Scantec: ‘Adopt low-charge NH3 to comply with HFC phasedown’

Scantec’s Stefan Jensen was in Sydney this week to make the case for low-charge, centralised DX ammonia systems as a means of complying with the global HFC phasedown.

Stefan Jensen presenting at ATMOsphere Australia 2018 in Sydney.

At ATMOsphere Australia and ARBS 2018 this week, Stefan Jensen – managing director of Scantec Refrigeration Technologies – made the case for low-charge, centralised ammonia DX systems as a means of complying with the HFC phasedown, cited system simplicity, energy performance and the minimisation of risk to occupants among their benefits.

“People who make the buying decisions generally look at their electricity bill first and foremost,” Jensen told the ATMOsphere Australia conference at Sydney’s Luna Park on 7 May.

He presented field data indicating that switching from conventional liquid overfeed NH3 to low-charge centralised DX NH3 results in Specific Energy Consumption (SEC) reductions of 18-38% depending on plant layout. “This is a result of the removal of liquid from wet return lines and risers,” he said (for more details, see his presentation on

Dual-stage central plants with distributed condensing reduce electricity bills compared to conventional liquid overfeed plants, said Jensen, citing specific NH3 inventories of 0.2-0.4 kg NH3/kW.

“The numbers speak for themselves. We now have 14 systems running in Australia, with five more under construction,” Jensen said. Of these 14 plants constructed since 2013, none have required compressor overhauls to date. No issues regarding moisture accumulation in the refrigerant have been reported thus far either.

He argued that capital costs of the new system build are approximately the same as conventional liquid overfeed NH3.

Once you go ammonia, you’ll never go back!
– Stefen Jensen, Scantec

Jensen told ARBS 2018 in a 10 May seminar that there are three fundamental types of low-charge ammonia systems – packages for chilling of liquid (down to approx. 0.03 kg NH3/kW), unitary equipment (0.018 kg NH3/kW), and larger central plants (0.65 kg NH3/kW).

Among the specifics of the design he presented at ARBS 2018:

  • Reciprocating compressors with VFDs for superior part-load performance and turn-down ratio.
  • VFDs on all evaporators and condenser fans.
  • Special evaporator circuiting, materials and distribution.
  • Dry expansion controlled by combination of superheat and refrigerant quality at evaporator exits.
  • No heavy liquid in the suction lines.

In these plants there are no ammonia pumps. The low and medium-temperature evaporators are fed by common high-pressure liquid line. The hot-gas defrost condensate returns by means of a high-pressure float valve to minimise the gas bypass.

The configuration also allows for adding short secondary refrigerant loops by employing low-charge DX/ NH3 glycol heat exchangers.

“The system is readily expandable,” Jensen told the ARBS 2018 audience. “You can extend vapour lines to new locations on the roof for new evaporators or glycol pipes for glycol-cooled condensing as the plant grows.”

Among likely future market trends, he cited smaller tubes that suit lower ammonia inventories, 304SS piping for low friction, high-corrosion resistance, and low-leakage probability.

“Once you go ammonia, you’ll never go back!” Jensen said.

The Air Conditioning, Refrigeration and Building Services Exhibition is taking place at the ICC in Sydney's Darling Harbour from 8-10 May.

By Andrew Williams

May 10, 2018, 02:00

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