Laundry wash water and dryer air from heat pumps
How an industrial laundry washing 4 tonnes of linen a day can make its 60–90 °C wash water and preheat tumble dryer air with heat pumps, against a diesel-fired steam boiler.
▶Video: Heat pumps for textile and leather processing
V03 · 2–2.5 minDyeing, pre-treatment and tanning, with heat recovered from hot drain water
Video coming soon01Problem statement
- Hot water in short bursts. Washer-extractors fill quickly at the start of each wash, so the boiler has to meet sharp peaks.
- Disinfection temperature. Hospital linen needs a sustained hot wash. A boiler that cannot keep up lets wash temperatures drop.
- Dryers heat cold air. Tumble dryers draw in ambient air and heat it with steam coils or gas, which is one of the largest energy users in the laundry.
- Losses between fuel and process. Burning diesel in a boiler or heater and distributing the heat loses a quarter or more of the fuel's energy before it reaches the process.
- Compliance, safety and handling. Fired equipment brings boiler inspections, fuel storage and unloading, flue emissions and an attendant on every shift.
02Use case
The reference laundry serves hotels and hospitals, washing 4 tonnes of linen a day in washer-extractors over two shifts. Three tumble dryers dry towels and blankets, and flatwork goes to a steam ironer.
| Heat user | Process temp. | Basis | Heat, kWh/day |
|---|---|---|---|
| Main wash water | 75 °C | 4,000 kg × 3 L/kg = 12,000 L, 28 → 75 °C | 655 |
| Pre-wash and rinse water | 45 °C | 4,000 kg × 4 L/kg = 16,000 L, 28 → 45 °C | 316 |
| Tumble dryer air preheat | Air 35 → 80 °C | 2,400 kg/h air × 1.005 kJ/kg·K × 45 K = 30.2 kW × 12 h | 362 |
| Storage and pipework standing losses | – | about 5% | 67 |
| Total useful heat | 1,399 | ||
Averaged over 16 running hours, the heat pumps need about 87 kW.
03P&ID
Tags: HP heat pump, TK tank, SG steam generator, P pump, PHE plate heat exchanger, TCV temperature control valve, TIC temperature indicating controller (panel), TT temperature transmitter, MT moisture transmitter, PT pressure transmitter, LT level transmitter, FS flow switch, NC normally closed. Process fluids are heated through their own exchanger, coil or jacket.
04Solution
System description
- 2 × SE-SHT-50C (100 kW total) (SE-SHT cascade heat pump) delivering 90 °C, covering the day's 1,399 kWh in about 14.0 running hours.
- A 3,000 L insulated storage tank decouples the heat pumps from the process peaks.
- The diesel-fired steam boiler stays connected behind a normally closed valve as standby.
- The heat pumps charge a storage tank sized for the morning washer fill peak, so washers get 75 °C water on demand.
- A separate warm tank supplies pre-wash and rinse water at 45 °C.
- Hot-water coils on the tumble dryer intakes preheat air to about 80 °C, and the existing dryer heaters top up.
Selected equipment
| Model | SE-SHT-50C × 2 |
|---|---|
| Heating capacity | 50 kW each, 100 kW total |
| COP | 2.6 at A20 °C / W90 °C (data sheet T1) |
| Power input | about 37.2 kW total at rated conditions |
| Rating | cascade R410A + R515B, rated 90 °C, 95 °C maximum |
| Supply temperature | 90 °C |
| Storage | 3,000 L insulated tank |
Ratings from the Sunniva TDS 2026 data sheets.
Control philosophy
TT-101 starts the heat pumps below 82 °C and stops them at 90 °C, and TT-102 at the tank bottom starts them early before the first wash. TIC-201 to TIC-203 hold each user at set-point. The steam boiler remains standby for the ironer and for peak days.
05Energy saving and ROI
Change any input to match a customer's site. Defaults are typical Indian prices for October 2026. The installed cost is a placeholder; replace it with the actual quotation.
| Existing | Heat pump | |
|---|---|---|
| Daily consumption | – | – |
| Annual energy cost | – | – |
| Cost per tonne of linen | – | – |
| CO₂ per year | – | – |
06Benefits
Wash temperature held
Stored water at 75 °C keeps the main wash at its disinfection temperature through peak fills.
Faster drying
Preheated intake air cuts tumble dryer heating time and gas or steam use.
Smaller boiler load
The boiler serves only the ironer, so it runs at steadier load.
Lower energy cost
Each kWh of electricity delivers about 2.6 kWh of heat at the required temperature, against well under one kWh of useful heat per kWh of fuel burnt.
No flame on site
No burner, flue or fuel tank for this duty, and no fuel deliveries to schedule.
Built-in redundancy
Several machines share the load. If one is serviced, the others and the storage carry most of the day, with the existing heater in reserve.
07Engineering pointers
Site data to collect
- Linen washed per day and wash programmes
- Water use per kilogram by stage
- Tumble dryer number, airflow and heat source
- Boiler fuel use per day
- Shift pattern and peak fill times
- Present fuel or electricity use and monthly bill
- Sanctioned electrical load and spare capacity
- Space for the heat pumps and storage, with service access
- Winter minimum ambient at site
Design notes
- Ironers stay on steam. Flatwork ironers need steam well above heat pump temperatures. Keep them on the boiler.
- Lint on coils. Dryer air carries lint. Fit the coils on the fresh-air intake side with a filter, and clean lint screens daily.
- Drain heat recovery. A simple drain-to-fresh-water exchanger can preheat mains water before the heat pump tank. Check whether one is fitted before sizing.
- Electrical. About 37 kW of heat pump input at rated conditions, plus pumps and fans. Check spare sanctioned load before ordering.
- Winter output. The SE-SHT cascade gives about 80% of rated output at 7 °C ambient and still runs at −20 °C. Size on the coldest design day for northern sites.
- Water quality. Scale forms quickly above 60 °C. Use softened make-up and keep the heat pump loop closed, with process fluids on the far side of an exchanger or coil.
Service and warranty
Sunniva has supplied 5,000+ heat pumps since 2012, with nine service technicians across India, including remote sites such as Leh. All components carry a one-year warranty.
Talk to us
Laundry wash water and dryer air from heat pumps
How an industrial laundry washing 4 tonnes of linen a day can make its 60–90 °C wash water and preheat tumble dryer air with heat pumps, against a diesel-fired steam boiler.
▶Video: Heat pumps for textile and leather processing
V03 · 2–2.5 minDyeing, pre-treatment and tanning, with heat recovered from hot drain water
Video coming soon01Problem statement
- Hot water in short bursts. Washer-extractors fill quickly at the start of each wash, so the boiler has to meet sharp peaks.
- Disinfection temperature. Hospital linen needs a sustained hot wash. A boiler that cannot keep up lets wash temperatures drop.
- Dryers heat cold air. Tumble dryers draw in ambient air and heat it with steam coils or gas, which is one of the largest energy users in the laundry.
- Losses between fuel and process. Burning diesel in a boiler or heater and distributing the heat loses a quarter or more of the fuel's energy before it reaches the process.
- Compliance, safety and handling. Fired equipment brings boiler inspections, fuel storage and unloading, flue emissions and an attendant on every shift.
02Use case
The reference laundry serves hotels and hospitals, washing 4 tonnes of linen a day in washer-extractors over two shifts. Three tumble dryers dry towels and blankets, and flatwork goes to a steam ironer.
| Heat user | Process temp. | Basis | Heat, kWh/day |
|---|---|---|---|
| Main wash water | 75 °C | 4,000 kg × 3 L/kg = 12,000 L, 28 → 75 °C | 655 |
| Pre-wash and rinse water | 45 °C | 4,000 kg × 4 L/kg = 16,000 L, 28 → 45 °C | 316 |
| Tumble dryer air preheat | Air 35 → 80 °C | 2,400 kg/h air × 1.005 kJ/kg·K × 45 K = 30.2 kW × 12 h | 362 |
| Storage and pipework standing losses | – | about 5% | 67 |
| Total useful heat | 1,399 | ||
Averaged over 16 running hours, the heat pumps need about 87 kW.
03P&ID
Tags: HP heat pump, TK tank, SG steam generator, P pump, PHE plate heat exchanger, TCV temperature control valve, TIC temperature indicating controller (panel), TT temperature transmitter, MT moisture transmitter, PT pressure transmitter, LT level transmitter, FS flow switch, NC normally closed. Process fluids are heated through their own exchanger, coil or jacket.
04Solution
System description
- 2 × SE-SHT-50C (100 kW total) (SE-SHT cascade heat pump) delivering 90 °C, covering the day's 1,399 kWh in about 14.0 running hours.
- A 3,000 L insulated storage tank decouples the heat pumps from the process peaks.
- The diesel-fired steam boiler stays connected behind a normally closed valve as standby.
- The heat pumps charge a storage tank sized for the morning washer fill peak, so washers get 75 °C water on demand.
- A separate warm tank supplies pre-wash and rinse water at 45 °C.
- Hot-water coils on the tumble dryer intakes preheat air to about 80 °C, and the existing dryer heaters top up.
Selected equipment
| Model | SE-SHT-50C × 2 |
|---|---|
| Heating capacity | 50 kW each, 100 kW total |
| COP | 2.6 at A20 °C / W90 °C (data sheet T1) |
| Power input | about 37.2 kW total at rated conditions |
| Rating | cascade R410A + R515B, rated 90 °C, 95 °C maximum |
| Supply temperature | 90 °C |
| Storage | 3,000 L insulated tank |
Ratings from the Sunniva TDS 2026 data sheets.
Control philosophy
TT-101 starts the heat pumps below 82 °C and stops them at 90 °C, and TT-102 at the tank bottom starts them early before the first wash. TIC-201 to TIC-203 hold each user at set-point. The steam boiler remains standby for the ironer and for peak days.
05Energy saving and ROI
Change any input to match a customer's site. Defaults are typical Indian prices for October 2026. The installed cost is a placeholder; replace it with the actual quotation.
| Existing | Heat pump | |
|---|---|---|
| Daily consumption | – | – |
| Annual energy cost | – | – |
| Cost per tonne of linen | – | – |
| CO₂ per year | – | – |
06Benefits
Wash temperature held
Stored water at 75 °C keeps the main wash at its disinfection temperature through peak fills.
Faster drying
Preheated intake air cuts tumble dryer heating time and gas or steam use.
Smaller boiler load
The boiler serves only the ironer, so it runs at steadier load.
Lower energy cost
Each kWh of electricity delivers about 2.6 kWh of heat at the required temperature, against well under one kWh of useful heat per kWh of fuel burnt.
No flame on site
No burner, flue or fuel tank for this duty, and no fuel deliveries to schedule.
Built-in redundancy
Several machines share the load. If one is serviced, the others and the storage carry most of the day, with the existing heater in reserve.
07Engineering pointers
Site data to collect
- Linen washed per day and wash programmes
- Water use per kilogram by stage
- Tumble dryer number, airflow and heat source
- Boiler fuel use per day
- Shift pattern and peak fill times
- Present fuel or electricity use and monthly bill
- Sanctioned electrical load and spare capacity
- Space for the heat pumps and storage, with service access
- Winter minimum ambient at site
Design notes
- Ironers stay on steam. Flatwork ironers need steam well above heat pump temperatures. Keep them on the boiler.
- Lint on coils. Dryer air carries lint. Fit the coils on the fresh-air intake side with a filter, and clean lint screens daily.
- Drain heat recovery. A simple drain-to-fresh-water exchanger can preheat mains water before the heat pump tank. Check whether one is fitted before sizing.
- Electrical. About 37 kW of heat pump input at rated conditions, plus pumps and fans. Check spare sanctioned load before ordering.
- Winter output. The SE-SHT cascade gives about 80% of rated output at 7 °C ambient and still runs at −20 °C. Size on the coldest design day for northern sites.
- Water quality. Scale forms quickly above 60 °C. Use softened make-up and keep the heat pump loop closed, with process fluids on the far side of an exchanger or coil.
Service and warranty
Sunniva has supplied 5,000+ heat pumps since 2012, with nine service technicians across India, including remote sites such as Leh. All components carry a one-year warranty.