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PLEASE READ THE tERMS AND CONDITIONS CAREFULLY before starting the R32 calculator


The R32 calculator is a practical and user-friendly tool that determines within 4 steps the refrigerant charge limits of MHI air-conditioning and heat pump systems using R32 in indoor spaces.

When mildly flammable refrigerants such as R32 are used within an air-conditioning system, safety checks and proper risk assessment should be performed to minimise any risk of toxicity and flammability.

Depending on the total refrigerant charge of the system, indoor unit(s) must comply with minimum installation floor area requirements.

To do so, Mitsubishi Heavy Industries has decided to follow the standards below:

  • AS/NZS 60335.2.40 2019: Household and similar electrical appliances – Safety Particular requirements for electrical heat pumps, air-conditioners, and dehumidifiers.

This product-family standard covers the safety requirements of Air Conditioners and Heat Pumps (including hot water heat pumps).
In January 2018, IEC 60335-2-40 Edition 6.0 of the standard was published, adding the requirements for refrigerating systems charged with A2L mildly flammable refrigerants.
Annex GG specifies the maximum charge, minimum installation floor area limits, and the relevant appropriate safety measures to comply with flammability requirements.
AS/NZS 60335.2.40:2019 supersedes AS/NZS 60335.2.40:2015 on 28 June 2019. Identical to, and includes the text of, IEC 60335-2-40 Ed.6.

  • AS/NZS 5149.1:2016 Amd 2:2018: Refrigerating systems and heat pumps — Safety and environmental requirements.

This horizontal and generic standard covers a wide range of products including Air Conditioners and Heat Pumps. It consists of 4 parts and in its latest 2016 version, the documents supersede the AS/NZS 1677 series and adopt ISO standards for refrigeration safety. The requirements for refrigerating systems charged with A2L refrigerants were added.
Part 1 – Annex A specifies the maximum charge and minimum installation floor area limits to comply with flammability and toxicity requirements.
It outlines how to calculate the refrigerant charge limit for toxicity-based limits and flammability-based limits.

To reduce confusion and clarify, Mitsubishi Heavy Industries have decided to follow AS/NZS 60335-2-40 2019 for the flammability risk assessment and AS/NZS 5149.1:2016 Amd 2:2018 for the toxicity risk assessment.

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