Terrarium Substrate Cooler

Prerequisites

1. The flat base of your enclosure must sit flush against the surface it's set upon — there cannot be any trim pieces on the bottom edges keeping it elevated.
2. The enclosure can only sit upon a solid surface — meaning no holes, slats, or gaps.
3. Ensure adequate space for the reservoir at or above the enclosure's platform, and for the chiller to be lower than the reservoir. See dimensions below.

	Width x Depth x Height
Reservoir	12 x 3 x 4" (30 x 8 x 10cm)
Chiller	12 x 16 x 18" (30 x 40 x 46cm)

Minimum Parts

Substrate Thermometer	5.45
Aquarium Chiller	168.96
Chiller Fittings	8.39
Pad Fittings	3.49
Reservoir Fittings	7.99
Pump Fittings	9.59
Pump Power Supply	6.77
Coolant Pump	18.99	Failed after ~1yr of operation — consider keeping a spare.
Cooling Pad	57.99	Subtract 3" (8cm) from each of your enclosure's footprint dimensions to determine the largest pad that may be used. This ensures enough space for the risers to support the enclosure's weight.
Coolant Reservoir	17.59	Collects air trapped in the cooling loop.
Reservoir Cap	6.59	Seals the reservoir's fill port.
Reservoir Insulation	6.16	Improves thermal performance and limits condensation.
Tubing	7.99	Interconnects the loop's elements.
Tubing Insulation	15.99	Improves thermal performance and limits condensation.
Hose Clamps	5.79	Secures tubing to the barb fittings.
Rubber Risers	10.45	Creates a gap for the cooling pad beneath the enclosure.
1G Distilled Water	2.00	Coolant.
	Total

Optional Upgrades

Silicone Mat	9.99	To protect the surface beneath the cooling pad from condensation if coolant drops below the dew point.
Silicone Tray	14.99	To protect the surface beneath the reservoir from condensation if coolant drops below the dew point.
Damper Pads	12.00	Affixing to the base of the pump reduces vibration noise.
Enclosure Insulation	13.99	To improve thermal performance. Install to any unobstructed surfaces on outside of the enclosure, at and below substrate height.
Substrate Heatsink	14.99	To greatly improve thermal performance by aiding vertical conductivity within substrate, which is also a must if incorporating a drainage layer. Select the largest "width" that the intended substrate depth can hide. Wash to remove machine oils, and place flat face atop the glass directly above cooling pad. Multiple are recommended for most footprints, spaced in parallel with their vertical faces ~4" (10cm) apart. Affix after placement with silicone sealant on only the lengthwise edges of each segment, so as to not insulate the glass/metal interface with either silicone or trapped air.
Basic Substrate Thermostat	18.99	Replaces the substrate thermometer, enabling thermal stability in highly variable ambients by controlling power to the pump and chiller. Ideally combined with the optional substrate heatsink, to shorten the lag between cooling commands and the result. Set the chiller thermostat's target to 34°F (1°C), and the substrate thermostat's differential to its lowest supported value.
Smart Substrate Thermostat	49.99	The same capability and notes as the Basic Substrate Thermostat described above. However, this also supports setting schedules (e.g., day/night and seasonal cycles), can alert to out-of-bound thermals, and charts thermal history.
Time-Delay Outlet	31.99	Protects the chiller from damage if utility power is briefly lost. Install between the outlet and chiller, or between the outlet and substrate thermostat if one's used.
Specialized Coolant	24.99	Coolant alternative, which contains biocide, limits bubbles, and lubricates the pump for a longer life. Up to two liters may be needed, depending on loop length.

Required Tools

Slot Screwdriver	To fasten hose clamps and reservoir cap.
14mm Wrench or Pliers	To fasten G1/4 fittings.
Measuring Tape	To measure for cuts.
Scissors	To cut tubing and insulation.
Small Funnel	To fill reservoir with coolant.
Towel	To soak up any leaked coolant.

Instructions

Prep Chiller

1. Chillers must be kept upright for at least 24 hours before any operation, which ensures that their compressor's oil has settled to a safe level. Failure to allow this time often results in compressor damage.
2. Set aside the pump and tube fittings included with the chiller, as they're incompatible with this use case.
3. Locate two separately-ordered chiller fittings, and place one of the chiller's included o-rings within each.
4. Fasten these two prepped fittings to the top of the chiller.

Prep Cooling Pad

1. With scrissors, cut the fitting off the end of the pad's tubing and discard the included insulation.
2. Cut the pad's remaining tubing to 1" (25mm) lengths and discard the removed lengths.
3. Press the small end of a pad fitting into each of the pad's tubes.

Prep Reservoir

1. Ensure that the reservoir's black end pieces are fully-threaded to the acrylic glass, as they may have loosened during shipping.
2. Identify the end with two holes and affix a reservoir fitting to each. Threads are tight, so double-check that the gaskets squash upon fastening.
3. Affix the reservoir cap to the end with only one hole.

Prep Pump

1. Set aside the pump's included fittings, as they aren't compatible with this use case.
2. Affix the separately-ordered pump fittings and their included o-ring to each of the pump's ports.

Prep Tubing

1. Place the chiller, cooling pad (plastic face upward), reservoir (oriented horizontally), and pump in your planned locations. The reservoir in particular must be at the loop's highest point, as its role is to collect trapped air while the coolant cycles.
2. Cut four lengths of tubing — one between pad and reservoir, pad and chiller, chiller and pump, as well as the reservoir and pump. Lengths should have some slack.
3. Sleeve the tubing's insulation such that all but ~1" (25mm) at each end of the tubes are fully covered. Fitment is tight, so long tubes may require sleeving multiple short lengths of insulation.

Install Tubing

1. Use the now-insulated tubing to connect the pump's side fitting to one on the chiller, and the chiller's remaining fitting to one on the pad. Next, connect the pad to the fitting on the reservoir featuring an internal tube (visible through the acrylic), and then connect the reservoir's second fitting to the pump. These connections are made by pressing the tubing over the fittings' barbs until they're fully covered.
2. Ensure that the reservoir can rotate such that the port connected to the pad is oriented above the one leading to the pump.
3. Open the hose clamps by fully unscrewing them, and then affix to the tubing anywhere it covers a barb fitting.
4. Take a break — this is about to get spicier.

Add Coolant

1. Reassess fittings to confirm that they're sufficiently secure.
2. Plug the pump's power supply into its planned outlet, and be ready to connect it to the pump.
3. Remove reservoir cap and orient the reservoir such that its open port faces up and the tubes are downward, again ensuring that the reservoir is the loop's highest point.
4. Loosely insert a funnel into the open port and add coolant until the reservoir is ~80% full.
5. While maintaining reservoir orientation, connect the pump to its power supply.
6. Coolant should drain from the reservoir, and there will be strange noises as the pump struggles with air pockets. Keep adding coolant to the reservoir and try to maintain a coolant level of at least 80%.
   • If coolant struggles to flow despite maintaining level in the reservoir, this is because of large air pockets trapped in the loop. Manipulate the tubing until the pockets pass through the system, especially by vertically aligning the tube running between the pump and reservoir. The tubes can go back to the intended positions once the filling process is complete.
7. Once the coolant's flow sounds steady and the reservoir maintains at least an 80% coolant level on its own, ensure that this remains the case for at least 2 consecutive minutes.
8. Reaffix the reservoir's cap and set it back in its planned location.
9. Disconnect the pump from power.
10. The loop is now under pressure, so over the next 5 minutes, inspect fittings for leaks and tighten anything suspect.

Add Reservoir Insulation

1. Cut the reservoir insulation to a length of 5.5" (14cm).
2. Sleeve insulation over the reservoir until the coolant is no longer visible.
3. Find the reservoir's clear plastic feet and affix them to the black end caps.
4. Set the reservoir back down, and rotate it such that the port leading to the pad is oriented above the port leading to the pump.

Position Cooling Pad

1. Move cooling pad aside and set the enclosure in its planned location.
2. Place a rubber riser beneath each of the enclosure's four corners, and an additional beneath perimeter spans exceeding ~12" (30cm) — as long as placement won't block sliding of the pad in the following step.
3. Lift one side of the enclosure, and slide only the cooling pad (not the tubes) beneath it.
4. Set the enclosure back down and ensure that each of the risers is taking some of the enclosure's weight. The pad should be compressed against the glass but not taking all of the enclosure's weight.
5. Power the pump back up.

Populate Enclosure

1. Add substrate if you haven't already, and keep in mind that depth is a factor in temperature deltas. A height gradient will create a thermal gradient, which may or may not be desireable.
2. Install thermometer with its probe above the cooling pad on the substrate's surface.

Configure Chiller

1. Power the chiller on and set its thermostat differential to 4°F (2°C).
2. Set a coolant temperature based on deltas in the following section on Performance.
3. Take a break for ~6 hours to allow the enclosure's thermals to settle.

Tune System

1. Reassess fittings for leaks and tighten anything suspect. Some condensation is normal if coolant drops below the dew point.
2. Begin adjusting the coolant's temperature to reach the desired substrate temperature, and allow ~2 hours before reassessing these adjustments.

Troubleshooting