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Comment by londons_explore | Hacker News Reader

Whats wrong with R600a (isobutane)?

It can provide heating/cooling suitable for nearly all usecases in homes, offices and retail (ie. -100C up to +150C).

It isn't awful for the environment if vented (no ozone depletion, greenhouse effect less bad than driving your car a few miles if you vent a fridge/freezer).

Yes, it is flammable... But in typical quantities in a fridge (perhaps 60 grams), it's hard to do too much damage.

It is also cheap, easy to lubricate, unpatented, made by many suppliers and efficient.

I really don't understand why anyone would want to use anything else....

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For better or for worse, people like to pump refrigerant through pipes in buildings, and flammability can be a problem. Also this requires a lot of refrigerant.

One can separate the refrigeration part and the moving-heat-around part, though, by using good old H2O in pipes. Water is non-flammable, non-ozone-depleting, cheap, and has zero GWP. It can be a bit messy if a large amount spills indoors, though.

Flammable refrigerants are no joke:

https://www.youtube.com/watch?v=A169-s4KHFQ

Several light hydrocarbons seem like perfectly good alternatives. Propane is another one. And there's also quite a lot of use of ammonia for refrigeration as well. It's not clear to me why these simpler, non-chlorinated, non-fluorinated compounds are so grossly undesirable that we keep chasing more-complex alternatives.

Is it really that people are simply horribly afraid of their flammability?

Ammonia is quite toxic. Some bad outcomes from leaky ammonia air conditioning in the past. Ok for industrial chillers with good leak detection systems.

Texas state code requires machine rooms for ammonia systems to get 30 air exchanges per hour, same state building code requires houses to be under 1/3 air exchanges per hour.

I'm a little fuzzy about the later, pretty sure about the former, and most people don't have the privilege of living in Texas (not sure if I'm kidding or not?), but it demonstrates the safety issue that ammonia cooling needs about a hundred times as much ventilation as a normal kitchen. And insert the usual quotes about building codes being written in blood so they aren't demanding a hundred times the ventilation just for fun.

People are scared of the sealed container explosion.

An external butane leak would be about as harmful as a leaking cig lighter.

Internal leak? A perfect mixture of butane and air the size of fridge would certainly take out a wall, maybe an entire house if it knocks out a load bearing wall.

The worst part about the internal explosion is its almost certain to happen when the owner is standing right in front and opens the door and the light kicks on along with maybe anti-frost heaters or whatever else is in there.

I have seen some ideas proposed such as using the "smart" in a smart fridge for good not evil and locking the door if the system pressure drops below "X". Much more likely the "smart" in a smart fridge will never be permitted to be used for anything other than advertising and marketing, which is sad.

Energy content of hydrocarbons is about the same (to one sig fig or less LOL) and just one gram of gasoline can blow a piston rod clean thru an engine block under perfectly bad conditions (already shattered bearings, etc) so a couple hundred grams under worst possible case in a confined sealed fridge could take out a house, most likely.

(Edited to add: I have a better analogy: A perfect stochiometric mix of air and diesel the size of my coffee cup can blow the engine head clean off a diesel engine, IIRC that's how one of the brothers who invented the Diesel engine died in a lab accident a century ago. And that was just a little coffee cup sized engine cylinder. So imagine a sealed container the size of a fridge instead of a coffee cup... that'll take out a house for sure... neighbors will "probably" live but I wouldn't bet on it...)

I had an internal explosion of my gas grill. I apparently forgot to turn the gas off so it filled the chambers under the grill plates and when I went to light it, it sent the top and the grill plates through the lanai and 40ft into the air. I lost my eyebrows for a few months.

locking might not even be necessary, just power off the device if pressure of refrigerant drop.

Having some way to ventilate the gas (so you don't just get "a box full of flammable gas" situation on slow leak) without reducing performance too much might help also

I get your point, but we already have methane pumped to our houses. Are these worse?

Yes, sealed container vs open air. If we stored natgas in scuba tanks that could get exciting... ironically there are people considering powering auto engines with compressed natgas... must be very exciting in a fire LOL.

Yet we plumb methane in houses all the time. Also, at least for HVAC, it's perfectly reasonable to keep all of the refrigerant outdoors and use water as a heat transfer medium to the interior.

And it’s not a great idea, especially given the proliferation of appliances that burn it in room air.

And methane has the convenience property of being less dense than air. I’m not sure, but I expect that the heavier hydrocarbon gasses might be more likely to accumulate indoors.

A3 refrigerants (hydrocarbons) have very low charge quantity limits that basically make them infeasible systems with even modest capacities. Split type air conditioners or heat pumps predominately used in the US have several times the allowable limit of charge in the liquid line alone.

Building codes have only recently (and incompletely) been revised to allow mildly flammable refrigerants (A2L) inside most buildings for space conditioning. Amending these for A3 refrigerants is an uphill battle.

Ammonia is mildly flammable, toxic, and electrically conductive. Good luck finding/building a hermetically sealed compressor that is anywhere near affordable.

CO2 in a refrigeration cycle goes transcritical at even moderately warm temperatures, making the system very inefficient without adding several (typically expensive) changes to the cycle. Manufacturers would struggle to build a CO2 air conditioner that meets minimum efficiency standards at anywhere near current equipment costs.

I'm not an expert in refrigerant selection but you've missed many critical aspects of a refrigerant: we care about viscosity, density, thermal conductivity, etc. because these all impact the energy efficiency of the system.

Every flammable refrigerant I've seen is usually in a completely sealed system. There is no way to maintain them unless you completely vent the system and add ports yourself, manufacturers don't seem to want the liability and many governments force the issue by code anyways.

You typically need to completely vent the system for any maintenance on a refrigeration system anyway, if only for the fact it is important to weigh the amount of refrigerant (too much and you could get slugging, which is very expensive to fix).

I think lack of ports is simply to save money - in the factory it's just as easy to fill once and crimp the system closed.

> You typically need to completely vent the system for any maintenance on a refrigeration system anyway

On residential/small systems where it's commonly used today, sure. For larger systems this is not true. You're typically going to have a receiver and a valve you can use to store the charge entirely in the receiver. Then you can work on the system without having to dump or capture that charge.

It also allows you to have additional cooling circuits, so you're starting to see this incorporated into smaller commercial designs for the additional cooling efficiency.

> I think lack of ports is simply to save money

They're required to be hermetically sealed in the US by IEC and in most Pacific Island countries by law where they're more commonly used in residential applications.

Save money, and force consumers to buy a new one when it breaks

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