THE PROOF IS IN THE TESTING – RUSHCO TEST STAND
Ensuring Chiller Performance As Specified Under Job Site Conditions
PROJECT DATE: 2022
We test RES Rental equipment when returned, before it goes out, and when we purchase new chillers.
In a rental fleet, equipment is always leaving and returning to the “yard”. Some of it has been on a rental application for months, working hard and hopefully remaining invisible to the customer. While it is serviced by RES in the field, the environment of rentals is often brutal and less than ideal for machinery. Rental chillers and boilers often operate at full demand in outside areas exposed to the environment- blistering heat, sand, and dust coating coils and electronics, with wind and rain trying to short things out. Twenty-four hours per day and seven days a week at high demand in these conditions are hard on equipment.
So RES recently decided we needed to build a test stand in our yard to test equipment when it is being returned, before it goes out, and when we purchase new gear.
We want to be sure when the rental gear leaves our yard headed to its destination, it will start quickly and meet demand with no issues.
We had the pumps, the hoses, and the tanks but we needed to put it all together with a heat load. You might think, “well, just connect a tank and let the water cycle through the chiller”. But this does not consider the incredible cooling power of a modern chiller. It simply drops temperature too quickly on a loop of water if there is no heat load on it.
Let’s do some math to prove this:
BTU= amount of energy required to heat 1 LB of water 1 degree
Let’s say we have a 1,000-gallon tank connected to a 300-ton chiller and our starting water temp is 80 degrees (70 degrees out of the tap plus some Texas sun heating it up in a tank). To drop 8,340 lbs of water by one degree, we need to remove 8,340 btus. To drop 8,340 lbs of water 35 degrees (80- 45 degree setpoint = 35 degrees worth of heat to remove) we need to remove 291,900 btus(8,340 LBS X 35 degrees x 1 btu per lb per degree ). A 300-ton chiller will remove 3,600,000 btus per hour (300 X 12,000). Let’s divide what we need to remove by what we CAN remove: 291,900/3,600,000 = 8%. This 1,000-gallon tank at 80 degrees is 8% of what our 300-ton chiller can do in an hour. I am going to extrapolate here a bit, this is not hard science, but an approximation- 8% of an hour is 5 minutes. We can reach a setpoint on 1,000 gallons of water that has no additional energy/load put into it with a 300-ton chiller in less than ten minutes. This is not long enough to test the chiller. We need a “false” load.
So, we ran a new gas line to a rental boiler in the yard and added a coil in an open tank to heat the water to create a false load for our chillers. This coupled with our existing gear completed our test stand for air cooled chillers. We can now test run our gear before it goes out.
This allows us to run our rental chillers at full capacity on our test stand. We can check compressors, refrigerant charge, suction and discharge pressures, and condenser fans and make sure we are making nominal tonnage. We can swap out pumps for varying size chillers.
This simple test stand will allow us to ensure the equipment we are delivering is running correctly when it leaves RES and that it will start and run correctly when it reaches your site. A simple thing to do that has enormous benefits when time becomes critical on the rental job site.