It was 6:50 on a Tuesday in late February 2025, and the building manager's text was short: "Heat pump 3 is down. Something with the pressure sensor. No heat in the east wing until we get a replacement." I was still holding my coffee. I didn't know what a pressure sensor looked like, let alone how to order one. That day turned into a crash course in AAON parts procurement, heat pump reliability, and why an outdoor heater should never be moved indoors.
This isn't a complaint about AAON. I've been in this building for five years, and the water-source heat pump units have done their job through some nasty summer weeks. But the moment a sensor fails, you find out how prepared you actually are. I wasn't.
The Morning the Heat Pump Went Silent
Quick background: I'm the office administrator for a 120-person company. I handle all the facility purchasing—office supplies, cleaning contracts, HVAC parts, and the occasional patio heater. My annual spend is roughly $90,000 across maybe 14 vendors. I took over this role in 2020, so I've had some practice. But my background is not HVAC. I know what a thermostat is, and I know who to call when the air stops working. I don't know a transducer from a transformer. I report to both operations and finance, which means every repair is also a budget conversation.
Our building uses a water-source heat pump system. I think we have eight AAON units total—wait, maybe nine. I'd have to walk the building. Anyway, they're commercial-grade water source heat pumps, and they run on a closed water loop. Most of the time, they work quietly. When they break, it's not a light bulb.
The maintenance ticket said "aaon suction pressure transducer." The building manager explained that the low-side pressure sensor sends a signal to the controller. If the signal is wrong, the compressor shuts down as a safety. We needed the same transducer, not a generic replacement, because the controller is picky. So I grabbed my phone and started searching for "aaon suction pressure transducer" and "aaon hvac distributors."
The Phone Calls I Shouldn't Have Needed to Make
The first place I found was a heating and cooling supply house about 40 minutes away. The woman on the phone was polite, but we got tangled. I said "we need this expedited." She heard "we need it ground, but put a rush on it." Result: when I checked the tracking number, the delivery date was Friday. That was a four-day wait for a part that probably cost us more in lost productivity than the part itself. (Honestly, I still don't know if the first distributor didn't have it or didn't want to say no.)
The second call was better. A small branch of an AAON distributor in a neighboring state had one in stock. They could ship it overnight, but the freight cost more than the part. We paid it. The part arrived at 10am the next day, a technician installed it in about 30 minutes, and the heat pump came back online.
I also called a third distributor who listed AAON on their website, but they only carried major assemblies like condenser coils and compressors, not small sensors. That was the first time I understood the difference between a parts distributor and a full-line stocking distributor. Knowing that distinction would have saved me one call.
The Outdoor Heater Detour
While the east wing was still cold, someone on the maintenance team suggested bringing in the propane heater off the patio. We have a 45,000 BTU commercial outdoor heater that we use for the smoking patio. It is not safe to run inside. It's made for open air, not for a hallway with a dropped ceiling. I know it seems obvious, but when people are cold, they stop thinking clearly.
We also priced a propane heater for emergency use. The ones that looked affordable were all outdoor units. The indoor-rated ones were bigger and needed venting. We didn't have time for that. We ended up with a temporary electric forced-air heater. (Surprise, surprise: the propane outdoor heater stayed outside.)
What Are the Disadvantages of a Heat Pump? Here's My Honest Answer
If you ask "what are the disadvantages of a heat pump?" online, you get a lot of pro/con lists written by people who have never had one on their roof. After this outage, I can give you a more grounded answer.
- More sensors and controls than a simple furnace. A failed suction pressure transducer can shut down an entire unit. A gas furnace has fewer smart components to fail.
- Repairs are not always cheap or quick. The part itself wasn't outrageous, but overnight shipping and the service call made it a costly outage.
- Performance depends on the installer and the water loop design. If the loop isn't sized right, you'll chase problems.
- Cold climate outdoor units are better than they used to be, but they still lose efficiency in extreme cold. Our system is water-source, so that specific issue isn't in my building, but it's still a real concern for anyone with an air-source heat pump in a cold region.
The biggest disadvantage I saw was serviceability. A furnace or boiler is mechanically simpler. With a heat pump, you have refrigerant circuits, reversing valves, expansion valves, transducers, controllers, and electric backup heat. More components means more things to diagnose when something goes wrong.
To be fair, a failed sensor isn't a sign that the brand is bad. AAON units are usually reliable. But they are still machines. The disadvantage is that they have more smart components than a simple furnace, and each one can become a failure point.
Another disadvantage is cost transparency. The part itself wasn't outrageous—I think it was around $300, maybe $350, I'd have to check the invoice. But overnight freight and the service call made it a four-figure repair for a small sensor. If I had kept a spare transducer on the shelf, the repair would have been an hour or two instead of two days.
I'll also be honest about cold climates. Our system is water-source, so the outside air temperature doesn't affect the loop as much. But if you're shopping for an air-source heat pump for a house in Minnesota, the cold-climate question is real. Modern cold-climate models work down to negative temperatures, but efficiency drops. If you ask what are the disadvantages of a heat pump, that's one of them. It's not a deal-breaker, but it's a trade-off.
I'm not saying you should avoid heat pumps. I'd recommend one for a commercial building with a good mechanical contractor. If you're a homeowner in a cold region with no local heat pump specialist, the honest answer might be different. There is no best system, only the best fit for your building and your market.
What I'd Do Differently
I still kick myself for not creating a spare parts list earlier. During our 2024 vendor consolidation project, I promised operations that I would identify critical spare parts. I didn't follow through. This outage was the consequence.
Since then, I have a one-page cheat sheet with the model number of every heat pump, the phone number for the distributor that stocked the transducer, and a short list of sensors worth keeping on the shelf. I should add that I haven't actually bought spare transducers yet. That's still on my list. (Note to self: call the distributor before next winter.)
I'd also ask about overnight freight on the first call. The second distributor volunteered the price. The first one didn't. If I'd asked a better question, we might have saved a day.
One more thing: I should have asked the technician whether the transducer was a common failure item. He said it was one of the more common sensor failures on these units. If I had asked that in 2024, we would have had a spare before February 2025.
This was accurate as of February 2025, and HVAC distributor stock changes fast. Prices shift, too. If you're budgeting, call your local distributor and verify current availability before you assume a part is in stock.
The Bottom Line
AAON makes solid equipment, but no brand I've worked with is free from sensor failures. The real difference is how quickly you can get the right part. That was the lesson. And if someone in my building ever asks to bring the propane heater indoors again, the answer is still no. It is an outdoor heater. It stays outside.
