Where did you find that info? It's nowhere on Joule's website.
Is it the heat-up from cold time (15°C to 60°C) or the reheat time after 70% draw off? If it's 'from cold time' then you would need a 72Kw boiler to do the job and a coil to match! If it's after 70% draw off , it will need a 50kW boiler and matching coil.
Someone is exaggerating the performance of their product.
It's in their brochure. Yes, you need a big ol' boiler to achieve the quoted times, but they are capable of that. It's an absolutely enormous coil in there with a 4.0m² surface area - larger than a lot of tank-in-tank heat exchanger sizes.
Yeah, the website is pretty terrible. I can't upload pdf files here it seems - comes up with a security error - but here's a screenshot from the brochure I have saved on my phone...
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