I have leaks in my chiller. Do I have to convert or change out my chiller?
Not necessarily, not if the leaks can be stopped with a sealant. In some cases a sealant can be applied to the areas leaking and then painted over to prevent the leak from causing operational problems for the chiller. This is not a permanent fix as the chiller gaskets and O-rings may be getting old and brittle having less flexibility. Applying an external sealant may give you an extra year or two to get ready, or budget to repair, replace or convert your chiller.
My chiller is thirty years old. Should I convert or change out the chiller?
This depends on whether you have the financial means to just replace the chiller and any relevant mechanical items to give you the most cost efficient operation in the future. The older chillers operate in the one-kilowatt per ton area, whereas, if you wish, you can engineer a chiller to operate in the half a kilowatt per ton area. These extremely efficient chillers cost more to purchase but if the cost of hydro keeps increasing then the purchase cost will be worth the investment. The difference between conversion and replacement in monetary terms can be quite high. If you do not require the full capacity of your present chiller, then conversion may be your most economical plan.
Parts of my building are too warm and I get complaints. Do I require a larger chiller?
First of all, find the original specs for the chiller. They should be in a binder left by the installing mechanical contractor. If not, your service contractor or the manufacturer of the chiller may provide you with the specifications, if you give them the model and serial number. You can then ask your service contractor, or your staff, to set up the chiller to specified chilled water and condenser water flows and set up the in-and-out thermometers on the chilled water and condenser water for accuracy. Then, on the days when the complaints start, look at the amperage draw of your chiller. If the amperage is at specification for full load, and your temperatures for the chilled water and condenser water are within specification, then you probably require more capacity. If the amperage is lower than specification, a chiller mechanic is required to see if the problem is with the chiller or with the chilled water system.
My chiller works well in the spring and fall but keeps shutting down in the summer. What is wrong?
If the chiller is shutting down on low refrigerant temperature, it is likely that your chiller is short of refrigerant. This means a leak check, fixing the leak and then topping up the charge. An alternate cause could be fouled evaporator tubes, which will need to be cleaned.
If the chiller is shutting down on high head, then it could be fouled condenser tubes. The condenser tubes should be cleaned annually. It could also be a problem with the cooling tower or if you have a low- pressure chiller, a leak allowing air into the chiller. These are the most common problems causing a shut down at heavier load conditions. If these are not the cause, then you require an experienced chiller mechanic to troubleshoot your system.
How can I save money with my current system?
In many cases money can be saved through the installation of a Variable Frequency Drive (VFD). With VFD’s installed on the cooling tower fan motor, the designed water temperature for the chiller can be achieved by slowly increasing the speed of the fan, rather than the starting and stopping of the fan where all the electrical power is used to maintain the designed water temperature for the chiller, not to mention the wear and tear on the components of the equipment. The condenser supply water temperature is kept closer to 80’F at all times lowering the use of electricity.
A similar Soft start system can be installed on the chiller’s motor replacing the conventional Wye-Delta starters.
The control system can be changed on some of the older chillers to raise the chilled water supply temperature as the chilled water return temperature falls (load on chiller diminishes) thereby using less electricity. This is a very economical (low cost) change.
If the Refrigerant charge is kept at optimum and the tubes are kept clean the cost of operation is kept as low as possible. A 10% saving could be achieved with only some of these options.