Israeli heat-exchanger manufacturer Lordan Coils has developed a cold-climate propane (R290) residential heat-pump water heater (HPWH), using 5mm (0.2in) MicroGroove copper tubes to achieve a low charge.

The MicroGroove 5mm copper tubes are used to create bent L-shape heat exchanger coils with high heat-transfer coefficients, resulting in higher seasonal energy efficiency ratios (SEER). The small diameter tubes mean less material is needed, giving lower system weight while maintaining the same capacity, according to Yoram Shabtay, President for U.S. consulting firm Heat Transfer Technologies and Peter Mostovoy, Business Development Manager at Lordan.

Shabtay and Jordan described the R290 heat pump during the ATMO America conference, which took place in Alexandria, Virginia, June 7–8. ATMO America was organized by ATMOsphere (publisher of Hydrocarbons 21)

“It’s very clear to see that the output – in terms of watts per volume – you can get much more output by putting it together in 5mm,“ said Mostovoy. 

Anticipating queries about the alternative use of microchannel technology, he added, “It has to drain, it’s getting wet all the time, it’s outside, it’s dirty, the microchannel doesn’t do it, and it’s hard to bend.”

The goal when designing the air-source R290 HPWH was to achieve 20kW of heating or 14kW of cooling (5.7TR heating/4TR cooling), which is enough for a standard house, according to Mostovoy. The smaller diameter tubes mean that the charge for the unit is 0.519kg (1.14lbs), compared to to 1.64kg (3.6lbs) for a similar capacity system with ⅜in (9.5mm) tubes. To those arguing that this charge is still too much, Mostovoy said “don’t forget that this [monoblock] unit sits outside the house, heating a water-glycol mixture, and that mix is what’s going into the house, so the charge is all outside.”

In addition, the reduced need for material means that the weight of the tubes in the tested system goes down from 23.5 to 11.5kg (51.8 to 25.4lbs), when compared to traditional ⅜ in tubes, and as everyone knows “copper prices are going through the roof,” Mostovoy noted. 

“It’s very clear to see that the output – in terms of watts per volume – you can get much more output by putting it together in 5mm,“

Peter Mostovoy, Lordan

Similar to Dutch unit

The R290 HPWH presented by Shabtay and Mostovoy is similar to one Lordan manufactures in the Netherlands, where they have produced 2,500 units in 2022 already. The Dutch model is combined with a gas boiler in a hybrid system. In any temperature above 28°F (-2°C) the heat pump is running. The gas boiler only steps in to assist below that. Dutch law requires natural refrigerants as of 2026, and no boiler can then be installed without a heat pump. 

Talking about how the European Union’s F-gas regulation will soon prevent the use of traditional refrigerants like R134a, Mostovoy mentioned that the demand for R290 heat exchangers and units in Europe is “crazy” at the moment, helped along by Russia cutting off gas supplies to several EU countries as a result of the conflict in Ukraine. 

Questioned about a potential introduction of this technology to the U.S. – considering that the IEC approved an increased charge limit in May for home heat pumps and ACs – Mostovoy explained that for larger units up to 75kW, Lordan would use two or three compressors to address  the existing U.S. charge limit.

“For swimming pool heaters, I don’t know why there’s an issue with charge, it’s sitting way out in the pool room in the back, so I don’t know why anybody is worried about it, I think it’s just legislative; there’s no real reason. If all the gas is outside, I don’t know why there’s an issue with charge.”

Speaking at another session during ATMO America, Christina Starr, Senior Policy Analyst, Climate with the Environmental Investigation Agency (EIA), said, “If U.S. industry stakeholders embrace this new [IEC] Edition 7 and initiate the process for harmonization, we could see residential and light commercial heat pumps and ACs using R290 or other hydrocarbon refrigerants on the market in the next five years. 

“The next step will be forming a CANENA Technical Harmonization Committee (THC) to discuss proposals for adopting these changes into the next edition of the North American safety standards, including UL 60335-2-40. The limit in the US for A3s under UL 2-40 is still 3xLFL, or about 114 grams of propane.”

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