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(More customer reviews)I have used the Internet extensively for information on tankless water heaters and this 250SX model in particular, so I wanted to fully detail my experiences accurately for others. In short, these things aren't for everyone, it depends on your usage and tolerance, your handyman ability, and the quality of plumbing in your home particularly water pressure. That being said, I am personally very happy with my 250SX set up, but I had to make some adjustments.
Usage: I only use hot water at the kitchen faucet, dishwasher, and clothes washer about once a week. I take a 10 or 15 minute shower every morning. About once a month I fill my 75 gallon jacuzzi. Rarely do I use hot water in the bathroom sinks for other uses, I often wash my hands in cold water. Other than the jacuzzi water and shower, I use very little hot water. Having a hot water tank of 75 gallons, or even 40 gallons, just does not make sense. The 250SX needs 0.8 gallon flow to activate the heating element. I take fairly hot showers and I keep the 250SX at 124 degrees. Because an extra 0.8 gallon flows through the pipes before the 250SX activates, some complain that it takes too long to get hot water, but I think it is no big deal. A bigger problem for some: when you turn off the hot water then turn it on again, your hot water that was in the pipe comes first, then the 0.8 cold water, then it gradually gets hot again. That is a little annoying. Imagine your wife turning the hot water on and off to wash dishes. A hot water tank would just keep the hot water flowing ready for on/off use, but not a tankless unit. It wasn't too big of a deal, but in the end I decided to solve the problem by adding a 6 gallon hot water tank (Ariston GL6+) in series after the 250SX. The 250SX has 3/4 inch NPT water threads, to keep the pressure constant make sure you get a small holding tank that also has 3/4 inch NPT water threads. The hot water always flows through the hot water tank last and the outward source recieves hot water from the small holding tank first. Also, the 0.8 gallon of cold water flows into the small tank first where it is mixed with 6 gallons tanked hot water. Set the small tank at about 4 degrees higher than the 250SX and you won't even know the difference in temperature; problem solved.One guy told me that his wife insists that the hot water must be 140 degrees in the dishwasher, but she also likes luke-warm showers. The problem here is that the 250SX does not get the 0.8 gallon of flow when she is in the shower. Add the fact that she messes with the shower's water controls and the unit goes from on (hot) to off (cold) while she is in the shower. Apparently, that really pisses her off. The small holding tank helps with this too, but there are several ways to solve this problem: 1) get a new wife, 2) use Bosch's remote temperature control (about $120 extra) at the shower to turn down the temperature, 3) turn on a bathroom faucet while she showers (wasting a lot of hot water) 4) my new dishwasher (this recently went out too) has an option to superheat the water it uses (it must have a separate water heater). Some people complain that the unit causes less hot water pressure, but that is not my experience at all. It helps to have good water pressure to begin with (mine is 70 psi) but maybe the hard piping to keep 3/4 of water flowing without bottlenecks helps too. Some people complain that the unit makes a high pitched noise, but that is not my experience either. I will say this: for a short time I had it connected to the previous tanks 1/2 inch gas line. It did make this noise a little when two hot water appliances worked at the same time; probably has to do with needing more gas than available in the 1/2 inch line. In that case, that problem is solved by hard piping a 3/4 inch gas pipe to the 250SX. It seems to me all these problems are related to particular usage or to improper installation; READ THE INSTALLATION MANUAL.
Installation: The venting exhaust must be on its own line, NOT combined with say your furnace exhaust. Also, be sure you incline the exhaut pipe upward if venting horizontally as the manufacturer requires. Incidentally, the model's installation instructions are available on the Internet, READ THE INSTALLATION MANUAL. The 250SX drinks in 175,000 BTU when it is working hard, that might mean you will need to upgrade your gas line. In my case, I was replacing my furnace as well as the water heater. The guy that installed the furnace, used the previous 3/4 inch gas line for the 250 SX, then ran another gas line for the new furnace. Since it was part of the bid, I have no way of knowing the cost, but I would guess the cost at $75 of the furnace bid. To insure that the 250SX gets sufficient gas, the installation manual strongly suggests that the gas line be hard piped to the unit which is what the furnace guy did for me. Another guy told me to hard pipe the water lines to unsure that there are no bottle necks in the water pressure. Apparently, a3/4 inch flex line is actually 5/8 inch in the middle. I sweated the 3/4 inch copper pipe from the cold water source to the 250SX, then to the 6 gallon holding tank, then to the hot water line; all water runs through 3/4 inch copper pipe with unions for quick uninstall if either the 250SX or the holding tank needs to be replaced someday. You will need an outlet for the 250SX pilotless ignition, but I think it takes very little power. If you install the Ariston tank, it requires a 20 amp circuit hardwired to the unit. So, you've got to know a little about electrical, plumbing for copper pipe, and basic handyman skills for everything else. I found it to be a fun little installation project. You can also contract out the installation but it is rather expensive.
Costs: I bought mine at a local hardware store for $899 + tax. The expenses don't stop there, if properly installed this model MUST HAVE a special sealed 3 inch stainless steel pipe for hot gas (carbon monoxide) exhaust, plus a wall thimble and a termination hood. I needed 13.5 feet of exhaust venting (AL29 type) which I bought on the Internet (Cinnabar) for $292. The optional small holding tank (Ariston GL6+) cost me $174 (from Ace hardware on the Internet, have them send it to one of their stores). There is another $150 to $200 in other materials, including a 20 amp circuit plus 12 gauge wire for the small holding tank which needs to be hard wired, copper pipe, etc. The 250SX itself needs an outlet for pilotless ignition. You are supposed to have both on separate curcuits, but I felt this was not necessary, so I put them on the same circuit, outlet and hardwire to the small tank. In total, everything cost me about $1650 with the small tank and installing everything myself. Figure more if you need to increase your gas line as these things suck 175,000 BTUs when loaded, plus $800 to $1500 more if you have someone else install it for you. I got a quote for about $800 for the install not including the small holding tank or the extra for the increased gas line.
Analysis: I figure a quality large water heater, big enough for my Jacuzzi, would be about $800 installed. I will get $300 back in a Federal Tax credit, so the tankless unit setup is $550 in extra expenses that have to be made up in savings ($1650 - $800 -$300 = $550). I figure I save $8 a month in energy costs when I subtract the $2.50 a month to operate the small 6 gallon water tank. It depends on how much hot water you use, others claim they save $20 a month. That means it will take me about 6 years to break even. The warranty is 12 years on the 250SX and 6 years on the GL+6. Keep in mind that tankless units are expected to give twice the service of a water tank. That make sense since most water tanks rust out trying to hold all that water. I have used the 250SX for 2 months now. I'm tickled pink by the unit, but NOT because of my marginal energy savings. With the small tank in series, it acts a lot like the tank I replaced, except the hot water is endless, great for the Jacuzzi,and a lot of room is freed up in my garage. Bottom line: If you 1) have good water pressure (a must), 2) are able to install it yourself, 3) have other reasons besides energy savings to install, then I highly recommend it. If you are lacking on these 3 points then do yourself a favor and just replace your old hot water tank with another.
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Bosch AquaStar Natural Gas Tankless Water Heater #250SX-NG
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