Heat pump installation and service across Suffolk County.

In cooling mode a heat pump works exactly like an air conditioner — it absorbs heat from inside the house and rejects it outside. The difference is a reversing valve. In heating mode the flow reverses, and the outdoor coil absorbs heat from the outside air and pumps it indoors. There is no flame and no electric resistance element doing the work; the compressor is moving heat that already exists in the outdoor air, even when that air feels cold.

Because it moves heat rather than generating it, a heat pump can deliver more units of heat into the house than the units of electricity it consumes. That ratio drops as the outdoor temperature falls, which is why sizing and backup heat matter — but the principle holds down to temperatures well below freezing.

As the outdoor temperature drops, a heat pump produces less heat and runs longer to meet the same load. At some point the heat pump alone cannot keep up, and supplemental heat comes on to help. On a correctly sized system that point is reached only on the coldest days of the year; on an undersized system it is reached constantly and the backup heat runs all the time.

The supply air from a heat pump in heating mode is cooler than the supply air from a furnace — roughly 95 to 105 degrees instead of 120 or more. It feels lukewarm to a hand held over a register, and homeowners who are used to furnace heat sometimes read that as a problem. It is not. The air is warm enough to heat the room; it is just not hot. If the house is not reaching the set temperature at all, that is a different issue and worth a call.

Frost builds on the outdoor coil during heating because the coil is colder than the outside air. The system periodically reverses to melt that frost off, and the outdoor unit gives off steam while it defrosts. That is normal operation. A unit that builds a thick coat of ice and never clears it has a defrost problem, and that is a repair.

An air conditioner is sized for the cooling load on the hottest day. A heat pump has to be sized for the heating load on the coldest day too, and on Long Island the heating load is usually the larger number. A heat pump sized only for cooling will short-cycle all summer and run on backup heat all winter, which defeats the purpose of having one.

Sizing comes from a load calculation — square footage, insulation, window area and orientation, air sealing, ceiling height, and duct location — not from a rule of thumb about tons per square foot or from copying the old unit's label. The load calculation tells us what the house actually needs at design temperature, and the equipment is matched to that. We do not print a tonnage or a capacity figure on this page, because the number belongs to a specific house.

A ducted heat pump uses an outdoor unit and an indoor air handler connected to a duct system, and it replaces a furnace and an air conditioner with one piece of equipment. It is the right answer when the house already has sound ductwork that can carry the airflow the heat pump needs.

A ductless heat pump — a mini-split — uses an outdoor unit and one or more indoor heads mounted directly in the rooms, with no ducts at all. It is the right answer for a house on baseboard or radiators with no duct system, or for a single room that the existing system does not reach. The ductless mini-split installation and service page covers where those make sense room by room.

If the existing ductwork is undersized, leaking, or run through unconditioned space, that has to be dealt with as part of the job. A heat pump on bad ductwork underperforms for the same reason a new air conditioner on bad ductwork does — the equipment is fine and the air never arrives.

A heat pump makes sense when a homeowner wants one system that heats and cools, when the existing furnace or air conditioner is at the end of its life, or when a house on baseboard heat wants air conditioning and is open to letting the heat pump carry the heating too. It also makes sense as a dual-fuel setup alongside an existing boiler, where the heat pump handles the heating most of the winter and the boiler takes over on the coldest days.

A heat pump does not make sense on ductwork that cannot carry the airflow, in a house where the heating load is far larger than the cooling load and the backup heat would run constantly, or when the only reason to switch is the refrigerant rules — a working R-410A system does not have to be replaced. If the path is repair rather than replacement, that conversation starts on the AC repair page for cooling or the heating repair page for heating.

We will tell a homeowner which situation they are in before anyone spends money. If the house is better served by a new AC installation and replacement and a separate furnace, we say so.

We service and repair heat pumps regardless of who installed them. Common heat pump calls: a system that cools but will not heat, or heats but will not cool, which is often a reversing valve or a control problem; a system that runs auxiliary heat constantly and runs up the electric bill, which is usually a sizing or a defrost problem; an outdoor unit that ices over and never clears; a system short on refrigerant, which means a leak in the line set or at a flare and not a system that "needs a top-up."

Diagnosis on a heat pump means reading supply and return temperature difference across the coil in both modes, suction and liquid pressures against outdoor temperature, superheat and subcooling, amp draw on the compressor and the fan, and what the control board is reporting. Travis Hart is EPA Section 608 Universal certified, certification number 303313, and he is the person reading those numbers, not a dispatcher.

Regular seasonal tune-ups and inspections catch a drifting charge or a failing defrost control before it becomes a no-heat call in January.