Danfoss Pressure Switch Buying Guide: Why the KP36 Is My Default, and What to Read Before You Order

For industrial refrigeration and compressor service, the Danfoss KP36 pressure switch is my default order—not because it is the cheapest quote, but because the total cost of ownership is usually lower than every generic alternative I have tracked. The first step is to download the Danfoss pressure switch manual PDF before you order, not after. If you only remember one thing from this article: match the exact pressure range, differential, and wiring diagram from the official manual, and treat the switch price as maybe 20% of the decision. Installation labor, downtime, and rework risk are the other 80%. Not the cheapest. Usually the most predictable.

Why this is written from a cost-control desk

I am a procurement manager at a 120-person industrial service company. I have managed a roughly $380,000 annual MRO budget for seven years, negotiated with more than 40 vendors, and documented every order in our cost tracking system. When I first started, I assumed a pressure switch was a commodity. That assumption cost us a $650 service call when a lower-priced unit drifted out of set point after three months. Not ideal. I now order the Danfoss when I want the switch that does not require a second trip.

When I compared two service sites side by side—one standardized on Danfoss KP-series switches, one using a mix of less expensive units—the biggest difference was not the first cost. It was the human cost. Our technicians spent more time fourth-guessing unknown switches and scheduling callback visits. The Danfoss site logged 31% fewer service callbacks over a year. That figure comes from our internal maintenance log, not from a manufacturer promise.

Danfoss KP36 and the rest of the family

KP36 is not the only Danfoss pressure switch, and the manual PDF will remind you of that. Depending on your system, you may need a KP15, KP35, RT116, MBC 5100, or a differential switch. The range is broad, and that is a good thing. But the product breadth means the real work starts with a specification, not a model name.

• KP15: often used in lower-pressure control circuits.
• KP35: common in high-pressure circuits.
• KP36: a versatile single-pressure switch that I keep in stock for many refrigeration and compressor controls.
• RT116: an older industrial control style still used as a direct replacement.
• MBC 5100: a compact option when panel space is tight.

I am not naming these to build a perfect comparison table. The point is that the official manual tells you which series fits your application. Use it.

Why the Danfoss Pressure Switch Manual PDF Is the Real Checklist

Danfoss publishes product documentation as PDFs, and I have been relying on those files for years. As of January 2025, the KP36 data sheet and installation guide are still available from danfoss.com. The manual includes wiring diagrams, set point ranges, differential settings, and electrical contact data.

Show a technician the wiring diagram from the official manual and your phone stops ringing. Hand them a switch and say it is standard and you will be back out there later.

I keep a folder on my desktop for every Danfoss component we stock. When a technician asks which wire goes where, the answer is already there.

When the compressor is down, certainty is the real product

In March 2024, we had a compressor off-line at a client plant. The replacement switch was an MBC 5100, and the normal shipment would have arrived in four days. Four days of partial production would have cost more than $3,000 in downtime. We paid $470 to rush it—no, $520 after the last-mile courier. Worth it. Absolutely. The added fee bought certainty, not just speed.

I get why people hesitate on rush shipping. Budgets are real. But I have rarely seen a missed deadline that was cheaper than the rush fee.

Filters: a side note that belongs in the same conversation

Search traffic around Danfoss pressure switches often includes hog hair air filters, spin-on oil filters, and the question 'is STP a good oil filter?' That makes sense: all those parts can live on the same compressor.

A clogged hog hair air filter can make a pressure switch behave erratically because it changes the airflow around the system. A spin-on oil filter with the wrong cross-reference can starve a compressor of oil pressure. If the pressure switch is giving you trouble, check the filters first. The switch might not be the problem.

To answer the question directly: STP makes decent automotive spin-on oil filters. For an industrial compressor, I would not use one unless the service manual lists it as an approved cross-reference. The same rule applies to any filter: use the number from the parts list, not a close enough guess. Should mention: in most of our jobs, the filter labor was already sunk because we were doing scheduled maintenance anyway.

Where I got burned

In my second year, I made the classic specification error: I ordered a KP35 when the system called for a KP36. I saw the Danfoss logo, checked the pressure range, and ignored the differential setting. The switch arrived, the technician asked if it was the right part, and I said yes. It was not. We paid a return fee, rushed the correct switch, and the wrong one sat on a shelf for a year.

That is why I now open the manual PDF before ordering. The quick-set scale on the switch body is only a starting point. The actual set points depend on the differential and the reset behavior. Skip that page, and you are guessing.

What to do before you order

1. Download the official Danfoss pressure switch manual PDF. As of January 2025, the latest versions are at danfoss.com.
2. Read the nameplate on the old switch. Write down the type designation, contact rating, and any stamped set point.
3. Match the pressure range, differential, and reset behavior to the manual.
4. If you are changing a filter at the same time, use the filter number in the service manual—not an automotive filter with a similar thread.
5. Decide between standard and rush delivery based on the cost of downtime, not just the difference in freight.

When I would buy something else

To be fair, a lower-priced switch can make sense in a non-critical application. If the system is a small cooler with an old compressor and you expect to replace the whole unit soon, a generic switch may be acceptable. If your maintenance team knows the quirks of a particular brand and keeps spares, that is their call.

For a critical production line, I would still start with the official spec and the manual PDF. The Danfoss range now covers many different enclosures, contact materials, and ambient temperature limits. The manual will tell you which version you need. Ignore those limits, and you will be back on site in the middle of July explaining why the switch did not handle the environment.