HVAC_Marc
I keep a marine tank with hard corals (SPS - agreed and knows by marine hobbyist as fussy corals that can die within a few hrs if conditions are not right) - they require water temp to be in the region of 26 Deg C. I live in the tropics where ambient temp hit 35 Deg C.
I have similar setup but the easy way out of this is to go back to a simple system. I have given up on the "specially" built for aquarium systems as they are just too compact to be efficient. Here is what I have done
1. 1.5 outdoor unit (standard home units) - non inverter type
2. titanium coil
3. A pump with flowrate calculated based on - required cycle time and tube size / coil length - (titanium coil as well and I estimated the length based on the tube size and volume of the cooling casing)
4. A temperature controller set to cut in at 27 Deg C and cut off at 26 Deg C. I have alarms etc.
5. Place coil and outdoor unit as close as possible and shortest route to the tank.
My compressor cycles on/off about 15 mins interval and runs for about 4 to 5 mins.
This installation keeps things simple - the compressor can be easily be replaced and all other items as well. If i am not confident of the unit, I just replace the outdoor unit because my lifestock is more precious and i leave the troubleshooting for another day ( I have a spare outdoor ready to be installed at short notice).
Since you are advising your client, this is the way to go :
1. Get all the heat load that the tank will have - internal / external pumps (internal pumps dumps all its heat load (i.e W, uv, heating, etc - att consumption ) into the water and externals probably about 80% (aquarium pumps are not efficient)
2. Lighting heat load - you have to design for the worse case - so assume all lamps are turned on (i used 2 x 500 W metal halides and they are a 6 inches from water surface and are placed with reflectors) - So i assume all 500 W heat is channeled to the water.
3. Take the worse ambient heat possible.
Get the heat load - work out your desired cycle time and size the outdoor. The titanium cooling coils have variable sizes - it depends how precise you want to keep the water in the fixed temperature range
Hope the above helps in your future works with aquariums