Installation Tips: Evaporators

April 1, 2008
There are many different thoughts on installation procedures of evaporators. Coming from a contractor background, I will briefly share some of my successes. Note: always inspect your evaporator for damage, and check to make sure it’s the correct unit for this job before you proceed.

By Robert Thornton

There are many different thoughts on installation procedures of evaporators. Coming from a contractor background, I will briefly share some of my successes. Note: always inspect your evaporator for damage, and check to make sure it’s the correct unit for this job before you proceed.

1. Prepare the Unit. Assuming that all load calculations, equipment matches, and component selections have been accurately determined, I like to mount all of my components — thermal expansion valve, nozzle, solenoid, thermostat, etc. — on the evaporator while it is on the ground. I also cap the inlet and outlet, and perform a leak check before hoisting the evaporator into the air, to simplify the repair.

Always use proper brazing techniques. Heat sink any component that may be damaged due to heat. Follow wiring diagrams that are supplied, making sure not to over strip the wire ends, then tighten adequately.

2. Use a Template as a Guide. A template of the hanging brackets can be made from a piece of cardboard that the evaporator is shipped in. Place that template up to the ceiling, and mark where the evaporator will be attached, then drill holes completely through the top panel. The mounting location should not be over doors. A good rule of thumb is to hang the evaporator at approximately the height of the coil, away from the back wall. There are many circumstances affecting this distance, but the main goal is to get sufficient air back to the entering airside of the coil.

3. Consider Hanging Options. Depending on the size of evaporator, there may be a couple of hanging options. Small evaporators can use threaded rod or long threaded bolts inserted through the panel using large washers to keep the bolts in place. Larger units will need reinforcement, such as uni-strut or steel plate, placed on top of the panel before inserting the threaded rod.

4. Attach Coil. Now, the coil can be lifted onto the bolts or threaded rod, and the nuts and washers tightened so that the coil is safely suspended. Before tightening down, it’s a good idea to fill the drilled holes, and all other penetrations that have been made, with spray urethane foam such as Great Stuff, to prevent air and moisture migration when the system is in operation.

Use padding on the lifting device, so as not to damage the coil. Always lift from the sturdiest points of the coil — sides and ends, or if possible, the mounting brackets.

If your evaporator has a channel that runs from top to bottom directly under the mounting bracket, run the threaded rod all the way to the bottom of the channel, for added holding strength. As the coil is tightened, remember to pitch it, for good drainage later. Some larger coils have mounting brackets that are meant to pitch the coil for proper drainage to one end. Pay attention to those brackets, as the coil is not meant to be perfectly level.

5. Connect all Piping. Next, connect all refrigerant piping so that you can perform an evacuation while the remainder of the installation is completed. If a distributor nozzle is required, insert the correct one into the distributor followed by the expansion valve, before completing piping. If multiple evaporators are being used, the liquid line solenoid valve needs to be installed before the tee. On a single evaporator, install the solenoid valve before the expansion valve. A suction line “P” trap will always need to be installed if at any time the suction line becomes a riser that goes up above the evaporator.

6. Clamp TXV Bulb to Line. The thermal expansion valve bulb can now be clamped to the suction line. Mount it in the three- or nine o’clock position. Depending on the pipe diameter of the suction line, this position may vary slightly, so as to not sense the liquid that may be in the bottom of this suction line. Make sure the bulb makes solid contact to the full surface of the bulb and is tightened securely. Insulate the bulb completely.

7. Allow for Proper Slope. When installing the condensate drain line, always use steel or copper in freezers and slope away from the evaporator at a minimum pitch of …-in. per foot. Electric defrost units that operate below 34F should have electric heat tape and insulation affixed to the condensate line. Twenty watts per foot is adequate. This tape can be wired to a constant power source, such as a standard plug- n or, based on the wiring arrangement, there are several power sources available inside the evaporator wiring. The condensate drain line will also need a “P” trap installed before it drains or tees together with another condensate drain from another unit.

8. Follow Wiring Diagrams. Wiring diagrams are supplied with new evaporators and should be followed. There are far too many wiring configurations to cover here as they include air, electric, and hot gas defrosts, single and multiple evaporators, defrost contactors and single timers. Local codes must always be adhered to.

9. Check and Adjust. Now that all of the installation is complete and evacuation has been done, it’s time to power up the unit, after adding an initial refrigerant charge into the condensing unit. Check that fans are tight, blowing in the right direction, and are operating. You’re now ready to make adjustments (superheat, defrost, temperature, etc.) and verify all components are working properly.

There’s no way to cover every procedure in this small article, but these are the most important. In addition, the Heatcraft Refrigeration Products installation and operations manual is an excellent resource that offers many helpful suggestions. Find it at For other support, call 800/537-7775.

Robert L. Thornton is a sales engineering specialist with Heatcraft Refrigeration Products. Edited by Charles Tice, sales engineering specialist.