I purchased a new water softener for the house. It has a digital flow metering device. It worked great for a few days and then stopped working. Long story short, I finally figured out that the outlet I plugged it into was for 240V instead of 120V (bought the house about a year ago so the previous owner obviously didn’t know what he was doing). The power supply for the water softener has a 120V to 24v stepdown transformer to power the digital meter. I’m assuming the water softener was getting 48V for a few days until either the transformer or digital meter gave out. I’ve corrected the electrical problem so now it’s time to get the water softener working again. Will replacing the transformer be enough or should I just order a new digital meter? $30 vs $300 so I’m hoping for the best case scenario.
It's impossible to say. It really depends on how the meter's internal power supply works.
Being electronic, obviously it runs on DC and not 24VAC. They're just using that voltage because it's extremely common in North American homes, being used as control voltage for the furnace and there's usually an existing 24V transformer somewhere in the house. Those transformers are cheap and common, by the way; I'm surprised you have to wait for one. Any HVAC supply will have them, maybe even a hardware store or big-box.
So it must have an internal power supply. If it's a switching power supplY, they open and close (switch) a gate, and on higher voltage they simply close the gate sooner. (That is how many consumer electronics can auto-range from 90-264VAC). So you can run switching supplies beyond max spec if their insulation is in good enough shape to handle the higher voltage. Insulation is cheap to add to most components (not electrolytic capacitors), so you have a fair chance. If it's fried and you want to attempt component repair, start with the big caps.
None of this will fix anything else that was plugged into that 240V receptacle.
Putting 240V on a NEMA 5 120V receptacle is simply outrageous. And needless - they make receptacles for that. They look exactly like standard receptacles except they are keyed differently. Every big box store and hardware store sells the receptacles and plugs.
Now if you found a NEMA 6 receptacle and altered your transformer to fit, that's on you. But if the previous homeowner fit a NEMA 5 receptacle because he was too lazy and cheap to get the correct NEMA 6 at the hardware store, and his logic was "well I know it's wired 240V", then he should have disclosed that in his disclosures, and he would've been written up for it and had to fix it, presumably by installing a NEMA 6. If he did not do any of that, then he is liable for all your damages here. I would go after him for it. Not least, he sorely needs an education, because you bet he did it again to save $5.
This could have caused a house fire.
Really sorry that you were exposed to an improperly wired outlet and had to discovered it this way. If you have already not done so you should take a meter and measure the other outlets in your house that the previous owner may have messed around with.
You could measure the transformer output when it is plugged into the proper 120VAC outlet. If it reads out ~24VAC then the transformer is probably OK. I would expect that the maximum voltage ratings of the transformer were above those that it was exposed to in the improper operating scenario. So it should be OK unless you noticed that it got extremely hot for those few days in which case I would recommend replacing it.
The digital metering unit on the other hand has likely not had a good outcome from being exposed to the 48V for an extended period of time. It is not possible to know, without reviewing a schematic for the metering unit, if the unit was designed to work properly with a wide range of input voltage or not. Certain designs could have exposed much of the circuitry to voltages well beyond what it can survive. On the other hand there could have just been a small portion of the circuitry that was exposed and failed but left the rest OK. In this latter case an experienced electronics technician could possibly repair the unit by replacing just a few components. You would have to weigh possible repair costs against the cost of a new unit.
The transformer will, to some extent, limit the voltage at the output, likely to more like 36V than 48V due to saturation. Your meter may or may not have survived intact. If nothing appears to be burned (use your nose) it may well be okay.
Most well-designed products will have no trouble with a momentary transient but they may not be able to withstand continuous abuse.
I suggest you to get a 'switching' power supply capable of bearing 110 to 250V (similar to pc power supply) so you just don't have to bother where you connect it. 'Standard' power supply, that are essentially transformers, only get 'proportional' reduction ratio (so a 220V to 24V used on 110V circuit will make 12V and vice versa). Anyway, in your case, it's possible you have destroyed your softener (instead of your transformer).