Chillers vs. Water Recirculators

What’s the difference between a chiller and a water recirculator? The major difference between the two is whether or not the unit contains a refrigerant.

An actual CHILLER will have a compressor and a pump to actively remove heat from the liquid flowing through it, using a refrigerant (much the same way a refrigerator or a drinking fountain works).

A WATER RECIRCULATOR does just that; it recirculates coolant through a radiator (much like the radiator in your car). It passively cools liquid by using a heat exchanger and cooling fins.

Do I need a chiller or a recirculator?

There is no simple rule to determine whether you need a chiller or a recirculator. If you are welding in high production, welding aluminum, or other important or exotic applications, a chiller is the clear choice. If the production rate is low, or the machine is used infrequently, a recirculator is probably fine. Please contact us for details.

Chiller Sizing

A general rule for sizing a chiller is that, for every 100KVA of welder, you should have about a 1-ton chiller. For example, if you want to cool 4 welders that are 100KVA each, you will need a 4-ton chiller. If you want to cool a 300KVA machine, you will need a 3-ton chiller. See below for further sizing details.

BTU calculations, with duty cycle taken into account

If you want a more accurate method for determining your chiller or recirculator size, you can use the formulas below.

To calculate BTU’s per hour of a resistance welder:

Resistance Welding: BTU/hr = (welder KVA) * (duty cycle) * (.85) * (.6) * 3415 BTU/hr

Resistance Welding: BTU/hr = (Welder KVA) * (Duty Cycle) * (Eff Power Supply) * (Eff Heat Collection) * 3415

Eff. Power Supply: the % of power out to power input; typically 85%

Eff. Heat Collection: the % of heat absorbed by the chilling water; Varies 50%-75% est

To calculate duty cycle:
(weld time on) / (elapsed time) = duty cycle

Say you are averaging 4 welds per minute on a 100KVA welder with a weld time of 15 cycles (250ms).

duty cycle = [(number of welds) x (weld time, in cycles)] / 3600
duty cycle = [4 * 15] / 3600 = 0.016667 = 1.67%
BTU/hr = 100 * 0.8 * 0.016667 *0.6 * 3415 = 2732 BTU/hr

Cost Savings

Historically, it was a common practice to use city water for cooling.  The waste water was then run down the drain.  There are a number of reasons this practice has largely gone away.

  • City water can be too cold, often below dew point temperature.  This can cause your electronics (SCR, diodes, transformer, IGBT, other) to “sweat”, a.k.a., develop condensation, and cause an electrical short.  This is one of the more common causes of a welding system failure.  (Confusingly, you may actually need to turn the set-point temperature of your chiller up as the temperature rises… which can be counterintuitive.  This is to keep your chiller at or near dew point temperature).
  • In certain climates, water is a quickly becoming a limited resource.  You can add significant long-term costs by simply running water down the drain and paying both water and sewer costs.

**graphic source: TJ Snow

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