Grundfos lists five control modes for its COMFORT recirculation pumps: continuous 24/7, temperature control, temperature+ control, a timer, and AUTOADAPT. Which ones you get depends on the pump variant. All except continuous operation aim to cut heat loss by running the pump only when hot water is likely needed.
Why do control modes matter?
Grundfos says the control modes reduce heat loss of the hot-water recirculation system by optimizing operating time, and that choosing the right one can save substantial heat energy. The Department of Energy's building science site says the best way to operate a recirculation pump is with demand-initiated controls. ENERGY STAR says recirculation systems that operate continuously have the potential to use more energy, due to energy spent pumping and hot water energy lost from the pipes, than the energy saved by reducing hot water waste. Our page on whether a recirculation pump is worth it covers that tradeoff for a Phoenix home.
What are the five modes?
| Mode | How it decides when to run |
|---|---|
| Continuous operation 24/7 | Runs whenever it has power |
| Temperature control | Starts when the internal sensor sees the water fall below a set threshold |
| Temperature+ control | Same idea, with an external sensor on the supply pipe and a vacation mode |
| Timer | Runs during hours you set |
| AUTOADAPT | Learns your hot water use and runs ahead of it |
Grundfos's booklet has a table showing which variant offers which mode: the plain COMFORT, COMFORT T, COMFORT TDT (TU) and COMFORT TA. Check the model on your nameplate before you count on a mode. Grundfos also says timer and temperature control can be enabled at the same time on the COMFORT TDT (TU).
### How does continuous operation work?
The pump operates continuously while connected to the power supply. Grundfos recommends this mode when the recirculation system must operate uninterrupted, or when the pump is connected to an external control unit.
### How does temperature control work?
The pump starts automatically when the sensor inside it detects that the water temperature has fallen below a set threshold. Grundfos says the threshold is updated automatically based on the maximum system temperature, which the pump measures for 15 minutes every 12 hours. You do not set a temperature by hand.
### How does temperature+ control work?
This mode is only available on COMFORT TA variants. It follows the same principle as temperature control, with these additions:
- Two sensors. The pump uses both an internal and an external sensor. The external sensor ensures a hot temperature in the supply pipe.
- Constant measuring. The maximum temperature of the system is measured constantly, so the start and stop temperatures adjust dynamically.
- Vacation mode. If water has not been tapped for 24 hours, the pump switches to vacation mode and turns off until it registers water being tapped 2 times within 80 minutes.
- Flushing. To keep the system sanitised, Grundfos says the pump flushes the system every 8 hours for 15 minutes.
The TA pump must be installed in the return line, and its external sensor must be mounted on the supply line. Grundfos says the sensor goes on the supply pipe 20 to 50 cm (8 to 20 inches) from the water heater. The sensor comes prewired with the pump, and its wire is 2.5 m (8 ft) long.
### How does the timer work?
COMFORT TDT variants have an integrated timer that lets you customize the pump's operating time. Grundfos says it eliminates unnecessary heat loss by restricting recirculation when no water use is expected. You set it on the pump's display in increments of 30 minutes.
If the power goes out, the timer pauses because it has no power reserve, but the selected operating times and the actual time are retained. When power returns, the pump resumes its last set operating state. Grundfos adds that if the outage lasts more than 15 minutes, the actual time may need to be reset. That differs from the older Comfort System dial, which stops keeping time in an outage.
### How does AUTOADAPT work?
AUTOADAPT automatically adjusts the pump to your actual hot water needs. Grundfos says it monitors your hot-water usage and optimizes operation to keep comfort while minimizing energy use, which makes it the most energy-efficient mode in the COMFORT range.
The pump detects hot water use through temperature changes at its internal and external sensors. A temperature rise at the supply-line sensor indicates use. The pump ignores temperature rises caused by its own operation. To learn your pattern, the pump must be switched on and set to AUTOADAPT mode, and Grundfos says this can take up to two weeks. During that period the pump runs in temperature+ control mode to reduce energy use while keeping hot water available.
Once the schedule is set, the pump predicts demand and starts ahead of time. It still runs in temperature+ control. When it stops according to the schedule, the AUTOADAPT LED flashes continuously. The controller tells normal use from unexpected demand and adapts to different patterns, including weekdays, weekends and vacation. The schedule keeps updating from logged use.
### What safeguards does AUTOADAPT add?
Two behaviors run in the background:
- Vacation mode. After 24 hours without detected hot water use, the pump enters vacation mode. It resumes normal operation once it detects 2 tapping events within 80 minutes.
- Flushing and disinfection. If the pump is inactive for 8 hours, it switches on and runs a 15-minute disinfection cycle to flush the recirculation loop, which Grundfos describes as a preventative measure against bacteria growth. In prolonged inactivity, the cycle runs once a week. If a higher temperature is measured at another time of the week, the run shifts to that time.
Grundfos does not claim these cycles make the system safe from Legionella or any other organism, and this page does not either. Building water safety rules for larger buildings are a separate topic, covered in our page on Legionella water management plans in Phoenix.
### What warning does the pump give?
The warning icon stays on permanently if the external temperature sensor is defective. The pump then keeps working in temperature control mode. Grundfos does not describe the repair, so a TA pump that shows the icon is a job for a dealer or plumber.
What are the operating specs?
The booklet lists these numbers for the range: maximum power consumption of 7 W for the COMFORT 15-14, 12 W for the COMFORT 15-14 XL and 6 W for the COMFORT 10-16, with a sound pressure level below 25 dB(A). It says the pump is for indoor installation only.
When should you call a plumber?
Call if a pump will not start, if the sensor needs to be mounted or replaced on the supply line, or if you are choosing a pump for a house without a return line. See our page on whether a Grundfos pump needs a return line first. HQ Plumbing & Air is licensed and insured, gives free estimates, quotes an upfront price, and offers 24/7 service.