A scroll compressor compresses between two interleaved spirals, a rotary one with an eccentric roller inside a cylinder. No regulation, no standard and no declared dataset compares those two kinematics against each other: Regulation (EU) 813/2013 sets its requirements on the complete appliance, with a seasonal space heating energy efficiency of at least 110% for medium and high temperature units and 125% for low temperature units since 26 September 2017. The technology-level COP gaps found online rest on no primary source. What can be compared, recorded and defended is the declared efficiency figure, the sound power level, and the refrigerant charge.
What the compressor does, and what it does not decide
Its role in the cycle, in one line useful on survey
The compressor draws refrigerant in at low pressure and discharges it at high pressure, which raises its saturation temperature and lets it release heat at the condenser. On a variable speed machine, it sets the refrigerant mass flow and therefore the instantaneous output. On a technical survey, what you record is not the compressor technology, it is the stated modulation range, the output available at the site design temperature, and the declared sound power level.
Scroll and rotary: what the design actually changes
The scroll compresses continuously over several turns of spiral, with a fairly steady resisting torque. The rotary compresses over one turn, with more concentrated forces and a different vibration signature. That translates into industrial fitting choices: rotary dominates small outputs and compact units, scroll dominates mid and higher outputs. That market observation is not declared performance, and it does not belong on a quote as a numeric argument.
Why seasonal efficiency is the only defensible benchmark
The seasonal space heating energy efficiency under Regulation (EU) 813/2013 is measured on the complete appliance, under defined conditions, and declared by the manufacturer. It is the only value you can put to a client, an inspector or a competitor. Read it with its category, low temperature or medium and high temperature, because the thresholds differ. On reading declared performance, see COP at part load.
The refrigerant charge, which is what really decides your obligations
The 5 tonne CO2 equivalent threshold, converted into kilos
A leak check is not triggered by a compressor type or an output rating, but by a charge expressed in tonnes of CO2 equivalent. The conversion is one multiplication: charge in kg times the refrigerant GWP, divided by 1,000. GWP values come from Annex I of EU Regulation 2024/573, on the fourth IPCC assessment report, and blend values are worked out through the Annex VI method.
| Refrigerant | GWP used | Charge reaching 5 t CO2e | Charge reaching 50 t CO2e |
|---|---|---|---|
| R32 | 675 (Annex I) | 7.41 kg | 74.1 kg |
| R410A | 2,088 (calculated, Annex VI) | 2.39 kg | 23.9 kg |
| R407C | 1,774 (calculated, Annex VI) | 2.82 kg | 28.2 kg |
| R134a | 1,430 (Annex I) | 3.50 kg | 35.0 kg |
| R290, R744 | outside the annexes | not applicable | not applicable |
On a residential heat pump holding 1 to 2 kg, none of those thresholds is reached. The exemption is even explicit for hermetically sealed equipment labelled as such holding less than 3 kg in a residential building. On calculating and logging the charge, see refrigerant charge.
What a compressor replacement triggers
Article R543-79 of the French environment code requires a leak check at commissioning above the thresholds, then on every modification affecting the circuit that holds the refrigerant. A compressor replacement is one. Below the thresholds the duty falls away, but the intervention record remains the document that proves what you did. That is what gets produced in a dispute, not the compressor brand.
The failure causes you control, whatever the technology
- Insufficient water flow or an undersized circulator, pushing the machine outside its envelope.
- Short cycling from oversizing or too little water volume, multiplying the number of starts.
- A rushed vacuum pull-down or brazing without a nitrogen purge, leaving moisture and oxides in the circuit.
- An approximate charge, causing liquid return or oil starvation depending on which way the error runs.
Noise, the one comfort criterion that is actually enforceable
What Article R1336-7 of the public health code sets
Overall emergence is the gap between ambient noise with the machine running and residual noise without it. The limits are 5 dB(A) in the daytime period, 07:00 to 22:00, and 3 dB(A) at night, 22:00 to 07:00. Those values carry correction terms based on the cumulative duration of the noise.
| Cumulative duration | Correction term |
|---|---|
| T ≤ 1 min | + 6 dB(A) |
| 1 min < T ≤ 5 min | + 5 dB(A) |
| 5 min < T ≤ 20 min | + 4 dB(A) |
| 20 min < T ≤ 2 h | + 3 dB(A) |
| 2 h < T ≤ 4 h | + 2 dB(A) |
| 4 h < T ≤ 8 h | + 1 dB(A) |
| T > 8 h | 0 |
Article R1336-8 disapplies the limits where measured ambient noise, machine included, stays below 30 dB(A). A short defrost is therefore judged more harshly than steady part-load running: that is what you explain to the neighbours, not compressor kinematics.
What gets designed out at siting rather than paid for later
Perceived noise comes from the fan, the defrost cycle and vibration transmitted into the support before it comes from the compressor. Decouple with anti-vibration mounts, prefer a ground frame to a wall bracket, keep clear of re-entrant corners that reverberate, and check the distance to neighbouring openings. On method and on after-the-fact corrections, see heat pump noise and vibration.
What you measure before leaving site
Record the level at the boundary with the machine off, then running, at steady state and during a defrost, and note the time. Two dated readings beat a declaration of compliance. They are your baseline if a complaint lands a season later, once the acoustic environment has changed for reasons that have nothing to do with you.
What goes on the quote and what carries your liability
The technical wording that makes a quote defensible
State the exact reference, the output at the site design temperature, the declared efficiency with its temperature category, the refrigerant and the charge in kg. Those values come from the manufacturer, and a catalogue where the technical characteristics are already verified saves re-entering them on every quotation. Compressor technology can appear as a characteristic, never as a performance promise: a performance claim with no standardised data behind it is a commitment you will not hold in front of an expert.
Compressor warranties: what voids them
Ask in writing what the compressor warranty covers, part only or part, labour and travel, and above all the conditions for keeping it. Non-compliant commissioning and the absence of a logged service history are the two commonest exclusions. On duties and check points, see heat pump servicing.
Justifying your price against a cheaper bid
The extra cost of a job done properly sits in the sizing, the acoustic decoupling and the buffer volume, not in the compressor. A competitor lining up an oversized machine is selling short cycles and starts that will wear the component out, whatever its technology. On the mistakes that recur most, see the five sizing mistakes.
