What is USRT and How to Calculate the Right Cooling Capacity for Your Chiller？

The term refrigeration ton is commonly used, and mostly used, in North America. It’s a unit of measurement for the cooling capacity of a refrigeration machine. It has a few variants, and it’s sometimes called a ton of refrigeration or just RT for short.

The term refrigeration ton is a little bit confusing to many people. It has nothing to do with the weight of the machine. It only relates to the amount of cooling that the machine can produce.

The term used to be used in many other countries, but the majority of the world has switched over to SI metric units of kilowatts of cooling. However, some people and manufacturers will still refer to equipment rated in refrigeration tons.

If you’re outside North America and have some older refrigeration equipment on site, then this will likely be noted in refrigeration tons. If you’re working in North America then you’ll often see large refrigeration plants, such as chillers, referred to in refrigeration tons. Whereas smaller units are typically rated in BTUs.

	kcal/h	BTU/h	USRT	w
1 kcal/h	/	3.968	0.00033069	1.163
1 BTU/h	0.252	/	0.00008333	0.2931
1 USRT	3024	12000	/	3517
1 w	0.8598	3.412	0.00028434	/

BTU is an acronym. It stands for British Thermal Unit. It is a form of measuring energy. 1 BTU is the amount of energy required to increase the temperature of one pound of water by 1 °F. It is most frequently used when talking about small capacity chiller units.

One kilocalorie per hour is equal to one kilocalorie, or 1,000 times the energy needed to heat one gram of water 1 °C, for one hour.

Kilocalories per hour can be abbreviated as kcal/h; for example, 1 kilocalorie per hour can be written as 1 kcal/h.

In formal expressions, the slash, or solidus (/), is used to separate units used to indicate division in an expression.

A kilowatt is simply a measure of how much power an electric appliance consumes—it’s ­­1,000 watts to be exact. You can quickly convert watts (W) to kilowatts (kW) by diving your wattage by 1,000:

A kilowatt-hour measures the energy an appliance uses in kilowatts per hour. For example, if you clean your floors with a 1,000-watt vacuum cleaner for one hour, you consume 1 kWh of energy.

1. Air-cooled Or Water-cooled

Air-cooled chillers use a condenser that is similar to the “radiators” in a car. They use a fan to force air through the refrigerant coil. Unless they are specifically designed for high ambient conditions, air-cooled condensers need to operate effectively at an ambient temperature of 35°C (95°F) or less.

Air-cooled chillers require less maintenance than water-cooled chiller units.

• Air-cooled chillers do not require cooling towers.
• Easier to install compared with a water-cooled chiller.

Water-cooled chillers function in the same way as air-cooled chillers but require two steps to complete the transfer of heat. First, heat enters the condenser water from the refrigerant vapor. The warm condenser water is then pumped to the cooling tower, where the heat from the process is eventually vented to the atmosphere.

Advantages of water-cooled chiller:

• Higher COP(Coefficient Of Performance).
• Lower cost on power for the same cooling capacity.
• Have a longer lifespan.
• Relatively quieter than air-cooled chillers.
• Provide more consistent cooling performance.

2. Cooling capacity

How to calculate the cooling capacity I need?

Let’s see the below formula.

• Calculate Temperature Differential = Incoming Water Temperature (°c) – Outlet Chilled Water Temperature(°c)
• Water flow rate that you need per hour(m³/hour)
• Get in tons of cooling capacity = Water Flow Rate x Temperature Differential ÷ 0.86 ÷ 3.517
• Oversize the chiller by 20% Ideal Size in Tons = Tons x 1.2
• You have the ideal size for your needs.

Fill out our quick sizing form and we will be able to provide you with the perfect cooling capacity.

If you are not sure how to choose the cooling capacity, please contact us.