Grundfos Comfort PM Settings, Super Selectric Replacement Costs, and Pump Buying FAQ

Before the questions: I'm a procurement manager for a 45-person mechanical service contractor. I've managed roughly $1.1M in annual pump and HVAC-related spend for six years. I approve the POs and I track callbacks. I'm not a Grundfos engineer, so I won't invent a menu-by-menu manual here. My answers come from invoices, service logs, and corrections after jobs that didn't go perfectly.

Short version: compare total cost of ownership, not sticker price. Confirm the duty point before you order. Then set the pump to match the building, not the default in the box.

What do the Grundfos Comfort PM settings actually change?

PM on the Comfort pump labels I order stands for permanent magnet. That's a motor design. Because it's electronically commutated, the controller can vary speed. The settings tell the pump when to run and how to choose that speed.

For recirculation loops, I usually start on automatic or adaptive mode. It's a reasonable default, but I've seen an oversized pump hunt. The speed cycles up and down because one open tap is not enough load. When that happened, we switched to a lower fixed curve and the noise stopped. That's what fixed it in our buildings, so I don't treat the default as sacred.

The time and temperature settings matter as much as the mode. A recirculation pump running 24 hours in a building that only needs hot water 16 hours is wasting energy. Changing the run schedule can save more than switching motor technology.

Should I buy a Grundfos Super Selectric replacement?

If there's a Grundfos Super Selectric still working in your building, that's a credit to the old design. It does not mean you should buy the same series as a replacement. The series name matters less than the duty point on the label.

Take that duty point into the official Grundfos Product Center and see what current model matches. In a recent retrofit, our installer measured a working Super Selectric at 58 W on medium speed. The current permanent-magnet circulator at the same duty point drew 14 W. At $0.13/kWh, 44 W of continuous load costs about $50 per year. If pump replacement is already planned, that's a strong reason to choose the PM version. If the old pump is running fine and the system rarely runs, don't create a payback that isn't there.

What do I check before ordering a replacement?

Flange-to-flange length. Not just model number. The most expensive returned pump I've dealt with was ordered by model number alone. The replacement looked right in the catalog but was 12 mm longer than the old unit, and the pipes wouldn't flex. That turned a one-hour swap into a full day of pipe fitting.

Our field checklist now includes flange distance, union size, connection voltage, and pipe orientation. It's not glamorous. It's what prevents a second trip.

What is the crust made of?

Inside a pump, the white or tan crust is usually calcium carbonate. It's the same scale that builds up in a kettle. Hard water plus heat makes calcium carbonate come out of solution and deposit on shaft seals or impeller edges.

We learned that by paying for the same repair twice. At one apartment building, we replaced a leaking seal. Three weeks later it leaked again. When we opened the pump, there was crust on the shaft. It wasn't a pump defect. It was water chemistry. After the system got scale control, the new seal held.

Why is one Grundfos quote so much lower than the other?

In 2023, one distributor quoted $418 per pump for a batch of circulators. A second distributor quoted $481. On the surface, that's an easy decision. But the lower quote had freight and crating listed separately. The higher quote included delivery and a local rep who could swap a damaged unit. After we added the missing lines, the actual difference was under $40 per pump.

From the outside, the lower quote looks like efficiency. What it often hides is risk and handling. Our request-for-quote template now asks for an all-in delivered price. That one change saved us more money than the cheapest quote ever did.

When is a pump specialist most useful? When they tell you what not to buy.

I once had a supplier say that the permanent-magnet version was overkill for a low-head loop and that a standard Grundfos pump would do the job. It sounded like a strange sales move. It saved us money, and it earned them the next order.

A specialist should know strengths and limits. The Grundfos name doesn't fix a bad spec. If someone quotes a pump without checking system pressure, water chemistry, or duty point, the brand name alone is not enough.

What should I do before adjusting Grundfos Comfort PM settings?

Measure the pump first. Record the current power draw, the date, and the current run schedule. Change one setting at a time. Then check the farthest tap and the power draw again. I keep a one-page pump log for each building we service. Without a baseline, you're guessing, not managing.