The Mis-Match Saga Continues

VINDICATION is Sweet!  I have been railing for months that changing an outdoor unit to a 13- seer while leaving a 10-seer air handler was a mean, awful, nasty, unethical thing to do. I didn’t have the “run test” data to back up such a claim, just the number crunching of the engineering data.  That was then.

Now, the good folks at a local power company have done the research that has been so desperately needed to show the actual effect of this MIS-Match situation, and I applaud them for it.

  • Up to 40% reduced capacity in cooling which means system may not be able to keep up with the thermostat.
  • Up to 48% reduced capacity in heating resulting in heat strip coming on earlier.
  • Up to 40% reduced efficiency in cooling resulting in higher power bills. Not only is it going to run longer, but also dollar per cooling will be more as well.
  • Up to 60% reduced efficiency in heating resulting in higher power bills.
  • System charging becomes critical since the charge might seem correct for one season but not another.
  • TXV will not solve the charge problem for all cases since the Super Heat and Sub Cooling can change dramatically with condition.

All of these situations will result in numerous service calls and most likely the only way to resolve it is to replace the indoor coil with a larger coil anyway. 

In Florida the Energy TAC has produced a “DEC” statement that requires install at or above the SEER from the last time the system was inspected when changing component parts.  The data shows that unless both indoor and outdoor pieces or changed, it is a violation of the Florida Energy Code.

The real problem is that our state only has so much electrical energy available.   Since several hundred thousand of these change outs per year are being installed there will be a significant impact on peak energy consumption.  The amount of power required to run all these new units will dramatically increase and possible surpass that which the power companies are capable of supplying.

Governor Charlie Crist has recently issued and Executive Order that makes bold statements requiring significant mandatory increases in energy efficiency in new construction houses, and the appliances in them. This is a positive move, though the change-out market of A/C dwarfs the size of the new construction market.  All the efforts in new construction would be squandered if these inefficient mis-matched installations continue to be allowed in the market 12 + million existing systems that will most likely need replacement over the next ten years and not just new construction.

The hidden problem is that these mis-matched systems will require refrigerant charge modification twice per year.  In the Power Company scenario, that was the removal of approximately four plus pounds of refrigerant to allow the unit to operate in heating, only to have it reinstalled in the cooling mode.  The test results also clearly show that the application of a TXV does not eliminate the problem. 

Written by Bob Cochell, a FRACCA Board member and member of the Energy Technical Advisory Committee of the Florida Building Commission


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