Turn the programming ring until the timing arrow points to the current time, plug the pump in, then pick a mode with the manual switch: ON for nonstop pumping, TIMER to follow the tabs, or OFF for none. Each tab equals 15 minutes, and after a power outage you must reset the time.
How do you set the time of day?
Grundfos gives two steps:
- 1Turn the programming ring in the direction of the arrow on the timer face, until the timing arrow points to the current time.
- 2Plug the pump's 115 volt cable into a properly grounded 115 volt outlet. Route the cable so it does not touch the exhaust vent or pipe of a gas- or oil-fired water heater. The circulator starts and is ready for timer settings.
Before you start the circulator, Grundfos says to ensure the system is filled with liquid and vented. If you are installing the pump for the first time, our page on how to install a Grundfos Comfort System pump covers that step.
What are the three settings?
The manual describes three control options, chosen with the manual switch.
| Switch position | What the pump does |
|---|---|
| ON | Pumps continuously, 24 hours per day, 7 days per week. The programming tabs are ignored. |
| TIMER | Pumps according to the programming tab settings. |
| OFF | Does not pump. The timer still keeps the time of day. |
### How do the programming tabs work?
In TIMER mode, you decide the ON and OFF times by pushing the tabs. Grundfos says to push a tab away from the center ring to switch the circulator ON, and toward the center ring to switch it OFF. Each tab equals 15 minutes. A full day therefore has 96 tabs, since 24 hours contains 96 quarter-hours.
### What is a good schedule?
Grundfos suggests running the pump around your peak use times, such as 30 minutes before the first shower until 15 minutes after the last shower. Here is an example using that rule. Suppose showers happen between 6:30 and 7:30 in the morning. Starting 30 minutes early puts the pump on at 6:00. Ending 15 minutes after the last shower puts it off at 7:45. From 6:00 to 7:45 is 1 hour and 45 minutes, which is 7 tabs. The same math works for an evening block. The times in this example are ours. The 30-minute and 15-minute lead and lag come from Grundfos.
Your household may have a different pattern, such as a night shift or morning dishes. The Department of Energy's building science site says the best way to operate a recirculation pump is to use demand-initiated controls. A dial timer is a schedule, not a demand control, so it runs whether or not anyone needs hot water in a given block. Keep the blocks short and tied to the times you really use the water.
### How much less does a schedule run the pump?
Here is a second example, again with our own numbers. Say the household runs the pump from 6:00 to 7:45 in the morning (7 tabs) and from 5:30 to 8:00 in the evening (10 tabs). That is 17 tabs, or 4 hours and 15 minutes of pumping a day. The ON position would run the pump for all 24 hours. The example schedule uses less than a fifth of that run time. Grundfos does not give an energy figure for the timer, so treat this as arithmetic about run time, not a promise about your bill.
What happens in a power outage?
Grundfos says that in a power outage, the timer will not keep time. After the power is restored, reset the timer using the steps above. Because the timer stops keeping time during the outage, the dial no longer matches the real time of day until you reset it. It is worth glancing at the dial if your hot water arrives late one morning after the power blinked.
### Which position should you use when you are away?
The OFF position stops the pump and keeps the clock running, so the timer stays set for your return. Grundfos does not give travel advice in the manual, and how long a house should sit without pumping is your call. If you leave your house for months, our snowbird plumbing checklist for Arizona covers the water heater and the rest of the plumbing.
What if the pump does not run?
Grundfos's fault finding table lists three causes for a pump that does not run, each with a remedy:
- The pump is not connected to the power supply. Connect it.
- The circuit breaker has tripped. Cut in the circuit breaker.
- The pump is defective. Replace the pump.
Before you assume the pump is defective, check the switch position. In OFF, the pump does not pump by design, and in TIMER it only runs during the ON tabs. If you want the pump to run right now to test it, move the switch to ON.
If the pump runs but you do not get hot water quickly at the far faucet, the manual points to the bypass valve. It lists an improperly installed valve as the cause of "no hot water at the faucet or too much hot water on the cold water side," and says to review the valve installation and reinstall it if necessary. Our page on why hot water depends on a recirculating pump covers related symptoms.
### Does the Comfort System need maintenance?
Grundfos says the Comfort System is maintenance free and that no service is required. That covers the pump and valve. The timer setting is the one thing that needs your attention, mostly after an outage or a change in your household's routine.
When should you call a plumber?
Call if the pump never runs after you check the plug, breaker and switch, if there is a leak at the pump or the under-sink valve, or if hot water does not reach the far faucet quickly even though the pump is running. HQ Plumbing & Air is licensed and insured, gives free estimates, quotes an upfront price, and offers 24/7 service.