Ah, homeownership. That magical journey where you spend thousands on things that make no visual difference to your home, just to avoid slowly freezing or melting to death. Welcome to the glamorous world of heat pumps—specifically, the LG Therma V, a device I now know far too much about.

Let’s rewind to the commissioning day. Picture it: a brisk morning, coffee in hand, and the “official LG partner” arrives to wave his magic wand over my shiny new heat pump. He assures me everything is set up just right. I nod politely, knowing full well my system is oversized. Like, comically oversized. We’re talking heat-pumping-the-Sahara oversized.

But hey, it was all “fine.” You know, like when your car is making a weird noise but your mechanic says, “It’s probably nothing.”

Spoiler: It was not fine.

Short Cycling: The HVAC Equivalent of a Nervous Breakdown#

What followed was a delightful phenomenon known as short cycling. For the uninitiated, this is when your system turns on and off so frequently, you’d think it was trying to set a new Olympic record in HVAC sprints.

It’s kind of like revving your car from 0 to 100 km/h every few minutes and then slamming on the brakes—except instead of winning a race, you just get terrible efficiency, uneven heating, and a compressor that’s aging faster than a banana in the sun.

My beautiful, overpriced heat pump was essentially panicking every 30 minutes.

“HEAT EVERYTHING! Oh wait… never mind. No! Wait! HEAT EVERYTHING AGAIN!”

Enter: The €30 Hero#

Instead of calling back the installer (and risking hearing the phrase “that’s just how it works” again), I took matters into my own hands. Armed with my trusty €30 Modbus tool—basically the digital equivalent of a stethoscope for your heat pump—I started poking around the settings like a nosy neighbor on HOA day.

First realization? The control was set to room temperature. Which is cute if you have radiators and like dramatic temperature swings. But I have underfloor heating, which is slow and steady—basically the tortoise of heating systems.

So I switched it to outlet temperature control. Why? Because underfloor heating needs stability, not drama. Outlet temperature is smoother, less prone to wild swings, and makes the system behave like a responsible adult instead of a caffeine-addled intern.

The Setting That Changed Everything#

Then came the pièce de résistance: the TH On/Off setting. The Therma V comes with four options:

  • Type 0 – The default.
  • Type 1 – For radiators. Slightly less sad.
  • Type 2 – Chef’s kiss for underfloor heating. Long cycles, minimal drama.
  • Type 3 – Hyperactive mode. Immediate response, but burns energy like a toddler burns through snacks.

Naturally, mine was on Type 0. Because of course it was.

I switched it to Type 2, and like magic, the frantic compressor calmed down. It went from “I MUST HEAT NOW!!!” to “Yeah, we’ll get there. Let’s vibe.” Modulation kicked in properly, and now it runs like a Zen monk with a thermostat.

The Before and After: Now with Graphs!#

Before the change, my compressor graph looked like a seismograph during an earthquake. Spikes every 30 minutes, up and down like a stock market crash.

After the change? Smooth, steady lines. No more panic attacks. No more energy waste. Just warm floors and a compressor that won’t die of exhaustion before its 5th birthday.

compressor

power usage

Moral of the Story#

Just because something is installed by a “certified partner” doesn’t mean it’s optimized. Manufacturers set defaults for average installations. But your home isn’t average. It’s a unique snowflake of poorly documented quirks and insulation sins.

A €30 gadget and a little research saved me from years of inefficiency and probably a multi-thousand-euro maintenance bill. All because I dared to question the sacred default settings.

So if you have an LG Therma V—or any smart HVAC system—and it’s short cycling like a hyperactive toddler, don’t wait. Get curious. Get nerdy. Get a Modbus.

And remember: when in doubt, never trust “default.”