to a single one, but they've all been really healthy to date and I haven't seen any real need to thin them out. But if that would reduce the transpiration and help keep things more manageable, then it makes sense to me to take one plant all the way to harvest rather than lose all three in the next couple of months to rot. Although there would be tears in my eyes at killing two of my ladies ;-)
Thanks for any suggestions, and sorry for the long post - I wanted to get as much info as possible, but I guess there may still be some questions.
Thanks!
spin
I am a first time grower (although I have a reasonable amount of horticultural experience), and I'm having problems controlling high relative humidity in my tent now that we are 10 days into flowering. I think that I have all the tools needed to control this properly, but suspect that I just haven't got it all dialed in correctly yet, so I am hoping some wise heads here can help me.
My setup is in my garage, which is not ideal as my intake air will be cold (current ambient temp is about 13 degrees, but this will drop to 5-8c before harvest). During lights off, I have a very effective small oil filled radiator which kicks in at about 20 degrees. There is nothing I think I can do about the intake air temperature except try to manage it. I am using a fan controller to control my intake and exhaust. This is set to kick in at 25 degrees, although it has an idle speed setting to ensure some exhaust / intake occurs below that temperature. I currently have it set to a moderate idle speed, and I have the balance controller slightly biased toward the exhaust, in order to maintain negative pressure. In addition to that I am using a single 600 watt HID for lighting, which currently gives me plenty of lights-on temperature.
I only bought a RH monitor a few days ago, and was shocked to see the RH at between 70-80% at different times through the day. So yesterday I bought a dehumidifier and put that in the tent as well. The probe of the RH monitor is set at the root zone level of the plants, and is adamant that RH is an average of 75%. I don't know where the gauge on the dehumidifier is, but that is reading closer to 55-60%. But the dehumidifier has been running at full blast all night, and is still not winning the battle, so the electricity usage is also getting to be a bit of a concern.
My feeling is that the RH is higher at the root zone because I have a very dense canopy. I have a 1m x 1m tent containing three sativas, which have been kept low and tight using LST. So they are not too high but are nicely filling the width and depth, to the extent that I may need to do some trimming soon to stop any leaves sticking to the sides. We are almost 2 weeks into flowering and some lovely looking flowers are starting to form. But I am concerned about root rot, and possible later bud rot.
The thoughts I have currently are:
1. I only bought the dehumidifier yesterday - perhaps it will take a little while to get things under control (I know this is probably wishful thinking, but hey).
2. Am I overwatering? The plants are taking a total of about 6lt per day between them. They don't look or feel overwatered, but perhaps they could manage on less. I am using coco by the way.
3. I could completely kill the intake fan, so that all intake would be passive. Maybe this would reduce the amount of cold air coming in.
4. I will buy another fan today and aim it directly at the root zone to try to make the RH more equal throughout the tent. (update, I already did this and there is no noticable difference)
5. If there was no other option I could potentially remove the radiator and place it instead in a sort of pre-chamber, so that I wasn't heating the tent directly, but heating the intake air. However this would cost me time, space and money, and so I'd appreciate opinions on whether it would be worthwhile before I go ahead and do it.
6. Lastly, would it be more sensible to simply cull two of my plants? The original intention was always to cull down to a single one, but they've all been really healthy to date and I haven't seen any real need to thin them out. But if that would reduce the transpiration and help keep things more manageable, then it makes sense to me to take one plant all the way to harvest rather than lose all three in the next couple of months to rot. Although there would be tears in my eyes at killing two of my ladies ;-)
Thanks for any suggestions, and sorry for the long post - I wanted to get as much info as possible, but I guess there may still be some questions.
Thanks!
spin