Harvest - Lettuce Temperature Problem [Under Investigation]

Just curious, do these units have multiple wall warts or is it just a single plug with the power supplies inside?  Normally the submergible pumps use an AC motor and the rest needs DC.    So if a  single external PS then there would be the need to rectify and regulate inside.    I assume they are wall warts as the PS with a 40w LED panel produces a lot of heat.  Having that PS inside would really heat things up.

There is only one wall plug (edit: wall Wart) for the Harvest. The plug goes into the base. There is a detachable cable from the reservoir pump that goes into the base. And the light fixture connects to the base with the extendible post, I assume it has a wire running up the post and all of the electronics for power management is in the base.

Maybe that explains why the base was feeling warm while the light is on. I do believe that the Harvest is 20W if I remember correctly.

Day 3 - Pumps on, Lights off



The pumps were turned on at 10:00 pm yesterday night and ran all day on the built-in schedule of 5 minutes on, 25 minutes off.

There is a temperature spike at 6am this morning when we had the heater on briefly, but I don't know what else to make of it. 

On the one hand, the temperature did not drop alongside air temperature last night like it did the day before. The local weather station says that this morning was 10% more humid than yesterday (70-80% relative humidity vs. 60-70% between midnight and 6am) but I'm not sure if that's why.

On the other hand, it looks like the temperature still stabilized below room temperature during the day today when the pumps were still on.

Yes airscapes you're right this is short and I should run this longer! It is only on for the default 5mins on 25 mins off so I didn't expect there to be a huge difference though. Is your 2 degree difference 24 hours on or on a shorter schedule?

Unfortunately I need to get some basic answers before the Aerogarden return slip runs out, so I am truncating the study to confirm primarily whether the Old Harvest is defective or not. Maybe after figuring it out I'll run it again and see what happens if just the pumps are on for longer.

As I was reading I was thinking location and as I read on ...  you stated you were going to swap them

Eureka! There's been a new development in the Aerogarden heat theory  

The last 4 days I switched the locations back to the original position (Old Harvest in the corner) and measured with lights & pumps on without disturbing the system. The temperatures read the same!  


This means, on day 4 when the gardens were in the same positions, the ~1 C difference between the gardens was due to the pump being on and not due to location as we previously suspected.

Thumbnail of Day 4:

However, such a large difference in pump-on vs. pump-off temperatures is only apparent during the lights-on period. Previously when the pumps were on, and the lights were off, the water was still below air temperature (Day 3):


I think this means that when the pump is on, and the lights are on, the water is collecting heat from the deck, which is warmed by the light like this:

So what I think is - even though the pump itself contributes a small amount of heat using the 5 mins on, 25 mins off schedule, having the pump on can contribute a fair amount to heating during the lights-on period by pushing the water through the warmed deck.

If this is true, then having a piece of insulation on top of the deck might be able to solve both problems at once!?

x2!

belugaleuca, earlier I meant to say that I really like your colorful diagram of the heat transfers in the Bounty! It makes your point very clear.