Something I don't understand is how come can it cost so much to relace an old Amiga to control AC? What about a regular PC with some smart software? Is this the cost of other hardware that is so expensive?
It reads like the current system is probably using AX.25 wireless packet radio to communicate with the other schools. I suspect this type of use case with amateur radio is, at best, a grey area in terms of regulatory compliance. The replacement still shouldn't cost as much, but I'll bet it's more than just replacing the PC. It's also coming up with some kind of cross-school network, if one doesn't already exist. And compliance with the inevitable mountain of government requirements.
Another comment mentioned this already, but a single low end PLC for the central control unit (such as https://www.automationdirect.com/adc/overview/catalog/progra... ) plus RDCs at each building would cost under $5000 easily, all while being in compliance with any standards governing such equipment.
I like Amiga, but you could probably do whatever that machine is doing with some Arduino-class hardware these days. I don't think the challenges are technical in nature.
Edit: And as the comment thread in the article explains they're probably renovating the whole HVAC system, not just replacing that single Amiga.
It doesn't. The same type of solution could be provided today with a low cost PC/embedded system with a trivial amount of specialized hardware. The cost for a modern version of what they had (solving any major issues the old system had) would be a fraction of the cost and time the original took. But no business owner in their right mind wants to be stuck selling that: low margin, virtually no growth. What they replaced it with is something completely different than what they had.
There are only a few vendors and if you get it wrong the school can end up with a $3000 bill for power over the usual charges. The actual programming and hardware is incredibly simple.
Probably because it's a public school, so it has to go through a tender process with an absurd number of requirements and paperwork. That'll 10x the cost because of the extra paperwork.