Most coil performance problems that surface during installation or commissioning did not start on the job site. They started in the spec. A parameter that was assumed rather than verified. A dimension that was carried forward from a previous project without checking whether it still applied. A glycol concentration that nobody flagged because it looked close enough. By the time the coil is on site and the problem is visible, the options have narrowed considerably.
This is the pattern we see repeatedly, and it is why the application review that happens before fabrication is the most consequential part of the process. Not the fabrication itself. The review before it.
The three field problems that almost always trace back to the spec
Problem 1
The coil does not meet leaving conditions under actual operating loads
The system runs but never quite reaches setpoint. Complaints come in gradually. The coil gets blamed, but the coil was built to the parameters submitted. The parameters were wrong. Entering air conditions were assumed from a general reference rather than the actual system design, or the latent load was underestimated and the coil was selected for the wrong wet bulb temperature.
Problem 2
The coil does not fit the casing or connect to the piping as intended
The coil arrives on site and the connections are on the wrong end, or the face dimensions account for the coil body but not the header or the drain pan. Nobody flagged the physical constraints because they were not in the spec. The contractor now has a coil that requires field modification, additional piping, or in the worst case a reorder and a schedule delay.
Problem 3
The coil underperforms at part load or in cold weather operation
The system heats adequately in mild conditions and loses capacity exactly when it is needed most. Fluid-side parameters were submitted without accounting for glycol concentration or actual entering fluid temperature at design conditions. The coil was built to the wrong load. The difference between a correct and an incorrect glycol concentration affects both heat transfer coefficient and pressure drop in ways that are not visible until the system is under stress.
“Most field problems with coil performance trace back to the spec, not the product. A coil built correctly to wrong parameters is still a problem. The review catches the parameters before fabrication begins.”
What the pre-fabrication review actually involves
When a spec comes to HX Coils, the application review checks the submitted parameters against the application before the coil goes into production. That means verifying that entering air conditions include both dry bulb and wet bulb temperatures, that fluid type and glycol concentration are specified and consistent with the application, that entering fluid temperature and flow rate are provided, that face dimensions account for headers and connections in addition to the coil body, and that connection location and orientation match the installation.
When something does not add up, we ask. Not to delay the order. To prevent the kind of problem that brings everyone back to the job site after the coil is installed and the system will not perform.
HX Coils has been manufacturing custom heating coils, cooling coils, and replacement coils for commercial and industrial applications across the Mid-Atlantic region for over 30 years. We can replicate any coil from any manufacturer and turn around emergency replacement orders in as little as two days. But the review before fabrication is the capability that prevents the emergency in the first place.
If you have a coil spec in development or a replacement application where you are not sure the original parameters still apply, send it to us before the order is placed.
Send us your spec before the order is placed.
HX Coils manufactures custom heating coils, cooling coils, and replacement coils for commercial and industrial HVAC applications across Eastern PA, Southern NJ, and Delaware. The application review is free and takes less time than a field problem.
Call Us Today!
References
1. ASHRAE. ASHRAE HVAC Systems and Equipment Handbook. Covers coil selection parameters, entering air condition requirements, latent load calculation, and fluid-side performance considerations for custom HVAC coils. ashrae.org
2. AHRI. Standard 410: Forced-Circulation Air-Cooling and Air-Heating Coils. Industry standard for rating and testing forced-circulation coils including performance verification at specified operating conditions. ahrinet.org
3. SMACNA. HVAC Systems: Design Handbook. Covers coil application in commercial air handling systems, physical installation requirements, and connection orientation considerations. smacna.org
