What's normal in cold weather, and what isn't
Some winter behavior looks like a breakdown but isn't. Below about 32°F, frost builds on the outdoor coil and the heat pump runs a defrost cycle: it briefly switches into cooling mode, the outdoor fan may stop, and backup heat may come on. The U.S. Department of Energy's homeowner guide says a defrost usually lasts 5 to 15 minutes (DOE-hosted heat pump guide). A unit that stays iced over or seems stuck in defrost is a reason to call a technician.
The same guide lists the signs that point to a real problem: the system won't run or keeps cycling, the house never reaches the setpoint, humidity stays high, it's unusually loud, the auxiliary heat light is on all the time, there are strange smells, or the coils are frozen or dirty. Before the visit, write down which of these you saw, when, and the outdoor temperature. Check the filter too, since a clogged one restricts airflow (how often to change a furnace filter). Don't open panels, touch wiring, or chip ice off the coil.
In a Philadelphia rowhome, defrost meltwater drips from the outdoor unit. DOE notes it shouldn't pool and refreeze where people walk, which matters when the unit sits beside a narrow back walkway or over a shared alley.
What the technician should actually test
Airflow and refrigerant charge are the two faults the Building America Solution Center flags as significantly raising energy use, along with duct leakage (heat pump commissioning guide). Ask for the numbers behind each one:
- Airflow: total external static pressure or a measured airflow reading, plus the filter and indoor coil condition.Refrigerant charge: readings checked against the manufacturer's method, and where any leak was found. Adding refrigerant without finding the leak is a short-term fix.Defrost and backup heat: whether defrost starts and ends properly, and when the auxiliary heat is set to take over.Condensate drain and outdoor coil: clear and clean, with the unit raised above snow and ice.Ductless units: the indoor head's filter, coil and drain, since each head can fail on its own.
The EPA says homeowners should use technicians certified under Section 608 for refrigerant work (EPA guidance on repairing heat pumps). If your system uses R-22, a repair usually means recharging with R-22, which is increasingly scarce. The EPA also warns that the flammable product sold as “R-22a” is unsafe. Ask which refrigerant your unit uses and what a recharge involves before you approve one.
Repair or replace: the questions that settle it
DOE puts a typical heat pump's life at about 15 years. Building America's pre-retrofit guidance says equipment older than 15 years can be assumed to be near the end of its life, and that only minor, low-cost repairs are usually worth it after that (pre-retrofit assessment). Ask the technician:
- How old is the outdoor unit, and the indoor coil or air handler?Is this a single failed part, or the second or third repair in a few winters?Does the system use R-22?Would a new system be sized from a room-by-room load calculation?
If replacement comes up, Building America's checklist calls for an ACCA Manual J load calculation, equipment chosen with Manual S, the charge verified to the manufacturer's specs, and room-to-room airflow testing (heat pump replacement checklist). A quote that simply matches the old unit's size skips that step. Our guide on what a heat pump quote should explain about sizing goes through what to look for.
If you keep an old furnace or boiler as backup, DOE suggests setting its thermostat 2 to 4 degrees below the heat pump's setpoint, so the backup only runs when the heat pump can't keep up.
Philadelphia permit rules for repair versus replacement
The City's Department of Licenses and Inspections says you need a Mechanical Permit to install heating, venting and air conditioning equipment, but not for ordinary repairs or maintenance (Philadelphia Mechanical Permit page). So a capacitor or a cleaned drain is usually just a repair, while a new heat pump is permitted work. Replacing an appliance in a one- or two-family home can qualify for an EZ permit, which doesn't need plans. A licensed contractor must do the work and be current on City taxes with insurance on file, residential applications include an HVAC Equipment Design Form, and inspections are scheduled once work is ready to start. Homes on the historic register need Historical Commission approval before L&I will accept the application. For a related job, see what permit a furnace or central air replacement needs in Philadelphia.