When sizing your glycol feeder, you will want to think about the overall volume of fluid in your closed-loop system, expected makeup, pressure, glycol concentration and pump capacity. The tank will need to have enough pre-mixed solution stored for normal operation between services. The pump must be able to push the required volume of fluid.
Selecting a larger or smaller glycol feeder depending on size of building or piping can cause issues. A small commercial heating loop will have different requirements than a large industrial cooling system.
These are often used in chilled water, hydronic heating and industrial process cooling systems. They are used to provide automatic makeup to keep your fluid levels and pressure up. By using the correct size, you will reduce the need to manually top up the solution, provide consistent glycol concentration and protect your equipment.
1. Understanding what a Glycol Feeder Does
Before selecting the correct size it can be helpful to understand what a glycol feeder does. The unit will contain a tank, pump, pressure switches, valves and pipework. Some models will also contain a low level switch, alarm and pressure gauge.
The unit connects to your closed loop system. When the pressure drops below the set point, the pump will add further glycol solution.
This helps to maintain correct fluid levels when there is a small amount of loss due to leaks or maintenance. It will also reduce air ingress.
Generally, glycol feeders are used for makeup and not for completely emptying a system. The Neptune GE-50-1 states the unit is for glycol makeup only and should not be used to fill large systems due to the pump having a relatively low flow rate. The tank will be 55 gallons. Always check what the unit is for and any limitations.
2. Calculating volume
The first thing you should look at is the volume of fluid in your closed loop system. This will help you understand how much glycol you will need to have in stock to complete any makeup. Think about all the components that will contain fluid.
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Piping (supply and return)
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Chillers/Boilers
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Heat Exchangers
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Air Handling Unit Coils
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Pumps
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Buffer Tanks
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Process Equipment
Try to use any documentation you have for the equipment, calculate the piping and look at commissioning documents. If your system already exists you may need to calculate how much each component can hold.
For example, your commercial chilled water loop may have 1,500 gallons of fluid. An industrial process loop could have far more.
The volume of your system will not necessarily mean you need a larger tank. Glycol feeders are not generally expected to have enough fluid to completely refill your loop. The tank will provide you with a source of glycol makeup. How big the tank is will depend on how much fluid you expect to lose and how regularly you can check and top up.
3. Expected makeup
Next you should consider how much glycol solution you will need.
In general, your closed loop system will not lose much fluid. You may need to complete some makeup after maintenance or replacing components, but if you are regularly completing makeup, there may be an issue with a leak or something else.
Look at your maintenance history, how much you have topped up previously, pressure and service reports to get an idea of the amount you will use.
If your system has historically used around 4 gallons of makeup per month and the staff at the facility plan on checking and topping up every 2 months, you will expect to use around 8 gallons.
Your tank will need to be large enough to provide the required amount of usable glycol. You will also want to have some extra in case of any issues. You will also need to consider the manufacturer's guidelines on how full you should fill the tank.
This will give facility managers a better starting point than just using a larger glycol feeder due to the system having a large volume. If you are suddenly using a lot more glycol, investigate why. This is often due to a leak. Valves, piping joints, pump seals, heat exchangers, etc.
A larger tank may mean you don’t have to top up as often, but it will not fix the issue.
4. Selecting the correct tank size
Now you know the volume of your system and how much makeup you expect, you can look at the tank sizes available.
A glycol feed tank should hold enough solution to cover the expected makeup requirement between inspections without creating unnecessary storage or installation problems. Larger facilities may need more capacity, while smaller commercial systems can often operate with compact equipment.
Bypass Feeder offer several options from J.L. Wingert and Neptune. Below are examples of what we currently offer:
Small 10 gallon systems: The J.L. Wingert CGL10 unit is ideal for smaller commercial and closed loop systems. The tank is compact, making it perfect for areas with limited space in the equipment room.
Small 17 gallon systems: The J.L. Wingert CGL17 unit provides more storage but keeps the compact design. This unit is listed for use in commercial, institutional and light industrial closed loop systems.
Large 55 gallon systems: The J.L. Wingert GL50-E1-1 unit has a larger polyethene tank. This unit provides automatic glycol makeup and low-level control. This is ideal for more demanding commercial and industrial systems.
These are examples of the different sizes available. The volume will not necessarily be a recommendation for certain-sized buildings. Two systems with the same volume may have very different makeup requirements, pressures and service intervals.
Look at the usable volume. Some manufacturers will have guidelines on how full you can fill the tank to ensure the equipment works correctly. For example, Neptune recommends filling the 55-gallon GE-50-1 unit to 2/3 full.
5. Checking pump capacity and flow rate
Alongside the tank size, you will need to ensure the pump can provide the correct flow rate. Larger tanks do not mean a more powerful pump. High pump capacity doesn’t mean you need a large tank.
Check the following:
Flow rate: Ensure the pump can provide the required flow rate for your makeup. Check the rated flow rate.
Pressure: The pump will need to provide the correct pressure to push the fluid through your system. The rated flow rate can vary depending on the pressure and fluid.
Fluid compatibility: Different concentrations and temperatures can affect the viscosity of glycol solutions. Ensure the pump is rated for the solution you are using.
Operation: Ensure the pump is suitable for intermittent operation. Don’t select a unit that needs to run constantly.
Neptune has published details on the GFS pumps. They have a standard flow rate of approx 1.6GPM at 100 PSI. They also have an option for a low profile pump with a flow rate of approx 3.6GPM at 100 PSI. This shows the importance of considering the pump configuration. Always check the exact model.
6. Pressure compatibility
The glycol feeder will need to be compatible with the pressure of your closed loop system. The pump, pressure switch, relief valve and pipework/fittings will need to be rated correctly.
First determine what the normal pressure is and what pressure is required at the point of connection. Compare this to the rated pump pressure and pressure settings from the manufacturer.
Many automatic feeders will have adjustable pressure switches. When the pressure drops below the minimum setting, the pump will turn on. When the pressure reaches the maximum, it will turn off.
For example, the Neptune GFS feeder has a factory setting of 20 PSI min and 40 PSI max. The relief valve is set to 100 PSI. Don’t exceed the maximum pressure limits of the equipment. These are for this model.
Don’t adjust the pressure switch to make the feeder more reactive or provide a higher flow. This should be set to match your system requirements and won’t exceed any of the components' ratings.
Incorrect pressure settings can cause the unit to constantly cycle, not provide enough makeup or cause overpressure. Have a qualified HVAC technician check the settings when installing.
7. Glycol type
Glycol solutions are commonly used in commercial HVAC systems. Inhibited Ethylene Glycol or Propylene Glycol. The correct concentration will depend on the lowest temperature the system will reach and how much freeze protection you require. Increasing the concentration will affect the viscosity, heat transfer and pumping.
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Before selecting your glycol feeder, check:
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What type of glycol is used in the current loop.
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What concentration is required.
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What temperature freeze protection is required.
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Ensure the pump and tank are compatible.
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What concentration the pre-mixed solution is.
Your glycol feeder should have a compatible solution and correct concentration. Adding plain water can slowly dilute the solution and reduce the freeze protection. Use the correct refractometer and conversion information from the glycol manufacturer to check the concentration. Don’t go by the appearance.
Bypass Feeder have a guide on adding glycol to a closed loop system. This will help you determine the current concentration, correct fluid and how much you will need.
8. Space and accessibility
Even if you have the correct tank and pump size, the glycol feeder may not be suitable for your mechanical room. Ensure there is enough space for the tank, pump, pipework connections, electrical connections and future maintenance.
Ensure:
The unit is a suitable size. Check the unit will fit the available floor space. It should be able to be placed on a suitable flat base. The tank is compatible with the glycol type.
Check it is suitable for the glycol formulation and manufacturer-approved operation.
It is easy to check the fluid levels, top up the tank, check the connections and service the pump.
Low level protection. A float switch or low level alarm can help prevent the pump running if there isn’t enough fluid in the tank.
Single or multiple loop. If your facility has separate heating and cooling loops, you may need separate feeders. Some specialist double pump systems are designed for two separate closed loops.
Ensure there is suitable isolation and connections for servicing. Follow the installation manual for your chosen model. Pressure connections and electrical work should be completed by qualified staff.
FAQs
Do I always need a larger glycol feeder for a larger HVAC system?
Not necessarily. Whilst the volume of your loop is important you should size the tank to the expected makeup, how regularly you can top up and how much reserve you need. You should also ensure the pump is suitable.
What sizes of glycol feeder are available?
This will depend on the manufacturer and model. Bypass Feeder offer compact models such as 10 and 17 gallon feeders. We also offer larger models such as 55-gallon.
Can I use a glycol feeder to fill my new closed loop system?
Not necessarily. Some feeders are designed for makeup only and may not have enough flow capacity. Check the manufacturer's instructions and use suitable filling equipment.
How often should I top up my glycol feeder?
This will depend on how often you need to complete makeup, tank size and how regularly you can check. A correctly functioning closed loop should not require much makeup. If you are needing to top up unexpectedly, investigate for a leak.
Do I need to size the pump?
Yes. The tank will determine how much solution you can store, but the pump will need to ensure it can provide the correct flow rate. Both should be suitable for your application.
Selecting the correct glycol feeder
Sizing your glycol feeder correctly will involve more than just ensuring you have a tank large enough for your closed loop system. The amount of makeup you will require, pump performance, pressure, glycol concentration and maintenance will all affect your choice.
By selecting the correct glycol feeder, you will help maintain fluid levels and pressure. It will also reduce the need for manual topping up and provide a more consistent way of topping up with compatible glycol solution.
Bypass Feeder offer J.L. Wingert and Neptune glycol feed systems. We offer models for commercial HVAC, hydronic heating, chilled water and industrial process. View our glycol feeders or contact us to help find the right model for your application.