Size the Chiller for the Hottest Saturday, Not the Empty Tank on Monday Morning
The right seafood display tank chiller is selected from heat load, not tank volume alone. Before approving a unit, I want six numbers: total system water volume, seafood species and biomass, target water temperature, highest realistic room temperature, required pull-down time, and heat added by pumps, lighting and the surrounding environment .
For saltwater systems, I would also specify a titanium water-side heat exchanger and verify the chiller's cooling capacity at the actual operating conditions—not simply accept “1 HP” or “suitable for 1,000 liters.”
This matters because temperature changes two things at once. It affects the seafood directly, and it changes its oxygen demand. FAO data on live-fish handling illustrates the relationship clearly: for common carp in the cited example, oxygen consumption rose from 17 mg O₂/kg/h at 10°C to 50 mg/kg/h at 20°C and 105 mg/kg/h at 30°C . The exact values differ by species, but the direction does not: warmer animals generally consume oxygen faster.
For a restaurant or supermarket, cooling is therefore not an accessory.
It is part of the life-support system.
The 1,000-Liter Question I Don't Answer Immediately
A buyer emails:
“We have a 1,000 L lobster tank. What HP chiller do we need?”
I can give a rough range.
I shouldn't give a final answer.
Imagine two identical 1,000-liter systems.
Tank A: air-conditioned restaurant, 23°C room, target water 10°C.
Tank B: seafood market beside an open kitchen, 34°C summer ambient, strong display lighting, target water 10°C.
Same liters.
Tank B has to continuously fight a much larger temperature difference.
Now add a fresh seafood delivery whose transport water arrives several degrees above the tank setpoint. The chiller suddenly has two jobs:
maintain temperature + remove the new thermal load quickly enough.
That second job is why an apparently adequate chiller can spend hours running at 100% after every delivery.
Current commercial seafood cooling guidance likewise sizes from water volume, target temperature, maximum ambient temperature, livestock load, pumps, lighting and required pull-down time rather than volume alone.
Do the Pull-Down Calculation Before Looking at Horsepower
Here is the calculation I use to make the problem visible.
Suppose:
Water volume = 1,000 L ≈ 1,000 kg
Starting temperature = 18°C
Target = 10°C
So:
ΔT = 8°C
Water's specific heat is approximately 4.186 kJ/kg·°C .
The theoretical heat that must be removed is:
Q = m × c × ΔT
Q = 1,000 × 4.186 × 8
= 33,488 kJ ≈ 9.3 kWh of thermal energy
If you want that pull-down completed in two hours, the theoretical average cooling requirement is already about:
9.3 ÷ 2 = 4.65 kW
And that is before adding continuing heat gain from the room, pumps, lights, livestock and imperfect insulation.
That is why I do not like selecting a commercial chiller from:
“1 HP per X liters.”
Useful for rough screening.
Not enough for a purchase order.
HP Is Not Cooling Capacity
This is the line I would circle on an RFQ.
Horsepower and refrigeration capacity are not interchangeable specifications.
HP may describe compressor or motor class. What the tank actually needs is heat removal capacity , preferably stated in kW or BTU/h at defined entering-water and ambient-air conditions .
Ask the supplier:
“How many kW of cooling does this unit deliver when the room is 35°C and my water setpoint is 10°C?”
That answer is much more useful than:
“2 HP, suitable for 1,200 liters.”
TECO makes the same point indirectly in its current chiller specifications: its volume ratings are tied to stated assumptions— 25°C water, 30°C ambient and 0.2 W/L heat load —rather than presenting liters as an unconditional capacity.
A liter rating without test conditions is only half a rating.
Saltwater Gets a Vote on the Heat Exchanger
For a marine seafood display, I would specify titanium on the water side.
Not “metal heat exchanger.”
Titanium.
Commercial aquarium chillers commonly use titanium specifically because the heat exchanger remains in continuous contact with saltwater; current marine chiller manufacturers explicitly identify titanium heat exchangers as part of their saltwater designs.
This is one area where saving money in the BOM can create a much more expensive service problem later.
The heat exchanger sits where refrigeration and livestock water meet.
I want that material written into the Ruibit project specification, not agreed verbally during quotation.
Flow Through the Chiller Has a Window
Bigger circulation is not automatically better.
Water passing too quickly through a heat exchanger spends less time there; inadequate flow creates a different set of heat-transfer and operating problems. Chiller manufacturers therefore specify operating flow ranges, and current aquarium-chiller guidance recommends matching measured system flow to the unit's required range rather than using the pump's zero-head number.
For procurement, ask for:
minimum chiller flow
recommended flow
maximum flow
then calculate the actual plumbing condition.
A pump marked 8,000 L/h may not deliver 8,000 L/h after 1.5 meters of lift, elbows, valves, filters and the heat exchanger itself.
The chiller only knows the water that actually reaches it.
I Would Buy Margin, but Not a Monster
Undersizing is obvious: the compressor runs continuously and the tank cannot hold setpoint during peak conditions.
Oversizing has its own problems.
A badly matched fixed-speed unit may satisfy the thermostat too quickly and cycle on and off excessively. Good control design, including inverter capacity modulation where appropriate, can reduce this problem by matching cooling output more closely to changing load.
For a high-value seafood system, I am also interested in redundancy , not merely oversizing.
If one enormous chiller fails, cooling capacity becomes zero.
For a large supermarket or seafood market, two smaller circuits may offer a more useful failure strategy, provided the hydraulic and control design is correct.
That decision depends on the value of the live inventory and the financial consequence of downtime.
The Chiller RFQ I Would Send to Ruibit
I would not write:
1,000 L seafood tank — include 2 HP chiller.
I would write:
Total circulating water:
1,000 L
Species:
lobster / crab / marine fish / other
Maximum live biomass:
___ kg
Target water temperature:
___ °C
Maximum design ambient:
___ °C
Maximum incoming water/product temperature:
___ °C
Required pull-down time:
___ hours
Cooling capacity:
supplier to state kW/BTU/h at design conditions
Water-side heat exchanger:
titanium
Required water flow:
supplier to declare min/nominal/max
Temperature control accuracy:
declared
Condenser ventilation clearance:
declared
High/low-pressure protection:
required
Auto-restart after power interruption:
state behavior
Compressor type:
declared
Refrigerant:
declared for destination-market review
Redundancy:
evaluate for high-value/high-load projects
Ruibit already publishes a seafood-chiller guide emphasizing titanium heat exchangers, ambient conditions, livestock load, pump heat and real cooling requirements rather than tank volume alone. The final values, however, should come from the actual project heat-load calculation.
The Chiller Is Really Buying You Time
At 6 p.m. the restaurant is full.
The seafood delivery arrived warm.
The kitchen is hotter than it was during commissioning.
The pumps have been running all day.
That is when the refrigeration system finally tells you whether the sizing spreadsheet was honest.
I don't want the temperature controller showing 10°C because the tank happened to be empty during the factory test.
I want it holding 10°C when the system is carrying its largest realistic thermal and biological load .
So don't ask only:
“How many horsepower for 1,000 liters?”
Ask:
“How much heat must this system remove on the worst operating day, and how quickly must it remove it?”
Answer that correctly, and the chiller size usually stops being a guess.
