Chapter 4 — Forty Years Later: what has changed, what remains

Forty years on: what has changed, what remains

Forty years later, the industry has evolved profoundly. Modern heat pumps bear little resemblance to the PERCHE systems of the early 1980s: Inverter compressors, next-generation refrigerants, real-time electronic controls, COP¹ values above 4 in real winter conditions. The technology has delivered on its promises — with a four-decade delay on Suominen’s intuitions.

Yet several of the principles he championed — quality of installation, optimisation of heat exchange, matching output to real demand, achieving a high COP in cold conditions — are now recognised as basic requirements that any serious installer must master. Not as historical curiosities, but as indispensable technical foundations.

What forty years have brought

The Inverter compressor: the quiet revolution

This is arguably the most decisive development. The two-speed compressor that Suominen recommended — already a break from the on/off approach of the time — has been superseded by the Inverter compressor, whose speed is continuously variable thanks to an electronic drive.

The result is spectacular: the machine continuously adapts its output to the building’s actual needs, without unnecessary start-stop cycles. The COP is maximised at every instant, mechanical wear is reduced, and thermal comfort is incomparably superior to that of the first installations.

Refrigerants: forty years of chemistry

The R22 that dominated in the 1980s was progressively banned due to its impact on the ozone layer. Its successors — R410A, R32, and today R290 (propane) — offer better thermodynamic properties at low temperatures, a reduced environmental impact, and for some (R290) a flammability that imposes new installation safety constraints.

Controls: from electromechanics to microcontrollers

The mechanical thermostats and pressure switches of the PERCHE era have given way to fully digital control systems: weather compensation curves calculated in real time, communication between indoor and outdoor units, embedded diagnostics, home automation connectivity. What Suominen described as adapted control is today intelligent control.

Installation: the weak link that remains

This is perhaps the area where progress has been least spectacular. An excellent machine that is poorly installed remains a machine that underperforms — approximate sizing, poorly balanced hydraulic circuits, badly chosen location for the outdoor unit. Feedback from serious installers confirms it: installation quality remains the primary factor in real-world performance, exactly as Suominen emphasised in 1983.

What Lenoir understood before the others

The true lesson of this article is not that the heat pump was a bad idea. It is that a promising technology can be durably discredited when it is industrialised too quickly, without sufficient mastery of its design, installation, and commissioning.

This observation, made by Yves Lenoir in 1983, remains strikingly relevant today — at a time when other energy technologies are being deployed massively and hastily. The temptation to sacrifice quality for speed is a constant in industrial history; the heat pumps of the 1980s paid the price for fifteen years.

Purpose of this project

This project does not aim to demonstrate that the solutions described in 1983 constitute a model to be reproduced as-is. It seeks above all to preserve a remarkable technical testimony, and to place in context the debates that accompanied the early days of heat pumps in France.

The reader is invited to compare these analyses with current knowledge and technologies — and perhaps to find in them some lessons that go well beyond the realm of thermodynamics.

The following chapters are aimed more specifically at readers who wish to go further: understanding the internal workings of a modern heat pump, identifying common failure points, and approaching the diagnosis of a faulty installation with confidence.