When you put Al Knight and Nathan Walker together, you could say that you’ve got both sides of a split system heat pump. Knight is the outdoor split system product manager for Goodman Manufacturing. Walker is the indoor split system product manager.

They are each important in their own ways, but like the indoor and outdoor coils of a heat pump, if you get them working together, you have a very efficient technical experience. And that is their main point about installing replacement heat pumps: You need to match the indoor coil to the outdoor coil, especially when the newer unit is replacing a less-efficient model.

That happens a lot these days. “It’s very important to put in a properly matched system,” Knight stressed. “Make it an ARI match. We don’t promote the use of third-party coils, but if the coil match is sanctioned by ARI, it should be OK.”

Said Walker: “Sometimes you get into situations where contractors try to reason their way out of using a properly matched system. They need the ARI match.

“We encourage people to go to the ARI Website. Given that the match you want is good, the site will produce a pdf certificate. But we do publish these matches in our spec sheets as well.” He noted that Goodman’s new indoor coils can be used with either R-410A or R-22.


The line set is “the critical link between the indoor and outdoor components,” Walker said. It needs to be clean and dry, with no oil from the old system.

The duo stressed the importance of proper system evacuation and dehydration before the new refrigerant is charged in, especially if it’s R-410A, which tends to be more sensitive to moisture and noncondensables.

“You don’t have to change the (correctly sized) line set provided proper evacuation and dehydration techniques have been taken,” Walker said. “Also, make sure there are no mineral oil pockets.”

Oil and moisture can wind up in any dip or depression in a horizontal run of copper tubing, he said. “It finds the lowest point.” Products are available to flush line sets out. They recommended Nu-Calgon’s Rx11-flush™.

“The old filter-drier needs to be removed. All of our units have a filter-drier installed,” he added. “It’s already in the unit, installed in the line.”

How does a contractor get the correct length of the line set? “Just follow our installation instructions,” said Knight. “For starters, we don’t have anything less than a 3/8 inch for the liquid line.” If the unit coming out was not this manufacturer’s, the installer may well need to make changes to the length.

How much of a difference is that? “It could be quite a bit,” Knight said. “There are still some older heat pumps out there that were somewhat unique in their use of one-quarter-inch liquid lines. There are still a lot of them out there.”


Both Knight and Walker recommended performing a whole-house load calculation to make sure the unit going in is the correct size for the home.

“Don’t swap out like with like,” Knight said. “Maybe the owners have added some insulation, maybe they’ve replaced their windows” - or maybe the old system was installed without a load calculation being done at all.

The two recommended using whole-house load calculation programs from Nitek Software, Wrightsoft, or Elite Software. Nitek’s Load Wizard™ software has Goodman model numbers and capacities already loaded into it, they pointed out.

Finally, don’t overlook the “heat” aspect of the heat pump efficiency, especially further north.

“I would encourage the contractor to pay more attention to HSPF (Heating Seasonal Performance Factor),” Walker said. “When you look at the actual cost calculations, HSPF will come into play for what the homeowner will spend throughout the year. We have very high HSPF product lines in our high-end products.”

Publication date:05/28/2007