75-250 is indeed a pretty large range. But not too unusual to do that. According to https://www.ysi.com/water-hardness that would be somewhere between soft and slightly hard (no particular endorsement; this was just the first site that I found online). I don't think you'd go horribly wrong by telling your oven to treat this as "medium". Worst case, it prompts you to descale the unit more frequently than strictly necessary. That'll waste a little money on supplies. But if in doubt, that's better than wasting money on repairs. I recommend you buy the descaling tabs in bulk. They regularly show up on Amazon and other online services. And they definitely get cheaper if you buy a bigger package. You'll need two per descale cycle. I usually need to do so every six to nine months. But that might not be the same for you. We use the steam oven very frequently, but we have very soft water. Also, you absolutely want to make sure you have tabs on hand, when the unit needs it. You don't want to find yourself in a situation where you can't use the oven for a few days while waiting for supplies.

This is not to convince you to buy a sous vide cooker, but will give you a reference perspective point regarding temperature and cooking time with short ribs: (copied from the WEB for cooking short ribs at 145F for 72 hours) "Collagen determines, to a large extent, whether cooked meat ends up tender or tough. It is also the determining factor in how long you should cook a given cut of meat. Collagen fibers are the biological equivalent of steel cabling, forming a mesh that holds bundles of meat fibers together. Proper cooking unravels the cable-like structure of collagen fibers and dissolves them into juices, transforming the tough collagen into tender gelatin. In order to unravel collagen fibers, you must heat them. Heat causes the fibers to shrink, and the contracting mesh squeezes juices out of the meat. The hotter the cooking temperature, the more collagen mesh contracts, and the more juices are lost. If you cook the meat at lower temperatures, fewer of the collagen fibers shorten at any given point in the cooking process, so the mesh constricts the meat less. This is why meats retain more of their juices when cooked sous vide. But at lower temperatures, more time is needed to shrink, unravel, and dissolve enough of the collagen fibers to make the meat pleasantly tender." I generally SV cook at 150F for 48 hours. Short ribs is expensive, given the fact that it is mostly bones and fat, here is a suggestion for you for fun: 1. pressure cook short ribs in a separate container with no seasoning and no water for about an hour. You will get a good amount of the most concentrated beef broth(juice) ever for many recipes. 2. Remove the meat from the bones, and use the bones later for more beef broth the regular pressure cooker way. 3. Now with the meat, which has most of the fat rendered already, and find recipes for boneless short ribs and cook until tender. dcarch

Basically - brown the meat, add liquid and extras, cook at low heat for a long time to break down connective tissue and convert to gelatin, then do something with the liquid. Sometimes you marinate the meat first for flavour, or coat in flour to thicken the sauce later, I often don't bother with either. The liquid is usually wine or beer or stock, being tastier than water. Extras are usually aromatics (mirepoix etc), herbs/spices, tomato paste, anchovy paste, lardons/bacon, etc. You can use stock-making tricks like adding a gelatin source (powdered gelatin or a piece of animal with lots of collagen - knuckles, feet, etc) or adding bones - these are discarded at the end. It is hard to mess up. I'm sure you'll get lots of recipes. Here is a slightly Asian version that is very simple and tasty. In fact I made short ribs in this manner a couple weeks ago, yummy. - start with 3-4 lbs of short ribs, do not trim fat - use large sauce pot or dutch oven with tight-fitting lid - brown ribs over high heat in a little vegetable oil, working in batches - chop a few slices of gingerroot and a few cloves of garlic, cut a bunch of green onions into 2" lengths (ginger and garlic are optional, can use regular onions) - place ribs, ginger, garlic, green onions in pot - add about 3 oz of soy sauce and a little bit of red pepper (if don't like heat, then black pepper) - add about 6 oz of rice wine (if none, could use sake or white wine or red wine, the wine version will taste different) - add enough water or beef stock to cover ribs (you want at least 10 oz of liquid in total) - bring to boil, then cover pot and reduce heat to simmer or place covered pot in 350F oven - cook for 4 hours, stir once or twice - remove ribs, the meat should be almost falling off the bone, and set aside in a warm place - discard all remaining solids (ginger, green onions, etc) - defat liquid if needed (probably won't be) - place pot on burner, uncovered, bring liquid to full boil, and boil until reduced by 1/3 to 1/2 (you want to end up with an adequate amount of sauce, which is why you started with at least 10 oz liquid) - heat to medium, return ribs to pot to reheat and coat in sauce - faster alternative to 4 hours slow cooking: pressure cooker at high pressure for 1 hour

Another parent of an 8 years old; and a 6 years old. Please note that there is a difference between steam assist and a true combination steam oven (*). One of the the nice things about our Miele CSOs is the fact that you can select between 0% and 100% humidity across the entire temperature range. Steam-assist ovens usually can't do that. Also, our CSO has very precise temperature control at the low end. This makes it possible to be used as a sous-vide cooker. And that opens up a whole lot of other possibilities. You can slow cook first and then in the same appliance roast to finish the dish. Also, temperature and humidity control is great when baking bread. The short preheat times are great too. Bigger ovens frequently take a lot longer to change temperature. For some dishes that's ok; for others, it's a nuisance and requires careful meal planning. @dorianday, no way would I let you sit and watch. I'll find a task for you. Do you like peeling potatoes, or do you want to pit a half gallon of olives? *) Edit: It does look as if Thermador makes a real combination steam oven and not just a steam-assist oven. But the manual (like most of these manufacturers) is woefully inadequate. I can't quite tell in which modes I can enable steam and what temperature and humidity ranges I am restricted too. Also, I can't tell whether temperature control is sufficiently precise to allow sous-vide cooking. That only works, if temperature swings are really minimal. Finally, while Thermador boasts to have the largest oven cavity of any steam oven, I can't quite tell how that compares to Miele. I know that my Miele can, in a pinch, hold a regular half-size cookie sheet. It won't quite fit with the railings, but it's close. According to Thermador's spec sheet, the oven cavity is much too small for an 18x13" half pan. On the other hand, their oven seems taller. Yes, no? Hard to tell. The Miele XXL is also quite tall, but I can't find precise numbers for its size. Arrgh, these manufacturers don't really make it easy.