Common Questions About Your New Glycol Chiller

What size disconnect and breaker should I install? 

Sizing the electrical service is usually the first question we are asked. Manufacturers of chillers provide specification stickers, also known as data plates, that are generally located on the electrical enclosure. The spec sticker will list the electrical requirements used to size the main breaker and the service disconnect for the chiller. On G&D’s spec sticker we list the MCA and MOC. These stand for minimum circuit ampacity and maximum overcurrent protection, respectively. 

The chiller’s electrical service must be able to handle the MCA at a minimum, and the breaker must trip at or below the MOC. To say this another way, the breaker and disconnect you install should be no smaller than the MCA and also no larger than the MOC to provide adequate protection for the equipment. 

What are the requirements for chiller placement and clearances? 

Chiller placement is another common question. Refer to the applicable safety and civil codes at your location to ensure you won’t run into any issues on that front. From our perspective, the chiller simply needs to be located on a level surface capable of supporting its weight. It needs to be accessible for serviceability. The backside of the chiller, also known as “the side with the condenser,” should have a minimum clearance of 2-3 feet from any nearby walls. The louvered access panel side should be open to free space with nothing in front of the chiller that could obstruct the hot air it exhausts. If a fence is needed around the chiller, we recommend installing a chain link fence with no slats so the hot air can pass through the fence freely. Installing the chiller on a rooftop is often a good option, assuming the roof can support its weight and an appropriate supporting pad can be constructed. If you have no choice but to install your chiller indoors, contact the manufacturer to discuss the additional installation requirements.

How do I calculate how much glycol I will need for my chiller? 

Calculating glycol can seem intimidating but is a fairly straightforward process. First you will need to calculate the full capacity of the chilling system. This will include the chiller reservoir, process piping, and tank jacket capacity. The reservoir capacity should be located on your chiller’s spec sticker. Calculate your total process pipe capacity by taking the total length of pipe and using pipe volume calculator on the internet. Lastly, if your tank does not list the jacket capacity on it, reach out to the tank manufacturer for those details. 

Once you have determined the total volume of coolant your system will require, take this value and multiply it by the manufacturers recommended glycol %. The result is the amount of pure propylene glycol you will need to purchase. This pure propylene glycol will then be mixed with clean water to achieve the required glycol %. At that point, the resulting volume of coolant mixture should be able to complete fill the chilling system. Note: Inhibited propylene glycol is typically sold as 97% pure propylene glycol, with the remaining 3% consisting of rust and corrosion inhibitors that protect the internals of the piping system. Pay attention to the type of glycol you are purchasing and adjust the mixture accordingly.

Does my chiller have a bypass valve? What is it used for and what pressure should I see? 

Bypass valves and pump pressure are concerns for many people. Some manufacturers have internal bypass valves installed in the chiller and some do not. One misconception is the only purpose of a bypass valve is to regulate the pressure of the glycol in the supply line leaving the chiller. This is not always true. On a chiller system that has only one pump, the bypass valve is used to always maintain flow through the chiller’s heat exchanger (evaporator). The secondary purpose of the valve in this case is to regulate the glycol supply pressure. On a two-pump system that has a dedicated process pump, the bypass valve is used only to regulate glycol supply pressure.

The pressure of the glycol leaving the chiller should not exceed the pressure ratings of your tank jackets. An adjustable bypass valve is ideal. At G&D we factory set the bypass valve at a pressure of 20 psi by default, when the valve is in full bypass mode. However, with the chiller supply and return valves open to your process, the glycol pressure will likely drop below this 20 psi. This is expected behavior and is not usually a cause for concern. It happens because, with the glycol flowing through your system, there is less restriction of glycol flow (lower pressure drop) compared to full bypass mode, where all of the glycol flow is being forced through the bypass valve and back into the reservoir. If you are not sure if your chiller contains an internal bypass valve, or how the bypass valve should be configured, contact your chiller manufacturer. 

Why is a wye strainer important for a glycol chiller? 

A main source of protection for your chiller is a wye strainer. This should be installed on the return line piping just before the process fluid enters back into the reservoir. If you do not have a wye strainer installed on the return line, any contaminants from the install process left in the piping will end up collecting in the chiller reservoir. Then it is only a matter of time before the contaminants in the reservoir are pumped into your chiller’s heat exchanger and cause catastrophic damage. Installing a 20 mesh wye strainer on the return line is recommended in most cases.