Heat PumpsHeat Pump System
Johnson Controls THF2B42T21 + XAHD48FBCN1 Heat Pump System · AHRI 212415879
Certified ratings, sizing notes, operating tips and maintenance for this 3.5-ton split-system heat pump combination.
- SEER216.0
- HSPF28.1
- Cooling40,500 Btu/h
- Heat at 5 °F22,200 Btu/h
About this heat pump system
AHRI reference 212415879 certifies the Johnson Controls THF2B42T21 outdoor unit paired with indoor unit XAHD48FBCN1 and furnace Z8ET120C20LMPS1 as a matched split-system heat pump system.
As a matched system it is rated at 16.0 SEER2, 11.7 EER2 and 8.1 HSPF2, delivering 40,500 Btu/h of cooling (about 3.5 tons) and 40,500 Btu/h of heating at 47 °F. At 5 °F it still produces 22,200 Btu/h — 55% of its 47 °F output with a COP of 2.34.
A two-stage compressor runs on a low stage most of the time and switches to high stage only on the hottest and coldest days, improving comfort and efficiency over single-stage equipment.
Specifications
| Brand | Johnson Controls |
|---|---|
| Outdoor unit model | THF2B42T21 |
| Indoor unit model | XAHD48FBCN1 |
| Furnace model | Z8ET120C20LMPS1 |
| AHRI reference number | 212415879 |
| SEER2 | 16.0 |
| EER2 | 11.7 |
| HSPF2 | 8.1 |
| Cooling capacity | 40,500 Btu/h |
| Heating capacity at 47 °F | 40,500 Btu/h |
| Heating capacity at 17 °F | 25,800 Btu/h |
| Heating capacity at 5 °F | 22,200 Btu/h |
| COP at 5 °F | 2.34 |
| Compressor staging | Two-stage |
| Refrigerant | R-410A (GWP:2088) |
| ENERGY STAR cold climate | No |
| Meets peak cooling (EER2) requirement | Yes |
| Connected capability | No |
| ENERGY STAR Most Efficient | No |
How it compares with other THF2B42T21 matches
The THF2B42T21 has 419 certified matches. This one's 16.0 SEER2 is higher than 234 of them (56%). The matches with the closest efficiency are listed below.
| AHRI ref. | Indoor unit | SEER2 | EER2 | HSPF2 | Cooling Btu/h |
|---|---|---|---|---|---|
| 212485804 | XAHC48FBCN1with furnace Z8ES080B12LMPS1 | 16.0 | 12.0 | 8.1 | 40,000 |
| 212475874 | XAHD48FBCN1with furnace Z8ES080C16LMPS1 | 16.0 | 12.0 | 8.1 | 41,000 |
| 212485790 | XAFD48FBCN1with furnace Z8ES080C20LMPS1 | 16.0 | 11.7 | 8.1 | 40,500 |
| 212416014 | XAHD48FBCN1with furnace Z8ET080C16LMPS1 | 16.0 | 12.0 | 8.1 | 41,000 |
| 212478314 | XAFD48FBCN1with furnace Z8ES080C16LMPS1 | 16.0 | 11.7 | 8.1 | 41,000 |
| 212416024 | XAHC48FBCN1with furnace Z8ET080C16LMPS1 | 16.0 | 12.0 | 8.1 | 41,000 |
| 212415904 | XAFC48FXXN1+TXVwith furnace Z8ET120C20LMPS1 | 16.0 | 11.7 | 8.1 | 40,500 |
| 212416354 | XAHD48FBCN1with furnace Z8ES080C16SMPS1 | 16.0 | 12.0 | 8.1 | 41,000 |
| 212416379 | XAFC48FXXN1+TXVwith furnace Z8ES080C16SMPS1 | 16.0 | 11.7 | 8.1 | 41,000 |
| 212416034 | XAFD48FBCN1with furnace Z8ET080C16LMPS1 | 16.0 | 12.0 | 8.1 | 41,000 |
| 212416174 | XAFC48FXXN1+TXVwith furnace Z8ES120C16SMPS1 | 16.0 | 11.7 | 8.1 | 41,000 |
| 212482950 | XAHC48FBCN1with furnace Z8ES120C16LMPS1 | 16.0 | 11.7 | 8.1 | 41,000 |
Safety information
- Installation, refrigerant charging and electrical connection must be performed by a licensed HVAC contractor in accordance with local codes and the manufacturer's installation instructions. Many jurisdictions require a permit and inspection.
- Turn off power at the outdoor disconnect and at the main panel before opening any service panel. Capacitors can hold a dangerous charge after power is removed.
- Keep children and pets away from the outdoor unit; never insert objects through the fan guard.
- Do not operate the system with panels or the fan guard removed.
- If a gas furnace provides backup heat, make sure carbon monoxide alarms are installed on every level of the home and near sleeping areas.
Installation and sizing
Proper installation matters more than any rating on the label: field studies show that incorrect charge, poor airflow and leaky ducts can cut real-world efficiency by 30% or more. Use the checklist below when reviewing quotes for the Johnson Controls THF2B42T21.
- Load calculation
Insist on a room-by-room heat-loss and heat-gain calculation (ACCA Manual J) before choosing a size. Oversized heat pumps short-cycle, dehumidify poorly and wear out sooner; rule-of-thumb sizing by square footage is unreliable.
- Verify the matched system
Confirm the outdoor unit, indoor coil or air handler (and furnace, if any) match an AHRI certificate. Mismatched components can lower efficiency well below the published ratings and may void rebates.
- Outdoor unit placement
Set the condenser on a level pad raised above expected snow depth, with at least 12–24 in. of clearance around the coil and 5 ft above the fan. Avoid spots under roof drip lines where ice can fall onto the unit.
- Ductwork and airflow
Have the contractor measure static pressure and set blower airflow (typically 350–450 CFM per ton). Leaky or undersized ducts are the most common reason a new system underperforms.
- Line set and charge
The refrigerant line set should be pressure-tested, evacuated to 500 microns or lower and charged by weight and verified by subcooling or superheat as the manufacturer specifies.
- Commissioning
Ask for a commissioning report showing airflow, refrigerant charge readings, thermostat configuration (including auxiliary-heat lockout) and a test of defrost operation.
Using your heat pump
Thermostat settings
Pick a comfortable setpoint and leave it. Heat pumps are most efficient when they hold a steady temperature; deep night setbacks in heating mode can trigger expensive auxiliary (strip) heat during recovery. If you use setbacks, limit them to 2–3 °F or use a thermostat with adaptive recovery designed for heat pumps.
Heating mode and defrost
In cold, damp weather frost builds up on the outdoor coil. The unit periodically reverses into a defrost cycle for a few minutes — you may see steam rising from the outdoor unit and hear a whoosh when the reversing valve shifts. This is normal.
Heating output drops as outdoor temperature falls. Below the system's balance point a backup heat source (electric strips or a furnace) supplements the heat pump; your installer should set the thermostat so backup heat runs only when needed.
Cooling and dehumidification
For better humidity control in summer, use the "Auto" fan setting rather than "On" so moisture collected on the indoor coil can drain away instead of re-evaporating into the house.
Care and maintenance
| When | What to do |
|---|---|
| Every 1–3 months | Check the air filter and replace it when dirty (1 in. filters usually monthly to quarterly; 4–5 in. media filters every 6–12 months). |
| Monthly in season | Keep 2 ft clear around the outdoor unit: remove leaves, grass clippings, snow and ice. Never cover the unit while it is in use. |
| Each spring | Gently hose the outdoor coil from the inside out with power off; straighten bent fins with a fin comb. |
| Each fall | Confirm the condensate drain is clear and the outdoor unit is level and not sinking into the ground. |
| Every year | Schedule professional maintenance: electrical connections, capacitor test, refrigerant charge check, coil cleaning, blower and drain service, and a defrost test. |
Troubleshooting
| Problem | Possible cause | What to try |
|---|---|---|
| No heating or cooling | Thermostat in wrong mode; tripped breaker or blown fuse; outdoor disconnect off. | Check mode and setpoint; reset the breaker once; confirm both indoor and outdoor disconnects are on. If it trips again, call a technician. |
| Steam from the outdoor unit in winter | Normal defrost cycle. | No action needed; defrost typically lasts 2–10 minutes. |
| Outdoor unit covered in ice | Defrost control or sensor fault; low refrigerant; blocked airflow; gutter dripping on unit. | Clear snow and debris; redirect dripping water. If the coil stays encased in ice for hours, switch to emergency heat and call for service. |
| Air from vents feels lukewarm in heating | Heat pumps deliver air around 90–100 °F, cooler than a furnace. | Normal. Check that the house is reaching setpoint rather than judging by air temperature. |
| High electric bills in winter | Auxiliary strip heat running too often; deep setbacks; dirty filter. | Reduce setbacks; ask your contractor to set an aux-heat lockout; replace the filter. |
| Short cycling | Oversized system; thermostat near a supply register; refrigerant or control issue. | Relocate the thermostat if needed; have the contractor verify sizing and charge. |
| Water dripping indoors | Clogged condensate drain or pump; dirty coil; frozen evaporator. | Turn the system off and clear the drain line; if ice is visible on the coil, check the filter and airflow before restarting. |
| Unusual noises (grinding, squealing) | Fan motor bearings; debris in the fan; loose panel. | Turn the system off and call a technician — continued operation can damage the compressor or motor. |
Energy use and running costs
Assuming 1,000 full-load cooling hours per year (typical of a moderate U.S. climate), this system would use roughly 2,531 kWh for cooling — about $430 at $0.17/kWh.
For heating, 1,500 full-load hours at 8.1 HSPF2 works out to about 7,500 kWh, or $1,275 per year, excluding any auxiliary heat. The same heat from an 80% AFUE gas furnace would cost about $1,139 at $1.50/therm.
Your actual cost depends on climate, home insulation, thermostat habits and local utility rates. Use these figures to compare models rather than as a bill forecast.
Frequently asked questions
What is the SEER2 rating of AHRI 212415879?
This Johnson Controls THF2B42T21 + XAHD48FBCN1 system is rated at 16.0 SEER2, 11.7 EER2 and 8.1 HSPF2.
How many tons is this Johnson Controls heat pump system?
Its rated cooling capacity is 40,500 Btu/h, which is about 3.5 tons (12,000 Btu/h per ton).
How well does this system heat in very cold weather?
It is rated for 22,200 Btu/h at 5 °F with a COP of 2.34, meaning it delivers about 2.3 units of heat per unit of electricity. It does not meet the ENERGY STAR cold-climate criteria, so plan for backup heat in cold regions.
What refrigerant does this system use?
R-410A (GWP:2088).
Can I use a different indoor unit with this outdoor unit?
Yes, but the ratings on this page apply only to this exact AHRI-certified combination. The THF2B42T21 has other certified matches listed on its main page, each with its own ratings.
Sources and disclaimer
Specifications on this page come from the ENERGY STAR certified heat pumps dataset published by the U.S. Environmental Protection Agency (record certified July 6, 2026), retrieved October 7, 2026. The AHRI reference number identifies the certified combination; verify it in the AHRI Directory of Certified Product Performance before purchase.
The setup, operating, maintenance and troubleshooting guidance is written by ManualHarbor's editors for this specific product type and configuration. It is an independent guide — not a reproduction of the manufacturer's manual — and ManualHarbor is not affiliated with Johnson Controls. Always follow the safety instructions, installation requirements and warranty terms supplied with your unit, and contact Johnson Controls or an authorized service provider for warranty repairs and replacement parts.
Running-cost figures use assumed U.S. average utility prices and are estimates for comparison only. See our editorial methodology for details.
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