Trouble Controlling Nutrient Reservoir Temperature

by Mark
(Cincinnati)

Hi,

I'm having an unexpected problem with rising temperatures in
my nutrient reservoir. I say its unexpected because the
temperature in the grow room is 63 degrees F. The grow
room is in the back corner of the basement and I've
closed the HVAC vents and shut the door.


When I first mixed the 30 gallons of nutrients, the water
temp was about 52 degrees. Its been a cold winter. They
were drifting up, but I thought it was just trying to
equalize to the room temperature. It hit 63 and has kept
climbing.

Its now around 76 degrees and I'm trying to lower it with
blue ice packs.

Question - what is the maximum safe temperature the
nutrient solution can be at?

I'm trying to understand where the heat may be coming from.
For instance. Does the air pump add heat to the nutrients?
I've taken readings of the temperature and it can climb
a 1/2 a degree in an hour without any nutrient pumping.

Then, during a nutrient pumping, the temperature of 30
gallons of nutrient can increase 3 degrees. I just had
my 6PM feeding and the temperature went from 68.9 to
72.0. The absolute temperature of the thermometer may
be off, but the change in temperature should be accurate.

I feed twice per day at 6am and 6pm. I understand why the
return nutrients would be warmer during the evening feeding.
The grow chamber has been between 76 and 79 degrees for
12 hours. But, when I measured the temperature of the
return nutrients, they were at 84 degrees, higher than the
ambient temperature of the grow chamber. I thought about the
black tubing acting as a solar shower. The grow
light shining on the 1/2 ID black tubing could heat the
water in the tubing higher than the ambient temperature.
So, I wrapped them in the reflective foil I used on the
walls of the grow chamber to reflect the light away. Did
not help.

At midnight, when the grow lights shut off for six hours,
I run an exhaust fan until the temperature in the chamber
drops to 68 degrees. The fan will keep coming on all night
to keep the temps below 68 degrees. The low temperatures
recorded each day is 66 degrees, so that is working. The
nutrient reserve in the bottom of the Dutch buckets should
cool to 66 during the six hours of night and the grow
media should also cool so that the first feeding of the
day at 6am right when the lights come on should not pick
up any heat from the grow chamber. But, the temp of my
reservoir will increase by 3 degrees.

Does the submersible pump add much heat when its
operating?

Does anyone have any ideas where the additional heat is
coming from?

Thanks,

Mark

Comments for Trouble Controlling Nutrient Reservoir Temperature

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Mar 18, 2014
Reservoir heat
by: Memwl

Does the submersible pump add much heat when its
operating?

Does anyone have any ideas where the additional heat is
coming from?

You answered your question
The pump will add a lot of heat, You can upsize your reservoir or try a smaller pump, I had a monster running a system once the pump was a huge one, I figured the bigger the more flow and aeration bit it made the water hot, also look into the pump that sits outside non submersible.
This si a guess from my own experience
others my differ.

Mar 23, 2014
Reservoir Heat: Solved
by: Mark

I think my problem is partially solved. The device
from AcuRite I was using to monitor the temperature
was WAY off. It was reading at least 15 degrees
high. I could never understand how a reservoir at
75 degrees sitting in a basement that is 60 degrees
would drift up two degrees per day when the pump
wasn't running. The real temperature of the
reservoir was probably in the low 50's and moving
up to the room ambient temperature. But, my
monitor claimed the reservoir was in the low
70's.

I bought a new device from Lacrosse which, so far,
is really nice. They call it LaCrosse Alerts.
Device sends ambient temperature/humidity and,
optionally, the temperature on an external probe
to their server over the internet. Then, you go
to their website, login, and you can see the data.
You can set different sampling periods, they
give you the data in graphs, tables, you can
download it, etc.

The device connects via radio signals to the
gateway which connects to your internet. Each
gateway can support five devices.

The one downaide is the way their support plan
works. You get a year free, then its a
subscription service. Instead of a
service plan per gateway, its per device. So,
if you have five devices connected to the gateway,
you have to buy five service plans. The
discount on longer term service plans is
aggressive, so if you sign up for a three year
plan, it bends the cost curve down. Its
roughly $11, $20, and $28 for one, two, or
three years, respectively. But, you have to
buy one per device.

You can set high and low alert points for each
data point (ambient temp, ambient humidity, and
remote temp) and receive email and text alerts.
Its probably worth it so I can see my
environmentals on my cell phone.

Thanks,

Mark

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