Replacing a 15 Year Old Heat Pump in Prince George's County
Key takeaway: A fifteen year old heat pump has run in both seasons every year of its life, and the failures that end the repair argument on this equipment are a dead compressor, a leaking reversing valve body, a leaking outdoor coil, and a defrost board that has been replaced twice. Strip heat arriving earlier in the fall and running longer than it did three winters ago is a measurement of lost capacity rather than a thermostat setting. What changed since the mid 2000s is real. One fixed compressor speed became a modulating range, the federal test changed so SEER2 and HSPF2 cannot be subtracted from your old nameplate numbers, and the refrigerant moved off R-22 and R-410A to lower global warming potential options. What carries over from the old install is the ducts, the 240 volt circuit, the pad, and often the line set. What gets redone is the matched indoor coil, the electric heat kit sized to a real balance point, the breaker checked against the new nameplate, and the thermostat with its auxiliary lockout actually set. TerraStream Energy does this replacement work for single family homes in Maryland, with Prince George's County first, and the survey and load calculation come before any model number does.
Reading an Aging Heat Pump
What Fifteen Years Does to a Heat Pump
A fifteen year old heat pump has worked both seasons of every year it sat on that pad, so it carries compressor hours an air conditioner of the same age never had to.
An air conditioner in a Maryland house sits idle from October to May. A heat pump runs through the summer, turns around, and runs through the winter, and the winter hours are the hard ones because that is where the machine has the least margin. The Department of Energy calls a heat pump an energy efficient alternative to furnaces and air conditioners, and yours has been doing both of those jobs since it was new.
Wear arrives in order. Compressor valves and bearings give up a little output, which nobody notices inside one season. Contactor points pit and the run capacitor drifts, so starting gets harder. Outdoor fan bearings dry out, the fan moves less air, and the compressor pays for it. Fins turn chalky and pack with cottonwood. The defrost sensor drifts a few degrees and the board starts making decisions on bad information. Added together, that is a machine which holds the house in October and falls behind in January.
Before calling anyone, get the data plates. The outdoor plate faces the house where nobody looks, its serial carries a date code, and its model number carries nominal capacity in the digits, where 024 means two tons and 036 means three at 12,000 BTU per hour per ton. Write down the refrigerant, which reads R-22 or R-410A on equipment this old, the rated heating capacity at 47 degrees, and the MCA and MOCP, meaning minimum circuit ampacity and maximum overcurrent protection, which tell you what the existing wire and breaker were sized against. Do the same inside for the air handler, the coil and the kW on the electric heat kit. Then note behavior. How long it runs on a 20 degree morning, whether the thermostat shows auxiliary heat at 40 degrees outside, and whether the coil clears after a defrost.
Repair, Replace, and Who Makes That Call
A heat pump that still runs and needs a cause found needs a service contractor, which is a different phone call from a replacement.
TerraStream Energy replaces whole heating and cooling systems rather than repairing them, so diagnostics, service calls and seasonal maintenance are not what the company does. A homeowner who does not yet know why the system is limping should have it diagnosed by whoever services it, then decide. Nobody should buy a system to answer a question gauges can answer.
Plenty of failures are worth fixing on old equipment. A capacitor, a contactor, a condenser fan motor, a chewed low voltage wire, a plugged drain, a thermostat. Those are hours rather than projects and they buy real time. The failures in the next part are sealed system or control system work on a machine that has already spent its service life, and the repair leaves you holding one new part inside a fifteen year old system.
The Failures That End the Argument
A Compressor That Has Failed
A dead compressor on a fifteen year old heat pump ends the repair conversation, and the labor is more of the reason than the part is.
The compressor is the most expensive single component in the system and the heaviest labor to change. Recover the refrigerant, cut the lines, lift out the old one, braze in the new one with a new filter drier, pressure test, evacuate, recharge by weight. Every one of those steps is work a new outdoor unit needs anyway, and at the end the reversing valve, the coil, the fan motor and the board are still fifteen years old.
The breaker trips when the thermostat calls. The unit hums for a few seconds and goes quiet while the outdoor fan keeps turning. Suction and discharge lines leave the cabinet at the same temperature, which means nothing is being compressed.
An electrical failure makes it worse. When windings short and burn, acid and carbon leave the compressor and travel wherever the oil goes, which is the line set and the indoor coil. Cleanup means suction line driers, a flush, and sometimes new coil and lines regardless. If the plate reads R-22 there is a second problem stacked on the first, since production and import of that refrigerant ended under EPA's phaseout of class II ozone depleting substances and only reclaimed supply remains.
The Reversing Valve and a Board Replaced Twice
The reversing valve and the defrost control are the two parts nothing but a heat pump has, and when either keeps failing you are looking at a tired control system rather than one bad component.
The reversing valve is a four port valve that swaps which coil absorbs heat and which rejects it. That swap is the whole trick of a heat pump, and it is how the machine defrosts, by briefly running in cooling to send hot refrigerant to a frozen outdoor coil. Three things go wrong. The solenoid coil burns out, which is a small part and a quick fix. The slide inside sticks part way or bypasses internally, which gives lukewarm air in both modes and pressures sitting too close together. Or the valve body leaks at a brazed joint.
That last one ends the argument. The valve carries internal seals a few inches from where a torch has to work, inside a cabinet built for assembly rather than service. Shops do it. Few are eager to on a unit with this many hours.
The defrost board gets replaced twice more often than anything else on these units. Early boards ran defrost on a timer plus a coil sensor, and later ones measure the spread between coil and outdoor air and defrost on demand. Either way the board is rarely the root cause. It is the part that burns when a relay sticks, when the solenoid draws high current, when the sensor has drifted, or when defrost has run every twenty minutes for two winters and nobody asked why. A second board is a message. Boards for mid 2000s models also go obsolete, which turns a repair into a parts hunt.
A Leaking Outdoor Coil
A leak in the outdoor coil quietly decides the whole question, and the refrigerant is the reason rather than the coil.
Outdoor coils fail from the outside in. Fin to tube corrosion where road salt spray reaches them, fatigue cracks at a return bend, a trimmer line, a hailstone, a dog. Symptoms arrive slowly, longer run times first. Then frost on only part of the coil, because the refrigerant boils off early in the circuit. Then auxiliary heat carrying hours it never used to. Oily residue on the fins confirms it.
Topping off a leaking system is not a repair and it is not a plan. Venting is prohibited and recovery has to be done by a technician certified under EPA's Section 608 program, which governs how refrigerant is handled in the field. The supply picture has also moved. R-22 is reclaimed only, and R-410A is being reduced in new equipment under EPA's Technology Transitions program, which sets limits on hydrofluorocarbon use sector by sector, home air conditioning included.
Spot repairs got harder too. An all aluminum coil cannot be brazed the way a copper tube coil could, and when the replacement coil for a discontinued model is no longer stocked, the decision gets made for you.
Strip Heat Running More Than It Used To
Strip heat that comes on earlier in the fall and runs longer than it did three winters ago is a measurement of lost capacity, not a thermostat preference.
Strip heat is a bank of electric resistance coils in the air handler. One unit of electricity in, one unit of heat out. In numbers that is a COP of 1, where COP means coefficient of performance, the heat delivered divided by the electricity consumed. A heat pump in working order beats it by a wide margin in a Maryland winter. The ENERGY STAR cold climate designation requires a measured COP of at least 1.75 at 5 degrees Fahrenheit, with at least 70 percent of the 47 degree heating capacity still available there, under the ENERGY STAR criteria for air source heat pumps. When resistance heat starts carrying hours the compressor used to carry, the compressor side has lost ground.
The usual causes are a slow refrigerant loss, worn compressor valves, a coil too dirty to move heat, defrost firing more often than conditions call for, and an outdoor fan pushing less air. One more belongs on the list. The auxiliary lockout may never have been set at all. That setting ties strip heat to a balance point, which is the outdoor temperature where the heat pump's output equals the house's heat loss. A thermostat with no lockout hands the job to the coils the moment the room drifts behind, at 45 degrees outside as readily as at 15.
Two ways to see it yourself. Watch for the auxiliary or emergency indicator on a mild day, since no healthy system has business running resistance heat at 40 degrees outside. Then compare January electric use across a few years at the same setpoint. Separate out the habit question. Pushing the setpoint up eight degrees at six in the morning calls strip heat on any heat pump ever built, and that is a setting. Strip heat running while the thermostat holds steady on a mild day is the equipment.
What Fifteen Years of Standards Changed
Single Stage Then, Inverter Driven Now
A mid 2000s heat pump had one compressor speed and a current one has a range, and that single difference drives nearly everything you will notice after a replacement.
Single stage means off or all the way on. On a 55 degree day it makes full output, overshoots, shuts down, and starts again. An inverter driven compressor rides a variable frequency drive and holds whatever speed the house needs, which is a low speed most of the year. Long quiet runs instead of short loud ones. Better moisture removal in July, since humidity comes off the coil during run time and a short cycle gives it none.
The cold weather question got settled by the same change and has its own page on this site. Variable capacity equipment holds useful output at Maryland winter temperatures where single stage machines of that era had already handed the house to the coils. Winter design temperatures for this part of Maryland sit in the teens, and ASHRAE's climatic design data is where a contractor pulls them from. Ask for the manufacturer's extended capacity table at that temperature rather than the 47 degree rating off the brochure.
System element | Mid 2000s single stage heat pump | Current inverter driven heat pump |
|---|---|---|
Compressor output | One fixed speed, off or full | Continuously variable between a minimum and a maximum |
Published efficiency metric | SEER and HSPF under the older federal test | SEER2 and HSPF2 under the Appendix M1 test, not directly comparable to the old numbers |
Refrigerant | R-22 early in that period, R-410A later | Lower global warming potential refrigerant such as R-32 |
Indoor blower | PSC motor moving whatever the duct system allows | ECM variable speed motor holding a target airflow |
Defrost control | Run time interval plus a coil sensor check | Measured spread between coil and outdoor air temperature |
Backup heat control | Energized whenever the room fell behind setpoint | Staged, with an outdoor lockout temperature and a delay |
Thermostat | Any 24 volt thermostat with heat pump terminals | The system's own control on a manufacturer bus in many product lines |
Low temperature data | A 47 degree rating and little published below it | Extended capacity tables well below freezing |
What changed between a mid 2000s single stage heat pump and a current inverter driven system
SEER2 and HSPF2 Measure Differently
The rating on your old nameplate and the rating on a new quote came off two different tests, and one cannot be subtracted from the other.
Three terms, defined once. SEER2 is seasonal cooling efficiency, the cooling delivered across a season divided by the electricity it took, and HSPF2 is the heating version of the same idea. AFUE belongs to gas equipment and means annual fuel utilization efficiency, the share of fuel burned that ends up as heat in the house. One counts gas. The other counts electricity. They do not compare.
The federal test procedure changed effective January 1, 2023. DOE created SEER2, HSPF2 and EER2, says the revised procedure is "designed to produce measures of energy efficiency that better reflect real-world installation and use," and states that ratings under the new metrics "are not directly comparable" to the old ones. Minimums rose at the same time. A split system heat pump manufactured on or after that date has to meet 14.3 SEER2 and 7.5 HSPF2 under DOE's guidance on the 2023 standards. Maryland sits in DOE's hot humid southeast region in that same document, where the regional rules apply to air conditioners while heat pumps meet the national standard.
ENERGY STAR sits above that floor, qualifying split system heat pumps at 7.8 HSPF2, 15.2 SEER2 and 11.0 EER2, with the ducted cold climate designation asking for 8.1 HSPF2 on top of the low ambient performance described earlier. The practical use of this is narrow and real. Do not let anyone compute your savings by subtracting your old HSPF from a new HSPF2. Ask for the AHRI certified reference number of the combination being proposed, and the heating capacity it makes at the winter design temperature.
The Refrigerant Changed Under You
A heat pump bought in the mid 2000s holds R-22 or R-410A, and neither one is what a new system will be charged with.
R-22 went first, for ozone reasons rather than climate reasons, and systems still running on it live on reclaimed supply. R-410A came next with no ozone problem and a high global warming potential, which is what EPA's Technology Transitions program addresses. New residential equipment moved to lower global warming potential refrigerants, which in the ducted market mostly means R-32 or R-454B.
Both carry an A2L safety classification, meaning mildly flammable. Handling, the leak detection built into some equipment, and the service parts are specific to the refrigerant, and the old charge cannot go into a new system. R-32 has one property worth knowing. It is a single component refrigerant rather than a blend, so a leak does not change the mixture of what stays behind.
TerraStream Energy installs Daikin and Goodman equipment on R-32, which is the practical reason the line set and coil questions in the next part get answered against the manufacturer's installation instructions rather than against a rule of thumb. Pressures in this class of refrigerant sit near where R-410A sat, so reusing copper becomes a question about condition, diameter and cleanliness rather than about whether the tubing can hold pressure.
What Carries Over and What Gets Redone
The Line Set and Whether It Can Be Reused
The two insulated copper lines between the outdoor unit and the indoor coil are often the one part of a fifteen year old install worth keeping, and whether they stay comes down to diameter, condition and what used to be inside them.
There are two. A small liquid line and a larger suction line carrying vapor back to the compressor. Reuse starts with diameter, since every manufacturer publishes line sizes against actual length and vertical rise, and a suction line one size off changes pressure drop and oil return in ways that surface as a capacity complaint two years later rather than a failure on day one. Then condition. No kinks, no flattened sections, insulation intact, no buried joints nobody can inspect, length and lift inside the limits in the instructions.
Then the history. R-410A and R-32 systems use POE oil, polyol ester, which pulls moisture out of open air and does not tolerate the mineral oil R-22 systems ran on. A line set that spent fifteen years carrying mineral oil either gets flushed by the manufacturer's procedure or replaced, and after a burnout it gets replaced without debate. A clean R-410A era line set of the right diameters is a different story, and the instructions for the new equipment decide whether it stays.
The work around the lines is where corners get cut. The old charge gets recovered rather than vented. Brazing happens under a dry nitrogen purge so the tubing does not grow oxide scale that ends up in the new metering device. Joints get pressure tested with nitrogen, and the system gets evacuated to a deep vacuum proven with a micron gauge and a standing decay test, not by watching a clock. A quote that never mentions a pressure test or a vacuum is not describing the job it is bidding.
The Air Handler, the Coil and the Electrical
The outdoor unit cannot be replaced by itself, because the rating and the capacity belong to the pair rather than to either box.
Performance for this equipment is published for tested matched combinations, and the AHRI directory of certified products is where one gets confirmed. A new outdoor unit on a fifteen year old coil has no published rating and will not deliver either unit's number. The metering device is the deeper problem. An old coil's fixed orifice or expansion valve was matched to a compressor that ran at one speed, while modulating equipment needs a coil built for a range. Many product lines require their own matched coil, and the communicating ones their own air handler.
The blower is the other half. A PSC motor moves whatever the ducts allow and never tells you there is a problem. An ECM variable speed motor targets an airflow and works harder to hold it, so duct restriction turns into noise and short equipment life instead of quietly low airflow. Static pressure gets measured with a manometer before equipment is selected. Airflow problems that live in the ducts are duct work, which TerraStream Energy does not take on, so a house with crushed trunk lines or an undersized return needs the homeowner's own contractor for that portion.
Several things do carry over. The platform or closet, the return, the filter cabinet, the condensate drain and its trap, the low voltage run back to the thermostat. The electric heat kit is not one of them, since a new kit gets sized against the balance point of the new equipment rather than copied off the old plate. On the electrical side the surprise runs opposite to what people expect. Inverter equipment frequently draws less than the single stage unit it replaces, so an existing breaker can be too large for the new system and has to come down to match the nameplate MCA and MOCP. The disconnect, the whip, the ground and the conduit get checked at the same time.
The Thermostat and the Backup Heat Lockout
The thermostat is the part most likely to be carried over out of habit and the part most likely to waste the equipment you just bought.
A 24 volt thermostat with Y, W, O and B terminals cannot run a communicating inverter system, which talks to its air handler over the manufacturer's own bus. There the control is part of the system rather than an accessory. On conventional 24 volt equipment a familiar thermostat can stay, and then the settings have to be entered rather than left at factory defaults. Heat pump mode rather than conventional. Staging and differentials. Recovery behavior for setbacks, where a lot of surprise strip heat comes from.
The setting that matters most is the auxiliary lockout, tied to the calculated balance point. Above that outdoor temperature the compressor carries the house alone. Below it the coils stage in. Pulling that number from a load calculation and the manufacturer's capacity table, entering it at startup, and writing it down for the homeowner is the difference between a system that behaves and a January bill nobody expected.
Two more terms. Dual fuel means keeping a gas furnace as the backup heat and letting an outdoor temperature setpoint decide which appliance runs, which does not apply to most heat pump replacements since the backup in these houses is already electric. If your house is the other kind, a heat pump outside and a gas furnace inside, the furnace's age joins the same decision. Emergency heat locks the compressor out and runs the house on strip heat alone. It is for the week you are waiting on a part.
"The call I get on these is almost always the same. Fifteen year old unit, third repair in two winters, and the strip heat has been carrying the house since Thanksgiving. Hanging the new equipment is the easy part of my day. What decides whether the new one is actually better is the line set, the coil match, and whether somebody set the lockout off a real balance point instead of leaving the thermostat the way the old one was wired." Jake Mazzoccoli, Owner, TerraStream Energy
How Big This Job Gets
The Smallest Version of the Work
Replacing a heat pump with a heat pump is the smallest whole system job there is in a Maryland house, and the reason is everything the first install already paid for.
The ducts are in, and the 240 volt circuit is in and sized for a heat pump rather than a condenser alone. The pad is poured, the lines are run, the air handler has a place to live. No gas line to cap, no flue to abandon, no panel work in the usual case. Getting a gas heated house off gas costs more than this work does, and most of that difference is the parts of an install your house already has.
Smallest does not mean quickest. Even this version starts with a Manual J, the room by room heat loss and heat gain calculation defined in ACCA's technical manuals, because the nameplate on the old pad is evidence of what somebody picked in 2009 rather than of what the house needs now. Windows get replaced, attics get insulated, additions get built, and plenty of equipment from that era was oversized the day it went in.
TerraStream Energy replaces an aging heat pump with a new high efficiency system as whole system work, covering the outdoor unit, the indoor air handler and coil, the controls, and the commissioning that makes the first two behave. That replacement work is single family residential, and heat pump out, heat pump in is the most contained version of it.
What Makes It Grow
Five things turn a contained swap into a bigger project, and four of them are visible before anything comes off the pad.
First, a line set that cannot be reused and cannot be reached. Copper run through a finished wall, a chase with no access, or a slab turns an hour of work into drywall and a plan. Second, an indoor coil and air handler that have to change in a space which barely fit the last ones, bringing the drain, the platform and sometimes an attic walkway with them. Third, static pressure the ducts cannot support, which is a separate trade and a separate decision rather than something absorbed into an equipment quote.
Fourth, electrical that does not line up with the new nameplate, or a heat kit size change that moves the indoor circuit. Fifth, a load calculation that lands somewhere other than where the old nameplate sat. A house needing less capacity than the old unit made is good news, and it still changes the airflow assumptions the original install was built on.
One growth item stays invisible until the system is open. An R-22 system, or any system that lost a compressor electrically, can carry contamination nobody sees from the driveway. Anyone quoting that house without saying what happens if the lines turn out dirty is quoting a best case. Prince George's County also requires a mechanical permit to replace heating and cooling equipment, and the county takes that application from a licensed contractor, so settle in writing who pulls it before equipment is ordered.
How TerraStream Energy Would Approach This
A heat pump replacement gets decided by the survey rather than by the brochure, and on this job the survey is shorter than it is on a gas conversion.
TerraStream Energy starts in the house rather than with a model number. Room by room measurements for the load calculation. Static pressure read across the existing air handler, since airflow the ducts cannot deliver caps what any equipment can do there. Data plates on both ends, the kW of the heat kit, the line set route and diameters, whether the copper is reachable end to end. The panel cover comes off to read the breaker and conductor against what the new unit asks for.
TerraStream Energy runs the Manual J before selecting equipment, then pulls the heating capacity of the proposed combination at the Maryland winter design temperature from the manufacturer's extended table and states the balance point in writing. Backup heat gets sized to the gap above that point rather than copied from the old kit. TerraStream Energy pressure tests and evacuates the system with a micron gauge before charge goes in, then sets the auxiliary lockout and the thermostat staging at startup instead of leaving factory defaults in place.
This work is single family residential in Maryland, with Prince George's County first. TerraStream Energy replaces whole systems and does not run repair calls, maintenance agreements or duct work, which is worth knowing before you dial so you reach the right trade first.
What you should end up holding is paper. The Manual J output. The AHRI certified reference number for the combination that went in. Capacity at the design temperature, the balance point and the lockout temperature as it was left. The line set decision and why. The vacuum and pressure test results. Nameplate data for what was installed, refrigerant and charge weight included. That packet is what lets a homeowner answer questions about their own system three winters from now.
Incentive programs for heating equipment change from year to year, and so do the federal rules behind them. The Maryland Energy Administration lists current residential programs, and whatever is there should be confirmed before it goes into a budget. Nobody should plan a project around an incentive they have not verified.
If you own a single family home in Prince George's County or elsewhere in Maryland and your fifteen year old heat pump is losing the argument, call TerraStream Energy at 703-772-5970 or reach out here to start with the survey and the load calculation. Bring the data plate numbers. The conversation gets shorter when the measurements are already on the table.
Frequently Asked Questions
My heat pump is 15 years old and still runs. Should I replace it now or wait?
Wait if the only symptom is age. Replace on evidence. The evidence that counts is a sealed system failure, a control board replaced twice, R-22 on the data plate, or strip heat carrying hours it did not carry three winters ago at the same setpoint. A system that still holds the house through January and has only needed a capacitor or a contactor has time left. Planning ahead has one real advantage. Choosing equipment in October with a load calculation in hand produces a better result than choosing it on the coldest night of the year with no heat in the house.
Can my existing line set be reused with a new R-32 heat pump?
Often yes, if it is R-410A era copper of the right diameters, in good condition, with intact insulation and no buried joints. The manufacturer's installation instructions are the authority, since line sizing depends on your actual length and vertical rise. A line set that carried R-22 and mineral oil either gets flushed by the manufacturer's procedure or gets replaced, and after a compressor burned out electrically it gets replaced. Either way the lines should be pressure tested with nitrogen and evacuated to a deep vacuum verified with a micron gauge before any charge goes in.
Why is my strip heat running so much more than it used to?
Something on the compressor side has lost capacity, or the auxiliary lockout was never set. Slow refrigerant loss, worn compressor valves, a dirty outdoor coil, an outdoor fan moving less air, and defrost cycles running more often than conditions call for all shift hours onto the resistance coils. A thermostat with no lockout temperature energizes those coils whenever the room drifts behind setpoint, even at 45 degrees outside. Watch for the auxiliary or emergency indicator on a mild day, and compare January electric use across several years at the same setpoint.
Can I replace just the outdoor unit and keep my indoor coil?
Not with a result worth paying for. Efficiency and capacity are published for tested matched combinations, so a new outdoor unit on a fifteen year old coil has no published rating and will not deliver either number. The metering device is the bigger issue, since an old coil was matched to a compressor that ran at one fixed speed. Modulating equipment needs a coil and metering device designed for a range, and communicating product lines generally require their own air handler to modulate at all.
Do I need a permit to replace a heat pump in Prince George's County?
Yes. Prince George's County requires a mechanical permit to replace heating, ventilating and air conditioning equipment, and the county takes that application from a licensed contractor rather than from the homeowner. Confirm in writing which party is pulling it before equipment is ordered, and confirm that an inspection is part of the plan. Requirements and the county's submission process change, so check the current rule with the Department of Permitting, Inspections and Enforcement rather than relying on how a neighbor's job went five years ago.
Will a new heat pump keep up in a Maryland January better than my old one?
Yes, when it is selected off a load calculation and the manufacturer's capacity table at the winter design temperature. Variable capacity equipment holds useful output at temperatures where single stage units of the mid 2000s had already handed the house to the strip heat. The ENERGY STAR cold climate designation puts numbers on it, requiring a measured COP of at least 1.75 at 5 degrees Fahrenheit and at least 70 percent of the 47 degree capacity at that point. Sizing and the lockout settings decide the rest.
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