Why Your Danfoss Pressure Switch Order Got Rejected (And How to Fix It Before You Order)

If you're reading this, you're probably one of the lucky ones—you caught the rejection notice before the job site started yelling at you. Or you're the unlucky one holding a box with the wrong switch, wondering how the part number was right but the everything else was wrong.

I've been handling industrial HVAC parts orders for about 7 years now. When I started in 2018, I was the guy who made the classic mistakes—ordering a KP 15 when the callout was for an MBC 5100, just because the pressures looked similar. The first time that happened, it was a $1,800 mistake (expedited shipping + restocking fees). After the third rejection in Q1 of 2022, I finally created a pre-order checklist that I now force every new hire in our department to use. It's caught us 47 potential errors in the last 18 months alone.

Here's the checklist I essentially wrote by failing. If you use it before ordering a Danfoss pressure switch (especially for the KP, RT, or MBC series), you'll save yourself a headache. And money.

Step 1: Nail the Series—It's Not Always Obvious

This sounds basic, but it's where I see the most confusion. People assume because a KP35 and an RT 116 both handle differential pressure, they're interchangeable. They are not.

Your first filter is the series:

• KP Series (KP1, KP5, KP15, KP35): These are your workhorses for HVAC/R. KP1 and KP5 are common for general pressure control. KP15 and KP35 are for differential pressure (like across a filter). The KP5 is especially common on smaller compressor applications. Look for the specific model number on the old switch's label—the sticker usually also lists the code number (like 060-xxxxxx).
• RT Series (RT 116, RT 260L): These are heavier-duty industrial switches. The RT 260L is a beast for oil differential pressure control on larger refrigeration oil management systems. The RT 116 is a high-pressure switch. If you're dealing with a Danfoss oil pump (like the MBP 100), you're probably looking for an RT switch.
• MBC 5100 / MBC 8100: This is a newer, compact differential switch designed for refrigeration applications. It competes with some older KP models. If a system diagram shows 'MBC 5100', don't try to sub in a KP 15. They have different pressure ranges and, more importantly, different mounting brackets.
• MP 55: This is a single-pressure switch for simple applications. Not as common to confuse, but I've seen people try to use an MP 55 for differential duty. That's a short-term fire waiting to happen.

My mistake: I once ordered an RT 260L thinking it could replace a faulty MBC 5100. They looked the same size and had similar 'oil diff' in their descriptions. The pressure differential range was different, but the killer was the wiring terminals—the MBC uses flat-blade connectors, the RT uses screw terminals. $320 in parts, but I had to return them and pay for expedited air shipping on the correct ones. Cost me the budget for the month.

Step 2: Verify the Cut-In / Cut-Out Pressure (This is the Most Common Rejection Reason)

This is it. The big one. I'd say 60% of order rejections I see come down to getting the pressure settings wrong.

A Danfoss pressure switch has two numbers that matter: the cut-in pressure (when the switch turns on) and the cut-out pressure (when it turns off). You have to verify these against your system requirements.

People look at a datasheet and see a range like '1.5–12 bar' and think it's universal. Wrong. That's the adjustment range. The actual switch you order or the one on the shelf might be set for a different range than your system needs.

How to avoid this:

• Look at the existing switch's label. It almost always shows the setpoint or the range it was set to at the factory. If it just shows '4 bar (cut-in) / 6 bar (cut-out)' on a sticker, that's your target.
• Check the system's technical manual. If it's for a compressor pack from Bitzer or Copeland, the manual will specify the pressure switch settings.
• If the old switch has no sticker (common after a few years), you need to measure the system's operating pressures. Don't guess. I promise you, guessing is more expensive than taking the time to measure.

Most industrial KP5 switches, for example, have an adjustable range, but the range might be 'Pressure 4–7.5 bar' for one part number and 'Pressure 8–12 bar' for another. Ordering the 'Pressure 4–7.5 bar' variant when your system runs at 10 bar is a non-starter.

Step 3: Check the Code Number (060-xxxxxx)—Your Paper Trail Starts Here

Every genuine Danfoss pressure switch has a 6- or 7-digit code number printed on the label. For the KP series, it usually starts with '060-'. For the RT and MBC series, it's a similar format.

This code number tells you everything: the exact model, the pressure range, the connection type (flare, solder, NPT, ISO), and the electrical specifications (like the contact type—SPDT or DPST).

Why this matters more than the model name: A KP5 could be code number 060-112266 (for R134a, with a 7.5 bar pressure range and a 3/8" flare connection) and another KP5 could be 060-112267 (for R404A, same pressure, but with a 1/4" female flare connection). Same model name, different application.

Action item for your checklist: Before you finalize the order, cross-reference the code number against the Danfoss datasheet. I keep a PDF of the KP and RT series datasheets (the official ones from the Danfoss website) accessible on my order desk. If you can't find the code number, trace it from the old part. If the label is worn off, order based on the system coding (which is risky—I have done this and learned my lesson).

Step 4: Don't Forget the Connection & Mounting

This is the step that catches people who are focusing on pressure ranges. You can have the perfect electrical and pressure specs, and still fail on the physical interface.

• Process Connection (the part that goes into the pipe/vessel): Is it 1/4" flare? 1/2" NPT? 7/16"-20 UNF? A G1/2? The KP series often comes with either a flare or a straight thread. The MBC 5100 often uses a 1/4" flare. If you have a 3/8" flare on an old system and order a 1/4" flare, you need an adapter. That's fine if you plan for it. It's a nightmare if you don't realize until you're at the site.
• Capillary Tube Length (if applicable): Some Danfoss switches (like some RT series with a remote sensor) have a capillary tube. Are you ordering the right length? A 200cm tube vs a 100cm tube is a different part. I once saw a purchase order for an RT 116 with a 300 cm capillary when the system needed 150 cm. The extra tubing had to be coiled up and zip-tied, which creates a potential break point.
• Mounting Bracket: The KP series uses a standard bracket. The MBC 5100 uses a different bracket. The RT series often needs a separate mounting kit. Check if the bracket is included in your order. Nothing is more frustrating than paying for a rush order and then realizing you need a $10 bracket that you forgot.

Step 5: Verify the Electrical Contacts (Voltage & Functionality)

This is less common as a rejection reason, but I've seen it enough to include it. A Danfoss pressure switch is an electrical switch. Make sure the contact type matches your control circuit.

• Function: Is it a normally open (NO) or normally closed (NC) contact? The application determines this. A safety pressure switch for high pressure is usually NC (it opens on high pressure to shut down the compressor). A differential switch to indicate a dirty filter might be NO (it closes on high pressure to send a signal). The datasheet for the code number will tell you this.
• Electrical rating: For most industrial PLC or relay circuits, the standard 10-16A rating is fine. But if you have a very low voltage (24V AC/DC) or require gold-plated contacts for low current, check the specs. The standard KP switches can handle 10A at 250V, which covers 90% of cases, but always verify.

What to Do If You're Still Not Sure (The 20% Rule)

Honesty time: This checklist covers the 80% of obvious errors. There will be a 20% of cases where you have a system that uses a non-standard pressure switch, or an old system with a superseded model. You know what I do in those cases?

I do not just order by the highest-rated part. I call the technical support line. Or I use the Danfoss Selector tool on their website (it's free and lets you filter by pressure, connection, and code number). If I'm ordering for a very specific, safety-critical compressor system (like an oil pressure switch on a semi-hermetic compressor), I talk to a human. It's not admitting failure; it's avoiding a $4,000 compressor burnout because the oil differential switch failed to trip.

The conventional wisdom is that you should just order the same model you took off. But experience has taught me that 'same model' often gets misinterpreted. The switch you took off had a worn label. The model you're ordering from a chart doesn't match. Follow the checklist. It's saved me well over $10,000 in mistakes over the last few years. It'll save you a few hundred on your next order, at the very least.

Prices for Danfoss industrial pressure switches (based on current online distributor quotes, general reference; verify current rates):

• KP5 series (basic): $65–$95
• KP35 / KP15 series (differential): $90–$130
• RT 260L (oil): $160–$220
• MBC 5100: $110–$150

Always verify the code number. It's the single best way to avoid a rejection.