Humidity spike at lights on

[lyzer]

I've read about humidity spikes at lights out, but I am currently experiencing a big humidity spike at lights on.

Week 3 into flower running RDWC and finding that whenever the lights turn on the humidity spikes to 80+. At the same time as the lights come on the AC changes from a target temp of 70 to 78 degrees. The room is sealed and with the dehumidifier set to 45%. All other times, including lights out, the humidity is maintained almost perfectly.

Any ideas as to what's causing the RH to spike? I thought RH went down as Temp increases.

 

[Dontjudgeme]

I've read about humidity spikes at lights out, but I am currently experiencing a big humidity spike at lights on.

Week 3 into flower running RDWC and finding that whenever the lights turn on the humidity spikes to 80+. At the same time as the lights come on the AC changes from a target temp of 70 to 78 degrees. The room is sealed and with the dehumidifier set to 45%. All other times, including lights out, the humidity is maintained almost perfectly.

Any ideas as to what's causing the RH to spike? I thought RH went down as Temp increases.

That’s a head scratcher. I must say I’ve never experienced that. Not sure that DWC has anything to do with it, but that’s strange.

 

[athlete]

...so the dehumidifier ... isn't working?

 

[SnidleyBluntash]

When lights come on the plant begins transpiration, making more humidity.

The AC doesn’t come on until it’s a bit warmer, AC also drys air.

 

[lyzer]

...so the dehumidifier ... isn't working?

The dehu seems to be working (pumping out hot air, producing water), but maybe it simply can't handle the rapid spike in the beginning? I've got a new humidity controller on the way which might improve things. Alternatively I can add another dehu and see if that makes a difference, or stair-step the AC target slower so everything isn't adjusting all at once.

 

[ChrispyCritter]

Normally humidity goes up after lights out ... As temp drops from lights not on.

 

[JoeBlow5823]

I would say the AC not running is the issue.... AC dries the air. Dehumidifiers work on the same principle of air conditioners but the condenser (the hot part) is not cooled in any way, the cold air from the evaporator is just reheated by the condenser.

 

[bEelzeBosS]

How long from the spike until its back down? If we're talking 30 min or less I wouldn't worry about it.

 

[lyzer]

It's relatively short, probably about 20 min from spike to the levels settling back down. I stair-stepped the AC on the last lights-on and you can see the initial spike of humidity and then another smaller spike in the charts below. Tomorrow I'm going to try just letting the lights kick on for an hour before raising the temp and see if that let's things run a little smoother with the humidity.

This was not an issue on the last run and the dehu was in a different location so I'm wondering if that's also part of the issue. Moving the humidity sensor with the new controller would likely alleviate that, still waiting on that to deliver.

 

[calvin.m16]

Humidity spikes lights on is totally normal. Your plants are firing up. It's kinda like when you wake up you take a piss probably. Same concept. Weed plants are just like us in some ways. You may want to look into a better quality dehumidifier such as a Quest and size according to their recommendation.

Personally since I've gotten a Quest Dual 225 dehumidifier I don't have swings in my flower room it stays between 43-45% at all times. Haven't seen powdery mildew since installing it and resolving the smaller dehumidifier units not being good enough.

 

[JoeBlow5823]

probably about 20 min from spike to the levels settling back down

Dont worry about it, 20 min is nothing. Think of it like "morning dew"

 

[Rurumo]

could it be that you or someone else is taking a shower in the morning? Or maybe making tea on the stove or something? Simple things can dump a lot of moisture into the air.

 

[Dontjudgeme]

Like others have mentioned, that short period of time won’t do anything, especially if you have sufficient air flow. Most decent size dehueys actually have built in therms on them. Mine is way more accurate then my controller, which is why I don’t have mine connected to my dehuey. My controller is only controlling my humidifier. But I think you should be ok.